A cobalt solvent extraction investigation in africa s copper belt
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A Cobalt Solvent Extraction Investigation in Africa’s Copper Belt. Tanja Könighofer. Premium-Grade Co-Metal Specification. Premium Grade Co Metal = $34/lb (August 2008). CoEW Electrolyte Composition. A Co-Circuit Flowsheet. Testwork Objectives.

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Premium grade co metal specification l.jpg
Premium-Grade Co-Metal Specification Copper Belt

Premium Grade Co Metal = $34/lb (August 2008)


Coew electrolyte composition l.jpg
CoEW Copper Belt Electrolyte Composition



Testwork objectives l.jpg
Testwork Objectives Copper Belt

  • 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.


Slide6 l.jpg

Theory Copper Belt

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)


Order of metal extraction of cyanex 272 vs ph l.jpg
Order of Metal Extraction of Cyanex 272 vs pH Copper Belt

  • Fe3+>Zn2+>Al3+>Cu2+>Mn2+>Co2+>Mg2+>Ca2+>Ni2+.


Extraction isotherm with mccabe thiele plot l.jpg
Extraction Isotherm Copper Beltwith McCabe-Thiele Plot

1

2

3

4


Stripping isotherm versus mccabe thiele plot l.jpg
Stripping Isotherm Copper Beltversus McCabe-Thiele Plot

1

2

3


Cosx circuit l.jpg
CoSX Copper Belt Circuit


Co mg extraction efficiencies ph in final extraction stage l.jpg
Co & Mg Extraction efficiencies & pH in final extraction stage

100% Co Extraction

Co Slippage



Mg in the organic phase l.jpg
[Mg] in the organic phase stage

Strip

Scrub

Extraction


Mg scrubbing efficiency l.jpg
Mg scrubbing efficiency stage

  • < 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


  • Co in organic phase of e1 final scrub stage l.jpg
    [Co] in organic phase of E1 & final scrub stage stage

    1 Scrub stage

    3 Scrub stages


    Zn in s1 l.jpg
    [Zn] in S1 stage

    pH = 3.5


    Zn in s3 l.jpg
    [Zn] in S3 stage

    [H2SO4] = 8 to 9g/L


    Conclusions recommendations l.jpg
    Conclusions & Recommendations stage

    • 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 l.jpg
    Conclusions and Recommendations stage

    • 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 recommendations20 l.jpg
    Conclusions and Recommendations stage

    • 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


    Thank you l.jpg
    Thank you stage


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