Abstract
Sherritt’s Chimera process was developed to treat high impurity copper concentrates and nickel laterites together in a single pressure leach step. In this process, oxidation of the sulphide minerals in the copper concentrate provides heat and acid for the leaching reactions, while the limonite or transition laterite ore consumes acid and provides a source of iron to form highly stable leach residues. Copper is recovered as copper cathode from the common leach solution by solvent extraction and electrowinning while nickel and cobalt are recovered as mixed sulphide or hydroxide intermediates after purification of the copper raffinate.
In this study, batch tests were conducted on samples of arsenical copper sulphide concentrates, with varying concentrations of As, Sb and Bi, to determine the effects of these elements on sulphide oxidation and metals extraction from the concentrate and laterite ores. The rate and extent of nickel and cobalt extraction from the laterite was affected by the Fe:As and/or Fe:Sb mole ratio in the concentrate feed and the autoclave retention time. Bismuth did not interfere with the kinetics or extraction of copper, cobalt or nickel up to the maximum level tested. Extractions of over 96% copper and over 95% for nickel and cobalt were achieved from a range of laterite ores and from concentrates containing up to 5 wt% As, 8 wt% Sb and 5 wt% Bi.