New insights into pyrite-mediated residual xanthate degradation and carbon disulfide emission from mineral processing wastewater: mechanism and pathways.

Xanthates are the predominate regents used in the mineral processing industry of sulfide ores and are also recognized as organic contaminants in mining areas. It has been demonstrated that pyrite can accelerate the residual xanthate degradation in mineral processing wastewater. However, the degradation mechanisms and pathways remain unclear. This work comprehensively investigated the influence of pyrite on xanthate degradation using potassium ethyl xanthate (PEX) as a representative xanthate collector, and elucidated the degradation mechanisms and pathways by integrating solution composition analysis with mineral surface characterization. The results indicated that the degradation rate of PEX increased by 33.7-fold in the presence of 1.0 g/L pyrite, while the yield of hazardous by-product carbon disulfide decreased by 96.2% due to the spontaneously generated •OH, which oxidized the xanthate adsorbed on the pyrite surface. In addition, elemental sulfur was identified as the dominant sulfur-containing degradation product. These findings suggest that residual pyrite plays an important role in reducing CS2 emissions in mining environments. This results of this work provide new insights into the transformation of xanthates during their long-term coexistence with pyrite in tailings ponds and the life cycle of thiol collectors in the mineral processing circuit.