24Bond, F.C., "Crushing and Grinding Calculations," BritishChemical Engineering, Vol. 6,1966, p. 578.25Celik. M.S.. "A Study of Fine Grinding of Coals in TumblingBall Mills," MS Thesis. The Pennsyvania State University. 1977.26Somasundaran. P.. and Kulkarni, R.D.. "A New StreamingPotential Apparatus and Study of Temperature Effects UsingIt." Journal of Colloid and Interface Science, Vol. 45, 1973. p.591.27Van Krevelen, D. W.. Coal, FJsevier. AmSterdam. 1961.28Schmidt. R.A.. Consumer Coal Criteria as a Guide to E$.-ploration, Miller Freeman Publications. Inc.. San Francisco.1976, p. 610.

minution, " Final Report on US Energy Research and Develop.

ment AdminiStration Contract No. EX.76.C-OI.I777. SyracuseUniversity Research Corp., Syracuse. 1976.21Datta, R.S., and Howard. P.H., "Characterization of theChemical Comminution of Coal, " Interim Report on US Energy

Research and Development AdminiStration Contract No. EX.76-C.OI-2520, Syracuse University ~ Corp.. Syra~. 1977.22Campbell, j.A.L.. "An Electrokinetic Study of Coal FrothFlotation and Flocculation." PhD Thesis, The PennsylvaniaState University, 1969.2SAustin, L.G,. and Luckie. P. T., "Methods for Determinationof Breakage Distribution Parameters," Powder Technology,Vol. 5, 1971/2. p. 215.

D. R. Nagaraj and P. SomaStlndaran

copper specificity of these chelating agents has been exploitedfor solvent extraction of copper, their potential for other ap-plications such as flotation has not been considered so far. Thepresent study, to the best of our knowledge, is the first attemptto investigate this application of LIX reagents as collectors.

The results obtained for microflotation of chrysocolla andcuprite using LIX65N, and the Batch Laboratory cell flotationof synthetic mixtures of copper oxides and sulfides with quamusing LIX65N are presented here. The flotation tests demon-strated the ability of the LIX reagents to function as effectivecollectors for copper minerals. Furthermore, the difference inthe collector property between the isomers of LIX65N is alsostudied here to elucidate the mechanisms involved.

~19 0-- ~ I

Y~. OH I n J, a..t

(ANTI-) (SVN-)(2-HYD~()XY-5-~IO'1Yl-B[NZGP'~[Nf)'IE QXi'.~). 1IX65!1

Fig. 1- Schematic diagram of LIX65N.

C9H19

:6

Ahetraet- This study initiated to explore the potential of com-mercial chelating extractant for beneficiation of mineralsrevealed" UX "6'N to be an excellent coUector for cuprite andchrysocolla. The collector action of the UX is proposed to resultfrom its chelation with copper species on the surface of theminerals. Thw, the SJ1f.-isomer of UX65N, which is unable toform a chelate with copper ions, fa,led also to act as a collector.The proposed mechanism takes into account partu'"oning ofUX between the mineral surface (to form a surface chelate) andthe copper chelate dispersed in the bulk aqueow phase (eitherdue to formation of the chelate with dissolved copper, or due todetachment of chelate formed at surface). The efficiency of thecollection is dependent upon this partuioning since the bulkchelate is found unable to collect. The marked decrease ,nflotation obtained when copper uw added to the system supportsthis mechanism. The dependence of flotation of chrysocollaand cupn"te on pH and reagentumg time is discussed on thebasis of the proposed mechanism.

Batch laboratory flotation tests wing syntheu.c mixtures ofoxide, sulfide and mixed oxidt-sulfide copper minerals wa"thquartz demonstrated the abu'"ty of LIX to separate the copperminerals from quartz.

" ,~:0 "-

~

C'IIN

CIIN

Introduction (Jot

D. R. N8g8r8j, Member SME, is affiliated with AmericanCyanamid Co., Stamford, Conn. 06904. P. Som8sundaran,Member SME, is Professor of Minerai Processing, Henry KrumbSchool of Mines, Columbia University, New Yorl<, NY 10027,SME preprlnt 778218. Manuscript June 29, 1977. Discussion ofthis paper must be submitted, in duplicate, prior to July 31,1980.

Chelating agents. because of their specificity toward cenainmetal ions, are ideal for use as collectors for beneficiation ofores. A classic example is the use of xanthates as collectors forflotation separation of sulfides. Chelating agents have also ~used as collectors for the flotation of a variety of non-sulfideminerals. 1-7

The availability of certain chelating agents such as thehydroxyoximes under the name "LIX" extractants has nowmade solvent extraction one of the mOSt attractive techniquesfor purification and concentration of copper leach liquors.S-IOThis can be attributed mainly to the high copper selectivity thatthese extractants possess under cenain conditions. Whereas the

I~T~ VOl - Society of Mining Engi~fS of AIME

Cool Type

q

m>:I:

4

~I

~~

rJ\

-- -cD ~.> C-' 4

~801

60

40

20

>e

2'C.l

. 0 -~ ::i; . , . ,

10 15 80 85 90 -'Totol Corbon ( Dry. Ash Free). _/0

Fig. 7- (va. total carbon content (rank) In a methanol environ.ment.

~

Acknowledgements

The work described herein was initiated under a grant fromthe Gulf Oil Foundation and completed under ERDA ContractNo. EY-76-S-02-2871.*OOO. By counesy of L.G. Austin, thegrinding studies were carried out by J.S. Shah and M.S. Celik ofthe Mineral Processing Section, Dept. of Material Sciences, ThePennsylvania State University. J.R. Sweet perfonned the zetapotential detenninations.

References

Reagents on the Wet Grinding of Quanz, " Powder Technology,

Vol. 18, 1977, p. 179.8Hanneman, R.E., and Westbrook, J.H., -Effecu of Adsor-ption on the Indentation Deformation of Non-Metallic Solids,-The Ph,"ZosoPhical Magazine, Vol. 18, 1968, p. 75.9Pensov, N.V., cited in Rebinder, P.A., and Shchukin, E.D.,-Surface Phenomena in Solids During Deformation and Frac-ture Proceaes,- Progress in Surface Sc,'ence, Vol. 5, 1972/5, p.97.10Pertsov, N.V., Sinevich, E.A., and Shchukin, E.D.,"Strength Reduction in Molecular Crystals Due to Adsorption,"Dokl4d, AUdemii Nou. SSSR, Vol. 179, 1968, p. 655.IISinevich, E.A., PenJOv, N.V.. andShchukin, E.D.. -Resultsof Determining the Surface Energy of Naphthalene SingleCrystals by Splitting in Different Liquid Media,"Smachiwemost i Pover.hnostnye Swutm Rasplawv Tverdy.hTel, Instytut Problem Materialomavstm, Akademii Nauk, UR-SR, Kiev, 1972, p. 64.12SkVOrtlOV, A.G.. et aI., -Determination of the Surface Energyof Naphthalene Crystals by a Cleavage Method,- DoklodyAkademii Nou. SSSR, Vol. 195, 1970, p. 76.15Sinevich, E.A., Pensov, N.V., and Shchukin, E.D., "Reduc.tion in the Stability of Polycryaalline Naphthalene During Ad.sorption of Surface Active Agents from Aqueous Solutions.-Doklad, Akademai' Nou. SSSR, Vol. 197, 1971, p. 1576.14Shchukin, E.D., et al., -Selectivity of the Reduction in theStrength of Polymer Materials Subject to the Action of SurfaceActive SubStances,- Sow'et Materials Science, Vol. 7, 1971, p.160. (trans. from Fmko-KhimichesMya Me~ Materialov,Vol. 7,1971, p. 55).15Poeluev, A.P., et aI., -Effectiveness of Dust Suppression byWetting Coal Seams by Solutions, - Bor 'bo SilIM%Om, AkademiiNaukSSSR. SbornikStatei, Vol. 7,1967, p. 72.16Shilenkov, V.N.. -Mechanism of the Weakening of a CoalMus During Its MoiStening," Doklad, AUdemii Nouk SSSR,Vol, 157, 1964, p. 961.I 7 Polferov , K. Ya., et al.. "Increasing the Effectiveness ofPulverizing Coals With the Aid of Surface Active AgentS,"TeploenergetiM, Vol. 17, 1970. p, 26.18Et~, I.L., Lamba, E.G., and Adamov, V.G., -The Roleof the Gaseous Medium in Processes of Disintegration of Coal,"Do.lady Akademii Nou. SSSR, Vol. 115, 1957, p, 585.19A1drich, R.G.. -The Effect of Chemical Additives on theProduction of Fine Particles in Coal Fragmentation, - Final

Report on US Bureau of Mines Contract No. HOI01704,S~acuse University Research Corp., Syracuse, 1971.2 Datta, R.S., Howard, P.H.. and Hanchett, A., -FeasabilityStudy of ~-Combustion Coal Cleaning Using Chemical Com-

I Macmillan , N.H., .Chemisorption Induced Variations in thePlasticity and Fracture of Non-Metals,. Surface Effects inCrystal Plasticit,. Noordhoff, Leyden, 1977, p. 629.2Westwood, A.R.C., and Macmillan. N.H., .Environment-Sensitive Hardness of Non-Metals,. The Science of Hardne.s.sTesting and its Research APPlications, American Society forMetals, Metals Park, 1975, p. 577.5Westwood, A.R.C., .Tewksbury Lecture: Control and Ap-plication of Environment-Sensitive Processes,. Journal ofMateriGLs Science, Vol. 9, 1974, p- 1871.4Macmillan, N.H., and WestWood, A.R.C., .Surface Charxe"Dependent Mechanical Behavior of Non.Metals,. Surfaces andInterfaces in Glass and Ceramics, Plenum Presa, New York,1974, p. 495.5Westwood, A.R.C., and Latanision, R.M., .Environment-Sensitive Machining Behavior of Non.Metals,. The Science ofCeramic MachIning and Surface Finishing, Special Pub. No.548, National Bureau of Standards, Washington. DC, 1972, p.141.6Westwood, A.R.C., and Mills, J.J., . Application ofChemomechanical Effects to Fracture-Dependent IndustrialProcesses.. Surface Effects in Crystal Plasticit,. Noordhoff,!.eYden.1977, p. 855.7R.yncan, A., and laskowski, J., "Influence of Flotation

rra_- Val --,81SocWty of MIning Engi.-rs 01 AI.

c , .00 I :~ _I - - I

I , I , ',' I-I Me'hanol Envlron",.n'

Materials and Methods-Reagents Synthetic mineral mixtures-For the batch laboratory celltesu. mixtures of quanz (Arkansas. 99 + %) with chrysocolla(Black Hills Minerals). chalcopyrite (Ward's) and chalcocite(Ward's) (all-14 mesh) were prepared by wet-grinding in alaboratory porcelain ball mill at 60% solids by weight. and wet-screened to obtain - 65 to + 525 mesh fraction assaying ap-proximately 2.2% Cu. This fraction was used for batchlaboratory cell flotation tesu.

MicroDotanon Tests

LIX65N-LIX65N, representative of the aromatichydroXYOximes was obtained from General Mills, Inc. The as-received LIX65N is an amber liquid of specific gravity 0.9, andpure LIX65N is a yellowish-brown viscous liquid. It is im-miscible with water, and as-received contains a large amount ofdiluent which is added to facilitate handling.ll LIX65N wasused for flotation after purification using the procedurefollowed by Atwood and Millerl2 and Ashbrook.15

LIX65N has tWO isomeric forms, the anti-(I) and the syn-(11).12.15 Pure LIX65N contains about 80% of the anti-isomer15 which is also the active isomer for chelation.

Syn-LIX65N was obtained as a white precipitate from hexaneextracts during purification of commercial LIX. Recrystalliza-tion of this precipitate from hexane gave white. needle-likecrystals of pure syn-65N. The anti-isomer obtained afterpurification contained a small amount of syn-65N and was usedwithout further separation of isomers.

The purified LIX65N and its isomers were characterizedusing lRA-l Jasco infrared spectrophotometer.

Cu.LIX65N bulk chelate-Purified LIX65N was dissolved incarbon tetrachloride. thoroughly mixed with an excess of cop-per sulfate solution and then allowed to stand for completephase separation. The organic phase containing the Cu-LIX65N chelate was then separated from the aqueous phase.washed with water. and vacuum desiccated for fifty hours toremove the solvent. The Cu-LIX65N chelate was also charac-terized by its IR spectrum.

Collector emulsion-For batch Denver cell flotation tests, anemulsion (oil in water) of LIX65N in hexane was prepared using"Tergitol" (Union Carbide) as an emulsifier in a blender at a pHof about 11.0.

Other reagents-Dowfroth 250 was used as a frather for theDenver cell tests. No frother was used for the microflotationtests. KOH and HNO5 were used for pH control and KNO5 forionic strength control. All the chemicals used were of reagentgrade. and acetone was of spectroscopic grade. Triple distilledwater was used for all the tests.

Minerals

The preparation of cuprite and chrysocolla for microflotationtesu haa been described earlier.14 Briefly, the -65 to + 150mesh fraction of cuprite and - S5 to + 65 mesh fraction ofchrysocolla were used. X-ray and chemical analyses showedcuprite to be 95% Cu20 (84% Cu), 2% iron and 2% quanz,and chrysocolla to be S5% Cu and 44% silica.

80

60c\&I'49IL

#.0

The procedure for microflotation tests has been describedearlier .14 Briefly, to a deslimed mineral suspension in water.LIX65N was introduced as an acetone solution. and the mineralwas conditioned by tumbling at 15 rpm. (Instantaneousemulsification occurred when the acetone solution of LIX wasbrought into contact with the aqueous suspension.) Mter con-ditioning. the mineral was floated in a hallimond cell by passingnitrogen at 20 cc/min.

Batch-Laboratory Cell Tests

Conditioning-500 g of the - 65 to + 525 mesh syntheticmixture was suspended in 1200 mL distilled water in a 2.5 L D-lDenver laboratory flotation cell. The pulp was agitated at 1800rpm for 5 min. during which time the pH of the pulp was ad-justed to the desired value. The collector emulsion was then in-troduced. volume of pulp was made up to 2.5 L (-20% solids).and the minerals mixture was conditioned for 4 min. at 1800rpm. The frother was added during conditioning.

Aotation-l'1otation of the conditioned minerals was carriedout by passing air at approximately 8.5 L/min. while the pulpwas kept in suspension at 1500 rpm. l'1otation was conducted tocompletion as indicated by a barren froth. In some tests therougher concentrate was cleaned. Conditions in the cleanerflotation were milder than in the rougher flotation; agitationwas 1500 rpm in the first and second cleaning, and 1500 rpm inthe third cleaning. and the air flow rate was in the range of 4 to6.5 L/min. Frother was added when necessary. but no freshcollector addition was made. In some tests a scavenger flotationof the cleaner tailings was also carried out.

100[ - i -r ~~~R:~O:O~L:~"~~" - - /T/"?:::\\' l\ 00~6 GPL L" ,

i O---OCUPRITt -L'X6~" i. 000'6 GP\.\.'x f

I ~--OC.Lf&CHEOFR(N ? \.\ C"zO OJ 10 MI..! "00 M~ CONOoT'O..o..G !. ' M'" 'LOT&TOOOl '

.P"'

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t~., S

A.a.

If ';\

/4\

rLOTATI~ I;

i

A, .

.EACHED C..

r--

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G

zo 1~

0o~ -3 5 7 9 1\

pHFig. 3-Flotation of chrysocolla and cuprite, along with con.

centration of copper leached from cuprite, as a func.tion of pH. (Curves for cuprite. reproduced from CRC

press publication.14)

Fig. 2- Flotation of chrysocolla and cuprite as a function ofconcentration of LlX65N. (Curve for cuprite. repro-duced from CRC press publication,14).

TI8"'ct~ Vol. 25-1-Society 01 Mining Engi.-rs 01 AIME

R~ts-Micronotation Tests

Results obtained for flOtation of chrylOCona as a function ofconcentration of LIX65N are given in Fig. 2, along with thOleobtained earlier for cuprite .14 It can be Ieen that a mw:h higherconcentration and longer reagentizing time are necesaary forcomplete flotation of chrysocolla, compared with those forcuprite. Tho 0 in accord with the fact that chrysocolla isrelatively difficult to float.

Thr flotation ruponse of chrysocona as a function of pH ispreRnted in Fig. 5. The results obtained for flotation as wen asIOlubility of cuprite are a1IO given in this figure. The IOlubilitydata given are those obtained from 10 min. leaching testscarried out with 1 gram cuprite in distilled water in the a~ceof UX. The lignificance of the solubility data will be discu8edin a later section. It is Been from Fig. 2 that two fbation maximaare obtained for cuprite at pH of about 5.6 and 10.5, and forchryaocolla at pH of about 5 and 10. An apparent inverserelationship between flotation and solubility of cuprite is to beDoted in Fig. 5. In the pH range of 6.5 to 9, ~, IOlubilityis almost CODItant, and flotation is continuously decreasing.

These resultS suggested that flotation of cuprite andchryaocolla could in fact be sensitive to the concentration ofdi8Olved copper species. Furthermore, since the concentrationof copper released from the mineral is dependent upon thereagentizing time, a dependence of flotation on re~tizingtime is a1IO to be expected. Results obtained from tests conduc-ted to check this possibility are given in Fig. 5. Data are presen-ted for chrylOColla at only 0.52 glL and 0.064 glL of UX65N,and for cuprite at 0.0052, 0.026 and 0.052 g/L. An imponantfeature to be noted from Fig. 4 is the occu~ of a maximumfoUowed by a decrease in flotation of cuprite at higher concen-trations of LIX65N. In contrast to this marked dependence ofcuprite flotation on reagentizing time, chrylOCona flotation doesDot exhibit a maximum in the range tested.

The effect of concentration of dilaolved copper species onfbation is more directly examined by adding copper before andduring reagentizing of cuprite or chrYJOColla. Figure 5 givesresults of flotation of cuprite and chrysocolla as a function of

100 f J>

initial concentration of copper, which was added in the forDl ofCu(NO5)t to the solution before introducing LIX in thereagentizing stage. As can be seen from Fig. 5, even small ad-ditions of copper markedly decrease the flotation of bothminerals.

Table 1 summarizes the effect of addition of copper duringreagentizing of chrysocolla with LIX65N on flotation ofchrysocolla. It is seen from Table 1 that copper addition duringreagentizing also is effective in reducing flotation but not to thesame extent as the addition prior to that of mineral.

An important oblervation made during the re~tiring ofthe copper minerals with LIX65N was the appearance ofyellowish-brown globules (dispened in the bulk aqueous phase).As this resembled the copper-LIX65N chelate forDled betweenLIX65N and copper ions, it was suspected that a portion of theadded UX was consumed in the forDl of a Cu-LIX65N chelatediapened in the bulk.. It was therefore decided to investigate thecollector aCtion of this chelate.

The results obtained for the flotation of chrysocolla andcuprite with Cu-LIX65N chelate are given in Table t. In-terestingly, the Cu-LIX65N chelate failed to collect bothchrysocoUa and cuprite under all the conditions tested. It is tobe noted that complete flotation of both minerals could be ob-tained with the LIX65N under these conditions. An intriguingobservation here was that even at a relatively high concen-tration, LIX65N failed to collect chryIOColla and cuprite whenit was added along with the Cu-LIX65N chelate, whereas thesame when added alone was very effective in floating theseminerals.

Another important aspect of the present work was the obser-ved difference in the collecting property between the iaomers ofLIX65N (lee fig. 1). The iaomers ~ used in separate tnu ascollecton for the flotation of chrysocoUa. (It must be noted herethat in all other tests described in this paper the reagent wasmOldy in the anti- forDl.) For flotation tests, solutions of syn-isomer were made in the IOlvents hexane, kerosene, acetone orcarbon tetrachloride, and a dispersion of each of these IOlutionawas made in water with and without an emulsifier "Tergitol".flotation was carried out in both the pH ranges, namely 4 to 6and 9 to 11 where chrysocolla was expected to float (fig. 5).Concentrations of the ayn-ilOmer up to 0.16 g/L and reagen-tiring periods up to 60 min were employed. It was found fromthe tnu that the ayn-isomer is unable to collect chrysocolla whiJethe anti-iaomer is capable of floating it under the tested con-ditions. The significance of such a difference in the chelatingability between iaomen of a re~t in regard to flotation isnoted for the fint time to our knowledge.

-::::--

A.-~~~::::; -',~~ -:0;; PI. I..

d'

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Q11/30

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...,~~~ _t

;OOII.~L~ . .120 40 60

CONDITIONING TIME, M'..

Fig. 4- Flotation of chrysocolla and cuprite as a function ofreagentlzlng time at LIX65N concentrations of 0.0032,0.028 and 0.032 gpl for cuprite, and 0.032 and 0.084 gplfor chrysocolla. (Curves for cuprite. reproduced fromCRC press publlcatlon.1~

L- . . .~~,~j~ Ctfi"T~LA -. --;:to ,. .O56~LIX

'."10

k)-s k)-4 10" 1([1INITIAL ~ aKENTRATk)N. "L

ol.~::::= .0

Fig. 5- Flotation of chrysocolla and cuprite using LIX65N asa function of Initial concentration of added copper InSolution, at natural pH of the systems. (Reproducedfrom CRC press pubIICation.14)

1--T~ VOl 28Soc-ty of IM!ling Engi.-rs of AI~

Table 2Table 1- Total Aeagentlzlng* Time: 10 min.; Collector: 0.056OPI Antl.LlX65N; pH: 5.6 . 5.8. Copper Added Was Equivalent

to 10-4M.as Cu(NO3>2' YoFIoeted,1 mln.

flotation

pttCondo lime,

min.

Chlysocolla

103060~~

~

~

Inhial tln8lCollector1'-8'

Cu eddllion,min.

CueddilionNONE

10-4M. Cu2 +

Remarts% Floe,""64.614.3

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5.85.85.8

10.04.0

5.8

5.8

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U

8.4

3.30.1

12.313.22.7

0.13 OPI Cu-UX66NChelate.0

0

Copper addedbefore minerai

Copper and mineraladded sln-."-.eouslyCopper added afterminerai, i.e. duringreegentlzlng

0.26 gpl Cu.UXMNChel.te

0.13 gpl Cu-LIX66NChelate +

0.064 gpl UX85N

0.064 gpI LIX65Nalone

...

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58.0

25.0

26.0~30

Cuprite

10

5.8 ...0.0194 Opt Cu-lIX65N

Chelate

0.017 OplllX65Nalone

0.0194 OPI Chelate+0.0170pl LIX65N

.Reagent/zlng In. '30 ml cylinder (with pH .iectrode.nd thermometer) by agitatingmln"" .t500 rpm In the collector solution.

..Attheendol '0 min. ~nt/zlng

5.8

5.8

5.8

5.7

5.8

12.0

100.0

39.0

10

10 uDiscussion

'Equl~.Ie"t 10 1.73 X 1U2~ ofc"""'orO. t1 gplof UX85N

The reasons for the occurrence of Cu-LIX65N chelate in thebulk are two-fold as explained below. It is recognized thatduring reagentizing. LIX molecules can enter into two com-peting processes. as shown in Fig. 8.

Proceu I-They can adsorb on the mineral by forming a sur-face chelate (see Fig. 6); this chelate can then detach itself fromthe surface of the mineral and get dispersed in the bulk aqueousphase as the bulk copper chelate (see Fig. 7).

Proceu 2-A pan of the LIX can also form a chelate in thebulk aqueous phase with the copper released into bulk from themineral.

It is now to be noted that if the bulk chelate has no ability tocollect. then LIX associated with the bulk copper chelate willbecome essentially unavailable for flotation. Indeed. the resultsgiven in Table 2 confirm that the bulk chelate. once formed inthe bulk. contributed little to the flotation of the mineral.Results in Table 2 also suggest that an additional amount ofLIX may be abstracted by this chelate. the reasons for which arenot known at present.

A third consequence of the occurence of bulk Cu - LIX chelateresults from the dependence of process 2 (Fig. 8) on the concen-tration of copper in the bulk. In the absence of any externalsource, the only source of copper in the system is the mineral it-self. The extent of process 2 is therefore dependent on the con-centration of copper leaching from the mineral. which in turn isinfluenced by various parameters such as pH. and reagentizingtime.

The microflotation results obtained in this investigationdemonstrate firstly the ability of LIX type of reagents to func-tion as collectors for oxidic minerals.

The concentration dependence given in Fig. 2 shows the needfor much higher concentrations, compared with those forcuprite. for complete flotation of chrysocolla. a mineral which isknown for its relatively low flotation response to almost all thecommon collectors.

At the concentrations investigated here, flotation of copperminerals with LIX65N showed a strong dependence on pH (Fig.2). Although the.maximum in flotation response around pH 5.6for cuprite and pH 5.0 for chrysocolla could possibly be ex-plained on the basis of maximum adsorption of CuOH +species.15 the maximum around pH 10 for both minerals can-not be accounted for by this mechanism. An insight into themechanism of flotation in this system was obtained both fromthe data given in Fig. 2 for the copper leached from cuprite as afunction of pH. and from the observation made duringmicroflotation tests that Cu-LIX65N chelate was found disper-sed in the bulk.

The collector function is proposed here to be the result offormation of a surface chelate between LIX and the copperatoms on the surface. This 'surface chelate' could beschematically represented as depicted in Fig. 6.

The surface chelate exposes a hydrophobic exterior favoringbubble attachment to the mineral and hence flotation.

It may be recognized that this surface chelate need not beidentical with the chelate formed with Cu2 + ions in the bulkaqueous phase, as shown in Fig. 7.

c;,~~O.:H-O, 0~- --"'CU..-N-C'Jd/OC-N"- ... *, ;.0

:0 O-tor'"

~HI~Cllt-.. ~c.Q 1-

HoN OH J~

COPPERMINERAL

MG.

LIX65N Cu(LIX65NJz CH~LAT£ IN

THE BULK AQUEOUS PHASE

Fig. 7-0ccurrence of Cu-UX65N chelate in the bulk aqueous

phase.Fig. 6-Schematic of surface chelate.

Transactions Vol. ~18ESociety of Mining Engineers of AlME

Fig. 8- The two competing processes in which the lIX mole-cules participate, resulting in Cu.lIX65N chelate in thebulk of the solution.

With reference to the pH dependence of flotation shown inFig. ~, observed maxima in flotation are noted to correspond tothe minima in copper leached from the mineral. I'lotation in thebasic pH range could also be attributed panly to other factorssuch as change in surface active properties of the LIX reagentand its increased ionization or solubility as its pKOH is aroundpH 10.0. I'lotation decrease in the pH range 6 to 9, on the otherhand. could possibly be explained by the nature of surface ofmineral itself which in this pH range is expected to exposepredominantly a coordinatively saturated Cu(OH)2.

At conStant pH conditions, the copper introduced into thebulk by leaching of the mineral increases with reagentizing timeand hence affects the panitioning of LIX65N between themineral and the copper in bulk, and thereby the flotation. Fur-thermore. detachment of the surface chelate can also be expec.ted to be a function of time. Although, at this stage. it is dif-ficult to say which of the processes I and 2 (Fig. 7) ispredominant. both could be expected to be operative. Resultsgiven in Fig. 4 showing a maximum in flotation response ofcuprite as a function of reagentizing time can perhaps be ex-plained by detachment of the chelate rather than by increasedformation of bulk copper chelate with leached copper since sucha maximum followed by a decrease in flotation is absent forchrysocolla. On the other hand. absence of flotation maximumfor chrysocolla could be because of slower adsorption of LIX onthis mineral compared with that for leaching of copper.

Funher insight into the mechanism via processes 1 and 2 isobtained from results given in Fig. 5 and Table I. Copper addedjust before the mineral was introduced into the collectorsolution in the reagentizing stage will severely compete with themineral for LIX molecules, resulting in a large panitioning ofLIX. hence the marked decrease in flotation of both cuprite andchrysocolla (Fig. 5). A marked decrease in flotation ofchrysocolla was also observed when both mineral and copperwere simultaneously added to the collector solution (Table I).Copper addition during reagentizing also seriously affectsflotation suggesting that panitioning of LIX (process 2, Fig. 7)is cenainly an imponant factor.

The flotation of copper minerals by LIX65N was earlierproposed to be the result of formation of a chelate by LIX65Non the mineral. That this is a prerequisite for flotation is sup-poned by the finding in the present work that the syn.isomer ofLIX65N failed to collect chrysocolla under all the conditionstested here (see Results section).

From studies in analytical chemistry of hydroxyoximes9.12, I~it is known that the syn.isomer does not form a chelate withcopper ions in solution because of steric reasons, and does soonly when the syn.form transforms into the anti-form. It is con-ceivable that the syn-isomer cannot form a chelate on the sur.face of the mineral also.

It must be noted here that the collector propeny of syn-LIX65N cannot be tested under all conditions of pH, reagen-tiling time and presence of solvents such as acetone or alcoholbecause the syn.anti transition is very sensitive to all theseparameters; a brief discussion of this is to be found in references9,16,and17.

It is clear from the results that the reagent is selective tochrysocolla. and that cleaning of the rougher concentrate isnecessary to obtain the best grade; the first fraction of thecleaner concentrate analyzed about 21.5% copper with arecovery of 69%. During the flotation test. a majority of thecopper minerals was observed to float rather fast (in the first 20sec).

ChrysocoUa-maloopyrite-chalcocite-quartz mixture- Resultsof a typical flotation test are presented in Table 4. The coUectoremulsion contianed 0.02 kg/t (0.04 lb per It) of Tergitol and0.46 kg/t (0.95Ib per st) of LIX65N in Hexane'" 5 kg/t or'" 6lb per st). The rougher concentrate (4 min flotation) wascleaned thrice. During the 5rd cleaning) pH "'7.8, 1500 rpm,4.5 L/min air) three flotation fractions, corresponding to 0-20,20.60. and 60.180 sec of flotation were collected. A microscopicexamination indicated that during the first 20 sec only sulfidesfloated; in the next fraction a majority of chrysocolla floatedand in the last fraction copper minerals were present in onlysmall amounts. This order was also observed for the rougherconcentrate; sulfides had a tendency to float much more readilythan chrysocolla, suggesting the possibility that sulfides may befloated in the first stage and perhaps at a much lower reagentlevel. A stagewise addition of collector was hence consideredpotentially beneficient.

Table 5 gives results of a flotation test carried out with 0.242kg/t (0.485 lb per It) of LIX65N added stagewise-0.025 kg/t(0.05Ib per st) in the first, and 0.217 kg/t (OA551b per at) in thesecond stage. Reagentizing time in each stage was 4 min and pHwas "'10.5. lOA. A microscopic examination of the concentratesobtained indicated that the lit stage concentrate contained onlysulfides (all sulfides recovered; grade 45% Cu) and nochrysocolla or quartz, the 2nd stage concentrate containedmainly chrysocolla and some quartz ("'90% recovered; amajority analyzing 55% Cu). From the results in Table 5 it isclear that a stagewise addition of LIX65N is advantageous. Ascavenging flotation did not seem to be very effective becauseonly 5% of total copper was recovered at a grade of 0.82% Cu;copper rejected in the tailings was also very low. Furthermore,the total reagent level for comparable results is half that used inthe test presented in Table 4.

The results of batch laboratory flotation tests (Tables 5 to 5)have thus clearly demonstrated the ability of LIX65N to selec.Batch Laboratory Tests

Table 3

Flat. time Weight Gr8de %sec. % %Cu RecoV8ry

100.0 2.130-20 4.7 31.:.1 88.0

20-60 3.1 8.44 12.460-150 3.0 4.42 8.3

7.1 1.21 4.0310 O.~ 5.251.1 0.13 3.2

0 11Recovefy

FeedAecl88ner concentrate

Scavenger concentrateScavenger tailingRougher tailing

Chrysocolla-quartz mixture-Results of a typical flotationtest are presented in Table 3. The collector emulsion contained0.034 kg/t (0.069Ib per st) of Tergitol* and 0.5 kg/t (lIb per It)of LIX65N in hexane (3.0 kg/t or 6.1 Ib per st). The rougherconcentrate (4 min flotation) was cleaned twice. During thesecond cleaning (total 2.5 min flotation) solids which floated inthe first 20 sec, and betWeen 20-60 sec and 60-150 sec werecollected separately. A scavenger flotation of the 1st and 2ndcleaner tailings was also carried out.

'Tnpol-- - no "ol/#""",obilil,.wn wh." /o'K' ...0..01, -. odd.d

'--Tr..-ctlons Vol. ~ Society of Mining Engi of AIME

tively float copper mineTall. especially chr)'locoila. from syntbetic mixtures witb quanz.

Summary and Conclusions References

. Application of LIX chelating agents as collecton for theflotation of copper minerals is discussed in this paper. Thesereagenu, which are currently used commercially for the solventextraction of copper, have been found to function as collectonfor copper minerab.

. Both microflotation tests on chrysocolla and cuprite, andbatch laboratory cell tests on synthetic mixtures of copperminerals-chrysocolla, chalcopyrite and chacocite-with quartzhave been carried out using LIX65N.

. On the basi. of the p~liminary microflotation tests, amechanism has been proposed which is based on the par.titioning of LIX65N between the mineral surface and the bulkaqueous IOlution in the latter either due to chelation withdissolved copper species from the mineral or due to detachmentof chelate from the mineral surface. The LIX65N associatedwith the chelate dispersed in the bulk become. essentiallyunavailable for flotation. Thw was confirmed by the findingthat the bulk chelate failed to collect chrysocoila or cuprite.

. The mechanWm is supponed by the findings that copperadded to the collector solution just before or simultaneou.lywith the mineral, or at various times during the reagentizing ofmineral with LIX65N, markedly decreased flotation ofchrysocolla and cuprite.

. flotation of cuprite as a function of reagentiling time at.tained a maximum followed by a decrease at higher concen.tration of LIX65N. This was explained panly by the propoeedmechanilm and a1IO by detachment of surface chelate. flotationof chrysocolla had no such maximum under the tested con.ditions.

. F1otation response of both cuprite and chrysocolla as afunction of pH had maxima around pH 5 and pH 10. Themaxima have been explained using the data for concentrationof copper leached from cuprite as a function of pH. and on thebasis of the propoeed mechanism.

. The syn.isomer of LIX65N that does not chelate withcopper failed to collect chrysocolla supponing the mechanismthat flotation of copper minerals with chelating agenu such asLIX65N is possible only through the formation of a copperchelate.

. Batch laboratory cell flotation tests have demonuratedthe ability of LIX65N to selectively float copper minerals,especially chrysocolla, from synthetic mixtures with quanl.

Acknowledgment

1 DeWitt , C.C., and Batchdder, F.V., "Chdate Compounds uFlotation Reagenu, " Joumal 0/ American Chemical Society,

Vol. 61, 1959, pp. 1%47 and 1%&0.%Ludt, R.W., and DeWitt, C.C., "The Aotation of CopperSilicate from Silica," Tnms. AIME. Vol. 184, 1949, p. 49.5Petenon, H.D., Fuemenau, M.C., Ricard, R.S., and Miller,J.D., "Chrysocolla Flotation by the Fonnation of InIOluble Sur-face Chelates, " Tnms. SME-AlME, Vol. 25%,196&, p. SS9.

4Usoni, L., Rinelli, G., and Marabini, A.M., "Clelating Agen-u and Fuel Oil: A New Way to Aotation," A/ME CentennialAnnual Meeting, 1971, New York, prepn"nt 71.B-10.5Rinelli, G., and Marabini, A.M., "Flotation of Zinc and LeadOxide-Sulfide Ores with Chelating AgenU," Proceedings. 10thInternational Mineral Proce8ing Co~, London, 1975, p.495.6Rinelli, G., Marabini, A.M., and Aleue, V., "Flotation ofCassiterite with Salicylaldehyde.. a Collector," Rotati4m. A.M.Gaudin Memorial Volume, Vol. I, M.C. Fuentenau, ed.,AIME, New York., 1976, pp. &49-&60.7Mubi, S., and Wabmauu, T., "Some Problems of CopperOxide Mineral Flotation," SME-AIME Fall Meeting, Den~,1976.8Flett, D.S., and Spi~, D.R., "Solvent Extraction of Non-Ferrous Metals: A Review 197%-74," HydrometaUuTB)', Vol. I,No.5. 1976, p- 207.9Ashbrook, A.W., "Chdating Reagenu in Solvent UtraCtionProceues: The Present Position," Coordination ChemistryReviews, Vol. 16, 1975, p. %85.10Hopkina, W.R., and Lynch, A.J., "Anamo Oxide Plant: ANew U.S. Dimension in Solvent Extraction," Engineering andMiningJournal, Feb. 1977, pp. &6-64.IISwanson, R.R., "The Chemistry of Oximes, " American

Chemical Society Centennial Annual Meeting, San Frana..co,A~- 1976.12Atwood, R.L.. and Miller, J.D., "Structure and Compositionof Commercial Copper Chelate Extractanu," Trans. SME-AlME, Vol. %&4, 1975, p. 519.15 Ashbrook.. A- W -, "Commercial Chelating Solvent ExtractionReagents I. Purification and lIOmer Separation of 2-Hydrox-yoximes," Journal o/Chromatograph" Vol. 10&, 1975, p. 141.14Nagaraj, D.R., and Somuundaran, P., "Chelating AgenU uFlotaids: LIX-Copper Minerals Systems," American ChemicalSociety Centennial Annual Meeting, San Francisco, Aug. 1976.I&Palmer, B.R., Gutierrez, B.G., Fuentenau, M.C., andAplan, F.F., "Mechanisms Involved in the Flotation of Oxidesand Silicates with Anionic Collectors, Parts 1 and %," Trans.SME-AlME, Vol. 258, 1975, p. 257.16 Ashbrook., A. W ., "Commercial Cbelating Solvent ExtractionReagenu III. Oxime.: Spectra, Structure and Properties,"H!:rometaUurgy, Vol. I, 1975, p. 5.1 Kohler, E.P., and Bruce, W_F., "The Oximes of Onho-Hydroxy Benzophenone,"J. American Chem. Soc., Vol. 55,1951, p. 1569.

Suppon for this work by the National Science Foundation.Interfacial Chemistry of Selected Fine Particles ProcessingSystems. NSF-ENG-76-SO159. is acknowledged.

Society 01 MIning EngiI-.8 01 ANE TIW-=tiOIw Val. --187