Synergistic degradation of sulfamethoxazole using peroxymonosulfate activated by Fe-Mn-Cu hollow spheres: Kinetics and mechanism studies

• Fe-Mn-Cu hollow sphere (FCMHS) catalyst was synthesized via the hard-template method. • The FCMHS/PMS catalytic system can achieve 99.10% removal of SMX without ions release. • Synergistic effect of Fe, Mn and Cu oxides accelerates charge transfer to enhance catalytic performance. • The cavity can enrich reactant concentrations and improve the accessibility of reactants and catalytic sites. • Degradation pathways of SMX were proposed based on LCMS-IT-TOF analysis and DFT calculations. The synergistic effect of bimetallic or trimetallic oxide catalysts plays a vital role in sulfate radical-based advanced oxidation processes (SR-AOPs). Herein, a composite catalyst of iron-manganese-copper hollow spheres (FCMHS) was synthesized by hard template method and used for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). The catalytic activity of FCMHS was comprehensively evaluated under different conditions (including catalyst loading, PMS dosage, pH etc.). A removal efficiency of 99.1% and a mineralization efficiency of 39.7% for SMX were achieved under the optimal conditions. The kinetic studies demonstrated that the reaction rate for SMX removal by using FCMHS was about 3.5 times faster than that for using copper-manganese hollow spheres (CMHS). The enhanced catalytic performance mainly stemmed from the confined high instantaneous concentration of SMX in the local void space and the synergistic effects of Mn 2+ /Mn 3+ /Mn 4+ , Cu + /Cu 2+ /Cu 3+ and Fe 2+ /Fe 3+ redox cycles to generate radicals and non-radicals. More importantly, the introduction of iron oxide into CMHS substantially facilitated charge transfer at the interface between FCMHS and reaction solution, leading to a high rate and good product selectivity. Furthermore, SMX degradation pathways were proposed by LCMS-IT-TOF assisted with density functional theory (DFT) calculations, and the mechanism was proposed comprehensively. This study opens a reliable and promising avenue for the efficient treatment of antibiotics-polluted water based on trimetallic oxide catalysts.