PROTECTED BUSINESS INFORMATION
CHARACTERIZATION OF THIOSALTS GENERATION DURING MILLING OF
SULPHIDE ORES
OCTOBER 1999
MINING AND MINERAL SCIENCES LABORATORIES T. Negeri, A.D. Paktunc, M. Boisclair and D.M. Kingston Work Performed for: THIOSALTS CONSORTIUM
Job No. 601838 CONFIDENTIAL MINING AND MINERAL SCIENCES LABORATORIES REPORT MMSL 99-055 (CR)
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
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EXECUTIVE SUMMARY
Experimental studies were undertaken on a pyritic Cu-Zn ore from the Louvicourt mill and
pyrrhotite-rich Cu-Ni ore from the Strathcona mill with the overall purpose to identify the
processes, conditions and mineralogical characteristics that may influence the production of
thiosalts during milling of sulphide ores.
Experimental studies involved batch, semi-batch and continuous milling and flotation tests to
(1) study the influence of pH, temperature and residence time, (2) assess grinding media
effect, (3) simulate the Louvicourt and Strathcona mill conditions, and (4) study the effects of
mineralogy on thiosalts generation.
The effects of pulp temperature, residence time and pH on thiosalts generation appear to be
linear. The pyrrhotitic ore appears to be more sensitive to pulp temperature, whereas the
pyritic ore is more sensitive to changes in pH. Pulp residence time significantly affected the
thiosalts generation during processing of the pyrrhotitic ore, but not the pyritic ore.
The amount of thiosalts generated during grinding strongly depends on the type of grinding
media used; the stainless steel produces more thiosalts than mild steel grinding media. The
pyritic ore is oxidized faster than the pyrrhotitic ore during grinding regardless of the
grinding media type. The use of more active media or semi-autogenous grinding would
generate less thiosalts than inert media or autogenous grinding.
Flotation of the pyrrhotitic ore produced more thiosalts than the pyritic ore at pH values
typical for flotation. Continuous testing results on the pyritic ore indicated that an estimated
23% of the overall thiosalts determined originated from the feed while grinding, aeration,
copper circuit flotation and Zn circuit flotation contributed 17%, 5%, 50% and 5%
respectively. Semi-batch testing results on the pyritic ore indicated that grinding contributed
approximately one-third of the total thiosalts generated. Copper rougher/scavenger/cleaner
circuit produced 23% of the total thiosalts present, Cu cleaning stage being responsible for
approximately half of this amount. Zinc rougher/flotation/cleaner produced 26% of the total
thiosalts. Semi-batch testing results of the pyrrhotitic ore indicated that the collector
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
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conditioning contributed the highest amount of thiosalts generated in the circuit, followed by
the regrinding of flotation products in the pyrrhotite rejection circuit. The amount of thiosalts
in pulp solution increases with an increase in the collector xanthate and the amount of SO2
used during conditioning. The rate of thiosalts generation is the highest during the first few
minutes of conditioning including aeration.
Thiosalts generation is influenced by sulphide mineralogy. Thiosalts generation generally
increases with sulphide mineral content of the ore. Thiosalts generation rate appears to be
linearly dependent on the abundance of sulphide minerals in the ore.
A good portion of the thiosalts in mill circuit comes with the ore in dry form. Scrub washing
under inert atmosphere results in total removal of thiosalts contained in the feed ore.
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CONTENTS
EXECUTIVE SUMMARY iINTRODUCTION 1BACKGROUND INFORMATION 3THE INFLUENCE OF pH, TEMPERATURE AND RESIDENCE TIME ON THIOSALTS GENERATION
9
Test Methodology 10 Feed Sample Compositions 11 Mineralogical composition of the Strathcona Ore 12 Mineralogical composition of the Louvicourt Ore 13 Experiments on Thiosalts Generation 14 Mineralogical Composition of the Strathcona Samples 16 Mineralogical Composition of the Louvicourt Samples 19INFLUENCE OF GRINDING MEDIA ON THIOSALTS GENERATION 26 Test Methodology 26 Results and Discussion 26STUDY OF THIOSALTS FORMATION UNDER SIMULATED SULPHIDE ORE PROCESSING PLANT CONDITIONS
29
Continuous Testing of Thiosalts Generation by the Louvicourt Ore 29 Semi-batch Testing of Thiosalts Generation by Louvicourt Ore 31 Test Methodology 31 Results and Discussion (Louvicourt) 33 Semi-batch Testing of Thiosalts Generation by Strathcona Cu-Ni Ore 35 Results and Discussion (Strathcona) 35EFFECTS OF MINERALOGY ON THIOSALTS GENERATION DURING MILLING AND FLOTATION
37
Louvicourt Ore 37 Sample Preparation and Testing Methodology 37 Mineralogy 38 Test Results and Discussion 40 Strathcona Ore 42 Sample Preparation, Sample Mineralogy and Testing Methodology 42 Test Results and Discussion 47EFFECTS OF REAGENTS ON THIOSALTS GENERATION 50 Effects of Xanthate on Thiosalts Generation by the Pyrrhotitic Cu-Ni Ore 50 Effects of Sulphur on Thiosalts Generation by the Pyritic Cu-Zn Ore 51 Test Methodology 52 Test Results and Discussion 53CONCLUSIONS 53RECOMMENDATIONS 55ACKNOWLEDGEMENTS 55REFERENCES 56APPENDIX A: FIGURES (See Figure Listing - page vi) A1-A45APPENDIX B: PULP SAMPLES COLLECTED AT THE MILLS AND MEASUREMENTS B1-B2APPENDIX C: THIOSALTS (INDIVIDUAL SPECIES AND TOTAL THIOSALTS) ANALYSIS OF THE PULP SAMPLES
C1-C2
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TABLES
Table 1 Galvanic series of sulphide minerals 6Table 2 Bulk chemical analysis of the Strathcona (ST) and
Louvicourt (LV) ore samples 11
Table 3 Minerals identified, their relative abundances and particle sizes in the Strathcona ore
12
Table 4 Minerals identified, their relative abundances and particle sizes in the Louvicourt ore
14
Table 5 Test design parameters and results 15Table 6 Bulk chemical analysis of the experimental samples 15Table 7 Bulk chemical analyses of the Louvicourt samples resulted
from batch experiments 16
Table 8 Minerals identified, their relative abundances and particle sizes in the Strathcona samples
17
Table 9 Mineral quantities (wt%) of the feed and experimental samples 19Table 10 Minerals identified, their relative abundances and particle sizes in
the Louvicourt samples 20
Table 11 Mineral quantities (wt%) of the feed and experimental samples 22Table 12 Contributions by factors and their interactions to thiosalts generation
when factor settings change from low to high levels investigated 22
Table 13 ANOVA for selected factorial model (Pyritic Cu ore) 24Table 14 ANOVA for selected factorial model (Cu-Ni pyrrhotitic ore) 24Table 15 Experimental conditions and results of grinding media effect study 26Table 16 Effects of pulp pH (lime addition) on thiosalts generation
during grinding with stainless steel 27
Table 17 Flotation conditions for the Louvicourt ore 30Table 18 Thiosalts generation in the experimental grinding and flotation circuit 30Table 19 Bulk chemistry and mineralogical quantification of the flotation
products 34
Table 20 Flotation test results (separate Cu and Zn concentrates) 34Table 21 Flotation test results (combined Cu and Zn concentrates) 34Table 22 Bulk chemistry and mineralogical composition of the flotation
products 36
Table 23 Flotation Test Results (Strathcona ore) 36Table 24 Louvicourt experimental samples 38Table 25 Bulk chemical analysis of the samples prepared by gravity
separation 38
Table 26 Minerals identified, relative abundances and particle sizes in the Louvicourt experimental samples
39
Table 27 Mineral quantities (wt %) of the Louvicourt experimental samples 40Table 28 Louvicourt experimental sample size distributions 41Table 29 Test results 41Table 30 Strathcona experimental samples 43
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TABLES (Cont'd)
Table 31 Bulk chemical analysis of the samples prepared from magnetic and non-magnetic fractions
43
Table 32 Minerals identified in the Strathcona samples 44Table 33 Grain sizes (µm) of the minerals identified in the Strathcona samples 45Table 34 Mineral quantities (wt%) of the samples resulting
from magnetic separation 47
Table 35 Grinding and simulated flotation conditions 47Table 36 Strathcona experimental sample grain size distribution 47Table 37 Thiosalts concentrations (g/t) generated during experiments 48Table 38 Effects of SO2 conditioning on thiosalts generation 53
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FIGURES Figure 1 Metal sulphide oxidation to sulphate generalized path A-1Figure 2 Experimental set-up for the thiosalts generation studies A-2Figure 3 Representative backscattered electron (BSE) photomicrograph
of SAR-Ore A-3
Figure 4 BSE photomicrograph of SAR-Ore A-3Figure 5 BSE photomicrograph of SAR-Ore A-4Figure 6 Representative BSE photomicrograph of various sulphides and
gangue minerals in LVR-Ore A-4
Figure 7 BSE photomicrograph of a composite particle made of pyrite, chalcopyrite and quartz
A-5
Figure 8 Backscattered electron (BSE) photomicrograph of an unknown sulfosalt in sphalerite, magnesian siderite and quartz
A-5
Figure 9 BSE photomicrograph of a rhombohedral magnesian siderite grain A-6Figure 10 BSE photomicrograph of liberated pyrrhotite displaying variable
sizes A-6
Figure 11 BSE photomicrograph of liberated pyrite and chalcopyrite grains LVR5-LLL
A-7
Figure 12 BSE photomicrograph of carbonate grains in LVR5-LLL A-7Figure 13 BSE photomicrograph showing chalcopyrite attached to an anhedral
pyrite grain in LVR7-MMM A-8
Figure 14 Model adequacy for the pyritic ore A-9Figure 15 Model adequacy for the pyrrhotitic ore A-9Figure 16 Effect of pulp temperature on thiosalts generation A-10Figure 17 Effect on pH on thiosalts generation during flotation under constant
temperature and residence time A-11
Figure 18 Effect of pH and temperature on thiosalts generation for residence time of 22 minutes
A-12
Figure 19 Effect of residence time on thiosalts generation A-13Figure 20 Overall effects of pH, temperature and residence time on total
thiosalts generation (pyritic ore) A-14
Figure 21 Overall effects of pH, temperature and residence time on total thiosalts generation (pyrrhotitic ore)
A-14
Figure 22 Effect of grinding media composition on total thiosalt generation by the pyritic ore at natural pH
A-15
Figure 23 Effect of grinding media composition on total thiosalt generation by the pyrrhotitic ore at natural pH
A-16
Figure 24 Comparison of grinding media effects on pyritic and pyrrhotitic ores based on total thiosalts generation at natural pH
A-16
Figure 25 Change in grinding mill discharge pH as a function of time addition rate
A-17
Figure 26 Effect of lime controlled grinding pH on thiosalts generation A-18Figure 27 Experimental continuous grinding, classification and flotation A-19Figure 28 Distribution of the total thiosalts among the major process and the
ore A-20
Figure 29 The PC controlled automatic flotation cell A-21
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FIGURES (Cont’d)
Figure 30 Semi-batch test flowsheet used to investigate thiosalts generation in various circuits (Louvicourt)
A-22
Figure 31 Distribution of thiosalts generated among sub processes A-23Figure 32 Semi-batch test flowsheet used to investigate thiosalts generation in
various circuits (Strathcona) A-24
Figure 33 Proportions of total thiosalts generated in various process circuits A-25Figure 34 Sample preparation, grinding and flotation simulation of Louvicourt
pyritic Cu-Zn ore A-26
Figure 35 Sample preparation, grinding and flotation simulation of Strathcona pyrrhotitic Cu-Ni ore
A-27
Figure 36 BSE photomicrograph of pyrite grains attached to an encapsulated in gangue
A-28
Figure 37 BSE photomicrograph of a pyrite grain attached to an encapsulated in gangue. Note the sharp grain boundaries on exposed surfaces of pyrite grains
A-28
Figure 38 Effect of mineralogical composition of Louvicourt ore on total thiosalt generation rate
A-29
Figure 39 Dissolved oxygen concentration and pulp oxidation-reduction potential data for LVT4
A-30
Figure 40 Change in pulp oxidation-reduction potential with residence time A-31Figure 41 Louvicourt test. Change in pH with resident time A-32Figure 42 Pulp conductivity A-33Figure 43 Representative BSE photomicrograph of various sulphides from
SAMM-HEAD A-34
Figure 44 Representative BSE photomicrograph of various sulphides in SAMM6
A-34
Figure 45 Representative BSE photomicrograph of various gangue minerals in SAMM5
A-35
Figure 46 BSE photomicrograph of pyrrhotite surrounded by fine particles of pyrrhotite
A-35
Figure 47 Representative BSE photomicrograph of pyrrhotite SAMM5 A-36Figure 48 Effect of mineralogical composition of Strathcona ore on total thiosalt
generation rate A-37
Figure 49 Change in rate of total thiosalt generation (Strathcona core) A-38Figure 50 Thiosalts generation rate as a function of residence time interval and
sulphide mineral content of samples A-39
Figure 51 Comparison of correlations between initial thiosalts generation rate and mineral quantities (first 15 minutes of processing)
A-40
Figure 52 Comparison of correlations between initial thiosalts generation rate and mineral quantities (last 20 minutes of processing)
A-41
Figure 53 Thiosalts generation rate as a function of bulk sulphur assays (%) A-42Figure 54 Change in pulp oxidation-reduction potential A-43Figure 55 Change in pulp pH A-44Figure 56 Effect of xanthate addition rate on thiosalts generation A-45
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INTRODUCTION
Thiosalts, which are defined as metastable sulphur oxyanions containing S-S bonds, are
produced in varying quantities during processing of sulphide ores. Primary mechanism for
the formation of thiosalts is the oxidation of sulphide minerals. Thiosalts are intermediate
products formed during the conversion of sulphides to sulphates; therefore, they are
considered as metastable and the reactions producing thiosalts can be reversible.
Earlier studies (e.g. Wasserlauf and Dutrizac 1982, Rolia and Tan 1985, Thiosalts Workshop
notes, Montreal, June 1996) indicated that the milling processes such as grinding,
conditioning, flotation and dewatering contribute to thiosalts generation. More specifically,
the following factors promoted the generation of thiosalts in mill circuits: (1) high sulphide
content of ore, (2) finer grain size, (3) alkaline grinding solution, (4) higher dissolved oxygen
in grinding solution, (5) longer retention time, (6) higher temperature, (7) lower pulp density,
(8) increased agitation rate during flotation, and (9) SO2 additions. In addition, it was found
that airflow had a marginal effect on the production of thiosalts. A study conducted by
Noranda Mining and Exploration in a Brunswick concentrator, however, was unable to
identify a specific unit process or reagent that generated more thiosalts than others (Thiosalts
Workshop notes, Montreal, June 1996).
The presence of thiosalts in effluents causes the potential acidification of water courses.
Thus, current treatment or control practices are designed to destroy thiosalts prior to their
release to the environment. The treatment/control options include natural degradation in
ponds, liming and water recycling, subaqueous tailings disposal in impoundments and sea
disposal. Annual treatment costs range from 4 million dollars for the natural degradation
option to 72 million dollars for options involving technologies (Wasserlauf et al. 1985).
Thus, liabilities to mining companies arising due to thiosalts generation are paramount.
The magnitude of thiosalts production vary with the location and type of operation; however,
environmental and economic implications of thiosalts disposal are such that identification of
processes that contribute to thiosalts production is of profound importance to mining
companies. Development of predictive and control measures can not be properly achieved
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without establishing sound relationships between the mill processes and thiosalts generation.
If the effects of unit operations on mineral surface chemistry and on thiosalts generation are
better understood, then appropriate control or prevention measures can be designed with the
objective to minimize the formation of thiosalts, to prevent the persistence of thiosalts in
process streams or to bring the oxidation reactions to a completion before they are released to
the environment. Control or prevention measures may include the use of alternate reagents,
alternate reagent addition points, alternate process units, such as columns instead of
mechanical cells, and alternate means of reducing flotation retention times by enhancing
flotation.
The Thiosalts Consortium was set-up to respond to the following needs: (1) early
identification of the potential for an ore to generate thiosalts and (2) identification of plant
conditions that would increase the production rates of thiosalts. In order to meet these needs,
CANMET proposed a two-phased study: (1) characterization of thiosalts generation in
experimental mill circuits and development of basic information on thiosalts formation and
(2) development of prediction tools, and prevention and control measures. This study reports
the findings of the first phase of the approach.
The principal objective of this study was to identify the processes, conditions and
mineralogical characteristics that may influence the production of thiosalts during milling of
sulphide ores.
Two types of ore were investigated: pyritic Cu-Zn ore from Louvicourt and pyrrhotite-rich
Cu-Ni ore from Strathcona. The Louvicourt mill sampling was carried out on September 17-
18, 1998. A total of 35 pulp samples representing the mill circuit were taken, and pH, Eh,
dissolved oxygen and conductivity measurements were made after filtering and before the
samples were frozen. Approximately 500 kg of fresh mill feed, process water and graded
balls for ball mill operation were obtained from the Louvicourt mill on October 1 and 10,
1998. The ore has been dried, crushed and prepared for testing at CANMET facilities. Ten
pulp samples from the plant were analyzed for total thiosalts, S2O3, S3O6, S4O6, SO42-, S,
Fe3+, Fe2+, Zn, Cu, Ca, Mg, Na, and K. Results are given in Appendix A. Original sampling
at the Strathcona mill planned for October 20, 1998 was cancelled because of an emergency
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shutdown at the mill. Mill sampling was instead conducted on November 19-20, 1998. A
total of 28 pulp samples representing the mill were collected and analyzed on-site for pH, Eh,
dissolved oxygen and conductivity after filtering and before freezing the samples.
Approximately 450 kg of fresh rod mill feed, process water from Moose Lake and reclaim
water from the stock tank 129 were received from the mill plant on December 1, 1998. Ten
pulp samples from the plant were analyzed for total thiosalts S2O2-3, S3O2-
6, S4O2-6, SO4
2-, S,
Fe3+, Fe2+, Zn, Cu, Ca, Mg, Na, and K. Results are given in Appendix A.
BACKGROUND INFORMATION
Thiosalts or polythionates are a collective name for oxyanions such as S2O3
2-, S3O62-, S4O6
2-,
which are intermediate products of oxidation of S to SO42-. Although the thermodynamics of
oxidation suggests that SO42- is the only ultimate product, kinetic limitations in neutral and
alkaline media results in partially oxidized products. The oxidation route of sulphide
minerals is presented schematically in Figure 1. Equation 1 shows a more detailed sub
process of sulphide mineral oxidation (Bocharov, 1985).
2
/ 2S
2
-4e-
0
+S +2e +e0 -
SO
MS SO S O S O SO
S SO S O
S e e ne
e
e
42
22 2 2
2 32 2
4 62
42
2 632
2 32
2
2 2 40
−
− + + − − − − −
− − −
−
↑
⇒ → → →
↑ ↓
→
↓
− − −
− −
−
SO42−
Equation 1
Sulphide minerals are thermodynamically unstable in moisture. Their oxidation in aqueous
solutions can be considered as an electrochemical corrosion process for which the following
equation (Avdokhin and Abramov, 1989) applies.
∆Gτ = -nEτF < 0 Equation 2
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where Gτ is isobaric-isothermal potential of corrosion process, n is number of gram-
equivalents of substance, F is the Faraday’s constant (9.648456.104 C/mole), and Eτ is the
difference in reversible potential of the cathode and anode processes (Eτ =ϕc -ϕa ).
The spontaneous occurrence of the electrochemical corrosion of minerals is determined by
the difference in the reversible potential of the mineral (anode), ϕa, and of any oxidizing
agent (cathode), ϕc, present in the solution. Process water used during grinding and flotation
always contains ample amount of dissolved oxygen whose reversible oxidation-reduction
potential is much more positive than the potential of any mineral. Consequently, Eτ will be
positive, making the expression ∆Gτ being less than zero, a prerequisite for spontaneous
oxidation of sulphide minerals.
Majority of sulphide minerals fall in the category of compounds with partial ionic bonding
and are frequently represented as MeS where Me stands for a metal. When in contact with
water, dissolved oxygen is adsorbed at the metal anion site as represented by Equation 3.
MeS O MeS O
MeS O H O MeS O OHdiss ads
ads
+
+ + +
↔↔ + −
2 2
2 2 322 22
( ) ( )
( )
. Equation 3
Elemental sulphur which is normally present on sulphide mineral surfaces may oxidize to
thiosalts in aqueous sulphite solution (Equation 4). The sulphite ion is also a product of
surface oxidation (Equation 5). Equations 5, 6 and 7 are various routes of sulphur oxidation
(Garshteyn, Illyvieva and Baron, 1987).
MS MSS SO S Oaq0
32
2 32+ → +− −
( ) Equation 4
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MS MS
MS MS
MS MS
S O H O S O S OH
S OH SO S H O
S O SO
SO O SO
S SO S O
S SO H O H
aq
aq
aq aq aq
aq aq aq
aq aq
aq aq
aq
22 2 2 3
2 0
032 2
2
22 4
2
32
2 42
032
2 32
232
2
12
2
3 6 3
212
2 3 3
− − −
− − −
− −
− −
− −
− −
+ + → + +
+ → + + +
+ →
+ →
+ → +
+ + →
( )
( )
( ) ( ) ( )
( ) ( ) ( )
( ) ( )
( ) ( )
( )
200 3 6⇔ + −S OH
Equation 5
MSMS MS
S SO S O
S OH S SO S H O
SO O SO
aq aq
aq aq aq
aq aq aq
032
2 32
0 032 2
2
32
2 42
6 2 3
12
+ →
+ → + + +
+ →
− −
− − −
− −
( ) ( )
( ) ( ) ( )
( ) ( ) ( )
Sometimes: Equation 6
MS 2 2 2
2 4
022 2 2
2 32
2 632 2
2 32
32 2
42
2 32
4 62 4
42
0
0
S SO S O
S SO S O
SO SO
S O S O SO
e S
e e S
e
e
→ →
→ →
→
↔ →
− + + −
− − − + + −
− − −
− − − −
−
−
−
Equation 7
At relatively high concentrations, thiosulphate is complexed by Cu ions according to
Equation 8 (Skrinchenko and Shelkova, 1987):
2 6 222 3
22 3 2
34 6
2Cu S O Cu S O S O+ − − −+ → +[ ( ) ] Equation 8
All sulphide minerals are semi-conductors and, in a grinding and flotation environment, they
undergo galvanic corrosion. Galvanic corrosion or surface oxidation occurs when two (or
more) dissimilar sulphide minerals, just as in the case of metals, are brought into electrical
contact under water. When a galvanic couple forms, one of the minerals in the couple
becomes the anode and oxidizes faster than it would all by itself, while the other becomes the
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cathode and oxidizes slower than it would alone. Neither of the minerals in the couple may
oxidize by itself in grinding and/or flotation pulp depending on other conditions.
Table 1. Galvanic series of sulphide minerals
(Natarajan, 1986, Abramov, 1989) pH 4 (Kosabag and Smith 1985) Chalcocite Pyrite Noble (Cathodic), slow oxidizing Bornite Marcasite Covellite Chalcopyrite Pyrite Sphalerite Chalcopyrite Covellite Galena Bornite Pentlandite Galena Pyrrhotite Sphalerite Stainless steel media Mild steel media Active (Anodic) fast oxidizing
The Galvanic Series shown in Table 1 is a list of sulphide minerals ranked in order of their
tendency to oxidize in grinding and flotation environments. This table can be used to predict
which mineral will become the anode and how fast it will oxidize relative to the other
minerals and the steel grinding media. When two minerals on the list are in physical contact
during grinding, conditioning or flotation, the one closer to the anodic (or active) end of the
series will become the anode and oxidizes faster than the one closer to the cathodic (or noble)
end.
Suppose that pyrite, with a rest potential (i.e. the potential reached spontaneously by a
mineral electrode in a given aqueous solution) of +660 mV, is attached to galena which has a
rest potential of +400 mV. In this case, pyrite will act as the cathode and the voltage
difference between the two minerals will be 260 mV. It is this voltage difference that drives
the current flow to accelerate oxidation of the anodic mineral, galena. With their joint
presence and contact with each other during comminution and flotation, the nobler mineral in
the galvanic series will be protected from oxidation by the less noble minerals.
There are two major factors affecting the severity of galvanic corrosion. These are the
voltage differences between the two minerals and the size of the exposed area of cathodic
mineral relative to that of the anodic mineral. If the particle size distribution of the two
minerals is similar, relative abundance of the two minerals controls the oxidation rate of the
anodic mineral and hence the thiosalts generation due to cathodic effects. Oxidation of the
anodic mineral increases as the voltage difference between the cathode and anode increases
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(i.e. the further apart the minerals are in the galvanic series) and as the cathode area increases
relative to the anode area.
When two minerals in a galvanic couple are close together on the series, their voltage ranges
overlap, and either one can be the anode, depending on the exact exposure conditions. In the
case of complex ore where more minerals with different rest potentials come in contact with
each other, the situation becomes more complex and the oxidation pattern will depend on
surface area ratios of the sulphide minerals present in the ore. An electrical potential will
develop between the large area of the cathode mineral and the small area of the anode. Rapid
pitting of the active mineral occurs at the point of contact. A small sphalerite inclusion in a
larger pyrite particle for instance accelerates sphalerite oxidation thus mobilizing more
sulphur, which is a precursor to thiosalts formation. Lack of liberation may become a cause
for concern not only due to poor metallurgical performance but also from an environmental
point of view.
Chalcopyrite-pentlandite-pyrrhotite ore
The grinding mill (if not lined) and the steel rods produce steel debris during grinding. This
fine metallic debris may interact with the ground mineral particles. If the media is mild steel,
magnetic minerals such as pyrrhotite can be coated with the iron debris which may affect the
rate and extent of pyrrhotite oxidation by lowering the rest potential of the mineral. When it
comes in contact with chalcopyrite or pentlandite, the Fe-coated pyrrhotite may assume a
mixed potential and become more anodic and, accordingly, may oxidize faster. As a
consequence, oxidation of chalcopyrite and pentlandite may even slow down. On the other
hand, with a decrease in the difference of rest potentials of the Fe-coated pyrrhotite and
grinding media, the oxidation of pyrrhotite due to galvanic interactions becomes less severe.
Under certain operating conditions, coating of pyrrhotite with grinding media debris may be
insufficient to lower the rest potential of the mineral. Since the rest potential of mild steel is
lower than that of stainless steel, pyrrhotite may be more protected against oxidation by the
mild steel media. Oxygen depletion resulting from the oxidation of steel debris also causes
changes in the rest potential.
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A reaction product on the surface of pyrrhotite may be of a non-soluble nature and could alter
the rest potential of pyrrhotite permanently. Mild steel depletes dissolved oxygen from the
solution. Overall, more thiosalts are likely to be generated by stainless steel than by mild
steel media.
The following are possible reactions during grinding of a pyrrhotitic ore (Pozzo and Iwasaki,
1987).
At the steel anode:
Fe Fe e→ ++ −2 2 Equation 9
At pyrrhotite cathode (Cheng and Iwasaki, 1992)
FeS H O Fe SO H eS S O SO
+ → + + +
→ →
+ − + −
− −2
24
2
02 3
24
2
8 8 Equation 10
At chalcopyrite cathode:
12
2 22 2O H O e OH+ + →− − Equation 11
Presence of chalcopyrite should enhance the oxidation of pyrrhotite and pentlandite.
However, the presence of the steel debris that is magnetically attached to pyrrhotite particles
lowers the rest potential. In the case of the Strathcona ore, there is a possibility that the
thiosalts generation rate increases in proportion to increases in certain sulphide mineral
content even if the overall sulphur content of the ore doesn’t change significantly.
Pyrite-chalcopyrite-sphalerite ore
In this case, the grinding media debris is less attracted by the non-magnetic sulphide
minerals. Pyrite could act as the cathode whereas sphalerite, chalcopyrite and steel debris act
as the anode.
At the contact of the grinding media (steel anode) with sphalerite, chalcopyrite and pyrite, the
following reaction takes place:
2e Fe Fe -2 += + Equation 12
At the sphalerite, chalcopyrite and pyrite cathodes, oxygen is reduced to hydroxide:
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2OH 2e OH O 21 ,, --
2222 →++Surface
FeSCuFeSZnS Equation 13
On the other hand, if the minerals are in contact more with each other than with the grinding
media, the following changes occur. Pyrite becomes the cathode when it is in contact with
either sphalerite or chalcopyrite. Chalcopyrite becomes the cathode when it is in contact with
sphalerite only.
For pyrite in contact with either minerals the anodic reaction can be expressed as:
−+ ++→ eSZnZnS 202 Equation 14
For chalcopyrite in contact with sphalerite, the anodic reaction is:
−+ ++→ eSFeCuFeS 42 02
2 Equation 15
The corresponding cathodic reaction is the reduction of oxygen on the pyrite surface as
above.
THE INFLUENCE OF pH, TEMPERATURE AND RESIDENCE TIME ON THIOSALTS GENERATION
The effects of conditioning (grinding) pH, temperature and residence time were investigated
under controlled laboratory conditions for both sulphide ores. Besides aeration rate and
grinding media type, these three factors are known to have the capacity to influence thiosalts
generation (Cotton, Spira and Wheeland, 1977). To determine how these factors affect
thiosalts generation and investigate possible interactions between these factors, a 23-Factorial
design of experiments with centre-point replicate was set up. A statistical design of
experiments was selected since many unknown factors may affect interpretations of one-at-a-
time type of experiments and small changes in responses often result from changes in
uncontrolled operating parameters. Significance of such small changes can not be positively
determined unless they are subjected to statistical analysis. Ranges of the factors investigated
are pH 7.5 to 9.5; temperature: 10 to 25°C; and residence time: 10 to 30 minutes. Within the
factor space studied, residence time of up to 30 minutes increased thiosalts concentration
only marginally in the case of the pyrrhotitic ore. A change in pH from 7.5 to 9.5 had the
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same effect as raising the pulp conditioning temperature from 10 to 25°C. There was no
significant interaction between the three factors.
Test Methodology
The set-up used for this investigation is shown in Figure 2. A 76x210 mm plexiglass tube
was used for the test. The bottom was fitted with a stainless steel plate of very fine porosity
through which air was fed. Air flow, pH and temperature were controlled by a PC. Air was
fed at a rate of 0.25 L/min through a mass flow controller. The pH control was on/off type
using two peristaltic pumps: one for lime addition and the other for acid. Temperature was
controlled using a U-shaped 4-mm stainless tube through which cold/hot water flows.
Temperature was measured using a thermocouple. Information about pH, temperature,
oxidation-reduction potential, air flow rate and conductivity of the pulp was collected on-line
by a PC.
Initial tests conducted indicated that it was difficult to obtain reproducible results on thiosalts
generation due to difficulties in monitoring and controlling certain process factors. For
instance, minor inconsistencies, such as grinding temperature, delays in collecting samples
and preparation for testing and minor changes in grinding pH, that are acceptable in standard
flotation tests, caused significant differences in the amount of thiosalts generated. Evidently,
normal procedures used for grinding of ores for flotation testing was not adequate. When a
positive identification of factor effects became difficult, an elaborate procedure for preparing
samples was worked out to provide a uniform feed for each test. The amount of sample used
for each test was scaled down from 1650 g to a manageable size of 300 g due to cost
considerations. The samples weighing 1650 g were ground with 840 mL of temperature-
adjusted tap water. The pulp was filtered immediately and the filtrate was aerated with
nitrogen until the dissolved oxygen concentration dropped to 0.5 ppm to prevent further
oxidation of thiosalts species. The filter cake was split into 5 portions and each portion was
vacuum-sealed in an aluminum bag for storing in freezer. Three batches of samples were
ground for each ore to prepare sufficient number of feeds. The filtrate from the three
grindings was mixed and split into 15 equal amounts of solution. Each sample was
transferred to 0.5 L plastic container purged with nitrogen, and instantly frozen with liquid
nitrogen and stored in freezer. Before testing, the aluminum bag containing frozen solid
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sample and the bottle containing frozen solution, with its tight lid in place, were warmed up
in a temperature-controlled water bath. As soon as the working temperature was attained, the
solution and the solid samples were transferred to the cell where the temperature was
maintained automatically.
Feed Sample Compositions
Bulk chemical compositions of the ore samples are given in Table 2. The Strathcona ore
(ST1 and ST2) is characterized by high Fe, S and SiO2 concentrations. Average Cu and Ni
levels of the ore are 4.3 and 2.7% respectively. Sulphate concentration of the ore is 0.5% and
the CO2 level is below the detection limit of 0.05%. Solid samples that resulted from the
experiments do not display significant variations from these levels.
Table 2. Bulk chemical analysis of the Strathcona (ST)
and Louvicourt (LV) ore samples ST1 ST2 LV1 LV2 SiO2 28.24 28.67 32.94 34.23 TiO2 0.33 0.32 na na Al2O3 7.58 7.64 9.37 9.56 MnO 0.08 0.08 0.12 0.13 MgO 2.04 2.02 5.01 5.07 CaO 2.99 3.06 1.90 1.99 Na2O 1.73 1.78 0.32 0.36 K2O 0.58 0.57 0.65 0.65 CO2 <0.05 <0.05 4.17 4.17 SO4 0.48 0.47 0.25 0.28 Fe 28.88 28.81 20.27 20.66 Ni 2.70 2.66 na na Cu 4.29 4.25 3.92 4.04 Pb na na <0.03 <0.03 Zn na na 0.16 0.16 Ssul 20.17 19.52 18.36 18.31 Total 93.10 92.93 97.45 99.61 Results in wt %; Ssul: sulphide sulphur; na: not analyzed
The Louvicourt ore samples (LV1 and LV2) are characterized by high SiO2, Fe and S
concentrations. Aluminum concentrations (as Al2O3) are approximately 9.5%. MgO levels
are around 5%. Sulphate concentrations are lower than 0.3% and the CO2 levels are 4.2%.
Copper is approximately 4% and Zn is 0.16%.
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Mineralogical Composition of the Strathcona Ore
The Strathcona ore consists predominantly of pyrrhotite, chalcopyrite, pentlandite, quartz,
muscovite and Ca-pyroxene (Table 3). Pyrrhotite is the dominant sulphide mineral in all the
samples. Pyrite, sphalerite, galena and bornite occur in trace quantities. Chlorite, K-feldspar,
amphibole, epidote and biotite are the other silicate minerals present in moderate to minor
quantities. In addition, magnetite, ilmenite, apatite, gypsum and Fe-oxyhydroxides are
present. A representative photomicrograph is given in Figure 3.
Table 3. Minerals identified, their relative abundances and particle
sizes in the Strathcona ore Mineral Abundance Particle size (µm)
Pyrrhotite +++ 1-1500 (25-300) Chalcopyrite +++ 1-1500 (25-200) Pentlandite ++ 1-1500 (25-150) Magnetite/Ilmenite ++ 1-1500 (100-400) Pyrite + 10-50 Sphalerite + 1-1500 (100-200) Galena + 1-150 (1-20) Bornite - 10-20 Quartz +++ 1-1500 (25-300) Potassium feldspar +++ 1-1500 (25-300) Pyroxene ++ 25-150 Muscovite + 20-125 Chlorite +++ 20-125 Amphibole ++ 20-150 Epidote ++ 20-100 Biotite + 20-50 Gypsum + 10-30 Iron oxyhydroxide + 25-50 Apatite + 5-10 +++ :major; ++: minor; +: trace; -: not present ; Numbers in brackets represent the size ranges of the majority of grains.
Pyrrhotite occurs as liberated grains and, less commonly, in association with chalcopyrite,
pentlandite and magnetite/ilmenite (Figure 4). Pyrrhotite-gangue associations were observed;
however, they are generally restricted to the fine-grained fraction. Coarse pyrrhotite grains
that are liberated frequently display exsolution flames of pentlandite. Chalcopyrite was
observed primarily as liberated grains and less commonly in association with pyrrhotite,
pentlandite, and gangue minerals. More rarely chalcopyrite occurs in the form of exsolution
blebs in sphalerite. Pentlandite exists primarily as liberated grains and as exsolution lamellae
or flames in pyrrhotite. Rare occurrences of pyrrhotite intergrown with chalcopyrite were
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also observed. Pentlandite also occurs in association with feldspar and quartz. Galena was
observed as inclusions in chalcopyrite and to a lesser extent in sphalerite. Rare occurrences
of liberated galena were also observed. Pyrite, magnetite and ilmenite occur primarily as
liberated grains. Pyrite also occurs in association with pyrrhotite and chalcopyrite. Coarse
pyrrhotite and chalcopyrite grains sometimes display a relatively fine-grained rim that
consists of angular fragments mineralogically identical to the grain they surround (Figure 5).
The angular nature of the fragments that comprise the halo suggest that it is the result of a
mechanical process rather than being chemical. Major liberated sulphide grains (i.e.
pyrrhotite, chalcopyrite and pentlandite) range from less than 1 µm to 1.5 mm in size;
however, the majority of the grains fall between 40 and 200 µm.
Quartz, plagioclase feldspar, amphibole, epidote, pyroxene, chlorite and muscovite are the
most abundant gangue minerals in the ore sample. Gangue minerals often occur as
composite particles sometimes locking and encapsulating various sulphides.
Mineralogical Composition of the Louvicourt Ore
The Louvicourt ore mineralogy and average grain sizes of the minerals after grinding are
summarized in Table 4. Sulphide and gangue minerals occur in equal proportions. The
sample is made up of grains that range in size from less than 1 µm to 1.5 mm with the
majority falling in the 50 to 125 µm range (Figure 6). Pyrite occurs primarily as liberated
grains displaying subhedral outlines. Pyrite commonly occurs in association with
chalcopyrite. Composite particles of pyrite-chalcopyrite-gangue association are also present
(Figure 7). Less commonly, pyrite occurs as inclusions in chalcopyrite. In order of
decreasing abundance, chalcopyrite occurs as subhedral to anhedral liberated grains,
inclusions in pyrite, attached to pyrite, inclusions in gangue minerals and inclusions in
sphalerite. Sphalerite occurs as liberated grains, attached to chalcopyrite and gangue-
chalcopyrite composites, in order of decreasing abundance. Sphalerite may contain
exsolution blebs of chalcopyrite. Other sulphides listed in Table 4 are very rare and warrant
only a cursory mention. Galena, native bismuth, pyrrhotite and an unknown sulphosalt,
having an approximate mineral composition of Fe6Sb7S7, occur as fracture-fillings in
sphalerite-carbonate composites (Figure 8). A small gold grain measuring approximately
2 µm was found as encapsulated in pyrite.
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Quartz, magnesian siderite, chlorite and muscovite are the most abundant gangue minerals.
Carbonate grains display subhedral to euhedral outlines, some of which have well-developed
crystal habit (Figure 9). Magnetite, ilmenite, and rutile occur as liberated grains.
Table 4. Minerals identified, their relative abundances and
particle sizes in the Louvicourt ore Mineral Abundance Particle size (µm)
Pyrite +++ <1500 (50-200) Chalcopyrite +++ <500 (50-200) Magnetite/Ilmenite + 25-50 Pyrrhotite + <100 (2-50) Sphalerite + 25-100 Galena + 1-10 Arsenopyrite + 25-40 Gold + 2 Native Bi + 10-15 Unknown Sulphosalt + 10-15 Quartz +++ 1-1500 (25-200) Mg-siderite ++ 2-1000 (25-200) Ankerite +++ 25-75 Calcite + 25-75 Dolomite + 25-75 Muscovite +++ 20-150 Chlorite +++ 1-500* Amphibole + 1-100 Potassium feldspar ++ 25-200 Plagioclase feldspar + 25-200 Rutile + 5-20 Apatite + 5-15 +++ :major; ++: minor; +: trace; -: not present ; Numbers in brackets represent the size ranges of the majority of grains;
Experiments on Thiosalts Generation
The amount of thiosalts generated, expressed as g/t of total thiosalts concentration for each
test, is given in Table 5.
Bulk chemical compositions of the Strathcona samples that resulted from the batch
experiments (LLL1, LLL2, MMM1 MMM2, HHH1 and HHH2) are given in Table 6. These
samples do not display significant variations from the feed composition.
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Table 5. Test design parameters and results
Total Thiosalts Generated (g/t) TEST
ID Factor A
pH Factor B
Temperature (°C)
Factor C Residence time
(min) Louvicourt Strathcona
1 8.5 17.5 20.0 34 216 2 9.5 10.0 10.0 45 85 3 9.5 10.0 30.0 51 203 4 7.5 10.0 10.0 30 59 5 9.5 25.0 30.0 75 284 6 7.5 25.0 10.0 47 160 7 8.5 17.5 20.0 50 174 8 9.5 25.0 10.0 67 206 9 7.5 25.0 30.0 49 267 10 7.5 10.0 30.0 31 90 11 8.5 17.5 20.0 59
Table 6. Bulk chemical analysis of the experimental samples LLL1 LLL2 MMM1 MMM2 HHH1 HHH2 SiO2 29.09 28.88 29.52 28.88 29.09 29.52 TiO2 0.32 0.32 0.33 0.33 0.33 0.32 Al2O3 7.69 8.03 8.77 7.92 7.75 7.84 MnO 0.08 0.09 0.10 0.09 0.08 0.08 MgO 1.97 2.07 3.48 2.01 1.99 2.04 CaO 2.95 2.92 3.01 2.95 3.01 3.04 Na2O 1.82 1.81 1.86 1.82 1.86 1.85 K2O 0.58 0.59 0.59 0.59 0.59 0.59 CO2 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 SO4 0.33 0.32 0.29 0.28 0.28 0.26 Fe 27.68 29.09 24.85 28.37 27.37 28.00 Ni 2.57 2.69 1.43 2.64 2.56 2.61 Cu 3.99 4.19 4.06 4.08 3.99 4.04 Ssul 19.15 19.37 19.28 19.99 19.16 18.93 Total 91.67 93.49 92.09 93.22 91.51 92.47 Results in wt %; Ssul: sulphide sulphur
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The Louvicourt samples that resulted from the experiments (LLL1, LLL2, MMM1, MMM2,
HHH1 and HHH2) are compositionally similar to the feed (Table 7).
Table 7. Bulk chemical analyses of the Louvicourt samples resulted from batch experiments
LLL1 LLL2 MMM1 MMM2 HHH1 HHH2
SiO2 34.44 34.66 34.87 35.30 34.23 34.66 Al2O3 9.77 9.75 9.47 9.56 9.54 9.47 MnO 0.13 0.13 0.13 0.13 0.13 0.13 MgO 4.92 4.98 4.92 4.87 4.86 4.91 CaO 1.85 1.86 1.86 1.90 1.87 1.89 Na2O 0.59 0.39 0.38 0.40 0.54 0.35 K2O 0.67 0.66 0.67 0.66 0.66 0.66 CO2 3.96 4.15 4.10 3.96 4.14 4.17 SO4 0.19 0.21 0.19 0.19 0.20 0.22 Ssul 17.86 17.75 18.12 17.13 17.96 17.67 Fe 19.60 19.97 19.67 19.51 19.68 19.86 Cu 3.65 3.73 3.65 3.66 3.65 3.70 Pb <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 Zn 0.16 0.17 0.16 0.16 0.16 0.17 Total 97.80 98.41 98.19 97.44 97.63 97.85 Results in wt %; Ssul: sulphide sulphur
Mineralogical Composition of the Strathcona Samples
Similar to the feed mineralogy, the Strathcona samples that resulted from batch experiments
consist predominantly of pyrrhotite, chalcopyrite, pentlandite, quartz, muscovite and Ca-
pyroxene. Pyrrhotite is the dominant sulphide mineral in all the samples. Pyrite, sphalerite,
galena and bornite occur in trace quantities. Mineralogy of the Strathcona samples is
summarized in Table 8. This suite of Strathcona samples exhibits only minor differences in
the relative sulphide abundance from sample to sample.
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Table 8. Minerals identified, their relative abundances and particle sizes in the Strathcona samples
abundance particle size (µm) Mineral
SAR4-LLL SAR7-MMM SAR5-HHH SAR4-LLL SAR7-MMM SAR5-HHH
Pyrrhotite +++ +++ +++ 1-125 (20-40) 1-125 (15-30) 1-150 (15-30) Chalcopyrite +++ +++ +++ 1-125 (20-40) 1-125 (15-30) 1-150 (15-30) Pentlandite ++ ++ ++ 1-125 (10-40) 1-125 (10-30) 1-75 (10-30) Magnetite/Ilmenite + + + 20-40 20-40 20-40 Pyrite + + + 10-25 10-25 10-20 Sphalerite + + + 20-40 20-40 20-40 Galena + - + 1-10 1-10 1-10 Bornite + - - 10-20 Quartz +++ +++ +++ 1-125 (25-75) 1-125 (25-50) 1-150 (25-50) Potassium feldspar +++ +++ +++ 1-125 (25-75) 1-125 (25-50) 1-75 (25-50) Pyroxene ++ ++ ++ 25-50 10-25 10-25 Muscovite + + + 20-50 20-50 25-50 Chlorite +++ +++ +++ 20-50 20-50 25-50 Amphibole ++ ++ ++ 20-75 20-75 25-100 Epidote ++ ++ ++ 25-50 25-50 25-50 Biotite + + + 10-40 10-30 10-40 Gypsum + - - 10-25 Iron oxyhydroxide + + + 25-50 25-40 25-50 Apatite + + + 5-10 5-10 5-10 +++ :major; ++: minor; +: trace; -: not present
SAR4-LLL
The descriptive mineralogy of this sample is similar to that of the ore sample. Sulphides
range in size from <1 µm to 120 µm; however, the majority of the grains are between 15 and
50 µm. Relatively coarse liberated sulphide grains occasionally display evidence of
mechanically created deformation halos similar to that observed in the ore sample.
Composite particles commonly consist of pyrrhotite, chalcopyrite and a variety of gangue
minerals. There is no apparent evidence of dissolution or alteration along grain margins or
microfractures in sulphides. Quartz, feldspar, amphibole, epidote, pyroxene, and muscovite
are the dominant silicates in this sample. Chlorite is a minor phase. Silicates are generally
anhedral to subhedral and show no evidence of alteration along their grain boundaries. Trace
amounts of liberated iron oxyhydroxide grains are present in this sample.
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SAR7-MMM
This sample is mineralogically similar to SAR4-MMM. Sulphides range in size from 1 µm
to 100 µm; however, the vast majority of grains are between 10 and 50 µm. Sulphides are
anhedral to subhedral and show no apparent evidence of dissolution. In addition, grain
boundaries between different sulphide minerals show no evidence of alteration or
replacement. Quartz, plagioclase feldspar, amphibole, epidote, pyroxene and chlorite are the
dominant silicate phases in this sample. Biotite and muscovite are present as minor phases.
Silicate particles are generally anhedral and subhedral and devoid of apparent dissolution
features.
SAR5-HHH
Mineralogy of this sample is similar to those of SAR4-MMM and SAR7-LLL. Sulphides
appear to display a higher degree of liberation than that exhibited in the other samples (ORE,
SAR4-LLL, SAR7-MMM). Sulphide particles range from less than 1 µm to 100 µm with the
majority being between 15 and 30 µm. Fewer coarse-grained sulphides exhibit rims of
agglomerations of finer particles observed in the other samples (Figure 10). Sulphides do not
display any apparent evidence of alteration along the grain boundaries with other sulphides.
Silicate mineralogy is similar to that described for SAR7-HHH with the exception of minor
amounts of calcite. Feldspars are anhedral to subhedral with fresh particle boundaries.
Mineral Quantities
It is assumed that ilmenite is responsible for the bulk Ti concentrations. Accordingly,
ilmenite mode was calculated based on Ti and Fe tied to ilmenite and was subtracted from
total Fe before employing multiple regression techniques and mass balance calculations.
Only pyrrhotite, pentlandite and chalcopyrite, as sulphide minerals, were considered in the
calculations. Sulphide minerals that are present in trace or minor quantities were excluded
from the calculations. The following mineral compositions, based on theoretical mineral
formulas or semi-quantitative energy-dispersive microanalysis, were used in the calculations:
pyrrhotite: FeS; pentlandite: Ni4.5Fe4.5S8; chalcopyrite: CuFeS2; quartz: SiO2; muscovite:
K2Al6Si6O20(OH)4; chlorite: Mg4.6Fe5.4Al4.4Si5.8O20(OH)16; Ca-pyroxene:
Mg0.8Ca0.8Fe0.4Al0.1Si2O6; and epidote: Ca2FeAl2Si3O13.
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Pyrrhotite quantities vary from about 29 to 33% (by weight) (Table 9). Chalcopyrite is the
second most abundant sulphide with quantities in the 13 to 15% range. Pentlandite occurs in
quantities varying from 7 to 9%. Quartz and muscovite together make up approximately
30% of the samples. Ca-pyroxene is present in concentrations that are approximately 9%
whereas epidote forms approximately 6% of the samples. These mineral quantities are
relatively uniform among the ores and the processed samples.
Table 9. Mineral quantities (wt%) of the feed and experimental samples
ORE1 ORE2 LLL1 LLL2 MMM1 MMM2 HHH1 HHH2 Quartz 15.2 15.4 16.4 15.1 14.0 15.8 16.3 16.2 Muscovite 14.4 14.1 14.7 14.9 19.6 15.2 14.9 14.7 Ca-pyroxene 9.5 9.5 9.2 9.5 14.9 8.9 9.3 9.6 chlorite 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 epidote 5.1 6.1 5.6 5.9 0.0 5.2 5.6 6.0 ilmenite 0.6 0.6 0.6 0.6 0.7 0.6 0.7 0.6 pyrrhotite 32.9 32.8 32.1 33.2 29.1 32.3 31.6 32.1 pentlandite 8.9 8.4 8.5 8.2 6.8 8.9 8.7 8.4 chalcopyrite 13.5 13.1 12.9 12.6 15.0 13.1 13.0 12.5 Total 100 100 100 100 100 100 100 100
Mineralogical Composition of the Louvicourt Samples
The mineralogy of the Louvicourt samples and average grain sizes of the minerals are
summarized in Table 10. There is no significant mineralogical difference among the
samples.
LVR5-LLL
Mineralogy of this sample is similar to that of the ore sample. Sulphide and gangue minerals
occur in roughly equal proportions. Sulphide minerals range in size from approximately 1 to
120 µm; however, the majority of the grains fall in the 10 to 30 µm range. Liberated grains
of pyrite and chalcopyrite exhibit no apparent evidence of alteration along their grain margins
(Figure 11). Grain boundaries between pyrite and chalcopyrite are pristine and show no
evidence of reaction. Similarly, pyrrhotite and sphalerite particles do not display any
evidence of oxidation. Carbonates do not show any apparent evidence of significant
dissolution (Figure 12). This is evidenced by the preservation of rhombohedral crystal
boundaries exhibited by many of the magnesian siderite particles.
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Table 10. Minerals identified, their relative abundances and particle sizes in the Louvicourt samples
abundance particle size (µm) Mineral
LVR5-LLL LVR7-MMM LVR6-HHH LVR5-LLL LVR7-MMM LVR6-HHH
Pyrite +++ +++ +++ <200 (20-50) <150 (25-75) <200 (25-75) Chalcopyrite +++ +++ +++ <100 (10-40) <100 (25-50) <125 (25-50) Magnetite/Ilmenite + + + 15-30 20-75 25-100 Pyrrhotite - + + <20 10-30 10-40 Sphalerite + + + 2-20 25-75 25-100 Galena + - - 1-5 - - Arsenopyrite - - - - - - Gold - - - - - - Native Bi - - - - - - Unknown Sulphosalt - - - - - - Quartz +++ +++ +++ 1-120 (10-50) 1-150 (25-75) 1-200 (25-75) Mg-siderite ++ ++ ++ 1-100 (5-50) 1-150 (25-50) 1-150 (25-75) Ankerite +++ +++ +++ 5-25 10-50 10-50 Calcite + + + 5-25 10-50 10-50 Dolomite + + + 5-25 10-50 10-50 Muscovite +++ +++ +++ 5-50 5-75 10-100 Chlorite +++ +++ +++ 5-50 5-75 10-100 Amphibole 5-25 5-50 5-50 Potassium feldspar ++ ++ ++ 5-100 10-100 10-125 Plagioclase feldspar + + + 5-100 10-100 10-125 Rutile + + + - - - Apatite + - - - - - +++ :major; ++: minor; +: trace; -: not present; Numbers in brackets represent the size ranges of the majority of grains;*: as part an agglomerate
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LVR7-MMM
Mineralogy of this sample is similar to LVR-ORE and LVR5-LLL. Only the differences are
described here. Pyrite and chalcopyrite particles range in size from approximately 1 to
125 µm; however, the majority of particles are between 10 and 40 µm. Particle surfaces
reveal no evidence of oxidation. Similarly, the mutual grain boundaries between pyrite and
chalcopyrite show no discernible evidence of reaction (Figure 13). Of the gangue minerals
listed in Table 10, the carbonates are considered to be the best measure of degree of reactivity
or dissolution. Carbonates are similar to those observed in LRV5-LLL and show no evidence
of significant dissolution; however, some grains display somewhat ragged edges, which may
be interpreted as an indication of the initial stages of dissolution.
LVR6-HHH
Sulphide mineralogy is similar to that described for LVR5-LLL and LVR7-HHH. The
majority of pyrite and chalcopyrite particles ranges from 10 to 40 µm; however grains as
large as 120 µm were observed. Sulphides show no obvious evidence of dissolution along
the grain edges or boundaries with other sulphides. Carbonate minerals have maintained
their subhedral to euhedral form, although some rugged edges may be due to dissolution.
Mineral Quantities
It is assumed that chalcopyrite is the only Cu-bearing mineral and all the Zn is tied to
sphalerite. Following the calculation of chalcopyrite (based on its theoretical formula
CuFeS2) and sphalerite, assuming that it does not contain Fe (i.e. ZnS), the remaining S is
assigned to pyrite. Iron that is tied to pyrite was subtracted from the bulk Fe concentrations
and the residual Fe and other elements were used in the calculation of the other minerals
present in the samples by MODAN (Paktunc, 1998). The following mineral compositions,
based on either theoretical mineral formulas or semi-quantitative energy-dispersive X-ray
microanalysis, were used in the calculations: quartz: SiO2; muscovite:
K1.7Na0.2Fe0.1Al5.8Si6O20(OH)4; plagioclase: Ca0.05Na0.95Al1.05Si2.95O8; chlorite:
Mg6Fe3.4Al5.2Si5.4O20(OH)16; magnesian siderite: Fe0.38Mg0.62CO3; ankerite:
Ca0.5Mg0.38Fe0.12CO3; and magnetite: Fe3O4. The results are given in Table 11.
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Table 11. Mineral quantities (wt%) of the feed and experimental samples recalc ORE1 ORE2 LLL1 LLL2 MMM1 MMM2 HHH1 HHH2
quartz 22.9 23.0 22.6 23.2 24.3 24.4 22.9 24.0 muscovite 13.7 13.2 13.4 14.0 13.6 13.5 13.5 13.8 plagioclase 5.2 5.4 7.7 6.0 5.7 5.9 7.3 5.5 chlorite 20.6 20.4 20.2 19.8 19.9 19.9 19.4 19.6 Mg-siderite 2.7 2.3 2.5 2.7 2.7 2.1 2.8 2.7 ankerite 7.6 7.6 7.2 7.2 7.3 7.4 7.3 7.4 magnetite 0.9 1.5 0.6 1.3 0.4 1.6 0.7 1.3 pyrite 18.4 18.2 18.3 18.0 18.6 17.5 18.4 18.0 chalcopyrite 7.9 8.1 7.4 7.6 7.4 7.5 7.4 7.5 sphalerite 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Statistical Analysis and Discussion of Effects of Parameters Studied on Thiosalts Generation The results are statistically analyzed to determine the most significant effects. Three main
effects (pH, temperature and residence time), three 2-Factor interaction effects (pH vs
temperature, pH vs residence time, temperature vs residence time), and one 3-Factor
interactions (pH vs temperature vs residence time) can be determined from this series of tests
(Table 12).
Table 12. Contributions by factors and their interactions to thiosalts generation when factor settings change from low to high levels investigated
Effect of changing From low to high
setting
Contribution % Model Coefficient
Term Pyritic
ore Pyrrhotitic
ore Pyritic
ore Pyrrhotitic
ore Pyritic
ore Pyrrhotitic
ore Intercept 81.54 236.44pH [A] 33.44 70.55 48.02 10.03 16.72 35.27Temperature [B] 33.44 167.64 48.02 56.66 16.72 83.82Residence time [C] 7.02 116.65 2.12 27.43 3.51 58.32pH X Temperature 4.54 -26.54 0.89 1.42 2.27 -13.27pH X Residence time 4.54 20.26 0.89 0.83 2.27 10.13Temperature X Residence time 1.24 12.57 0.07 0.32 0.62 6.29pH X Temp. X Residence time 0.41 -40.51 0.01 3.31 0.21 -20.26
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Table 13 and 14 show the results of statistical analysis of factor and factor-interaction effects
and their contributions to thiosalts generation. From this, it is evident that only the main
effects are significant and not even a single interaction effect exists in both cases. In the case
of the pyritic ore, changes in residence time did not significantly affect the thiosalts
generation. All the significant effects have positive signs implying that, within the studied
factor space, all three factors contribute to thiosalts generation. The extent to which each
factor contributes to the total amount of thiosalts is sufficiently independent of the levels of
the remaining two factors. In other words, whether it is in the winter (where in-mill water
temperature is around 10°C) or in the summer, the effect of change in pH or change in
residence time will remain about the same all other conditions being similar. For mill
temperatures below 10°C and above 25°C there may be some differences. Tables 13 and 14
show statistical details of variance analysis for the factors of significant influence. From
Table 13, it is evident that the generation of thiosalts can be adequately expressed in terms of
only pH and temperature variations. Temperature and pH variations contributed 96% of the
total thiosalts generated, each have equal contribution in the case of the pyritic ore. The
effects are linear in nature (note that curvature with a probability of greater than 0.7 is not
significant) implying that increasing pH beyond 9.5 and temperature beyond 25°C would
increase the thiosalts generation at a similar rate. This linearity of the effects of all the three
factors investigated is also confirmed in Table 13.
Thiosalts generation by the pyrrhotitic Cu-Ni ore is significantly affected by all three factors,
temperature being the largest contributor (56.7%) followed by residence time (27.4%) and
pH (10%). The effects of these factors on thiosalts generation are linear as in the previous
case.
The pyrrhotitic ore appears to be more sensitive to pulp temperature than the pyritic ore while
the pyritic ore is more sensitive to pH than the pyrrhotitic ore (Figures 14, 15 16 and 17).
Unlike its effect in the tailings pond, elevated temperatures may not contribute to thiosalts
degeneration during the relatively short residence time in the processing plant. Pulp
residence time, which has a negligible effect on thiosalts generation in the case of pyritic Cu
ore, has however a significant contribution in the case of pyrrhotitic Cu-Ni ore.
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Table 13. ANOVA for Selected Factorial Model (Pyritic Cu ore) Source Sum of
Squares DF Mean Square F Value Prob > F
Model 4473.79 2 2236.89 14.78 0.0031
Curvature 17.37 1 17.37 0.11 0.7447
Residual 1059.07 7 151.30
Lack of Fit 184.45 5 36.89 0.084 0.9873
Pure Error 874.62 2 437.31
Cor Total 5550.22 10
Root MSE 12.30 R-Squared 0.8086 Dep Mean 80.77 Adj R-Squared 0.7539 C.V. 15.23 Pred R-Squared 0.5604 PRESS 2440.08 Adeq Precision 9.018 Desire > 4
Table 14. ANOVA for Selected Factorial Model (Cu-Ni pyrrhotitic ore) Source Sum of
Squares DF Mean Square F Value Prob > F
Model 93370.68 3 31123.56 14.69 0.0036
Curvature 96.07 1 96.07 0.045 0.8384
Residual 12713.21 6 2118.87
Lack of Fit 5828.23 4 1457.06 0.42 0.7898
Pure Error 6884.98 2 3442.49
Cor Total 1.062E+05 10
Root MSE 46.03 R-Squared 0.8802 Dep Mean 238.25 Adj R-Squared 0.8202 C.V. 19.32 Pred R-Squared 0.6345
PRESS 38804.11 Adeq Precision 11.434 Desire > 4
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The total thiosalts generated may be expressed with the following equations: Pyritic ore:
C = 16.72 * pH + 2.23 * T - 99.61 Equation 16
Pyrrhotitic ore:
C = 35.27 * pH + 11.18 * T + 4.17 * t - 375.6 Equation 17
where C is the total thiosalts (TTS) concentration in ppm, T is temperature in oC and t is
residence time in minutes.
Figures 14 and 15 show the adequacy of these models to estimate the amount of TTS
generated under various conditions. Within the factor-space studied, the average TTS
generated by the pyritic ore is 81.5 g/t (Figure 20). On average, the pyrrhotitic ore generates
236.4 g/t TTS (Figure 21). Raising the pH from 8.5 to 9.5 would result in an increase of
these values by 16 g/t and 35 g/t respectively assuming that the temperature and residence
time remains constant.
All other conditions remaining constant, a change in pulp temperature by 1°C would result in
an increase by 2.2 g/t and 11.2 g/t in TTS for the pyritic and pyrrhotitic ores respectively. An
increase in residence time by 1 minute has the effect of increasing total thiosalts generation
by about 4 g/t for the pyrrhotitic ore while there is no significant change occurring in the case
of the pyritic ore.
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INFLUENCE OF GRINDING MEDIA ON THIOSALTS GENERATION
Test Methodology
Samples weighing 1.65 kg were ground at 66% solids to a targeted grind size by using 100%
stainless steel, 100% mild steel and a 50%:50% mixture of stainless steel and mild steel rods
(equal in number of rods and similar in weights and diameters). No reagents were used
during grinding. The mill discharge was allowed to settle and the clear solution was analyzed
for total thiosalts.
Results and Discussion
The physical parameters of testing and the results are presented in Table 15 and Figures 22,
23 and 24. From Figure 24 it is evident that the pyritic ore produces more thiosalts than the
pyrrhotitic ore regardless of the grinding media composition. It is however necessary to
determine if this is the case for all pH values within the range of interest. Lime is the major
reagent used to control pH in most sulphide ore processing plants. The change in pH of mill
discharge, as a function of lime addition rate, is shown in Figure 25. The resulting pulp
conditions are shown in Table 16. Stainless steel media was used in this series of tests. The
pyrrhotitic ore consumes at least three-times more lime than the pyritic ore to obtain similar
pH.
Table 15. Experimental conditions and results of grinding media effect study
Pyritic ore (Louvicourt) Pyrrhotitic ore (Strathcona) Grinding media
100% MS SS/MS mix 100% SS 100% MS SS/MS MIX 100% SS
Temperature (0C) 19.1 19.00 22.0 20.3 22.00 22.1
Dissolved oxygen conc. (mg/L) 1.38 4.24 1.09 2.42 0.42 4.23
pH 6.6 7.05 6.31 6.03 6.88 5.31
Conductivity (µs) 36.9 20.3 2.4 56.3 3.2 4.6
Thiosalts concentration. (ppm) 22 40 104 16 11 66
Thiosalts generated (g/t of ore) 11 21 53 8 6 34
Note: MS: Mild steel, SS: Stainless steel
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Table 16. Effects of pulp pH (lime addition) on thiosalts generation during grinding with stainless steel
Pyritic ore (Louvicourt) Pyrrhotitic ore (Strathcona)
Lime (g/t) 152 455 909 152 455 909 1818 2424 3212
pH 0.81 6.64 4.64 0.56 1.5 5.3 1.5 2.0 4.5
Conductivity (µs) 1262 1590 1497 3350 2280 3360 1852 2760 4480
Temperature (0C) 7.04 7.96 9.44 6.67 6.83 7.4 7.14 8.03 9.14
Dissolved oxygen conc. (mg/L) 24.8 24.6 26.4 28.6 25.2 23.9 26.5 22.5 24.5
Thiosalts concentration (ppm) 146 228 366 13 18 134 55 107 256
Thiosalts generated (g/t of ore) 72 114 183 7 9 67 28 55 130
The effects of pulp pH (as controlled by lime addition) on thiosalts generation is shown in
Figure 26 for both ore types. Unlike the flotation stage (see Figures 16, 17 and 19), the
pyritic ore produces more thiosalts than the pyrrhotitic ore within the range of grinding pH
investigated. The linearity of the relationship and the similarity of the slopes for the two
curves representing the two ores may provide a simple predictive tool.
Although both grinding and flotation result in increases of thiosalts for both ore types, the
extent to which milling and flotation affect each ore type appears to be different. Since pyrite
produced more thiosalts than pyrrhotite during grinding while it produced less during
aeration flotation (see Figure 17), an explanation is ought to be found. It could be that the
mechanism of oxidation during grinding where there is a galvanic influence of a grinding
media is more intensive for the pyritic ore. It could also be that, due to the surface coating by
oxidation products formed during grinding, the rate of oxidation is slower in the case of the
pyritic ore than it is for the pyrrhotitic ore during aeration (flotation). Due to grinding in a
closed mill, the oxygen demand may not have been met for the pyrrhotitic ore compared to
the pyritic ore. It requires characterization of surface oxidation products to validate the
above mentioned hypothesis.
The following preliminary conclusions were drawn from the test results:
• The amount of thiosalts generated during grinding strongly depends on the type of
grinding media.
• As anticipated, the stainless steel produced more thiosalts than mild steel grinding media
did. Switching from 100% mild steel to 100% stainless steel media increased the amount
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of total thiosalts generated during grinding by 5-fold for the pyritic ore and 4-fold for the
pyrrhotitic ore.
• Grinding the pyrrhotitic ore with a 50:50 mix of stainless steel and mild steel media
generated slightly less thiosalts than the 100% mild steel media. Grinding the pyritic ore
under similar conditions doubled the amount of thiosalts generated during grinding.
• The change in trend of dissolved oxygen consumption during grinding, in response to
changes in grinding media composition, is unique for both ore types. The highest
consumption of oxygen for the pyritic ore occurred during grinding with 100% stainless
steel and the lowest consumption occurred during grinding with the 50:50 mix. The
opposite is true for the pyrrhotitic ore. In general, where 100% stainless steel or mild
steel grinding media is used, oxygen is stripped from the solution faster by the pyritic ore
than the pyrrhotitic ore.
• Conductivity of grinding mill discharge solution is higher for the mild steel media than
the stainless steel media.
• The pyritic ore is oxidized faster than the pyrrhotitic ore during grinding regardless of the
grinding media type. During flotation, the opposite appears to be true. Less thiosalts are
generated by the pyritic ore than by the pyrrhotitic ore at pH values normally used for
flotation.
• The solution becomes more acidic with increase in proportion of stainless steel in the
media.
Being influenced by both ore mineralogy and grinding media composition, oxidation of
sulphide ore during grinding, and the resulting thiosalts generation, is a complex process.
The environment in an autogenous (or semi-autogenous) mill can be expected to be more
oxidizing (or non-reducing) than in conventional mill in which active media is used and this
results in the formation of higher concentration of S2O3- (Forrssberg et al., 1993).
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STUDY OF THIOSALTS FORMATION UNDER SIMULATED SULPHIDE ORE PROCESSING PLANT CONDITIONS
Continuous and semi-batch-type flotation tests were conducted in the laboratory to
investigate thiosalts generation by simulating operations of the Louvicourt and Strathcona
mills. Prior to these tests, the processing plants were sampled to determine the levels of
thiosalts concentrations in major streams. Based on a preliminary investigation, it was
decided to use batch-type laboratory flotation tests to study the nature of thiosalts generation
in the processing plants. Data obtained from laboratory simulations correspond to the
measurements made on the samples obtained from the plants. The amount and rate of
thiosalts generation in the process streams are influenced mainly by sulphide mineral
quantities and types of reagents used, pH, temperature and residence time.
Neither Strathcona mill nor Louvicourt mill was able to provide the proposed amount of ore,
dried and crushed to minus 10 mesh size required to process 180 kg of ore per hour. In view
of this, a small-flow continuous grinding, classification and flotation circuit capable of
processing 200 g/min was proposed as an alternate approach. SAG mill feed from the
Louvicourt mill and rod mill feed from the Strathcona mill were sampled dried and crushed
at CANMET. The Louvicourt ore was tested by both continuous and semi-batch modes
whereas the Strathcona ore was tested on semi-batch mode only.
Continuous Testing of Thiosalts Generation for the Louvicourt Ore
Figure 27 shows the configuration of the small-flow continuous grinding, classification and
flotation experimental set-up capable of processing 200 g/min of ore. The grinding circuit
consists of a rod mill in closed circuit with a 160 µm sieve. The flotation circuit was
configured to allow pre-aeration, collector conditioning, and Cu rougher-scavenger and
3-stage closed circuit cleaning of Cu concentrate. The Zn circuit is comprised of activation
stage, collector conditioning, pH adjustment, Zn roughing, scavenging and 3-stage cleaning
of Zn concentrate. Main flotation conditions are summarized in Table 17.
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Table 17. Flotation conditions for the Louvicourt ore
Unit operation/conditions Conditions Remarks
Grinding size 100% passing 160 micron
Grinding pH 8 to 8.5
Aeration time 10 min 2 L/min airflow
Cu Collector type Combination of KAX 20 g/t, 3 min conditioning
pH of Cu flotation 8.5 to 9
Rougher and scavenger residence time 30 min
Zn activation pH > 8.5
CuSO4.5H2O 280 g/t of feed
SIPX 30 g/t of feed
SIPX conditioning pH 10-11
Zn Flotation pH 10-11
Zn rougher and scavenger residence time 30 minutes
Table 18. Thiosalts generation in the experimental grinding and flotation circuit Water flow (mL/min) Total thiosalts
(mg/L) g/min g/min/t of feed
ST1 Mill Feed 0.0059 29.5 ST2 Mill discharge 200 52 0.0104 ST2-ST1 Grinding 0.0045 22.5 ST3 Post aeration 300 39 0.0117 ST3-ST2 Aeration 0.0013 6.5 ST4 Cu concentrate stream 60 70 0.0042 ST5 Cu tailings stream 290 71 0.0206 ST4+ST5 Cu circuit 0.0131 65.5 ST7 Zn concentrate stream 20 77 0.0015 ST8 Zn tailings stream 300 68 0.0204 6.8 ST7+ ST8 Zn circuit 0.0014 Total 0.0261 The distribution of thiosalts generation in the circuit is shown in Table 18 and Figure 28. The
amount of total thiosalts generated in the mill discharge includes the thiosalts originally
contained in the feed sample. An estimated 23% of the thiosalts measured in the mill
discharge originated from the feed.
With 50% of the total thiosalts generated, Cu circuit is the biggest contributor followed by
grinding (17%). Owing to the addition of CuSO4, which reduces the amount of total thiosalts
concentration in the solution, the amount of thiosalts generated within the Zn circuit is only
5% despite the alkalinity of the circuit which was maintained at pH of about 11. Aeration
contributed only 5%.
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Semi-batch Testing of Thiosalts Generation for Louvicourt Ore
Stabilization and control of the small flow continuous testing system described in the
preceding section was fast and easy. However, changing the flow conditions to less than
200 g/min solids was ineffective and higher than 200 g/min of solids flow resulted in coarse
grinding. Changing the residence time in the flotation and conditioning circuits was also
difficult. In view of this, a semi-batch flotation setup was assembled for more accurate
measurements of flow and other physical and chemical conditions.
Test Methodology
This setup consists of an automated and instrumented flotation cell based on
Denver laboratory flotation machine (Figure 29). The equipment allows automated
measurement and/or control and recording of various parameters such as airflow rate, pH,
oxidation reduction potential (ORP), dissolved oxygen concentration, temperature, froth
depth and pulp level. Froth is picked up automatically and pumped to a filtration funnel.
Both solids and froth water weight are monitored and recorded during flotation. Two modes
of flotation are available: one with addition of pH-adjusted water for pulp level control and
the other is without water addition. In the latter case, there is no need to maintain constant
pulp level with water. The froth pick-up mechanism is designed to automatically track the
pulp/froth interface at a predetermined distance (froth depth). This eliminates the undue
dilution of flotation pulp and reagent concentrations. The whole setup minimizes
intervention by the operator and ensures consistently reproducible results, which are critical
when using statistical design and analysis of results.
The rougher and scavenger flotation stages were conducted under controlled temperature, pH
and airflow rate. Cleaning of concentrates was done in a similar but smaller flotation setup
but without control on temperature. The complete flowsheets indicating sampling points are
shown in Figure 30. Selective Cu and Zn flotation procedure was used, although there was
very little Zn in the ore, to better simulate plant procedure.
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Grinding
• grinding was carried out in a rod mill with 46 lbs. mild steel rods at 66% solids.
• no excess water was used to wash down the pulp from the mill. Volume of the pulp,
when transferred to the flotation cell, was less than that of the cell. No water was
removed from the pulp to preserve the composition of the pulp solution.
• the pulp was diluted in the flotation cell to 40% solids.
Aeration
• pH was adjusted with lime addition to 8.5
• pulp was aerated to ORP of = -100 mV (SCE vs Au electrode)
• collector conditioning for Cu Rougher flotation
• PAX was added at pH 8 - 8.5
• duration of conditioning was 3 minutes
Cu Rougher Flotation
• Cu was floated at 2.5 L/min. airflow, 1600 RPM, and at a pH of 8.5.
• frother amount was just about sufficient and was added gradually in a diluted form.
• froth removal was gentle and uniform. The targeted concentrate weight was
recovered over a period of 10 minutes.
Cu Scavenger Flotation
• airflow was temporarily stopped and the required amount of collector was injected
deep into the pulp for a thorough mixing before turning on the air.
• froth removal was gentle. The targeted concentrate weight was recovered over a
period of 10 minutes.
Zn Flotation
• Zn activation with CuSO4 was for about 1 minute and was carried out before pH
adjustment for Zn flotation.
• pH was adjusted to 11 before collector (sodium isopropyl xanthate) addition
• collector conditioning was for 3 minutes.
Zn Rougher Flotation
• pH of 11 was maintained
• airflow rate was 2.5 L/min.
• froth removal was gentle. The targeted concentrate weight was recovered over a
period of 10 minutes.
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Zn Scavenger Flotation
• airflow was temporarily stopped and the required amount of reagent(s) was injected
deep into the pulp for a thorough mixing before turning on the air. A pH of 11 was
maintained.
• froth removal was gentle. The targeted concentrate weight was recovered over a
period of 10 minutes.
Concentrate Cleaning
• both Cu and Zn concentrates cleaning were carried out in a small cell with a gentle
airflow.
• Cu cleaning was at pH 6 to 6.5. Zn cleaning was at pH 10.5 to 11
• froth removal was gentle and slow.
• the targeted concentrate weight was recovered over a period of 3 minutes.
Results and Discussions (Louvicourt)
The bulk chemistry and mineralogical composition of the flotation products are summarized
in Table 19. In Table 20, metal recovery, in separate mill products, is shown. Table 21
shows the overall grade and recovery of Zn if the separate products were combined. Ignoring
the amount of Zn in the products allows considering the two separate concentrates as
belonging to only Cu. In this case, the recovery of Cu is 91.9% at 23.7% Cu grade or 93.5%
at 19.1% Cu grade. These values are comparable to that of the plant grade and recovery.
Figure 31 shows the amount of total thiosalts generated in major process circuits by each ton
of feed ore. Evidently, 14% of the total thiosalts comes with the feed ore. Approximately
one-third of the total thiosalts was generated during grinding. Cu conditioning contributed
only 5%. Cu rougher/scavenger/cleaner circuit produced 23%. Zn conditioning stage,
particularly the addition of CuSO4, results in minor reduction of thiosalts concentration. Zn
rougher/flotation/cleaner produced 26% of the total thiosalts. Cu cleaning stage alone
contributed half of the total amount generated by Cu rougher/scavenger/cleaner circuits. The
same applies to Zn circuit. This can be explained by the similar quantities of sulphide
minerals present in both circuits. Due to the insignificance of Zn content in the ore, both
circuits can be technically considered as Cu circuits. In this test, Zn flotation was carried out
not to recover Zn but to monitor the effects of Zn processing factors on thiosalts generation.
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Table 19. Bulk chemistry and mineralogical quantification of the flotation products (Louvicourt) Assays % Mineral distribution
Stream Weight(g)Cu Fe Zn S CuFeS2 ZnS FeS2 Others
Cu concentrate 95.7 30.6 30.1 0.51 34.68 88.29 0.76 6.87 4.08Cu cleaner tailings 7.1 11.3 22.5 0.50 25.98 32.60 0.75 26.96 39.69Cu circuit tailings 22.9 0.9 18.2 0.13 20.88 2.51 0.19 37.40 59.90Zn cleaner concentrate 72.0 23.1 29.7 1.90 34.91 66.65 2.84 20.15 10.36Zn cleaner tailings 52.0 1.7 18.3 0.16 21.01 4.76 0.24 36.14 58.86Zn scavenger tailings 1377.9 0.2 17.9 0.06 20.51 0.69 0.09 37.94 61.28Head Sample (assayed) 1650.0 3.5 19.2 0.19 22.06 10.21 0.28 34.51 54.99
Table 20. Flotation test results (separate Cu and Zn concentrates)
Weight Cu Fe Zn (g) % Assay Cumulative
dist'n Assay Cumulative dist'n Assay Cumulative
dist'n Cu concentrate 95.7 5.88 30.60 57.33 30.10 9.23 0.51 17.24Cu cleaner tailings 102.8 6.32 29.27 58.90 29.58 9.74 0.51 18.49Cu circuit tailings 125.7 7.72 24.09 59.29 27.50 11.08 0.44 19.54Zn cleaner concentrate 72.0 4.42 23.10 32.56 29.70 6.85 1.90 48.32Zn cleaner tailings 124.0 8.85 14.10 34.24 24.92 9.90 1.17 51.26Final tailings 1377.9 84.66 0.240 6.5 17.90 79.0 0.060 29.2Head Sample (assayed) 1627.6 100 3.14 100 19.18 100 0.17 100Head Sample (calculated) 26.8 3.54 19.20 0.19
Table 21. Flotation Test Results (Combined Cu and Zn concentrates)
Weight Cu Fe Zn (g) % Assay Cumulative
dist'n Assay Cumulative dist'n Assay Cumulative
dist'n Cu concentrate 95.7 5.88 30.60 57.33 30.10 9.23 0.51 17.24Cu cleaner tailings 102.8 6.32 29.27 58.90 29.58 9.74 0.51 18.49Cu circuit tailings 125.7 7.72 24.09 59.29 27.50 11.08 0.44 19.54Zn cleaner concentrate 197.7 12.15 23.73 91.85 28.30 17.93 0.97 67.86Zn cleaner tailings 249.7 15.34 19.13 93.53 26.22 20.98 0.80 70.80Final tailings 1377.9 84.66 0.240 6.5 17.90 79.0 0.060 29.2Head Sample (assayed) 1627.6 100 3.14 100 19.18 100 0.17 100Head Sample (calculated) 26.8 3.54 19.20 0.19
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Semi-batch Testing of Thiosalts Generation for Strathcona Cu-Ni ore
The same equipment and procedures used in the investigation of Louvicourt ore were used in
testing the Strathcona ore with a slight difference in the flowsheet. In the case of Strathcona,
in which the plant flowsheet was simulated, no attempt was made to separate Cu from Ni.
The flowsheet, which is similar to the Strathcona Mill flowsheet, is shown in Figure 32.
Results and Discussions (Strathcona) The bulk chemistry and mineralogical quantities of the flotation products are given in
Table 22. The ore contains about 12.6% chalcopyrite, 3.7% pentlandite and 35.9%
pyrrhotite. Pyrrhotite is the predominant sulphide mineral in all streams except in Cu circuit
streams and in the non-magnetic stream where chalcopyrite dominates. Metal distribution in
the flotation products is shown in Table 23. The flotation process employed was adequate
and resulted in 97% overall recovery of Cu at a grade of 9.7% Cu, and 87.9% recovery of Ni
at a grade of 4.9% Ni.
The operation of the simulated circuit resulted in the production of 579 g thiosalts per ton of
feed. The amount of thiosalts generated by each ton of feed ore in various circuits is shown
in Figure 33. The 3-minute conditioning with potassium amyl xanthate contributed the
highest amount of thiosalts (i.e. 29.3%). The primary conditioning circuits contributed most
of the remaining thiosalts. It is evident that collector conditioning has a major effect on
thiosalts generation followed by the regrinding of flotation products in the pyrrhotite
rejection circuit. These two areas appear to be paramount from the point of view of
controlling the production of thiosalts.
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Table 22. Bulk chemistry and mineralogical composition of the flotation products
(Strathcona) Sulphide mineral distribution (wt%)
Weight (g) Chalcopyrite Pentlandite Pyrrhotite Total
Head 1626 12.6 3.7 35.9 52.2Cu-Ni con 65.1 90.9 4.3 17.5 112.7Cu-Ni cleaner tailings 26.6 41.0 11.2 35.2 87.4Cu cleaner feed 91.7 76.5 6.5 14.3 97.2Pyrrhotite rejection cleaner concentrate 151.7 13.6 7.2 83.7 104.5
Pyrrhotite rejection cleaner concentrate tailings 2
142.7 14.7 5.9 92.4 113.1
Pyrrhotite rejection cleaner concentrate tailings 1
139.9 12.1 6.3 97.5 115.9
Non-magnetics 71.7 66.6 2.9 34.2 103.8Final tailings 1029 0.5 0.6 11.9 12.9Note: The total sulphide mineral abundance adds to more than 100% in most cases due to the assumption that the Ni, Cu, Fe and S analyzed in the products are contained by only these three minerals.
Table 23. Flotation Test Results (Strathcona ore) Weight
Cumulative distribution
Assay (%)
Cumulative distribution (%) Each
product (g) (g) % Cu Ni Cu Ni
Cu-Ni concentrate 65.1 65.1 4.00 31.50 2.80 34.19 5.50Cu-Ni tailings 26.6 91.7 5.63 26.48 4.10 40.48 11.33Pyrrhotite rejection cleaner concentrate 151.7 243.4 14.95 12.92 4.44 52.44 32.60
Pyrrhotite rejection cleaner concentrate tailings 2
142.7 386.1 23.72 10.04 4.22 64.60 49.13
Pyrrhotite rejection cleaner concentrate tailings 2
139.9 526.0 32.32 8.48 4.18 74.37 66.26
non-magnetic fraction 71.7 597.7 36.72 9.74 4.88 97.08 87.89
Rougher/scavenger tailings 1029 1029.9 63.28 0.170 0.39 2.9 12.1
HEAD (calculated) 1627.6 100 3.69 2.04 197 100HEAD (assayed) 3.54 2.34
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EFFECTS OF MINERALOGY ON THIOSALTS GENERATION DURING MILLING AND FLOTATION
Mineralogical composition of sulphide ores influences the amount and rate of thiosalts
formation in mill feed, during grinding and flotation. An examination of ore samples with
variable quantities of sulphide minerals and corresponding amounts of thiosalts generated
under similar conditions allows estimation of the contributions of grinding and sub-processes
in flotation to the formation of thiosalts. The Strathcona and Louvicourt ores were subjected
to batch-type grinding and flotation simulation experiments as shown in Figures 34 and 35.
Each ore sample was processed to prepare variable head grade samples to simulate possible
variation in mineralogical composition. Magnetic separation was used to prepare the
pyrrhotitic Cu-Ni ore samples whereas gravity separation was used to prepare the pyritic Cu-
Zn ore samples. The samples were mineralogically characterized to investigate relationships
between the level of total thiosalts generation and the changes in mineralogical composition.
Louvicourt Ore
Sample Preparation and Testing Methodology
The pyritic ore sample was crushed to 100% passing 1650 µm and scrubbed under nitrogen
atmosphere with deoxygenated water to remove any residual thiosalts in the sample. The
sample was then ground at 66% solids with a stainless steel media in deoxygenated water to
reduce oxidation. The mill discharge was further diluted with deoxygenated water and
subjected to gravity separation on a shaking table. The middling and the concentrate,
containing mostly sulphide and other metallic minerals, separated in this manner, were
pressure filtered under nitrogen and preserved in the freezer. Equal amounts of sample were
taken from the concentrate and the middling to mix with a 1.65 kg of freshly ground sample.
Each of the four tests conducted contained the same amount of original ore but variable
amounts of gravity concentrate and middling. The mixing proportion of solids for each test is
given in Table 24.
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Table 24. Louvicourt experimental samples
Test ID Original sample
(%)
Table concentrate and middling
(%)
Total sample weight
(g) LVT 1 96 4 1710 LVT 2 93 7 1770 LVT 3 90 10 1830 LVT 4 87 13 1890
Bulk chemical compositions of the samples are given in Table 25. The head sample (LVT1)
has 19.5% Fe, 18.4% S (sulphide), 3.3% Cu and 0.14% Zn. LVT2 and LVT3 do not display
significant variations from the head sample. LVT4 has higher sulphide S and Fe
concentrations.
Table 25. Bulk chemical analysis of the samples
prepared by gravity separation LVT1 LVT2 LVT3 LVT4
SiO2 35.94 34.87 34.66 33.80 Al2O3 8.88 8.69 8.88 8.69 MnO 0.12 0.11 0.11 0.12 MgO 4.48 4.31 4.48 4.48 CaO 1.54 1.54 1.54 1.82 Na2O 0.31 0.32 0.30 0.32 K2O 0.63 0.61 0.66 0.58 CO2 3.60 3.54 3.51 3.75 SO4 0.34 0.33 0.33 0.34 Ssul 18.41 18.41 19.40 20.62 Fe 19.50 19.90 19.60 20.10 Cu 3.29 3.54 3.86 3.69 Pb na na na na Zn 0.14 0.15 0.15 0.14 Total 97.17 96.33 97.47 98.44 na: not analysed
Mineralogy
Mineralogy of the three process samples and grain sizes are summarized in Table 26.
Variations in mineralogy and textural relationships among the three samples are not
significant. Representative photomicrographs illustrating the salient textures and mineral
associations are presented in Figures 6, 7, 8, 9, 11, 12, 13, 36 and 37.
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Table 26. Minerals identified, relative abundances and particle sizes in the Louvicourt experimental samples
Abundance particle size (µm) Mineral LVT2-H LVT3-H LVT4-H LVT2-H LVT3-H LVT4-H
Pyrite +++ +++ +++ <125 (25-75) <125 (25-75) <125 (25-75) Chalcopyrite ++ ++ ++ <125 (25-60) <125 (25-60) <125 (25-60) Magnetite/Ilmenite + + + 25-100 25-100 25-100 Pyrrhotite + + + <75 (10-60) <75 (10-60) <75 (10-60) Sphalerite + + + <25 (5-10) <25 (5-10) <25 (5-10) Galena + + - <10 <10 <10 Arsenopyrite + - + <10 <10 <10 Quartz +++ +++ +++ 1-150 (25-100) 1-150 (25-100) 1-150 (25-100) Mg-siderite ++ ++ ++ 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) Ankerite ++ ++ ++ 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) Calcite + + + 25-75 25-75 25-75 Dolomite + + + 25-75 25-75 25-75 Muscovite ++ ++ ++ 10-75 10-75 10-75 Chlorite +++ +++ +++ 10-75 10-75 10-75 Amphibole + + + 10-60 10-60 10-60 Potassium feldspar + + + 1-150 (25-100) 1-150 (25-100) 1-150 (25-100) Plagioclase feldspar + + + 1-150 (25-100) 1-150 (25-100) 1-150 (25-100) Rutile + + + - - 5-20 Apatite - - + +++ :major; ++: minor; +: trace; -: not present
Sulphide and Oxide Minerals
Pyrite and chalcopyrite account for over 90% of sulphide and oxide minerals observed in
these samples. The remainder consists of magnetite, pyrrhotite, sphalerite, galena and
arsenopyrite in order of decreasing abundance. Pyrite and chalcopyrite occur primarily as
liberated inclusion-free grains; however, very fine-grained pyrite and chalcopyrite was
observed attached to various gangue minerals. More rarely fine-grained chalcopyrite was
observed as attached to relatively coarse pyrite. All the sulphide mineral particles display
sharp edges and show no evidence of dissolution or reaction.
Gangue Minerals
Quartz, chlorite, ankerite and magnesian siderites are the dominant gangue minerals in order
of decreasing abundance in each of the three samples studied. Quartz is by far the most
abundant gangue mineral. Quartz, along with chlorite and carbonates represents
approximately 80% of all the gangue minerals. Some of the carbonate mineral grains show
corroded-looking grain edges; however, this texture shows no preference for a particular
mineral or sample. As a result, a sample may contain particles with sharp outlines and
particles with rugged edges. This suggests that dissolution is more a function of degree of
exposure than mineralogy. In addition to carbonates, some feldspar grains exhibit features
which may have resulted from dissolution. Similar to the carbonates, feldspar dissolution
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features were observed on a grain to grain basis, not a sample to sample basis. None of the
other silicate or oxide minerals display any definitive evidence of dissolution.
Polymineralic agglomerations were observed in all the samples. Gangue minerals dominate
the mineralogy of agglomerates but small quantities of pyrite and chalcopyrite are almost
always present. Agglomerations can range in size from 100 to 1000 µm.
Mineral Quantities
Mineral quantities as determined by MODAN are listed in Table 27.
Table 27. Mineral quantities (wt %) of the Louvicourt
experimental samples LVT1 LVT2 LVT3 LVT4
quartz 27.3 26.6 26.3 25.5 muscovite 13.4 13.5 14.6 14.6 plagioclase 5.1 5.3 5.3 6.0 chlorite 18.7 18.2 17.5 16.0 Mg-siderite 2.7 2.6 1.9 0.9 ankerite 6.2 6.3 6.9 8.5 magnetite 0.2 1.0 0.0 0.0 pyrite 19.4 19.1 19.6 21.1 chalcopyrite 6.7 7.1 7.7 7.2 sphalerite 0.2 0.2 0.2 0.2 Total 100 100 100 100
Test Results and Discussion Scrubbing of the feed sample prior to grinding under non oxidizing nitrogen atmosphere
removed all the thiosalts originally present in the ore which was estimated to be 42 g/t.
Grinding of the ore in enclosed laboratory mild steel rod mill produced 31 g/t of total
thiosalts. It appears that a good portion of the total thiosalts in mill effluents originates from
the mine and not all is produced in the processing plant. Thiosalts are known to be formed
especially in stockpiles. Table 28 shows a comparison of particle size distribution of the
samples tested. The d80 grind size for the original ore is 52 µm. With the addition of gravity
concentrate and middling, the d80 shifts to a lower value indicating that the combination of
gravity concentrate and middling has a lower d80 value than the original ore grind size.
Generally, the higher the proportion of the gravity concentrates in the mixture the lower the
d80 size is. The concentration of total thiosalts in successive water samples, taken at
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predetermined time intervals, is reported in Table 29. To determine the dynamics of thiosalts
formation rate, the results were analyzed by time intervals and are shown in Figure 38.
Table 28. Louvicourt experimental sample size distributions
original ore LVT1 LVT2 LVT3 LVT4
d80 grinding size (µm) 52 44 47 43 40
Table 29. Test results
Total thiosalts generated (g/t) Process step
Cumulative residence time (min) LVT1 LVT2 LVT3 LVT4
5' pulp conditioning without air 5 33 39 46 20 15' aeration 15 41 48 50 33 35' aeration 35 52 69 65 59 55' aeration 55 73 97 92 94 75' aeration 75 96 127 121 124 10' min conditioning with KAX 85 116 142 138 130
The rate of thiosalts generation appears to be higher during grinding and the first few minutes
of conditioning than the first 5 to 20 minutes of flotation. The rate of thiosalts production
gradually increases for the first hour for all four samples. There is at least one-fold increase
in thiosalts production rate during this period. After that, the rate appears to be levelling off.
The increase in rate with time can be due to dissolution of oxide coatings on sulphide
particles, which may have developed during initial conditioning. This exposes more sulphide
surfaces for further oxidation to form thiosalts.
The instant reduction in the rate of thiosalts generation as aeration starts may be partly
explained by the oxidation of thiosalts to sulphate due to an increase in the abundance of
dissolved oxygen concentration. Figure 39 shows that the pulp oxidation-reduction potential
(ORP) for LVT4, which is highly reducing at the beginning, quickly becomes oxidizing in
the first 5 minutes of conditioning and levels off after 30 minutes. The dissolved oxygen
concentration follows a similar pattern, but the increase is much slower because it is partially
used up during oxidation or oxygen transfer into solution is slower.
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The pulp oxidation-reduction potential change with residence time for all the samples
(Figure 40) indicates that with an increase in the proportion of the sulphide minerals in the
pulp, the oxidation potential becomes more reducing. Only LVT1 does not follow this
pattern, probably owing to its relatively low sulphide mineral content.
To establish a relationship between pH and total thiosalts generation rate, pulp pH is plotted
against cumulative residence time (Figure 41). During the first 5 minutes of conditioning, the
pH drops sharply. With aeration, the pH begins to rise again for a period of about 10
minutes. After 10 minutes of aeration, the pH begins to gradually decrease. LVT4 and
LVT3 are generally less acidic than LTV1 and LTV2.
Conductivity also increased with an increase in abundance of sulphide minerals in the pulp
(Figure 42). Only LVT2 does not appear to follow this general pattern. The conductivity of
LTV1 (sample with the lowest amount of sulphide minerals) is the weakest, and non-
proportionally low.
Strathcona Ore
Sample Preparation, Sample Mineralogy and Test Methodology
To obtain a series of variable feed compositions for grinding and simulation of flotation
processes, the Strathcona ore was first crushed to 100% passing 1650 µm. The sample was
then separated into a magnetic and a non-magnetic fraction using a low intensity drum
magnetic separator (Eriez Magnetics Model 15DIA”X” 12’) operating at a medium speed.
The split was 53% magnetic and 47% non-magnetic fractions. Obviously some amount of
magnetic and non-magnetic particles would report into the other component by entrapment.
For simplicity, we would refer to the two products as magnetic and non-magnetic fractions.
The amount of material used in each test was 1.65 kg. The proportions used to prepare the
samples are listed in Table 30.
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Table 30. Strathcona experimental samples
Sample No Magnetic fraction (wt%) Description SAMM-H na original Sample SAMM7 0 experimental sample SAMM1 10 “ SAMM 2 30 “ SAMM 5 50 “ SAMM 3 70 “ SAMM 4 90 “ SAMM 6 100 “
Table 31. Bulk chemical analysis of the samples prepared from magnetic and non-magnetic fractions
SAMM-H SAMM7 SAMM1 SAMM2 SAMM5 SAMM3 SAMM4 SAMM6 SiO2 34.87 53.91 50.27 44.28 36.37 32.09 26.10 24.39 TiO2 0.42 0.47 0.47 0.47 0.47 0.48 0.48 0.48 Al2O3 8.13 12.47 11.72 10.77 9.07 7.75 6.43 5.86 MnO 0.11 0.12 0.13 0.12 0.12 0.11 0.12 0.11 MgO 2.30 3.27 3.00 2.75 2.49 2.27 2.12 2.04 CaO 3.46 5.21 5.00 4.46 3.95 3.43 3.06 2.92 Na2O 2.51 3.90 3.55 3.15 2.66 2.22 1.87 1.73 K2O 0.89 1.37 1.19 1.06 0.93 0.78 0.69 0.63 CO2 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 SO4 0.44 0.07 0.11 0.14 0.17 0.25 0.31 0.33 Fe 24.00 8.38 11.40 16.90 22.90 28.20 33.60 35.20 Ni 1.82 0.92 1.01 1.35 1.58 1.74 2.01 2.11 Cu 3.27 1.31 1.49 1.52 1.37 1.16 1.25 1.07 Ssul 15.33 4.34 5.98 9.74 13.47 16.92 20.32 21.90 Total 92.45 93.50 92.81 93.85 92.58 94.51 95.10 95.59 Results in wt %; Ssul: sulphide sulphur
Bulk chemical compositions of the samples are given in Table 31. The head sample
(SAMM-H) has 24% Fe, 15.3% S (sulphide), 3.3% Cu and 1.8% Ni. Iron, Ni, S and SO4
concentrations display a steady increase from the non-magnetic sub-sample (SAMM7) to the
magnetic sub-sample (SAMM6). These increases are counter balanced by decreases in SiO2,
Al2O3, MgO, CaO, Na2O and K2O concentrations. Mineralogy and the grain sizes of the
minerals present are summarized in Tables 32 and 33. The samples exhibit differences in
sulphide quantities as anticipated.
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Table 32. Minerals identified in the Strathcona samples
Mineral SAMM-H SAMM1 SAMM2 SAMM3 SAMM4 SAMM5 SAMM6 SAMM7
Pyrrhotite +++ ++ +++ +++ +++ +++ +++ ++
Chalcopyrite ++ ++ ++ ++ ++ ++ ++ ++
Pentlandite ++ ++ ++ ++ ++ ++ ++ +
Magnetite/Ilmenite ++ ++ ++ ++ ++ ++ ++ ++
Pyrite + + ++ ++ + + + ++
Sphalerite + + + + + + + +
Galena + + + + + + + -
Bornite - + + + - + + -
Cubanite - - + - + + -
Millerite + - - - - - - -
Quartz +++ +++ +++ +++ +++ +++ +++ +++
Feldspar +++ +++ +++ +++ +++ +++ +++ +++
Pyroxene +++ +++ +++ +++ ++ ++ ++ ++
Muscovite + + + + + + + +
Chlorite +++ ++ +++ +++ +++ +++ +++ +++
Amphibole ++ + ++ ++ ++ ++ ++ ++
Epidote ++ ++ ++ ++ ++ ++ ++ ++
Biotite + + + + + + + +
Iron oxyhydroxide + + + + - - - -
Apatite + + - + + + + +
+++ :major; ++: minor; +: trace; -: not present
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Table 33. Grain sizes (µm) of the minerals identified in the Strathcona samples
Mineral SAMM-HEAD SAMM7-H SAMM1-H SAMM2-H SAMM5-H SAMM3-H SAMM4-H SAMM6-H
Pyrrhotite <125 (50-100) <100 (25-50) <125 (50-100) <125 (50-100) <125 (50-100) <100 (25-50) <100 (50-75) <125 (50-100)
Chalcopyrite <125 (25-75) <100 (25-50) <125 (25-75) <125 (25-75) <125 (50-75) <100 (25-50) <100 (25-75) <125 (50-75)
Magnetite/Ilmenite 50-125 10-100 (25-50) 50-125 50-125 50-75 5-100 (25-50) 5-100 (50-100) 50-75
Pentlandite <75 (10-50) <75 (10-25) <75 (10-50) <75 (10-50) <75 (25-50) <75 (10-25) <25 (5-15) <75 (25-50)
Pyrite <125 (60-100) <50 (20-40) <125 (60-100) <125 (60-100) <100 (50-75) <50 (20-40) <75 (50-50) <100 (50-75)
Sphalerite <100 (25-50) <25 (5-10) <100 (25-50) <100 (25-50) <50 (25-50) <25 (5-10) <25 (5-10) <50 (25-50)
Galena <10 <10 <10 <10 <10 <10 <10 <10
Arsenopyrite - - - - - <10 - -
Cubanite 5-25 - 5-25 5-25 5-25 - 5-25 5-25
Millerite 5-25 - 5-25 5-25 5-25 - - 5-25
Quartz 1-125 (50-100) 1-150 (25-100) 1-125 (50-100) 1-125 (50-100) 1-150 (50-100) 1-150 (25-100) 1-125 (25-75) 1-150 (50-100)
Mg-siderite 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) 1-100 (25-75) 1-125 (25-75) 1-100 (25-75) 1-100 (25-75)
Ankerite 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) 1-125 (25-75) 1-100 (25-75) 1-125 (25-75) 1-100(25-75) 1-100 (25-75)
Calcite 25-75 25-75 25-75 25-75 25-75 25-75 25-75 25-75
Dolomite 25-75 25-75 25-75 25-75 25-75 25-75 25-75 25-75
Muscovite 5-75 10-75 5-75 5-75 5-75 10-75 10-75 5-75
Chlorite 10-100 10-75 10-100 10-100 10-125 (50-100) 10-75 10-100 10-125 (50-100)
Amphibole 10-50 10-60 10-50 10-50 10-50 10-60 10-50 10-50
Potassium feldspar 1-125 (50-100) 1-150 (25-100) 1-125 (50-100) 1-125 (50-100) 1-125 (50-75) 1-150 (25-100) 1-100 (25-75) 1-125 (50-75)
Plagioclase feldspar 1-125 (50-100) 1-150 (25-100) 1-125 (50-100) 1-125 (50-100) 1-125 (50-75) 1-150 (25-100) 1-100 (25-75) 1-125 (50-75)
Apatite - 5-20 - - - 5-20 5-20 -
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Sulphide and Oxide Minerals
Pyrrhotite, chalcopyrite and pentlandite are the dominant sulphide minerals in each of the
eight samples studied. Magnetite is the most common oxide mineral in the samples. Minor
and trace sulphides and oxides include pyrite, sphalerite, cubanite, millerite, bornite, and
rutile. Their relative abundance and average grain sizes are summarized in Tables 32 and 33.
Pyrrhotite, chalcopyrite and magnetite occur primarily as liberated grains (Figures 43 and
44). Pentlandite often occurs as exsolution flames enclosed in coarse pyrrhotite grains but it
also forms liberated grains. Chalcopyrite was also observed as encapsulated grains in various
gangue minerals (Figure 45) and more rarely as attached grains to pyrrhotite. Magnetite
occurs exclusively as liberated grains with no inclusions. Galena occurs almost exclusively
as inclusions in various sulphides (e.g. chalcopyrite) and silicates (e.g. amphibole). Trace
sulphides such as cubanite, bornite and millerite were all observed as relatively small and
liberated grains.
The majority of the sulphide grains show little or no significant evidence of oxidation.
Coarse particles of pyrrhotite from each of the eight samples studied display a rim of
agglomeration of very fine-grained pyrrotite (Figure 46). This rim may contain minor
quantities of other sulphides, usually chalcopyrite or pentlandite. In some cases, this texture
appears to be gradational with grain size increasing away from the host pyrrhotite
(Figure 47). Coarse-grained pentlandite rarely displays a thin rim. Unfortunately, this rim is
too thin to be accurately resolved by the electron beam (approximate diameter 1µm). Other
sulphide grains show no evidence of oxidation.
Gangue Minerals
Quartz, chlorite, epidote, plagioclase, potassium feldspar, Ca-pyroxene and amphibole are the
major gangue minerals in the samples (Table 32). The majority of gangue minerals occur as
liberated grains (Figure 45). They may contain fine-grained inclusions of the dominant
sulphides. Polymineralic agglomerations made up of gangue minerals and various sulphides,
and ranging in size from 200 to 1000 µm occur in all the samples. None of the gangue
minerals display any apparent evidence of dissolution.
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Mineral Quantities
Mineral quantities were determined using a similar technique as the one described previously
for the Strathcona samples. Mineral quantities of the process samples are given in Table 34.
Table 34. Mineral quantities (wt%) of the samples resulting
from magnetic separation SAMM-H SAMM7 SAMM1 SAMM2 SAMM5 SAMM3 SAMM4 SAMM6 quartz 20.9 33.9 31.9 27.0 21.2 18.3 13.6 12.6muscovite 14.2 21.1 18.3 17.4 15.5 14.2 12.3 11.9Ca-pyroxene 10.1 13.1 10.6 10.1 10.6 10.9 11.3 11.3chlorite 3.4 6.5 7.8 5.8 4.1 1.9 0.7 2.9epidote 7.2 12.9 14.0 11.8 9.3 6.3 4.2 0.0ilmenite 0.8 0.9 0.9 0.9 0.9 1.0 0.9 0.9pyrrhotite 27.0 3.1 7.5 16.9 28.0 37.4 46.0 49.0pentlandite 6.0 3.6 3.7 4.8 5.5 5.9 6.6 7.2chalcopyrite 10.4 4.9 5.3 5.3 4.9 4.1 4.3 4.2Total 100 100 100 100 100 100 100 100
Grinding and flotation simulation conditions
The following grinding and simulated flotation conditions were used for each test (Table 35).
Table 35. Grinding and simulated flotation conditions
Grinding Conditions Louvicourt Strathcona Grinding media: mild steel rods stainless steel rods
Grinding time: 32 minutes variable Initial water temperature: 18°C 21.6ºC
Pulp density: 66% solids 66% solids Pulp temperature after grinding: 22ºC 24.5ºC
Conditions of flotation simulation Airflow rate: 2.5 L/min. 2.5 L/min.
Pulp equilibration: 5 minutes 5 minutes Residence time: 15, 35, 55, 75 minutes 15, 35, 55, 75 minutes
Pulp density: 32% solids 32% solids Pulp temperature 26ºC 25ºC
Test Results and Discussion
The d80 particle size for the original and composite samples is shown in Table 36. The d80
particle size decreases with an increase in the magnetic component from 10% to 90%.
Table 36. Strathcona experimental sample grain size distribution
Original sample
SAMM7 SAMM1 SAMM2 SAMM5 SAMM3 SAMM4 SAMM6
Magnetic component 0% 10% 30% 50% 70% 90% 100% d80 particle size (µm) 53 57 83 65 57 51 46 63
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Table 37. Thiosalts concentrations (g/t) generated during experiments
Total thiosalts generated (g/t) SAMM7 SAMM1 SAMM2 SAMM5 SAMM3 SAMM4 SAMM6
Unit operation Cumulative residence time (min)
Original sample 0% 10% 30% 50% 70% 90% 100%
Scrubbing N/A 30 10 30 30 36 36 49 42 Grinding N/A 7 58 45 53 60 47 48 43 5 min. pulp conditioning without air
5 20 84 60 68 66 64 80 64
15 min. aeration
15 112 104 94 144 188 218 278 238
35 min. aeration
35 216 128 132 196 264 320 420 336
55 min. aeration
55 282 152 138 218 292 380 500 438
75 min. aeration
75 350 170 174 252 358 438 570 514
10 min. condit. with KAX
85 384 164 164 252 376 452 614 524
The original sample and the samples with 10 and 30% magnetic fraction, contained equal
amounts of thiosalts in dry form. Scrubbing of these samples under nitrogen atmosphere in
deoxygenated water indicated that they all contained 30 g/t of total thiosalts. The samples
with 70 and 90% magnetic fraction contained 36 g/t and 49 g/t thiosalts respectively. The
sample with 100% magnetic minerals component, however, contained about 42 g/t total
thiosalts, 7 g/t less than the sample with 90% components. The sample without the magnetic
fraction (SAMM7) contained only 10 g/t of total thiosalts, one-fourth the amount contained
by the 100% magnetic minerals component sample (SAMM6).
Thiosalts in the feed sample appear to be associated with the magnetic fraction because the
amount of residual thiosalts removed from the test samples generally increased with an
increase in magnetic fractions as shown in Table 37.
The cumulative change in total thiosalts concentration with an increase in residence time is
shown in Figure 48. Evidently, all the experimental samples with the exception of the
original sample, produced similar amounts of total thiosalts during conditioning. The
original sample produced the least amount of total thiosalts during conditioning and the first
15 minutes of aeration. This sample ultimately produced the same amount of total thiosalts
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as the composite sample with 50:50 magnetic and non-magnetic fractions. The 50:50
composite, and the original sample, contained similar amounts of pyrrhotite and pentlandite,
but the 50:50 composite contained only one-half of the original chalcopyrite. Why the
original sample had a lower level of thiosalts at the beginning may be explained by the fact
that the composite sample was subjected to a sample preparation process. In general terms,
the higher the magnetic mineral component in the sample, the higher the amount of total
thiosalts produced during flotation. Particle size distribution appears to be affecting this
general trend. The sample with 100% magnetic fractions produced lower thiosalts compared
to the sample with 90% magnetic fractions. The 100% magnetic fraction has a finer particle
size than that of the 90% magnetic fraction (Table 36).
The average rate of thiosalts production was calculated by intervals and plotted on Figure 49
to see if such rate is consistent with sulphide mineral abundances in the experimental
samples. The rate of thiosalts generation during conditioning appears to be erratic. During
the simulated flotation stages, there is a general trend, which shows that samples with higher
amounts of sulphide mineral, release more thiosalts. The first 10 minutes of aeration marks
the highest rate of thiosalts generation which is followed by a gradual decrease with
increasing residence time. The specific rate of thiosalts generation, expressed as g/t/min., is
plotted in Figure 50 against the total quantities of pentlandite, chalcopyrite and pyrrhotite.
The rate appears to increase linearly with increases in the total amount of sulphide mineral
quantities. The rate is higher at the preliminary processing steps and decreases steadily with
increase in residence time. From Figures 51 and 52, it is evident that the coefficient of
correlation between the rate of thiosalts generation and mineral quantities does not change
significantly if the quantities of pentlandite and chalcopyrite are considered unimportant
compared to the amount of pyrrhotite. The specific thiosalts generation rate is further plotted
against the bulk sulphur assays shown in Table 31 (excluding SAMM7 and SAMM1). It
appears that there is an exponential relationship between the rate of thiosalts generation and
the sulphur content of the test samples (Figure 53). With an increase in sulphur content of
the samples, the difference in rates of thiosalts generation in successive processing stages
also increases.
The initial rapid rate of thiosalts generation coincides with the rapid increase in pulp
oxidation-reduction potential from a highly reducing to a more oxidizing condition, leveling
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
50
off within 5 minutes (Figure 54). The time interval for the rapid thiosalts production rate
coincides with a small but rapid decrease in pulp pH (Figure 55) at the early stage of
flotation.
EFFECTS OF REAGENTS ON THIOSALTS GENERATION
Effect of Xanthate on Thiosalt Generation by the Pyrrhotitic Cu-Ni ore
Xanthates are the most commonly used class of sulphide mineral collectors, the potassium
amyl form being the number one (Frank, Aplan and Chander, 1987). Laboratory flotation
test results of the Strathcona ore revealed high concentration of thiosalts in the solution
during conditioning of the pulp with potassium amyl xanthate for a relatively short period of
three minutes. An estimated 29.3% of the total amount generated during the entire test was
attributed to this conditioning stage (Figure 33). A series of tests were conducted to obtain
some understanding of the mechanisms by which xanthate influenced the increase in thiosalts
concentration in the solution. The minus 10 mesh test sample was scrubbed in deoxygenated
water of pH 2 (adjusted with HCl) at a temperature of 20°C. HCl is known to clean sulphides
resulting in S-rich mineral surface (Pratt and Nesbitt, 1997). The apparatus shown in
Figure 2 was used for the experiment. In Figure 56, the amount of thiosalts generated per
tonne of ore is plotted against the amount of potassium amyl xanthate used. This confirms
the previous observation that xanthate has a major impact on thiosalts generation (Frank
et al., 1987).
It has been suggested that collector molecules have the capacity to remove from the mineral
surfaces most oxidized products which include fine oxidized sulphide particles, colloidal
metal hydroxide particles, and oxidized sulphide layers (Smart, 1991). Thus, there are two
possible mechanisms by which the influence of xanthate on thiosalts concentration in the
pulp solution has been manifested. The first mechanism involves the transfer of thiosalts
compounds from the surface to solution as a result of the surface cleaning action of xanthate.
The second cause for increased thiosalts concentration could be the result of more surface
sulphur exposure to oxidation.
It has been shown by (Avdokhin and Abramov, 1989) that the most probable electrochemical
reactions leading to the formation of Cu-, Pb-, and Zn-xanthate by oxidation of chalcocite,
covellite, galena and sphalerite are:
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
51
Equation 18
where Kx: Potassium amyl Xanthate.
In all cases, thiosulphate ion is a major electrochemical reaction product. It is assumed that
this same mechanism is responsible for the major thiosalts generation during conditioning of
the Strathcona ore.
Effects of Sulphur Dioxide on Thiosalt Generation by the Pyritic Cu-Zn Ore
Sulphur dioxide is a reactive gas widely used as a depressant to promote selectivity between
Cu/Pb and Zn minerals. It is believed that recoveries of Au-, Ag- and Cu-minerals are
improved when sulphur dioxide is used instead of other depressants such as cyanide and
starch. The probable mechanism is assumed to be the substantial reduction of cupric ions
(activator for sphalerite) to cuprous and the complexing of the latter with sulphite ions which
lowers the activation of sphalerite.
Aqueous solution of SO2 consists of HSO3-, SO3
- and H3O (hydrated H+) ions (Chander
1987). The reaction sequence may be written as:
SO H O SO H HSO
HSO SO Hg aq2 2 2 3
3 32
( ) ( )+ ⇔ + +
⇔ +
+ −
− − + Equation 19
If elemental sulphur is present and conditions in the pulp (i.e. time alkalinity and
temperature) are favourable, the reaction between elemental sulphur and sulphite ion
proceeds to form thiosulphate (Wasserlauf and Dutrizac, 1982). Based on Equation 5, the
reaction between the two species may be written as:
Cu S H O Kx CuKx S O H e
CuS H O Kx CuKx S O H e
PbS H O Kx PbKx S O H e
ZnS H O Kx ZnKx S O H e
2 2 2 32
2 2 32
2 2 32
2 2 32
3 4 6 8
3 2 2 6 6
3 4 2 6 8
3 4 2 6 8
+ + ⇔ + + +
+ + ⇔ + + +
+ + ⇔ + + +
+ + ⇔ + + +
− − +
− − +
− − +
− − +
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
52
MS MSS SO S Oaq aq0
32
2 32+ → +− −
( ) ( ) Equation 20
If this is the case, then sulphur dioxide contributes to the total thiosalts generated in a
flotation pulp. Results presented by Noranda Mining and Exploration-Brunswick Mining
Division at the Thiosalts Workshop (Montreal, June 5, 1996) however indicated that
investigators did not find any specific unit process or reagent (including SO2) that generated
more thiosalts than others. To generate more information on the effect of SO2 on thiosalts
generation, SO2-conditioning tests were conducted for the pyritic Cu-Zn ore from Louvicourt.
Test Methodology
1.65 kg of ore was ground at 66% solids in a stainless steel mill. The sample was filtered and
rinsed with water while still on the filter paper. Subsequently it was conditioned for 5
minutes with deoxygenated water of pH 2 (adjusted using HCl). The sample was filtered and
rinsed and then split into 5 equal parts, vacuum-sealed in aluminum bag and kept frozen for
24 hours before testing. The rinse water did not contain thiosalts.
Three conditioning tests were conducted at 20°C, and at pH of 4, 5 and 6 adjusted with SO2.
Two control tests were conducted at pH 4 and 5 adjusted with buffer solutions instead of
SO2. The apparatus with automatic pH and temperature control shown in Figure 2 was used
for these tests.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
53
Test Results and Discussion
Results given in Table 38 indicate that S3O6 2- is the predominant thiosalt species in SO2
experiments. Evidently, decrease in pH (increase in SO2 in this case) increases the
concentrations of S3O6. S4O62- was detected only in the pulp conditioned with a buffer
solution. In test LVS O6, SO2 solution (without solids in it) was stirred for 5 minutes to
determine if there is a significant amount of thiosalts originating from SO2 itself. Evidently,
all three species are less than 5 ppm. Hence, it can be concluded that, there is a significant
amount of thiosalts generated as a result of mineral-SO2 interaction.
Table 38. Effects of SO2 conditioning on thiosalts generation
Test Conditions S2O3 S3O6 S4O6 Thiosalt Total
Sample Name
pH pH adjusted with: [ppm] [ppm] [ppm] [ppm] LVS 01 6 SO2 12 34 0 46 LVS 04 5 SO2 23 77 0 100 LVS 03 4 SO2 22 90 0 112 LVS 02 5 buffer 11 10 12 33 LVS 05 4 buffer 12 6 11 29 LVS 06 4 SO2 Solution, no solids. <1 <5 <5
CONCLUSIONS
Thiosalts generation in processing plants is controlled by the abundances of sulphide
minerals in the ore, pulp pH, temperature, residence time, grinding media type and reagents
such as xanthates and sulphur dioxide. The effects of pulp temperature, residence time and
pH on thiosalts generation appear to be linear. The pyrrhotitic ore appears to be more
sensitive to pulp temperature whereas the pyritic ore is more sensitive to changes in pH. Pulp
residence time has a negligible effect on thiosalts generation during processing of the pyritic
ore whereas the pyrrhotitc ore is significantly affected.
A good portion of the thiosalts in the mill circuit comes with the ore in dry form. Scrub
washing under inert atmosphere results in total removal of thiosalts contained in the feed ore.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
54
The amount of thiosalts generated during grinding strongly depends on the type of grinding
media. The stainless steel produces more thiosalts than mild steel grinding media. The
pyritic ore generated more thiosalts than the pyrrhotitic ore during grinding regardless of the
grinding media type and grinding media composition. The use of more active media or semi-
autogenous grinding would generate less thiosalts than inert media or autogenous grinding.
Thiosalts generation is influenced by sulphide mineralogy. Thiosalts generally increase with
sulphide mineral content of the ore. Thiosalts generation rate appears to be linearly
dependent on the abundance of sulphide minerals in the ore.
Flotation of the pyrrhotitic ore produced more thiosalts than the pyritic ore at pH values
typical for flotation. Continuous testing results on the pyritic ore indicated that an estimated
23% of the overall thiosalts originated from the feed while grinding, aeration, copper circuit
flotation, and Zn circuit flotation contributed 17%, 5%, 50% and 5% respectively.
Semi-batch testing results on the pyritic ore indicated that approximately one-third of the
total thiosalts was generated during grinding. Copper rougher/scavenger/cleaner circuit
produced 23% of the total thiosalts generated with Cu cleaning stage being responsible for
approximately half of this amount. Zinc rougher/flotation/cleaner produced 26% of the total
thiosalts.
Semi-batch testing results of the pyrrhotitic ore indicated that the collector (potassium amyl
xanthate) conditioning contributed the highest amount of thiosalts generated in the circuit.
This is followed by the regrinding of flotation products in the pyrrhotite rejection circuit.
The amount of thiosalts in pulp solution appears to increase with the amount of collector
used.
The rate of thiosalts generation is the highest during the first few minutes of conditioning
including aeration. Conditioning of pulp with SO2 affects thiosalts generation. The amount
of thiosalts increases with an increase in SO2.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
55
RECOMMENDATIONS
new process flowsheet development (stockpiling procedure, flotation circuit
configuration, selection of grinding mill and grinding media, selection of reagents and
reagent addition points) has to be based not only on metallurgical performance but also
based on the resulting level of thiosalts generation.
the characteristics of thiosalts on mineral surfaces before and after grinding, and in
flotation circuits (before and after reagent additions), should be examined in light of the
thiosalts species in the solutions, to allow appropriate changes to the process to inhibit
thiosalts generation.
some of the samples from the bench-scale testwork should be analysed by X-ray
photoelectron spectrometry (XPS) and synchrotron-based X-ray absorption spectrometry
(XAS) for the determination of sulphur speciation and oxidation features on the surfaces
of sulphide grains. These studies of chemistry of mineral surfaces at the mineral-solution
interface are required to develop an understanding of thiosalts formation in mill circuits.
Chemical reactions that control the production and evolution of thiosalts in process
streams will be governed by the behavior of elements at the mineral-solution interface. If
we understand the reactions at the mineral-solution interfaces, then we can look into
developing prediction and prevention techniques to passivate or demote such reactions
from occurring.
ACKNOWLEDGEMENTS
Participation and help of Dr. Peter Wells, Joseph Fyfe, Mike Wiebe and Noel Mejia of
Falconbridge Ltd., and Yves Desrosiers of the Louvicourt mill at various stages of the project
are greatly appreciated. Bob Campbell and Micheline Boisclair of CANMET are
acknowledged for sample preparation, assembling experimental setups, calibration of
instruments and conducting tests. Pierre Groulx of CANMET performed polished section
preparation work. Chemical analyses were carried out by the Analytical Services Group of
CANMET. John Graham’s timely and efficient response for thiosalts analyses and guidance
for sample preservation are greatly appreciated. The report was reviewed by Dr. Allen Pratt
Orlando Dinardo and Raymond Gaëtan.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
56
REFERENCES
1. Bocharov, V.A. et al., (1985), Characteristics of sulphide oxidation during selective
flotation of pyritic ore, Svetnye Metalu No. 10.
2. Avdokhin, V.M. and Abramov, A.A., (1989), Oxidation of sulphide minerals during
the process of enrichment, Moscow “Nedra”.
3. Kosabag, D. and Smith, M.R., (1985), The effect of grinding media and galvanic
interactions upon the flotation of sulphide minerals, In Complex Sulphides. Ed.
Zunkel, A.D., Borman, R.S., Moris, A.E., Wesley R.J. pp. 55-82. The Metallurgical
Society, Inc.
4. Natarajan, K.A., (1988), “Electrochemical aspects of bioleaching multisulfide
minerals,” Minerals and Metallurgical Processing, Vol. 5, No. 2, pp. 61-65.
5. Pozzo, R.L. and Iwasaki, I., (1987), “Effect of pyrite and pyrrhotite on corrosive wear
of grinding media,” Minerals and Metallurgical Processing, Vol. 4, No. 3, pp. 166-
171.
6. Cheng, X. and Iwasaki, I., (1992), “Effect of Chalcopyrite and pyrrhotite interaction
on flotation separation,” Minerals and Metallurgical Processing, Vol. 9, No. 2,
pp. 73-79.
7. Paktunc, A.D., (1998) MODAN: An interactive computer program for estimating
mineral quantities based on bulk composition. Computers and Geosciences, 24:425-
431.
8. Rolia, E. and Tan, K.G., (1985), The generation of thiosalts in mills processing
comlex sulphide ores; Canadian Metallurgical Quarterly 24:293-302.
9. Wasserlauf, M. and Dutrizac, J.E., (1985), The chemistry, generation and treatment
of thiosalts in milling effluents – A non-critical summary of CANMET investigations
1976-1982; CANMET Report 82-4E, 91p.
10. Frank, F., Aplan, and Chander, S., (1987), Reagents in Mineral Technology; ed.
Somasundran, P. and Moudgil Brij, M., 335-369.
11. Forrssberg, K.S.E., Subrahmsanyam, T.V., Leif, K.N., (1993), Influence of grinding
method on complex sulphide ore flotation. Int. J. Miner. Process., 38:157-175.
12. Skrinchenko, M.L. and Shelkova, C.A., (1987), Interaction of thiosulphate complexes
of Cu with sulphide minerals. Svetnye Metalu. 3:94-97.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
57
13. Pratt, A.R. and Nesbitt, H.W., (1997), Pyrrhotite leaching in acid mixtures of HCl
and H2SO4. American Journal of Earth Science, Vol. 297, October, 1997, pp. 807-
828.
14. Illyvieva, A.E., Garshteyn, G.V. and Baron, I.U., (1986), On Evaluation of
Mechanisms of chemical changes during aeration of complex sulphide pulp. Svetnye
Metalu. 2:80-82.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
APPENDIX A FIGURES
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 1. Metal sulphide oxidation to sulphate generalized path.
SO4=
Polythionates
S=
S=
MS M=
M=
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 2. Experimental set-up for the thiosalts generation studies.
Acid
Lime
Mass flowcontroler
Air
To drain
Hot waterCold water
Solenidvalves
Stainlesssteel coil
Sampling valve
Stirrer
Poroussteel plate
pH OR
PC
ondu
ctiv
ity
DO
Tem
p .
Data Acquisition and Control System
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 3. Representative backscattered electron (BSE) photomicrograph of SAR-Ore (F).
po
qtz
pe
po
pe
cp
pe
Mag
MagMag
po
po
po
po
po
po po
po
po
po
cp
cp
pe
pe
pe
pe
pe
cp
fsp
fsp
fsp
fsp
fsp
fsp
fsp
qtz
qtz
amph
musc
qtz
fsp cpfsp
cp
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 4. BSE photomicrograph of SAR-Ore (F).
Figure 5. BSE photomicrograph of SAR-Ore.
Po
Pe
cp
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 6. Representative BSE photomicrograph of various sulphides and gangue minerals in LVR-Ore.
py py
py
pypy
py
py py
py
py
py
py
cp
cp
cp sid
sid
sid
sid chl
chl
chl
Fe Dol qtz
qtz appo
py
py
py
biot
chlpy
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 7. BSE photomicrograph of a composite particle made of pyrite, chalcopyrite and
quartz.
py
cp
qtz
sp
Mg-sidpo
ga
unknown
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 8. Backscattered electron (BSE) photomicrograph of an unknown sulfosalt (white) in sphalerite (light gray), magnesian siderite (medium gray) and
quartz (dark gray).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 9. BSE photomicrograph of a rhombohedral magnesian siderite grain.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 10. BSE photomicrograph of liberated pyrrhotite displaying variable sizes.
Figure 11. BSE photomicrograph of liberated pyrite and chalcopyrite grains LVR5-LLL.
Py
py
cp
py py
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 12. BSE photomicrograph of carbonate grains in LVR5-LLL.
Mg-sid
Mg-sid
dol
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 13. BSE photomicrograph showing chalcopyrite attached to an anhedral pyrite
grain in LVR7-MMM.
py
cp
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
40
50
60
70
80
90
100
110
120
40 50 60 70 80 90 100 110 120
Actual Value (g/t)
Pre
dict
ed V
alue
(g/t)
Figure 14. Total thiosalts prediction model adequacy for the pyritic ore.
75
125
175
225
275
325
375
425
475
75 125 175 225 275 325 375 425 475
Actual Value (g/t)
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 15. Total thiosalts prediction model adequacy for the pyrrhotitic ore.
0
50
100
150
200
250
300
350
7 12 17 22 27
Temperature, 0C
Pyritic Cu-Zn ore Pyrrhotitic Cu-Ni ore
Figure 16. Effect of pulp temperature on thiosalts generation.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
0
50
100
150
200
250
300
7 7.5 8 8.5 9 9.5 10
pH
Pyritic Cu-Zn ore Pyrrhotitic Cu-Ni ore
Figure 17. Effect of pH on thiosalts generation during flotation under
constant temperature and residence time.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 18. Effect of pH and temperature on thiosalts generation for residence time of 22
minutes
pH
7.5 8.0 8.5 9.0 9.5 10.0
13.8
17.5
21.2
25.0
59
70
82
93
104
Tem
pera
ture
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
0
50
100
150
200
250
300
7 12 17 22 27 32
Residence tme, min.
Pyritic Cu-Zn ore Pyrrhotitic Cu-Ni ore
Figure 19. Effect of residence time on thiosalts generation.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 20. Overall effect of pH, temperature and residence time on total thiosalts generation
(pyritic ore).
pH
Residence time
A- A+B-
B+
C-
C+
50
51
78
81
74
84
111
124
Temperature
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 21. Overall effect of pH, temperature and residence time on total thiosalts generation
(pyrrhotitic ore).
pH
Residence time
A- A+B-
B+
C-
C+
82
126
224
373
119
284
288
397
Temperature
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
0
10
20
30
40
50
60
100% MS (50:50) SS/MS MIX 100% SS
Grinding media composition
0
1
2
3
4
5
6
7
8
Conductivity TTS DO pH
Figure 22. Effect of grinding media composition on total thiosalt generation by the
pyritic ore at natural pH.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
0
10
20
30
40
50
60
70
100% MS (50:50) SS/MS MIX 100% SS
Grinding media composition
0
1
2
3
4
5
6
7
8
Conductivity TTS DO pH
Figure 23. Effect of grinding media composition on total thiosalt generation
by the
pyrrhotitic ore at natural pH.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Grinding media effect on total thiosalt (TTS) generation
0
20
40
60
80
100
120
100% MS SS/MS MIX 100% SS
Grinding media composition
Pyritic ore (Louvicourt)Pyrrhotitic ore (Strathcona)
Figure 24. Comparison of grinding media effects on pyritic and pyrrhotitic ores based on total
thiosalts generation at natural pH.
Change in grinding mill discharge pH
6.06.57.07.58.08.59.09.5
10.0
0 1000 2000 3000 4000
lime (g/t)
Pyritic orePyrrhotitic ore
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 25. Change in grinding mill discharge pH as a function of lime addition rate.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
TTS (g/t) = 46pH - 254.07
TTS(g/t) = 49pH - 323.87
0
20
40
60
80
100
120
140
160
180
200
6.5 7 7.5 8 8.5 9 9.5 10
Mill discharge solution pH
Pyritic ore (Louvicourt)Pyrrhotitic ore (Strathcona)
Figure 26. Effect of lime controlled grinding pH on thiosalts generation.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Tailings
68 ppm
300
20
Aeration
Cu/Rghr/Scvr
Cu Concentrate
Zn rougher
3-stage Zn
Cleaner
Zn Concentrate
3-stage Cu
Cleaner
Zn Scavenger
52 ppm
39 ppm
70 ppm 68 ppm
71 ppm
200
100
50
L/ i
60
50 mL/min. water
20 mL/min
290
mL/min
50 mL/min
Conditioning
Classificati
Rod
Mill
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 27. Experimental continuous grinding, classification and flotation circuit (200 g/min
throughput).
Figure 28. Distribution of the total thiosalts among the major process and the ore.
23
17
5
50
5
0
10
20
30
40
50
60
Mill Feed Grinding Aeration Cu circuit Zn circuit
Circuit
Estim
ated
con
trib
utio
n [%
]
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
125 g
pH adjusted
Conc. recovery
controlling balance
In-line
concentrate
filtering funnel
Automatic froth
take-off assembly
Air
Automatic froth level
controller assembly
pH, ORP, DO
and T sensors
Flotation cell
3 L/min Air
Air flow controller
Pump
Vacuum
pump
Pulp zone
Froth
100 g
Concentrate
t i hi
Vacuum
pump
PC based data acquisition and
froth
depth
diffuser
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 29. The PC controlled automatic flotation cell.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
tap water
-10 mesh
sample
AerationConditioning
Activation with CuSO4Conditioning
with SIPX
Grinding Circuit
Primary conditioning
Cu Flotation Circuit
Zn conditioning circuit
Zn Flotation Circuit
Stainless
steel rod
Zn rougher flotation
Zn Scavenger
Zn cleaner flotation
Cu rougher flotation
Cu Scavenger flotation
Cu cleaner flotation
ST ST
ST
ST ST
ST tap
water ST ST
ST
ST 10
ST ST 12
ST 13 tap
water ST 14
ST 14
ST 16
ST 15
Zn cleaner tails
Zn concentrate Final tails
Cu concentrate
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 30. Semi-batch test flowsheet used to investigate thiosalts generation in various
circuits (Louvicourt).
Figure 31. Distribution of thiosalts generated among sub-processes.
14
33
14
11 12
-1
13 13
-505
1015202530354045
Mill Fee
d
Grindin
g
10 m
in eq
uilibr
ation
6 min
aerat
ion
Cu Rou
gher+
Sca
veng
er
Cu Clea
ning
Zn con
dition
ing
Zn RGHR+S
CAVENGER
Zn Clea
ning
Sub-process
Thio
salts
[%]
Conditioning
Cu circuit flotation
Zn circuit flotation
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 32. Semi-batch test flowsheet used to investigate thiosalts generation in various
circuits (Strathcona).
tap water
-10 mesh sample
10 min6 min
Magnetic Separation
Grinding Circuit
Primary conditioning
Cu-Ni Flotation
Pyrrhotite Rejection Circuit
Rod mill
Stainless
PO Rejection
Scavenger
PO Rejection Rougher
Cu-Ni Rougher I flotation
Cu-Ni Rougher II flotation
Cu-Ni cleaner flotation
ST
ST
ST
ST
ST
ST
CuSO4
ST 12
ST
ST 17
ST 18ST 16
ST 14
ST 15
Pyrrhotite tailings
Cu-Ni Concentrate
ST
3 min
Cu-Ni Scavenger flotation
ST 10 ST 11
ST 13
ST
tap water
tap water
tap water
Magnetic
Nonmagnetic
Ball mill
Mild steel
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
6.3 7.4
15.9 16.5
29.3
4.51.6
4.56.2
0
5
10
15
20
25
30
35
Sub processes
Figure 33. Proportion of total thiosalts generated in various process circuits.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
15 min. 20 min. 20 min.20 min.
Air 2.5 L/min.
Nitrogen gas
FreezerConcentrate Middlings
tap waterFiltrate (discarded)
Wermco Scrubber
10 min. conditioningwith Xanthate
deoxygenated tap water
Pressure filter -10 mesh sample
Table concentrate
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 34. Sample preparation, grinding and flotation simulation of Louvicourt pyritic Cu-
Zn ore.
5 min. conditioning No air, no reagent
15 min. 20 min. 20 min. 20 min.
Air
2 5 L/min
Nitrogen gas
Eriez Drum Magnetic Separator
Freezer Non Mag Mag
tap water Filtrate (discarded)
Wermco Scrubber
10 min. conditioningwith Xanthate
deoxygenated tap water
Pressure filter
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 35. Sample preparation, grinding and flotation simulation of Strathcona pyrrhotitic Cu-Ni ore.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 36. BSE photomicrograph of pyrite grains attached to and encapsulated in gangue
(chlorite, quartz and muscovite).
Figure 37. BSE photomicrograph of a pyrite grain attached to and encapsulated in gangue.
Note the sharp grain boundaries on exposed surfaces of pyrite grains.
py
chl
musc+qtz
py
chl
mag
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 38. Effect of mineralogical composition of Louvicourt ore on total thiosalts
generation rate.
Change in rate of total thiosalts generation with time
0.0
0.4
0.8
1.2
1.6
2.0
Time interval (min.)
LVT1 0.89 0.51 0.58 1.06 1.16
LVT2 1.06 0.62 1.03 1.40 1.49
LVT3 1.24 0.26 0.77 1.34 1.44
LVT4 0.53 0.92 1.28 1.77 1.47
32 min. grinding, 5 min.
conditioning 5-20 20-40 40-60 60-80
Aeration
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 39. Dissolved oxygen concentration and pulp oxidation-reduction potential data for LVT4.
-300
-200
-100
0
100
200
300
0 10 20 30 40 50 60 70 80 90
Residence time [min.]
Oxi
datio
n R
educ
tion
Pot
entia
l [m
V, P
t vs.
SC
E]
0
2
4
6
8
10
12
Dis
solv
ed O
xyge
n C
once
ntra
tion
[mg/
L]
ORP [mV, Pt vs. SCE]
Dissolved Oxygen [mg/L]
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
-240
-200
-160
-120
-80
-40
0
40
80
120
160
200
240
280
0 10 20 30 40 50 60 70 80 90 100
Residence time [min.]
Pulp
Oxi
datio
n re
duct
ion
pote
ntia
l (m
V, S
CE)
LVT1LVT2LVT3LVT4
Figure 40. Change in pulp oxidation-reduction potential with residence time.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
9
0 10 20 30 40 50 60 70 80
Residence time [min.]
pH
LVT1
LVT2
LVT3
LVT4
LVT3LVT1
LVT2
LVT4
Figure 41. Louvicourt test. Change in pH with residence time.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
100
150
200
250
300
350
400
0 20 40 60 80 100
Residence time [min.]
LVT1LVT2LVT3LVT4
Figure 42. Pulp conductivity
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 43. Representative BSE photomicrograph of various sulphides from SAMM-HEAD.
mag
cubpo
po
po
cp
cp
pe
po po
po po
popo
pe
cp
cp
po
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 44. Representative BSE photomicrograph of various sulphides in SAMM6
Figure 45. Representative BSE photomicrograph of various gangue minerals in SAMM5.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 46. BSE photomicrograph of pyrrhotite surrounded by fine particles of pyrrhotite.
fsp
fsp
fsp
fsp
fsp
cpx
qtz pe
chl
cp
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 47. Representative BSE photomicrograph of pyrrhotite SAMM5.
po
po
po
po
pomag
Po+mag
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 48. Effect of mineralogical composition of Strathcona ore on total thiosalts
generation rate.
Effect of mineralogical composition on total thiosalts generation
0
100
200
300
400
500
600
700
0 5 15 35 55 75 85Residence time [min.]
Cum
ulat
ive
thio
salts
gen
erat
ed [g
/t]
Originalsample0%
10%
30%
50%
70%
90%
100%
Magnetic fraction
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Figure 49. Change in rate [g/t/min] of total thiosalts generation (Strathcona ore).
Change in rates of total thiosalts generation with time
0
2
4
6
8
10
12
14
Time interval
Ave
rage
rate
of T
TS g
ener
atio
n (g
/t/m
in)
SAH [Head] 4.12 2.13 5.20 3.30 3.40
SAMM7 [0%] 5.23 1.33 1.20 1.20 0.90
SAMM1 [10%] 2.93 2.27 1.90 0.30 1.80
SAMM2 [30%] 3.07 5.07 2.60 1.10 1.70
SAMM [50%] 1.21 8.13 3.80 1.40 3.30
SAMM3 [70%] 3.31 10.27 5.10 3.00 2.90
SAMM 4 [90%] 6.41 13.20 7.10 4.00 3.50
SAMM6 [100%] 4.25 11.60 4.90 5.10 3.80
0-5 (no air) 5-20 20-40 40-60 60-80
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
Total thiosalts generation rate as a function of total metallic mineral components
0
2
4
6
8
10
12
14
0 20 40 60 80
Total metallic mineral component [%]
5-20
20-40
40-60
60-80
Time interval [min]
Figure 50. Thiosalts generation rate as a function of residence time interval and sulphide
mineral
content of samples.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
R2 = 0.97
R2 = 0.98
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
0 10 20 30 40 50 60 70
Mineral Abundance [%]
Spoe
cific
thio
salts
pro
duct
ion
rate
[g/t/
min
]
Pyrrhotite + Chalcopyrite + PentlanditePyrrhotite
Figure 51. Comparison of correlations between initial thiosalts generation rate
(g/t/min.)
and mineral quantities (first 15 minutes of processing).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
R2 = 0.89
R2 = 0.88
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 10 20 30 40 50 60 70
Mineral Abundance [%]
Thio
salts
pro
duct
ion
rate
[g/t/
min
]
Pyrrhotite + Chalcopyrite + PentlanditePyrrhotite
Figure 52. Comparison of correlations between initial thiosalts generation rate (g/t/min.)
and mineral quantities (last 20 minutes of processing).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
y = 0.6447e0.1057x
R2 = 0.99
y = 0.6027e0.1446x
R2 = 0.98
y = 0.6717e0.0782x
R2 = 0.86
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 5 10 15 20 25
Bulk sulphur assay [%]
5-20 min.20-40 min.60-80 min.
Time Interval
Figure 53. Thiosalts generation rate (g/t/min.) as a function of bulk sulphur assays (%).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
-250
-200
-150
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100
Residence time [min.]
Oxi
datio
n-R
educ
tion
Pote
ntia
l (m
V vs
. SC
E)
Magnetic
Non Magnetic
Figure 54. Change in pulp oxidation-reduction potential (SAMM6, magnetic and
SAMM7
non-magnetic samples).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
7.8
8
8.2
8.4
8.6
8.8
9
9.2
0 20 40 60 80 100 120
Residence time [min.]
pH
MagneticNon Magnetic
Figure 55. Change in pulp pH (SAMM6, magnetic and SAMM7 non-magnetic samples).
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
320
330
340
350
360
370
380
390
0 20 40 60 80
Potassium amyl xanthate (g/t)
Thio
salts
(g/t)
Figure 56. Effect of Xanthate addition rate on thiosalts generation.
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
APPENDIX B PULP SAMPLES COLLECTED AT THE MILLS
AND MEASUREMENTS
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
B-1
Appendix B
Louvicourt Mill
Field ID Lab ID T
(ºC) pH ORP Conductivity
(µ) DO
(mg/L) #1 LC1 21.1 6.6 151 1476 5.3#2 LC2 23.7 11.1 -59 23300 1.56#3 LC3 24.4 10.6 -35.4 172 3.3#4 LC4 26.5 10.7 -27 2060 1.8#5 LC5 25.4 10.6 -23 2060 3.5#6 LC6 22.4 9.7 22.8 1584 4#7 LC7 24.8 10.4 -18.3 2070 1.2#8 LC8 22.9 9.7 22.5 1653 2.3#9 LC9 24.0 9.5 16 2130 2.1#10 LC10 22.7 9.4 39.5 1898 2.8#11 LC11 24.2 9.9 21 1998 1.2#12 LC12 Sampled with #10 #1012 LC1012 23.0 9.3 61.5 1909 2.61#13 LC13 24.4 9.6 20 2230 1.3#14 LC14 21.6 9.1 35 1693 4.6#15 LC15 22.5 9.3 36.4 1719 3.3#16 LC16 22.2 9.6 39.4 1636 2.2#SP1 LC17 20.6 9.4 56 1518 3.6#18 LC18 23.5 9.0 19 1823 1.2#19 LC19 20.4 9.0 79 904 5.1#20 LC20 23.3 9.4 44 1833 2.4#21 = #32 LC21 21.6 9.3 50 1629 5.1#22 LC22 25.0 10.8 -24 2200 1.5#23 Sampled with #23 #24 Sampled with #24 #2324 LC2324 20.0 9.3 64 1587 4.7#25 LC25 23.0 10.0 18 2200 2.5#26 LC26 19.9 9.2 55 1334 5.58#27 LC27 22.0 9.6 40 1508 3.9#28 LC28 19.6 9.2 72.7 1298 6#29 LC29 18.2 8.5 128 1197 7.3#30 LC30 19.5 9.0 100 1495 5.6#31 LC31 21.9 9.3 60 1492 4.0#SP3 LC32 21.5 10.6 -6.9 1630 2.9#33 LC33 21.7 8.4 120 1134 0.7#34 LC34 23.7 9.8 -17 2210 1.65#35 LC35 Same as #21 #36 LC36 21.6 11.8 -68 3000 3.92Tap water LC36 22.8 6.5 215 335 5.2
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
B-2
Appendix B
Strathcona Mill
Sample ID ORP DO
(mg/L) T
(ºC) pH Conductivity
(µs)
Tap Water 233 11.5 6.8 170 23 135 4.47 12.3 6.28 2570 26 -87 1.00 15.7 10.65 2930 19 72 4.86 14.9 8.32 3160 62 -62.7 6.20 12.4 12.14 6840 20 65.3 4.71 15.2 8.65 3240 2 2.8 1.04 16.1 9.84 3400 27 -92.4 1.42 16.7 10.64 2910 3 -28.3 4.20 17.3 9.56 3800 57 -17.8 2.39 15.2 8.77 2600 56 +111.92 9.00 11.2 7.84 1845 35 +27 6.52 13.6 9.25 2590 25 +84.3 6.49 13.7 8.38 2400 36 +15 5.06 15.3 8.72 2890 16 +56.5 6.7 15.2 8.08 3370 43 -19 5.0 13.4 9.29 2180 4 +85.8 3.8 13.7 8.68 2600 15 +39.2 6.9 15.2 7.79 3290 24 +84.5 4.92 13.3 8.01 2440 68 -76.6 4.51 13.2 12.20 8140 54 +50.4 7.85 14.5 9.50 2590 48 -38.1 7.81 14.2 11.61 2740 18 +63.4 4.8 15.5 8.90 2700 55 -25 6.4 14.9 10.40 2720 49 -79 7.0 14.9 12.08 8070 ST13-2 -61 5.6 13.8 11.93 4600 ST-27 -26 9.7 13.7 11.45 2360 ST-15 +147 8.9 13.7 8.98 2560 ST-13-4 -53 6.8 13.5 11.93 4920 ST-28 -14.7 2.74 13.2 11.33 2330 ST-21 78 7.3 13.8 9.33 2930 ST-1 +190 9.70 12.7 8.04 1766 ST-14A None ST-19B +12.4 8.56 13.4 10.81 2790 ST-20 +72.5 8.6 14.4 9.56 2890 ST-30 -30.4 3.1 13.1 10.73 2750 ST-29 +13.5 9.3 12.7 10.20 2680 ST-14B -111.7 5.6 14.0 10.97 2460
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
APPENDIX C THIOSALTS (INDIVIDUAL SPECIES
AND TOTAL THIOSALTS)
ANALYSIS OF THE PULP SAMPLES
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
C-1
Strathcona Mill ST1 ST2 A ST7 ST9 ST10 ST11A ST11B ST12 ST23 ST26
Fe+2 ppm <1 <1 <1 <1 <1 <1 <1 <1 <1 <1
SO4 ppm 670 1138 802 1081 738 750 769 689 583 721
S2O3 ppm 3 255 417 232 583 431 523 238 50 213
Thiosalt mg/L 13 599 556 564 706 535 624 318 60 301
S3O6 ppm 10 277 108 206 9 85 87 52 10 23
S4O6 ppm <5 5 52 58 <5 <5 44 28 <5 <5
Ca ppm 205 328 213 311 332 289 277 240 374
Cu ppm 0.78 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2
Mg ppm 13.2 2.06 2.95 9.72 0.14 0.18 2.72 5.95 <0.06 <0.06
S ppm 192 407 358 415 1179 820 580 435 216 321
Zn ppm 0.24 0.038 0.027 0.032 0.03 0.014 0.033 0.033 0.031 0.038
Fe ppm 0.06 <0.13 <0.13 <0.13 <0.13 <0.13 <0.13 0.13 <0.13 <0.13
Na mg/L 106 77 44.4 99.7 83.9 76 58.2 90.8 98.7 90
K mg/L 24.1 37.1 17.4 56.2 32.5 27.1 18.1 23.2 22.7 30.2
THIOSALTS CONSORTIUM PROTECTED BUSINESS INFORMATION Project No. 601838
C-2
Louvicourt Mill LC1 LC4 LC6 LC13 LC20 LC21 LC22 LC25 LC29 LC31
Fe+2 ppm < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1
SO4 ppm 88 103 123 145 231 149 273 187 78 172
S2O3 ppm 21 < 5 < 5 < 5 5 < 5 9 6 23 9
Thiosalt mg/L 292 421 323 436 500 349 449 445 210 260
S3O6 ppm 558 595 574 538 452 548 564 501 402 596
S4O6 ppm 44 27 44 33
Ca ppm 23 37.7 26.6 32.4 26.7 26 30.4 29.3 17.3 21.1
Cu ppm 36.5 58.9 41.7 50 40.9 39.3 47.8 45.7 29.2 31.9
Mg ppm 348 429 373 430 404 378 424 418 249 366
S ppm <0.2 <0.2 0.47 <0.2 0.41 0.24 <0.2 0.25 2.53 2.07
Zn ppm <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09
Fe ppm 4.01 0.31 3.01 2.48 2.67 3.57 0.57 1.26 3.81 2.79
Na mg/L 404 923 470 829 629 510 844 1006 315 422
K mg/L <0.06 <0.06 <0.06 <0.06 <0.06 <0.06 <0.06 0.07 0.09 <0.06