Z-scheme CoS/BiOI heterostructure for visible light catalytic degradation of tetracycline hydrochloride: Degradation mechanism, toxicity evaluation, and potential applications.

The Z-type heterojunction CoS/BiOI material was prepared by the solvothermal method. The crystal structure and surface elemental valence state of the material were investigated by XRD, XPS, and other characterization methods. The microstructure of the material was investigated by SEM, BET, and other methods. In the experiment of degradation of 20 mg/L tetracycline hydrochloride using the prepared photocatalytic materials, the optimal photocatalytic performance of CoS/BiOI was explored with the introduction of 1.5 % CoS, and the degradation rate could reach 94.7 %. It was also found that 1.5 % CoS/BiOI had stable photocatalytic performance and good photocatalytic performance for all tetracycline antibiotics. Then the possible degradation pathways in the degradation process of TCH were explored using GC-MS, and the acute toxicity of the intermediates was evaluated by ECOSAR software. The UV-vis-DRS results showed that the overall photoelectrical properties of the composites were enhanced after introducing CoS with broad-spectrum absorption properties, and the PL and EIS results also proved the collation. The possible degradation mechanism of the CoS/BiOI system was also speculated by combining the free radical trapping experiments with the M-S curve results. The increasing severity of antibiotic pollution necessitates the development of highly efficient photocatalytic materials to enhance environmental remediation capabilities. Traditional photocatalysts suffer from high recombination rates of photogenerated carriers and low degradation efficiency. To enhance the photocatalytic activity and cycling stability of BiOI, we synthesized a CoS/BiOI heterojunction material via a solvothermal method. Using 20 mg/L TCH as a model pollutant, we investigated the photocatalytic efficiency of the prepared material. Through comprehensive experiments and structural analyses using XRD, XPS, and SEM, we explored the photocatalytic degradation performance and mechanism of tetracycline, confirming that CoS/BiOI is an ideal material for constructing a Z-type heterojunction, effectively reducing the recombination of photogenerated electron-hole pairs. Compared to pure BiOI, the CoS/BiOI composite exhibits superior performance in improving charge separation efficiency and enhancing visible light absorption. This study successfully constructs a Z-type heterojunction with efficient electron-hole separation, significantly enhancing photocatalytic efficiency. The composite material holds great potential for antibiotic pollution treatment, while the elucidation of its photocatalytic degradation mechanism provides theoretical guidance for designing novel photocatalysts.