Preparation and photocatalytic properties of magnetically separatable ZnFe₂O₄-TiO₂/reduced graphene oxide composites

ZnFe₂O₄-TiO₂/reduced graphene oxide(rGO) composites were synthesized from TiO₂(P25), Fe(NO₃)₃·9H₂O, Zn(NO₃)₂·6H₂O and graphene oxide (GO) by one-step solvent thermal method. The properties and structures of ZnFe₂O₄-TiO₂/rGO composites were characterized by UV-Vis, Raman spectra, XRD, SEM and EDS. The photocatalytic degradation performance of ZnFe₂O₄-TiO₂/rGO composites prepared with different amount of GO were investigated. GO is reduced to rGO in the solvent thermal reaction process. The addition of ZnFe₂O₄ and rGO broadens the visible light wavelengths absorbed by ZnFe₂O₄-TiO₂/rGO composites. ZnFe₂O₄-TiO₂/rGO composites have magnetic performance, which is convenient for separation and recycling. ZnFe₂O₄-TiO₂/rGO composites show the best photocatalytic degradation of methylene blue(MB) when the mass fraction of GO is 5wt%, and the degradation rate reaches 99.1% after 60 min under simulated solar irradiation. According to the scavenger experiments, the possible MB degradation mechanism is mainly contributed to the generation of active species induced by·OH and·O^2-. The photo-generated electrons(e⁺) in conduction band(CB) of TiO₂ migrate to valence band(VB) of ZnFe₂O₄, and form a Z-scheme photocatalytic system. The photocatalyst stability test shows that ZnFe₂O₄-TiO₂/rGO composites have excellent stability and can be used as a photocatalyst for the degradation of organic dyes under sunlight.