Efficient photocatalytic reduction of aqueous Cr (VI) by Zr4+ doped and polyaniline coupled SnS2 nanoflakes

The synergistic Zr4+ doping and PANI coupling were used to improve the photocatalytic activity of SnS2 nanoflakes for the treatment of aqueous Cr (VI). The Zr-SnS2/PANI photocatalyst was prepared by a facile two-step method. The optimal Zr-SnS2/PANI-6% (with the Zr/Sn molar ratio of 1:8 and the PANI content of 6 wt%) exhibited dramatically higher photocatalytic activity toward Cr (VI) reduction than SnS2, Zr-SnS2, SnS2/PANI, and many previously reported SnS2-based and PANI-containing visible-light photocatalysts. Moreover, Zr-SnS2/PANI-6% showed outstanding performance in the photocatalytic treatment of Cr (VI)-containing electroplating solution. Based on the measured photo-electrochemical properties of the samples, the increased photocatalytic efficiency of Zr-SnS2/PANI-6% was mainly due to the synergistic effect induced by the smaller bandgap, higher charge transfer efficiency, and lower electron-hole recombination rate. Furthermore, the effects of coexisting cations and anions, photocatalyst amount, initial pH, Cr (VI) concentration, environmental atmosphere, and copresence of 1,4-benzoquinone or K2S2O8 on photocatalytic Cr (VI) reduction over Zr-SnS2/PANI-6% were investigated.