In this paper the photocatalytic degradation of o-phenylenediamine as the deputy of organic pollutant in aqueous solutions with CuO/X zeolite as a photocatalyst under UV irradiation has been studied Photocatalyst was prepared by ion exchanging process of parent synthetic zeolite NaX with copper(II) nitrate aqueous solution (0 1 M) for 8 h followed by drying and calcination at 450 C for 4h The parent zeolite ion exchanged media and photocatalyst were characterized by X-ray diffraction infrared spectroscopy atomic absorption spectroscopy BET and thermal analysis methods The degradation process was monitored during the experimental runs through UV/vis absorption as well as COD and TOC concentration determination and HPLC methods The effects of various key operating parameters and the effect of hydrogen peroxide and potassium bromate on the degradation rate of o-phenylenediamine were studied The optimum values were 0 1 g L-1 of photocatalyst 10 ppm of o-phenylenediamine pH of 9 25 C 20 0 mM of H2O2 and 10 0 mM of KBrO3 The results showed that the degradation kinetic of OPD can be described by Langmuir-Hinshelwood equation (C) 2010 Elsevier B V All rights reserved