Enhanced visible light driven photodegradation of rifampicin and Cr(VI) reduction activity of ultra-thin ZnO nanosheets/CuCo2S4QDs: A mechanistic insights, degradation pathway and toxicity assessment

Abstract

In this study, we focused on fabrication of porous ultra-thin ZnO nanosheet (PUNs)/CuCo2S4 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 loaded ZnO, which is 213% and 517% greater than bare ZnO PUNs. This enhancement attributed to the improved visible light absorption, interfacial synergistic effect, and high surface-rich active sites. Extremely high generation of ●OH attributed to the spin-orbit coupling in ZnO PUNs@CCS QDs and the existence of oxygen vacancies. Besides, the ZnOPUNs@CCS QDs, forming Z-scheme heterojunctions, enhanced the separation of photogenerated charge carriers. 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 ZnO PUNs@CCS QDs obtained even after six consecutive degradation (85.9%) and Cr(VI) reduction (67.7%) cycles. Furthermore, the toxicity of intermediates produced during the photodegradation process were assessed using ECOSAR program. This work provides a new strategy for ZnO-based photocatalysis as a promising candidate for the treatment of various contaminants present in water bodies.