Synthesis of TiO2 nanoparticles by a combined sol-gel ball milling method and investigation of nanoparticle size effect on their photocatalytic activities

TiO₂ nanoparticles were synthesized by a sol-gel method and the effect of ball milling of dried gel on the particle size has been investigated. The results show that the ball milling has a crucial role in preparation of nanosized TiO₂ powder. Also thermal treatment at different temperatures can control the size of prepared nanoparticles. The photocatalytic activities of TiO₂ nanoparticles with different sizes were studied by photocatalytic degradation of Congo red dye using a homemade photoreactor. The photo degradation of Congo red dye was monitored by UV-Vis absorption measurements. It was found that the nanopowders which were synthesized at 550 °C with average particle size of 55 nm show the maximum photocatalytic activities. These nanopowders which were a mixture of anatase and rutile phases did not show the same photocatalytic effect on Eriochrome black, Bromocresol green, Methyl orange and Rose Bengal dyes.