Diffusiophoretic and diffusioosmotic velocities for mixtures of valence-asymmetric electrolytes
Diffusiophoretic and diffusioosmotic velocities for mixtures of valence-asymmetric electrolytes
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DOI：
10.1103/physrevfluids.4.043702
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发表时间：
2019-04-12
影响因子：
2.7
通讯作者：
Stone, Howard A.
中科院分区：
文献类型：
--
作者：
Gupta, Ankur;Rallabandi, Bhargav;Stone, Howard A.
扩散电泳和扩散渗透是电动现象，其中由于离子的浓度梯度，在带电表面和周围电解质之间引起相对运动。在文献中，表面和电解质之间的相对速度已经推导出的价对称（z：z）电解质。在这篇文章中，我们重新制定的控制方程在一个方便的形式的基础上，系统的推广的非线性泊松-玻尔兹曼方程的限制薄双层，这使我们能够推导出结果的diffusiophoretic和diffusiosmotic速度的混合物的电解质的一般组合的阳离子和阴离子价。我们发现，相对运动显着依赖于离子价态。我们还提供了分析近似的diffusiophoretic和diffusiosmotic速度，并讨论其准确性和适用性。此外，我们列出了一些常见的情况下，这突出了阳离子和阴离子价的不对称性的重要性diffusiphoretic速度。最后，我们讨论了我们的假设的有效性和影响的重要性，如有限的离子尺寸，介电衰减，和典型的实验条件下的表面传导。
Diffusiophoresis and diffusioosmosis are electrokinetic phenomena where relative motion is induced between a charged surface and a surrounding electrolyte due to a concentration gradient of ions. In the literature, a relative velocity between a surface and the electrolyte has been derived for a valence-symmetric (z:z) electrolyte. In this article, we reformulate the governing equations in a convenient form based on a systematic generalization of the nonlinear Poisson-Boltzmann equations in the limit of a thin double layer, which allows us to derive results for diffusiophoretic and diffusioosmotic velocities for a mixture of electrolytes with a general combination of cation and anion valences. We find that the relative motion depends significantly on ion valences. We also provide analytical approximations for the diffusiophoretic and diffusioosmotic velocities and discuss their accuracy and applicability. Further, we tabulate diffusiphoretic velocities for some common cases, which highlights the importance of asymmetry in cation and anion valences. Finally, we discuss the validity of our assumptions and the importance of effects such as finite ion size, dielectric decrement, and surface conduction for typical experimental conditions.