Heterostructured MWCNTs@PANI@TiO2 Nanocomposites for Enhanced Adsorption of As(III) from Aqueous Solution: Adsorption and Photocatalytic Oxidation Behaviors

Arsenite contamination in groundwater seriously impairs human health due to its high mobility and toxicity. Herein, a novel heterostructured MWCNTs@PANI@TiO2 nanocomposite was synthesized via a one-pot polymerization process for the adsorption and photocatalytic oxidation of As(III) from aqueous solution. In the dark, the as-synthesized nanocomposite had a high adsorption capacity of As(III) at about 0.29 mmol·g–1 with an initial As(III) concentration of 0.067–0.801 mmol·L–1 at 298.15 K and exhibited a stable adsorption capacity in a wide pH range of 2–9. The adsorption kinetics of As(III) on MWCNTs@PANI@TiO2 was in accordance with the PSO model and was mainly controlled by chemical adsorption. Under visible light irradiation, the adsorption amount of As(III) on MWCNTs@PANI@TiO2 was substantially enhanced by about 57%, and the photocatalytic conversion of As(III) to As(V) was found to be caused by the photogenerated holes and superoxide free radical (•O2–). The hypothesized adsorption mechanisms of As(III) and As(V) ions on the nanocomposite were possibly ascribed to surface complexation and hydrogen-bonded interactions. The heterostructured MWCNTs@PANI@TiO2 nanocomposite offers a promising candidate for highly efficient removal of As(III) ions from arsenite-polluted groundwater.