Enhancing sulphide-based arsenic precipitation for treatment of metallurgical waste streams to reduce environmental impact

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Due to the depletion of high grade ores, production of metals necessitates processing of lower grade ores with increasing levels of arsenic. Processing this type of raw materials introduces arsenic into the metallurgical circuits, resulting in the generation of waste streams that contain arsenic, which is toxic and carcinogenic. In partnership with BQE Water, a water treatment service provider with expertise in mine impacted water and process solution treatment and management, we propose to enhance a sulphide-based precipitation process that removes and stabilizes arsenic as arsenic trisulphide with high arsenic content. Compared with the existing removal methods, this sulphidization process will generate the least volume of arsenical waste by-product due to the high arsenic content, which could reach as high as 60%, a substantial increase from the 5-30% content that results from current methods. However, the stability of arsenic trisulphide is a major concern due to its solubility and susceptibility to atmospheric and bacterial oxidation. Therefore, the key technical challenge the proposed project will address is to assess and devise a strategy to enhance the stability of the arsenic trisulphide under a variety of conditions, specifically those relevant for safe storage in the field. The enhanced sulphidization process aligns well with the strategic technology development at BQE Water. The new knowledge generated will strengthen the existing expertise and facilitate its business in the area of arsenic management. While sulphidization has been used in the past for arsenic removal, enhancing the process and the stability of the final by-product of treatment will enable mining companies to process arsenic-bearing ores for extraction of valuable metals in an environmentally safer manner. Given the importance of the minerals sector to the Canadian economy, the implementation of the proposed process will bring enormous economic, social and environmental benefits to Canada. The proposed project will train 1 postdoctoral fellow and 2 undergraduate research assistants.