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Kinetics and Mechanisms of Nanosilver Oxysulfidation

机译：纳米银氧硫化的动力学及机理

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摘要

Among the many new engineered nanomaterials, nanosilver is one of the highest priority cases for environmental risk assessment. Recent analysis of field samples from water treatment facilities suggests that silver is converted to silver sulfide, whose very low solubility may limit the bioavailability and adverse impact of silver in the environment. The present study demonstrates that silver nanopaiticles react with dissolved sulfide species (H_2S, HS~_) under relevant but controlled laboratory conditions to produce silver sulfide nanostructures similar to those observed in the field. The reaction is tracked by time-resolved sulfide depletion measurements to yield quantitative reaction rates and stoichiometries. The reaction requires dissolved oxygen, and it is sensitive to pH and natural organic matter. Focused-ion-beam analysis of surface films reveals an irregular coarse-grained sulfide phase that allows deep (> 1 μm) conversion of silver surfaces without passivation. At high sulfide concentrations, nanosilver oxysulfidation occurs by a direct particle-fluid reaction. At low sulfide concentration, quantitative kinetic analysis suggests a mechanistic switch to an oxidative dissolution/precipitation mechanism, in which the biologically active Ag+ ion is generated as an intermediate. The environmental transformation pathways for nanosilver will vary depending on the media-specific competing rates of oxidative dissolution and direct oxysulfidation.
机译：在许多新的工程纳米材料中，纳米银是环境风险评估中最优先的案例之一。最近对来自水处理设施的现场样品的分析表明，银已转化为硫化银，其极低的溶解度可能会限制其在环境中的生物利用度和不利影响。本研究表明，在相关但受控的实验室条件下，银纳米颗粒与溶解的硫化物物种（H_2S，HS__）反应，生成的硫化银纳米结构与本领域观察到的相似。通过时间分辨的硫化物耗竭测量来跟踪反应，以得到定量的反应速率和化学计量。该反应需要溶解的氧气，并且对pH和天然有机物敏感。表面膜的聚焦离子束分析显示不规则的粗颗粒硫化物相，可以使银表面进行深度（> 1μm）的转化而无需钝化。在高硫化物浓度下，纳米银氧硫化通过直接的颗粒-流体反应发生。在低硫化物浓度下，定量动力学分析表明机理向氧化溶解/沉淀机理的转变，其中以生物活性形式的Ag +离子作为中间体生成。纳米银的环境转化途径将根据氧化溶解和直接氧硫化的特定于介质的竞争速率而变化。

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  • 来源
    《Environmental Science & Technology》 |2011年第17期|p.7345-7353|共9页
  • 作者

    Jingyu Liu; Kelly G. Pennell; Robert H. Hurt;

  • 作者单位

    Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States;

    Civil and Environmental Engineering Department, University of Massachusetts-Dartmouth, Dartmouth, Massachusetts 02747,United States;

    School of Engineering, Institute for Molecular and Nanoscale Innovation, Brown University, Providence, Rhode Island 02912,United States;

  • 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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  • 正文语种 eng
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