Sol-gel synthesis and photocatalytic activity of In0.05TiO2(x)/HGB composite suspended in azophloxine solution

Low-density In 0.05 TiO 2 ( 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 0.05 TiO 2 in the composite, and n (In): n (Ti) is 0.05:1.). The dispersion of In 0.05 TiO 2 onto the surface of HGB slightly reduced the crystallite size of anatase TiO 2 . The bandgap energies of In 0.05 TiO 2 ( 20 )/HGB, In 0.05 TiO 2 ( 30 )/HGB, In 0.05 TiO 2 ( 60 )/HGB and In 0.05 TiO 2 were calculated to be 3.28, 3.21, 3.15 and 3.10 eV, respectively. The BET surface area of the pure In 0.05 TiO 2 is 36.4 m 2 /g, and the pore volume is 0.0575 cm 3 /g. Both the BET surface area and pore volume of the In 0.05 TiO 2 ( x )/HGB composites are reduced with a decreasing In 0.05 TiO 2 content. If In 0.05 TiO 2 content is more than 40%, the photocatalytic activities of the composites are almost as strong as that of the pure In 0.05 TiO 2 . The azophloxine solution was completely decolorized after 90 min in the presence of In 0.05 TiO 2 ( 60 )/HGB or pure In 0.05 TiO 2 . The activity of the composites has a close correlation with the produced hydroxyl radicals. The In 0.05 TiO 2 ( 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. Graphical Abstract Highlights Low-density In 0.05 TiO 2 ( x )/HGB composite photocatalyst was synthesized via a sol-gel route. The In 0.05 TiO 2 ( x )/HGB composites can float on the surface of the azophloxine solution after reaction. The dispersion of In 0.05 TiO 2 onto the surface of HGB slightly reduced the crystallite size of anatase TiO 2 . The activity of In 0.05 TiO 2 ( x )/HGB is as strong as the fine indium doped TiO 2 powders.