a novel process for the treatment of copper concentrates · a novel process for the treatment of...

David G Dixon, UBC Hydrometallurgy

GALVANOXTM – A Novel Process for Copper Concentrates

GALVANOXTM

A Novel Process for the Treatment

of Copper Concentrates

David G. Dixon

UBC Hydrometallurgy



GALVANOX HISTORY

GALVANOX FEATURES

GALVANOX CHEMISTRY

BATCH LEACHING RESULTS

PILOT LEACHING RESULTS

PROCESS FLOWSHEET OPTIONS

PROCESS COMPARISONS

COMMERCIAL EVALUATION

CONCLUSIONS

PRESENTATION OUTLINE



UBC researchers Dave Dixon and Alain Tshilombo developed a novel

process for galvanically-assisted atmospheric leaching of primary

copper concentrates in early 2004.

A preliminary patent application was filed in June 2004.

Several patent applications were filed in 2005 (US, Chile, Peru, Laos),

and successful PCT examination in September 2006 spawned many

other national phase applications.

UBC entered into an exclusive marketing agreement with Bateman

Engineering in October 2006, and is working closely with Bateman to

identify potential applications of the process.

Batch testing programs on many candidate concentrates have been

initiated or completed, continuous leaching was piloted in May, and

three detailed feasibility studies are currently underway, with

integrated pilot campaigns planned to begin in November.

GALVANOX HISTORY



Atmospheric Leach (~80°C)

No microbes

Pure sulphate medium (no chloride)

Conventional materials of construction

No fine grinding

Generates elemental sulfur (> 95%), low oxygen demand

No surfactants

Selective for chalcopyrite over pyrite (can cost-effectively treat low

grade concentrates down to 9% copper or less)

Complete copper recovery, typically in less than 12 hours, and

sometimes in as little as 4 hours

Fully compatible with conventional SX-EW

GALVANOX FEATURES



GALVANOX takes advantage of the galvanic effect between

chalcopyrite and pyrite.

Chalcopyrite is a semiconductor, and therefore corrodes

electrochemically in oxidizing solutions.

In ferric sulphate media, the overall leaching reaction is as follows:

CuFeS2 + 2 Fe2(SO4)3 → CuSO4 + 5 FeSO4 + 2 S0

This reaction may be represented as a combination of anodic and

cathodic half-cell reactions:

Anodic: CuFeS2 → Cu2+ + Fe2+ + 2 S0 + 4 e–

Cathodic: 4 Fe3+ + 4 e– → 4 Fe2+

GALVANOX CHEMISTRY



UNASSISTED CHALCOPYRITE LEACHING

Cu2+

Fe2+

4 Fe3+

4 Fe2+

So

4 e-

CuFeS2

Anodic Site Cathodic Site



UNASSISTED CHALCOPYRITE LEACHING



Typically, chalcopyrite surfaces are passivated (i.e., they

become resistant to electrochemical breakdown) in ferric sulfate

solutions at even modest solution potential levels.

It is widely held that this results from the formation of some sort

of passivating film on the mineral surface that most likely

consists of an altered, partially Fe-depleted sulfide layer.

Because of this, most investigators have assumed that it is the

anodic half-cell reaction that limits the overall rate of leaching.

However, we discovered that it is primarily the cathodic half-cell

reaction (i.e., ferric reduction) that is slow on the passivated

chalcopyrite surface.

GALVANOX CHEMISTRY



The presence of pyrite facilitates chalcopyrite leaching by

providing an alternative surface for ferric reduction

This essentially eliminates cathodic passivation of chalcopyrite

in ferric sulfate solutions.

Also, by ensuring rapid chalcopyrite oxidation, the solution

potential is easily maintained at levels low enough to prevent

anodic passivation of the chalcopyrite

This also prevents anodic breakdown of the pyrite, which

remains more or less completely inert.

GALVANOX CHEMISTRY



GALVANICALLY-ASSISTED

CHALCOPYRITE LEACHING

Cu2+

Fe2+

So

Py

Py

Cp

4 e- 4 e-

4 Fe3+

4 Fe2+

Anodic Site Cathodic Site



GALVANICALLY-ASSISTED

CHALCOPYRITE LEACHING

Partially leached particle Completely leached particles



The ferric required for GALVANOX leaching is regenerated in situ with

oxygen gas

Ferric leaching of chalcopyrite:

CuFeS2 + 2 Fe2(SO4)3 → CuSO4 + 5 FeSO4 + 2 S0

Oxidation of ferrous with dissolved oxygen gas:

4 FeSO4 + O2 + 2 H2SO4 → 2 Fe2(SO4)3 + 2 H2O

Overall leaching reaction:

CuFeS2 + O2 + 2 H2SO4 → CuSO4 + FeSO4 + 2 S0 + 2 H2O

GALVANOX CHEMISTRY



GALVANOX leaching is followed by conventional solvent extraction and

electrowinning to recover LME Grade A pure copper cathodes

Copper electrowinning:

CuSO4 + H2O → Cu0 + ½ O2 ↑ + H2SO4

GALVANOX CHEMISTRY



Iron is rejected from the Galvanox circuit by oxyhydrolysis in an

autoclave at ~220°C to make hematite, which is easy to filter and

perfectly suitable for disposal

Iron oxyhydrolysis:

4 FeSO4 + O2 + 4 H2O → 2 Fe2O3 (s) + 4 H2SO4

This autoclave also treats a portion of the concentrate feed, in order to

generate the heat required for the atmospheric leach circuit, and also to

generate extra acid as required for secondary sulfides or acid-

consuming gangue minerals in the concentrate

GALVANOX CHEMISTRY



In summary, the overall GALVANOX process chemistry is as follows:

Galvanically-assisted atmospheric leaching of chalcopyrite:

CuFeS2 + O2 + 2 H2SO4 → CuSO4 + FeSO4 + 2 S0 + 2 H2O

Iron oxyhydrolysis:

FeSO4 + ¼ O2 + H2O → ½ Fe2O3 (s) + H2SO4

Copper electrowinning:

CuSO4 + H2O → Cu0 + ½ O2 ↑ + H2SO4

Overall process chemistry:

CuFeS2 + 5/4 O2 → Cu0 + 2 S0 + ½ O2 ↑ + ½ Fe2O3 (s)

GALVANOX CHEMISTRY



BATCH TESTING

APPARATUS

Six 3-L jacketed reactors

Water baths for

temperature control

Digital oxygen mass flow

meters for potential control

Automated data

acquisition for potential,

pH and temperature



CHALCOPYRITE CONCENTRATE – 35% Cu

Effect of pyrite addition (50 g con, 65 g acid, 470 mV, 80°C)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

Py = 150 g (K5)

Py = 100 g (K9)

Py = 50 g (K6)

Py = 25 g (K10)

Py = 0 g (K1)




Effect of sulfuric acid addition (50 g con, 100 g Py, 470 mV, 80°C)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

Ac = 90 g (1.80 kg/kg) (K16)

Ac = 80 g (1.60 kg/kg) (K14)

Ac = 68 g (1.36 kg/kg) (K9)

Ac = 55 g (1.10 kg/kg) (K13)

Ac = 45 g (0.90 kg/kg) (K15)



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

E = 485 mV (K20)

E = 470 mV (K16)

E = 455 mV (K19)

E = 440 mV (K18)

E = 425 mV (K17)


Effect of solution potential (50 g con, 100 g Py, 90 g acid, 80°C)



400

410

420

430

440

450

460

470

480

490

500

0 4 8 12 16 20 24

Time (h)

So

lutio

n P

ote

ntia

l (m

V v

s A

g/A

gC

l)CHALCOPYRITE CONCENTRATE – 35% Cu

Effect of solution potential (50 g con, 100 g Py, 90 g acid, 80°C)



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

T = 80°C (K16)

T = 70°C (K22)

T = 60°C (K21)


Effect of temperature (50 g con, 100 g Py, 90 g acid, 470 mV)



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

Baseline (K16)

Alt. Baseline (K25A)

+ K25A Continued (K25B)

+ K5 Residue + 7.5 g Cu (K24)

+ K8 Residue (K23)


Effect of pyrite recycle (50 g con, 100 g Py, 90 g acid, 470 mV, 80°C)



0 4 8 12

Time (h)

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

pH

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12

Time (h)

Cu

Re

co

ve

ry

Alt. Baseline (K25A)

+ K25A Continued (K25B)

+ K5 Residue + 7.5 g Cu (K24)


At constant solution potential, pH is an indicator of reaction progress



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

Galvanox Leaching

No Pyrite

CHALCOPYRITE CONC 2 – 23.6% Cu

Effect of pyrite addition (30 g con, 120 g Py, 30 g acid, 480 mV, 80°C)



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ry

Galvanox Leaching

No Pyrite





0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 4 8 12 16 20 24

Time (h)

Cu

Re

co

ve

ryCHALCOPYRITE BULK CONC – 10.2% Cu

150 g bulk con @ ~1.21 Py/Cp ratio, 75 g acid, 440 mV, 80°C)



BULK CONC RESIDUE – 22.8 g/t Au

77 g Galvanox residue @ 0.5 g/L NaCN, pH 11, room temp

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 12 24 36 48

Time (h)

Au e

xtr

action

0

1

2

3

4

5

6

0 12 24 36 48

Time (h)

NaC

N c

onsum

ption (

kg/t

)



GALVANOX is robust (insensitive to the source of chalcopyrite)

Process optimization is straightforward:

Pyrite-to-chalcopyrite ratio (2:1 to 4:1 typically optimal)

Acid concentration (stoichiometric + modest excess)

Solution potential (> 440 mV)

Temperature (> 70°C)

Recycled pyrite is equally as effective as fresh pyrite

Under the correct process conditions, GALVANOX leaching is

very rapid (limited by the rate of gas-liquid mixing)

High Au extractions from GALVANOX residues are feasible, with

relatively modest cyanide consumption levels

SUMMARY OF LEACH RESULTS



FIRST GALVANOX COPPER

(99.85% Cu directly from PLS at 50 g/L Fe!)



QUESTIONS ?

For more information, please visit:

www.GALVANOX.com

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