Two Birds with One Stone Strategy: Simultaneous Removal of Cr(VI) and Cr(III) Efficiently by Porous ZnIn2S4/SBA-15 Nanorods

Carcinogen Cr(VI) is reduced efficiently into Cr(III) by a photocatalyst, but the produced Cr(III) is difficult to transfer from the photocatalytic active site. The "two birds with one stone" strategy is proposed to realize the in situ growth of ZnIn2S4 nanoplates on SBA-15 and the creation of separated active sites, in which ZnO loading on the porous SBA-15 nanorod was used as a zinc source. Obtained samples ZnIn2S4/SBA-15 (ZIS/SBA) showed the redshift of the absorption band and better separation of photoinduced carriers than pristine ZnIn2S4, due to its smaller size and S defect. All of the Cr(VI) was reduced to Cr(III) by the ZIS/SBA sample during the photocatalytic process, which was 2 times higher than pristine ZnIn2S4. Moreover, 92.8% of Cr(III) was adsorbed simultaneously during photocatalysis due to the electrostatic interaction from SBA-15. In addition, the ZIS/SBA sample showed good recycling stability after 5 times cycles, providing a new strategy for the in situ growth of ZnIn2S4 on the surface of porous materials and a novel way for the simultaneous removal of Cr(VI) and Cr(III) during photocatalysis.