A novel Z-Scheme CdS/Bi3O4Cl heterostructure for photocatalytic degradation of antibiotics: Mineralization activity, degradation pathways and mechanism insight

A novel Z-Scheme CdS/Bi3O4Cl heterostructure photocatalysts are fabricated by a facile surfactant-free method, and the visible-light-driven photocatalytic activity has been investigated for degradation of ciprofloxacin (CIP) and tetracycline (TC). For degradation of CIP, the Z-Scheme CdS/Bi3O4Cl-50 heterostructure displays the optimal rate constant (k(app) = 0.0151 min(-1)), which is about 10.63 and 1.97 times higher than that of pure Bi3O4Cl (k(app) = 0.00142 min(-1)) and CdS (k(app) = 0.00764 min(-1)), respectively. Meanwhile, as expected, the rate constant of Z-Scheme CdS/Bi3O4Cl-50 heterostructure also displays the highest (0.0643 min(-1)) for degradation of TC, which is 2.14 times and 4.34 times as high as those of the bare CdS (0.0301 min(-1)) and Bi3O4Cl (0.0148 min(-1)), respectively. The enhancement of phototcatalytic activity is ascribed to the significant improved transfer and separation of charge carriers, which are proved by photocurrent and electrochemical impedance spectra (EIS) measurements. The possible degradation pathway for CIP and TC are proposed based on the HPLC-MS analysis. Compared with pure CdS nanospheres and Bi3O4Cl nanosheets, the Z-Scheme CdS/Bi3O4Cl heterostructures exhibit the excellent mineralization ability towards the CIP and TC molecules degradation through the analysis of the total organic carbon (TOC) tests. Moreover, the photocatalytic mechanism over Z-Scheme CdS/Bi3O4Cl heterostructure under visible light irradiation is investigated by active species trapping experiments and ESR technology. The present work provides a new approach to construct Z-Scheme heterojunction photocatalysts and a deeper insight for the mineralization activity, possible degradation pathways and photocatalytic mechanism. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.