Characterization of the Liberator Cell Sludges from Three Copper Electrorefineries

Abstract

The amounts of As, Sb and Bi precipitated in the liberator cells of copper electrorefineries increase as the copper concentration is reduced by electrowinning and precipitation is significant for Cu concentrations <1 g/L. Liberator cell sludges usually contain PbSO4 which incorporates small amounts of As, Sb and Bi from the electrolyte. The Pb originates from the Pb anodes used in the liberator cells and because of its low solubility, PbSO4 precipitates for the entire range of Cu concentrations encountered during decopperizing, from >40 g/L Cu to <1 g/L Cu. No Cu arsenide (Cu3As or Cu5As2) precipitates during decopperizing to 5 g/L Cu, even from electrolytes containing up to 25 g/L As. However, Cu arsenide forms when the electrolytes are decopperized to <1 g/L Cu. Significant amounts of Sb and Bi are incorporated in the Cu arsenide phase. The As, Sb and Bi also precipitate as a (Sb,Bi,As)3O6(OH) phase in the liberator cell sludge. Trace amounts of metallic Bi, a Cu-As-Bi phase, a Cu-Bi-As-Sb-O phase (?) and Sn arsenate are also detected in the liberator cell sludges.