Regulation of electron delocalization on porous carbon/manganese-iron oxide for enhancing nonradical processes of sulfamethoxazole: Oxidation pathway and mechanism

Abstract

Transition metal oxide defect engineering can regulate the electronic properties of materials, thereby realizing nonradical reactions during catalytic processes. In this study, porous carbon/manganese-iron oxide (PC@MFO) composites with different Mn/Fe ratios were prepared via in-situ encapsulation strategy. PC@MFO exhibited superior catalytic degradation and stable recycling performance during peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). After 10 min of reaction, >92 % of SMX was rapidly degraded, with high selectivity, through oxidative SMX removal from a complex aqueous solution. The kinetics of SMX degradation over different as-prepared samples were also investigated. A recycling study and regeneration treatment revealed no clear deactivation between the 1st and 6th cycles, suggesting that PC@MFO is a reusable heterogeneous catalyst for utilization in efficient oxidative SMX removal. Multiple characterization techniques and density functional theory calculations were used to study the mechanism of SMX degradation process. Nonradical oxidation was found to be the dominant reaction in the catalytic reaction, leading to SMX degradation. This was possibly due to the highly conjugated electron delocalization induced by Mn-Fe in the O-octahedra close to the oxygen vacancies, promoting rapid charge transfer and interfacial reaction kinetics. This study expands the understanding for the activation mechanism driven by Mn-Fe spinel oxides in deep-water treatment.