Congener-specific dechlorination of dissolved PCBs by microscale and nanoscale zerovalent iron in a water/methanol solution
Congener-specific dechlorination of dissolved PCBs by microscale and nanoscale zerovalent iron in a water/methanol solution
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DOI：
10.1021/es049835q
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发表时间：
2004-10-01
影响因子：
11.4
通讯作者：
Johnson, KM
中科院分区：
文献类型：
--
作者：
Lowry, GV;Johnson, KM
受多氯联苯污染的沉积物仍然对人类和水生生态系统构成重大威胁。疏浚和处置成本高昂，因此需要可行的现场多氯联苯脱氯技术。这项研究表明，纳米零价铁（ZVI）脱氯多氯联苯低氯化产物在环境条件下，提供了深入了解PCB异构体之间的结构-活性关系，并比较了纳米ZVI的反应性的钯化微米ZVI。对六种多氯联苯同系物（22 '、34'、234、22'35'、22'45'和33'44'）进行了研究，以比较每种同系物的初始脱氯率，并监测氯的去除顺序。在30%甲醇/水混合物中使用200克/升纳米级零价铁，观察到的表面积归一化准一级多氯联苯脱氯速率常数范围为1 x 10（-6）至5.5 x 10（-4）L yr（-1）m（-2），取决于所测试的多氯联苯同系物。使用200 g/L的钯化（0.05 wt %）微型ZVI，表面积归一化的准一级PCB脱氯速率常数明显更快，范围为3.8 x 10（-2）至1.7 x 10（-1）L yr（-1）m（-2），但这些速率是不可持续的。对于纳米ZVI，非邻位取代的同系物有更快的初始脱氯速率比邻位取代的同系物在同一同系物组。帕拉和Meta位的氯主要是在邻位的氯，这表明，毒性更大的共面多氯联苯同系物不太可能形成毒性较低的非共面，邻位取代的同系物。在实验过程中没有观察到完全脱氯。多氯联苯脱氯是足够快的纳米零价铁可能提供新的原位补救多氯联苯污染的沉积物的替代品。
Polychlorinated biphenyl (PCB)-contaminated sediments remain a significant threat to humans and aquatic ecosystems. Dredging and disposal is costly, so viable in situ technologies to dechlorinate PCBs are needed. This study demonstrates that nanoscale zerovalent iron (ZVI) dechlorinates PCBs to lower-chlorinated products under ambient conditions, provides insight into structure-activity relationships between PCB isomers, and compares the reactivity of nanoscale ZVI to that of palladized microscale ZVI. Six PCB congeners were studied (22', 34', 234, 22'35', 22'45', and 33'44') to compare the initial rate of dechlorination of each and to monitor the order in which chlorines are removed. Using 200 g/L of nanoscale ZVI in a 30% MeOH/water mixture, observed surface-area normalized pseudo-first-order PCB dechlorination rate constants ranged from 1 x 10(-6) to 5.5 x 10(-4) L yr(-1) m(-2) depending on the PCB congener tested. Using 200 g/L of palladized (0.05 wt %) microscale ZVI, surface-area normalized pseudo-first-order PCB dechlorination rate constants were significantly faster and ranged from 3.8 x 10(-2) to 1.7 x 10(-1) L yr(-1) m(-2), but these rates were not sustainable. For nanoscale ZVI, nonorthosubstituted congeners had faster initial dechlorination rates than orthosubstituted congeners in the same homologue group. Chlorines in the para and meta position were predominantly removed over chlorines in the ortho position, which suggests that more-toxic coplanar PCB congeners are not likely to form from less-toxic noncoplanar, orthosubstituted congeners. Complete dechlorination was not observed over the course of the experiments. PCB dechlorination is rapid enough that nanoscale ZVI may offer novel in situ remedial alternatives for PCB-contaminated sediments.