Metal Complex Catalytic Reduction Of 2,2',4,4'-tetrabromodiphenyl Ether (BDE-47)

As a brominated flame retardant,polybrominated diphenyl ethers?PBDEs?are widely used in electronic appliances,building materials,textiles,furniture and other products.In recent years,with the increasing concentration of PBDEs in the environment,the related degradation technology becomes particularly important.2,2',4,4'-tetrabromodiphenyl ether?BDE-47?,as a homologue of BDE-209,has been reported as a new organic pollutant because of its toxicity,persistence and bioaccumulation.The treatment technology is mainly used photodegradation method,microbial degradation method,physical method and chemical oxidation reduction method degradation,but these methods have their shortcomings: low removal rate,long reaction cycle,and can not completely de-bromine and generate toxicity higher intermediate products and final products.Based on the effect of ball milling aluminum powder and the catalytic reduction of vitamin B₁2 and its high efficiency in degradation of halogenated organic compounds,this article first proposed the reduction and degradation of polybrominated diphenyl ethers catalyzed by ball milling aluminum powder in conjunction with vitamin B₁2,and constructed ball milling aluminum powder/vitamin B₁2-methanol/water-BDE-47 reaction system.The ball milling aluminum powder used in this experiment possesses stronger reduction ability than the traditional zero valent iron as well as high surface activity which can provide more active sites in the reaction.In this study,BDE-47 can be successfully removed by combining the B₁2 powder with ball milling aluminum powder,nano-tin powder and nano-iron powder respectively.The effects of vitamin B₁2 dosage,metal dosage,pH value,pretreatment condition,reaction concentration on the degradation rate of BDE-47 have been investgated.First of all,the ball milling method was used to prepare aluminum powder,then characterized by XRD,SEM,BET,ICP.The results show that the size of the aluminum powder is less than 5 ?m and the specific surface area is 27.9 m2/g.Subsequently,the synergistic effects of milling aluminum powder and vitamin B₁2 on the catalytic reduction of BDE-47 were investigated by batch experiment.Finally,the mechanism of BDE-47 catalytic reduction by ball-milling aluminum powder and vitamin B₁2 was studied,the whole reaction B₁2 did not change,mainly based on its strong nuc leophilic action to achieve electronic directional transfer.The optimum reaction condition is as follow: methanol-water ratio 40:60,ball milling aluminum powder dosage 2.0 g/L,vitamin B₁2 dosage 0.3 mM,initial pH 4.0.Under the optimal reaction conditions,96.4% of BDE-47 with concentration of 50 mg/L could be removed after 30 min reaction.Subsequently,the influence factors of nano-tin powder on vitamin B₁2 were discussed and the optimized conditions were obtained.The optimum reaction conditio ns for the reduction of BDE-47 were as follows: methanol-water ratio 40:60,ball milling aluminum powder dosage 1.0g/L,vitamin B₁2 dosage 0.2 mM,initial pH10.0.Under the optimum reaction conditions,BDE-47 of 50 mg/L can be removed 99.2% after 30 min of reaction.The optimal reaction conditions for the reduction of BDE-47 catalyzed by nano-iron powder and vitamin B₁2 were as follows: the dosage of nano-iron powder was 0.15 g/L,the dosage of vitamin B₁2 was increased by 0.1 mM,and the initial pH was abo ut 6.Under the optimum reaction conditions,BDE-47 of 10 mg/L can be removed 91.62% after 120 min of reaction.