Process for recovery of metal values from materials containing arsenic and/or antimony

Abstract

A method for the recovery of metal values from a metal value-bearing material containing arsenic and/or antimony and a source of sulphate ions such as sulphide ore or concentrate is disclosed. In one form the method comprises the steps of: (a) providing a feed stream comprising a metal value-bearing material containing arsenic and/or antimony and a source of sulphate ions; (b) subjecting the feed stream to oxidative conditions under elevated temperature and pressure conditions in the presence of at least one component selected to decrease the effective concentration of free acid generated during the pressure oxidation step and promote the formation of pH-stable iron (III) sulphate products, thereby forming a slurry comprising a metal value-containing leach solution and a solid leach residue containing pH-stable iron (III) sulphate products and environmentally stable iron-arsenic and/or iron-antimony products; (c) separating the metal value-containing leach solution from the solid leach residue; (d) recovering the metal value (s) from the metal value-containing leach solution; and (e) recovering precious metal values, if present, in the solid leach residue by cyanide leaching.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a pressure oxidation process for the recovery of metal values, in particular copper and optionally gold and other precious metal values, from metal value-bearing materials containing arsenic and / or antimony.[0002]The present invention relates more particularly but not exclusively to a process of sequestering arsenic and / or antimony in a stable iron-arsenic and / or iron-antimony compound or compounds from a metal value-bearing material containing arsenic and / or antimony.[0003]The present invention also relates more particularly but not exclusively to a process by which the recovery of the metal values can be increased by enhancing the formation of a stable iron-arsenic and / or iron-antimony compound or compounds from a metal value-bearing material containing arsenic and / or antimony.[0004]The present invention also relates more particularly but not exclusively to a process by which recovery of metal values can be enhanced by i...

AI Technical Summary

Benefits of technology

[0064]In the case of copper sulphides containing arsenic and/or antimony, copper dissolution in the high temperature/high pressure leach step is optimized by addition of iron compounds to the reaction vessel, typically an autoclave, in sufficient quantities to favour precipitation of environmentally stable secondary iron-arsenate and/or iron-antimonate and/or iron-arsenate-sulphate and/or iron-antimonate-sulphate phases within the autoclave rather than the precipitation of copper-containing arsenate-antimonate residues, thereby limiting the copper content of the residue and maxi

Problems solved by technology

Pyrometallurgical treatment of metal-bearing sulphide materials that also contain arsenic is generally regarded as technically and economically undesirable, as most of the arsenic reports as flue dust and a speiss phase.

Safe disposal of these arsenic-containing materials involves considerable cost and technical disincentives.

The kinetics of the copper leaching stage of such a treatment are frequently slow and there is generally coprecipitation of an iron-copper-arsenate-sulphate compound or compounds, leading to copper losses to the leach stage solid residue and thus to the overall process.

The presence of meta-stable solid iron compounds such as basic ferric sulphate [Fe(OH)SO4] and any copper-containing precipitates such as an iron-copper-arsenate-sulphate in the residue decompose (break down) un