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

The present invention provides methods for the recovery of metal values from metal value-bearing materials containing arsenic and / or antimony and a source of sulphate ions such as a sulphide ore or concentrate. The methods involve subjecting the material to oxidative conditions under elevated temperature and pressure conditions in the presence of certain iron-containing compounds and / or other chemical agents selected to decrease the effective free acid concentration during the pressure oxidation step and promote the formation of pH-stable iron(III) sulphate conditions. The slurry formed in the process can then be separated from the solid residue and the metal value-containing leach solution can be recovered. The methods can also involve the use of a continuous autoclave and the slurry can be maintained at a temperature for a period of time prior to separation. The technical effects of the invention include improved efficiency in the recovery of metal values and the ability to recycle precious metals from the solid residue.

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.

Images