The photocatalytic degradation of Direct Yellow12 (DY12) was studied by a batch process using ZnO as the catalyst on irradiation with UV light. The influence of pH, catalyst weight and initial concentration of the dye on the degradation of the dye was investigated. The degradation of the dye was found to be effective in alkaline media. The dye degradation obeyed first order kinetics and explained on the basis of Langmuir-Hinshelwood mechanism. The oxidants involved were identified as positive hole, hydroxyl radical and superoxide anion radical. (C) 2009 Elsevier B.V. All rights reserved.