CoTiO₃ for highly efficient peroxymonosulfate activation: The critical role of Co–O–Ti bond for rapid redox cycles of Co²⁺/Co³⁺

Exploring efficient catalyst is critical for the application of persulfate-based advanced oxidation processes (AOPs) for environment remediation. Herein, perovskite CoTiO₃ was demonstrated an efficient catalyst for peroxymonosulfate (PMS) activation, which shows superior performance compared with single metal oxide system and homogenous systems: it removes 98.2% of hydroxychloroquine (HCQ, drugs for effective treatment of COVID-19) within 20 min at low dose of PMS (0.5 mmol/L), showing high tolerance to the environmental pH range (3.5–10.6) and significant versatility for various refractory organics. Combined with the material characterization and DFT calculations, it is found Co–O–Ti bond in CoTiO₃ serves as an electron mediator to facilitate the rapid redox cycles of Co²⁺/Co³⁺ during activation process, thus maintaining the high catalytic activity. Further mechanism exploration showed that fast regeneration of Co²⁺ ensures the production of high concentration of SO₄^•− and ^•OH, thus securing the rapid degradation of HCQ. Moreover, a designed CoTiO₃-CNT-PVDF membrane reactor can effectively remove refractory pollutant via practically feasible filter-through mode, which delivers a highest removal efficiency and longest operation duration compared with previous developed membrane-based AOPs. The corresponding mechanism revealed in this work can serve as guidelines for the design of advanced heterogenous catalysts and membrane reactors for AOPs.