Microwave frequency effects on the photoactivity of TiO2: Dielectric properties and the degradation of 4-chlorophenol, bisphenol A and methylene blue

Microwave frequency (2.45 GHz and 5.8 GHz) effects on the photoactivity of P-25 TiO2 were examined for the photodecomposition of 4-chlorophenol (4-CP), bisphenol A (BPA) and methylene blue (MB), and by the characterization of dielectric properties. Changes in microwave (MW) irradiation efficiency between water and the TiO2 particulates were examined at two MW frequencies on the basis of penetration depth of the microwaves and the dielectric loss factor. TiO2 particles in aqueous media were less photoactive under 5.8-GHz microwave radiation in degrading the organic substrates than under 2.45-GHz microwaves for otherwise identical temperature conditions. Factors that affect the photoactivity of TiO2 at the two frequencies are briefly discussed.