Insights into the Adsorption and Photocatalytic Oxidation Behaviors of Boron-Doped TiO2/g-C3N4 Nanocomposites toward As(III) in Aqueous Solution

The coupled adsorption-photocatalytic oxidation process provides a great potential scenario to enhance the removal efficiency of arsenite contaminants by converting As(III) to As(V) and simultaneous adsorption. In this study, the boron-doped black TiO2/g-C3N4 nanocomposite is synthesized by combination of sol-gel and in situ decomposition-thermal polymerization methods as a photocatalyst for the photocatalytic oxidation and adsorption of As(III). Under dark conditions, the boron-doped samples (B-TiO2 and B-TiO2/g-C3N4) display an increase in the As(III) adsorption capacity by one order of magnitude up to circa 3.2 mg g(-1) with an initial As(III) concentration of 2 mg L-1 at 298.15 K and pH 5. The adsorption kinetics of As(III) on B-TiO2/g-C3N4 conform to the pseudo-second-order kinetic model, revealing the chemical adsorption mechanism. Under visible light irradiation, the total arsenic removal capacity is substantially improved by 20% with a removal capacity of 3.9 mg g(-1). The enhancement of arsenic adsorption is attributed to the chemical complexation and hydrogen bond, in which B-OH bonds play a dominant role. The photocatalytic oxidation mechanism of the as-synthesized B-TiO2/g-C3N4 is attributed to the synergism of superoxide radicals, hydroxyl radicals, and photogenerated holes.

Automated summary

The coupled adsorption-photocatalytic oxidation process using boron-doped black TiO2/g-C3N4 nanocomposite as a photocatalyst enhances the removal efficiency of arsenite contaminants by converting As(III) to As(V) and simultaneous adsorption. The enhancement of arsenic adsorption is attributed to the chemical complexation and hydrogen bond, with B-OH bonds playing a dominant role. The photocatalytic oxidation mechanism of the as-synthesized B-TiO2/g-C3N4 is attributed to the synergism of superoxide radicals, hydroxyl radicals, and photogenerated holes.