The effects of the ratio of TiO2/silica gel, superficial gas velocity (U-g), solid circulation rate (G(s)), initial trichloroethylene (TCE) concentration, wavelength of UV light, and concentrations of H2O and O-2 on photodegradation of TCE over TiO2/silica gel have been determined in a circulating fluidized bed (CFB) photoreactor. The TCE conversion decreases with wavelength of the UV light, the initial TCE and H2O concentrations in the CFB reactor. The optimum concentration of O-2 for TCE degradation is found to be approximately 9 vol.% in the CFB photoreactor. The CFB photoreactor is an effective tool for high TCE degradation with efficient utilization of photon energy. (C) 2004 Elsevier B.V. All rights reserved.