Improved sulfamethoxazole degradation by the addition of MoS2 into the Fe2+/peroxymonosulfate process

Abstract

The low efficiency of transforming ferric ion (Fe3+) to ferrous ion (Fe2+) always challenges the activation of peroxymonosulfate (PMS) by (Fe2+) processes in the degradation of micro-organic contaminants. In this study, molybdenum disulfide (MoS2) which accelerated PMS activation and the Fe2+/Fe3+ cycle through the reaction of Mo4+ and Fe3+ was employed to significantly improve the efficiency of Fe2+/PMS on sulfamethoxazole (SMX) degradation. Through the analysis of electron paramagnetic resonance (EPR) and quenching experiments, both sulfate and hydroxyl radicals have been proven to account for SMX degradation in the MoS2/Fe2+/PMS process. The optimal pH of 3 has been determined for SMX degradation in the process, and an equation to express the relationship between the rate of SMX degradation and the dosages of Fe2+, MoS2 and PMS was simulated. Chloride ion and humic acid had positive and negative effects on the process, respectively, whereas nitrate and bicarbonate had no influences on SMX degradation. Through the identified intermediates by LC/MS, a transformation pathway of SMX in the MoS2/Fe2+/PMS process was proposed. Additionally, the good efficiency of SMX degradation (>80%) in real water matrices and good stability of MoS2 after reuse for 6 times further suggest that the MoS2/Fe2+/PMS process can be effectively used to degrade SMX.