BACKGROUNDSeveral pharmaceuticals have been detected as minor pollutants in industrial waste, surface and ground water. Among these compounds, antacids are the most widely consumed. Recently, advanced oxidation processes (AOPs) have been acknowledged as very promising methodologies to degrade and remove pharmaceutical compounds from water. RESULTSThe advanced oxidation of omeprazole (OME) promoted by the TiO2/UV system in aqueous medium was investigated. Monitoring this reaction by HPLC and TOC, it was demonstrated that while degradation of OME is quite efficient under these conditions, its mineralization is not complete. Continuous monitoring by IR spectroscopy demonstrated the breaking of the OME structure giving rise to two main intermediate groups, pyridine and benzimidazole derivatives. These aromatic compounds were eventually converted into trans-unsaturated carboxylic and amino acids. A total of 14 intermediate reaction products were identified by GC-MS analysis. Among these, the hydroxylated compounds stand out since they become more abundant as time moves forward, as evidenced by FT-IR and UV-vis analysis. GC-MS and FT-IR studies indicate the presence of nitro derivatives such as nitrophenol and nitrobenzimidazole in the reaction mixtures. CONCLUSIONBased on these experimental results, a total mechanism for photocatalytic oxidation of OME is proposed indicating benzimidazole and alkyl pyridine degradation pathways. Utilizing several analytical techniques, some fundamental aspects of the oxidative mechanism of OME were elucidated such as mode and sites of oxidation. Studies on degradation mechanisms are fundamental for future applications of photocatalysis in the removal of pharmaceutical compounds from residual water. (c) 2017 Society of Chemical Industry