Insight into novel Fe₃C/Mo₂C@carbonized polyaniline activated PMS for parachlorophenol degradation: Key roles of Mo²⁺, C=O bonds and N-doping

Developing efficient heterogeneous catalysts are of great importance for utilizing peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) toward environment remediation. In this work, a novel composites Fe₃C/Mo₂C@CPANI are synthesized via hydrothermal and calcination with a precursor of metal salt and PANI. The derived Fe₃C and Mo₂C nanoparticles are wrapped into the nitrogen-doped carbon layer thanks to the rationally structure design, which can not only suppress metal ions leaching but also promote carbocatalysis by synergistic effect. The as-synthesized catalyst exhibited excellent performance in activating PMS with a fast 4-CP degradation rate (k = 0.79 min⁻¹). On the basis of surface chemistry analysis, the graphite N, C=O group, Fe²⁺ and Mo²⁺ are considered to be active sites that responsible for PMS activation. The electron paramagnetic resonance (EPR) and competitive quenching test both witnessed the existence of SO₄^•−, ^•OH, O₂^•− and ¹O₂ in the Fe₃C/Mo₂C@CPANI-0.1/PMS system, while SO₄^•− and ¹O₂ are considered as dominant reactive oxygen species (ROSs). Additionally, the influences of various reaction parameters on 4-CP removal were systematically investigated, where Fe₃C/Mo₂C@CPANI-0.1 could maintain its catalytic capacity under different conditions. This study proposes a facile method for fabricating metal carbide/carbon hybrids with rational structure and brings new insights into the radical/nonradical pathway in PMS activation process.