| With the rapid development of chromium industry,a large amount of chromium-containing wastewater is discharged into the natural environment.Cr(Ⅵ)is highly toxic and is listed as the first category of pollutants by Integrated Wastewater Discharge Standard.The photocatalysis is currently one of the most promising methods for removing Cr(Ⅵ).The research of cheap and efficient photocatalysts has become a hotspot at home and abroad.In this paper,the safe and environmentally friendly photocatalyst,Ti O2 is selected as the substrate,and the cheap and easily available dye,alizarin is used as the surface modifier.Alizarin-titanium dioxide(AL-Ti O2)composite is synthesized by a one-step hydrothermal method in order to improve the photocatalytic Cr(Ⅵ)removal efficiency of Ti O2.The structural composition and optical properties of the photocatalyst are systematically analyzed by SEM,XRD,UV-vis and other methods.Afterwards,the photocatalytic reduction effect of AL-Ti O2 composite on Cr(Ⅵ)under visible light is investigated and the influencing factors of the photocatalytic reaction are analyzed.Finally,a possible mechanism of the reaction is proposed.The results show that alizarin and Ti O2 are connected to each other through Ti-O-C bonds,and there are oxygen vacancies on the surface of the composite.The total removal rate of Cr(Ⅵ)over AL-Ti O2 composite is 99.4 % with 60 min of irradiation,and the photocatalytic degradation rate constant is about 46 times than that of pure Ti O2.The amount of alizarin introduced,the p H value,and the ratio of material to liquid in the system are all factors that affect the photocatalytic reaction.The LMCT excitation process is formed between alizarin and Ti O2,which reduces the band gap of the Ti O2 and extends the optical response range of the composite to the visible light region.The oxygen vacancies produced also inhibit the recombination of photogenerated electron-hole and improve the electron transport capability. |
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