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

The limited regeneration of Fe²⁺ in the Fe-catalyzed advanced oxidation processes (AOPs) constrained its application for the removal of organic pollutants. Herein, MoSe₂ was introduced to promote the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in the Fe²⁺/PMS system. Compared with Fe²⁺/PMS processes, the 2,4-D degradation efficiency and PMS decomposition rate respectively increased by 73.8% and 84.2% in the MoSe₂/Fe²⁺/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 Fe³⁺. The rapid regeneration of Fe²⁺ boosted the activation of PMS and the degradation of pollutants. Additionally, the electron paramagnetic resonance (EPR) and quenching experiments results indicated that SO₄∙^-, ∙OH, and ¹O₂ accounted for 2,4-D degradation, and SO₄∙^- and ¹O₂ 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 MoSe₂ than that of WSe₂. In addition, the degradation efficiency of 2,4-D was up to 95.5% after five cycles of MoSe₂ in the co-catalytic system. The coexistent humic acid (HA) and Cl^- showed ignorant negative effect on the degradation, while HCO₃^- 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.