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Defining silica–water interfacial chemistry under nanoconfinement using lanthanides
Environmental Science: Nano ( IF 7.3 ) Pub Date : 2021-1-11 , DOI: 10.1039/d0en00971g
Anastasia G. Ilgen 1, 2, 3, 4 , Nadine Kabengi 4, 5, 6, 7 , Kevin Leung 1, 2, 3, 4 , Poorandokht Ilani-Kashkouli 4, 5, 6, 7 , Andrew W. Knight 1, 3, 4, 8 , Lourdes Loera 1, 2, 3, 4
Affiliation  

A quarter of Earth's land surface is covered by porous sedimentary silicate rocks, so silica–water interfaces are critical to the fate and transport of chemical species on a global-scale. However, while the physiochemical properties of unconfined silica–water interfaces are understood reasonably well, these properties have proven to be unpredictable when the interface is confined in nanometer-scale pores within sedimentary rocks. For example, the existing theories struggle to quantitatively predict how the energetics of adsorption reactions and the coordination environment of adsorbed species shift due to nanoconfinement of an interface. Here, we utilized gradual and known variations in the properties of trivalent lanthanide ions to decipher the chemical interactions that cause the nanoconfinement effects on chemistry at the silica–water interfaces. We discovered that the lanthanide's free energy of hydration (ΔGhydr) is a descriptor that can be used to predict the extent to which nanoconfinement will change the thermodynamics and products of interfacial reactions. We show that nanoconfinement promotes inner-sphere complexation between lanthanides and silica surface, as well as the formation of polymeric surface species. In nanoconfined domains lanthanide's ΔGhydr becomes less negative, reducing the energy required to dehydrate the ion during the formation of an inner-sphere surface complex. These nanoconfinement effects on chemistry become more pronounced for ions with lower hydration free energies.

中文翻译:

使用镧系元素定义纳米约束下的二氧化硅-水界面化学

地球陆地表面的四分之一被多孔的沉积硅酸盐岩石覆盖,因此二氧化硅与水的界面对于全球范围内化学物种的命运和运输至关重要。然而,尽管人们对非限制性的二氧化硅-水界面的理化性质有充分的了解,但是当界面局限于沉积岩中的纳米级孔隙中时,这些性质是无法预测的。例如,现有理论难以定量地预测由于界面的纳米约束,吸附反应的能量和吸附物质的配位环境如何变化。这里,我们利用三价镧系元素离子的特性的逐步已知变化来解释化学相互作用,这些相互作用导致纳米约束作用对二氧化硅-水界面的化学作用。我们发现镧系元素的水合自由能(ΔG hydr)是一个描述符,可用于预测纳米约束作用在多大程度上改变热力学和界面反应产物。我们表明,纳米约束促进了镧系元素和二氧化硅表面之间的内球络合,以及聚合物表面物种的形成。在纳米约束域中,镧系元素的ΔG hydr变得越来越负,从而减少了在形成内球表面复合物期间使离子脱水所需的能量。对于水合自由能较低的离子,这些对化学的纳米限制作用更加明显。
更新日期:2021-01-18
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