The photocatalytic activity of tetra(4-carboxyphenyl)porphyrin with different metal centers (Fe(III), Cu(II), Zn(II) and metal-free), adsorbed on TiO2 surface has been investigated by carrying Out the photodegradation of atrazine in aqueous solution and under visible light irradiation. Under this condition, no photocatalytic activity was found meaning that anion superoxide (which was evidenced by photodegradation of luminol) is not sufficiently oxidant to degrade atrazine. However by adding hydrogen peroxide in the solution, a degradation of atrazine was observed. Under this condition, the maximum photocatalytic activity was obtained Using Cu(II) porphyrin as photosensitizer (82% of degradation after 1 h of irradiation). The influence of H2O2 concentration has been studied. It has been found that in the range 0.015-0.05 mol L-1 the higher the concentration the higher the rate of degradation, whereas for higher H2O2 concentrations, the rate of degradation leveled off. Intermediate products were identified Using high performance liquid chromatography-Diode Array Detector (HPLC-DAD) and GC-MS and a mechanism of degradation was proposed. (C) 2009 Elsevier B.V. All rights reserved.