Modeling the mineralization of an organic pollutant was studied using a slurry of TiO2 powder. 2-4 dichlorophenol was chosen as the target molecule. In a first stage, a study was carried out, on the basis of a semi-empirical approach in order to define the optimal concentration of the catalyst. In a second stage, a series of photocatalytic mineralization was performed with a laboratory set-up using an artificial UV source. The parameters involved in the kinetics of mineralization were identified by a comparison of results obtained by simulations and experiments at constant but different levels of irradiation. In a third stage, the robustness and suitability of the model were tested with experiments carried out with an experimental solar set-up with different dimensions. No supplementary adjustment of parameters was needed to simulate the experiments performed under unsteady irradiation. Finally, the model is used to illustrate the great variation in treatment capability of a solar photocatalytic process depending on the weather conditions and, more particularly, the seasonal variations in UV irradiation.