| Polybrominated diphenyl ethers（PBDEs）,as a typical brominated flame retardant in environmental media,are widely detected in various environmental media,which seriously threaten the safety of ecological environment and human health.Therefore,the removal of PBDEs in the environment has become a hot topic.Clay minerals supported nano zero valent iron-based materials have good stability and strong reactivity,which can effectively remove halogenated organic pollutants,and has great application potential for environmental remediation.In this study,a typical natural one-dimensional nanostructure clay mineral attapulgite（ATP）was selected as the carrier precursor,and modified by octadecyl trimethyl ammonium chloride to prepare attapulgite（OA）.Then OA supported nanoscale zero valent Fe/Pd bimetallic composite（OA-Fe/Pd）was prepared by step reduction method.The degradation kinetics of 4,4-dibromophenyl ether（BDE15）and decabromodiphenyl ether（BDE209）in solution was studied by batch experiments.The degradation performance and mechanism of OA-Fe/Pd for different brominated PBDEs were discussed.The degradation performance and influencing factors of OA-Fe/Pd on BDE209 in contaminated soil tetrahydrofuran/water system were also investigated.The main results and conclusions are as follows:（1）OA-Fe/Pd material was successfully prepared with OA as carrier.Nanoscale zero valent Fe/Pd was successfully loaded on the surface of modified attapulgite.The bimetallic particles were spherical,and the particle size was between 50-100 nm.After loading,Fe/Pd bimetallic particles can be more evenly dispersed on the OA surface,which effectively inhibits the agglomeration of Fe/Pd bimetallic particles.Compared with other clay supported nano zero valent iron-based materials,OA-Fe/Pd had the best removal performance for representative polybrominated diphenyl ether BDE209.The cumulative removal amount of BDE209 by OA-Fe/Pd（0.025%）were 116.5 mg/g,which were significantly higher than that by OA-Fe/Pd（0.1%）.（2）Low brominated diphenyl ether（BDE15）could be completely debrominated into diphenyl ether（DE）by OA-Fe/Pd materials,and the removal mechanism were mainly reductive debromination.The degradation kinetics was in accordance with the pseudo first order kinetic equation.The kobsvalue increased with the increase of OA-Fe/Pd material dosage and Pd loading,but decreased with the increase of BDE15 initial concentration,tetrahydrofuran/water ratio and pH.Active hydrogen atom H*was the main reducing agent for the degradation of BDE15 by OA-Fe/Pd.H*reacted with C-Br of BDE15 molecule step by step,and finally completely debrominated into DE.（3）OA-Fe/Pd could effectively degrade BDE209 in solution,the degradation kinetics was in accordance with the pseudo first order kinetic equation.The kobsvalue increased with the increase of OA-Fe/Pd material dosage and Pd loading,but decreased with the increase of BDE209 initial concentration,tetrahydrofuran/water ratio and pH.The debromination mechanism of BDE209 in solution by OA-Fe/Pd were step by step reduction debromination.GC-MS results showed that BDE209 can be debrominated to DE under suitable conditions..The order of hydrodebromination of BDE209by OA-Fe/Pd were ortho>meta>para.（4）OA-Fe/Pd material had good removal performance for BDE209 in red soil tetrahydrofuran/water system,and its removal rate increased with the increase of OA-Fe/Pd material addition,and decreased with the increase of pH.The removal rate increased sharply in 0-3 h,and tended to be stable in 4-6 h.The degradation kinetics of BDE209 in red soil tetrahydrofuran/water system by OA-Fe/Pd was in accordance with the pseudo first order kinetic equation,and its kobs value increased with the increase of OA-Fe/Pd addition,and decreased with the increase of pH.The products of reductive debromination of BDE209 in red soil tetrahydrofuran/water system by OA-Fe/Pd were mainly medium brominated diphenyl ethers. |
