An investigation into the leaching of enargite under atmospheric

conditions

G. Csicsovszki, M. Gupta, J.G. Peacey

Queen`s University,

Canada

Overview of presentation

• Background

• Literature review

• Material and methods

• Review of shake flask test results

• Review of stirred reactor test results

• Conclusions

Background• Several high enargite deposits are currently being

developed

• Arsenic capacity of world`s Cu smelters is limited

• Roasting to produce a low-As calcine is the onlycommercially proven process

• Aqueous processing could be a more viable option

• Enargite can be even more refractory to commonlixiviants than chalcopyrite

• High temperature pressure leaching can extract >99%Cu in 2 h but maintenance intensive

Atmospheric Leaching Processes Proposed for Enargite Concentrates

• Xstrata`s Albion Process• Utilizes the Isamill for ultra-fine grinding (d90< 10

μm)

• Galvanox Process• 2-4 times excess of pyrite added for galvanically-

assisted leach

• Both processes claim enargite concentrates can beleached in <24 h.

• Objective of this study was to better understand theatmospheric leaching of enargite concentrate

Literature review

- Operating parameters of interest fromliterature:

Variable Effect on enargite dissolution

Temperature Increasing with variable

Particle size Decreasing with variable

Pyrite concentration Increasing with variable

Chloride concentration Increasing with variable

Acidity Increasing with variable

O2 concentration Increasing with variable

Fe2+

concentration No data

Fe3+

concentration No data

Cu2+

concentration No data

Material and methods

- Enargite concentrate from Kinross Gold`s LaCoipa mine in Chile; d80 = 21 m, Mineralogicalassay :

- Pure enargite specimen; Chemical composition:

Mineral Concentration, wt%

Enargite 39.8

Pyrite 46.5

Covellite 8.5

Chalcocite 5.2

Element Concentration pure, wt% Concentration bulk, wt%

Cu 44.96 33.35

As 13.83 10.13

Fe 5.06 11.78

Material and methodsShake flask tests

- Variables studied: T, chloride-, acid-, ferrous-, ferric-, copper concentrationand pulp density- 250 cm3 flasks, 100 cm3 solution- Orbital shaker at 300 min-1

- FAAS analysis for Cu, Fe and As- Titration and colorimetry for ferrous

Stirred reactor tests- Variables studied: agitation and direct gas sparging as well as the samevariables as in shake flask tests- 2 dm3 baffled glass vessel, 750 cm3 solution- Temperature control- FAAS analysis for Cu, Fe and As- Titration and colorimetry for ferrous

Effect of temperatureShake flask experiments

Effect of temperature on copper recovery when leaching enargite concentrate (-38 m +25 m) at 50 g/l pulp density, 1.5 g/l H2SO4 and 0 M NaCl

Effect of acid concentrationShake flask experiments

Effect of acid concentration on copper recovery when leaching enargite concentrate (-38 m +25 m)at 50 g/l pulp density and 0 M NaCl at 70°C

Effect of chloride concentrationShake flask experiments

Effect of chloride concentration on copper recovery when leaching enargite concentrate (-38 m +25 m)at 50 g/l pulp density and 1.5 g/l H2SO4 at 70°C

Effect of particle sizeShake flask experiments

Effect of particle size on copper recovery when leaching enargite concentrate at 50 g/l pulp density, 0 M NaCl at 70°C and 9.8 g/l H2SO4

Effect of Fe and Cu additionShake flask experiments

Effect of iron (5 g/l) and copper (5 g/l) addition on copper recovery when leaching enargite concentrate (d80=20 µm) at 10 g/l pulp density, 9.8 g/l H2SO4,

0 M NaCl and 80°C

SummaryShake flask experiments

- Particle size has the highest impact on enargitedissolution

- Iron addition, chloride conc. and temperaturealso increases the dissolution kinetics of enargite

- No significant difference between ferrous andferric on enargite leaching

- Higher acidity slightly improves enargitedissolution

Effect of oxygen injection rateStirred reactor experiments

Effect of oxygen injection rate on copper recovery when leaching enargite concentrate (d80=21 µm) at 1% pulp density, 60 g/l H2SO4, 8.5 g/l Fe2+, 1000

min-1 stirring rate and 85°C

339.8 l/h air

339.8 l/h O2

Effect of Fe concentrationStirred reactor experiments

Effect of Fe2+ and Fe3+ concentration on copper recovery when leaching enargite concentrate (d80=21 µm) at 1% pulp density, 60 g/l H2SO4, 1000 min-1 stirring rate and

85°C

Effect of pyrite additionStirred reactor experiments

Effect of pyrite addition (bulk: d80=145 µm and fine: d80=2 µm) on copper recovery when leaching enargite concentrate (d80=21 µm) at 1% pulp density, 60 g/l H2SO4, 8.5

g/l Fe2+, 1000 min-1 stirring rate and 85°C

Conclusions

• Leaching of enargite was extremely slow in alltests

• Dissolution rate increased with T, Cl-, acidityand smaller particle size

• Mechanism of dissolution is very complex

• Atmospheric leaching of enargite concentratesmay be too slow for commercial viability