Effects of particle size of TiO2 on photocatalytic degradation of methylene blue in aqueous suspensions

The influence of particle size of TiO2 on the photocatalytic degradation of methylene blue (MB) in a suspended aqueous solution has been studied. The results suggested that the adsorption rate and adsorbability of MB on suspe nded TiO2 particles increased as the particle sizes of TiO2 decreased. Phot ocatalytic activity of TiO2 also increased as the particle size of TiO2 bec ame smaller, especially when the particle size is less than 30 nm. The half -life (t(0.5)) of the photocatalytic degradation of MB also decreased as th e particle sizes of TiO2 decreased. The first-order reaction rate constant for photodegradation of MB increased as the particle size of TiO2 decreased . The initial degradation rate of MB in a suspended model was higher than t hat of a fixed-bed model. This will overcome the difficulty of preparation of ultrafine TiO2 catalyst particles. Once the problem of separation of fin e TiO2 particles is solved, a TiO2 suspended photoreactor could be provided on an industrial basis.