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Thermodynamics of phase equilibria in aqueous‐organic systems with salt
Author(s) -
Zerres H.,
Prausnitz J. M.
Publication year - 1994
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690400411
Subject(s) - molality , aqueous solution , chemistry , thermodynamics , solvation , ternary operation , activity coefficient , solvent , salt (chemistry) , ion , debye–hückel equation , electrolyte , organic chemistry , physics , electrode , computer science , programming language
A semiempirical thermodynamic method is developed to establish a framework for calculating vapor‐liquid and liquid‐liquid equilibria in ternary systems containing water, an organic solvent, and a salt. Careful attention is given to precise definition of standard states. Short‐range ion‐solvent forces are taken into account primarily by a chemical‐equilibrium method based on stepwise ion solvation; however, physical contributions also contribute. Water‐cosolvent nonideality is described by an extended equation of the van Laar form. Long‐range electrostatic forces between ions are taken into account by an extended Debye‐Hückel equation with corrections for transferring from a McMillan‐Mayer to a Lewis‐Randall framework. The new method is illustrated with results for several systems including saturated aqueous mixtures of LiBr or LiCl with methanol where the salt concentration exceeds 20 molal. The method developed here is of particular interest for process calculations in extractive crystallization, a low‐energy operation for producing salt from aqueous solution.