Rapid removal of organic micropollutants by heterogeneous peroxymonosulfate catalysis over a wide pH range: Performance, mechanism and economic analysis

Abstract

Despite the previous success of MoS2/Fe2+/PMS process in detoxifying organic micropollutants, the drawback of requiring a narrow range of working pH limits its practical application. In this study, a class of commercial MoS2 nanoparticles was introduced as a co-catalyst to facilitate the PMS activation by Fe3+ ion. Results showed that the MoS2/Fe3+/PMS system over a wide range of pH values (3.0–9.0) achieved above 90% of removal efficiency for seven pollutants (chloramphenicol, tetracycline, ciprofloxacin, benzoic acid, rhodamine B, sulfadiazine, and bisphenol A) within 60 min of reaction time. The addition of MoS2 greatly accelerated the reduction of Fe3+ to Fe2+ and the decomposition of PMS, thereby resulting in increased mineralization efficiency of pollutants. The generation of Mo6+ ion and Mo6+ peroxo-complexes also contributed to the promoting effect. Both sulfate (SO4−) and hydroxyl (OH) radicals were identified in MoS2/Fe3+/PMS system but SO4− was the dominant reactive oxidant. Chloride ion (Cl−) showed an enhanced effect on degradation, while bicarbonate ion (HCO3−) showed an inhibitory effect. Economic analysis was conducted by using an electrical energy per order (EE/O) approach. The above research findings suggest that the MoS2/Fe3+/PMS system is a promising oxidation technology owing to its efficient removal of various pollutants over a wide pH range.