Enhanced activation of peroxymonosulfate by ball-milled MoS2 for degradation of tetracycline: Boosting molybdenum activity by sulfur vacancies

Though molybdenum disulfide (MoS2) has attracted widely attention in SO4 center dot- based advanced oxidation process recently, the effect of ball milling on its catalytic efficiency is less studied. In this work, the purchased MoS2 was ball milled and applied as peroxymonosulfate (PMS) activator for degradation of tetracycline (TC). MoS2 materials with different milling time or ball-to-MoS2 mass ratio all exhibited higher degradation efficiency (77.2%-83.6%) compared with pristine MoS2 (68.1%). It was supposed that ball milling could optimize the surface properties of MoS2, especially increased the surface area and the amount of S-vacancies, thus exposed more Mo (IV) sites, which were the main active sites to react with PMS. Besides, the enhanced adsorption capacity and the accelerated generation of reactive species both benefited the catalytic efficiency of ball-milled MoS2. EPR spectra and quenching experiments showed that ball-milled MoS2 could generate more reactive species (SO4 center dot-, (OH)-O-center dot, O-2(center dot-), and O-1(2)), which favored TC degradation. The above results implied that ball-milled MoS2 materials are promising in advanced oxidation processes.