Enhanced photocatalytic activity of titanium dioxide/allophane mixed powder by acid treatment

Abstract The TiO 2 /allophane mixed powders at various mixing ratios were acid-treated to obtain a highly active photocatalyst. It was found that amorphous silica surrounding TiO 2 particles was formed after acid treatment by selective dissolution of alumina component in the allophane. The photocatalytic activity of the mixed powder, evaluated by the photocatalytic decomposition rate for gaseous acetaldehyde, was improved by the acid treatment when the mixing ratio of allophane was higher than 5 mass% in spite of the decrease of specific surface area (SSA), while that of the pure-TiO 2 powder was decreased maybe because of the increase of Ti 3 + defects density on its surface. As for the pure-allophane powder, SSA and adsorption rate for acetaldehyde were decreased by acid treatment. In addition, it was found that the acid treatment of allophane was needed to be performed in the presence of TiO 2 to obtain a highly active photocatalyst from the result of the comparative experiments using mixed powder of acid-treated TiO 2 powder and acid-treated allophane powder. Based on these results, it was concluded that the silica-dispersed microstructure of the nanocomposite was suitable for the efficient removal of acetaldehyde.