Identification the active species and reaction intermediates during the treatment of norfloxacin using Bi2WO6 photocatalysis were investigated in this study. To the best of our knowledge this is the first study on the active species and reaction intermediates for the degradation of any fluoroquinolones (FQs) using Bi2WO6 photocatalysis. The role of active species was determined by the influence of radicals' scavengers and selected ions. The overall efficiency of Bi2WO6 photocatalysis was ascribed to photolysis, photocatalysis-via hydroxyl radical ((OH)-O-center dot), and photocatalysis-via direct hole (h(+)) oxidation, and their contribution was determined to be 15.0, 79.3, and 5.7%, respectively. Fourteen intermediates were identified in the treated samples. Among them, the five amide intermediates in Bi2WO6 photocatalysis were resulted from the OH oxidation on the piperazine in FQs. A reaction formula was developed to describe this reaction where amine translated into amide by the attack of OH radicals. Moreover, a mathematical model was successfully built up to predict the intermediates accumulation as the concentration of initial probe and reaction time is given, which is useful in practical application. (C) 2014 Elsevier B.V. All rights reserved.