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

[Display omitted] •Novel Fe3C/Mo2C@CPANI composites were successfully prepared.•Fe3C/Mo2C@CPANI can activate PMS for fast 4-CP oxidation.•The synergies of metal carbide, C=O and N-doping boost PMS activation.•SO4•− and 1O2 were identified as the dominant reactive oxygen species. 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.