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混合电解质溶液中考虑介电饱和度的表面电位评估原理
邹温馨1, 彭 景1, 修维宁2, 刘新敏*1
1.西南大学资源与环境学院,土壤多尺度界面过程与调控重庆市重点实验室,重庆 400715;2.重庆市农业科学院农业工程研究所,重庆 401329
摘要:
基于非线性泊松-玻尔兹曼方程,推导了混合电解质溶液中考虑介电饱和度的表面电位的解析表达式. 近似解析解和精确数值解计算出的表面电位在很大范围的电荷密度和离子强度条件下均具有很好的一致性. 当表面电荷密度大于0.30 C/m2 时,介电饱和度对表面电位的影响变得尤为重要;当表面电荷密度小于0.30 C/m2时,可忽略介电饱和度的影响,即基于经典泊松-玻尔兹曼方程可获得有效的表面电位解析模型. 因此,0.3 C/m2可作为是否考虑介电饱和度的颗粒临界表面电荷密度值. 在低表面电荷密度时,考虑介质饱和度的表面电位解析模型可自然回归到经典泊松-玻尔兹曼理论的结果,得到的表面电位可以正确地预测一价和二价反离子之间的吸附选择性.
关键词:  介电性质,双电层,表面电荷,胶体颗粒
DOI:10.1063/1674-0068/cjcp1907132
分类号:
基金项目:
Principles of Surface Potential Estimation in Mixed Electrolyte Solutions: Taking into Account Dielectric Saturation
Wen-xin Zou1, Jing Peng1, Wei-ning Xiu2, Xin-min Liu*1
1.Chongqing key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing 400715, China;2.Institute of Agricultural Engineering, Chongqing Academy of Agricultural Sciences, Chongqing 401329, China
Abstract:
The dielectric properties between in-particle/water interface and bulk solution are signif-icantly different, which are ignored in the theories of surface potential estimation. The analytical expressions of surface potential considering the dielectric saturation were derived in mixed electrolytes based on the nonlinear Poisson-Boltzmann equation. The surface potentials calculated from the approximate analytical and exact numerical solutions agreed with each other for a wide range of surface charge densities and ion concentrations. The effects of dielectric saturation became important for surface charge densities larger than 0.30 C/m2. The analytical models of surface potential in different mixed electrolytes were valid based on original Poisson-Boltzmann equation for surface charge densities smaller than 0.30 C/m2. The analytical model of surface potential considering the dielectric saturation for low surface charge density can return to the result of classical Poisson-Boltzmann theory. The obtained surface potential in this study can correctly predict the adsorption selectivity between monovalent and bivalent counterions.
Key words:  Dielectric property, Electrical double layer, Surface charge, Colloid particle
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