Study On The Control Of Typical Brominated Flame Retardants In Water

Brominated flame retardants?BFRs? are a newly emerged variety of persistent organic pollutants, of which polybrominated diphenyl ethers?PBDEs?, tetrabromobisphenol A?TBBPA? and hexabromocyclododecane?HBCD? are most important three ones. Decabromodiphenyl ether?BDE-209? is of highest demand in PBDEs. PBDEs, TBBPA and HBCD are detected in the industrial sewage of the East River. At the present time, there are very limited practical technologies to remove these BFRs, and especially in the case of the BFRs mixtures. In the work, we studied the removal of TBBPA, BDE-209 and HBCD using the oxidation and light degradation processes, thus to explore the approaches to deal with BFRs in actual water bodies.The results showed that it is effective to remove TBBPA by ozonation and potassium permanganate oxidation. The removal of TBBPA by ozonation is quick. Large ozone dosage, alkaline condition, high temperature and small initial substrate concentration are in favor of the removal of TBBPA. But it will produce bromate when ozone dosage is in excess. The removal of TBBPA by potassium permanganate oxidation is also fast. TBBPA removal increased with larger potassium permanganate concentration, lower the p H value and initial substrate concentration. Permanganate oxidation does not generate bromate. When potassium permanganate concentration is in excess, the reaction of potassium permanganate oxidation of TBBPA is first order reaction. The results also showed that ozonation and potassium permanganate oxidation of BDE-209 and HBCD are ineffective.254 nm ultraviolet degradation of BDE-209 and TBBPA have a good removal. When initial concentration are 0.3 ?mol/L, they can be completely degraded in 60 min and 120 min respectively. To further enhance the reaction rate, UV/Na₂SO₃ advanced reduction at the same ultraviolet light source is applied in BDE-209 and TBBPA removal studies. Contrast to the UV alone, removal of both has improved, and increased in condition of larger Na₂SO₃ concentration, p H value and smaller initial concentration. UV and UV/Na₂SO₃ degradation reactions are fit for first order reaction kinetics. 254 nm ultraviolet light degradation of HBCD has shown that the reaction rate is relatively slow. Degradation rate of 0.3 ?mol/L HBCD is 90% in 24 h.For HBCD, 185 nm ultraviolet is applied for its degradation. When the initial concentration is 0.3 ?mol/L, HBCD can be degraded completely by 79 W/185 nm ultraviolet light in 2 h. Meanwhile TBBPA and BDE-209 were also studied in 185 nm ultraviolet, and results showed they were degraded completely just in 20 min and 40 min.By compare the above removal method for typical brominated flame retardants TBBPA, BDE-209 and HBCD, we can get the following conclusion: when only TBBPA in the actual water, preferred potassium permanganate oxidation process, when BDE-209 exist at the same time, preferred Na₂SO₃/UV?254 nm? advanced reduction process, when present HBCD, choose 185 nm UV degradation.