Immobilization of black TiO2-x/SrFe2O4 heterojunction on diatomaceous earth as magnetic visible-light-driven photocatalyst for efficient ibuprofen mitigation

Abstract This study reports a facile preparation of black TiO2-x/SrFe2O4 (Ti3+ self-doped titania coupled with strontium ferrite), an efficient photocatalyst for ibuprofen (IBP) oxidation under visible light irradiation. Compared with TiO2-x or SrFe2O4, TiO2-x/SrFe2O4 heterojunction displayed better photo-oxidation performance, and their immobilization onto diatomaceous earth (DE) further increased the oxidation rate due to the adsorption ability of DE. The morphology, phase composition and other physicochemical properties of the composite were studied using various characterizations. The effects of several parameters on IBP oxidation efficiency were studied, such as pH, IBP concentration, catalyst dosage, co-existing ions, microplastics and introduction of oxidant peroxymonosulfate (PMS). About 97.4% of 10 mg/L IBP was removed within 150 min using 1.0 g/L composite at pH = 6. When PMS (0.6 mM) was added, IBP was completely removed within 120 min. Quenching experiment results demonstrated the roles of the following reactive species: hydroxyl radical, photo-induced hole, sulfate radical and superoxide radical. The intermediates during IBP oxidation were determined by HLPC-MS method, and their acute toxicity was studied. Furthermore, the plausible reaction pathway and mechanism were proposed. The reported photocatalyst revealed excellent reusability and stability after five repetitions, suggesting itself a promising approach for future wastewater treatment.