CuCo2O4/ZnS S-scheme heterostructure for ultrasound−/photo-assisted degradation of pollutants and their biological toxicity assessment

Abstract

In this study, a series of CuCo₂O₄/ZnS composite photocatalysts with varying amounts of loading CuCo₂O₄ were synthesized via a simple solvent thermal evaporation method. The incorporation of CuCo₂O₄ significantly enhanced the light responsiveness of ZnS, suppressed exciton recombination, and accelerated charge transfer. Under the light irradiation for 2 h, the 20 wt% CuCo₂O₄/ZnS achieved a 72.4 % degradation efficiency for a 40 mg/L TC solution, which was 1.95 times higher than that of ZnS. And ZnS had no sonocatalytic activity, while in the presence of 50 μL H₂O₂, all CuCo₂O₄/ZnS composites show enhanced sonocatalytic activity, with the best activity of 20 wt% CuCo₂O₄/ZnS, and the sonocatalytic removal rate of 100 mL 40 mg/L of TC in 20 min is 65.1 %. Additionally, the degradation pathways and possible intermediates of TC during photocatalytic oxidation were analyzed using HPLC-MS. Ecotoxicological assessments via ECOSAR modeling revealed that intermediates P5, P11, and P13 exhibited lower chronic toxicity to fish, daphnia, and green algae compared to the original TC, with P13 showing the least toxicity. The S-scheme heterojunction was elucidated through active radical trapping experiments, Tauc plot analysis, and Mott-Schottky measurements. This study provides a comprehensive investigation into the ultrasonic/Fenton-like degradation of TC and the photocatalytic mechanism of CuCo₂O₄/ZnS, offering valuable insights into ZnS modification and its potential for sonocatalytic environmental remediation.