The ultrasonic spray drying and modification of colloidal particles was proposed and applied to the control of the photocatalytic activity of titania particles. The cystalline phases, chemical compositions and morphologies of the produced particles were investigated by XRD, FTIR, centrifugal particle size analyzer, SEM/EDAX, TEM/EDAX. Photocatalytic activity of the modified particles was determined by measuring the rate of trichloroethylene(TCE) decomposition.
The spherical and micro-porous aggregates of primary particles were produced by the ultrasonic spray drying of suspended titania(Degussa P25) particles, and the size of these aggregates was changed depending on the size of droplet and the concentration of suspended titania particles in the spray solution. The Degussa P25 titania and the spray dried titania have the same physical and chemical characteristics in crystalline phase, crystallite size and photochemical activity.
The morphologies of modified titania particles are same with the spray dried titania except for being more micro-porous. The photocatalytic activity is, however, slightly higher than pure titania, when the metal or metal oxide loading is low. As the modifier loading is further increased, the photocatalytic activity is sharply decreased and becomes constant. This implies that the initial surface modification determines the photocatalytic activity and the further modification does not affect the chemical property.
