Processing of Metal Values from Concentrates

Abstract

The present invention relates to an improved method for the recovery of metal values, in particular copper and gold, from a metal value-bearing material containing arsenic and / or antimony and a source of sulphate ions, by means of a high temperature pressure oxidation process followed by cyanidation of the resultant high temperature pressure oxidation residue.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an improved process for the recovery of metal values, in particular copper and gold, from metal-bearing concentrates.[0002]The present invention also relates more particularly to an improved process for the recovery of metal values, in particular copper and gold, from metal-bearing concentrates by means of a high temperature pressure oxidation process followed by cyanidation of the resultant high temperature pressure oxidation residue.[0003]The present invention also relates. more particularly but not exclusively to a process of maximising copper and gold extraction from metal-bearing concentrates that also contain significant amounts of-arsenic and / or antimony, and that substantially simultaneously results in the formation of environmentally stable iron-arsenic and / or iron-antimony compounds in the process residues that can be discharged to tailings dams or the like such that strict environmental regulations are complied ...

AI Technical Summary

Benefits of technology

[0048]One particular aspect of the present invention is based upon the realisation that it is possible to adjust the processing conditions such that they prevent the formation of insoluble copper-containing precipitates during the high temperature pressure leaching process to extract metal values such as copper from a metal value-containing material such as a sulphide ore that also contains arsenic and / or antimony.

[0066]By means of limiting the copper content of the solid leach residue and efficient separation of the soluble copper from the solid leach residue, the economics of gold and / or silver recovery from the leach residue by cyanidation is enhanced as the extent of the reaction between copper and the cyanide leachant is significantly reduced, thereby lowering the overall cyanide consumption.

Problems solved by technology

Pyrometallurgical treatment of arsenic-containing metal sulphide minerals is generally regarded as technically and economically undesirable, as most of the arsenic reports as a flue dust and as a speiss phase.

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

The kinetics of the copper leaching stage of many such pressure oxidation processes are frequently slow and there is generally co-precipitation of an iron-capper-arsenate-sulphate compound or compounds, leading to copper losses to the leach stage solid residue and thus to the overall process.

Various means have been proposed to overcome the slow leach kinetics, including finer grinding of the feed material, although these sometimes result in substantially increased capital and operating costs.

Meta-stable 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 will decompose (break down) under the alkaline pH conditions required for gold / silver cyanidation and thus bring about an increase in the lime and cyanide consumption, thereby decreasing the economic efficiencies of the overall process.

In summary, many of the hydrometallurgical processes currently employed to treat arsenic- and / or antimony-containing copper sulphide materials suffer from unacceptable copper losses to the leach residue.

Moreover, if the feed material also contains precious metal values such as those of gold and / or silver, then current processing conditions also lead to the generation of solid residues that result in unacceptably high lime and cyanide consumption.

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