Abstract
To activate the photocatalytic behavior of predominantly amorphous TiO2 fine particles, the surfaces of the particles were modified by immersion in sulfuric acid aqueous solutions with different concentration, followed by heating at 525℃ for 1 h. The photocatalytic activity for acetaldehyde decomposition under UV irradiation increased on increasing the sulfuric acid concentration in the solutions used for immersion from 0.001 N to 1 N ; however, intermediate products, such as acetic acid, methanol and formic acid, were generated and remained in the case of immersion in 1 N sulfuric acid aqueous solution. The rate of decomposition of acetaldehyde remarkably increased, without generation of intermediate products, on using 0.001 N sulfuric acid for the immersion of amorphous TiO2 fine particles. Since only immersion in a sulfuric acid aqueous solution did not activate the photocatalytic behavior of rutile TiO2 particles, they were treated with a 3 mass％ aqueous solution of hydrogen peroxide, followed by immersion in a 1 N sulfuric acid solution and heat treatment. The rate of decomposition of acetaldehyde under UV irradiation using the surface treated rutile particles was increased about 10 times higher than that of the untreated rutile particles.
