Polyaniline-TiO₂ composite photocatalysts for light-driven hexavalent chromium ions reduction

In order to develop efficient photocatalysts, great efforts have been made to reduce hexavalent chromium to trivalent chromium. The photocatalytic efficiency of this reduction depends largely on the adsorption and diffusion of hexavalent chromium ions on the surface of the photocatalyst. In this paper, polyaniline-TiO₂ composite can effectively improve the photocatalytic reduction performance and stability of hexavalent chromium ion. The effect of polyaniline (PANI) thickness on Cr(VI) activity and stability of photocatalytic reduction was studied by adjusting the content of PANI on Mesoporous TiO₂ (MT) surface. Under the irradiation conditions, the reaction results showed that the reduction rate was 100%, and the maximum reaction rate reached 0.62 min^-1 when the PANI modification was 3.0%. Moreover, the results showed that the reduction performance remained 100% after ten cycles. The main reason is that the PANI modified on the surface of TiO₂ is rich in positively charged amino group, which can efficiently adsorb the reactant Cr(VI), and make the product Cr(III) leave the reaction interface quickly, thus ensuring the performance of photocatalyst.