乙醇-环己烷体系中NaI活度系数的测定与计算

由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一…     

电解质-非电解质混合溶液活度系数的关联及溶解的推算 II:NH3-NaCl-Na2SO4-H2O体系的液固平衡热力学

由于在研究的体系中, Na2SO4是非对称电解质, 且能生成水合盐, 故推导了由非对称型电解质与非电解质所构成的混合溶液的各组分的活度系数关联通式, 并在此基础上讨论了水合盐液固平衡的计算方法.     

四元交互体系Li~＋，K~＋／Cl~－，SO_4~（2－）－H_2O50，7

采用等温溶解平衡法测定了四元交互体系Ｌｉ～＋，Ｋ～＋／Ｃｌ～－，７５℃的溶解度和平衡溶液的物化性质（密度、粘度、折光率）．该四元交互体系５０，７５℃的溶解度等温图有５个相区：即Ｌｉ＿２ＳＯ＿４·Ｈ＿２Ｏ，ＫＬｉＳＯ＿４，ＫＣｌ，Ｋ＿２ＳＯ＿４，ＬｉＣｌ·Ｈ＿２Ｏ，７条单变量曲线，３个共饱点，其中Ｌｉ＿２Ｏ＿４·Ｈ）２Ｏ＋ＫＣｌ＋ＬｉＣｌ·Ｈ＿２Ｏ为一致零变量点。用我们以往提出的经验公式处理了平衡溶液的密度和折光率，由所测得的溶解度数据，求得了高温和高锂浓度下的电解质溶液Ｐｉｔｚｅｒ模型的离子相互作用参数。计算了各平衡溶液中盐的活度和水的活度。还计算了该四元交互体系２５℃的溶解度，考察了Ｐｉｔｚｅｒ电解质溶液理论在水－盐溶解度计算中的应用。     

Nd(NO_3)_3-HNO_3-H_2O体系的过量吉布斯自由能和Nd(NO_3)_3-HNO_3-H_2O-HDEHP-AMSCO体系水相中各组分活度系数的计算

我们简化了混合电解质溶液过量吉布斯自由能的Pitzer公式。用此简化公式并结合我们以往的工作计算了Nd(NO_3)_3-HNO_3-H_2O体系的过量吉布斯自由能和Nd(NO_3)_3-HNO_3-H_2O-HDEHP-AMSCO体系水相中各组分的活度系数,计算值与实验值均很接近。此工作为镧系金属萃取分离进行热力学分析提供了方便。     

手持技术数字化实验促进模型建构的化学教学——沉淀溶解平衡

创设了4组数字化实验情境,将较为抽象的沉淀溶解平衡转化为简单的曲线表征。学生主动解决与曲线相关联、层层递进的问题,解决问题的同时认识了难溶电解质的“可溶”,建构了沉淀溶解平衡模型,通过定量计算理解了溶度积的概念,并利用Q与K_sp的关系判断平衡的移动。其中利用浊度传感器测浊度的数字化实验解决了向碳酸钙饱和溶液中加碳酸钠溶液无法用肉眼观察到溶液变浑浊现象的难题。     

电解质-非电解质混合溶液活度系数的关联及溶解度的推算——Ⅱ.NH_3-NaCl-Na_2SO_4-H_2O 体系的液固平衡热力学

由于在研究的体系中,Na_2SO_4是非对称电解质,且能生成水合盐,故推导了由非对称型电解质与非电解质所构成的混合溶液的各组分的活度系数关联通式,并在此基础上讨论了水合盐液固平衡的计算方法.     

含锂水盐体系热力学性质研究:LiCl-MgCl~2-H~O体系渗透系数和活度系数的等压测定

25℃下,用等压法测定了单盐水溶液(浓度范围分别为0.5-19.8mol.kg^-1,0.3-6.0mol.kg^-1)以及混合水溶液(离子强度范围为0.6-19.4mol.kg^-1)的水活度和渗透系数,同时测定了LiCl的溶解度.该体系的实验等水活度线符合本工作推导出的Zdanovskii规则扩展式,用Gibbs-Duhem方程和改进的Mckay-perring方法计算了单盐和混合盐水溶液的活度系数.由本实验获得的渗透系数拟合了Pitzer单盐和混合作用参数,检验了Pitzer方程对该体系渗透系数、活度系数和溶解度预测的适用性.用Pitzer方程取本工作得到的参数计算的溶解度与文献实验值基本一致.     

含锂水盐体系热力学性质研究:LiCl-MgCl~2-H~O体系渗透系数和活度系数的等压测定

25℃下,用等压法测定了单盐水溶液(浓度范围分别为0.5-19.8mol.kg^-1,0.3-6.0mol.kg^-1)以及混合水溶液(离子强度范围为0.6-19.4mol.kg^-1)的水活度和渗透系数,同时测定了LiCl的溶解度.该体系的实验等水活度线符合本工作推导出的Zdanovskii规则扩展式,用Gibbs-Duhem方程和改进的Mckay-perring方法计算了单盐和混合盐水溶液的活度系数.由本实验获得的渗透系数拟合了Pitzer单盐和混合作用参数,检验了Pitzer方程对该体系渗透系数、活度系数和溶解度预测的适用性.用Pitzer方程取本工作得到的参数计算的溶解度与文献实验值基本一致.     

活度系数法测定A2B型难溶盐的溶度积——以Ag2SO4为例

实验假设水溶液中Ag+和SO42－的浓度非常低时,其活度无论处于同一体系还是在不同体系均相同。依此设计原电池,使该原电池的电池反应为Ag2SO4(s)→2Ag+(aq)+SO42－(aq),采用补偿法测量一定温度下此原电池中AgNO3溶液浓度和K2SO4溶液浓度发生变化时的电池电动势E。依据能斯特方程和Debye-Huckel极限公式,推导出原电池标准电动势E?与电解质的平均活度系数γ±及溶液浓度的关系,用外推法作图得到此电池反应的标准电动势E?。由平衡常数与原电池标准电动势的关系,得到Ag2SO4的溶度积Ksp(Ag2SO4)。     

利用吉布斯吸附等温式探索求解电解质溶液活度的新方法

以吉布斯吸附等温式积分式为基础,数学推证表面势的表达式,并应用表面势的数学表达式探求了一种测算电解质溶液活度系数的新方法.选取KIM计算电解质溶液溶质的活度系数公式为新方法的活度系数经验关系式的具体表达形式,利用实验直接测得的不同浓度下的表面张力数据,采用最优化拟合的方法,求算出活度系数经验关系式中的待定系数,从而可以求得不同浓度下的电解质溶液中的溶质的活度系数和活度.计算结果与KIM文献值对比,活度系数曲线在不同的坐标尺度下有很好的一致性,这使得通过测定电解质溶液表面张力测算其活度成为可能.     

Self-diffusion coefficients of ions in the presence of charged obstacles

The self-diffusion coefficient of ions of the charge- and size-symmetric +1:-1 (or +2:-2) electrolyte was studied in the presence of ionic obstacles (matrix) representing disordered media. For this purpose the Brownian dynamics method was used, complemented with the replica Ornstein-Zernike theory for the partly-quenched systems. The matrix was prepared by a rapid quench of the size-symmetric +1:-1 (in few cases also of +2:-2) electrolyte solution being in equilibrium at (temperature, relative permittivity) T0, epsilon. Within the matrix the charge- and size-symmetric (+1:-1 or +2:-2) electrolyte at T1, epsilon1 was distributed. This component was fully mobile (annealed) and in thermodynamic equilibrium with the matrix. In this study a special attention was paid to the self-diffusion of the annealed ions. The ratio D/D degrees, where D degrees is the self-diffusion coefficient of ions at infinite dilution, has been studied for various model parameters varying the concentration of all species in the system. The presence of charged obstacles decreases the self-diffusion of the annealed electrolyte; the D/D degrees values are lower in the partly-quenched mixtures than in the fully annealed electrolyte of the same concentration. In the investigated range of concentrations and solvent dielectric constants, the D/D degrees values first increased with the increased concentration of annealed electrolyte present and then decreased. An increase of the strength of the Coulomb interaction between annealed ions, or between annealed and quenched charges, yielded a decrease of the self-diffusion. In the range of concentrations investigated in this work, the decrease is mainly due to the Coulomb interaction with the matrix, since the presence of neutral obstacles did not modify the diffusion properties with respect to the situation without obstacles.     

金属溶剂萃取的热力学研究(Ⅶ)——2-乙基己基膦酸单(2-乙基己基)酯-硫酸钻-硫酸铜体系

本文提出了具有相同电荷的同号离子间作用力相等的假定, 简化了Pitzer的电解质溶液活度系数计算公式, 用此公式, 计算了H_2SO_4-CoSO_4-CuSO_4水相体系各单个离子活度系数以及水的渗透系数。本文还应用由作者提出的工作参考态法, 应用改进的Scatchard-Hildebrand模型计算了EHEHPA-CoSO_4-CuSO_4萃取体系中有机相各组分的活度系数以及萃取反应热力学平衡常数.     

含氯化钠电解质水溶液体系热力学性质研究进展

总结了近几十年来含氯化钠电解质水溶液体系热力学性质的研究成果及其在盐湖、地下卤水、油田水和海盐制备等领域的应用,并对含钠水盐体系在不同温度下的热力学性质进行了总结,对于推动含钠水盐体系电解质溶液理论的发展和促进富盐湖卤水、地下卤水及海水的开发利用具有重要的意义。     

Modeling of the Ion Exchange in Pulp Suspensions by Gibbs Energy Minimization

The ion exchange processes, which occur when two compartments of aqueous solutions separated by a semipermeable interface are placed in aqueous electrolyte solutions, were modeled using the multiphase Gibbs energy-minimization method. The Gibbs energy-minimization technique was applied for the ion-exchange system consisting of pulp fibers and the surrounding aqueous bulk solution. In such a system, the anionic acid groups inside the fibers cause an uneven distribution of ionic species between the solution within the fiber walls and the solution external to the fibers. The method was tested with four cation concentrations, which are naturally present in the fibers and whose partitioning between the fiber phase and the external solution phase has been described earlier. Although the Donnan distribution constant is not explicitly calculated in the Gibbs energy-minimization model, the results are consistent with the Donnan equilibrium theory. With the Gibbs energy-minimization multiphase model, the formation of solid precipitates can also be calculated.     

Synthesis and characterization of an amphoteric ion-exchange membrane

An amphoteric ion-exchange membrane was prepared by chemical grafting of acrylic acid and dimethyl amino-2-ethyl methacrylate on ozonized polyethylene. The effects of the variation of external pH on the physicochemical properties of this membrane were studied (exchange capacity, electrical resistance, water and electrolyte content, and membrane potential). The determination of the mean activity coefficient of the NaCl in the membrane phase using the Donnan equilibrium equation reveals that this coefficient increases with the NaCl concentration in the external solution. Fundamental electrochemical properties of the amphoteric membrane are discussed on the basis of the variation of the membrane selectivity with the external electrolyte concentrations and the pH. The properties at neutral pH are accounted for by a mutual neutralization of some acidic and basic groups in the membrane phase.     

Numerical calculation of the electrophoretic mobility of colloidal particles in weak electrolyte solutions

A numerical calculation of the electrophoretic mobility of colloidal particles in weak electrolyte solution is presented. It is based on a previous work (C. Grosse, V.N. Shilov, J. Colloid Interface Sci. 211 (1999) 160-170), where the analytical theory of the thin double layer concentration polarization is generalized to the case of weak electrolytes, i.e., when the dissociation-recombination equilibrium and rate constants both have finite values. The analytical results are first completed by including terms corresponding to co-ions that were neglected in the original presentation. It is shown that these terms that have little bearing in the case of strong electrolytes, become quite important in the case when the electrolyte is weak. The problem is then solved using the network method, leading to numerical results for the electric potential and the concentrations of counterions, co-ions, and neutral ion pairs. Finally, the electrophoretic mobility is calculated both analytically and numerically. It is shown that the hypothesis of a weak electrolyte leads to changes of mobility with respect to the classical results that are even stronger than predicted analytically.     

广义渗透系数

本文将Bjerrum渗透系数概念推广到混合溶剂体系中,提出了广义渗透系数的概念及其一般定义式,并导出了广义渗透系数与电解质活度系数之间的相互关系式,从而可以借助于广义渗透系数较易实现混合溶剂体系中溶质与溶剂热力学性质之间的相互推算,同时,混合溶剂作为一个整体的非理想性亦可得到具体度量.因此引入广义渗透系数概念具有理论与实际意义.     

甲醇-苯混合溶剂中NaI活度系数的测定与计算

测定了甲醇-苯-NaI体系在恒压条件下的汽液平衡数据,采用双标准检验法对数据进行检验,检验结果全部合格.应用P itzer强电解质在水溶液中的活度系数模型,采用全部合格的汽液平衡数据拟合出方程中的维利系数,从而获得在双液比固定条件下盐在甲醇-苯混合溶剂中的活度系数.计算结果表明,正常泡点温度下在具有固定双液比的甲醇-苯混合溶剂中,NaI的平均活度系数随盐浓度的增加先减小,经过一个极小值后又增加.     

Partition Equilibrium on the Interface Between a Charged Membrane and a Mixed Electrolyte Aqueous Solution

Ionic partition equilibrium on a charged membrane immersed in a mixed electrolyte solution was systematically investigated and several models were established for the determination of partition coefficients.On the basis of theoretical models,the effects of the concentration ratio λof the fixed group(charged density) to reference electrolyte,the concentration ratio η between the two electrolytes existing in the solution and the valence of the electrolyte ions on the partition equilibrium in a positively charged membrane were analyzed and simulated within the chosen parameters in detail.The obtainable results can also be applicable to a sytem of mixed electrolytes contacting with a negatively charged membrane.The theoretical calculations were confirmed with the experimental data of model mixed electrolytes,NaCl HCl and CaCl2 NaCl partitioned in the system of self-made negatively charged membrane-sulphonated poly (phenylene oxide)(SPPO) with different charge densities.