Visible light-responsive ZnO-based composite photocatalysts for the degradation of tetracycline in mariculture wastewater

The use of tetracyclines (TCs) in aquaculture has attracted significant attention due to its environmental impact. This study synthesized a visible light-responsive ZnO/CuO (ZC) composite photocatalyst via co-precipitation to degrade TCs in mariculture wastewater. The effects of CuO doping ratio, catalyst dosage, and TC concentration on TC degradation were systematically examined under visible light. Additionally, the reaction parameters for TC degradation were optimized using response surface modeling. The ZC 0.3 composite showed an exceptional TC removal efficiency of 90.89 % within 60 min for an initial TC concentration of 8.36 mg/L, which is 4.99 times higher than that of pristine ZnO. The enhanced photocatalytic activity of ZC is due to CuO doping, which adjusts the band structure that extends the absorption spectrum (2.78 eV) and improves visible light utilization (900 nm). Moreover, ZnO acts as an electron donor, significantly accelerating the separation of photogenerated electron-hole pairs. In the ZC catalytic system, holes, superoxide radicals (·O 2 − ), and hydroxyl radicals (·OH) are the primary reactive species. The strong oxidative potential of these species results in the mineralization of TC into less toxic or non-toxic small molecules. The loading of ZC powder catalysts onto polypropylene multifaceted spheres significantly enhanced the reuse efficiency of the catalysts. This research offers an effective strategy for managing TC pollution in mariculture and provides scientific guidance for using photocatalysts in saline environments.