| Brominated flame retardants are widely used in production and life due to their low price and excellent flame retardant,PBDEs is one of the most popular flame retardants. They are widely used in electronic electrical,architecture,plastics,furniture. PBDEs in the production of human life more convent,but also caused a huge environmental burden.And PBDEs have a volatile,can through the atmosphere general circulation for long migration.At present all the environmental media are detected in PBDEs existence,such as water and sediment,the atmosphere even organisms,etc. Large studies show that,PBDEs will cause serious harm on ecological and human health,such as thyroid hormone interference effect,nervous system toxicity,the liver and kidney toxicity,immune toxicity and carcinogenicity,reproductive system toxicity,etc.At present PBDEs research mainly focus on its distribution rule and biological toxicity,and the degradation of the reports of research are relatively few. As PBDEs is listed as a new type of persistent organic pollutants,to explore the effective methods and mechanism of degradation for removing become more urgent,and will has the significant practical significance.This article chooses BDE-209to be the objects,respectively through the single factor and the orthogonal experiments discusses the influence factors and the optimum reaction conditions by two different technology of Fe/C+H2O2and Fe/C+H2O2+UV.The following main results have been achieved:(1)The degradation performance, influencing factors, optimization, reaction kinetics and mechanism of BDE-209in the Fe/C+H2O2process were systematically studied. The results indicated that the removal rate of BDE-209by Fe/C+H2O2was influenced by Fe/C quality, Fe dosing, water pH value, H2O2dosage and the reaction time.The order of influence to the degradation of BDE-209by each factor is H2O2dosage>water pH value> Fe/C quality> Fe dosing quantity> reaction time.The optimal operating conditions were as following: Fe/C=1:1,Fe dosing of9g, pH=1,H2O2dosage of6ml·L-1,reaction time of90min.(2)The degradation performance, influencing factors, optimization, reaction kinetics and mechanism of BDE-209in the Fe/C+H2O2+UV process were also systematically studied.After the similar experiments, it was founded that all the factors are there exists an optimal value make BDE-209to the highest degradation,above or below the best value, the removal rate of BDE-209all will decreased.The optimal operating conditions were as following:Fe/C=2:1,Fe dosing of9g, pH=5,H2O2dosage of5ml·L-1,reaction time of30min.(3)Two process on the degradation of BDE-209methodology all followed pseudo-first-order decay kinetics,and the Fe/C+H2O2+UV process has the high constant than Fe/C+H2O2. Reaction kinetics rate constant were0.0041and0.0097,show that UV and H2O2have synergy effect on the degradation of BDE-209.(4)Detected the degradation products of BDE-209by GC-MS,speculated that the degradation way there are two possible:one kind is·OH attack on benzene directly realize BDE-209gradually to take off the bromine degradation,another kind is·OH first would connect two aromatic ring ether key open, and then replace two respectively of benzene rings bromine atoms, open the benzene and broken the key, and finally realize BDE-209mineralization.In the degradation of BDE-209by Fe/C+H2O2+UV process,BDE-209absorb ultraviolet spectrum contribution to the degradation by taken off the bromines.Through the above experiments, the research results not only enrich the Iron-carbon Micro-electrolysis Immobilized Fenton Processes and their combination technology theory, but also for the degradation of PBDEs explore the new way. |
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