Effect of Thiosulfate Concentration and Leaching Temperature in Ammoniacal Thiosulfate Leaching of Refractory Sulfide Gold Ore

Thiosulfate as gold leach solution first studied in 1979 to found alternative of cyanide and mercury solution which are widely used in gold extraction industry although it’s negative impact for the environment. The ore sample is native ore from Bolaang Mongondow, North Sulawesi. According to Optical Microscope observation and LIBS characterization, there are pyrite compound which is one of the chacaracteristic of sulfide ore. According to X-ray fluorescence and Inductively Coupled Plasma, the ore contained about 14.62% Fe, 6.69% S, 0.15% Cu, and 0.27 ppm Au. This study aimed to determine the effect of thiosulfate concentration and leaching temperature in ammoniacal thiosulfate leaching of refractory gold sulfide ores on the solubility of gold. This research was conducted by laboratory scale of leaching method. The leaching result is then checked by Inductively Coupled Plasma (ICP). The concentration of thiosulfate (0.05M, 0.1M, and 0.2M) and the effect of temperature (250 C, 400 C, 600 C) were studied. Maximum gold extraction (62%) was obtained using 0.1M of thiosulfate concentrations at 400 C for 2 h with 20% of pulp density. Stirring speed and the pH of the aqueous solution were 400 rpm and 10, respectively. According to the results, it can be concluded that the concentration of Thiosulfate solution and leaching temperature will affect the dissolution of gold.