Photocatalytic activation of persulfate by a TiO2/ZnFe2O4 Z-scheme heterojunction photocatalyst for the efficient degradation of tetracycline hydrochloride

Abstract

Antibiotic wastewater poses several environmental problems, and photocatalysis technology has become an ideal choice for the treatment of antibiotic wastewater by virtue of its high efficiency and clean and environmentally friendly nature. In this work, a TiO₂/ZnFe₂O₄ Z-scheme heterojunction was successfully prepared by a hydrothermal method, and tetracycline hydrochloride (TCH) wastewater was efficiently degraded in the presence of a persulfate (PDS). The effects of the catalyst dosage, amount of PDS, pH and interference from nine common cations and anions on the photocatalytic system were also investigated. In the photocatalytic synergic persulfate system, the TiO₂/ZnFe₂O₄ photocatalyst, under a simulated sunlight irradiation for 18 min, achieved a TCH removal rate as high as 97%, and although the effect of pH was very small, efficient TCH removal was achieved in the pH range of 4–10. Through the free radical trapping experiment, the photogenerated carrier migration path was inferred, and the degradation mechanism of the photocatalytic system was analyzed. It was observed that the free radicals (SO₄⁻˙, ˙OH and O₂⁻˙) and non-free radicals (h⁺ and ¹O₂) in the system collectively degraded TCH. In addition, the TiO₂/ZnFe₂O₄ photocatalyst exhibited excellent cyclic stability. This study provides guidance for the design and optimization of photocatalysis-persulfate advanced oxidation systems and further promotes the wide application of such systems in environmental remediation.