Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure-Activity Relationship

The quantity of mineral processingwastewater (MPW) islarge andcontains residual thiol collectors, which easily cause environmentalpollution. Herein, we systematically investigated the catalytic performancesand underlying mechanisms of iron sulfide minerals (pyrite, marcasite,and pyrrhotite) for the activation of peroxymonosulfate (PMS) to treatMPW containing various thiol collectors (ethyl xanthate (EX), butylxanthate (BX), diethyldithiocarbamate (DDTC)). Density functionaltheory (DFT) calculation results indicated that electron-rich Fe atomsin pyrite and marcasite acted as electron donors for PMS adsorptionand cleavage, while pyrrhotite with electron-deficient Fe atoms hasno PMS adsorption site. In particular, pyrite has stronger reactivityin comparison with marcasite due to more electron transfer and thelower thermodynamic and kinetic energy barrier of the reaction. Meanwhile,the efficient electron transfer of pyrite with strong F-S covalentbonds facilitated the regeneration of Fe(II), thus improving the catalyticperformance. As a result, pyrite exhibited the highest total organiccarbon (TOC) removal efficiency for real MPW, which was 1.12-foldand 1.63-fold of that on marcasite and pyrrhotite, respectively. Thisstudy highlights the structure-activity relationship of ironsulfide minerals and provides new insights into the PMS activationmechanism of sulfur-containing catalysts for MPW treatment. The relationship between the structureand catalytic performanceof iron sulfide minerals was clarified, and the degradation mechanismof thiol collectors was revealed.