Polyaniline modified SnO2 nanoparticles for efficient photocatalytic reduction of aqueous Cr(VI) under visible light

Polyaniline (PANI) was adopted to modify SnO2 nanoparticles for developing a promising high efficiency visible light-driven photocatalyst for the treatment of Cr(VI)-polluted wastewaters. PANI modified SnO2 nanoparticles (SnO2/PANI nanocomposites) were synthesized via the following procedures: (i) SnO2 nanoparticles were synthesized by hydrothermal treatment of SnCl4·5H2O in deionized water at 200 °C for 15 h; and (ii) adsorption of PANI in N,N-Dimethylformamide solution by SnO2 nanoparticles, then evaporation of N,N-Dimethylformamide. The compositions, structures, optical and photoelectrochemical properties of SnO2/PANI nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high resolution transmission electron microscopy, UV-vis diffuse reflectance spectra, photocurrents measurements and electrochemical impedance spectra. The photocatalytic tests showed that SnO2/PANI nanocomposites had far higher photocatalytic activity than SnO2 nanoparticles in the reduction of aqueous Cr(VI) under visible light (λ > 420 nm) irradiation (for example, the reaction rate constant for photocatalytic reduction of Cr(VI) by the most efficient SnO2/PANI-3% was about 23 times that by SnO2). Besides, the effects of photocatalytic experiment parameters (including dosage of photocatalyst, initial concentration and pH of Cr(VI) aqueous solution, and coexistent anions and cations) on the Cr(VI) removal rate by SnO2/PANI-3% were also investigated.