Enhanced visible light driven photodegradation of rifampicin and Cr(VI) reduction activity of ultra-thin ZnO nanosheets/CuCo 2 S 4 QDs: A mechanistic insights, degradation pathway and toxicity assessment.

In this study, we focused on fabrication of porous ultra-thin ZnO nanosheet (PUNs)/CuCo2 S4 quantum dots (CCS QDs) for visible light driven photodegradation of rifampicin (RIF) and Cr(VI) reduction. The morphology, structural, optical and textural properties of fabricated photocatalyst were critically analyzed with different analytical and spectroscopic techniques. An exceptionally high RIF degradation (99.97%) and maximum hexavalent Cr(VI) reduction (96.17%) under visible light was achieved at 10 wt% CCS QDs loading on ZnO, which is 213% and 517% greater than ZnO PUNs. This enhancement attributed to the improved visible light, interfacial synergistic effect, and high surface-rich active site. Extremely high generation of ● OH attributed to the spin-orbit coupling in ZnOPUNs@CCS QDs and existence of oxygen vacancies. Besides, the ZnOPUNs@CCS QDs, forming Z-scheme heterojunctions, enhanced the photogenerated charge separation. We investigated the influencing factors such as pH, inorganic ions, catalyst dosage and drug dosage on the degradation process. More impressively, a stable performance of ZnOPUNs@CCS QDs achieved even after six consecutive degradation (85.9%) and Cr(VI) reduction (67.7%) cycles. Furthermore, the toxicity of intermediates produced during the photodegradation assessed using ECOSAR program. This work provides a new strategy for ZnO-based photocatalysis as a promising candidate for the treatment of various contaminants.