Mechanistic differences in ce-MoS2 catalytic activation of peroxides: Pathway divergence and reactive species roles

Two-dimensional MoS 2 -based advanced oxidation processes (AOPs) have recently shown significant promise in wastewater treatment. However, the activation of different oxidants leads to distinct degradation mechanisms and transformation pathways for organic pollutants. In this study, we explored the distinct mechanisms of chemical exfoliation (ce-MoS 2 ) in activating peroxymonosulfate (PMS), peroxydisulfate (PDS), and H 2 O 2 for the degradation of roxarsone (ROX). The removal efficiency of ROX is in the order of ce-MoS 2 /PMS > ce-MoS 2 /PDS > ce-MoS 2 /H 2 O 2 , with the highest total organic carbon (TOC) removal rate achieved by ce-MoS 2 /PDS. The ce-MoS 2 /PMS system primarily generates radicals (·OH, SO 4 ·- ) and oxidizes ROX to As(V), while PDS is weakly adsorbed onto the surface vacancies (SVs) to form surface complexes (PDS*), facilitating ROX removal through an electron transfer pathway rather than radical-mediated reactions. H 2 O 2 is strongly adsorbed to SVs, directing the ce-MoS 2 /H 2 O 2 system to predominantly convert H 2 O 2 into H 2 O via a two-electron (2e - ) reduction pathway. The distinct activation pathways and types of reactive species led to differences in ROX removal efficiency, product transformation, and toxicity. This study clarifies the role of ce-MoS 2 in peroxide activation and offers guidance for the strategic design of MoS 2 -based composites tailored to specific oxidants, aiming to improve wastewater treatment efficiency.