A ZnO/Bi₃TaO₇ S-scheme heterojunction for photoelectrocatalytic degradation of ciprofloxacin in synthetic and real wastewater

Towards the design of new photoelectrocatalytic materials for application in the removal of emerging persistent organic pollutants in water, a semiconductor heterojunction of ZnO/Bi₃TaO₇ was constructed by a hydrothermal method. The synthesis, characterization and application of the pristine and heterojunction photoelectrocatalyst are reported. The semiconductors and photoanodes were characterized to investigate their morphological, structural and photoelectrochemical properties using electron microscopy, UV/Vis diffusive reflectance, EIS, XRD, LSV, Mott Schottky and XPS techniques. The photoelectrocatalytic (PEC) performance of the pristine and heterojunction semiconductors was investigated in degrading ciprofloxacin in synthetic and real wastewater samples. The degradation experiments were carried out under optimal conditions of current density and pH, where the heterojunction showed improved degradation efficiency compared to the pristine ZnO and Bi₃TaO₇. TOC measurements were utilized to examine the degree of mineralisation in both synthetic and real wastewater samples. TOC removal of 75 % was obtained for synthetic water while 55 % removal was obtained for real wastewater. The UPLC-MS was utilized to examine the degradation pathway and the resulting products from the PEC degradation of ciprofloxacin. The heterojunction photoanode was stable and reusable up to eight cycles.