ZnFe2O4/BiVO4 Z-scheme heterojunction for efficient visible-light photocatalytic degradation of ciprofloxacin

A novel Z-scheme ZnFe2O4/BiVO4 heterojunction photocatalyst was successfully synthesized using a convenient solvothermal method and applied in the visible light photocatalytic degradation of ciprofloxacin, which is a typical antibiotic contaminant in wastewater. The heterostructure of as-synthesized catalysts was confirmed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy characterizations. Compared with the single-phase counterparts, ZnFe2O4/BiVO4 demonstrated considerably enhanced photogenerated charge separation efficiencies because of the Z-scheme transfer mechanism of electrons between the composite photocatalysts. Consequently, the 30% ZnFe2O4/BiVO4 catalyst afforded a degradation rate of up to 97% of 20 mg/L ciprofloxacin under 30 min of visible light irradiation with a total organic carbon removal rate of 50%, which is an excellent activity compared with ever reported BiVO4-based catalysts. In addition, the liquid chromatography-mass spectrometry and quantitative structure-activity relationships model analyses demonstrated that the toxicity of the intermediates was lower than that of the parent ciprofloxacin. Moreover, the as-synthesized ZnFe2O4/BiVO4 heterojunctions were quite stable and could be reused at least four times. This study thus provides a promising Z-scheme heterojunction photocatalyst for the efficient removal and detoxication of antibiotic pollutants from wastewater.

Automated summary

A novel Z-scheme ZnFe2O4/BiVO4 heterojunction photocatalyst was successfully synthesized and applied in the visible light photocatalytic degradation of ciprofloxacin. The as-synthesized catalysts demonstrated enhanced photogenerated charge separation efficiencies due to the Z-scheme transfer mechanism. The ZnFe2O4/BiVO4 catalyst showed excellent activity with high degradation rate and total organic carbon removal rate for ciprofloxacin, and the intermediates were found to be less toxic.