Adsorption Performance and Photocatalytic Activity of La-TiO₂@kaolin Composites

Abstract La-TiO 2 @kaolin(LTK) composites were prepared via sol-gel method with kaolin, lanthanum nitrate and tetrabutyl titanate as raw materials. The samples were characterized by XRD, SEM/EDS, and UV-Vis. The visible light photocatalytic reduction activity and adsorption performance of samples for Cr(VI) were studied. The results showed that La doping can refine TiO 2 grains, stabilize phase structure of anatase TiO 2 , and expand its absorption spectrum, thereby enhancing its photocatalytic reduction activity. Due to the composite of kaolin, the dispersion of TiO 2 is improves and it is endowed with a large specific surface area lead to enhance its adsorption ability for Cr(VI). The adsorption equilibrium process of LTK for Cr(VI) conforms to the Langmuir equation model. The coupling effect of doping and composite modification improves the adsorption and visible light catalytic reduction activity of Cr(VI) over composite material samples. The adsorption-photocatalytic removal rate of LTK for Cr(VI) under visible light irradiation for 6 hours reached the highest of 96.5%. The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO 2 .