Thiosalts are sulphur oxides produced in the processing of sulphide ores. During the milling, grinding, and flotation of the ore or in the hydrometallurgical processing of the mineral to recover metals, partial oxidation occurs forming thiosalts. Thiosalts can pass through traditional effluent treatment systems relatively unaffected and oxidize to sulphuric acid in receiving ponds or other water bodies. Studies indicate that thiosalts themselves are not toxic but, rather, the pH depression in the water bodies is their negative impact on the environment. It is, therefore, important to determine the behaviour of thiosalts in the receiving water body accurately. The short-term objectives of this proposal are to determine thiosalt behaviour in an aqueous environment independent of other factors that may be present in the mining/metals processing treatment ponds and develop accurate methods to measure thiosalts. The long-term objective is the development of an overall thiosalt management plan where the location, wastewater composition, and available treatment options would be integrated into a risk assessment approach to decrease the overall impact of the mining/metals processing operations.
Although not currently regulated, thiosalts represent a significant challenge to both the mining and metals processing. The ability to predict behaviour in the ponds will have a significant impact on both costs and the environmental impact on discharge. This research will allow for better predictions of thiosalts and begin the incorporation of risk assessment into their management. This, as previously mentioned, will result in lower management costs, more directed treatment systems, and mitigate environmental impacts of pH depression.