Heterogeneous photocatalytic ozonation of sulfamethoxazole by Z-scheme Bi2WO6/TiO2 heterojunction: Performance, mechanism and degradation pathway

Abstract

• Bi 2 WO 6 /TiO 2 Z-scheme heterojunction was synthesized by a hydrothermal method. • The heterojunction had superior photocatalytic ozonation activity for SMX degradation. • The mineralization rate of SMX in the combined system reached 89.8% within 420 min. • A mechanism and possible pathway of SMX degradation were proposed. The objective of this study was to investigate the performance of Bi 2 WO 6 /TiO 2 (BT) heterojunction for photocatalytic ozonation degradation and the mineralization of sulfamethoxazole (SMX) under simulated sunlight. The authors investigated the effects of the Bi 2 WO 6 and TiO 2 ratio, as well as the catalyst dosage, ozone concentration, initial SMX concentration, pH value, and inorganic ions on the degradation efficiency of SMX in the BT photocatalytic ozonation process. The BT composites were characterized by methods such as XRD, SEM-EDS, TEM, XPS, FT-IR, UV–Vis DRS and BET. When the dosage of BT was 0.2 g/L, the ozone concentration was 1.5 mg/L, the SMX concentration was 10 mg/L, and the pH was 5.25, the removal rate of SMX could reach 97.1% after 180 min of reaction. Under the same conditions, the removal rate of TOC could reach 89.8% when the reaction time was 420 min. Test results after five cycles of experiments showed BT had excellent recyclability and stability. This paper presents a new Z-scheme transfer pathway of electrons and degradation mechanism based on the results of radical trapping experiments and electron spin resonance (ESR) measurements, as well as optical and photoelectrochemical analyses.