黏土颗粒扩散双电层影响因素分析

Analysis of influencing factors of clay particle diffusion in electric double layer

双电层结构对研究黏土力学特性、冻土水分迁移等具有重要意义。为了探究不同影响因素对黏土颗粒扩散双电层电势分布的影响,借鉴Gouy-Chapman-Stern双电层理论,基于Nernst-Planck方程和Poisson-Boltzmann方程,利用数值软件COMSOL定量分析了温度、浓度、颗粒尺寸、颗粒形状以及溶液相对介电常数对扩散双电层电势分布的影响规律。研究表明:温度对电势分布的影响不明显,但随着温度以及Stern层厚度增加,黏土颗粒表面电势和Stern电势均增加;而随着溶液浓度以及相对介电常数减小,表面电势值增加;在矿物成分、表面电荷密度以及颗粒形状确定的情况下,尺寸对于扩散双电层电势分布的影响不显著;但颗粒的不规则形状对电势分布的影响较为明显,当颗粒形状存在夹角时,夹角处的表面电势远大于其他位置,且夹角越小,夹角处表面电势值越大。

The electric double layer structure is of great significance for studying the mechanical properties of clay and the water migration of frozen soil.In order to explore the influence of different influencing factors on the potential distribution of the diffusion electric double layer of clay particles,referring to the Gouy-ChapmanStern electric double layer theory,based on the Nernst-Planck equation and the Poisson-Boltzmann equation,the numerical software COMSOL was used to quantitatively analyze the temperature,concentration,particle size,particle shape and the relative dielectric constant of the solution on the potential distribution of the diffusion electric double layer.The research shows that the effect of temperature on the potential distribution is not obvious,but with the increase of temperature and the thickness of the Stern layer,the surface potential and Stern potential of clay particles both increase;and as the solution concentration and relative permittivity decrease,the surface potential value increases;when the mineral composition,surface charge density and particle shape are determined,the effect of size on the potential distribution of the diffusion electric double layer is not significant;however,the irregular shape of the particles has an obvious effect on the potential distribution,when the particle shape has an included angle,the surface potential at the included angle is much larger than other positions,and the smaller the included angle,the larger the surface potential value at the included angle.