Degradation Of Tbbpa By Ferrate(VI) And Intermediate Charateristics

As the largest amount of brominated flame retardants applied in the world, Tetrabromobisphenol A（TBBPA） has been detected in rivers, soil and other natural environments. For the treatment of TBBPA in the aquatic systems, most processes are found to have some drawbacks involving low efficiency. Owing to the efficient oxidation and flocculation toward the refractory organic chemicals, potassium ferrate（K₂FeO₄） has potential applications in terms of the removal of TBBPA. In present work, we have studied the law of TBBPA removal by K₂FeO₄ and analyzed the intermediates of TBBPA. An efficient and harmless process for TBBPA removal is proposed on the basis of the comparison of various strengthening processes.The variation tendency of TBBPA removal by K₂FeO₄ and biological toxicity are investigated by static experiment. The results indicates that with more dosage of K₂FeO₄, less dosage of TBBPA or lower initial p H value, higher percent of TBBPA can be removed. At the temperature lower than 50 ℃, the removal efficiency of TBBPA increases first and then decreases, with the highest value at 30 ℃. In terms of coexisting substances, Fe³⁺、Cu²⁺、Cl^-、and SO₄^2- promotes the removal of TBBPA slightly, while HCO₃^-, NH₄⁺ and NOM have an inhibition effect on the removal. Due to the formation of intermediate products of TBBPA during the degradation process, the variation of biological toxicity increases first and then decreases.The intermediate products of TBBPA during the degradation process are identified and analyzed, thus providing a deep understanding of the reason behind the variation tendency of biological toxicity. The results suggests there is no bromate detected in inorganic intermediate products. The positive correlation is found between the production of bromide ion and removal efficiency of TBBPA. In addition, the removal of bromide ion remains at a low level even if the TBBPA is almost totally removed. For the organic intermediate products, the primary reaction products are consisted of Bisphenol A and dibromophenol. The degradation of TBBPA is speculated to experience two pathways, including brominated process and cleavage of C-C bond. By studying the generation, biological toxicity and removal of dibromophenol, this paper further demonstrates that the intermediate products produced by TBBPA degradation are contributed to the increase of biological toxicity.Combined with above results, comparsion of various strengthening processes including strengthening K₂FeO₄ process, K₂FeO₄/O₃ process and K₂FeO₄/H₂O₂ process is conducted in order to realize the totoal removal of TBBPA, improve the debromination and decrease the biological toxicity of reaction process simultaneously. K₂FeO₄/O₃ process is observed to be the most efficient for the removal of TBBPA and it is recommended to be applied to treat TBBPA in water.