Experimental and molecular dynamics study on anion diffusion in organically modified bentonite
Experimental and molecular dynamics study on anion diffusion in organically modified bentonite
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DOI：
10.1016/j.clay.2015.11.026
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发表时间：
2016-02-01
影响因子：
5.6
通讯作者：
Dultz, S.
中科院分区：
文献类型：
--
作者：
Schampera, B.;Solc, R.;Dultz, S.
该工作提出了以硝酸盐作为有机改性膨润土中的模型探针的阴离子扩散的实验和分子模型研究。制备了具有不同负载量的两种阳离子十六烷基三甲基铵（HDTMA(+)）和十六烷基吡啶鎓（HDPy+）的有机粘土样品。 NO3- 在有机膨润土界面区域的扩散率受到有机涂层堆积密度的强烈影响。穿透扩散实验证实，有机粘土的缓凝能力随着粘土表面两种有机阳离子数量的增加而增加。 HDTMA(+)- 和 HDPy+-膨润土中观察到的 NO3- 扩散处于相似的范围内。此外，在 HDTMA(+)- 和 HDPy+-蒙脱土模型上进行的经典分子动力学研究解释了硝酸根阴离子在有机粘土-水界面扩散过程的分子机制。分子模拟显示了实验中观察到的NO3-扩散系数对表面有机阳离子含量的依赖性趋势。计算解释了有机阳离子在表面上的排列方式，并揭示了有机阳离子带正电的头基在降低硝酸根离子扩散性方面发挥着关键作用。 (C) 2015 Elsevier B.V. 保留所有权利。
The work presents experimental and molecular modeling study of the anion diffusion with nitrate as a model probe in the organically modified bentonite. Organoclay samples with different loadings of the two cations Hexadecyltrimethylammonium (HDTMA(+)) and Hexadecylpyridinium (HDPy+) were prepared. The diffusivity of NO3- in the interfacial area of the organo-bentonite is strongly affected by the packing density of the organic coating. Through-diffusion experiments verified that the retardation capacity of the organoclays increases with the increasing amount of both organic cations on the clay surface. Observed NO3- diffusion in HDTMA(+)- and HDPy+-bentonite is in a similar range. Further, classical molecular dynamics studies, performed on sets of HDTMA(+)- and HDPy+-montmorillonite models, explained a molecular mechanism of the diffusion process of the nitrate anion at the organoclay-water interface. The molecular simulations showed comparable trends of the dependence of the NO3- diffusion coefficient on the content of organic cations on the surface as observed in experiment. Calculations explained how the organic cations are arranged on the surface and revealed that the positively charged head groups of the organic cations play a key role in the decreasing of the diffusivity of nitrate ions. (C) 2015 Elsevier B.V. All rights reserved.