Sulfur vacancy mediated pyrite for scalable selective non-radical roxarsone degradation in wastewater without external chemical oxidants: Unveiling the fate of oxygen source and As

To realize potential efficient and scalable application of pyrite-based oxidation system for roxarsone (ROX) degradation in livestock wastewater, sulfur vacancies (SVs) was introduced in pyrite through a facile one-step mechanical ball-milling treatment. Comprehensive characterization demonstrated that the introduction of SVs reduced particle aggregation, enriched low-valence Fe and S species, and enhanced electron transfer capability. SVs preferred to be the adsorption sites and Fe as the electron donation sites during O 2 activation process. The specific contribution rate of different O 2 sources for ROX degradation was calculated via well-designed control experiments and the increased dissolved oxygen (DO) in water was proved to enhance the contribution of •OH, cooperating with 1 O 2 and beneficial for complete ROX mineralization. 97.13% of total arsenic derived from ROX can be effectively immobilized and surface coprecipitation played the major role. Speciation analysis revealed that ROX underwent initial oxidative degradation to inorganic arsenic, followed by rapid adsorption on the pyrite surface. FeS 2 -600 showed the high adaptability to complex environment and made effluent As of real livestock wastewater stably below the emission standard of China. This work further provides a universal strategy for potential scalable application of pyrite in water purification with zero-oxidant.