Enhancement of peroxymonosulfate activation for 2,4-dichlorophenoxyacetic acid removal by MoSe2 induced Fe redox cycles

The limited regeneration of Fe 2+ in the Fe-catalyzed advanced oxidation processes (AOPs) constrained its application for the removal of organic pollutants. Herein, MoSe 2 was introduced to promote the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in the Fe 2+ /PMS system. Compared with Fe 2+ /PMS processes, the 2,4-D degradation efficiency and PMS decomposition rate respectively increased by 73.8% and 84.2% in the MoSe 2 /Fe 2+ /PMS system. DFT simulation results suggested that Se atoms acted smoothly as the bridge supporting the charge transfer from Mo to adjacent Fe atoms, which led to the reduction of Fe 3+ . The rapid regeneration of Fe 2+ boosted the activation of PMS and the degradation of pollutants. Additionally, the electron paramagnetic resonance (EPR) and quenching experiments results indicated that SO 4 ∙ − , ∙OH, and 1 O 2 accounted for 2,4-D degradation, and SO 4 ∙ − and 1 O 2 predominated the reaction. The Mo based co-catalysts showed better co-catalytic effect than the W counterparts, and the moderate adsorption for PMS and lower electron transfer electron transfer resistance accounted for the more excellent co-catalytic performance of MoSe 2 than that of WSe 2 . In addition, the degradation efficiency of 2,4-D was up to 95.5% after five cycles of MoSe 2 in the co-catalytic system. The coexistent humic acid (HA) and Cl − showed ignorant negative effect on the degradation, while HCO 3 − would depress the oxidation reaction. The acidic etching wastewater can be applied as the Fe ions source in this co-catalytic process to remove 2,4-D effectively.