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

Abstract

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.