用微扰理论状态方程计算电解质水溶液的活度系数

近年来,电解质溶液理论的研究日益活跃^[1]。因为理论模型能反映微观粒子参数与溶液结构和性质间的关系,参数物理意义明确,预测功能强。电解质溶液的原始模型中,忽略了离子－溶剂和溶剂－溶剂相互作用,而只考虑在溶剂平均场中离子之间的相互作用。这类模型不能反映溶液的本质和溶质－溶剂间的真实相互作用,因此很难推广到混合溶剂电解质溶液。用微扰理论研究电解质溶液的状态方程已经取得很大进展^[2]。硬球离子流体^[3]和离子－偶极^[4]模型流体的微扰理论处理结果已经成功地用于构筑实际电解质溶液的状态方程^[5]。作者采用微扰理论研究了电解质溶液的密度性质^[6],本文将进一步研究活度系数的计算问题。     

电解质NRTL模型的发展及应用

综述了电解质NRTL模型从最初的用于处理单一电解质、单一溶剂体系的两贡献模型发展成为能处理多电解质组分、混合溶剂体系的热力学模型，介绍了模型在电解质溶液相平衡计算中的应用。最后指出了此模型的优缺点和模型参数的发展方向。     

电动势法确定水-丙酮-氯化钠-氯化镁体系热力学性质

采用自行设计的无液体接界电池测定了多组分电解质在水溶液和混合溶剂中不同组成时电池的电动势.利用Pitzer模型拟合实验数据,获得电池的标准电动势E(○)及电解质的活度系数.此外,计算了电解质从纯水到混合溶剂中的迁移吉布斯函数,求得了Pitzer模型的计算参数.获得了NaCl和MgCl2混合电解质的混合参数θ(NaCl)...     

一种预测电解质溶液密度的新方法

根据对应状态原理的基本思想本文提出了一种预测电解质溶液密度的新方法。以CaCl2 溶液作为参考流体 ,本文得到了溶液渗透压和溶剂水的表观摩尔体积的定量关系。假定该关系对所有电解质水溶液都是适用的 ,则由离子半径和溶液组成 ,就可以计算单一电解质溶液和预测混合电解质溶液在全浓度和 2 73K～ 373K范围内的密度。模型的可靠性通过 30个二元电解质溶液在 2 98 1 5K和 1 1个单一电解质溶液在 2 73K～ 373 1 5K范围内密度的预测进行了检验。采用与温度和浓度无关的离子半径的优化值 ,本文对密度预测的总平均相对偏差小于 1 %。该方法公式简单 ,计算精度可以满足工业设计计算的要求     

新的电解质混合溶剂体系的Gibbs过量自由能模型

提出一个新的电解质混合溶剂体系的Ｇｉｂｂｓ过量自由能模型。该模型由三项组成：ＤｅｂｙｅＨｕｃｋｅｌ项、溶剂－溶剂相互作用项和溶剂化作用项。其表达形式简洁、满足热力学一致性，仅从２９８．１５Ｋ下关联的二元参数就可以预测单一电解质混合溶剂体系的热力学性质，用以熔融盐为标准态扩展到混合溶剂体系的Ｄｅｂｙｅ－Ｈｕｃｋｅｌ项，能正确地预测此类体系的盐析效应。     

混合电解质单个离子活度系数和平均活度系数的近似计算

水处理过程中所遇到的混合电解质溶液绝大多数离子强度都不高。本文简化了混合电解质溶液中单个离子活度系数和电解质平均离子活度系数的Pitzer计算式。所得简化式可方便地直接用于实际混合电解质溶液体系中活度系数的近似计算。     

环保型准固态电解质的制备及在染料敏化太阳电池中的应用

本文介绍了一种制备染料敏化太阳电池(DSC)准固态电解质的新方法——混合溶剂法.该方法具有制作工艺简单、所用溶剂对人及环境无污染等优点.将混合溶剂法制备的准固态电解质应用于太阳电池,并系统研究了电解质组成及环境温度对电解质及其DSC性能的影响规律.     

镁二次电池研究评述

镁二次电池是有望用于电动汽车的“绿色”蓄电池 ,比锂离子二次电池具有更多优点。组成镁二次电池的核心是镁负极、电解质溶液及能嵌入Mg2 +的正极材料。能用于镁二次电池的电解质溶液仅有RMgX衍生物的醚溶液 ;在可选的Co3 O4、V2 O5和Mo3 O4正极材料中Mo3 O4最好。镁负极由复杂的吸收过程控制 ,被吸收的组分主要取决于所用电解质。镁电极的循环效率由镁沉积的形态决定。指出改进电解质溶液如用混合溶剂、混合电解质和支持电解质及增大阴离子等 ,改进正极如掺杂 ,可改进镁二次电池的性能。     

NaCl在混合溶剂(DMF-H2O)中热力学性质的研究

应用钠离子选择性电极和Ag-AgCl电极组成可逆电池,通过测定电池的电动势,应用Debye-Hückel极限公式,求得不同温度下NaCl在混合溶剂(DMF-H2O)中的活度系数(γ±),计算了NaCl在混合溶剂(DMF-H2O)中的相对偏摩尔自由能,并据电解质溶液的溶剂化理论对NaCl溶液的活度系数及相对偏摩尔自由能的变化规律进行了初步的讨论。     

钠钙氯化物在乳糖水中热力学性质的确定

在298.15 K时利用电动势法确定四元体系氯化钠-氯化钙-乳糖-水不同组成(乳糖质量分数分别为0,5%,10%和15%)时的热力学性质。利用Pitzer离子作用模型拟合实验数据,获得了氯化钠和氯化钙在乳糖水混合溶剂中的Pitzer模型参数。进一步计算了氯化钠和氯化钙从纯水到乳糖水混合溶剂中的迁移吉布斯函数。获得了氯化钠和氯化钙混合电解质在乳糖水混合溶剂中的混合参数θ(Na Ca)和ψ(Na Ca Cl)。计算了298.15 K时四元体系中氯化钠和氯化钙的平均离子活度系数。结果发现:利用Pitzer高阶静电作用模型计算混合电解质在混合溶剂中的平均离子活度系数,能获得较为满意的结果。     

Correlation of the mean activity coefficient of aqueous electrolyte solutions using an equation of state

Accurate calculation of thermodynamic properties of electrolyte solution is essential in the design and optimization of many processes in chemical industries.A new electrolyte equation of state is developed for aqueous electrolyte solutions.The Carnahan–Starling repulsive model and an attractive term based on square-well potential are adopted to represent the short range interaction of ionic and molecular species in the new electrolyte EOS.The long range interaction of ionic species is expressed by a simplified version of Mean Spherical Approximation theory(MSA).The new equation of state also contains a Born term for charging free energy of ions.Three adjustable parameters of new e EOS per each electrolyte solution are size parameter,square-well potential depth and square-well potential interaction range.The new e EOS is applied for correlation of mean activity coefficient and prediction of osmotic coefficient of various strong aqueous electrolyte solutions at 25 °C and 0.1 MPa.In addition,the extension of the new e EOS for correlation of mean activity coefficient and solution density of a few aqueous electrolytes at temperature range of 0 to 100 °C is carried out.     

Association-based activity coefficient model for electrolyte solutions

This work presents an association-based activity coefficient model that explicitly considers the solution nonideality due to associations among ions and solvent species. Built upon the electrolyte nonrandom two-liquid (eNRTL) model, the model greatly improves the accuracy of eNRTL model for strongly associating electrolyte solutions due to presence of ionic species with high surface charge density. The model successfully correlates mean ionic activity coefficients of 46 aqueous single-salt systems from 10 cations and 5 anions at 298.15 K up to their solubility limits. With the ion-specific association parameters identified, the model accurately predicts activity and osmotic coefficients for aqueous mixed-salt systems at 298.15 K. The temperature dependence of the model results has also been examined at 273–373 K. With superior accuracy over a wide range of concentration and temperature, the model represents a major advancement over eNRTL model and has a great potential to be a next-generation model for electrolyte solutions.     

Generalized LIQUAC model for the single‐ and mixed‐solvent strong electrolyte systems

A generalized strong electrolyte LIQUAC model is presented to describe the vapor–liquid equilibria, osmotic coefficients, mean ion activity coefficients, and solid–liquid equilibria for the single‐ and mixed‐solvent electrolyte systems over the entire concentration range from infinite dilution to saturated solutions. An appropriate reference state for the ions was first applied to test the capability of the model in simultaneously describing the mean ion activity coefficients and the solubility of a salt in a binary solvent mixture. The influence of salt on the vapor–liquid equilibrium behavior is predicted with the new correlated parameters. The generalized activity coefficient formulations are presented through the investigation of thermodynamic properties and phase phenomena in the single‐ and mixed‐solvent electrolyte systems. This work is a continuous study for the LIQUAC activity coefficient model. A reliable representation of the single‐ and mixed‐solvent salt solutions is obtained. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Modeling for mean ion activity coefficient of strong electrolyte system with new boundary conditions and ion-size parameters

A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson–Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye–Hückel (DH) limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1:1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol-vents are predicted with the new equations.     

Peculiarities of the Thermodynamics of Electrolyte Solutions: A Critical Discussion

Differences in the thermodynamic treatment of electrolyte and nonelectrolyte solutions are highlighted. The relations between expressions for concentrations are stated and the need to consider the presence of ions is emphasized. Examples are presented to show that the activity coefficient of a particular ion depends on the nature of the other ions in the solution. An overview is given of the state of development — and shortcomings — of methods to measure the activity coefficient of individual ions. Pitfalls in the use of polynomials to evaluate the mean ionic activity from measurements of the activity of the solvent are emphasized and solutions proposed. The interpretation of the mean ionic activity coefficient of weak electrolytes is discussed. The relation between the excess Gibbs energy and the activity coefficients of the species in solutions is reviewed and the relation between the McMillan‐Mayer and Lewis‐Randall frameworks is commented. An abstract of the basic equations for electrolyte solution thermodynamics is appended.     

基于微扰理论和平均球近似的强电解质水溶液分子热力学模型

用平均球近似处理离子-离子间的静电相互作用,用微扰理论处理电解质溶液中各种粒子间的其他相互作用,建立了一个强电解质水溶液的分子热力学模型。该模型将阳离子直径作为唯一的可调参数,对52种1-1、1-2、2-1、2-2型强电解质水溶液离子的平均活度系数进行了关联,与现有模型比较,该模型形式相对简单,具有很好的适用性和满意的计算精度。     

平均球近似法计算电解质活度系数的研究(Ⅱ)——混合电解质水溶液

用(I)报中所得到的阳离子有效直径参数,用平均球近似(MSA)法,在不用混合参数的条件下,预测了32个混合电解质水溶液的离子平均活度系教.预测的Inγ_± 与实验值的平均标准偏差为0.0113.文中还用Pitzer方程作了计算.结果表明本文预测结果比无混合参数的Pitzer方程好得多,接近于带混合参数的Pitzer方程的关联结果,作者还分别预测了各温度下4个混合电解质水溶液饱和浓度时的活度系数,结果令人满意.     

COSMO-RS-PDHS: A new predictive model for aqueous electrolytes solutions

This work introduces a new tool able to predict water activities and activity coefficients of electrolytes in binary {water–electrolyte} systems. In mixtures containing electrolytes, the system is characterized by the presence of both molecular and ionic species, resulting in three different types of interactions: ion–ion, molecule–molecule and ion–molecule.Ion–ion interactions are governed by electrostatic forces between ions that have a much longer range than other intermolecular forces. The long range interactions between ions are taken in account by the Pitzer term based on the Debye–Hückel theory.Molecule–molecule and ion–molecule interaction forces are known to be short-range in nature. To determine short range mean activity coefficients of salts in {water–electrolyte} binary mixtures, a chemical treatment of ions solvation is combined with the predictive power of the COSMO-RS model. The main originality of this work resides in this chemical treatment model that provides the thermodynamic relations which enable to determine the equilibrium properties of the real solution {water–salt}, knowing those of a hypothetical mixture containing water and hydrated clusters.The resulting model called “COSMO-RS-PDHS” predicts results that are in good agreement with experimental data.     

Revisiting electrolyte thermodynamic models: Insights from molecular simulations

Pitzer and electrolyte nonrandom two‐liquid (eNRTL) models are the two most widely used electrolyte thermodynamic models. For aqueous sodium chloride (NaCl) solution, both models correlate the experimental mean ionic activity coefficient (γ_±) data satisfactorily up to salt saturation concentration, that is, ionic strength around 6 m. However, beyond 6 m, the model extrapolations deviate significantly and diverge from each other. We examine this divergence by calculating the mean ionic activity coefficient over a wide range of concentration based on molecular simulations and Kirkwood–Buff theory. The asymptotic behavior of the activity coefficient predicted by the eNRTL model is consistent with the molecular simulation results and supersaturation experimental data. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3728–3734, 2018