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首页> 外文期刊>Environmental Science & Technology >Impact of Organic Matter on Iron(Ⅱ)-Catalyzed Mineral Transformations in Ferrihydrite-Organic Matter Coprecipitates
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Impact of Organic Matter on Iron(Ⅱ)-Catalyzed Mineral Transformations in Ferrihydrite-Organic Matter Coprecipitates

机译：有机物对铁（Ⅱ）催化的水铁矿-有机物共沉淀物中矿物转化的影响

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摘要

Poorly crystalline Fe(III) (oxyhydr)oxides like ferrihydrite are abundant in soils and sediments and are often associated with organic matter (OM) in the form of mineralorganic aggregates. Under anoxic conditions, interactions between aqueous Fe(II) and ferrihydrite lead to the formation of crystalline secondary minerals, like lepidocrocite, goethite, or magnetite. However, the extent to which Fe(II)-catalyzed mineral transformations are influenced by ferrihydrite-associated OM is not well understood. We therefore reacted ferrihydrite-PGA coprecipitates (PGA = polygalacturonic acid, C:Fe molar ratios = 0-2.5) and natural Fe-rich organic flocs (C:Fe molar ratio = 2.2) with 0.5-5.0 mM isotopically labeled Fe-57(II) at pH 7 for 5 weeks. Relying on the combination of stable Fe isotope tracers, a novel application of the PONKCS method to Rietveld fitting of X-ray diffraction (XRD) patterns, and Fe-57 Mossbauer spectroscopy, we sought to follow the temporal evolution in Fe mineralogy and elucidate the fate of adsorbed Fe-57(II). At low C:Fe molar ratios (0-0.05), rapid oxidation of surface-adsorbed Fe-57(II) resulted in Fe-57 enriched crystalline minerals and nearly complete mineral transformation within days. With increasing OM content, the atom exchange between the added aqueous Fe-57(II) and Fe in the organic-rich solids still occurred; however, XRD analysis showed that crystalline mineral precipitation was strongly inhibited. For high OM-content materials (C:Fe = 1.2), Mossbauer spectroscopy revealed up to 39% lepidocrocite in the final Fe(II)-reacted samples. Because lepidocrocite was not detectable by XRD, we suggest that the Mossbauer-detected lepidocrocite consisted of nanosized clusters with lepidocrocite-like local structure, similar to the lepidocrocite found in natural flocs. Collectively, our results demonstrate that the C content of ferrihydrite-OM coprecipitates strongly impacts the degree and pathways of Fe mineral transformations and iron atom exchange during reactions with aqueous Fe(II).
机译：结晶度较弱的Fe（III）（羟基）氧化物如亚铁酸盐在土壤和沉积物中含量很高，并且通常以矿物有机聚集体的形式与有机物（OM）结合。在缺氧条件下，Fe（II）水溶液与亚铁酸盐之间的相互作用导致形成结晶性次生矿物，如纤铁矿，针铁矿或磁铁矿。但是，人们还不太了解Fe（II）催化的矿物转化受亚铁水合物相关OM的影响。因此，我们使水铁矿-PGA共沉淀物（PGA =聚半乳糖醛酸，C：Fe摩尔比= 0-2.5）和天然富铁有机絮凝物（C：Fe摩尔比= 2.2）与0.5-5.0 mM同位素标记的Fe-57（ II）在pH 7下5周。依靠稳定的Fe同位素示踪剂的组合，PONKCS方法在X射线衍射（XRD）图的Rietveld拟合和Fe-57 Mossbauer光谱学上的新应用，我们试图追踪Fe矿物学的时空演化并阐明吸附的Fe-57（II）的命运。在低的C：Fe摩尔比（0-0.05）下，表面吸附的Fe-57（II）的快速氧化导致富含Fe-57的晶体矿物，并在几天内几乎完成了矿物转化。随着OM含量的增加，仍会在添加的Fe-57（II）水溶液和富有机固体中的Fe之间发生原子交换。然而，XRD分析表明，晶体矿物沉淀被强烈抑制。对于高OM含量的材料（C：Fe> = 1.2），Mossbauer光谱显示在最终的Fe（II）反应样品中，高达39％的纤铁矿。由于XRD无法检测到纤铁矿，因此我们建议由Mossbauer检测到的纤铁矿由具有类似于纤铁矿的局部结构的纳米簇组成，类似于在天然絮凝物中发现的纤铁矿。总的来说，我们的结果表明，水铁矿-OM中的C含量会与Fe（II）水溶液反应期间，对铁矿物质转化和铁原子交换的程度和途径产生强烈影响。

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  • 来源
    《Environmental Science & Technology》 |2018年第21期|12316-12326|共11页
  • 作者

    ThomasArrigo Laurel K.; Byrne James M.; Kappler Andreas; Kretzschmar Ruben;

  • 作者单位

    Swiss Fed Inst Technol, Dept Environm Syst Sci, Inst Biogeochem & Pollutant Dynam, Soil Chem Grp,CHN, Univ Str 16, CH-8092 Zurich, Switzerland;

    Univ Tubingen, Ctr Appl Geosci ZAG, Geomicrobiol Grp, Sigwartstr 10, D-72076 Tubingen, Germany;

  • 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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