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首页> 外文期刊>Environmental Science & Technology >Use of Dithionite to Extend the Reactive Lifetime of Nanoscale Zero-Valent Iron Treatment Systems
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Use of Dithionite to Extend the Reactive Lifetime of Nanoscale Zero-Valent Iron Treatment Systems

机译：使用连二亚硫酸盐来延长纳米零价铁处理系统的反应寿命

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摘要

Nanoscale zero-valent iron (NZVI) represents a promising approach for source zone control, but concerns over its reactive lifetime might limit application. Here, we demonstrate that dithionite (S_2O_42-), a reducing agent for in situ redox manipulation, can restore the reducing capacity of passivated NZVI. Slurries of NZVI were aged in the presence (3 days) and absence 160 days) of dissolved oxygen over a range of pH values (6-8). Upon loss of reactivity toward model pollutants (1,1,1,2-tetrachloroethane, hexavalent chromium [Cr(VI)), nitrobenzene}, aged suspensions were reacted with dithionite, and the composition and reactivity of the drthionite-treated materials were determined. NZVI aging products generally depended on pH and the presence of oxygen, whereas the amount of dithionite influenced the nature and reducing capacity of products generated from reaction with aged NZVI suspensions. Notably, air oxidation at pH ≥ 8 quickly exhausted NZVI reactivity despite preservation of significant Fe(0) in the particle core. Under these conditions, formation of a passive surface layer hindered the complete transformation of NZVI particles into iron(lll) oxides, which occurred at lower pH. Reduction of this passive layer by low dithionite concentrations |<1 g/g of NZVI) restored suspension reactivity to levels equal to, and occasionally greater than, that of unaged NZVI. Multiple dithionite additions further improved pollutant removal, allowing at least a 15-fold increase in Cr(VI) removal [～300 mg of Cr(VI)/g of NZVI] relative to that of as-received NZVI [～20 mg of Cr(VI)/g of NZVI].
机译：纳米零价铁（NZVI）代表着一种有前途的源区控制方法，但对其反应寿命的担忧可能会限制其应用。在这里，我们证明了连二亚硫酸盐（S_2O_42-），一种原位氧化还原处理的还原剂，可以恢复钝化NZVI的还原能力。 NZVI浆液在存在溶解氧（3天和不存在160天）的pH值范围内（6-8）进行老化。在对模型污染物（1,1,1,2-四氯乙烷，六价铬[Cr（VI）），硝基苯}失去反应活性后，使老化的悬浮液与连二亚硫酸盐反应，并确定了经连二硫酸氢盐处理的材料的组成和反应性。 NZVI老化产物通常取决于pH值和氧气的存在，而连二亚硫酸盐的量会影响与NZVI老化悬浮液反应生成的产物的性质和还原能力。值得注意的是，尽管在颗粒核中保留了大量的Fe（0），但在pH≥8的空气氧化过程中，NZVI反应性迅速耗尽。在这些条件下，钝化表面层的形成阻碍了NZVI颗粒完全转变为氧化铁（III），而氧化铁在较低的pH值下发生。低连二亚硫酸盐浓度（<1 g / g NZVI）降低了该钝化层，可将悬浮液的反应性恢复至与未老化的NZVI相同的水平，有时甚至更高。多次连二亚硫酸盐的添加进一步改善了污染物的去除，相对于原先的NZVI [〜20 mg Cr]，Cr（VI）的去除率[〜300 mg Cr（VI）/ g NZVI]至少增加了15倍。 （VI）/克NZVI]。

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  • 来源
    《Environmental Science & Technology》 |2010年第22期|p.8649-8655|共7页
  • 作者

    YANG XIE; DAVID M. CWIERTNY;

  • 作者单位

    Department of Chemical and Environmental Engineering, University of California-Riverside, A242 Bourns Hall, Riverside, California 92521, United States;

    Department of Chemical and Environmental Engineering, University of California-Riverside, A242 Bourns Hall, Riverside, California 92521, 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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