Mesoporous TiO2/α-Fe2O3: Bifunctional Composites for Effective Elimination of Arsenite Contamination through Simultaneous Photocatalytic Oxidation and Adsorption

Abstract

Bifunctional mesoporous TiO2 (meso-TiO2)/α-Fe2O3 composites are successfully synthesized by impregnation of Fe3+ into meso-TiO2 followed by calcination at 300 °C. The composites are characterized by wide-angle X-ray powder diffraction, small-angle X-ray diffraction, and transmission electron microscopy. The “bifunctional” means that the composites possess synergy of the photocatalytic ability of meso-TiO2 for oxidation of As (III) to As (V) and the adsorption performance of α-Fe2O3 for As (V). Experimental results show that the meso-TiO2/α-Fe2O3 composites can oxidize higher toxic As (III) to lower toxic As (V) with high efficiency at various pH values in the photocatalysis reaction. At the same time, As (V) is effectively removed by adsorption onto the surface of composites. In addition, As (V) can be easily desorbed from the composites by heat treatment in alkali solution. After reusage for several times, the composites still present comparable catalysis and adsorption performance with that of first use, indicating the excellent stability of the bifunctional composites. The reasonable mechanism for the formation of meso-TiO2/α-Fe2O3 composites, the photocatalytic oxidation of As (III) to As (V) and simultaneous removal of As (V) are also presented in this paper. The bifunctional composites are expected to have significant applications in treating water contamination.