Effects of enhanced pyrite on the Galvanox™process • In the Galvanox process, pyrite samples...

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


0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Time (h)

Copper Extraction

Pyrite #1, 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


Silver-enhanced pyrite addition


0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Time (h)

Copper Extraction



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



Comparison


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


Silver-to-pyrite ratio


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



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




450 mV 420 mV 450 mV 420 mV


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





10 g/L Cu concentrate, T = 80°C


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


Same Silver Added, No Pyrite Added, E = 450 mV


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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Effects of enhanced pyrite on the Galvanox™process • In the Galvanox process, pyrite samples...

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