Effective peroxymonosulfate activation by natural molybdenite for enhanced atrazine degradation: Role of sulfur vacancy, degradation pathways and mechanism

In this study, natural molybdenite (MoS2) was applied to activate peroxymonosulfate (PMS) for the removal of atrazine (ATZ) and its degradation mechanism was investigated. Molybdenite exhibits superior catalytic performance. The best condition for atrazine degradation efficiency (>99%) was obtained with molybdenite concentration of 0.4 g/L, PMS concentration of 0.1 mM, and ATZ concentration of 12 μM within 10 min under experimental conditions. Electron paramagnetic resonance (EPR) test and chemical probe test further proved that HO• and SO4•− played important roles in the molybdenite/PMS system, and SO4•− was dominant. Meanwhile, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) tests showed that sulfur vacancies and edge sulfur played important roles in the system. Edge sulfur was conducive to Mo4+ exposure, while sulfur vacancy facilitated electron transfer and reduced Mo6+ back to Mo4+. Combined with DFT calculation, the role of sulfur in the degradation process was verified. Besides, five ATZ degradation pathways were proposed. Finally, the degradation ability of the molybdenite/PMS system for different pollutants and in actual water bodies was also explored. This work provided ideas for exploring the degradation of organic contaminants by natural minerals.