effects of enhanced pyrite on the galvanox™process • in the galvanox process, pyrite samples...
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Effects of enhanced pyrite on the
Galvanox™ process
Ghazaleh Nazari
Supervisors: Dr. Dixon and Dr. Dreisinger
The University of British Columbia
Outline
• Chalcopyrite Leaching
• The Galvanox™ Process
• Motivations and Objectives
• Experiments and Results
• Conclusions
Chalcopyrite Leaching
• Chalcopyrite, CuFeS2, the most abundant
source of copper in the world
• Various hydrometallurgical processes:
– Sulfate
– Chloride
– Ammonia
– Nitrate
Sulfate Processes
• Advantages:
– Simplicity of the leaching reactions
– Low capital cost
– Low operating cost
– Conventional SX/EW
• Disadvantages
– Slow leaching rates
– Low copper recoveries
• Pyrite-catalyzed atmospheric leaching
• Low-cost atmospheric leaching tanks
• Low oxygen consumption
• Low sulfuric acid generation
• Safe disposal of iron (as hematite) to tails
• No chloride, nitrate, or ammonia
• No surfactants
• No microbes
• No ultrafine grinding
The Galvanox™ Process
Motivation
• In the Galvanox™ process, pyrite samples from
various sources can influence the rate of
chalcopyrite leaching differently
• The effectiveness of pyrite on the kinetics of
chalcopyrite leaching has a strong correlation with
the amount of silver on pyrite
Objectives
1. To investigate the use of silver enhanced pyrite in
the Galvanox™ process to improve the extraction
of copper from chalcopyrite
2. To develop a comprehensive understanding of the
mechanism of this process
Experimental Apparatus
Silver Enhanced Pyrite
• 0.5 L of solution containing the desired amount of silver is
prepared
• Silver is added as silver nitrate solution
• The solution is well mixed using a magnetic stirrer
• Fifty grams of pyrite are added and allowed to react with the silver
until no silver is detected in the solution
• Pulp density is held at 10% to ensure a high degree of mixing by
the magnetic stirrer in the glass beaker
• the solid residue is filtered and rinsed several times with water
Experiments• Investigating the effect of various parameters on the
kinetics of chalcopyrite leaching:
– Silver concentration on pyrite
– Solution potential
– Pyrite recycle
– Pulp density
• Comparison of silver-catalyzed leaching and silver-
enhanced pyrite-catalyzed leaching
Mineralogy
MineralCopper Conc
(%)
Pyrite #1
(%)
Pyrite #2
(%)
Pyrite #3
(%)
Pyrite 15.9 97.6 70.8 95.6
Chalcopyrite 78 — 4.0 —
Quartz 1 0.6 1.9 1.3
Biotite 1.8 — — 0.9
Dolomite 1.1 — 12.2 —
Plagioclase 2.2 — — —
Anhydrite — 1.8 — —
Gypsum — — 3.4 0.6
Calcite — — — 1.6
Pyrrhotite — — 2.1 —
Clinochlore — — 2.2 —
Muscovite — — 3.4 —
Elemental composition
Element Copper Conc Pyrite #1 Pyrite #2 Pyrite #3
Cu 27.00 % 0.13 % 1.8 % 9 ppm
Fe 31.14 % 45.43 % 38.02 % 44.94 %
S 36.70 % 52.62 % 45.3 % 51.36 %
Mg 0.27 % 0.04 % 1.88 % < 0.01 %
Co 0.16 % — 68 ppm —
Pb — 0.14 % 48 ppm < 2 ppm
As 130 ppm — 49 ppm 10 ppm
Ag 15.5 ppm 21 ppm 2 ppm < 0.5 ppm
Ca 0.47 % 0.56 % 4.05 % 0.69 %
Al 0.51 % 0.02 % 0.41 % 0.18 %
Zn 0.01 % — 441 ppm 71 ppm
Si 1.14 % 0.28 % 1.18 % 1.2 %
Unassisted chalcopyrite leaching
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
0%
20%
40%
60%
80%
100%
0 10 20 30 40 50 60 70 80 90
Time (h)
Copper Extraction
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)
Copper Extraction
Pyrite #1, Py/Cp = 6
Pyrite #2, Py/Cp = 6
Pyrite #3, Py/Cp = 6
Natural pyrite addition
0%
20%
40%
60%
80%
100%
0 2 4 6 8 10
Time (h)
Copper Extraction
Pyrite #3, Py/Cp = 6, Ag/Py = 100 ppm
Pyrite #1,Py/Cp = 6, Ag/Py = 100 ppm
Pyrite #2,Py/Cp = 6, Ag/Py = 100 ppm
Silver-enhanced pyrite addition
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)
Copper Extraction
Pyrite #1, Py/Cp = 6
Pyrite #2, Py/Cp = 6
Pyrite #3, Py/Cp = 60%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)Copper Extraction
Pyrite #3, Py/Cp = 6, Ag/Py = 100 ppm
Pyrite #1,Py/Cp = 6, Ag/Py = 100 ppm
Pyrite #2,Py/Cp = 6, Ag/Py = 100 ppm
Comparison
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
Natural pyrite addition
0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)
Copper Extraction
Py/Cp = 6, Ag/Py = 0, E = 470 mV
Py/Cp = 4, Ag/Py = 0, E = 470 mV 0%
20%
40%
60%
80%
100%
0 20 40 60 80 100 120
Time (h)
Copper Extraction
Py/Cp = 6, Ag/Py = 0, E = 470 mV, Py Recycle
Py/Cp = 4, Ag/Py = 0, E = 470 mV, Py Recycle
Fresh pyrite Recycled pyrite
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
Silver-to-pyrite ratio
Potential set point = 470 mV (vs. Ag/AgCl), T = 80°C
0%
20%
40%
60%
80%
100%
0 5 10 15 20 25 30 35 40
Time (h)
Copper Extraction
Py/Cp = 4, Ag/Py = 200 ppm
Py/Cp = 4, Ag/Py = 100 ppm
Py/Cp = 4, Ag/Py = 50 ppm
Solution potential set point
Py/Cp = 4, Ag/Py = 100 ppm, T = 80°C
0%
20%
40%
60%
80%
100%
0 5 10 15 20 25
Time (h)
Copper Extraction
Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mV0%
20%
40%
60%
80%
100%
0 10 20 30 40 50 60
Time (h)
Copper Extraction
Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mV, Py Recycle
450 mV 420 mV 450 mV 420 mV
Fresh pyrite Recycled pyrite
Recycled pyrite at low pulp density
0%
20%
40%
60%
80%
100%
0 10 20 30 40 50 60
Time (h)
Copper Extraction
Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mV
Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mV0%
20%
40%
60%
80%
100%
0 10 20 30 40 50 60
Time (h)
Copper Extraction
Py/Cp = 4, Ag/Py = 100 ppm, E = 450 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 440 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 470 mV, Py Recycle
Py/Cp = 4, Ag/Py = 100 ppm, E = 420 mV, Py Recycle
10 g/L Cu concentrate, T = 80°C
Fresh pyrite Recycled pyrite
High pulp density
0%
20%
40%
60%
80%
100%
0 2 4 6 8 10
Time (h)
Copper Extraction
Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mV, 2nd Py Recycle
Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mV, Fresh Py
Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mV, 1st Py Recycle
70 g/L Cu concentrate, T = 80°C
Silver Catalyzed Leaching
• The copper extraction from chalcopyrite in ferric
sulfate solution increases by addition of silver as a
soluble silver salt.
• Formation of an intermediate Ag2S film
CuFeS2 + 4 Ag+ → 2 Ag2S (chalcopyrite surface) + Cu2+ + Fe2+
Ag2S + 2 Fe3+ → 2 Ag+ + 2 Fe2+ + S0
Comparison of silver-catalyzed leaching and
enhanced pyrite-catalyzed leaching
0.61 g Ag/kg Cu, E = 450 mV, T = 80°C
0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)
Copper Extraction
Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mV
Same Silver Added, No Pyrite Added, E = 450 mV0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Time (h)
Copper Extraction
Py/Cp = 2, Ag/Py = 100 ppm, E = 450 mV, Py Recycle
Same Silver Added, No Pyrite Added, E = 450 mV
Fresh pyrite Recycled pyrite
Conclusions
• An improvement to the UBC Galvanox™ process has been developed
• Pyrite, enhanced with as little as 60 mg of silver per kg of copper, is sufficient to ensure complete copper extraction typically within 10 hours of leaching
• The silver enhanced pyrite can be recycled and reused with minimal loss and no need for a separate silver recovery step
• The fastest rate was observed at a solution potential of 450 mV
• Recycled pyrite is equally as effective as freshly enhanced pyrite as a catalyst
• Both weaknesses of silver catalyzed leaching, silver availability and toxicity, are overcome in this process
Thank You!
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