Efficient removal of Cr(VI) by a 3D Z-scheme TiO2-ZnxCd1-xS graphene aerogel via synergy of adsorption and photocatalysis under visible light

Abstract

Efficient and robust photocatalysts for environmental pollutants removal with outstanding stability have great significance. Herein, we report a kind of three dimensional (3D) photocatalyst presented as Z-scheme heterojunction, which combining TiO₂ and Zn_xCd_1-xS with graphene aerogel to contrast TiO₂-Zn_xCd_1-xS graphene aerogel (TSGA, x=0.5) through a moderate hydrothermal process. The as-prepared Z-scheme TSGA was used to remove aqueous Cr(VI) via a synergistic effect of adsorption and visible light photocatalysis. The adsorption equilibrium can be reached about 40 min, then after about 30 min irradiation under visible light (wavelength (λ) > 420 nm) the removal rate of Cr(VI) almost reached 100%, which is much better than the performance of pristine TiO₂ and Zn_0.5Cd_0.5S, as well as TiO₂ graphene aerogel (TGA) and Zn_0.5Cd_0.5S graphene aerogel (SGA). The virulent Cr(VI) was reduced to Cr(III) with hypotoxicity after photocatalysis on TSGA, meanwhile the as-synthesized TSGA presented a good stability and reusability. The reduced graphene oxide (rGO) sheets between TiO₂ and Zn_0.5Cd_0.5S played a role as charge transfer mediator, promoting the photoinduced electrons transfer and photocatalysis ability of TSGA was enhanced significantly. Hence, such photocatalyst exhibits a potential application on removing heavy metals with high efficiency and stability from polluted aqueous environment.

Keywords: Adsorption; Cr(VI); Graphene aerogel; Photocatalysis; Photocatalyst.