聚电解质溶液分子热力学模型

MOLECULAR THERMODYNAMIC MODEL OF POLYELECTROLYTE SOLUTIONS

链状聚电解质由于是长链大分子又有很高的电荷密度,其溶液即使在极低的浓度下仍具有很强的负偏差,与Debye-Huckel理论预测的结果相去甚远。工程上使用的Manning模型认为聚离子的电荷密度有一临界值,当超过临界值时,反离子即凝聚在聚离子表面使其实际电荷密度降至临界值。Nagvekar等在该模型的基础上引入NRTL方程,以计及短程相互作用的贡献。Manning等的方法虽然有一定的物理意义,但临界值的确定缺乏可靠的根据。

The method of numerical solution of Poisson - Boltzmann equation for polyelec-trolyte solutions containing simple salt presented by Vink is used to calculate the distribution of electric potential around the polyion in cylindrical cell model. Combining with the thermodynamics of polyelectrolyte solution, the activity coefficients of counterion, coion and polyion are obtained from those electric potential data. The osmotic coefficients of solvent are also obtained. These numerical data are correlated with general function of parameter of electric charge density ε parameter of polyelectrolyte concentration X and the ratio of concentrations of simple salt and polyelectrolyte f. The mean activity coefficients of simple salt calculated by this work for systems of NaPP - NaCl, NaPP - NaBr and Napp - Nal are agreement with the experimental data, better than that predicted by Manning's model.