Electrolyte volatile weak

Yoo KP, Lee SY, Lee WH. 1986. Ionization and Henry s Law constants for volatile, weak electrolyte water pollutants. Korean J Chem Eng 3 67-72. 

Many of the undesirable substances present in gaseous or liquid streams form volatile weak electrolytes in aqueous solution. These compounds include ammonia, hydrogen sulfide, carbon dioxide and sulfur dioxide. The design and analysis of separation processes involving aqueous solutions of these materials require accurate representation of the phase equilibria between the solution and the vapor phase. Relatively few studies of these types of systems have been published concerning solutions of weak electrolytes. This paper will review the methods that have been used for such solutions and, as an example, consider the alkanolamine solutions used for the removal of the acid gases (H2S and C02) from gas streams. 

Recently, there have been a number of significant developments in the modeling of electrolyte systems. Bromley (1), Meissner and Tester (2), Meissner and Kusik (2), Pitzer and co-workers (4, ,j5), and" Cruz and Renon (7j, presented models for calculating the mean ionic activity coefficients of many types of aqueous electrolytes. In addition, Edwards, et al. (8) proposed a thermodynamic framework to calculate equilibrium vapor-liquid compositions for aqueous solutions of one or more volatile weak electrolytes which involved activity coefficients of ionic species. Most recently, Beutier and Renon (9) and Edwards, et al.(10) used simplified forms of the Pitzer equation to represent ionic activity coefficients. 

Edwards, T. J., John Newman and J. M. Prausnitz, "Thermodynamics of Aqueous Solutions Containing Volatile Weak Electrolytes," AIChE J., 1975, 21, 248. 

On the Solubility of Volatile Weak Electrolytes in Aqueous Solutions... 

This contribution describes and compares three procedures for representing vapor-liquid equilibria in multicomponent aqueous solutions of volatile weak electrolytes. Starting from the basic thermodynamic relations, the approximations and simplifications applied by van Krevelen, Hoftijzer and Huntjens ( ), Beutier and Renon (2) and Edwards, Maurer, Newman and Prausnitz (3) are discussed the necessary information for using these correlations is compiled. Results calculated with these procedures are discussed and compared with literature data. 

As shown in figure 1, a volatile weak electrolyte in water at a given temperature and pressure distributes itself between vapor and liquid phase. Phase e-quilibrium determines the concentration of the weak electrolyte in the gaseous phase at a known concentration of molecular electrolyte in water. But due to... 

VAN AKEN et al. 0) and EDWARDS et al. (2) made clear that two sets of fundamental parameters are useful in describing vapor-liquid equilibria of volatile weak electrolytes, (1) the dissociation constant(s) K of acids, bases and water, and (2) the Henry s constants H of undissociated volatile molecules. A thermodynamic model can be built incorporating the definitions of these parameters and appropriate equations for mass balance and electric neutrality. It is complete if deviations to ideality are taken into account. The basic framework developped by EDWARDS, NEWMAN and PRAUSNITZ (2) (table 1) was used by authors who worked on volatile electrolyte systems the difference among their models are in the choice of parameters and in the representation of deviations to ideality. 

Acetic Acid-Water Mixture. CRUZ (4) chose this example to illustrate his method of representation of vapor-liquid equilibria of volatile weak electrolyte and to show how to obtain simply from experimental vapor-liquid equilibrium data the significant parameters. ... 

Appendix. Formalism of BEUTIER S Model of Volatile Weak Electrolytes Vapor-Liquid Equilibria... 

Volatile weak electrolytes, such as ammonia, carbon dioxide, and hydrohydrogen sulfide are of great interest in hydrometallurgy. The vapor-liquid... 

Several computer-based techniques have been developed for more specific applications. Truesdell (45) describes a computer program for calculating equilibrium distributions in natural water systems, given concentrations and pH. Edwards, et al. (31, Z2) have developed computer programs for treating volatile weak electrolytes such as ammonia, carbon dioxide and hydrogen sulfide systems however, in their present state these programs (presumably) do not accommodate metallic species in solutions. 

The absorption rate of carbon dioxide increases in the presence of amines or ammonia. Therefore, the reaction kinetics of NH3 and C02 has been considered in the model equations, too. The rate constant as a function of the temperature has been determined according to Ref. 136. The coefficients for the calculation of the chemical equilibrium constants in this system of volatile weak electrolytes are taken from Ref. 137. 

Maurer G. On the solubility of volatile weak electrolytes in aqueous solutions. ACS Symp Ser 1980 133 139-172. 

T. J. Edwards, J. Maurer, J. Newman, et ah, Vapor-liquid equilibria in multicomponent aqueous solutions of volatile weak electrolytes, AIChE /., 1978, 24, 966-976. 

T. J. Edwards, Thermodynamics of Aqueous Solutions Containing One or More Volatile Weak Electrolytes, M.S. Thesis, University of California, Berkeley (1974). C. M. Gates and J. Newman, Equilibrium and Diffusion of Methanol and Water in a Nafion 117 Membrane, AIChE Journal, 46, 2076 (2000). 

OPl. Edwards, T.J., G. Maurer. J. Newman and J.M. Prausnitz, "Vapor-Liquid Equilibria in Multicomponent Aqueous Solutions of Volatile Weak Electrolytes", AIChE J., 24. 966 (1978)... 

Containing Volatile Weak Electrolytes", AIChE J, v21, 2, pp248-259 (1975)... 

From G. Maurer, "On the Solubility of Volatile Weak Electrolytes In Aqueous Solutions", Thermodynamics of Aqueous Syatema with Industrial... 

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