Peroxymonosulfate activation via CoP nanoparticles confined in nitrogen-doped porous carbon for enhanced degradation of sulfamethoxazole in wastewater with high salinity

Transition-metal phosphides (TMPs) have been considered a promising candidate for heterogeneous catalysis in wastewater treatment, while the feasibility of its application in peroxymonosulfate (PMS) based advanced oxidation processes systems for the treatment of high-salinity organic wastewater remains still unclear. In this study, catalysts of cobalt phosphide (CoP) nanoparticles confined in nitrogen-doped porous carbon (CoP/NC) were prepared using zeolitic imidazolate framework-67 (ZIF-67) as a template via calcination-oxidation-phosphorization, which were subsequently applied to activate peroxymonosulfate (PMS) for the degradation of sulfamethoxazole (SMX) in the water with high-salinity concentrations. Results showed that the degrading performance of CoP/NC could be improved and regulated by phosphorus (P) doping amount with an optimum of 5.0% (CoP/NC-5), which reached 100% of SMX degradation. Meanwhile, CoP/NC-5 catalyst could tolerate wide pH variations (5–9). More importantly, the CoP/NC-5/PMS system showed high adaptability to various concentrations of inorganic salt, even up to 500 mM. In addition, active species of sulfate radical (SO4•−) and singlet oxygen (1O2) were identified, which played dominant roles in the destruction of SMX, and the production amount of SO4•− was quantified. This work confirmed that transition-metal phosphides nanoparticles confined in nitrogen-doped porous carbon were a promising catalyst for SMX elimination in high saline wastewater.