Molybdenum disulfide (MoS2): A versatile activator of both peroxymonosulfate and persulfate for the degradation of carbamazepine

Abstract

In this work, molybdenum disulfide (MoS2) was proposed as an emerging activator of both peroxymonosulfate (PMS) and persulfate (PS) for the degradation of carbamazepine (CBZ). More than 95% CBZ could be degraded in 40 min from initial pH 3 to 9 in both MoS2/PMS system and MoS2/PS system. Quenching experiments as well as EPR technique verified that freely diffusible sulfate radicals were generated in MoS2/PMS system while surface sulfate radicals and freely diffusible sulfate radicals were both generated in MoS2/PS system. Different Mo-based materials and different metal sulfides were compared to investigate the role of different Mo valence and the function of reductive S. The different sensitivities of Mo (Ⅴ) towards PMS and PS activation were observed. Besides, not all the metal sulfides in our study were capable of both PMS and PS activation. The unexpected activity of MoS2 for PS activation enlarged the source of sulfate radical generation. Based on XPS analysis, the possible mechanism was put forward. Co-existing chloride ions had a little inhibition while phosphate and carbonate ions both had a severe inhibition on CBZ degradation. Finally, intermediates of CBZ were identified by UPLC-QToF-MS/MS and possible degradation pathways were also proposed. This work is expected to provide a new strategy of sulfate radical generation and distinguish the different activation mechanisms in MoS2/PMS and MoS2/PS systems.