Bimetallic cobalt-cerium oxides activated fenton-like process for organic contaminant removal: Role of high-valent cobalt species modulated by oxygen vacancies

Cobalt-cerium bimetallic oxides (CoCeOx) with rich oxygen vacancies (OVs) were prepared by solvothermal method for peroxymonosulfate (PMS) activation efficiently, and the effect of OVs on reactive species formation was discussed. Carbamazepine (CBZ), a widely used anti-epileptic drug, also a typical pharmaceutical and personal care products (PPCPs) in the water environment, could be removed by 98 % in 40 min with low addition of CoCeOx and PMS in the CoCeOx/PMS system. Through a series of quenching experiments and electron paramagnetic resonance, it was confirmed that the main reactive species for decontamination were high-valent cobalt oxygen species (Co(IV)). Through the OVs detection and the contribution calculation of radicals and non-radicals on CBZ removal, it was found that OVs promoted the transformation from radicals to non-radicals (mainly Co(IV)) in the systems. In addition, cerium doping played an important role in promoting Co (II) / Co (III) cycle and OVs regeneration. Density functional theory (DFT) calculation revealed the formation process of Co(IV), and further proved that OVs could promote the formation of Co(IV). Evaluated by quantitative structure–activity relationship (QSAR) analysis, the ecotoxicity of CBZ and its main intermediates was significantly decreased. Overall, this study deepens the understanding of OVs promoting the formation of high-valent metal oxygen species (HVMO), as well as provides feasibility for the removal of refractory organics in wastewater.