The Generation of Thiosalts in Mills Processing Complex Sulphide Ores

Abstract

AbstractThe generation of thiosalts during the grinding and flotation of complex sulphide ores from New Brunswick has been examined. Bench scale grinding and agitation tests established that, in alkaline media, the sulphide minerals oxidize first to elemental sulphur, then to thiosulphate, polythionates and finally to sulphite and sulphate. Steel grinding media under neutral conditions inhibited the oxidation, and pH adjustments with lime produced lower amounts of thiosalts than did pH adjustments with soda ash.Sampling campaigns in a demonstration unit at CANMET and in flotation mills at Heath Steele and Brunswick Mining and Smelting (BMS) confirmed the above observations. The use of the SO2/aeration technique, combined with the use of soda ash during grinding, resulted in a high output of thiosalts throughout the primary beneficiation lines at BMS. Reverse flotation of pyrite with SO2 additions and heating to 85°C yielded extremely large amounts of thiosalts, up to an estimated 7.4kg of thiosalt sulphur...