Fe2+-driven Mo(IV)/Mo(VI) redox-catalyzed PMS degradation of RhB

Abstract

Molybdenum disulfide (MoS2) can activate peroxymonosulfate (PMS) to degrade organic pollutants, but due to the continuous consumption of Mo(IV) during the reaction and the slow conversion of Mo(VI) to Mo(IV), the severe shortage of Mo(IV) regeneration will cause a large loss of catalyst, thus increasing the operation cost. In this study, different transition metal ions were introduced directly into the reaction system. The effects of conditions such as light, initial pH, transition metal ion concentration and PMS dose on the degradation effect of rhodamine B were investigated. The coupling mechanism was proposed based on the free radical scavenging reaction. The experimental results showed that the different transition metals activated PMS in the order of Co2+> Fe2+> Cu2+> Mn2+> Zn2+> Ni2+. In the Fe2+/MoS2/PMS/light system, the Fe2+ concentration ranging from 0.05 mM to 0.2 mM was proportional to the activation PMS efficiency. Free radical burst experiments suggested that ·OH and SO4−· were the main reactive radicals that effectively promoted the degradation of pollutants. Humic acid had an inhibitory effect on the removal of RhB from the MoS2/Fe2+/PMS/light system. Fe2+ completed its own redox cycle (Fe3+/Fe2+) while continuously catalyzing the conversion of Mo species (Mo(VI)/Mo(IV)) in 5 cycles.