Zinc oxide crystallites were synthesized by two steps, solution free mechanochemical method. In order to obtain zinc oxide of different morphology and crystallite size, calcination temperature was varied from 400 to 900 degrees C. These photocatalysts are then characterized by X-ray diffraction (XRD), Scanning Electron Micrograph (SEM), Energy dispersive X-ray spectra (EDXS), Fourier transform infrared spectra (FT-IR) and UV-Visible spectrophotometer. X-ray diffraction data suggest that the obtained ZnO crystallites are of wurtzite structure. The zinc oxide crystallite growth rate is found to be different in different calcination temperature range. Photocatalytic activity of ZnO was checked by means of oxidative photocatalytic degradation (PCD) of resorcinol a potent endocrine disrupter in water under irradiation of sunlight in a batch photoreactor. The PCD efficiency was found to be dependent on crystallite growth rate and morphology of zinc oxide. The zinc oxide calcined from 400 degrees C to 550 degrees C exhibit same crystallite growth rate and showed maximum photocatalytic degradation of resorcinol. The PCD efficiency of zinc oxide was found to decrease with increase in calcination temperature as the particle size was increased. In addition to effect of calcination temperature, the influence of various other parameters such as photocatalyst amount, initial concentration of resorcinol and pH was also examined for maximum PCD of resorcinol. Neutral and basic pH is found to be favorable for chemical oxygen demand (COD) removal of resorcinol. (C) 2009 Elsevier B.V. All rights reserved.