In this study, the photodegradation of some water pollutants in the presence of CdO cauliflower-like nanostructure as a photocatalyst has been investigated. This architecture was synthesized using mechanochemical process followed by heating treatment. An experimental design was done to evaluate the synthesis conditions and determine the optimum reaction via the band gap energy optimization. This parameter, selected as a response for the design of experiments (DOE), was estimated by the diffuse reflectance spectroscopy (DRS). Four factors of the calcining temperature, milling duration, calcining duration and reactants molar ratio (M/L) were chosen to have a sequence of 9 samples to analyze. The optimized structure with the band gap energy of 2.22 eV and high surface area showed the highest removal efficiency for the applied pollutants. The results revealed that this product can be prone for degradation activity in a visible region. Minitab and Qualitek-4 statistical softwares were used for data analysis. (c) 2012 Elsevier Ltd. All rights reserved.