Heterogeneous photocatalysis employing titanium dioxide has emerged as an efficient method to remove a wide range of toxic compounds from polluted waters. In particular, chlorophenols constitute an important group of aquatic contaminants that have been successfully degraded by photocatalysis. In this work, the modeling of a slurry reactor for the photocatalytic degradation of 4-chlorophenol (4-CP) is presented. The experimental reactor is a thin rectangular parallelepiped limited by two parallel windows made of borosilicate glass. It is illuminated from one side by two tubular UV lamps (UV Philips TLK40/09N) located at the focal axis of cylindrical reflectors of a parabolic cross-section. The flat plate reactor is placed inside the loop of an isothermal, batch recycling system. The model describes the degradation of 4-CP as well as the formation and disappearance of the main intermediate products: 4-chlorocatechol (4-CC) and hydroquinone (HQ). Intrinsic kinetic expressions, previously obtained in a laboratory scale reactor, were employed to solve the mass balance for each species. To take account of the radiation effects on the reaction rate, the radiative transfer equation was solved in the flat plate reactor. The radiation model involves two spatial variables and two angular variables in the direction of radiation propagation.To validate the model, experimental runs were conducted by varying the catalyst loading (0.05, 0.1, 0.5, 1.0 x 10-3 g/cm3) and the 4-CP initial concentration (0.7 and 1.4 x 10-7 mol/cm3). Good agreement was found between simulation results and experimental data. Based on the experimental and predicted concentrations of 4-CP and 4-CC, the root mean square error (RMSE) of the model was 9.9 %.