Oxygen vacancy-rich La2NiO4 firmly loaded ZIF-67-derived CoC for ofloxacin degradation via enhanced electron transfer and peroxymonosulfate activation

Advanced oxidation processes (AOPs) are constrained by the performance of catalysts. Introducing oxygen vacancies (OVs) and enhancing catalyst conductivity represent viable strategies. Herein, oxygen vacancy-rich A2BO4-type perovskite La2NiO4 was synthesized and loaded onto highly conductive ZIF-67-derived CoC for the activation of peroxymonosulfate (PMS) and the removal of ofloxacin (OFX). La2NiO4/CoC exhibited exceptional performance, achieving a removal efficiency of 93.4 % within 5 min. The degradation rate constant of La2NiO4/ CoC were 18 times and 2.3 times higher than those of LaNiO3 and ZIF-67-derived CoC, respectively, which was attributed to the enhancement of OVs and conductivity. Moreover, La2NiO4/CoC displayed excellent reusability with effective inhibition of ion leaching. In La2NiO4/CoC/PMS system, both radical and non-radical oxidation mechanisms cooperatively participated in the reaction with non-radical pathways predominating. Non-radical mechanism including singlet oxygen (1O2) and mediated electron transfer were also identified in addition to hydroxyl radical (& sdot;OH) and sulfate radical (SO4 & sdot;). The generation routes and mechanisms of reactive oxygen species (ROS) involved were elucidated, and the degradation intermediates and toxicity of OFX were evaluated. This work provides a novel strategy for designing efficient composite catalysts as PMS activator for wastewater treatment.