Brominated flame retardants have been widely used in industry.There is a rapid growing public concern for their availabilities in the environment.Advanced oxidation process (AOP) is a promising and efficient technology which may be used to remove emerging chemicals such as brominated flame retardants.This study aims at investigating optimal operational conditions for the removal of BDE-209 using nano-scaled titanium(IV) oxide.The residual PBDE congeners after photocatalytical degradation of BDE-209 by TiO2 were analysed by gas chromatography-mass spectrometry (GC-MS).It was found that the degradability of BDE-209 by TiO2 was attributed to its photocatalytic activity but not the small size of the particles.The half-life of removing BDE-209 by TiO2 was 3.05 days under visible light.Tetra- and penta-BDEs were the major degraded products of BDE-209.Optimum conditions for photocatalytical degradation of BDE-209 was found to be at pH 12 (93％ ± 1％),5,10,20 mg/L (93.0％ ± 1.70％,91.6％ ± 3.21％,91.9％ ± 0.952％,respectively),respectively of humic acid and in the form of anatase/mtile YiO2 (82％ ± 3％).Hence,the efficiency of removing BDE-209 can be maximized while being cost effective at the said operating conditions.