In this study, the degradation of a widely used non-steroidal anti-inflammatory drug ibuprofen (IBP) by UV/Fe(III)/Oxone was conducted. IBP decomposition by sole-UV, UV/Fe(III), Fe(III)/Oxone and UV/Oxone processes was also carried out to evaluate the isolated effects contributing to IBP degradation. The influence of pH levels, the concentration of Fe(III) and Oxone, and inorganic anions on the performance of UV/Fe(III)/Oxone process was evaluated. SPME (Solid phase microextraction)/GC/MS were used to identify the intermediates for the first time. Nineteen intermediates/byproducts were detected during IBP degradation, among which six escaped from the detection in previous studies. Based on the analysis of intermediates, possible decay pathways of IBP were proposed accordingly. Decarboxylation and hydroxylation were believed to be major reaction mechanisms involved in IBP degradation by UV/Fe(III)/Oxone process. (C) 2015 Elsevier B.V. All rights reserved.