Visible light-driven degradation of ofloxacin by graphene oxide-supported titania/zirconia ternary nanocomposites

Ternary nanocomposites based on titanium dioxide (TiO2) and zirconium dioxide (ZrO2) supported on reduced graphene oxide (rGO) are prepared via a facile hydrothermal method and exhibit a markedly enhanced photocatalytic activity towards the degradation of ofloxacin under visible light irradiation, as compared to the individual components. Among the series, the sample prepared at the Ti:Zr atomic ratio of 9:1 exhibits the highest degradation efficiency of 94.6% under the irradiation of a 300 W xenon lamp, with a mineralization rate over 40%, and the performance remains virtually unchanged after 5 consecutive cycles of testing. Structural characterizations show that the formation of type I heterojunctions at the TiO2/ZrO2 and rGO interfaces enhances the interfacial charge transfer, and two possible degradation pathways are identified by results from density functional theory calculations, in conjunction with liquid chromatography-mass spectrometry analysis of the degradation intermediates. The photocatalytic degradation of ofloxacin is predicted to be efficient and environmentally friendly based on the Toxicity Estimation Software Tool (TEST) and quantitative structure-activity relationship (QSAR) analysis. These results underline the significant potential of TiO2/ZrO2/rGO ternary composites in the effective removal of toxic pollutants and wastewater treatment.