BACKGROUND: The present study focuses on the photocatalytic transformation and mineralization of triclosan (TCS) using TiO2 catalyst. The main objectives were: (a) to investigate the effect of TiO2, TCS concentration and irradiation intensity on the photocatalytic efficiency and to model the degradation and mineralization percentage of TCS using response surface methodology (RSM) based on central composite design (CCD); (b) to identify transformation products (TPs) and degradation mechanisms, (c) to assess the toxicity of the TPs. RESULTS: The results from the RSM analysis indicated that all operating parameters studied have significant effects on TCS degradation and mineralization. A quadratic response surface model was found to fit the experimental data and was used to find the optimum experimental conditions. Scavenging experiments indicated that HO center dot radicals were principally responsible for TCS degradation. The transformation of TCS involved reactions of mono- and di-hydroxylation, dechlorination, and cleavage of the ether bond. Total detoxification of the treated solution was obtained after 30min, as revealed by Microtox bioassay. CONCLUSION: TCS can be effectively degraded and mineralized using TiO2 under simulated solar light avoiding the formation of highly toxic TPs. RSM modeling provided a statistically accurate prediction of the optimum degradation and mineralization of TCS. (C) 2014 Society of Chemical Industry