Department Soil and Environmental Sciences, National Chung Hsing University, Taichung, Taiwan.
Chemosphere. 2010 Mar;78(10):1200-6. doi: 10.1016/j.chemosphere.2009.12.061. Epub 2010 Feb 1.
Polybrominated diphenyl ethers (PBDEs) recognized as a new class of environmental persistent toxic contaminants have been distributed widely in the world. In this study, the synthesized nanoscale zerovalent iron (NZVI) in the laboratory was used to investigate the removal kinetics and mechanisms of decabrominated diphenyl ether (DBDE) at different pH. Within 40 min 90% of DBDE was rapidly removed by NZVI as compared to around 40 d needed for 24-fold weight of microscale ZVI. The removal by NZVI is much faster than that by microscale ZVI due to its high surface area and reactivity. At a different pH, the pseudo-first-order removal rate constants of DBDE linearly increased from 0.016 to 0.024 min(-1) with the decreasing of aqueous initial pH values from 10 to 5. The degradation of DBDE with NZVI is favorable in an acid condition. The debromination pathways of DBDE with NZVI were proposed on the basis of the identified reaction intermediates ranging from nona- to mono-brominated diphenyl ethers (BDEs) for an acid condition and from nona- to penta-BDEs for an alkaline condition. The debromination of PBDEs from para positions is more difficult than that from meta or ortho positions. Adsorption on NZVI also plays a role on the removal of DBDE. These findings can facilitate the treatment and fate prediction of PBDEs with NZVI in the environment.
多溴联苯醚（PBDEs）作为一类新的环境持久性有毒污染物，已在全球范围内广泛分布。本研究采用实验室合成的纳米零价铁（NZVI），研究了不同 pH 值条件下 NZVI 对十溴联苯醚（DBDE）的去除动力学和机制。在 40 分钟内，NZVI 可迅速去除 90%的 DBDE，而相比之下，24 倍质量的微尺度 ZVI 需要 40 天才能达到相同的去除效果。由于 NZVI 的高表面积和高反应活性，其去除速度远快于微尺度 ZVI。在不同 pH 值下，DBDE 的准一级去除速率常数随水初始 pH 值从 10 降低到 5 线性增加，从 0.016 增加到 0.024 min(-1)。在酸性条件下，DBDE 与 NZVI 的降解是有利的。基于所鉴定的反应中间体，从非溴代到单溴代二苯醚（BDEs）（对于酸性条件）和从非溴代到五溴代二苯醚（对于碱性条件），提出了 NZVI 条件下 DBDE 的脱溴途径。对 PBDEs 中对位的脱溴比间位或邻位的脱溴更困难。吸附在 NZVI 上也对 DBDE 的去除起作用。这些发现有助于 NZVI 在环境中处理和预测 PBDEs 的命运。
