Conditioning of POX slurry and its effect on pressure oxidation performance of refractory gold sulphide ore

Abstract

This paper describes the results of a laboratory study that looked at the conditioning of POX slurries produced by pressure oxidation (225 oC) of refractory gold flotation concentrates. The authors used a case study of sulphide concentrates produced as a result of flotation of refractory gold ores of the Malomyr and Pioner deposits to define the conditioning parameters applicable to POX slurries: i.e. temperature — 95 oC, duration — 2 to 4 hours. The above conditions help improve the quality of POX cakes before cyanidation so that the POX residue contained less sulphate sulphur and the cake weight could be lowered by 40–70%. The authors looked at the relationship between the conditioning parameters (60–95 oC with the duration of up to 7 hours) and the solids yield. They also examined how the above parameters influenced the transfer of the key components (i.e. iron, sulphur and arsenic) into liquid phase. In particular, the authors examined the process of conditioning POX cakes obtained from concentrates with the minimum (up to 2%) and high (8–10%) concentration of arsenic. The paper examines how the material composition of POX products tends to change after conditioning when dealing with sulphide concentrates. Conditioning was found to benefit the recovery of gold from POX cakes when dealing with high-arsenic concentrates. The gold particles in cakes can be encapsulated by mixed arsenate/sulphates of iron(III), which get dissolved during atmospheric conditioning, and the gold surface becomes available for cyanide solution. After conditioning, the share of cyanidable gold in POX cakes increases by 3.0 to 5.5%.