Sol-gel synthesis and photocatalytic activity of In_0.05TiO₂(x)/HGB composite suspended in azophloxine solution

Low-density In_0.05TiO₂(x)/HGB composite was synthesized by loading indium doped titanium dioxide onto hollow glass bubbles (HGB) via a sol-gel route (x is the weight content of In_0.05TiO₂ in the composite, and n(In):n(Ti) is 0.05:1.). The dispersion of In_0.05TiO₂ onto the surface of HGB slightly reduced the crystallite size of anatase TiO₂. The bandgap energies of In_0.05TiO₂(20)/HGB, In_0.05TiO₂(30)/HGB, In_0.05TiO₂(60)/HGB and In_0.05TiO₂ were calculated to be 3.28, 3.21, 3.15 and 3.10 eV, respectively. The BET surface area of the pure In_0.05TiO₂ is 36.4 m²/g, and the pore volume is 0.0575 cm³/g. Both the BET surface area and pore volume of the In_0.05TiO₂(x)/HGB composites are reduced with a decreasing In_0.05TiO₂ content. If In_0.05TiO₂ content is more than 40%, the photocatalytic activities of the composites are almost as strong as that of the pure In_0.05TiO₂. The azophloxine solution was completely decolorized after 90 min in the presence of In_0.05TiO₂(60)/HGB or pure In_0.05TiO₂. The activity of the composites has a close correlation with the produced hydroxyl radicals. The In_0.05TiO₂(x)/HGB composites can float on the surface of the azophloxine solution after the photocatalytic reaction, so the material can be easily collected for the next treatment cycle.