Thiosystem leach processes for precious metal ores and concentrates: a review

The reserves of precious metals are limited, and the availability of high grade and easy to process ores is rapidly decreasing. It therefore becomes an absolute necessity to shift to alternative processing techniques that are cheaper and more environmentally friendly. Thiosystems leaching of precious metals is being proposed as a possible alternative to leaching with cyanide. The thio-techniques have advantages over traditional leaching, such as reduced hindrance from foreign cations and lower harmful effects on the environment. However, these techniques exhibit relatively high reagent utilisation in the extraction of precious metals, and this limits their industrial application. It is therefore imperative to understand the nature of decomposition reactions of these reagents under practical leaching conditions in order to reduce their consumption and encourage their use in industry. On that account, this paper reviews the thiosystem leach processes for precious metal ores and concentrates, drawing parallels with thiosystem gold leaching processes.