Activation of persulfate-based advanced oxidation processes by 1T-MoS2 for the degradation of imidacloprid: Performance and mechanism

Abstract

Imidacloprid (IMI) which has been widely detected in the natural water environment is potentially genotoxic to humans and should be effectively eliminated. Persulfate-based advanced oxidation processes are considered to be reliable means aiming at organic pollutants degradation, while an efficient catalyst is urgently needed for the activation of the reaction. As a two-dimensional material, 1T-MoS2 is expected to be applied for the activation of persulfates due to its abundant active sites and good electrical conductivity. Therefore, in this study, 1T-MoS2 was synthesized by a simple and safe two-step solvothermal reaction and proposed as an emerging activator of peroxymonosulfate (PMS) for the degradation of IMI. It was found that 1T-MoS2 has significantly better catalytic performance on PMS than 2H-MoS2 and Bulk-MoS2, reaching. 76.4 % at pH = 3. The degradation rate of IMI reduced under alkaline conditions due to the inhibition of catalytic processes. Among the different coexisting anions, HCO3- had the greatest degree of interference and inhibition to the degradation process, resulting in the lowest IMI degradation rate for only 42.45 %. Quenching experiments and EPR analysis showed that SO4-∙ and OH were the main reactive oxygen species in the 1T-MoS2/PMS process. In addition, the IMI degradation pathways analyzed by UPLC-Q-TOF-MS/MS included dehydrogenation, electrophilic addition, heterocyclic ring breakage and intramolecular rearrangement. This study promotes the application of 1T-MoS2 and is expected to provide a novel persulfate-based advanced oxidation process catalyzed by 1T-MoS2 for IMI elimination in the aqueous environment.