纳米零价铁降解水中多溴联苯醚(PBDEs)及降解途径研究

Reductive Debromination of Polybrominated Diphenyl Ethers in Aquifier by Nano Zero-valent Iron: Debromination Kinetics and Pathway

纳米零价铁（nZVI）法是多溴联苯醚（polybrominated biphenyl ethers，PBDEs）脱溴的有效方法．其反应动力学与途径对阐明PBDEs降解机制具有重要意义．本研究采用液相还原法制备的nZVI，在含有表面活性剂聚乙二醇辛基苯基醚（Triton X-100）的条件下，46h内完全降解商用八溴联苯醚（octa-BDE）混合物中高溴代物质（7-9个溴代的同系物），其降解过程符合类一级反应动力学（pseudo-first-order）方程，平均降解速率常数（k）为0．106h^-1．本研究利用数量结构保留关系（quantatitive-structure retention relationship，QSRR）模型建立了在缺乏全系标准样品的情况下PBDEs降解产物的有效分析方法．通过混标中39种PBDEs各标准物在气相色谱中的保留时间，再以BDE47和BDEl83的平均保留时间归一化后得到每种标准物的相对保留时间（relativeretentiontime，RRT），再将数据库中的相对保留时间指数（relative retention time index，RRTI）与实验测得的相对保留时间拟合，得到QSRR模型．利用该模型对octa-BDE降解产物进行定性分析，推导得出nZV!对octa-BDE的还原降解途径．结果表明，nZVI对PBDEs的逐级脱溴过程中，间位的溴原子最容易被取代．

Nano-zerovalent iron （nZVI） approach is effective in the debromination of polybrominated biphenyl ethers （PBDEs）. The kinetics and degradation pathway are the key issues to understand the PBDEs degradation mechanisms. In this study, nZVI, synthesized through liquid phase reduction method, coupled with Triton X-100, could completely debrominate the highly brominated congeners of a commercial octa-BDEs mixture within 46 h. The debromination of octa-BDEs could be described by means of pseudo- first-order kinetics with the reaction constant （k） of 0. 106 h-l. In case of lacking the PBDE standards, an effective approach has been developed to determine the unknown PBDE congeners using the quantitative-structure retention relationship （QSRR） model. The retention time of all 39 PBDE congeners in a standard mixture was firstly analyzed with gas chromatography coupled with an electron capture detector （GC-ECD）, and the relative retention time （RRT） for each standard was obtained after normalizing the RT by the average RT of BDE47 and BDE183. Then a QSRR model was developed by fitting the RRT of each PBDE congener and its specific RRT index. The debromination products of octa-BDEs were identified using this QSRR model and the degradation pathway of octa- BDEs was elucidated. The results showed that in the stepwise reductive debromination process of PBDEs by nZVI, meta-debromin was facile to be degraded.