An Isotherm-Based Thermodynamic Model of Multicomponent Aqueous Solutions, Applicable Over the Entire Concentration Range

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• 作者：Cari S. Dutcher ; Xinlei Ge ; Anthony S. Wexler ; Simon L. Clegg
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：April 18, 2013
• 年：2013
• 卷：117
• 期：15
• 页码：3198-3213
• 全文大小：828K
• 年卷期：v.117,no.15(April 18, 2013)
• ISSN：1520-5215

文摘

In previous studies (Dutcher et al. J. Phys. Chem. C<span class="NLM_x"> span>2011<span class="NLM_x">, span>m>115,m><span class="NLM_x">, span>16474鈭?6487;<span class="NLM_x"> span>2012<span class="NLM_x">, span>m>116,m><span class="NLM_x">, span>1850鈭?864), we derived equations for the Gibbs energy, solvent and solute activities, and solute concentrations in multicomponent liquid mixtures, based upon expressions for adsorption isotherms that include arbitrary numbers of hydration layers on each solute. In this work, the long-range electrostatic interactions that dominate in dilute solutions are added to the Gibbs energy expression, thus extending the range of concentrations for which the model can be used from pure liquid solute(s) to infinite dilution in the solvent, water. An equation for the conversion of the reference state for solute activity coefficients to infinite dilution in water has been derived. A number of simplifications are identified, notably the equivalence of the sorption site parameters r and the stoichiometric coefficients of the solutes, resulting in a reduction in the number of model parameters. Solute concentrations in mixtures conform to a modified Zdanovskii鈥揝tokes鈥揜obinson mixing rule, and solute activity coefficients to a modified McKay鈥揚erring relation, when the effects of the long-range (Debye鈥揌眉ckel) term in the equations are taken into account. Practical applications of the equations to osmotic and activity coefficients of pure aqueous electrolyte solutions and mixtures show both satisfactory accuracy from low to high concentrations, together with a thermodynamically reasonable extrapolation (beyond the range of measurements) to extreme concentration and to the pure liquid solute(s).