Sugar-influenced water diffusion, interaction, and retention in clay interlayer nanopores probed by theoretical simulations and experimental spectroscopies
Sugar-influenced water diffusion, interaction, and retention in clay interlayer nanopores probed by theoretical simulations and experimental spectroscopies
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DOI：
10.1016/j.advwatres.2017.03.014
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发表时间：
2017-08-01
影响因子：
4.7
通讯作者：
Aoki, Thalia G.
中科院分区：
文献类型：
--
作者：
Aristilde, Ludmilla;Galdi, Stephen M.;Aoki, Thalia G.
了解粘土纳米孔的流体动力学对于深入了解天然和工程土壤中水、养分和污染物的捕获非常重要。先前的研究主要集中在蒙脱石粘土的阳离子饱和层间纳米孔中阳离子和水分子的层间组织和分子扩散系数（D）。然而，人们对这些层间动态特性如何受到土壤环境中普遍存在的小有机化合物（如糖）的影响知之甚少。在这里，我们探讨了葡萄糖分子对蒙脱土层间性能的影响。分子动力学模拟揭示了吸附物质层间组织的重组。水-水相互作用被葡萄糖-水氢键相互作用破坏。葡萄糖填充的纳米孔的“脱水”导致Na溶剂化壳层耗尽，从而导致Na离子（作为内球复合物）和剩余的水合水分子在矿物表面积累。这种积累导致 D-Na 和 D-水的减少。此外，随着葡萄糖含量的增加，D-葡萄糖的减少可以通过葡萄糖分子聚集成氢键结合到纳米孔两壁矿物表面的有机簇来解释。实验核磁共振和X射线衍射数据与理论预测一致。与不含葡萄糖的粘土夹层相比，Na-23 核磁共振谱中强度的增加和新峰证实了 Na 的固定随着葡萄糖含量的增加而增加。而且，X 射线衍射数据表明，暴露于水分减少的条件下，葡萄糖填充的夹层的塌陷减少，从而导致水合粘土纳米孔的维持。理论和实验结果的结合揭示了分子到纳米尺度的机制，这些机制控制着富含糖的粘土纳米孔内水分子和溶质的增强捕获。 (C) 2017 Elsevier Ltd. 保留所有权利。
Understanding the hydrodynamics in clay nanopores is important for gaining insights into the trapping of water, nutrients, and contaminants in natural and engineered soils. Previous investigations have focused on the interlayer organization and molecular diffusion coefficients (D) of cations and water molecules in cation-saturated interlayer nanopores of smectite clays. Little is known, however, about how these interlayer dynamic properties are influenced by the ubiquitous presence of small organic compounds such as sugars in the soil environment. Here we probed the effects of glucose molecules on montmorillonite interlayer properties. Molecular dynamics simulations revealed re-structuring of the interlayer organization of the adsorptive species. Water-water interactions were disrupted by glucose-water H-bonding interactions. "Dehydration" of the glucose-populated nanopore led to depletion in the Na solvation shell, which resulted in the accumulation of both Na ions (as inner-sphere complexes) and remaining hydrated water molecules at the mineral surface. This accumulation led to a decrease in both D-Na and D-water. In addition, the reduction in D-glucose as a function of increasing glucose content can be explained by the aggregation of glucose molecules into organic clusters H-bonded to the mineral surface on both walls of the nanopore. Experimental nuclear magnetic resonance and X-ray diffraction data were consistent with the theoretical predictions. Compared to clay interlayers devoid of glucose, increased intensities and new peaks in the Na-23 nuclear magnetic resonance spectra confirmed increasing immobilization of Na as a function of increasing glucose content. And, the X-ray diffraction data indicated a reduced collapse of glucose-populated interlayers exposed to decreasing moisture conditions, which led to the maintenance of hydrated clay nanopores. The coupling of theoretical and experimental findings sheds light on the molecular to nanoscale mechanisms that control the enhanced trapping of water molecules and solutes within sugar-enriched clay nanopores. (C) 2017 Elsevier Ltd. All rights reserved.