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

[0045]According to another aspect of the invention there is provided a pressure oxidation process for recovering one or more metal values from a metal value-bearing material containing arsenic and / or antimony, the process comprising the step of providing to the process at least one component selected to promote the formation of solids that are sufficiently stable under pressure oxidation conditions such that the recovery of the one or more metal values is enhanced.

[0065]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 precious metals recovery from the leach residue by cyanidation is enhanced as the extent of the reaction between copper and the cyanide leachant is significantly reduced, thus lowering the overall cyanide consumption.

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) under the alkaline pH conditions required for gold / silver cyanidation leaching and as a result increase lime and cyanide consumption, decreasing the economic efficiencies of the overall process.

The breakdown of the abovementioned solid components under alkaline conditions may also release copper and other metals in a form which is reactive with the cyanide ion, thereby increasing cyanide consumption.

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 materials also contain precious metals, then current processing conditions also lead to the generation of solid residues that result in unacceptably high lime and cyanide consumption.