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

Qianwei Liang, Xin Chen, Ruina Liu, Ke Xu, Hanjin Luo
Journal of environmental sciences (China) 2023 v.124 pp. 360-370
adsorption, aerogels, graphene, graphene oxide, irradiation, light, photocatalysis, photocatalysts, synergism, virulence, wavelengths, China
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 ZnₓCd₁₋ₓS with graphene aerogel to contrast TiO₂-ZnₓCd₁₋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 Zn₀.₅Cd₀.₅S, as well as TiO₂ graphene aerogel (TGA) and Zn₀.₅Cd₀.₅S 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 Zn₀.₅Cd₀.₅S 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.