GB728135A - Improvements in or relating to the recovery of precious metal content in arsenic-bearing ores and concentrates thereof - Google Patents

Abstract

In a process for recovering the precious metal content of minerals from particulate arsenic bearing ores and concentrates, an aqueous slurry of the particles is formed with a sulphuric acid leaching liquor having an acid content below 10 per cent. by weight but greater than one having a pH of 4.5, the slurry is oxidized with air, oxygen-enriched air or oxygen at a temperature of 250 DEG F.-650 DEG F. under a pressure exceeding the vapour pressure of the solution at the temperature concerned, treatment being continued until the reaction substantially ceases, the slurry is pressure-relieved and cooled. Before or after cooling alkaline earth metal compound such as limestone or dolomite or its equivalent is added whereby the arsenic and the iron content of the feed in amount up to the chemical equivalent of the arsenic is precipitated, separated, washed and agitated in an alkaline cyanide slurry to dissolve the precious metals which are recovered in known manner. The alkaline earth compound or iron, e.g. in the form of sulphide, may be added to the original slurry or, to avoid unnecessary increase in the bulk of solids to be treated with cyanide, it may be added after the precious metal-containing solid residue from the oxidation reaction has been separated. Acid soluble metals remain in the solution and may be recovered after separation of the solid residue. Specifications 728,134 and 728,136 are referred to.