The effect of Fe(II) and Fe(III) on the efficiency of copper electrowinning from dilute acid Cu(II) sulphate solutions with the chemelec cell. Part II. The efficiency of copper electrowinning from dilute liquors

Abstract This programme of work forms part of a study into the application of the Chemelec cell for direct electrowinning of copper from dilute leach liquors. A typical liquor is defined as containing less than 2 g l −1 Cu(II), with an equivalent or greater concentration of iron as Fe(II) and Fe(III). Electrowinning experiments using simulated liquors showed that the current efficiency decreased in proportion to the increase in the Fe(III) concentration. A current efficiency of less than 30% was obtained during the electrowinning of a copper solution (1–2 g l −1 Cu) with an Fe(III) concentration of 0.5–3.0 g l −1 . Electrowinning from leach liquors (1–2 g l −1 Cu, 1–2 g l −1 Fe(III) and 1–5 g l −1 Fe(II)) showed improved efficiencies. A current efficiency of 47% was obtained for copper removal to less than 50 mg l −1 , with an electrolytic energy cost of about £198 per tonne at 3.3p per kWh. The impurity content of the copper was low, the most significant impurity being lead at 0.012%. This work has shown that the Chemelec cell can achieve reasonable efficiencies for direct electrowinning from dilute leach liquors. Further work is required in order to confirm the efficiency of electrowinning and to assess the operating and capital costs of a commercial cell.