Effects of Particle Size of TiO₂ on Photocatalytic Degradation of Methylene Blue in Aqueous Suspensions

The influence of particle size of TiO 2 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 suspended TiO 2 particles increased as the particle sizes of TiO 2 decreased. Photocatalytic activity of TiO 2 also increased as the particle size of TiO 2 became 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 the particle sizes of TiO 2 decreased. The first-order reaction rate constant for photodegradation of MB increased as the particle size of TiO 2 decreased. The initial degradation rate of MB in a suspended model was higher than that of a fixed-bed model. This will overcome the difficulty of preparation of ultrafine TiO 2 catalyst particles. Once the problem of separation of fine TiO 2 particles is solved, a TiO 2 suspended photoreactor could be provided on an industrial basis.