TiO2 particles were immobilized on activated charcoal granules by means of a sol-gel method to use as a photosterilization catalyst capable of adsorbing microbial cells. The amounts of Escherichia coli cells adsorbed to the TiO2-immobilized activated charcoal (T/AC) granules were determined at temperatures of 288 to 303 Ii, and the maximum and minimum amounts of adsorbed cells were obtained at 288 and 293 K, respectively, At a temperature of 298 K, the relation between the amounts of adsorbed and suspended cells can be expressed by the Freundlich adsorption isotherm in the range of T/AC concentrations of 0.1 to 1.0 kg/m(3), Under light irradiation with a black light fluorescent lamp, sterilization of E. coli cells was carried out in the slurry of T/AC granules at temperatures of 288 to 303 Ii and T/AC concentrations of 0 to 0.1 kg/m3, The sterilization rates changes depending on the temperatures, and the highest and lowest rates are obtained at 288 and 293 Ii, respectively. The apparent sterilization rate constants are determined on the basis of a series-event model under various sterilization conditions, The rate constants can he correlated with the concentration of T/AC granules by taking into account the adsorption of cells to the T/AC granules.