Oxygen vacancy enhances the catalytic activity of trimetallic oxide catalysts for efficient peroxymonosulfate activation

Although transition metal oxides are widely used as catalysts during sulfate radical-based advanced oxidation processes (SR-AOPs), their expensive cost and low efficiency hindered their large-scale applications. In this work, a novel cost-economical and efficient catalyst composed of cobalt oxides on the surface of electrolytic manganese residue with abundant oxygen defects (v-Co3O4@EMR) was synthesized and applied to activate persulfate for the degradation of organic contaminants. The catalytic performance of the v-Co3O4@EMR trimetallic oxide catalyst was better than that of the pristine Mn/Fe bimetallic oxides. v-Co3O4 played a dominant role in peroxymonosulfate (PMS) activation, while EMR could facilitate the redox cycle of Co redox pairs and acted as the magnetism supplier for catalyst recycling. The synergistic effects of Co, Mn and Fe promoted the production of SO4-, OH, O-2(-) and O-1(2). As a result, seven kinds of organic contaminants could be removed with high degradation efficiency. Introducing oxygen vacancies (O-V) into Co3O4 was crucial because of their contribution to enlarging Fe/Mn-O bonds in EMR, which could accelerate the electron transfer between Fe/Mn and O species. Radicals, especially SO4-, have controlled the catalytic reaction while the non-radical way played a supporting role. The low metal concentration and strong COD removal ability for actual wastewater indicated that the developed system in this work could be well used for practical applications.