The effects of trichloroethylene (TCE) gas flow rate, relative humidity, TiO2 film thickness, and UV light intensity on photodegradation of TCE have been determined in an annular flow type photoreactor. Phosgene and dichloroacetyl chloride formation could be controlled as a function of TCE gas flow rate and photodegradation of TCE decreased with increasing relative humidity. The optimum thickness of TiO2 film was found to be approximately 5 mum and the photocatalytic reaction rate of TCE increased with square root of UV light intensity. In addition, the effects of the initial TCE concentration, phase holdup ratio of gas and solid phases (epsilon(g)/epsilon(s)) CuO loading on the photodegradation of TCE have been determined in an annulus fluidized bed photoreactor. The TCE photodegradation Aecreased with increasing the initial TCE concentration. The optimum conditions of the phase holdup ratio and CuO wt.% for the maximum photodegradation of TCE was found to be 2.1 and 1.1 wt.%, respectively. Therefore, an annulus fluidized bed photoreactor is an effective tool for TCE degradation over TiO2/silica gel with efficient utilization of photon energy. (C) 2003 Elsevier Ltd. All rights reserved.