Photocatalytic degradation of tetracycline antibiotics and elimination of N-nitrosodimethylamine formation potential by BiOCl/ZnInS heterostructure under visible-light irradiation.

Photocatalysis is an effective method for removing tetracycline antibiotics, which are important precursors to the potential carcinogen N-nitrosodimethylamine (NDMA). Herein, a BiOCl/ZnInS heterojunction was successfully synthesized using a simple hydrothermal method. This heterojunction was applied for the first time to degrade various tetracycline antibiotics and reduce NDMA formation potential (NDMA-FP) under visible-light irradiation. Characterization of surface morphology, crystal structure, chemical composition and photoelectrochemical properties revealed that the BiOCl/ZnInS heterojunction significantly improved light absorption, charge transport and carrier separation efficiency, thereby enhancing photocatalytic performance. The BiOCl/ZnInS catalyst achieved high degradation efficiencies of 88.0%, 90.7%, 88.7% and 91.7% for tetracycline, minocycline, chlortetracycline and doxycycline, respectively, within 60 min of visible-light irradiation. Additionally, it exhibited the lowest NDMA-FP values of 1.5%, 3%, 0.9% and 1.4%, respectively. Radical trapping studies and EPR experiments identified •O and •OH radicals as the primary reactive species involved in the photocatalytic process. Analysis of the degradation intermediates and structure-activity relationships indicated that the variations in NDMA-FP were closely associated with the number of dimethylamine groups in the antibiotics and the stability of the resulting carbocations. Notably, the BiOCl/ZnInS catalyst presented satisfactory stability and positive tetracycline degradation in real antibiotic wastewater. Incorporating BiOCl/ZnInS-loaded nonwoven fabric into a continuous-flow reactor efficiently degraded tetracycline in real wastewater under visible light. This work provides new insights on developing Z-scheme photocatalysts for the simultaneous degradation of various antibiotics and highlights their potential as commercially viable photocatalytic system.