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A Co-Circuit Flowsheet
Copper Circuit
Fe/Al Removal
Co Upgrade
Cu Ion
Exchange
Impurity Solvent
Extraction
Zn Ion
Exchange
Co Solvent
Extraction
Co ElectrowinningImpurities to
TailingTreatment
Impurity Bleed
Cu Recovery
Ore
Tails
Cu Metal
Bleed stream
Precipitate to Tails
Co Metal
Testwork Objectives
• Produce a raffinate stream containing <10mg/L cobalt
in order to minimise cobalt losses.
• Limit the amount of magnesium, reporting to the cobalt
electrowinning circuit to less than 5% of that contained
in the feed to the cobalt solvent-extraction circuit.
• Test pre-neutralisation with 10M NaOH.
• Determine the zinc build-up within the cobalt solvent
extraction strip circuit.
Theory
2AH+ + M2+ A2Mn2+ + 2H+
A represents R2P(O)O-
Overbar represents a species in the organic phase..R2P(O)OH(org)+NaOH(aq) R2P(O)ONa(org)+H2O(aq)
CoSX Circuit
E3 E2 E1 Sc1 Sc2 Sc3E4E5 S1 S2 S3
Strip Liquor
Loaded Strip
Liquor
Scrub Liquor
Aqueous Feed
Raffinate
Stripped Organic
Aqueous Organic
Mg scrubbing efficiency
• < 5% Mg reporting to strip circuit achievable in 3 stages• < 5% Mg reporting to strip circuit achievable in 1 stage, if
Mg loading in extraction is limited
Conclusions & Recommendations
• Extraction
– 18% (v/v) Cyanex 272 in aliphatic diluent
– 4 Stages using 40g/L NaOH for pH control
– 1 pre-neutralisation stage using 10M NaOH
– Increase pH profile in extraction using pre-neutralisation
– [Co] < 10mg/L in Raffinate
– 99% Co extraction efficiency
– pH profile of 4.9 in E1 and 5.7 in E4
– Phase ratio = 1.0
– Mg scrubbing enhanced by decreased pH profile from E4 to E1
Conclusions and Recommendations
• Scrubbing
– Scrub liquor = advance electrolyte (55g/L Co)
– O:A = 40
– < 5% Mg from feed reports to loaded strip liquor using 3 stages
– < 5% Mg from feed reports to loaded strip liquor using 1 stage if co-
extraction limited in extraction
– 68% and 39% scrubbing achieved in 3 and 1 stages respectively
– Recommend 2 stages be employed and optimised on full-scale plat
Conclusions and Recommendations
• Stripping
– Strip liquor = spent electrolyte (55g/L Co, 8-9g/L H2SO4)
– O:A = 0.67
– 100% Co stripping achieved in 3 stages when pH in S1 between
3.5 and 4.0
– pH control in S1 by addition of 30g/L H2SO4
– Zn accumulation, possible contamination of Co metal
– Slip in pH
– Recommend controlled periodic stripping of organic at low pH –
strip liquor recycled to upstream unit operations