| Tetrabromobisphenol A[4,4’-isopropylidenebis(2,6-dibromophenol),TBBPA],accounting for nearly 60%of the total brominated flame retardant market share,is primarily used as the flame retardant in printed circuit boards and also as additives in many consumer products,e.g.textiles and plastics.Based on the biodegradation results of TBBPA in different environmental media,including soil,river sediment and water,the estimated half-life of TBBPA in the environment was～2 months.Considering the recalcitrant nature of TBBPA in the environment and its potential risk,it is greatly needed to develop efficient techniques to eliminate TBBPA.It is reported that TBBPA can be degraded by δ-MnO2,UV irradiation,photosensitized oxidation,ozonation and sulfate radicals.However,the toxic byproducts,e.g.brominated isopropylphenol derivatives or carcinogenic bromate ions were generated during the degradation process.In order to efficiently degrade TBBPA,iron(Ⅲ)-tetraamidomacrocyclic ligand(Fe(Ⅲ)-TAML)activator was selected in the present study.Fe(Ⅲ)-TAML is a porphyrin-like macromolecule,which has been widely used to degrade various organic pollutants as a water-soluble "green" catalyst.The immobilization of metallic porphyrins has been proved to enhance the reactivity and stability of the macromolecules.Therefore,adsorption and surfactant-assisted self-assembly method were used to synthesize Fe(Ⅲ)-TAML-based composites.In order to immobilize Fe(Ⅲ)-TAML,layered double hydroxides(LDH)was served as the adsorbent to synthesize the composite Fe(Ⅲ)-TAML/LDH.Fe(Ⅲ)-TAML/LDH showed superior reactivity to free Fe(Ⅲ)-TAML by increasing the collapsing frequency and enhancing the LDH interlayer pH conditions via hydrolysis of carbonate ions and Mg-O basic sites.Moreover,surfactant-assisted self-assembly method was also used to synthesize Fe(Ⅲ)-TAML-based micromaterials Fe(Ⅲ)-TAML/DODMA and Fe(Ⅲ)-TAML/DODMA/PFOA.Fe(Ⅲ)-TAML/LDH exhibited superior reactivity compared to free Fe(Ⅲ)-TAML due to the effect of adsorption and enhanced basic interlayer environment.Fe(Ⅲ)-TAML/DODMA could effectively protect Fe(Ⅲ)-TAML from H+-induced demetalation by hydrophobic alkyl chains of DODMA.Fe(Ⅲ)-TAML/DODMA/PFOA efficiently enhanced the reactivity of Fe(Ⅲ)-TAML via hydrogen bonding between Fe(Ⅲ)-TAML and PFOA,which significantly promotes the ionization of axial water molecule and enhances the reactivity of Fe(Ⅲ)-TAML under near-neutral pH conditions. |
