Microwave-Specific Effects in Various TiO2 Specimens. Dielectric Properties and Degradation of 4-Chlorophenol

Microwave specific effects on various potential TiO2 photocatalyst specimens were examined for the photodecomposition of 4-chlorophenol (4-CP) with regard to physical and chemical properties and by the characterization of dielectric properties such as the dielectric loss factor (epsilon ''), the dielectric constant (epsilon'), and the dielectric loss tangent (tan delta = epsilon ''/epsilon'). Dielectric properties were measured in both dispersed TiO2 particles in a 4-CP aqueous solution and in TiO2 pellets prepared from the specimens' powders. The irradiation efficiency of the microwave for the TiO2 particles in aqueous media is discussed on the basis of the changes in the dielectric loss factor and penetration depth from the increase in the temperature of water. Changes in crystalline shape and the estimated band gap energies were analyzed before and after irradiation by the microwaves. Of particular significance, the band gap energies were estimated by an in situ observation method under UV and microwave irradiation conditions.