Metals recovery from multimetal sulphide concentrates (CuFeS 2–PbS–ZnS): combination of thermal process and pressure leaching

Abstract

A laboratory-scale method for treating a bulk concentrate (CuFeS 2–PbS–ZnS) for metals recovery was developed utilising a combination of thermal process (roasting) and pressure leaching as an alternative to conventional pyrometallurgical processing. Pyrometallurgy is becoming less acceptable from environmental standpoints for the treatment of bulk concentrates. Additionally, high capital costs make modern facilities cost prohibitive. The leaching agents employed, namely, sulphuric acid (lixivant) and ferric sulphate, are selective for metal sulphides, this coupled with the fact that they create fewer environmental problems and are economical makes this new process highly favourable. In the laboratory evaluation of this process, the metal values in the flotation concentrates were selectively recovered by combining roasting and pressure leaching. The experimental parameters studied included roasting temperature, and pressure leaching pulp density, temperature, and retention time. Laboratory results indicate that roasting followed by pressure leaching is an efficient and cost effective method of treating base metal sulphide concentrates.