Superior Activation of Persulfate to Degrade Acetaminophen by MgO incorporated CuO/TiO2: Pivotal Roles of non-redox MgO in the Regulation of Performance, Surface Properties and Nonradical Mechanism

Abstract Sulfate radical-based advanced oxidation processes (SR-AOPs) through the activation of persulfate (PS, S2O82−) have received increasing attentions due to their excellent ability to remove emerging pollutants. Herein, we provided a new approach to modulate the properties of copper-based catalysts through the incorporation of non-redox metal oxides MgO. The pivotal roles of MgO in regulating catalytic performance of various catalysts including CuOMgO/TiO2, CuOMgO/Kaolin, CuOMgO/SiO2, CuOMgO/MnO2, CuOMgO/Al2O3 and CuOMgO/ZnO were comprehensively studied. Among them, CuOMgO/TiO2-PS exhibited outstanding performance with reaction kinetic constant (kobs) of 0.046 min− 1, which was 15–100 times higher than that of control catalysts such as CuO-PS (0.00020 min− 1) and CuO/TiO2-PS (0.0070 min− 1). Additionally, Cu ions leaching from CuO/TiO2 (2.5 mg/L) was also obviously controlled in CuOMgO/TiO2 (0.34 mg/L) when being utilized for PS activation. Scavenging tests, EPR, electrochemical analysis and kinetic study on PS decomposition showed that electron transfer was the dominant oxidation pathway rather than classic free radicals or 1O2 in CuOMgO/TiO2/PS. Moreover, XRD, BET, EPR, XPS and FTIR disclosed that the incorporation of MgO significantly increased the intensity of surface hydroxyl groups with a larger surface area of CuOMgO/TiO2, which facilitated the outer-sphere coordination of Cu center and PS, therefore enhanced the generation of isolated surface-bound Cu2+ ions which played the dominant role for electron transfer process.