Study On The Degradation Of Tetrabromobisphenol A By Fe(?)/S(?) System

Brominated flame retardants?BFRs?are one of the most common flame retardant materials,which are widely used in homes and office.The large-scale production and discharge of BFRs cause environment pollution and bioacc umulation,threatening human health.Tetrabromobisphenol A?TBBPA?is the most widely used BFRs and usually removed by photodegradation,which can achieve great removal efficiency.However,limited by high cost and practical condition,it is hard for photodegradation to realize expansion applications.As a new AOPs technology for water treatment,S?IV?auto-oxidation system is environment friendly,cost efficiency and has good treatment efficiency.But there are few studies on S?IV?auto-oxidation system,also no report about its application on TBBPA degradation.In this paper,TBBPA was taken as the representative pollutant,and Fe???/HSO₃^-system were selected as the typical S?IV?auto-oxidation system to study the degradation efficiency of TBBPA.This research investigate the influence of operating conditions and water conditions on the degradation effect,and reveal the reaction mechanism,environmental hazards and practical application prospect,provide a new idea for the removal of BFRs.The results showed that Fe???could effectively activate sulfite.When the initial pH of the reaction was 6.0,the optimal dosage of Fe???and sulfite was 40?M and 0.4 mM,respectively,the removal efficiency of TBBPA was about 66.4%after 30 min.The degradation efficiency and reaction rate decreased with the increasing dose of Fe???.Elevating the dosage of sulfite could accelerate the reaction rate,but there was no significant changes in the degradation efficiency after 20 min.The apparent rate constant was inversely proportional to the substrate concentration.Fe???/HSO₃^-system was suitable for a wide range of pH,and had good performance when pH was 3⁷.About 60%TBBPA could be removed under weakly acidic condition?pH 3⁶?after 30 min,whereas no degradation was achieved under alkaline condition.When exploring the reaction mechanism,it was found that the Fe???/HSO₃^-system mainly relied on HO^·to degrade TBBPA.Since the generation of radicals in S?IV?auto-oxidation system was achieved by chain reaction,and the rapid oxidation of SO₃^·-to SO₅^·-by O₂ was a crucial step in this reaction,the system needs to ensure that there was enough dissolved oxygen in the water.LC/MS production analysis and density functional theory,which could reflect the reaction reactivity of each atom in TBBPA molecules,were combined to speculate the possible degradation pathway of TBBPA.It was found that in TBBPA molecules,Br26,Br27,Br28,Br29,O30 and O32 are vulnerable to radical attack,and the initial reaction is debromination of TBBPA or bromine atoms replaced by hydroxyl groups.To further illustrate the engineering application prospect of this system,remove of TBBPA in real water was investigated.The results shows that the degradation efficiency in real water was obvious lower than that of pure water,because of HCO ₃^-and HA can compete with TBBPA for radicals.But there still 41.0%TBBPA removal was achieved after 30 min.Different from the persulfate activation system,no BrO₃^-and bromine-containing by-products?Br-DBPs?were generated during the degradation of TBBPA by Fe???/HSO₃^-system.The acute toxicity analysis results showed that this system was safety and had good detoxification effect during the degradation of TBBPA.In addition,the study also compared the agentia costs of the Fe???/HSO₃^-system with the traditional Fenton system and the iron-activated persulfate system,and concluded that the agentia costs of the system were relatively low and had broad application prospects.