Carbon tetrachloride transformation on the surface of nanoscale biogenic magnetite particles.
Carbon tetrachloride transformation on the surface of nanoscale biogenic magnetite particles.
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DOI：
10.1021/es030487m
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发表时间：
2004-02
影响因子：
11.4
通讯作者：
M. McCormick;P. Adriaens
中科院分区：
文献类型：
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作者：
M. McCormick;P. Adriaens
地下环境中的铁还原条件通过生物和非生物途径促进脱氯反应，后者通常通过异化铁还原细菌（DIRB）形成的生物活性矿物质介导。在这里，我们报道了由DIRB金属还原杆菌产生的纳米级生物磁铁矿/磁铁矿颗粒对四氯化碳（CT）进行非生物转化的主要产物和途径。产物形成和自由基/二氧化碳捕获研究表明，CT转化通过三个平行途径发生。第一种途径（氢解）通过三氯甲基自由基（*CCl3）和可能的三氯甲基碳离子（**CCl3-）生成氯仿（45-50%）。第二和第三种途径涉及二氯甲烷中间体（**CCl2），该中间体要么水解生成CO（约38%）（二氧化碳水解），要么进一步还原生成甲烷（8-10%）（二氧化碳还原）。**CCl2生成甲烷的机理尚不清楚，但推测可能涉及一系列表面配位的类碳化合物和自由基配合物。通过碳介导途径形成的大量相对良性产物表明，磁铁矿/磁铁矿颗粒在CT污染环境的修复中可能具有有益的应用。
Iron-reducing conditions in subsurface environments promote dechlorination reactions via both biotic and abiotic pathways, the latter often mediated via biologically activated minerals formed by dissimilatory iron-reducing bacteria (DIRB). Here we report the major products and pathways associated with the abiotic transformation of carbon tetrachloride (CT) by nanoscale biogenic magnetite/maghemite particles produced by the DIRB Geobacter metallireducens. Product formation and free radical/carbene trapping studies indicate that CT transformation occurs via three parallel pathways. The first pathway (hydrogenolysis) results in the formation of chloroform (45-50%) via a trichloromethyl free radical (*CCl3) and possibly a trichloromethyl carbanion (**CCl3-). The second and third pathways involve a dichlorocarbene intermediate (**CCl2), which either hydrolyzes to form CO (approximately 38%) (carbene hydrolysis), or undergoes further reduction to yield methane (8-10%) (carbene reduction). The mechanism of methane formation from **CCl2 is not known, but is speculated to involve a sequence of surface coordinated carbenoid and free radical complexes. The large fraction of relatively benign products formed by the carbene-mediated pathways suggests that magnetite/maghemite particles may have a beneficial application in the remediation of CT contaminated environments.