Oxygen vacancy concentration modulation of perovskite-based heterogeneous catalysts for Fenton-like oxidation of tetracycline

Oxygen vacancies (V_O) constructing in metallic compounds have been verified to enhance hydrogen peroxide (H₂O₂) activation for pollutants treatment. However, the interactions between surface V_O concentration and H₂O₂ were still ambiguous. In this study, perovskites with different surface V_O concentration were successfully prepared by a simple sol-gel process. Experimental results showed that A-site cation deficient was capable of distorting FeO₆ octahedra in Ca_1−xFeO_3-δ (x = 0, 0.1, 0.2) orthorhombic perovskites for the regulation of surface V_O concentration. Afterwards, Ca_0.9FeO_3-δ exhibited excellent catalytic activity and stability for tetracycline (TC) degradation, which was 4 times higher of catalytic enhancement than that of the raw Ca_1.0FeO_3-δ. Moreover, up to 9, 17 and 27 times of catalytic enhancement as compared with commercial Fe₃O₄, ɑ-FeOOH and Fe₂O₃ towards TC degradation. Based on electron spin resonance and free radical quenching experiments, the hydroxyl radical (∙OH) was the main active species for the catalytic degradation of TC. Meanwhile, higher or lower surface V_O concentration was harmful to the production of ∙OH. Additionally, the toxicity of TC degradation by-products exhibited a decreasing trend according to the results of toxicological simulation. This work provides a new strategy for designing an efficient and promising heterogeneous Fenton-likes catalyst for environmental remediation.