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首页> 外文期刊>Environmental Science & Technology >Characterization and properties of metallic iron nanoparticles: Spectroscopy, electrochemistry, and kinetics
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Characterization and properties of metallic iron nanoparticles: Spectroscopy, electrochemistry, and kinetics

机译：金属铁纳米颗粒的表征和性质：光谱学，电化学和动力学

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There are reports that nano-sized zero-valent iron (Fe-0) exhibits greater reactivity than micro-sized particles of Fe-0, and it has been suggested that the higher reactivity of nano-Fe-0 may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In an effort to better understand the reactivity of nano-Fe-0, we have used a variety of complementary techniques to characterize two widely studied nano-Fe-0 preparations: one synthesized by reduction of goethite with heat and H-2 (Fe-H2) and the other by reductive precipitation with borohydride (Fe BH). Fe H2 is a two-phase material consisting of 40 nm alpha-Fe-0 (made up of crystals approximately the size of the particles) and Fe3O4 particles of similar size or larger containing reduced sulfur; whereas Fe-BH is Mostly 20-80 nm metallic Fe particles (aggregates of < 1.5 nm grains) with an oxide shell/coating that is high in oxidized boron. The FeBH particles further aggregate into chains. Both materials exhibit corrosion potentials that are more negative than nano-sized Fe2O3, Fe3O4, micro-sized Fell, or a solid Fe-0 disk, which is consistent with their rapid reduction of oxygen, benzoquinone, and carbon tetrachloride. Benzoquinone-which presumably probes inner-sphere surface reactions-reacts more rapidly with Fe EIH than Fe-H2, whereas carbon tetrachloride reacts at similar rates with Fe BH and Fe-H2, presumably by outer-sphere electron transfer. Both types of nano-Fe-0 react more rapidly than mic rosized Fe-0 based on mass-normalized rate constants, but surface area-normalized rate constants do not show a significant nano-size effect. The distribution of products from reduction of carbon tetrachloride is more favorable with Fe-H2, which produces less chloroform than reaction with Fe-BH.
机译：有报道说，纳米级零价铁（Fe-0）的反应性比微米级的Fe-0颗粒大，并且已经表明，纳米级Fe-0的较高反应性可能为地下水修复提供优势。或其他环境应用。但是，大多数这些报告都是初步的，因为它们留下了许多潜在的重要（通常是具有挑战性的）材料或过程变量，这些变量或过程变量不受控制或无法解决。为了更好地了解纳米Fe-0的反应性，我们使用了多种互补技术来表征两种广泛研究的纳米Fe-0制备物：一种是通过热和H-2（Fe- H2），另一种则用硼氢化物（Fe BH）还原沉淀。 Fe H2是一种两相材料，由40 nmα-Fe-0（由近似于颗粒大小的晶体组成）和类似尺寸或更大的Fe3O4颗粒组成，并含有还原的硫；而Fe-BH主要是20-80 nm的金属Fe颗粒（<1.5 nm晶粒的聚集体），其氧化物壳/涂层的氧化硼含量高。 FeBH颗粒进一步聚集成链。两种材料均显示出比纳米级的Fe2O3，Fe3O4，微米级的Fell或固态的Fe-0圆片更负的腐蚀电位，这与其快速还原氧气，苯醌和四氯化碳相一致。与Fe-H2相比，可能探测到内球表面反应的苯醌醌的反应要快于Fe EIH，而四氯化碳与Fe BH和Fe-H2的反应速率相似，大概是通过外球电子转移。基于质量归一化的速率常数，两种类型的纳米Fe-0均比微米化的Fe-0更快地反应，但是表面积归一化的速率常数并未显示出明显的纳米尺寸效应。 Fe-H2对四氯化碳还原反应的产物分布更有利，与与Fe-BH反应相比，氯仿产生的氯仿更少。

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