Effective elimination of As(III) via simultaneous photocatalytic oxidation and adsorption by a bifunctional cake-like TiO2 derived from MIL-125(Ti)

A bifunctional cake-like TiO2 was successfully synthesized via calcination of MIL-125(Ti) at a suitable temperature by a one-step method and was applied for As(III) removal by simultaneous photocatalytic oxidation and adsorption. The as-synthesized samples were characterized by XRD, TGA/DSC, SEM, TEM, N2 adsorption–desorption isotherms, PL spectra, photocurrent, FTIR and XPS. The effects of calcination temperature on the specific surface areas of the samples, transformation of the TiO2 crystal phase and properties of As(III) removal were investigated. The results showed that higher calcination temperature resulting in a lower specific surface area and more transformations of the TiO2 crystal phase from anatase to rutile. The TiO2 calcined at 380 °C (MIL-125(Ti)-380 °C) exhibited excellent properties for As(III) removal, including photocatalytic oxidation of As(III) and simultaneous adsorption of the generated As(V). In addition, MIL-125(Ti)-380 °C could be reused at least four times without significant reduction in the photocatalytic oxidation and adsorption performances. The excellent photocatalytic oxidation and adsorption abilities of MIL-125(Ti)-380 °C can be attributed to the synergistic effects of strong photogenerated electron–hole separation and high specific surface area. The bifunctional cake-like TiO2 provides a wonderful strategy to remove As(III) completely from contaminated water using a single step.