Density Prediction for Aqueous Multicomponent Solutions Obeying Isopiestic Relation and Isopycnotic Mixing Rule

The density predictive method based on isopiestic relation has been revised. The accuracy of density prediction based on the isopiestic mixing rule has been compared with that based on the isopycnotic mixing rule on ten aqueous ternary electrolyte systems, one quaternary electrolyte system, and one aqueous ternary nonelectrolyte system at 25°C. Of the ten ternary electrolyte systems, five systems show better predictive accuracy by the isopycnotic method, two by isopiestic relation, and three systems show comparable results. For the aqueous quaternary electrolyte and ternary nonelectrolyte systems, the isopycnotic method gives better predictive accuracy. The overall average error of density prediction based on isopiestic mixing rule is 0.00031, while that based on isopycnotic mixing rule is 0.00017.     

Flow of Multicomponent Electrolyte Solutions through Narrow Pores of Nanofiltration Membranes

The slow flow of a multicomponent electrolyte solution in a narrow pore of a nanofiltration membrane is considered. The well-known semiempirical method of subdivision of electrical potential into quasi-equilibrium and streaming parts and the definition of streaming concentrations and pressure are discussed. The usefulness of this tool for solving the electrohydrodynamic equations is shown and justified: the use of a small parameter enables a system of electrohydrodynamic partial differential equations to be reduced to a system of ordinary differential equations for streaming functions. Boundary conditions for streaming functions at both the capillary inlet and outlet are derived. The proposed model is developed for the flow of a multicomponent electrolyte solution with an arbitrary number of ions. This is coupled with (i) the introduction of specific interactions between all ions and the pore wall and (ii) the inclusion of the dissociation of water in both conservation and transport equations. Effective distribution coefficients of ions are introduced that are functions of both the specific interaction potentials and the surface potential of the nanofiltration membrane material. The axial dependency of surface potential is expressed by the use of a charge regulation model from which the discontinuity in electric potential and ion pore concentrations at the pore inlet and outlet can be described.A relation between the frequently used capillary and homogeneous models of nanofiltration membranes is developed. An example of application of the homogeneous model for interpretation of experimental data on nanofiltration separation of electrolyte solutions is presented, which shows a reasonable predictive ability for the homogeneous model.     

用Pitzer理论预测混合电解质溶液的偏摩尔体积

用Pitzer理论研究了混合电解质溶液的偏摩尔体积,建立了偏摩尔体积的预测方法,并利用所得电解质溶液的表观摩尔体积的Pitzer参数预测了HNO₃-UO₂(NO₃)₂-H₂O、KCl-Na₂SO₄-H₂O、NaCl-Na₂SO₄-H₂O、NaCl-CaCl₂-H₂O、KCl-CaCl₂-H₂O、KCl-MgCl₂-H₂O和KCl-NaBr-H₂O共7个系统4种类型的混合溶液的偏摩尔体积。     

An Investigation of Electrolyte Solutions Using a Simple Conductivity Apparatus

A student laboratory exercise in qualitative analysis has been developed to address student misconceptions associated with electrolyte and nonelectrolyte solutions. This exercise uses a previously reported, inexpensive, home-built conductivity meter to identify acid solutions. An additional short preparatory exercise provides students the opportunity to classify known solutions as strong, weak, or nonelectrolytes and gives students experience using a conductivity meter. These activities have been used successfully with both high school and introductory college chemistry students.     

纳滤膜对电解质溶液分离特性的理论研究(II): 混合电解质溶液

假定纳滤膜具有狭缝状孔, 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 用流体力学半径和无限稀释扩散系数表征了离子特性. 采用扩展Nernst-Planck方程、Donnan平衡模型和Poisson-Boltzmann理论描述了混合电解质溶液中离子在膜孔内的传递现象, 计算了三种商用纳滤膜(ESNA1-LF, ESNA1和LES90)对同阴离子、同阳离子和含四种离子的混合电解质体系中离子的截留率, 并与实验数据进行了比较. 计算结果表明, 电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对混合电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对含一价离子的混合电解质溶液通过纳滤膜的截留率计算结果比较准确, 但对高浓度或含高价离子的混合电解质溶液则偏差较大.     

Conductance of Electrolyte Solutions

The present article deals with methods and results of conductance studies with special reference to nonaqueous solvents, e.g. ethanol, dioxane, dimethylformamide, acetonitrile, nitromethane, and acetone, in some cases mixed with water, as well as NH₃, SO₂, I₂, etc. On the basis of a model in which the ions are represented as charged spheres and the solvent as a homogeneous isotropic medium, the conductance theory can (at least for low electrolyte concentrations) give a more or less complete representation of the problem. A new statistical treatment of the transport problem confirms important results of this representation. The present state of the investigation is finally outlined in a review of recent publications.     

Activity Coefficient Prediction for Binary and Ternary Aqueous Electrolyte Solutions at Different Temperatures and Concentrations

The mean spherical approximation (MSA) model, coupled with two hard sphere models, was used to predict the activity coefficients of mixtures of electrolyte solutions at different temperatures and concentrations. The models, namely the Ghotbi-Vera-MSA (GV-MSA) and Mansoori et al.-MSA (BMCSL-MSA), were directly used without introducing any new adjustable parameters for mixing of electrolyte solutions. In the correlation step, the anion diameters were considered to be constant, whereas the cation diameters were considered to be concentration dependent. The adjustable parameters were determined by fitting the models to the experimental mean ionic activity coefficients for single aqueous electrolytes at fixed temperature. The results showed that the studied models predict accurately the activity coefficients for single electrolyte aqueous solutions at different temperatures. In the systems of binary aqueous electrolyte solutions with a common anion, the GV-MSA model has slightly better accuracy in predicting the activity coefficients. Also, it was observed that the GV-MSA model can more accurately predict the activity coefficients for ternary electrolyte solutions with a common anion, especially at higher concentrations.     

Pitzer理论在含有机物的HCl-H2SO4-葡萄糖多组分电解质水溶液中的应用

在298.15K,以葡萄糖质量分数(0.15)恒定的葡萄糖+水混合物为溶剂,测定了电池Pt,H2(101.325kPa)|HCl(m1),H2SO4(m2),Glucose(x),H2O(1-x)|AgCl-Ag的电动势.用所得数据确定了H2SO4在该混合溶剂中的二级解离常数(K2)和一级介质效应.用带有中性分子与各离子相互作用项的Pitzer方程表示Owen定义的总介质效应可较好地处理含有机物的多组分电解质水溶液体系,并用此法处理了文献中HCl在各混合溶剂中的活度系数实验数据,确定了HCl与有机物分子相互作用的Pitzer参数.     

Excess Volume of Mixing of 1:1 Electrolyte Solutions at 298.15 K in the Aquo-1,4-Dioxane Mixed-Solvent System

Excess volumes of mixing for six possible binary combinations of solutions of NaCl, KCl, NaBr and KBr have been determined at constant ionic strengths of 1.000 and 2.000 mol-kg^{− 1} at 298.15 K using a dilatometer in the water + 1,4-dioxane mixed-solvent system. Pitzer’s ion-interaction model has been utilized to obtain binary and triplet interaction parameters, i.e., θ^V and ψ^V. The data were also analyzed by the Friedman Model and it is suggested that interactions between solvated ions are dictated not only by coulombic interactions but also by appreciable asymmetric effects. The data are dependent on the nature of the common ion and do not support Young’s cross-square rule. The deviation from the cross-square rule is considered to arise from preferential solvation of the ions and ion clusters in the mixed-solvent system as reflected by the appreciable contribution of triplet interactions.     

Electrochemically Controlled Ion‐exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

The electrochemically controlled ion‐exchange properties of multi‐wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion‐exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion‐exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structure of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X‐ray photoelectron spectroscopy (XPS).     

锂离子电池有机电解液研究

本文分析了影响有机电解液电导率的主要因素 ;总结了有机电解液的一般特点 ,从有机溶剂和电解质锂盐两个方面介绍了有机电解液的化学和电化学 ;概述了各常用有机溶剂的性质和近年来的研究状况 ;综述了有机电解液在电解质锂盐、有机溶剂和添加剂三个方面的研究进展 .文章最后对有机电解液研究的现状作了简要的评论     

A New Gibbs Energy Model for Obtaining Thermophysical Properties of Aqueous Electrolyte Solutions

In this paper, a new Gibbs energy model is proposed to study the thermophysical properties of aqueous electrolyte solutions at various temperatures. The proposed model assumes that the electrolytes completely dissociate in solution. The model also has two temperature-independent adjustable parameters that were regressed using experimental values of the mean ionic activity coefficients (MIAC) for 87 electrolyte solutions at 298.15 K. Results from the proposed model for the MIAC were compared with those obtained from the E-Wilson, E-NRTL, Pitzer and the E-UNIQUAC models, and the adjustable model parameters were used directly to predict the osmotic coefficients at this temperature. The results showed that the proposed model can accurately correlate the MIAC and predict the osmotic coefficients of the aqueous electrolyte solutions better on the average than the other models studied in this work at 298.15 K. Also, the proposed model was examined to study the osmotic coefficient and vapor pressure for a number of aqueous electrolyte solutions at high temperatures. It should be stated that in order to calculate the osmotic coefficients for the electrolyte solutions, the regressed values of parameters obtained for the vapor pressure at high temperatures were used directly. The results obtained for the osmotic coefficients and vapor pressures of electrolyte solutions indicate that good agreement is attained between the experimental data and the results of the proposed model. In order to unequivocally compare the results, the same experimental data and same minimization procedure were used for all of the studied models.     

在电解质溶液中测定非电解质溶解度的新方法

提出了一种可以同时测定电解质溶液中非电解质的溶解度和饱和溶液水活度的新方法。该法把等压平衡与传统化学分析统一起来,其优点是：（1）将多元饱和溶液中非电解质溶解度的测定转变为共存离子的溶度测定,避开了对非电解质难于进行精确化学分析的难题;（2）可以同时确定所测饱和体系的水活度。用该法测定了NaCl和KCl溶液中甘露醇的溶解度并与文献值进行了比较,结果表明二者符合得很好。     

Behavior of Tetrazole-containing Acrylic Hydrogels in Electrolyte Solutions

The influence of temperature, pH, and chemical composition of the medium on the equilibrium swelling of polymeric polyelectrolytic tetrazole-containing acrylic hydrogels was examined.     

The Solubility of Boric Acid in Electrolyte Solutions

The solubility of boric acid [B] in LiCl, NaCl, KCl, RbCl, and CsCl was determined as a function of ionic strength (0–6 mol ⋅ kg⁻¹) at 25 ^∘C. The results were examined using the Pitzer equation

A Model for the Shift of Isoelectric Points of Oxides in Concentrated and Mixed-Solvent Electrolyte Solutions

It is shown theoretically that the experimentally observed shifts of isoelectric points of various oxide surfaces toward more basic pH's in concentrated and mixed-solvent electrolyte solutions can be explained by a model previously used to predict the phenomenon of "coagulation zones" in the stability of colloids with adsorption layers of nonionic polymers. The model assumes the standard solvation energies of ions near a solid-liquid interface to be different from those in the bulk due to changes in the solvent structure. To reproduce the trends of experimental data in aqueous solutions, the solubilities of both cations and anions must be decreased, but for cations that must occur to a smaller extent. In mixed solvents a qualitative agreement with the experimental data is achieved by assuming that there is a water-enriched layer near the oxide surface. Copyright 2001 Academic Press.     

Viscosity Mixing Rules for Binary Systems Containing One Ionic Liquid

In this work the applicability of four of the most commonly used viscosity mixing rules to [ionic liquid (IL)+molecular solvent (MS)] systems is assessed. More than one hundred (IL+MS) binary mixtures were selected from the literature to test the viscosity mixing rules proposed by 1) Hind (Hi), 2) Grunberg and Nissan (G–N), 3) Herric (He) and 4) Katti and Chaudhri (K–C). The analyses were performed by estimating the average (absolute or relative) deviations, AADs and ARDs, between the available experimental data and the predicted ideal mixture viscosity values obtained by means of each rule. The interaction terms corresponding to the adjustable parameters inherent to each rule were also calculated and their trends discussed.     

Features of Component Interaction in Concentrated Solutions of Multicomponent Systems

Classical complex formation processes in the multicomponent systems Cd(NO₃)₂-MCl-H₂O (M = Li, Cs) occur at preeutectic concentrations of salts. At posteutectic concentrations of salts the formation of cadmium chloride complexes is of structurally enforced nature and depends on the type of the cybotactic group dominating in the solution. The example of the system Cd(NO₃)₂-LiCl-H₂O was used to show that the law of mass action does not apply to systems in which structurally enforced processes occur. Differences in the solubility of MCl (M = Li, Cs, Na) in concentrated solutions of cadmium nitrate are proposed to explain in terms of differences in interactions of cybotactic groups formed by cadmium nitrate and the corresponding chloride.     

Structure of Aqueous Electrolyte Solutions by X-ray Diffraction

Cadmium nitrate and cesium chloride solutions were studied in a wide concentration range by the X-ray diffraction method. The structure of aqueous solutions of the electrolytes is similar to the structure of solid phases that crystallize from them.     

Forces between Carboxylic Acid Surfaces in Divalent Electrolyte Solutions

The behavior of self-assembled monolayers of thiohexadecanoic acid adsorbed onto gold interacting in asymmetric 2:1 electrolytes has been studied with direct force measurements. The effects of two divalent cations (Mg(2+) and Ca(2+)) were studied at concentrations ranging from 1 μM to 10 mM. As compared to interactions in the presence of Na(+), the divalent ions adsorb strongly to the surfaces, with the effect of lowering the surface potential and decreasing the double-layer repulsion. At concentrations above 10 μM, the Ca(2+) ions were found to adsorb stronger than Mg(2+). Ca(2+) ions cause charge reversal at high concentrations, and the net interactions at 10 mM were attractive over the measurable range. Copyright 2000 Academic Press.