The catalyst of cerium supported on activated carbon (Ce/AC) for ozonation was prepared and the catalytic activity was evaluated by the degradation of p-toluenesulfonic acid (p-TSA). The results showed that Ce/AC catalyst could not only greatly enhance the degradation of p-TSA but also significantly increase the efficiency of COD removal by ozonation. The COD removal could reach 74.1% with the Ce/AC catalyst at 60 min, while the effects of activated carbon (AC) catalyst and without catalyst were only 62.4% and 50.8%, respectively. The superiority of Ce/AC catalyst was attributed to the fact that cerium increased the generation of hydroxyl radicals (OH), which could react with p-TSA and intermediate to form oxidized products rapidly. Based on the intermediates detected by GC/MS. IC and HPLC, a possible degradation pathway of p-TSA was proposed. Our aim is to provide basic data and theoretical support for pharmaceutical wastewater treatment by catalytic ozonation. (c) 2014 Published by Elsevier B.V.