Chen SB
Department of Chemical Engineering, National University of Singapore, 119260, Singapore
J Colloid Interface Sci. 1998 Sep 15;205(2):354-364. doi: 10.1006/jcis.1998.5625.
Electrostatic interaction and hindered diffusion of ion-penetrable spheres in a slit pore filled with an electrolyte solution are investigated theoretically. The concentration of the particles is assumed sufficiently low so that the interactions between the particles can be neglected. The slit pore comprises two parallel infinite plates, which can be either permeable or impermeable to the electrolyte. The electrostatic interaction energy is obtained analytically by adopting an integral of Green's function and an image method. It is found that for impermeable plates having constant surface charge densities, the electrostatic interaction can be attractive or repulsive for a particle with charge of opposite sign, depending on the relative magnitudes of charge densities and particle location. Similar behavior is predicted for plates with constant surface potential and a particle with charge of like sign. The interaction energy is used to determine the spatial distribution of the particle in the pore and the partition coefficient, and then to calculate the average and apparent diffusivities. The average diffusivity calculated from the average mobility in the pore is always smaller than that in the bulk solution because of greater drag the particle experiences in the presence of the plates. This mean diffusivity is larger than that in the corresponding neutral system for repulsive electrostatic interaction, but becomes smaller for attractive interaction. The apparent diffusivity defined from the flux based on the bulk concentration of the particle depends strongly on the ion concentration, as does the partition coefficient when the double layer is sufficiently thick. Copyright 1998 Academic Press.
从理论上研究了离子可穿透球体在充满电解质溶液的狭缝孔隙中的静电相互作用和受阻扩散。假设颗粒浓度足够低，从而可以忽略颗粒之间的相互作用。狭缝孔隙由两个平行的无限大平板组成，这两个平板对电解质可以是可渗透的或不可渗透的。通过采用格林函数积分和镜像法解析地获得了静电相互作用能。结果发现，对于具有恒定表面电荷密度的不可渗透平板，对于带相反电荷的颗粒，静电相互作用可以是吸引的或排斥的，这取决于电荷密度的相对大小和颗粒位置。对于具有恒定表面电势的平板和带相同电荷的颗粒，预测了类似的行为。相互作用能用于确定颗粒在孔隙中的空间分布和分配系数，然后计算平均扩散系数和表观扩散系数。由于颗粒在平板存在下受到更大的阻力，从孔隙中的平均迁移率计算出的平均扩散系数总是小于本体溶液中的平均扩散系数。对于排斥性静电相互作用，这个平均扩散系数大于相应中性体系中的平均扩散系数，但对于吸引性相互作用则变小。基于颗粒本体浓度的通量定义的表观扩散系数强烈依赖于离子浓度，当双电层足够厚时，分配系数也是如此。版权所有1998年学术出版社。
