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Mapping the Reactions in a Single Zero-Valent Iron Nanoparticle

机译：映射单个零价铁纳米粒子中的反应

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摘要

Nanoscale zerovalent iron (nZVI) possesses unique functionalities for metal-metalloid removal and sequestration. So far, direct evidence on the heavy metal-nZVI reactions in the solid phase is still limited due to low concentration of heavy metals and small size of nanoparticles. In this work, angstrom-resolution spectral mappings on the reactions of nZVI with chromate, arsenate, nickel, silver, cesium, and zinc ions are presented. This work was achieved with spherical aberration-corrected scanning transmission electron microscopy integrated with high-sensitivity X-ray energy-dispersive spectroscopy-scanning transmission electron microscopy (XEDS-STEM). Results confirm that iron nano particles have a core-shell structure. In addition, the removal mechanism significantly depends on the standard potential E-0 (E-0 is standard potential w.r.t. standard hydrogen electrode at 25 degrees C when free ion activity is 1.). For strong oxidiing agent, such as Cr(VI), the removal mechanise is diffusion and encapsulation in the core area of the nZVI particle. For moderate oxidizers, such as As(V) with E-0 more positive than that of iron, the removal mechanism is adsorption at the surface, followed by diffusion and encapsulation into the particle between the core and the shell. For metal cations with an E-0 close to or more negative than that of iron, such as Cs(I) and Zn(II), the removal mechanism is sorption or surface-complex formation. For metal cations with E-0 much more positive than that of iron, such as Ag(I), the removal mechanism is rapid reduction on the surface of nZVI. Meanwhile, metals with E-0 slightly more positive than that of iron, such as Ni(II), can be immobilized at the nanoparticle surface via sorption and reduction. The synergetic effects of sorption, reduction, and encapsulation mechanisms of nZVI lead to rapid reactions and high efficiency for treatment and immobilization of many toxic heavy metals. Results also demonstrate that the XEDS-STEM technique is a powerful tool for studying reactions in individual nanoparticles and is particularly valuable for mapping trace-level elements in environmental media.
机译：纳米级零价铁（nZVI）具有去除金属和螯合金属的独特功能。到目前为止，由于重金属浓度低和纳米粒子尺寸小，有关固相中重金属-nZVI反应的直接证据仍然有限。在这项工作中，提出了nZVI与铬酸根，砷酸根，镍，银，铯和锌离子反应的埃分辨率光谱图。这项工作是通过与高灵敏度X射线能量色散光谱-扫描透射电子显微镜（XEDS-STEM）集成的球差校正扫描透射电子显微镜完成的。结果证实铁纳米颗粒具有核-壳结构。另外，去除机理在很大程度上取决于标准电势E-0（当自由离子活度为1时，E-0是在25℃下的标准电势w.r.t.标准氢电极）。对于强氧化剂，例如Cr（VI），去除机理是扩散和封装在nZVI颗粒的核心区域。对于中等氧化剂，例如E-0比铁更正的As（V），去除机理是在表面吸附，然后扩散并封装到核与壳之间的颗粒中。对于E-0接近或比铁负的E-0的金属阳离子（例如Cs（I）和Zn（II）），去除机理是吸附或表面复合物形成。对于E-0比铁更正的金属阳离子，例如Ag（I），去除机理是nZVI表面的快速还原。同时，可以通过吸附和还原将E-0比铁的正性稍微强一些的金属（例如Ni（II））固定在纳米颗粒表面。 nZVI的吸附，还原和包封机制的协同作用可导致快速反应，并能高效处理和固定多种有毒重金属。结果还表明，XEDS-STEM技术是研究单个纳米颗粒中反应的有力工具，对于在环境介质中绘制痕量元素的映射特别有用。

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  • 来源
    《Environmental Science & Technology》 |2017年第24期|14293-14300|共8页
  • 作者

    Ling Lan; Huang Xiaoyue; Li Meirong; Zhang Wei-xian;

  • 作者单位

    Tongji Univ, State Key Lab Pollut Control, Sch Environm Sci & Engn, 1239 Siping Rd, Shanghai 200092, Peoples R China;

    Tongji Univ, State Key Lab Pollut Control, Sch Environm Sci & Engn, 1239 Siping Rd, Shanghai 200092, Peoples R China;

    Tongji Univ, State Key Lab Pollut Control, Sch Environm Sci & Engn, 1239 Siping Rd, Shanghai 200092, Peoples R China;

    Tongji Univ, State Key Lab Pollut Control, Sch Environm Sci & Engn, 1239 Siping Rd, Shanghai 200092, Peoples R China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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