ZnO nanomaterials of different morphologies are synthesized by different methodologies. These semiconductor photocatalysts are potentially explored for self-sensitized photodegradation of malachite green (MG) dye in water in a batch reactor. The effects of various parameters like initial dye concentration, catalyst loading, solution pH, light source on degradation efficiency was also investigated. The experimental results showed substantial reduction of COD, besides removal of colour. The photodegradation of MG dye followed the pseudo first order kinetics of Langmuir-Hinshelwood model. The hydrothermally synthesized flower shaped homocentric pencil like ZnO nanorod bundles exhibit excellent photocatalytic activity under solar light. A comparative study of photodegradation efficiency among ZnO nanopartides, ZnO nanoparticles (hydrothermal) and flower shaped homocentric pencil like ZnO nanorod bundles were also performed. Semiconductor photocatalysis often leads to partial or complete mineralization of organic pollutants. The CO2 gas evolved due to mineralization of MG was determined using Warburg manometric method under solar light. The possible mechanism of photodegradation under both solar and UV light were also proposed. (C) 2014 Elsevier B.V. All rights reserved.