This study aims to understand the efficiency and role of adsorption of common water pollutants (volatile organic chemicals (VOCs), pharmaceuticals and carboxylic acids) in the catalytic ozonation process on gamma-alumina. In order to understand the catalytic processes occurring, the effects of pH, hydroxyl radical scavengers, humic acids and phosphates on the efficiency of catalytic ozonation on alumina were studied. The results revealed that catalytic zonation on alumina could substantially enhance the removal of ibuprofen and acetic acid when compared with ozonation alone. However, alumina did not catalyse the removal of VOCs. The adsorption of pollutants plays a key role in the effectiveness of this process. The presence of hydroxyl radical scavengers, phosphates and humic acids had a significant effect on the removal of pollutants on alumina. It is therefore suggested that catalytic ozonation of organic pollutants on alumina proceeds via a radical mechanism that involves reactions of hydroxyl radicals with pollutants adsorbed on the surface of alumina. (C) 2014 Elsevier B.V. All rights reserved.