Natural Organic Matter (NOM) Imparts Molecular-Weight-Dependent Steric Stabilization or Electrostatic Destabilization to Ferrihydrite Nanoparticles
Natural Organic Matter (NOM) Imparts Molecular-Weight-Dependent Steric Stabilization or Electrostatic Destabilization to Ferrihydrite Nanoparticles
复制标题
天然有机物 (NOM) 赋予水铁矿纳米颗粒分子量依赖性的空间稳定性或静电去稳定性
DOI：
10.1021/acs.est.0c01189
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发表时间：
2020-06-02
影响因子：
11.4
通讯作者：
Hu, Yandi
中科院分区：
文献类型：
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作者：
Li, Zhixiong;Shakiba, Sheyda;Hu, Yandi
水铁矿纳米颗粒（Fh NP）在自然环境中无处不在。然而，在存在异质天然有机物（NOM）混合物的情况下，它们的胶体稳定性、归宿和运输行为很难预测。在这里，我们研究了暴露于不同分子量（MW）的 NOM 组分中的 Fh NP 的吸附和聚集行为。 MW < 3 kDa 的 NOM 组分会破坏纳米颗粒的稳定性，即使在高 C/Fe 质量比下也会加速聚集，而较高 MW 的 NOM 组分会随着 MW 和 C/Fe 比例的增加而提供更好的胶体稳定性。尽管本体（溶解的）NOM 组分的官能团组成存在差异，但所有 NOM 组分在 NP 上产生相似的吸附层组成，表明化学性质对独特聚集行为的贡献最小。相反，较高分子量部分的较高吸附质量和较大尺寸是通过空间排斥稳定纳米颗粒的关键因素，而最低分子量部分具有较低的吸附质量，并且当纳米颗粒带正电时无法对抗静电斑块电荷吸引力。这种机制的理解有助于我们预测 Fh NP 和相关污染物在具有不同 NOM 成分的自然环境中的运输和归宿。
Ferrihydrite nanoparticles (Fh NPs) are ubiquitous in natural environments. However, their colloidal stability, and fate and transport behavior are difficult to predict in the presence of heterogeneous natural organic matter (NOM) mixtures. Here, we investigated the adsorption and aggregation behavior of Fh NPs exposed to NOM fractions with different molecular weights (MW). The NOM fraction with MW < 3 kDa destabilized the NPs, resulting in accelerated aggregation even at high C/Fe mass ratios, whereas higher MW NOM fractions imparted better colloidal stability with increasing MW and C/Fe ratio. Despite differences in the functional group composition of the bulk (dissolved) NOM fractions, all NOM fractions produced similar adsorbed layer compositions on the NPs, suggesting minimal contribution of chemical properties to the distinctive aggregation behavior. Rather, the higher adsorbed mass and larger size of the higher MW fractions were key factors in stabilizing the NPs through steric repulsion, whereas the lowest MW fraction had low adsorbed mass and was unable to counter electrostatic patch-charge attraction when the NPs are positively charged. This mechanistic understanding helps us predict the transport and fate of Fh NPs and the associated contaminants in natural environments with varying NOM compositions.