Decabromodiphenyl ether (BDE209) poses a significant threat to human health. Most research so far has focused on BDE209 debromination by the reduction, which will produce more toxic products and further cause more serious environmental problems. In this study, we focused on thermally activated persulfate oxidation of BDE209. Various factors have been investigated, such as initial persulfate (0.05, 0.1, 0.2 and 0.5 M) or BDE209 content, temperature, pH and inorganic ion. The results show the of BDE209 removal rate constants (k(1)) indicated quadratic curve relationship with initial persulfate concentrations (k(1) = -0.293 x [PS](0)(2) + 0.267 x [PS](0) + 0.046, R-2 = 0.917, [PS](0) = 0.05-0.5 M) and a good linear relationship with initial BDE209 contents (k(1) = -0.004 x [BDE209](0) + 0.312, R-2 = 0.994). At the test pH range of 3-9, the highest degradation efficiency occurred at pH 5. However, inhibitory effects were observed in the presence of bicarbonate (HCO3(-)), and chloride (Cl-) exhibited either positive or inhibitive effect on the BDE209 degradation. The addition of an appropriate level of Cl- (e.g., [Cl-](0)/[PS](0) = 0.1/1) could significantly enhance the BDE209 decomposition, while higher contents of Cl- (e.g.,[Cl-](0)/[PS](0) = 2/1) resulted in totally inhibitory effect. (C) 2016 Elsevier B.V. All rights reserved.