Homogeneous catalytic activation of peroxymonosulfate and heterogeneous reductive regeneration of Co2+ by MoS2: The pivotal role of pH

The application of MoS2 to enhance Co(II)/peroxymonosulfate (Co(II)/PMS) system for organic pollutants degradation was developed, and the mechanism for pH dependent catalytic activity in the MoS2 co-catalyzed Co(II)/PMS processes was systematically investigated. It was found that MoS2 presented enhancement effect for Co(II)/PMS system in the tested pH range from 4.0 to 7.0, especially at pH 5.5 and 6.0. The pseudo first order reaction rates for Rhodamine B (RhB) degradation in MoS2-Co2+/PMS system at pH 5.5 and 6.0 were 3.2 and 1.8 times that in Co2+/PMS system (Co2+ 2 μmol L-1, PMS 0.2 mmol L-1, MoS2 0.5 g L-1). The redox recycle of Co3+/Co2+ was promoted by Mo(IV) and S(-II) on MoS2 surface and regenerated Co2+ induced homogeneous activation of PMS for the robust production of free radical with the major of hydroxyl radicals. Increasing MoS2 dosage, Co2+ and PMS concentration can linearly raise RhB degradation rate in MoS2-Co(II)/PMS system. Moreover, MoS2 exhibited excellent catalytic and chemical stability in recyclability and reuse for catalytic decontamination in MoS2-Co(II)/PMS system. This work gains new insight into the enhancement effect of MoS2 in the meal ions/PMS system, and provides a high performance wastewater treatment process of Co(II)/PMS at low concentrated Co2+.