Hindawi Publishing CorporationJournal of MiningVolume 2013 Article ID 507168 13 pageshttpdxdoiorg1011552013507168
Review ArticleExploitation of Bacterial Activities in Mineral Industry andEnvironmental Preservation An Overview
Ahmed A S Seifelnassr1 and Abdel-Zaher M Abouzeid2
1 Department of Mining Engineering Faculty of Petroleum and Mineral Engineering Suez Canal University Suez 62114 Egypt2 Department of Mining Engineering Faculty of Engineering Cairo University Giza 12613 Egypt
Correspondence should be addressed to Abdel-Zaher M Abouzeid abdelabouzeidgmailcom
Received 14 August 2013 Revised 21 October 2013 Accepted 4 November 2013
Academic Editor Morteza Osanloo
Copyright copy 2013 A A S Seifelnassr and A-Z Abouzeid This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited
Since the identification and characterization of iron and sulfur oxidizing bacteria in the 1940s a rapid progress is being made inminerals engineering based on biological activities Microorganisms can play a beneficial role in all facets of minerals processingfrom mining to waste disposal and management Some of the applications such as biologically assisted leaching of copper sulfideores uranium ores and biooxidation of refractory sulfide gold ores are now established on the scale of commercial processesA variety of other bioleaching opportunities exist for nickel cobalt cadmium and zinc sulfide leaching Recently other usesof microorganisms are potentially possible These include the bioleaching of nonsulfide ores bioflotation and bioflocculationof minerals and bioremediation of toxic chemicals discharged from mineral engineering operations These activities acquireconsiderable opportunities for further research and development in these areas This paper is an attempt to provide a criticalsummary on the most important efforts in the area of bacterial activities in the mineral and mining industry
1 Introduction
Biotechnology has many potential applications in min-ing industry including metal leaching product upgradingremoval of impurities treatment of acid rock drainage andother uses for environmental control Recent interest in thebiotechnological processes is the direct application to treatwastes and low-grade ores [1ndash3] In this aspect bacteriacatalyze the dissolution of metals from minerals Thereforebacterial leaching processes are faster than chemical pro-cesses at ambient temperature and atmospheric pressure Sofar only three different types of commercial scale microbi-ological leaching techniques are practiced for the recoveryof copper and uranium from low-grade ores namely dumpleaching heap leaching and insitu leaching Knowledgeabout bacterial involvement in these processes has beenrelatively recent because the microorganisms responsible forthe solubilization of metals from minerals were identifiedonly a few decades ago Furthermore heap and dumpleaching technologies were introduced in the United Statesby the Phelps-Dodge Corporation at Bisbee Arizona and
Tyron New Mexico in early 1920s [4] although at that timethe processes involved in the leaching and acid drainageproduction were considered to be solely chemical in nature
Lately interest in the biological oxidation of refractorysulfide gold ores has been practiced worldwide [5] Moreovermicroorganisms are used in biobeneficiation which refersto removal of undesirable mineral components from anore The interaction with microorganism selectively removesthe impurities and thereby enriches the desired mineralconstituent in the solid orematrix such as biodesulfurizationof coals and biobeneficiation of iron ores Another potentialutilization of microorganisms is that they could be used toflocculate finely divided minerals andor be used as mineralsurface modifiers or flotation collectors
2 Bioleaching of Sulfide Ores
21 Microorganisms Involved in Leaching Processes Themostimportant group of bacteria which are involved in sul-fide minerals leaching are the acidophilic Thiobacilli which
2 Journal of Mining
belongs to the family Thiobacteriacrae They have the abilityto use the oxidation of inorganic sulfur and its compoundsto produce energy for growth They are therefore referredto as chemolithotrophs They include the autotrophs whichderive their carbon for growth solely from carbon dioxidemixotrophs that can utilize carbon derived from organiccompounds and carbon dioxide and the heterotrophs whosesole source of carbon is obtained fromorganic substratesThemajority of the Thiobacilli species are active between 30 and35∘C However moderately thermophilic species have beenisolated which grow best at temperature of 45ndash50∘C [6]
In order of importance the Thiobacilli which areinvolved in mineral leaching are Acidithiobacillus ferrooxi-dans Thiobacillus thiooxidans Thiobacillus acidophilus andThiobacillus oranoporus Acidithiobacillus ferrooxidans is themost important of the above species [7ndash9] This species isable not only to utilize inorganic sulfur compounds butalso to oxidize ferrous iron in inorganic substrates Theirdifferentiation is based upon their capacity to oxidize eitherelemental sulphur or various sulfide minerals
Acidithiobacillus ferrooxidans is an aerobic acidophilicautotrophic Gram-negative bacterium It is rod-shapedbacterium and is active above pH 20 [10] Mesophilic strainshave an optimum temperature of 35∘C for growth It requiresa source of nitrogen phosphate and trace amounts ofcalcium magnesium and potassium Its energy for growthis obtained from the oxidation of ferrous iron insolublesulfides and soluble sulphur compounds The 9K nutrientmediumwas derived formass production ofAcidithiobacillusferrooxidans cells [11] There are also some Acidithiobacillusferrooxidans species which are also acidophilic autotrophicrod shaped mesophilic bacteria which grow on elementalsulfur and soluble sulfur compounds but unable to oxidizeferrous iron or insoluble sulfides
Thiobacillus acidophilus and Thiobacillus oranoporus aremesophilic mixotrophic acidophilus rod-shaped bacteriathat oxidize only elemental sulfur for growth They growat pH 15ndash50 with an optimum value from 25 to 30Being unable to oxidize insoluble sulfides their role inmineral leaching may only be to consume organic com-pounds excreted by Acidithiobacillus ferrooxidans which aredetrimental to the latter organismrsquos growth [12]
In recent years moderately and extremely thermophilicand acidophilic bacteria which are able to oxidise iron sulfurand mineral sulfides have been isolated and tested [6 13ndash15]Moderately thermophilicThiobacilli have been demonstratedto be heterotrophic with optimum temperatures for growthbetween 45 and 60∘C Strains of thermophilic organisms of aSulfolobus type grow within a temperature range of 55ndash85∘CTheir role in solubilizing metal is not completely understoodHowever the usefulness of thermophilicmicroorganisms canalso be extended to bioremediation activities
211 Mechanisms of Bioleaching Some doubt still surroundsthe exact role of bacteria in the oxidation of sulfide mineralsbecause of the inability to discretely separate reactions whichare solely promoted by bacteria from those which are simplychemical The concept of direct and indirect modes of
bacterial leaching of metal sulfides (MS) was introduced fewdecades ago [10]
In the direct mode of bacterial leaching mechanism thesulfide is oxidized to metal sulfate
MS + 2O2
bacteria997888997888997888997888997888rarr MSO
4
(1)
where M is a bivalent metal The heavy metal sulfides aregenerally insoluble in aqueous acid leach media while theirsulfates are soluble In some cases the oxidation product isinsoluble as for example in the case of lead sulfide leachingThis fact can be utilized for selective leaching [16] to separatesoluble zinc copper and cadmium from insoluble lead Inthe direct mode of bacterial oxidation bacteria must remainclose to the surface of the solid substrate
In the indirect mode ferric ion produced from bacterialoxidation of pyrite which is always associated with sulfideminerals is the oxidant The sequence of reactions is asfollows
2FeS2+ 75O
2+H2O bacteria997888997888997888997888997888rarr Fe
So + 15O2+H2O bacteria997888997888997888997888997888rarr H
2SO4
(5)
In the absence of bacteria elemental sulfur deposited on thesurface of the particles may grow in proportion so as to createa thick enough layer to inhibit the progress of the leachingprocess The sulfuric acid produced may further react withthe oxide contents (MO) of the ore thus contributing to themetal dissolution process
Again the reaction by-products ferrous iron and sulfur areoxidized by bacteria to ferric iron and sulfuric acid followingreactions (4) and (5)
The growth of Acidithiobacillus ferrooxidans is measuredby cell count of the supernatants of the suspensions whereasthe extent of bacterial attachmentadsorption to mineralsduring leaching was estimated from cell protein concentra-tion of the solid and liquid phases Probable mechanism ofattachment and detachment of bacteria was also discussed[17 18] Recently a two-step mechanism for bioleaching wasproposed [19 20] It involves chemical ferric reactionwith themineral to produce ferrous salt and then bacterial oxidationof ferrous iron to ferric completes a closed loop of reactions
Journal of Mining 3
212 Developments in Bioleaching of Sulfide Ores In 1947Acidithiobacillus ferrooxidans the main microorganismresponsible for metal sulphide oxidation was first isolatedand characterized [21] It was found that this bacteriumcould oxidize the sulfide part of the mineral to sulfuric acidand the ferrous ion to ferric ion This oxidation ability canbe demonstrated in the oxidation of pyrite which is almostalways found with the sulfide minerals equation (2)
The bioleaching of pyrite will be discussed later whenreferring to coal desulfurization in Section 4 entitled bioben-eficiation Numerous systematic studies [22ndash25] have sub-sequently revealed that Acidithiobacillus ferrooxidans underacidic leaching conditions can attack most sulfide miner-als producing water-soluble metal sulphates The optimumleaching conditions can be summarized as follows growthmedia (nutrients) [26 27] temperature 35∘C [28 29] pH 23[30] Eh below 500mV in order to avoid jarosite precipitation[31 32] high specific surface area of solids [33 34] and prioradaptation of bacteria to specific substrate [23 35 36] Largescale heap and dump leaching operations were built so as toprovide the best growth conditions for themicroorganisms inorder to harvest their beneficial effects in dissolution of metalfrom mining wastes [37 38]
Most investigations concerning the bioleaching of copperfrom low-grade ores have been conducted in the laboratoryusing small columns or simulated in large scale tests Theinfluence of variations in the mineralogical composition andtextural features of copper ores as well as process variableshave been examined [39 40] Chalcopyrite is leached in thepresence of bacteria in (7)
Again the above reaction by-products ferrous iron andsulfur are oxidized by bacteria to ferric iron and sulfuric acid
The oxidation mechanisms for chalcocite (Cu2S) can be
In addition extensive studies were conducted with ther-mophilic microorganism in the temperature range of 45ndash85∘C [41ndash43]The advantage of using thermophilic organismsin the leaching of sulfide minerals is that at higher temper-ature the reaction kinetics is expected to increase A newgenus of thermophilic spore-forming bacteria sulfobacilluswas reported [43]
Due to the refractory nature of the chalcopyrite theutilization of high temperatures and thermophilic bacteriahas been investigated It is reported that typical copperextraction yields obtained by mesophilic bacteria are about30 whereas copper extraction yields of more than 98 canbe obtained in shorter periods by thermophilic bioleaching[44 45] A study concerning bioleaching of chalcopyriteshowed that the bioleaching of chalcopyrite is controlled bythe oxidation-reduction potential temperature pH and theactivity of the thermophile used [46 47]
Recently a comparative study [48] on the bioleachingof chalcopyrite concentrates using mesophilic and moder-ately thermophilic bacteria indicated that the moderately
Leaching
SL separation
Recovery of constituents
PbS concentrate
Inoculum
Cd Cu Zn
Barren Solid
Nutrients
Leach residue (lead concentrate)solution
Figure 1 Schematic representation of a selective bacterial leachingprocess of a complex lead sulfide concentrate (SL signifies solid-liquid separation) [16]
thermophilic bacteria have higher ability for copper disso-lution These results show that copper dissolution from thechalcopyrite concentrate reached 8752 with the moderatelythermophilic bacteria while it was 3455 with mesophilicculture after 25 days
The applicability of bacterial leaching technique to therecovery of uranium from low-grade ores has been inves-tigated [49 50] In bacterial leaching of uranium ores thetetravalent uranium is oxidized to its hexavalent state whichis soluble by ferric sulfate
UO2+ Fe2(SO4) + 2H
2SO4
chemical997888997888997888997888997888997888rarr H
4[UO2(SO4)3
] + 2FeSO4
(10)
The role of bacteria is to reoxidize ferrous iron to theferric state Ferric sulfate is obtained by metabolic oxidationof pyrite which is always present in the uranium oresBioleaching of copper and uranium ores by heap leachingresulted in substantial saving in the production costs
Bioleaching of zinc sulfide concentrates using bacteria hasbeen investigated [16 51]The following reaction is proposed
ZnS + 2O2
bacteria997888997888997888997888997888rarr ZnSO
4
(11)
Themaximum rate of zinc extraction under optimum condi-tions was around 640mgdm3 h in terms of specific surfacearea particle size and pulp density of the solid substrateSelective extraction of zinc copper and cadmium frombelow the cut-off grade (complex) lead sulfide concentratesis illustrated in the flow diagram in Figure 1 The method isespecially applicable to ores with very fine crystalline inter-growth of lead zinc cadmium and copper sulfides wherequantitative recovery from individualmineral fractions is notpossible by physical separation techniques The leach residuein PbS concentrate leaching in this operation is a high-grade lead concentrate which consists of unreacted PbS andinsoluble PbSO
4 The recovery step my involve precipitation
of iron by increasing the pH to 35 using lime Copper andcadmium are obtained by cementation and zinc hydroxideis precipitated by increasing pH value to 75 using magnesiaZinc hydroxide can be converted to zinc by acidification andelectrowinning [16 23 35 52]
4 Journal of Mining
Almost complete extraction of pentlandite using themicroorganisms Acidithiobacillus ferrooxidans can beexpressed by
(Ni Fe)9S8+ 17625O
2+ 325H
2SO4
bacteria997888997888997888997888997888rarr 45NiSO
4+ 225Fe
2(SO4)3
+ 325H2O
(12)
It was possible to dissolve cobalt and nickel at a high ratefrom the sulfide minerals and to produce Co+2 and Ni2+ ionconcentrations as high as 30 gdm3 and 71 gdm3 respectivelySelective extraction of arsenic from a complex finely dissemi-nated stannic auriferous zinc-copper ore has been described[16 53] A basic flow diagram of this process is shownin Figure 2 In this process the arsenic content of the oreis solubilized by bacteria and after solid-liquid separationit is precipitated by addition of lime to raise the pH toabout 30 The dissolved copper is recovered by cementationwith scrap iron and the solution is recycled From the solidresidue of bacterial leaching the unreacted copper ore isremoved by flotation yielding copper sulfide concentrateand a tin enriched residue The process in Figure 2 can alsobe applied for leaching of gold-arsenic sulfides from finelydisseminated metal in the sulfide matrix In this case thepreciousmetals remain in the residue frombacterial leachingThe residue is neutralized by addition of lime and treatedwith cyanide solution to dissolve gold and silver From theleach solution arsenic is precipitated and discarded Thebacterial leaching in these studies can be considered as apreoxidation step which exposes the precious metals forsubsequent cyanidation or thiourea leaching [5]
Lately bacterial leachingmethods gained further impetuswith the introduction of biopreoxidation processes for theliberation of precious metals from sulfide-bearing minerals[54ndash56] If gold occurs in a finely disseminated form withinthe sulfide ore matrix the economic viability of conventionalgold extraction processes by cyanide leaching becomes lessthan marginal Extensive research work has been carried outfor the treatment of the complex gold-bearing sulfide oresIt is reported that pyrite oxidation by bioleaching improvedgold recoveryThis promising improvementwas proportionalto the degree of oxidation (Figure 3) For example with 84oxidation of pyrite gold recovery in solution reached 81
Bioleaching research has demonstrated that microorgan-isms can tolerate exceptionally high metal ion concentration(120 gL zinc 72 gL nickel 30 gL cobalt 55 gL copper and12 gL U
3O8) and high hydrogen ion concentration (acid
media of pH range 1ndash5) during leaching of sulfide minerals[43]
Genetic manipulations of leaching organisms were ini-tiated in the eighties [16 58] The purpose of these studieswas to develop specific metal extraction using microorgan-isms capable of a high rate of metabolic conversion andresistant to toxic elements Biosorption technology using freeor immobilized alive or dead cells or their derivatives infilms aggregates or pellets was illustrated It was found thatbiosorption technology is especially applicable to the removalof toxic metal contamination from large volume of industrial
L
Leaching
Precipitation
SL separation
SL separation
Cementation
Flotation
Sn-Cu-As Sulfide ore
Inoculum
Cu
Fe scrap
Cu
L
Solid
Solid
L
Nutrients
Lime
As residueSn
Figure 2 Bacterial leaching process for difficult-to-dress Sn-As-Cuores [16]
Pyrite oxidation ()
Gol
d ex
trac
tion
()
20
30
40
50
60
70
80
90
0 20 40 60 80 100
Figure 3 Effects of biological pyrite oxidation on gold recoveryfrom Porgera concentrate [57]
waste streams containing trace amounts of heavy metals andradionuclide [59]
3 Bioprocessing of Refractory Gold Ores
Bacterial leaching processes will be significant in the treat-ment of difficult-to-process refractory ores [60ndash63] Thegold in refractory ores is encapsulated as fine particles inthe crystal structure of sulfide matrix such as pyrite (FeS
2)
and arsenopyrite (FeAsS) This makes the efficiency of thecyanidation process very low since the cyanide solutioncannot penetrate the sulfide-bearing gold crystals and dis-solve gold particles even after fine grinding Therefore anoxidative pretreatment is necessary to decrease the refractoryproperties of the ore Roasting is sometimes used but it ishighly energy consuming and involves a costly off-gas neu-tralization system to prevent atmospheric pollution [64 65]Both pressure oxidation and oxidation by nitric acid requirehigh temperature andor corrosion-resistant materials whichare costly items Hence biological pretreatment becomes an
Journal of Mining 5
interesting alternative route This route leads to environ-mental protection and low-cost processes [64] Research anddevelopments in this direction have been stimulated by thebuoyant price of the precious metal and also by the fact thatconventional methods of extraction are not able to produce asufficiently high recovery of the contained value [66] It hasbeen demonstrated by both laboratory and pilot test workthat such process is feasible [67] The biological pretreatmentof refractory gold ores is based on the ability of somemicroorganisms such as Acidithiobacillus ferrooxidans andThiobacillus thiooxidans to oxidize and dissolve the bearing-gold sulfide minerals thus liberating the entrapped goldparticles thereby rendering it amenable to the cyanidationprocess [57 64] Advancements in this area have been madeon industrial scale to improve the rate of oxidation and toreduce cyanide consumptions in downstream gold recovery[68] The results indicated a direct relationship betweenthe degree of sulphide mineral oxidation and percent goldrecovery Complete oxidation of sulphides is not necessaryto achieve significant enhancement of gold recovery Onthe basis of the sulphide entity high gold recoveries can beobtained with as low as 50 oxidation of the total sulphides
4 Biobeneficiation
Biobeneficiation refers to removal of undesirable mineralcomponents from an ore through interactions with microor-ganisms which bring about their selective removal by abioleaching process Compared to bioleaching of sulfidemin-erals by Thiobacilli bioleaching of nonsulfide minerals hasreceived little attention in the past For example desulfuriza-tion of coal bioleaching of aluminum from aluminosilicatesremoval of alumina and silica from iron ores and so forthhave been extensively studied These interactions lead toenriching these desired mineral constituents in the solidore matrix mediated by a number of surface chemical andphysiochemical phenomena The mediation roles includealteration of the surface chemistry of minerals generationof metabolic products which cause chemical dissolutionselective dissolution of mineral phases in an ore matrixand sorption accumulation and precipitation of ions andcompounds on solid surfaces
In order to minimize the potential deleterious impact ofincreased amounts of sulfur dioxide emission due to coalburning the sulfur content of coal must be reduced Thebiodesulfurization of coal presents a potentially attractivealternative to chemical and physical methods [60 69 71] Inthe biodesulfurization process the pyrite content of coal willbe oxidized to water-soluble ferric sulfate and sulfuric acidaccording to (2) The dissolved ferric sulfate is removed fromthe coal in the dewatering step The coal is then washed anddried prior to combustion
Experimental investigations indicated that bacteria andfungi could be effectively used to remove iron and silicafrom clays sands and bauxite ores [15 72 73] Successfulcommercialization of bauxite biobeneficiation was proposed[74] Biological removal of calcium and iron from a low-grade bauxite ore was discussed with respect to Bacillus
polymyxa Growth conditions and probable mechanisms inthe biological removal of calcium and iron from the bauxiteore were outlined by Anand et al [75] From the reportedresults changes in the pHof the leachmedium correlatedwellwith the calcium dissolutionThe presence of bacteria lowersthe pH and hence facilitates calcium dissolution
Iron ores generally contain alumina silica sulfur andphosphorous as the main gangue minerals These impuritieshave adverse effects on reducibility of iron oxides coke rateconsumption and blast furnace operation and productivityfor steel making Various studies have examined the useof the heterotrophic bacteria and fungi for removal ofalumina and silica from iron ores for improving the ironcontent of the concerned ore The iron ore beneficiationwas carried out by secondary metabolites produced by theseheterotrophic microorganisms [76 77] It has been reportedthat in situ leaching of an iron ore with fungal strains suchasAspergillus fumigatus Penicillium citrinum andAspergillusflavus resulted in 7 6 and 17 removal of aluminaand 8 4 and 16 removal of silica respectively Bacil-lus polymyxa Bacillus sphaericus and Pseudomonas putidaensured silica removal percentage of 106 53 and 20respectively Aspergillus flavus and Pseudomonas putida weremost efficient among all the bacterial and fungal strains usedensuring an increase in iron content of about 3 at the end of10 days leaching [78]
Ronini [79] reported that heterotrophic organisms canbe used to leach out the alumina and silica from the slimesgenerated by Tata Iron and Steel Company in India Heinvestigated the feasibility of Bacillus to leach the slimesand increase its iron content At pH 7 leaching for 5 daysat inoculums size of 20 Ronini obtained an optimumrecovery of 79 of the iron content in the slimes
5 Biosurface Modification
Adhesion of microorganisms to mineral surfaces is knownto alter the hydrophobicity of minerals It has been demon-strated that Acidithiobacillus ferrooxidans is suitable for therapid treatment of sulfide ores where leaching is not thedesired outcome Surface treatment of sulfide minerals withbacterial solution is shown to influence their superficialchemical properties thus altering their response in processessuch as froth flotation andor selective flocculation Thistechnique is being evaluated as a method of enhancing thephysical separation of pyrite from coal in fine coal flotationcircuits and is suggested as an alternative method to the totalleaching of pyrite from coal [80 81] In this technique thecoal pulp is conditioned with Acidithiobacillus ferrooxidansbacteria for about 30 minutes and thus renders pyrite surfaceto be hydrophilic This in turn enhances the selectiveflotation of coal from pyrite Table 1 shows typical resultsof a study concerning bacterial leaching versus bacterialconditioning followed by flotation of minus 28 mesh coalcontaining 288 pyritic sulfur [69]
In a study concerning the effect of bacterial conditioningof sphalerite and galena it was found that the floatabilityof galena decreased markedly (Figure 4) due to oxidation of
6 Journal of Mining
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
belongs to the family Thiobacteriacrae They have the abilityto use the oxidation of inorganic sulfur and its compoundsto produce energy for growth They are therefore referredto as chemolithotrophs They include the autotrophs whichderive their carbon for growth solely from carbon dioxidemixotrophs that can utilize carbon derived from organiccompounds and carbon dioxide and the heterotrophs whosesole source of carbon is obtained fromorganic substratesThemajority of the Thiobacilli species are active between 30 and35∘C However moderately thermophilic species have beenisolated which grow best at temperature of 45ndash50∘C [6]
In order of importance the Thiobacilli which areinvolved in mineral leaching are Acidithiobacillus ferrooxi-dans Thiobacillus thiooxidans Thiobacillus acidophilus andThiobacillus oranoporus Acidithiobacillus ferrooxidans is themost important of the above species [7ndash9] This species isable not only to utilize inorganic sulfur compounds butalso to oxidize ferrous iron in inorganic substrates Theirdifferentiation is based upon their capacity to oxidize eitherelemental sulphur or various sulfide minerals
Acidithiobacillus ferrooxidans is an aerobic acidophilicautotrophic Gram-negative bacterium It is rod-shapedbacterium and is active above pH 20 [10] Mesophilic strainshave an optimum temperature of 35∘C for growth It requiresa source of nitrogen phosphate and trace amounts ofcalcium magnesium and potassium Its energy for growthis obtained from the oxidation of ferrous iron insolublesulfides and soluble sulphur compounds The 9K nutrientmediumwas derived formass production ofAcidithiobacillusferrooxidans cells [11] There are also some Acidithiobacillusferrooxidans species which are also acidophilic autotrophicrod shaped mesophilic bacteria which grow on elementalsulfur and soluble sulfur compounds but unable to oxidizeferrous iron or insoluble sulfides
Thiobacillus acidophilus and Thiobacillus oranoporus aremesophilic mixotrophic acidophilus rod-shaped bacteriathat oxidize only elemental sulfur for growth They growat pH 15ndash50 with an optimum value from 25 to 30Being unable to oxidize insoluble sulfides their role inmineral leaching may only be to consume organic com-pounds excreted by Acidithiobacillus ferrooxidans which aredetrimental to the latter organismrsquos growth [12]
In recent years moderately and extremely thermophilicand acidophilic bacteria which are able to oxidise iron sulfurand mineral sulfides have been isolated and tested [6 13ndash15]Moderately thermophilicThiobacilli have been demonstratedto be heterotrophic with optimum temperatures for growthbetween 45 and 60∘C Strains of thermophilic organisms of aSulfolobus type grow within a temperature range of 55ndash85∘CTheir role in solubilizing metal is not completely understoodHowever the usefulness of thermophilicmicroorganisms canalso be extended to bioremediation activities
211 Mechanisms of Bioleaching Some doubt still surroundsthe exact role of bacteria in the oxidation of sulfide mineralsbecause of the inability to discretely separate reactions whichare solely promoted by bacteria from those which are simplychemical The concept of direct and indirect modes of
bacterial leaching of metal sulfides (MS) was introduced fewdecades ago [10]
In the direct mode of bacterial leaching mechanism thesulfide is oxidized to metal sulfate
MS + 2O2
bacteria997888997888997888997888997888rarr MSO
4
(1)
where M is a bivalent metal The heavy metal sulfides aregenerally insoluble in aqueous acid leach media while theirsulfates are soluble In some cases the oxidation product isinsoluble as for example in the case of lead sulfide leachingThis fact can be utilized for selective leaching [16] to separatesoluble zinc copper and cadmium from insoluble lead Inthe direct mode of bacterial oxidation bacteria must remainclose to the surface of the solid substrate
In the indirect mode ferric ion produced from bacterialoxidation of pyrite which is always associated with sulfideminerals is the oxidant The sequence of reactions is asfollows
2FeS2+ 75O
2+H2O bacteria997888997888997888997888997888rarr Fe
So + 15O2+H2O bacteria997888997888997888997888997888rarr H
2SO4
(5)
In the absence of bacteria elemental sulfur deposited on thesurface of the particles may grow in proportion so as to createa thick enough layer to inhibit the progress of the leachingprocess The sulfuric acid produced may further react withthe oxide contents (MO) of the ore thus contributing to themetal dissolution process
Again the reaction by-products ferrous iron and sulfur areoxidized by bacteria to ferric iron and sulfuric acid followingreactions (4) and (5)
The growth of Acidithiobacillus ferrooxidans is measuredby cell count of the supernatants of the suspensions whereasthe extent of bacterial attachmentadsorption to mineralsduring leaching was estimated from cell protein concentra-tion of the solid and liquid phases Probable mechanism ofattachment and detachment of bacteria was also discussed[17 18] Recently a two-step mechanism for bioleaching wasproposed [19 20] It involves chemical ferric reactionwith themineral to produce ferrous salt and then bacterial oxidationof ferrous iron to ferric completes a closed loop of reactions
Journal of Mining 3
212 Developments in Bioleaching of Sulfide Ores In 1947Acidithiobacillus ferrooxidans the main microorganismresponsible for metal sulphide oxidation was first isolatedand characterized [21] It was found that this bacteriumcould oxidize the sulfide part of the mineral to sulfuric acidand the ferrous ion to ferric ion This oxidation ability canbe demonstrated in the oxidation of pyrite which is almostalways found with the sulfide minerals equation (2)
The bioleaching of pyrite will be discussed later whenreferring to coal desulfurization in Section 4 entitled bioben-eficiation Numerous systematic studies [22ndash25] have sub-sequently revealed that Acidithiobacillus ferrooxidans underacidic leaching conditions can attack most sulfide miner-als producing water-soluble metal sulphates The optimumleaching conditions can be summarized as follows growthmedia (nutrients) [26 27] temperature 35∘C [28 29] pH 23[30] Eh below 500mV in order to avoid jarosite precipitation[31 32] high specific surface area of solids [33 34] and prioradaptation of bacteria to specific substrate [23 35 36] Largescale heap and dump leaching operations were built so as toprovide the best growth conditions for themicroorganisms inorder to harvest their beneficial effects in dissolution of metalfrom mining wastes [37 38]
Most investigations concerning the bioleaching of copperfrom low-grade ores have been conducted in the laboratoryusing small columns or simulated in large scale tests Theinfluence of variations in the mineralogical composition andtextural features of copper ores as well as process variableshave been examined [39 40] Chalcopyrite is leached in thepresence of bacteria in (7)
Again the above reaction by-products ferrous iron andsulfur are oxidized by bacteria to ferric iron and sulfuric acid
The oxidation mechanisms for chalcocite (Cu2S) can be
In addition extensive studies were conducted with ther-mophilic microorganism in the temperature range of 45ndash85∘C [41ndash43]The advantage of using thermophilic organismsin the leaching of sulfide minerals is that at higher temper-ature the reaction kinetics is expected to increase A newgenus of thermophilic spore-forming bacteria sulfobacilluswas reported [43]
Due to the refractory nature of the chalcopyrite theutilization of high temperatures and thermophilic bacteriahas been investigated It is reported that typical copperextraction yields obtained by mesophilic bacteria are about30 whereas copper extraction yields of more than 98 canbe obtained in shorter periods by thermophilic bioleaching[44 45] A study concerning bioleaching of chalcopyriteshowed that the bioleaching of chalcopyrite is controlled bythe oxidation-reduction potential temperature pH and theactivity of the thermophile used [46 47]
Recently a comparative study [48] on the bioleachingof chalcopyrite concentrates using mesophilic and moder-ately thermophilic bacteria indicated that the moderately
Leaching
SL separation
Recovery of constituents
PbS concentrate
Inoculum
Cd Cu Zn
Barren Solid
Nutrients
Leach residue (lead concentrate)solution
Figure 1 Schematic representation of a selective bacterial leachingprocess of a complex lead sulfide concentrate (SL signifies solid-liquid separation) [16]
thermophilic bacteria have higher ability for copper disso-lution These results show that copper dissolution from thechalcopyrite concentrate reached 8752 with the moderatelythermophilic bacteria while it was 3455 with mesophilicculture after 25 days
The applicability of bacterial leaching technique to therecovery of uranium from low-grade ores has been inves-tigated [49 50] In bacterial leaching of uranium ores thetetravalent uranium is oxidized to its hexavalent state whichis soluble by ferric sulfate
UO2+ Fe2(SO4) + 2H
2SO4
chemical997888997888997888997888997888997888rarr H
4[UO2(SO4)3
] + 2FeSO4
(10)
The role of bacteria is to reoxidize ferrous iron to theferric state Ferric sulfate is obtained by metabolic oxidationof pyrite which is always present in the uranium oresBioleaching of copper and uranium ores by heap leachingresulted in substantial saving in the production costs
Bioleaching of zinc sulfide concentrates using bacteria hasbeen investigated [16 51]The following reaction is proposed
ZnS + 2O2
bacteria997888997888997888997888997888rarr ZnSO
4
(11)
Themaximum rate of zinc extraction under optimum condi-tions was around 640mgdm3 h in terms of specific surfacearea particle size and pulp density of the solid substrateSelective extraction of zinc copper and cadmium frombelow the cut-off grade (complex) lead sulfide concentratesis illustrated in the flow diagram in Figure 1 The method isespecially applicable to ores with very fine crystalline inter-growth of lead zinc cadmium and copper sulfides wherequantitative recovery from individualmineral fractions is notpossible by physical separation techniques The leach residuein PbS concentrate leaching in this operation is a high-grade lead concentrate which consists of unreacted PbS andinsoluble PbSO
4 The recovery step my involve precipitation
of iron by increasing the pH to 35 using lime Copper andcadmium are obtained by cementation and zinc hydroxideis precipitated by increasing pH value to 75 using magnesiaZinc hydroxide can be converted to zinc by acidification andelectrowinning [16 23 35 52]
4 Journal of Mining
Almost complete extraction of pentlandite using themicroorganisms Acidithiobacillus ferrooxidans can beexpressed by
(Ni Fe)9S8+ 17625O
2+ 325H
2SO4
bacteria997888997888997888997888997888rarr 45NiSO
4+ 225Fe
2(SO4)3
+ 325H2O
(12)
It was possible to dissolve cobalt and nickel at a high ratefrom the sulfide minerals and to produce Co+2 and Ni2+ ionconcentrations as high as 30 gdm3 and 71 gdm3 respectivelySelective extraction of arsenic from a complex finely dissemi-nated stannic auriferous zinc-copper ore has been described[16 53] A basic flow diagram of this process is shownin Figure 2 In this process the arsenic content of the oreis solubilized by bacteria and after solid-liquid separationit is precipitated by addition of lime to raise the pH toabout 30 The dissolved copper is recovered by cementationwith scrap iron and the solution is recycled From the solidresidue of bacterial leaching the unreacted copper ore isremoved by flotation yielding copper sulfide concentrateand a tin enriched residue The process in Figure 2 can alsobe applied for leaching of gold-arsenic sulfides from finelydisseminated metal in the sulfide matrix In this case thepreciousmetals remain in the residue frombacterial leachingThe residue is neutralized by addition of lime and treatedwith cyanide solution to dissolve gold and silver From theleach solution arsenic is precipitated and discarded Thebacterial leaching in these studies can be considered as apreoxidation step which exposes the precious metals forsubsequent cyanidation or thiourea leaching [5]
Lately bacterial leachingmethods gained further impetuswith the introduction of biopreoxidation processes for theliberation of precious metals from sulfide-bearing minerals[54ndash56] If gold occurs in a finely disseminated form withinthe sulfide ore matrix the economic viability of conventionalgold extraction processes by cyanide leaching becomes lessthan marginal Extensive research work has been carried outfor the treatment of the complex gold-bearing sulfide oresIt is reported that pyrite oxidation by bioleaching improvedgold recoveryThis promising improvementwas proportionalto the degree of oxidation (Figure 3) For example with 84oxidation of pyrite gold recovery in solution reached 81
Bioleaching research has demonstrated that microorgan-isms can tolerate exceptionally high metal ion concentration(120 gL zinc 72 gL nickel 30 gL cobalt 55 gL copper and12 gL U
3O8) and high hydrogen ion concentration (acid
media of pH range 1ndash5) during leaching of sulfide minerals[43]
Genetic manipulations of leaching organisms were ini-tiated in the eighties [16 58] The purpose of these studieswas to develop specific metal extraction using microorgan-isms capable of a high rate of metabolic conversion andresistant to toxic elements Biosorption technology using freeor immobilized alive or dead cells or their derivatives infilms aggregates or pellets was illustrated It was found thatbiosorption technology is especially applicable to the removalof toxic metal contamination from large volume of industrial
L
Leaching
Precipitation
SL separation
SL separation
Cementation
Flotation
Sn-Cu-As Sulfide ore
Inoculum
Cu
Fe scrap
Cu
L
Solid
Solid
L
Nutrients
Lime
As residueSn
Figure 2 Bacterial leaching process for difficult-to-dress Sn-As-Cuores [16]
Pyrite oxidation ()
Gol
d ex
trac
tion
()
20
30
40
50
60
70
80
90
0 20 40 60 80 100
Figure 3 Effects of biological pyrite oxidation on gold recoveryfrom Porgera concentrate [57]
waste streams containing trace amounts of heavy metals andradionuclide [59]
3 Bioprocessing of Refractory Gold Ores
Bacterial leaching processes will be significant in the treat-ment of difficult-to-process refractory ores [60ndash63] Thegold in refractory ores is encapsulated as fine particles inthe crystal structure of sulfide matrix such as pyrite (FeS
2)
and arsenopyrite (FeAsS) This makes the efficiency of thecyanidation process very low since the cyanide solutioncannot penetrate the sulfide-bearing gold crystals and dis-solve gold particles even after fine grinding Therefore anoxidative pretreatment is necessary to decrease the refractoryproperties of the ore Roasting is sometimes used but it ishighly energy consuming and involves a costly off-gas neu-tralization system to prevent atmospheric pollution [64 65]Both pressure oxidation and oxidation by nitric acid requirehigh temperature andor corrosion-resistant materials whichare costly items Hence biological pretreatment becomes an
Journal of Mining 5
interesting alternative route This route leads to environ-mental protection and low-cost processes [64] Research anddevelopments in this direction have been stimulated by thebuoyant price of the precious metal and also by the fact thatconventional methods of extraction are not able to produce asufficiently high recovery of the contained value [66] It hasbeen demonstrated by both laboratory and pilot test workthat such process is feasible [67] The biological pretreatmentof refractory gold ores is based on the ability of somemicroorganisms such as Acidithiobacillus ferrooxidans andThiobacillus thiooxidans to oxidize and dissolve the bearing-gold sulfide minerals thus liberating the entrapped goldparticles thereby rendering it amenable to the cyanidationprocess [57 64] Advancements in this area have been madeon industrial scale to improve the rate of oxidation and toreduce cyanide consumptions in downstream gold recovery[68] The results indicated a direct relationship betweenthe degree of sulphide mineral oxidation and percent goldrecovery Complete oxidation of sulphides is not necessaryto achieve significant enhancement of gold recovery Onthe basis of the sulphide entity high gold recoveries can beobtained with as low as 50 oxidation of the total sulphides
4 Biobeneficiation
Biobeneficiation refers to removal of undesirable mineralcomponents from an ore through interactions with microor-ganisms which bring about their selective removal by abioleaching process Compared to bioleaching of sulfidemin-erals by Thiobacilli bioleaching of nonsulfide minerals hasreceived little attention in the past For example desulfuriza-tion of coal bioleaching of aluminum from aluminosilicatesremoval of alumina and silica from iron ores and so forthhave been extensively studied These interactions lead toenriching these desired mineral constituents in the solidore matrix mediated by a number of surface chemical andphysiochemical phenomena The mediation roles includealteration of the surface chemistry of minerals generationof metabolic products which cause chemical dissolutionselective dissolution of mineral phases in an ore matrixand sorption accumulation and precipitation of ions andcompounds on solid surfaces
In order to minimize the potential deleterious impact ofincreased amounts of sulfur dioxide emission due to coalburning the sulfur content of coal must be reduced Thebiodesulfurization of coal presents a potentially attractivealternative to chemical and physical methods [60 69 71] Inthe biodesulfurization process the pyrite content of coal willbe oxidized to water-soluble ferric sulfate and sulfuric acidaccording to (2) The dissolved ferric sulfate is removed fromthe coal in the dewatering step The coal is then washed anddried prior to combustion
Experimental investigations indicated that bacteria andfungi could be effectively used to remove iron and silicafrom clays sands and bauxite ores [15 72 73] Successfulcommercialization of bauxite biobeneficiation was proposed[74] Biological removal of calcium and iron from a low-grade bauxite ore was discussed with respect to Bacillus
polymyxa Growth conditions and probable mechanisms inthe biological removal of calcium and iron from the bauxiteore were outlined by Anand et al [75] From the reportedresults changes in the pHof the leachmedium correlatedwellwith the calcium dissolutionThe presence of bacteria lowersthe pH and hence facilitates calcium dissolution
Iron ores generally contain alumina silica sulfur andphosphorous as the main gangue minerals These impuritieshave adverse effects on reducibility of iron oxides coke rateconsumption and blast furnace operation and productivityfor steel making Various studies have examined the useof the heterotrophic bacteria and fungi for removal ofalumina and silica from iron ores for improving the ironcontent of the concerned ore The iron ore beneficiationwas carried out by secondary metabolites produced by theseheterotrophic microorganisms [76 77] It has been reportedthat in situ leaching of an iron ore with fungal strains suchasAspergillus fumigatus Penicillium citrinum andAspergillusflavus resulted in 7 6 and 17 removal of aluminaand 8 4 and 16 removal of silica respectively Bacil-lus polymyxa Bacillus sphaericus and Pseudomonas putidaensured silica removal percentage of 106 53 and 20respectively Aspergillus flavus and Pseudomonas putida weremost efficient among all the bacterial and fungal strains usedensuring an increase in iron content of about 3 at the end of10 days leaching [78]
Ronini [79] reported that heterotrophic organisms canbe used to leach out the alumina and silica from the slimesgenerated by Tata Iron and Steel Company in India Heinvestigated the feasibility of Bacillus to leach the slimesand increase its iron content At pH 7 leaching for 5 daysat inoculums size of 20 Ronini obtained an optimumrecovery of 79 of the iron content in the slimes
5 Biosurface Modification
Adhesion of microorganisms to mineral surfaces is knownto alter the hydrophobicity of minerals It has been demon-strated that Acidithiobacillus ferrooxidans is suitable for therapid treatment of sulfide ores where leaching is not thedesired outcome Surface treatment of sulfide minerals withbacterial solution is shown to influence their superficialchemical properties thus altering their response in processessuch as froth flotation andor selective flocculation Thistechnique is being evaluated as a method of enhancing thephysical separation of pyrite from coal in fine coal flotationcircuits and is suggested as an alternative method to the totalleaching of pyrite from coal [80 81] In this technique thecoal pulp is conditioned with Acidithiobacillus ferrooxidansbacteria for about 30 minutes and thus renders pyrite surfaceto be hydrophilic This in turn enhances the selectiveflotation of coal from pyrite Table 1 shows typical resultsof a study concerning bacterial leaching versus bacterialconditioning followed by flotation of minus 28 mesh coalcontaining 288 pyritic sulfur [69]
In a study concerning the effect of bacterial conditioningof sphalerite and galena it was found that the floatabilityof galena decreased markedly (Figure 4) due to oxidation of
6 Journal of Mining
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
212 Developments in Bioleaching of Sulfide Ores In 1947Acidithiobacillus ferrooxidans the main microorganismresponsible for metal sulphide oxidation was first isolatedand characterized [21] It was found that this bacteriumcould oxidize the sulfide part of the mineral to sulfuric acidand the ferrous ion to ferric ion This oxidation ability canbe demonstrated in the oxidation of pyrite which is almostalways found with the sulfide minerals equation (2)
The bioleaching of pyrite will be discussed later whenreferring to coal desulfurization in Section 4 entitled bioben-eficiation Numerous systematic studies [22ndash25] have sub-sequently revealed that Acidithiobacillus ferrooxidans underacidic leaching conditions can attack most sulfide miner-als producing water-soluble metal sulphates The optimumleaching conditions can be summarized as follows growthmedia (nutrients) [26 27] temperature 35∘C [28 29] pH 23[30] Eh below 500mV in order to avoid jarosite precipitation[31 32] high specific surface area of solids [33 34] and prioradaptation of bacteria to specific substrate [23 35 36] Largescale heap and dump leaching operations were built so as toprovide the best growth conditions for themicroorganisms inorder to harvest their beneficial effects in dissolution of metalfrom mining wastes [37 38]
Most investigations concerning the bioleaching of copperfrom low-grade ores have been conducted in the laboratoryusing small columns or simulated in large scale tests Theinfluence of variations in the mineralogical composition andtextural features of copper ores as well as process variableshave been examined [39 40] Chalcopyrite is leached in thepresence of bacteria in (7)
Again the above reaction by-products ferrous iron andsulfur are oxidized by bacteria to ferric iron and sulfuric acid
The oxidation mechanisms for chalcocite (Cu2S) can be
In addition extensive studies were conducted with ther-mophilic microorganism in the temperature range of 45ndash85∘C [41ndash43]The advantage of using thermophilic organismsin the leaching of sulfide minerals is that at higher temper-ature the reaction kinetics is expected to increase A newgenus of thermophilic spore-forming bacteria sulfobacilluswas reported [43]
Due to the refractory nature of the chalcopyrite theutilization of high temperatures and thermophilic bacteriahas been investigated It is reported that typical copperextraction yields obtained by mesophilic bacteria are about30 whereas copper extraction yields of more than 98 canbe obtained in shorter periods by thermophilic bioleaching[44 45] A study concerning bioleaching of chalcopyriteshowed that the bioleaching of chalcopyrite is controlled bythe oxidation-reduction potential temperature pH and theactivity of the thermophile used [46 47]
Recently a comparative study [48] on the bioleachingof chalcopyrite concentrates using mesophilic and moder-ately thermophilic bacteria indicated that the moderately
Leaching
SL separation
Recovery of constituents
PbS concentrate
Inoculum
Cd Cu Zn
Barren Solid
Nutrients
Leach residue (lead concentrate)solution
Figure 1 Schematic representation of a selective bacterial leachingprocess of a complex lead sulfide concentrate (SL signifies solid-liquid separation) [16]
thermophilic bacteria have higher ability for copper disso-lution These results show that copper dissolution from thechalcopyrite concentrate reached 8752 with the moderatelythermophilic bacteria while it was 3455 with mesophilicculture after 25 days
The applicability of bacterial leaching technique to therecovery of uranium from low-grade ores has been inves-tigated [49 50] In bacterial leaching of uranium ores thetetravalent uranium is oxidized to its hexavalent state whichis soluble by ferric sulfate
UO2+ Fe2(SO4) + 2H
2SO4
chemical997888997888997888997888997888997888rarr H
4[UO2(SO4)3
] + 2FeSO4
(10)
The role of bacteria is to reoxidize ferrous iron to theferric state Ferric sulfate is obtained by metabolic oxidationof pyrite which is always present in the uranium oresBioleaching of copper and uranium ores by heap leachingresulted in substantial saving in the production costs
Bioleaching of zinc sulfide concentrates using bacteria hasbeen investigated [16 51]The following reaction is proposed
ZnS + 2O2
bacteria997888997888997888997888997888rarr ZnSO
4
(11)
Themaximum rate of zinc extraction under optimum condi-tions was around 640mgdm3 h in terms of specific surfacearea particle size and pulp density of the solid substrateSelective extraction of zinc copper and cadmium frombelow the cut-off grade (complex) lead sulfide concentratesis illustrated in the flow diagram in Figure 1 The method isespecially applicable to ores with very fine crystalline inter-growth of lead zinc cadmium and copper sulfides wherequantitative recovery from individualmineral fractions is notpossible by physical separation techniques The leach residuein PbS concentrate leaching in this operation is a high-grade lead concentrate which consists of unreacted PbS andinsoluble PbSO
4 The recovery step my involve precipitation
of iron by increasing the pH to 35 using lime Copper andcadmium are obtained by cementation and zinc hydroxideis precipitated by increasing pH value to 75 using magnesiaZinc hydroxide can be converted to zinc by acidification andelectrowinning [16 23 35 52]
4 Journal of Mining
Almost complete extraction of pentlandite using themicroorganisms Acidithiobacillus ferrooxidans can beexpressed by
(Ni Fe)9S8+ 17625O
2+ 325H
2SO4
bacteria997888997888997888997888997888rarr 45NiSO
4+ 225Fe
2(SO4)3
+ 325H2O
(12)
It was possible to dissolve cobalt and nickel at a high ratefrom the sulfide minerals and to produce Co+2 and Ni2+ ionconcentrations as high as 30 gdm3 and 71 gdm3 respectivelySelective extraction of arsenic from a complex finely dissemi-nated stannic auriferous zinc-copper ore has been described[16 53] A basic flow diagram of this process is shownin Figure 2 In this process the arsenic content of the oreis solubilized by bacteria and after solid-liquid separationit is precipitated by addition of lime to raise the pH toabout 30 The dissolved copper is recovered by cementationwith scrap iron and the solution is recycled From the solidresidue of bacterial leaching the unreacted copper ore isremoved by flotation yielding copper sulfide concentrateand a tin enriched residue The process in Figure 2 can alsobe applied for leaching of gold-arsenic sulfides from finelydisseminated metal in the sulfide matrix In this case thepreciousmetals remain in the residue frombacterial leachingThe residue is neutralized by addition of lime and treatedwith cyanide solution to dissolve gold and silver From theleach solution arsenic is precipitated and discarded Thebacterial leaching in these studies can be considered as apreoxidation step which exposes the precious metals forsubsequent cyanidation or thiourea leaching [5]
Lately bacterial leachingmethods gained further impetuswith the introduction of biopreoxidation processes for theliberation of precious metals from sulfide-bearing minerals[54ndash56] If gold occurs in a finely disseminated form withinthe sulfide ore matrix the economic viability of conventionalgold extraction processes by cyanide leaching becomes lessthan marginal Extensive research work has been carried outfor the treatment of the complex gold-bearing sulfide oresIt is reported that pyrite oxidation by bioleaching improvedgold recoveryThis promising improvementwas proportionalto the degree of oxidation (Figure 3) For example with 84oxidation of pyrite gold recovery in solution reached 81
Bioleaching research has demonstrated that microorgan-isms can tolerate exceptionally high metal ion concentration(120 gL zinc 72 gL nickel 30 gL cobalt 55 gL copper and12 gL U
3O8) and high hydrogen ion concentration (acid
media of pH range 1ndash5) during leaching of sulfide minerals[43]
Genetic manipulations of leaching organisms were ini-tiated in the eighties [16 58] The purpose of these studieswas to develop specific metal extraction using microorgan-isms capable of a high rate of metabolic conversion andresistant to toxic elements Biosorption technology using freeor immobilized alive or dead cells or their derivatives infilms aggregates or pellets was illustrated It was found thatbiosorption technology is especially applicable to the removalof toxic metal contamination from large volume of industrial
L
Leaching
Precipitation
SL separation
SL separation
Cementation
Flotation
Sn-Cu-As Sulfide ore
Inoculum
Cu
Fe scrap
Cu
L
Solid
Solid
L
Nutrients
Lime
As residueSn
Figure 2 Bacterial leaching process for difficult-to-dress Sn-As-Cuores [16]
Pyrite oxidation ()
Gol
d ex
trac
tion
()
20
30
40
50
60
70
80
90
0 20 40 60 80 100
Figure 3 Effects of biological pyrite oxidation on gold recoveryfrom Porgera concentrate [57]
waste streams containing trace amounts of heavy metals andradionuclide [59]
3 Bioprocessing of Refractory Gold Ores
Bacterial leaching processes will be significant in the treat-ment of difficult-to-process refractory ores [60ndash63] Thegold in refractory ores is encapsulated as fine particles inthe crystal structure of sulfide matrix such as pyrite (FeS
2)
and arsenopyrite (FeAsS) This makes the efficiency of thecyanidation process very low since the cyanide solutioncannot penetrate the sulfide-bearing gold crystals and dis-solve gold particles even after fine grinding Therefore anoxidative pretreatment is necessary to decrease the refractoryproperties of the ore Roasting is sometimes used but it ishighly energy consuming and involves a costly off-gas neu-tralization system to prevent atmospheric pollution [64 65]Both pressure oxidation and oxidation by nitric acid requirehigh temperature andor corrosion-resistant materials whichare costly items Hence biological pretreatment becomes an
Journal of Mining 5
interesting alternative route This route leads to environ-mental protection and low-cost processes [64] Research anddevelopments in this direction have been stimulated by thebuoyant price of the precious metal and also by the fact thatconventional methods of extraction are not able to produce asufficiently high recovery of the contained value [66] It hasbeen demonstrated by both laboratory and pilot test workthat such process is feasible [67] The biological pretreatmentof refractory gold ores is based on the ability of somemicroorganisms such as Acidithiobacillus ferrooxidans andThiobacillus thiooxidans to oxidize and dissolve the bearing-gold sulfide minerals thus liberating the entrapped goldparticles thereby rendering it amenable to the cyanidationprocess [57 64] Advancements in this area have been madeon industrial scale to improve the rate of oxidation and toreduce cyanide consumptions in downstream gold recovery[68] The results indicated a direct relationship betweenthe degree of sulphide mineral oxidation and percent goldrecovery Complete oxidation of sulphides is not necessaryto achieve significant enhancement of gold recovery Onthe basis of the sulphide entity high gold recoveries can beobtained with as low as 50 oxidation of the total sulphides
4 Biobeneficiation
Biobeneficiation refers to removal of undesirable mineralcomponents from an ore through interactions with microor-ganisms which bring about their selective removal by abioleaching process Compared to bioleaching of sulfidemin-erals by Thiobacilli bioleaching of nonsulfide minerals hasreceived little attention in the past For example desulfuriza-tion of coal bioleaching of aluminum from aluminosilicatesremoval of alumina and silica from iron ores and so forthhave been extensively studied These interactions lead toenriching these desired mineral constituents in the solidore matrix mediated by a number of surface chemical andphysiochemical phenomena The mediation roles includealteration of the surface chemistry of minerals generationof metabolic products which cause chemical dissolutionselective dissolution of mineral phases in an ore matrixand sorption accumulation and precipitation of ions andcompounds on solid surfaces
In order to minimize the potential deleterious impact ofincreased amounts of sulfur dioxide emission due to coalburning the sulfur content of coal must be reduced Thebiodesulfurization of coal presents a potentially attractivealternative to chemical and physical methods [60 69 71] Inthe biodesulfurization process the pyrite content of coal willbe oxidized to water-soluble ferric sulfate and sulfuric acidaccording to (2) The dissolved ferric sulfate is removed fromthe coal in the dewatering step The coal is then washed anddried prior to combustion
Experimental investigations indicated that bacteria andfungi could be effectively used to remove iron and silicafrom clays sands and bauxite ores [15 72 73] Successfulcommercialization of bauxite biobeneficiation was proposed[74] Biological removal of calcium and iron from a low-grade bauxite ore was discussed with respect to Bacillus
polymyxa Growth conditions and probable mechanisms inthe biological removal of calcium and iron from the bauxiteore were outlined by Anand et al [75] From the reportedresults changes in the pHof the leachmedium correlatedwellwith the calcium dissolutionThe presence of bacteria lowersthe pH and hence facilitates calcium dissolution
Iron ores generally contain alumina silica sulfur andphosphorous as the main gangue minerals These impuritieshave adverse effects on reducibility of iron oxides coke rateconsumption and blast furnace operation and productivityfor steel making Various studies have examined the useof the heterotrophic bacteria and fungi for removal ofalumina and silica from iron ores for improving the ironcontent of the concerned ore The iron ore beneficiationwas carried out by secondary metabolites produced by theseheterotrophic microorganisms [76 77] It has been reportedthat in situ leaching of an iron ore with fungal strains suchasAspergillus fumigatus Penicillium citrinum andAspergillusflavus resulted in 7 6 and 17 removal of aluminaand 8 4 and 16 removal of silica respectively Bacil-lus polymyxa Bacillus sphaericus and Pseudomonas putidaensured silica removal percentage of 106 53 and 20respectively Aspergillus flavus and Pseudomonas putida weremost efficient among all the bacterial and fungal strains usedensuring an increase in iron content of about 3 at the end of10 days leaching [78]
Ronini [79] reported that heterotrophic organisms canbe used to leach out the alumina and silica from the slimesgenerated by Tata Iron and Steel Company in India Heinvestigated the feasibility of Bacillus to leach the slimesand increase its iron content At pH 7 leaching for 5 daysat inoculums size of 20 Ronini obtained an optimumrecovery of 79 of the iron content in the slimes
5 Biosurface Modification
Adhesion of microorganisms to mineral surfaces is knownto alter the hydrophobicity of minerals It has been demon-strated that Acidithiobacillus ferrooxidans is suitable for therapid treatment of sulfide ores where leaching is not thedesired outcome Surface treatment of sulfide minerals withbacterial solution is shown to influence their superficialchemical properties thus altering their response in processessuch as froth flotation andor selective flocculation Thistechnique is being evaluated as a method of enhancing thephysical separation of pyrite from coal in fine coal flotationcircuits and is suggested as an alternative method to the totalleaching of pyrite from coal [80 81] In this technique thecoal pulp is conditioned with Acidithiobacillus ferrooxidansbacteria for about 30 minutes and thus renders pyrite surfaceto be hydrophilic This in turn enhances the selectiveflotation of coal from pyrite Table 1 shows typical resultsof a study concerning bacterial leaching versus bacterialconditioning followed by flotation of minus 28 mesh coalcontaining 288 pyritic sulfur [69]
In a study concerning the effect of bacterial conditioningof sphalerite and galena it was found that the floatabilityof galena decreased markedly (Figure 4) due to oxidation of
6 Journal of Mining
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
[1] Q P Granger ldquoBacterial leaching of mineralsrdquo CollieryGuardian Redhill vol 232 no 6 pp 212ndash214 1984
[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Almost complete extraction of pentlandite using themicroorganisms Acidithiobacillus ferrooxidans can beexpressed by
(Ni Fe)9S8+ 17625O
2+ 325H
2SO4
bacteria997888997888997888997888997888rarr 45NiSO
4+ 225Fe
2(SO4)3
+ 325H2O
(12)
It was possible to dissolve cobalt and nickel at a high ratefrom the sulfide minerals and to produce Co+2 and Ni2+ ionconcentrations as high as 30 gdm3 and 71 gdm3 respectivelySelective extraction of arsenic from a complex finely dissemi-nated stannic auriferous zinc-copper ore has been described[16 53] A basic flow diagram of this process is shownin Figure 2 In this process the arsenic content of the oreis solubilized by bacteria and after solid-liquid separationit is precipitated by addition of lime to raise the pH toabout 30 The dissolved copper is recovered by cementationwith scrap iron and the solution is recycled From the solidresidue of bacterial leaching the unreacted copper ore isremoved by flotation yielding copper sulfide concentrateand a tin enriched residue The process in Figure 2 can alsobe applied for leaching of gold-arsenic sulfides from finelydisseminated metal in the sulfide matrix In this case thepreciousmetals remain in the residue frombacterial leachingThe residue is neutralized by addition of lime and treatedwith cyanide solution to dissolve gold and silver From theleach solution arsenic is precipitated and discarded Thebacterial leaching in these studies can be considered as apreoxidation step which exposes the precious metals forsubsequent cyanidation or thiourea leaching [5]
Lately bacterial leachingmethods gained further impetuswith the introduction of biopreoxidation processes for theliberation of precious metals from sulfide-bearing minerals[54ndash56] If gold occurs in a finely disseminated form withinthe sulfide ore matrix the economic viability of conventionalgold extraction processes by cyanide leaching becomes lessthan marginal Extensive research work has been carried outfor the treatment of the complex gold-bearing sulfide oresIt is reported that pyrite oxidation by bioleaching improvedgold recoveryThis promising improvementwas proportionalto the degree of oxidation (Figure 3) For example with 84oxidation of pyrite gold recovery in solution reached 81
Bioleaching research has demonstrated that microorgan-isms can tolerate exceptionally high metal ion concentration(120 gL zinc 72 gL nickel 30 gL cobalt 55 gL copper and12 gL U
3O8) and high hydrogen ion concentration (acid
media of pH range 1ndash5) during leaching of sulfide minerals[43]
Genetic manipulations of leaching organisms were ini-tiated in the eighties [16 58] The purpose of these studieswas to develop specific metal extraction using microorgan-isms capable of a high rate of metabolic conversion andresistant to toxic elements Biosorption technology using freeor immobilized alive or dead cells or their derivatives infilms aggregates or pellets was illustrated It was found thatbiosorption technology is especially applicable to the removalof toxic metal contamination from large volume of industrial
L
Leaching
Precipitation
SL separation
SL separation
Cementation
Flotation
Sn-Cu-As Sulfide ore
Inoculum
Cu
Fe scrap
Cu
L
Solid
Solid
L
Nutrients
Lime
As residueSn
Figure 2 Bacterial leaching process for difficult-to-dress Sn-As-Cuores [16]
Pyrite oxidation ()
Gol
d ex
trac
tion
()
20
30
40
50
60
70
80
90
0 20 40 60 80 100
Figure 3 Effects of biological pyrite oxidation on gold recoveryfrom Porgera concentrate [57]
waste streams containing trace amounts of heavy metals andradionuclide [59]
3 Bioprocessing of Refractory Gold Ores
Bacterial leaching processes will be significant in the treat-ment of difficult-to-process refractory ores [60ndash63] Thegold in refractory ores is encapsulated as fine particles inthe crystal structure of sulfide matrix such as pyrite (FeS
2)
and arsenopyrite (FeAsS) This makes the efficiency of thecyanidation process very low since the cyanide solutioncannot penetrate the sulfide-bearing gold crystals and dis-solve gold particles even after fine grinding Therefore anoxidative pretreatment is necessary to decrease the refractoryproperties of the ore Roasting is sometimes used but it ishighly energy consuming and involves a costly off-gas neu-tralization system to prevent atmospheric pollution [64 65]Both pressure oxidation and oxidation by nitric acid requirehigh temperature andor corrosion-resistant materials whichare costly items Hence biological pretreatment becomes an
Journal of Mining 5
interesting alternative route This route leads to environ-mental protection and low-cost processes [64] Research anddevelopments in this direction have been stimulated by thebuoyant price of the precious metal and also by the fact thatconventional methods of extraction are not able to produce asufficiently high recovery of the contained value [66] It hasbeen demonstrated by both laboratory and pilot test workthat such process is feasible [67] The biological pretreatmentof refractory gold ores is based on the ability of somemicroorganisms such as Acidithiobacillus ferrooxidans andThiobacillus thiooxidans to oxidize and dissolve the bearing-gold sulfide minerals thus liberating the entrapped goldparticles thereby rendering it amenable to the cyanidationprocess [57 64] Advancements in this area have been madeon industrial scale to improve the rate of oxidation and toreduce cyanide consumptions in downstream gold recovery[68] The results indicated a direct relationship betweenthe degree of sulphide mineral oxidation and percent goldrecovery Complete oxidation of sulphides is not necessaryto achieve significant enhancement of gold recovery Onthe basis of the sulphide entity high gold recoveries can beobtained with as low as 50 oxidation of the total sulphides
4 Biobeneficiation
Biobeneficiation refers to removal of undesirable mineralcomponents from an ore through interactions with microor-ganisms which bring about their selective removal by abioleaching process Compared to bioleaching of sulfidemin-erals by Thiobacilli bioleaching of nonsulfide minerals hasreceived little attention in the past For example desulfuriza-tion of coal bioleaching of aluminum from aluminosilicatesremoval of alumina and silica from iron ores and so forthhave been extensively studied These interactions lead toenriching these desired mineral constituents in the solidore matrix mediated by a number of surface chemical andphysiochemical phenomena The mediation roles includealteration of the surface chemistry of minerals generationof metabolic products which cause chemical dissolutionselective dissolution of mineral phases in an ore matrixand sorption accumulation and precipitation of ions andcompounds on solid surfaces
In order to minimize the potential deleterious impact ofincreased amounts of sulfur dioxide emission due to coalburning the sulfur content of coal must be reduced Thebiodesulfurization of coal presents a potentially attractivealternative to chemical and physical methods [60 69 71] Inthe biodesulfurization process the pyrite content of coal willbe oxidized to water-soluble ferric sulfate and sulfuric acidaccording to (2) The dissolved ferric sulfate is removed fromthe coal in the dewatering step The coal is then washed anddried prior to combustion
Experimental investigations indicated that bacteria andfungi could be effectively used to remove iron and silicafrom clays sands and bauxite ores [15 72 73] Successfulcommercialization of bauxite biobeneficiation was proposed[74] Biological removal of calcium and iron from a low-grade bauxite ore was discussed with respect to Bacillus
polymyxa Growth conditions and probable mechanisms inthe biological removal of calcium and iron from the bauxiteore were outlined by Anand et al [75] From the reportedresults changes in the pHof the leachmedium correlatedwellwith the calcium dissolutionThe presence of bacteria lowersthe pH and hence facilitates calcium dissolution
Iron ores generally contain alumina silica sulfur andphosphorous as the main gangue minerals These impuritieshave adverse effects on reducibility of iron oxides coke rateconsumption and blast furnace operation and productivityfor steel making Various studies have examined the useof the heterotrophic bacteria and fungi for removal ofalumina and silica from iron ores for improving the ironcontent of the concerned ore The iron ore beneficiationwas carried out by secondary metabolites produced by theseheterotrophic microorganisms [76 77] It has been reportedthat in situ leaching of an iron ore with fungal strains suchasAspergillus fumigatus Penicillium citrinum andAspergillusflavus resulted in 7 6 and 17 removal of aluminaand 8 4 and 16 removal of silica respectively Bacil-lus polymyxa Bacillus sphaericus and Pseudomonas putidaensured silica removal percentage of 106 53 and 20respectively Aspergillus flavus and Pseudomonas putida weremost efficient among all the bacterial and fungal strains usedensuring an increase in iron content of about 3 at the end of10 days leaching [78]
Ronini [79] reported that heterotrophic organisms canbe used to leach out the alumina and silica from the slimesgenerated by Tata Iron and Steel Company in India Heinvestigated the feasibility of Bacillus to leach the slimesand increase its iron content At pH 7 leaching for 5 daysat inoculums size of 20 Ronini obtained an optimumrecovery of 79 of the iron content in the slimes
5 Biosurface Modification
Adhesion of microorganisms to mineral surfaces is knownto alter the hydrophobicity of minerals It has been demon-strated that Acidithiobacillus ferrooxidans is suitable for therapid treatment of sulfide ores where leaching is not thedesired outcome Surface treatment of sulfide minerals withbacterial solution is shown to influence their superficialchemical properties thus altering their response in processessuch as froth flotation andor selective flocculation Thistechnique is being evaluated as a method of enhancing thephysical separation of pyrite from coal in fine coal flotationcircuits and is suggested as an alternative method to the totalleaching of pyrite from coal [80 81] In this technique thecoal pulp is conditioned with Acidithiobacillus ferrooxidansbacteria for about 30 minutes and thus renders pyrite surfaceto be hydrophilic This in turn enhances the selectiveflotation of coal from pyrite Table 1 shows typical resultsof a study concerning bacterial leaching versus bacterialconditioning followed by flotation of minus 28 mesh coalcontaining 288 pyritic sulfur [69]
In a study concerning the effect of bacterial conditioningof sphalerite and galena it was found that the floatabilityof galena decreased markedly (Figure 4) due to oxidation of
6 Journal of Mining
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
[1] Q P Granger ldquoBacterial leaching of mineralsrdquo CollieryGuardian Redhill vol 232 no 6 pp 212ndash214 1984
[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
interesting alternative route This route leads to environ-mental protection and low-cost processes [64] Research anddevelopments in this direction have been stimulated by thebuoyant price of the precious metal and also by the fact thatconventional methods of extraction are not able to produce asufficiently high recovery of the contained value [66] It hasbeen demonstrated by both laboratory and pilot test workthat such process is feasible [67] The biological pretreatmentof refractory gold ores is based on the ability of somemicroorganisms such as Acidithiobacillus ferrooxidans andThiobacillus thiooxidans to oxidize and dissolve the bearing-gold sulfide minerals thus liberating the entrapped goldparticles thereby rendering it amenable to the cyanidationprocess [57 64] Advancements in this area have been madeon industrial scale to improve the rate of oxidation and toreduce cyanide consumptions in downstream gold recovery[68] The results indicated a direct relationship betweenthe degree of sulphide mineral oxidation and percent goldrecovery Complete oxidation of sulphides is not necessaryto achieve significant enhancement of gold recovery Onthe basis of the sulphide entity high gold recoveries can beobtained with as low as 50 oxidation of the total sulphides
4 Biobeneficiation
Biobeneficiation refers to removal of undesirable mineralcomponents from an ore through interactions with microor-ganisms which bring about their selective removal by abioleaching process Compared to bioleaching of sulfidemin-erals by Thiobacilli bioleaching of nonsulfide minerals hasreceived little attention in the past For example desulfuriza-tion of coal bioleaching of aluminum from aluminosilicatesremoval of alumina and silica from iron ores and so forthhave been extensively studied These interactions lead toenriching these desired mineral constituents in the solidore matrix mediated by a number of surface chemical andphysiochemical phenomena The mediation roles includealteration of the surface chemistry of minerals generationof metabolic products which cause chemical dissolutionselective dissolution of mineral phases in an ore matrixand sorption accumulation and precipitation of ions andcompounds on solid surfaces
In order to minimize the potential deleterious impact ofincreased amounts of sulfur dioxide emission due to coalburning the sulfur content of coal must be reduced Thebiodesulfurization of coal presents a potentially attractivealternative to chemical and physical methods [60 69 71] Inthe biodesulfurization process the pyrite content of coal willbe oxidized to water-soluble ferric sulfate and sulfuric acidaccording to (2) The dissolved ferric sulfate is removed fromthe coal in the dewatering step The coal is then washed anddried prior to combustion
Experimental investigations indicated that bacteria andfungi could be effectively used to remove iron and silicafrom clays sands and bauxite ores [15 72 73] Successfulcommercialization of bauxite biobeneficiation was proposed[74] Biological removal of calcium and iron from a low-grade bauxite ore was discussed with respect to Bacillus
polymyxa Growth conditions and probable mechanisms inthe biological removal of calcium and iron from the bauxiteore were outlined by Anand et al [75] From the reportedresults changes in the pHof the leachmedium correlatedwellwith the calcium dissolutionThe presence of bacteria lowersthe pH and hence facilitates calcium dissolution
Iron ores generally contain alumina silica sulfur andphosphorous as the main gangue minerals These impuritieshave adverse effects on reducibility of iron oxides coke rateconsumption and blast furnace operation and productivityfor steel making Various studies have examined the useof the heterotrophic bacteria and fungi for removal ofalumina and silica from iron ores for improving the ironcontent of the concerned ore The iron ore beneficiationwas carried out by secondary metabolites produced by theseheterotrophic microorganisms [76 77] It has been reportedthat in situ leaching of an iron ore with fungal strains suchasAspergillus fumigatus Penicillium citrinum andAspergillusflavus resulted in 7 6 and 17 removal of aluminaand 8 4 and 16 removal of silica respectively Bacil-lus polymyxa Bacillus sphaericus and Pseudomonas putidaensured silica removal percentage of 106 53 and 20respectively Aspergillus flavus and Pseudomonas putida weremost efficient among all the bacterial and fungal strains usedensuring an increase in iron content of about 3 at the end of10 days leaching [78]
Ronini [79] reported that heterotrophic organisms canbe used to leach out the alumina and silica from the slimesgenerated by Tata Iron and Steel Company in India Heinvestigated the feasibility of Bacillus to leach the slimesand increase its iron content At pH 7 leaching for 5 daysat inoculums size of 20 Ronini obtained an optimumrecovery of 79 of the iron content in the slimes
5 Biosurface Modification
Adhesion of microorganisms to mineral surfaces is knownto alter the hydrophobicity of minerals It has been demon-strated that Acidithiobacillus ferrooxidans is suitable for therapid treatment of sulfide ores where leaching is not thedesired outcome Surface treatment of sulfide minerals withbacterial solution is shown to influence their superficialchemical properties thus altering their response in processessuch as froth flotation andor selective flocculation Thistechnique is being evaluated as a method of enhancing thephysical separation of pyrite from coal in fine coal flotationcircuits and is suggested as an alternative method to the totalleaching of pyrite from coal [80 81] In this technique thecoal pulp is conditioned with Acidithiobacillus ferrooxidansbacteria for about 30 minutes and thus renders pyrite surfaceto be hydrophilic This in turn enhances the selectiveflotation of coal from pyrite Table 1 shows typical resultsof a study concerning bacterial leaching versus bacterialconditioning followed by flotation of minus 28 mesh coalcontaining 288 pyritic sulfur [69]
In a study concerning the effect of bacterial conditioningof sphalerite and galena it was found that the floatabilityof galena decreased markedly (Figure 4) due to oxidation of
6 Journal of Mining
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
[1] Q P Granger ldquoBacterial leaching of mineralsrdquo CollieryGuardian Redhill vol 232 no 6 pp 212ndash214 1984
[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Table 1 Flotation bacteria leaching and combinations of bacterial conditioning and flotation of minus28 mesh coal containing 288 pyriticsulfur [69]lowast
ProcessCoal product specifications
Coal yield Pyritic sulfur
Pyritic sulfurremoval Ash Calorific
value kcalkgRegular conditioning and one-stage flotation 7374 129 6676 225 mdashBacterial leaching (10 days leaching) 100 142 566 3047 5260Bacterial conditioning (4 hours) and one stage flotation 780 0825 7763 185 6361Bacterial conditioning (4 hours) and 3-stage flotation 3436 068 9178 1203 mdashlowast
pH = 20 for flotation conditioning and for bacterial leaching and pH = 9 for all flotation stages
Initial cell concentration (cellmL)
Flot
atio
n re
cove
ry (
)
0
20
40
60
80
100
Galena PbSSphalerite ZnS
1eminus2
1eminus1
1e+0
1e+1
1e+2
1e+3
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
1e+10
Figure 4 Effect of initial cell concentration during bacterialconditioning on the floatability of galena and sphalerite [82]
sulfur to insoluble lead sulfate species on the surface [82 83]In the case of sphalerite (Figure 4) such effects were notobserved since the zinc sulfate formed is solubleThe reportedresults have significant implications to the selective flotationof lead-zinc sulfides
Recently a copper concentrate assaying 2223 Cu wasobtained through bacterial conditioning followed by flota-tion whereas a copper concentrate assaying 1820 Cu wasobtained in conventional flotation [84] This means thatthe copper grade of the flotation concentrate subjected tobacterial conditioning is higher by 22 than the concentrateobtained by conventional flotation without bacterial con-ditioning Acidithiobacillus ferrooxidans can affect mineralsurfaces by direct (intimate) contact or indirect (no intimate)contact mechanisms In both cases the bacteria eliminatethe occurrence of oxidized sulfur which (the sulfur) hashydrophobic properties and induces higher floatability tominerals so that hydrophobicity of pyrite is decreased [85]
According to the mechanisms explained above bacteriaare more effective on the pyrite surface than on the chalcopy-rite surface This is because at low pH values the oxidationof pyrite is more pronounced than that of chalcopyrite In
addition Acidithiobacillus ferrooxidans increases the oxida-tion rate of pyrite gradually Under these conditions theformation of jarosite layer takes place at lower pH valuesOnce jarosite is formed it precipitates on mineral surfacesand decreases the effectiveness of reagentmineral surfaceinteraction in flotation resulting in pyrite depression Fromthe above discussion it could be conclude thatAcidithiobacil-lus ferrooxidans appears to play a dual role promoting flota-tion under certain conditions while enhancing depressionof minerals under some other conditions Promotion offloatability of sulphide minerals in the presence of this typeof bacteria could be understood in the light of elementalsulphur formation onmineral surfaces through biooxidationBacterial interaction for prolonged periods of time leadsto reoxidation of the sulphur to sulphoxy compounds andultimately to sulphate Gradual build-up of such oxidizedlayers on mineral surfaces would impede flotation
6 Bacteria Activities in Flotationand Flocculation
There is high evidence that microorganisms could be usedto flocculate finely divided minerals andor other solidssuspensions [86 87] It was found that the bacteriumMycobacterium phlei has a demonstrated potential to beused for the flotation of hematite Figure 5 The decrease inflotation recovery at high bacteria concentration (gt20 ppm)was due to the formation of hematite aggregates too large tobe levitated by air bubbles [88] This same type of bacteriumproved to be successful in flocculating a variety of finelydivided minerals such as hematite (Figure 6) phosphateslimes (Figure 7) and coal (Figure 8) [86 87 89] Figure 6shows that the concentration of bacteria cells affects theextent of flocculationThis type of bacteriumMycobacteriumPhlei possesses highly negative features on highly hydropho-bic surfaces It was suggested that these properties arisein large part from its fatty acid surface [88] Because ofthese characteristics the organism which is readily adsorbedonto the hydrophilic surface of the mineral may have anegative neutral or low positive charge It also adheres tomany hydrophobic minerals due to the created adhesion(attraction) energy of hydrophobic interactions [90]
Interaction between Paenibacillus polymyxa with min-erals such as hematite corundum calcite kaolinite and
Journal of Mining 7
Concentration of Mycobacterium phlei (ppm)
Flot
atio
n re
cove
ry (
)
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Material hematiteSize minus20microns
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Figure 5 Hallimond tube flotation recovery of hematite as a func-tion of Mycobacterium phlei concentration (operating conditionspH = 5 1 gram of hematite 10min flotation) [88]
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
02
04
06
08
10
12
14
16
No Mycobacterium phlei
702 g M Mycobacterium phlei
0 2 4 6 8 10 12 14 16
640 g M Mycobacterium phlei
Figure 6 Flocculation of hematite slimes with and withoutMycobacterium phlei as a function of time Samples were collectedat 4 cm from the bottom surface of a 1000mL graduated cylinder[88]
quartz resulted in significant surfacemdashchemical changesQuartz and kaolinite were renderedmore hydrophobic whilehematite calcite and corundum became more hydrophilicafter biotreatment Through biotreatment of the above min-erals it was possible to selectively separate silica and aluminafrom ironminerals either by flotation or selective flocculation[91]
Utilization of microorganisms and associated extracellu-lar metabolic products in selective flotation and flocculationhas been recently reported [91ndash93] Patra and Natarajan[94] showed that different protein fractions derived fromPaenibacillus polymyxa exhibited varying surface adsorptioncapacity towardsminerals such as quartz pyrite chalcopyritegalena and sphalerite Proper use of fractionated proteingroups rendered pyrite and chalcopyrite hydrophilic while
Flocculation time (minutes)
Solid
s con
cent
ratio
n (
)
00
05
10
15
20
25
0 5 10 15 20 25 30 35
No Mycobacterium phlei585 g M Mycobacterium phlei
Figure 7 Flocculation of a 14 suspension of Four Corners(Florida) phosphate slime with the addition of two different con-centrations ofMycobacterium phlei [88]
Settling time (minutes)
Am
ount
settl
ed (
)
20
40
60
80
100
Mycobacterium phlei 200 ppmPEO 100 ppmPAM 100 ppm
Illinois 6 coalpH 35
0 100 200 300 400 500
Figure 8 Amount of coal settled as a function of time in the pres-ence of different flocculants Mycobacterium phlei Polyacrylamideflocculent (PAM) and Polyethylene Oxide flocculent (PEO) [89]
sphalerite galena and quartz exhibited enhanced surfacehydrophobicity after bio-treatment Similarly prior proteintreatment resulted in selective flocculation of pyrite andchalcopyrite together while galena sphalerite and quartzwere effectively dispersed These studies demonstrated thatbacterial proteins could effectively replace the conventionalamine and xanthate types of collectors which are toxic andexpensive
Due to the adherence of bacteria to mineral surfacessome strains can be used to modify mineral surfaces toaid selective recovery of valuable minerals in flotation orflocculation processes Some bacteria can selectively depress
8 Journal of Mining
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Table 2 Flotation recovery of minerals treated individually in presence and in absence of collector without cells or extract and afterinteraction with mineral-grown cells and cell-free extract [70]
Mineral (minus105 + 75microns)
Flotation recovery percentWithout cells or cell-free extract With cells or cell-free extract
Without collector With collector After interactionwith cells (1 h)
the flotation of onemineral compared to anotherThe depres-sion can either result from bacteria oxidizing or otherwisemodifying the surface of themineral to render it less floatableor prevent the subsequent adsorption of a flotation collectorDue to the adherence of bacteria to mineral surfaces somestrains can be used tomodifymineral surfaces to aid selectiverecovery of valuable minerals in flotation or flocculationprocesses Some bacteria can selectively depress the flotationof onemineral compared to othersThe depression can eitherresult from bacteria oxidizing or otherwise modifying thesurface of the mineral to render it less floatable or frombacteria adhering to the mineral preventing the subsequentadsorption of a flotation collector
Adhesion of Bacillus subtilis and Mycobacterium phleionto dolomite and apatite was studied by sorption measure-ments and scanning electron microscopy [95] It was foundthat both Bacillus subtilis and Mycobacterium phlei adhereonto dolomite surface more readily than onto apatite surfaceat acidic and near neutral pH values At more basic pHvalues Bacillus subtilis adheres more readily onto the mineralsurface and remains a better depressant for dolomite than forapatite However Mycobacterium phlei at basic pH valuesadsorbs more onto apatite than onto dolomite acting as aweaker depressant for dolomite and a stronger depressantfor apatite compared with Bacillus subtilis The differencesin adsorption characteristics were attributed to differences insurface properties of the two bacteria species and of the twomineralsThenet result of the study indicated that while bothbacteria function as depressants in anionic collector flotationof dolomitic phosphate ores Bacillus subtilis functions as thestronger depressant especially for dolomite [95]
In amore recent investigation Sarvamangala andNatara-jan [70] showed that the microorganism Bacillus subtilis andthe extracellular protein have been utilized for the separationof hematite from the other oxide minerals It is evidentfrom the obtained results that the presence of bacterial cellsand cell-free extract promoted the flocculation and settlingof hematite whereas in the case of quartz corundum andcalcite the interaction with bacterial cells and cell-free extractfavored more dispersion of the minerals Flotation behav-ior of hematite-quartz and calcite-corundum systems wasstudied before and after interaction with bacterial cell-freeextract and bacterial cells The obtained results Table 2 [70]indicate that interaction with Bacillus subtilis confers surfacehydrophobicity on quartz calcite and corundumwhile simi-lar biotreatment renders hematite more hydrophilic Relative
hydrophobicity or hydrophilicity of mineral-grown bacterialcells depends on the ratio of proteins and polysaccharidespresent on the cell walls Bacterial cell population and theirinteraction period with minerals as well as mineral surfacecoverage through bacterial adhesion control the mineral sur-face hydrophobicity regarding flotation andor flocculationThese studies open a wide venue for possible developmentsof biotechnological applications for environmentally safemineral beneficiation operations However more detailedinvestigations need to be carried out to make a clear insightinto the control of bacterial cell wall composition Also themechanisms of bacteria-mineral surfaces interactions shouldbe clearly highlighted
In 2011 Reyes-Bozo et al [96] studied the effect ofbiosolids (obtained from waste water treatment plant Chile)on hydrophobic properties of sulfide ores on a laboratoryscale The principal components of biosolids are humicsubstances mainly humic acid and phosphorus compoundsThe interaction between the mineral surface and the func-tional groups found in biosolids as a collector for cop-per sulfide ores was investigated through zeta potentialmeasurements FT-IR analysis and film flotation tests Theresults showed that biosolids change the hydrophobicity ofthe sulfide minerals by adsorbing onto the surface Biosolidsshow greater affinity for pyrite while commercial humic acidshows similar behavior to industrial collectors Thereforeboth biosolids and humic acids can change the hydrophobicproperties of sulfide ores and can be used as collectors infroth flotation processes Thus the use of biosolids is feasiblein a preliminary flotation stage for removing pyrite or in therougher stage of froth flotation to separate important sulfideminerals from the gangue
7 Bioremediation
In addition to being useful in the mineral beneficiation arearecent developments in biotechnology have given promisesthat biotechnology may also provide means for bioremedi-ation of environmental problems generated in the mineralmetallurgical and chemical industries For example in theflotation of wastes an investigation concerning the biodegra-dation of thiol collectors by the bacterium Pseudomonas flu-orescentswas reported [88] In this study it was indicated thata residual xanthate concentration of 012mgL in the wastew-ater from a lead concentrator was completely destroyed in
Journal of Mining 9
Degradation time (hours)
Buty
l xan
that
e con
cent
ratio
n (
)
20
40
60
80
100
With bacteriaWithout bacteria
0 10 20 30 40 50
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Figure 9 Influence of Pseudomonas fluorescens on the degradationof butyl xanthate [88]
fiveminutes after treatmentwith a bacterial suspension Butylxanthate destruction by Pseudomonas fluorescents has alsobeen investigated and typical results are shown in Figure 9 Inthis figure it is clear that the concentration of butyl xanthatewas decreased by about 20 of its original concentration in40 minutes in the presence of bacteria [88]
Concerning polluted soil bioremediation there is anexcellent review in which sources of soil pollution biore-mediation strategies and the direction of further researchhave been highlighted [97] It is known that under specifiedconditions certainmicroorganisms or enzymes derived frommicroorganisms are able to break down cyanides and hencethere is a potential for using these organisms in biore-mediation cyanide wastes discharged from precious metalhydrometallurgical plants [98] Noel et al [24] cultivatedbacterial strains from solids previously exposed to cyanidesolution which tolerate 300 ppm sodium cyanide underanaerobic conditions In the selected soil samples thesebacteria reduced the level of cyanide from approximately300 ppm to essentially zero in about 50 days under anaerobicconditions Typical results of these experiments are shown inFigure 10 In this study various nutrient media were inves-tigated and the maximal growth of bacteria was establishedat Medium A which was composed of 10 gL K
2HPO4
02 gL MgSO4sdot7H2O 2 gL FeSO
4 2 gL MnCl
12sdot4H2O and
0001 gL Na2MoO4sdot2H2O
Maniatis et al [99] demonstrated that biological destruc-tion of cyanide inminingwater was effective in the laboratoryand in the field In this study the cyanide was put in acomplex form with selenium by aerobic reactor which wasrun continuously for six days to remove cyanide and thenrun one more time through a series of anaerobic reactors toremove selenium The aerobic reactor removed 95 of thecyanide content in the first 24 hours with another 3 removalover the next five days No nutrient addition was required
Biosorption laboratory research activities are expected toreach industrial application for the detoxication of industrialwaste water [100 101] Considerable interest exists in the
Contact time (days)
Sodi
um cy
anid
e con
cent
ratio
n (p
pm)
0
50
100
150
200
250
300
Heap solids WHeap solids X
Tailing solids YTailing solids Z
00 200 400 600 800 1000 1200 1400
Figure 10 Variation of sodium cyanide concentration as a functionof inoculum solids and contact time in the presence of nutrientMedium A at locations W X Y and Z [24]
application of biosorption to the removal of a number ofenvironmental contaminants including toxic heavy metalssuch as chromium [102] selenium [103] and cadmium aswell as radionuclides such as uranium [104]
Chaalal et al [105] reported the use of thermophilicbacteria (belongs to Bacillus family) for the removal of leadcompounds contaminating the drinkingwaterThese bacteriawere isolated and used in a reactor coupled with a membranesystem The bacteria the stirrer and the membrane housedin the reactor were arranged in a distinctive way to form thenovel biostabilization process proposed in this researchTheyclaimed that the proposed technique could be used at low costand with great confidence in purifying drinking water Thesystem was found to be adequate for remediating drinkingwater having lead concentration up to 40 ppm At the endof the operation the lead concentration reaches the levelallowed by the world health organization regulations
Bioremediation of waters contaminated with crude oiland toxic heavy metals was also achieved by the processof microbial dissimilatory sulfate reduction and biosorption[106]
8 Summary
The present paper highlights a number of new possibilitiesfor industrial application of biotechnological principles forthe extraction of metal values from inorganic resources Thepresent industrial interest in bioleaching methods is moti-vated by the fact that these processes can produce metal val-ues from low-grade resources for approximately one-third toone-half of the cost of the conventional smelting techniqueswithout polluting the environment Furthermore selectiveimplementation of living systems can offer opportunitiesfor reduced labor increased productivity and technologicaladvances In fact bacteria technologies have been applied ona commercial scale for the recovery of copper and uraniumfrom low-grade ores and industrial wastes
10 Journal of Mining
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
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[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
Bacterial activities have been recently introduced in themineral processing technology They have been used inmineral surface modification flocculation and collectors inflotation In these areas parameter optimization and processcontrol are required for efficient application In additionhigher levels for scaling up the operations must be encour-aged in all biomineral processing systems for industrial pur-pose Also detailed understanding of the biosurfactant rolein modifying the mineral surfaces and exploring bioflotationapplications is currently lacking
Bacterial leaching is a new development in hydrometal-lurgy of metal sulphides Greater understanding of the basicmechanisms of bacterial mineral leaching is still requiredwhich hinders the controlled utilization of this technologyPublished information relating to the oxidation of variousminerals differs greatly and sometimes contradicts eachother with respect to the acting mechanisms the rate andamount of oxidation took place under specific conditionsThis would indicate that considerable information is stillnecessary to determine the most efficient types of bacteriaproper operating conditions manner in which they shouldbe cultivated and the mechanisms with which they attach tothe minerals to be leached
Microbiological leaching is influenced by a number ofparameters and it functions best if carried out at optimumleaching conditions Intensive aeration is required to assuremaximum oxygen mass transfer into the leach solution Thesmallest particle size of the solid sulphide substratewill assurethe highest rate and yield of metal extraction The Eh mustbe kept below 500mV in order to avoid jarosite type andbasic ferric hydroxide precipitation on the surface of the solidsubstrate In all leaching techniques wherever possible acyclic leaching process should be applied
It seems that new trends are evolving as the knowledgeof bacterial activity relative to industrial applications isfurthered Biohydrometallurgical applications are multidis-ciplinary in nature and should be dealt with at optimumconditions for optimal effects Bioremediated processes areof high importance especially in copper uranium andpreciousmetals industries However their applicability in theremediation of contaminated soils and industrial aqueouseffluents is hampered by lack of sufficient information
References
[1] Q P Granger ldquoBacterial leaching of mineralsrdquo CollieryGuardian Redhill vol 232 no 6 pp 212ndash214 1984
[2] F D Pooley ldquoThe role of biohydrometallurgy in mineralprocessingrdquo in Innovations in Mineral and Coal ProcessingS Atak G Onal and M S Celik Eds p 435 BalkemaRotterdam The Netherlands 1998
[3] A S S Seifelnassr and A Z M Abouzeid ldquoNew trends inmineral processing exploitation of bacterial activitiesrdquo TheJournal of Mineral Processing vol 3 no 4 p 17 2000
[4] A W Hudson and G D Vanasdale ldquoHeap leaching at BisbeeArizonardquo Transactions of the Society of Mining vol 64 p 1371923
[5] A Bruynesteyn and R P Hack ldquoThe biotank leach processfor the treatment of refractory goldsilver concentratesrdquo in
Microbiological Effects onMetallurgical Processes J A Clum andL A Haas Eds pp 121ndash128 Tms-AIME New York NY USA1985
[6] J Murpby E Ristenberg D Marek R Moble B Beck andD Skidmore ldquoMicrobial dessulphurization of coal by Ther-mophilic bacteriardquo in Microbiological Effects on MetallurgicalProcesses J A ClumandLAHaas Eds pp 99ndash110 TMS 1985
[7] J E Moss and J E Anderson ldquoThe effect of environment onbacterial leaching ratesrdquoProceedings of the Australasian Instituteof Mining and Metallurgy vol 225 p 15 1968
[8] MMakintosh ldquoNitrogen fixation by T ferrooxidansrdquo Journal ofGeneral Microbiology vol 70 p 66 1971
[9] A E Torma ldquoThe role of Thiobacillus ferrooxidans inhydrometallurgical processesrdquo Advances in Biochemical Engi-neering vol 6 pp 1ndash37 1977
[10] M P Silverman ldquoMechanism of bacterial pyrite oxidationrdquoJournal of Bacteriology vol 94 no 4 pp 1046ndash1051 1967
[11] M P Silverman and D G Lundgren ldquoStudies on thechemoautotrophic iron bacterium ferroobacillus ferrooxidansan improved medium and harvesting procedure for securinghigh cell yieldsrdquo Journal of Bacteriology vol 77 pp 642ndash6471959
[12] F D Pooley ldquoMineral leaching with bacteriardquo in EnvironmentalBiotechnology F F Christopher and D A John Eds pp 114ndash134 Ellis Horwood John Wiley and Sons New York NY USA1987
[13] C L Brierley and J A Brierley ldquoA chemoautotrophic andthermophilic microorganism isolated from an acid hot springrdquoCanadian Journal of Microbiology vol 19 no 2 pp 183ndash1881973
[14] G Millonig M De Rosa A Gambacorta and J D BursquolockldquoUltrastructure of an extremely thermophilic acidophilic microorganismrdquo Journal of General Microbiology vol 86 no 1 pp165ndash173 1975
[15] V I Groudeva S N Grouder and M I markov ldquoA com-parison between Thermophilic bacterial with respect to theirability to leach sulfide mineralsrdquo in Fundamental and AppliedBiohydrometallurgy R W Lawrence R M Brauion and H GEbener Eds p 484 Elsevier 1986
[16] A E Torma ldquoBiohydrometallurgy as an emerging technologyrdquoin Proceedings of the Biotechnology and Bioengineering Sympo-sium No 16 p 49 1986
[17] M L Free T Oolman S Nagpal and D A BahlstromldquoBioleaching of sulfide oresmdashdistinguishing between indirectand direct mechanismsrdquo in Mineral Bioprocessing R W Smithand M A Misra Eds p 485 TMS 1991
[18] Y R K Mirajkar K A Natarajan and P SomasundaranldquoGrowth and attachment of Thiobacillus ferrooxidans duringsulfide mineral leachingrdquo International Journal of MineralProcessing vol 50 no 3 pp 203ndash210 1997
[19] G S Hansford ldquoStudies on the mechanisms and kinetics ofbioleachingrdquo Fizykochemiczne Problemy Mrtalugil vol 32 pp281ndash291 1998
[20] D Mishra and Y Rhee ldquoCurrent research trends of microbi-ological leaching for metal recovery from industrial wastesrdquoin Current Research Technology Education Topics in AppliedMicrobiology and Microbial Biotechnology A Mendez-VilasEd FORMATEX 2010
[21] A R Colmer andM E Hinkle ldquoThe role of microorganisms inacid mine drainage a preliminary reportrdquo Science vol 106 no2751 pp 253ndash256 1947
Journal of Mining 11
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
[22] W R Ruzzel and P C Trussel ldquoIsolation and properities of aniron oxidizing Thiobacillusrdquo Journal of Bacteriology vol 85 p595 1963
[23] K A Natarajan and I Iwasaki ldquoMicrobemineral interactionin leaching of complex sulfidesrdquo in Microbiological Effects onMetallurgical Processes S A Clum and L A Hass Eds p 113Tms-AIME New York NY USA 1985
[24] D M Noel M C Fuerstenau and J L Hendrix ldquoDegradationof cyanide utilizing facultative anaerobic bacteriardquo in MineralBioprocessing R W Smith and M Misra Eds pp 355ndash366TMS 1991
[25] W E Ruzzel ldquoBacterial leaching of metallic sulfidesrdquo CanadianInstitute of Mining vol 55 p 190 1962
[26] N Lazaroff ldquoSulfate requirement for iron oxidation to enhancegold and silver recovery from pyritc ores and concentratesrdquoCIM Bulletin vol 85 p 78 1963
[27] A H Tuovimen and D P Kelly ldquoStudies on the growth ofThiobacillus ferrooxidansrdquo Archives of Microbiology vol 88 p285 1973
[28] I J Corrans B Harris and B J Ralph ldquoBacterial leaching anintroduction to its application and theory and a study on itsmechanisms of operationrdquo Journal of the South African Instituteof Mining and Metallurgy vol 72 p 221 1972
[29] A Pinches ldquoBacterial leaching of an arsenic-bearing sulfideconcentraterdquo in Leaching and Reduction in Hydromrtallurgy AR Burkin Ed p 28 IMM London UK 1975
[30] H Sakaguchi and M Silver ldquoMicrobiological leaching of achalcopyrite concentrate byThiobacillus ferrooxidansrdquoBiotech-nology and Bioengineering vol 18 no 8 pp 1091ndash1101 1976
[31] A E Torma C CWalden andRM Branion ldquoMicrobiologicalleaching of a zinc sulfide concentraterdquo Biotechnology andBioengineering vol 12 no 4 pp 501ndash517 1970
[32] C L Brierley ldquoBacterial leachingrdquo CRC Critical Reviews inMicrobiology vol 6 no 3 pp 207ndash206 1978
[33] R L Braun and R G Mallon ldquoCombined leach-circulationcalculation for predicting in-situ copper leaching of primarysulfide orerdquo Transactions of the Society of Mining EngineersAIME vol 258 no 2 pp 103ndash110 1975
[34] P R Norris L Parrott and R M Marsh ldquoModerately Ther-mophilic mineral-oxidizing bacteriardquo in Proceedings of theBiotechnology and Bioengineering Symposium No 16 H LEhrlich and D S Holmes Eds pp 253ndash363 John Wiley andSons 1986
[35] H Kandemnir ldquoFate of sulfide Sulfur bacterial oxidation ofsulfide mineralsrdquo in Microbiological Effects on MetallurgicalProcesses J A Clum and L A Haas Eds p 51 TMS 1985
[36] M Elzeky and Y A Attia ldquoEffect of bacterial adaptationon kinetics and mechanisms of bioleaching ferrous sulfidesrdquoChemical Engineering Journal and the Biochemical EngineeringJournal vol 56 no 2 pp B115ndashB124 1995
[37] E Peters ldquoThermodynamic and kinetic factors in the leachingin sulfide minerals from ore deposits and dumpsrdquo SME ShortCourse in Bio Extractive Mining SMEAIME 1970
[38] A Bruynesteyn and J R Copper ldquoLeaching of Canadian ore intest depositsrdquo in Proceedings of the Solution Mining SymposiumF F Aplon and W A Mchinezy Eds p 268 1974
[39] A A S SeifelnassrBacterial aided percolation leaching of coppersulfide ores [PhD thesis] University ofWales Cardiff UK 1988
[40] A A S Seifelnassr and F D Pooley ldquoBiologically assisted ferricion leaching of refractory copper sulfide orerdquo in Proceedings ofthe V111 International Mineral Processing Symposium AntalyaTurkey October 2000
[41] J A Brierley and C L Brierley ldquoMicrobial leaching of cop-per at ambient and elevated temperaturesrdquo in MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomenena L E Murr A E Torma and J A Brierley Edspp 477ndash489 Academic Press London UK 1978
[42] L E Murr A E Torma and J A Brieley MetallurgicalApplications of Bacterial Leaching and Related MicrobiologicalPhenomena Academic Press New York NY USA 1978
[43] H M Tsuchiya ldquoMicrobial leaching of Cu-Ni sulfide concen-traterdquo in Metallurgical Application of Bacterial Leaching andRelatedMicrobiological Phenonena L EMurr A E Torma andJ A Brierley Eds pp 365ndash372 Academic Press London UK1978
[44] M Gericke A Pinches and J V Van Rooyen ldquoBioleachingof a chalcopyrite concentrate using an extremely thermophilicculturerdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 243ndash255 2001
[45] A Sissing and S T L Harrison ldquoThermophilic mineralbioleaching performance a compromise between maximiz-ing mineral loading and maximizing microbial growth andactivityrdquo Journal of The South African Institute of Mining andMetallurgy vol 103 no 2 pp 139ndash142 2003
[46] J Vilcaez K Suto and C Inoue ldquoBioleaching of chalcopyritewith thermophiles temperature-pH-ORP dependencerdquo Inter-national Journal ofMineral Processing vol 88 no 1-2 pp 37ndash442008
[47] J-L Xia Y Yang H He et al ldquoInvestigation of the sulfur spe-ciation during chalcopyrite leaching by moderate thermophileSulfobacillus thermosulfidooxidansrdquo International Journal ofMineral Processing vol 94 no 1-2 pp 52ndash57 2010
[48] A Behrad Vakylabad ldquoA comparison of bioleaching abilityof mesophilic and moderately thermophilic culture on copperbioleaching from flotation concentrate and smelter dustrdquo Inter-national Journal of Mineral Processing vol 101 no 1ndash4 pp 94ndash99 2011
[49] W A Gow and G M Ritcey ldquoTreatment of canadian uraniumoresrdquo Canadian Mining and Metallurgical Bulletin vol 62 no692 pp 1330ndash1339 1969
[50] R Guay A E Torma andM Silver ldquoFerrous ion oxidation anduranium solubilization from a lowgrade ore by ldquoThiobacillusferrooxidansrdquordquoAnnales deMicrobiologie vol 126 no 2 pp 209ndash219 1975
[51] A E Torma C C Walden D W Duncan and M R BrauionldquoEffect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concenytatesrdquo Biotechnologyand Bioengineering vol 14 p 777 1992
[52] A E Torma and K N Subramanian ldquoSelective bacterialleaching of a lead sulphide concentraterdquo International Journalof Mineral Processing vol 1 no 2 pp 125ndash134 1974
[53] Y Attia L Tchfield and L Vaaler ldquoApplication of bio-technology in the recovery of goldrdquo in Microbiological Effectson Metallurgical Processes J A Clum and L A Haas Eds pp11ndash20 Tms-AIME New York NY USA 1985
[54] E Livesey P Norman and R Livesey ldquoGold recovery fromarsenopyritepyrite ore by bacterial leaching and cyanidationrdquoin Recent Progress in Biohydrometallurgy pp 627ndash641 Asso-cizione Mineraria Sarda Iglesias Italy 1983
[55] E Livesey ldquoBacterial leaching of gold uranium pyrite-bearing-compacted mine tailing slimesrdquo in Fundamental and AppliedBiouhydro Metallurgy R W Lawrnce R M Braniou and HG Ebmer Eds pp 89ndash97 Elsevier 1986
12 Journal of Mining
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
[56] H L Ehrlich ldquoBacterial leaching of silver from a silvercontaining mixed Sulfide ore by a continuous processrdquo inFundamental and Applied Biohydrometallurgy R W LawrenceR M Braniou and H G Ebmer Eds pp 77ndash88 Elsevier 1986
[57] R W Lawrence and A Bruynesteyn ldquoBiological pre-oxidationto enhance gold and silver recovery from refractory pyritic oresand concentratesrdquo CIM Bulletin vol 76 no 857 pp 107ndash1101983
[58] D S Holmes and K A Debus ldquoOpportunities for biologicalmetal recoveryrdquo in Mineral Bioprocessing R W Smith and MMisra Eds pp 57ndash80 Tms-AIME 1991
[59] C C Towskey I S Ross and A S Atkins ldquoBiorecoveryof metallic residues from various industrial effluents usingfilamentous Fungirdquo in Fundamental and Applied Biohydromr-tallurgy R W Lawrence R M R Branion and H G EbnerEds pp 279ndash290 Elsevier 1986
[60] A E Torma ldquoMineral bioprocessingrdquo in BIOMIN 93 pp 1ndash10 Australian Mineral Foundation Glenside South Australia1993
[61] S N Groder I I Spasova and I M Ivauov ldquoMicrobialleaching of a gold-bearing pyrite Concentraterdquo in ChangingScopes inMineral Processing M Kemal V Arslan A Askar andM Canbazolgu Eds pp 583ndash586 Balkema Rotterdam TheNetherlands 1996
[62] A Ozkan S Aydogan and U Akdermir ldquoBacterial leachingas a pre-treatment step for gold recovery from refractoryoresrdquo in Proceedings of the Physicochemical problems of MineralProcessing vol 32 pp 173ndash182 Wroclaw Poland 1998
[63] Z Sadowski T Farbiszewska and J Farbiszewka-Bajar ldquoTherole of microorganisms in pretreatment of gold-bearing oresrdquoin Proceedings of the Physicochemical Problems of mineralProcessing 35th Symposium pp 151ndash165 Wroclaw Poland 1998
[64] S Ubaldini F Veglio L Toro and C Abbruzzese ldquoBiooxi-dation of arsenopyrite to improve gold cyanidation study ofsome parameters and comparison with grindingrdquo InternationalJournal of Mineral Processing vol 52 no 1 pp 65ndash80 1997
[65] D Karamanev A Margaritis and N Chong ldquoThe applicationof ore immobilization to the bioleaching of refractory goldconcentraterdquo International Journal ofMineral Processing vol 62no 1ndash4 pp 231ndash241 2001
[66] B VMihaylov and J L Hendrix ldquoBiooxidation of a sulfide goldore in columnsrdquo in Mineral Bioprocessing R W Smith and MMisra Eds p 163 TMS-AIME 1991
[67] B A Paponetti S Ubaldini C Abbruzzese and L ToraldquoBiometallurgy for the recovery of gold from arsenopyriteOresrdquo inMineral Bioprocessing RW Smith andMMisra Edsp 179 TMS 1991
[68] P Miller and A Brown ldquoBacterial oxidation of refractorygold concentratesrdquo in Advances in Gold Ore Processing M AAdams Ed Elsevier 2005
[69] M Z Dogan and M S Cleik ldquoLatest developments in coaldesulphurization by flotation and microbial beneficiationrdquo inProceedings of the 3rd Mining Petroleum and MetallurgicalConference vol 1 pp 2ndash4 Faculty of Engineering CairoUniversity February 1992
[70] H Sarvamangala and K A Natarajan ldquoMicrobially inducedflotation of alumina silicacalcite from haematiterdquo Interna-tional Journal of Mineral Processing vol 99 no 1ndash4 pp 70ndash772011
[71] T Farbiszewska ldquoIntensity of the bacterial leaching processfrom mining brown coal wasterdquo Physico-Chemical Problems ofMineral Processing vol 22 pp 145ndash159 1990
[72] G I Karavviko Z A Avakyan L V Ogurtsova and O FSafanova ldquoMicrobiological processing of bauxiterdquo in Proceed-ings of International Symposium onBiohydrometallurgy J SalleyRG LMcGready andP LWichlacz Eds pp 93ndash102 CanmetOttawa Canada 1989
[73] L V Ogurtsova G I Karavaiko Z A Avakyan and A AKorenevsii ldquoActivity of various microorganisms in extractingelements frombauxiterdquoMicrobiology vol 58 pp 774ndash780 1990
[74] S S Vasan J M Modak and K A Natarajan ldquoSome recentadvances in the bioprocessing of bauxiterdquo International Journalof Mineral Processing vol 62 no 1ndash4 pp 173ndash186 2001
[75] P Anand J M Modak and K A Natarajan ldquoBiobeneficiationof bauxite using Bacillus polymyxa calcium and iron removalrdquoInternational Journal of Mineral Processing vol 48 no 1-2 pp51ndash60 1996
[76] C Cameselle M T Ricart M J Nunez and J M Lema ldquoIronremoval from kaolin Comparison between ldquoin siturdquo and ldquotwo-stagerdquo bioleaching processesrdquoHydrometallurgy vol 68 no 1ndash3pp 97ndash105 2003
[77] H L Ehrlich ldquoPast present and future of biohydrometallurgyrdquoHydrometallurgy vol 59 no 2-3 pp 127ndash134 2001
[78] S Shitarashmi Biomineral processing a suitable approach [MSthesis] National Institute of Technology Rourkela India 2009
[79] NRoniniFeasibility study on themicrobial separation of iron oreslime [MS thesis] National Institute of Technology RourkelaIndia 2011
[80] G F Andrews P R Dugan and C J Stevens ldquoCombiningphysical and bacterial treatment for removing pyritic sulfurfrom coalrdquo inProcessing andUtilization ofHigh Sulphur Coal IVP R Dugan D R Quigley and Y A Attia Eds p 515 Elsevier1991
[81] Y A Attia M Elzekey F Bavariam and L S Fan ldquoCleaningand desulphurization of high sulfur coal by selective floccu-lation and bioleaching in draft tube fluidized bed reactorrdquo inProceedings of the 3rdMining PetroleumMetallurgyConferencevol 1 pp 2ndash4 Faculty of Engineering Cairo University Febru-ary 1992
[82] M K Yelloji K A Natarajan and P Somasundran ldquoEffect ofbacterial conditioning of sphalerite and galena with Thiobacil-lus ferrooxidans on their floatabilityrdquo in Mineral BioprocessingR W Smith and M Misra Eds pp 105ndash120 TMS 1991
[83] K Hanumantha Rao A Javadi T Karlkvist A Patra A Vilin-ska and I V Chernyshova ldquoRevisiting sulphide mineral (Bio)processing a few priorities and directionsrdquo in Proceedings ofthe 15th Balkan Mineral Processing Congress Sozopol BulgariaJune 2013
[84] A Ekrem Yuce HMustafa Tarkan andM Zeki Dogan ldquoEffectof bacterial conditioning and the flotation of copper ore andconcentraterdquo African Journal of Biotechnology vol 5 no 5 pp448ndash452 2006
[85] L C Bryner R B Walker and R Palmer ldquoSome factorsinfluencing the biological oxidation of sulfide mineralsrdquo Trans-actions of AIME vol 238 pp 56ndash62 1967
[86] MMisra S Chen andRW Smith ldquoKerogen aggregation usinga hydrophobic bacteriumrdquo inMineral Bioprocessing RW Smithand M Misra Eds p 133 TMS-AIME 1991
[87] M Misra R W Smith and J Dubel ldquoBioflocculation of finelydividedmineralsrdquo inMineral Bioprocessing RW Smith andMMisra Eds p 91 TMS-AIME 1991
[88] R W Smith and M Misra ldquoMineral bioprocessingmdashanoverviewrdquo inMineral Bioprocessing W R Smith and M MisraEds pp 3ndash26 TMS 1991
Journal of Mining 13
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
[89] M A Raichur M Misra and R W Smith ldquoThe Potential forselective flocculation of coal from pyrite using a Hydrophicbacteriumrdquo in Mineral Processing Recent Advances and FutureTrends S PMehrotra and R Shekhar Eds pp 686ndash693 AlliedNew Delhi India 1995
[90] D A Elgillani Class Notes in Surface Chemistry Cairo Univer-sity Faculty of Engineering Department ofMining Petroleumand Metallurgical Engineering Giza Egypt 2008
[91] K A Natarajan and N Deo ldquoRole of bacterial interactionand bioreagents in iron ore flotationrdquo International Journal ofMineral Processing vol 62 no 1ndash4 pp 143ndash157 2001
[92] D Santhiya S Subramanian K A Natarajan H HanumanthaRao and K S E Forssberg ldquoBio-modulation of galena andsphalerite surfaces using Thiobacillus thiooxidansrdquo Interna-tional Journal of Mineral Processing vol 62 no 1ndash4 pp 121ndash1412001
[93] M N Chandraprabha K A Natarajan and P SomasundaranldquoSelective separation of pyrite from chalcopyrite and arsenopy-rite by biomodulation using Acidithiobacillus ferrooxidansrdquoInternational Journal of Mineral Processing vol 75 no 1-2 pp113ndash122 2005
[94] P Patra and K A Natarajan ldquoRole of mineral specific bacterialproteins in selective flocculation and flotationrdquo InternationalJournal of Mineral Processing vol 88 no 1-2 pp 53ndash58 2008
[95] X Zheng P J Arps and RW Smith ldquoAdhesion of two bacteriaonto dolomite and apatite their effect on dolomite depressionin anianic flotationrdquo International Journal of Mineral Processingvol 62 no 1ndash4 pp 159ndash172 2001
[96] L Reyes-Bozo R Herrera-Urbina M Escudey et al ldquoRole ofbiosolids on hydrophobic properties of sulfide oresrdquo Interna-tional Journal of Mineral Processing vol 100 no 3-4 pp 124ndash129 2011
[97] S Pal A K Patra S K Reza W Wildi and J Pote ldquoUseof bio-resources for bioremediation of soil pollutionrdquo NaturalResources vol 1 pp 110ndash125 2010
[98] S Copaescu G fodor G Bota L Popa and A PescaruldquoPossibilities of treatment of residual waters containing cyanideand its recovery in a cyanidation plant from regia autonomaa cupului devardquo in Changing Scopes in Mineral Processing MKemal V Arslan A Akar and M Canbozoglu Eds pp 591ndash598 Balkema Rotterdam The Netherlands 1996
[99] T Maniatis B Wahlquist and T Pickett ldquoBiological cyanidedestruction in mineral processing watersrdquo in Proceedings of theSME Annual Meeting pp 879ndash880 Denver February 2004
[100] J A Brierley C L Brierley and G M Goyalc ldquoAMT-BIOCLAM a new waste water treatment and metal recoverytechnologyrdquo in Fundamental and Applied BiohydrometallurgyR W Lawrence R M R Branion and H G Ebner Eds pp291ndash304 Elsevier 1986
[101] T Jeffers C R Ferguson and P G Bennett ldquoBiosorption ofmetal contaminants from acidic mine watersrdquo in InternationalMineral Bioprocessing R W Smith and M Misra Eds p 289TMS 1991
[102] W A Apel and C E Turick ldquoBio-remediation of hexavalentchromium by bacterial reductionrdquo inMineral Bio-Processing RSmith and M Misra Eds p 376 TMS-AIME 1991
[103] J M Barnes E B McNew J K Polman J H McCune andA E Torma ldquoSelenate reduction by pseudomonas stutzerirdquo inMineral Bioprocessing R W Smith and M Misra Eds p 367TMS-AIME 1991
[104] M L Apel J M Barnes and A E Torma ldquoBiosorption kineticsof metal removal from uranium mill tailing effluentsrdquo in Bio-Processing R Smith and M Misra Eds p 339 TMS 1991
[105] O Chaalal A Y Zekri and R Islam ldquoUptake of heavy metalsbymicroorganisms an experimental approachrdquo Energy Sourcesvol 27 no 1-2 pp 87ndash100 2005
[106] V I Groudeva S N Groudev and A S Doycheva ldquoBioreme-diation of waters contaminated with crude oil and toxic heavymetalsrdquo International Journal of Mineral Processing vol 62 no1ndash4 pp 293ndash299 2001
