Modeling the chemical equilibrium in ionic solutions encountered in industrial applications, especially in the field of hydrometallurgy, still remains an unresolved issue. The complicated speciations, as well as the high ionic strengths encountered in these solutions, render the theories of analytical chemistry practically useless. The Debye–Huckel theory is examined in depth, so as to reveal the reasons of its failure. To remedy this problem, over the years, a large number of semi-empirical models have been proposed that are here reviewed, in order to help the reader find a model best suited for a system of interest. The models are classified into three main categories, based on their fundamental logic: ion interaction models describe the system through the physical interactions of the ions; ion association models describe the system through chemical equilibriums; and finally hybrid models use concepts from both previous categories. Focus is given in presenting the idea upon which each model is ...

Modeling chemical equilibrium of electrolyte solutions

Experiment and model investigation of D-sorbitol as a thermodynamic hydrate inhibitor for methane and carbon dioxide hydrates

Extension of some local composition models for correlation of the apparent molal volume of aqueous electrolytes at 298.15 K

Isopiestic determination of osmotic coefficients and evaluation of vapor pressures for solutions of sodium bromide and sodium thiocyanate in methanal at 25 °C

A new model for the excess Gibbs energy of hydrotrope solutions is presented. This model is based on the local composition model by Chen et al. Hydrotropes are usually organic salts that can increase the solubility of organic and inorganic compounds in water. The proposed model has five adjustable parameters; one of them is related to long-range forces, and four of them are related to short-range forces. Long-range forces are modeled by the Pitzer-Debye-Huckel equation. However, in our model, the effect of the molecular solute on the dielectric constant of water has also been considered. Modeling of short-range forces is based on local composition concepts. The model parameters are obtained using experimental data for six hydrotropes with four solutes at different temperatures. The water solubility of molecular solutes in the presence of hydrotropes has been calculated for different systems. Accurate results are obtained. © 2005 American Institute of Chemical Engineers AIChE J, 2006

K.V. Narayanan

Papers

A modified self-consistent local composition model for the thermodynamic properties of single and mixed electrolytes

Excess gibbs free energy of mixing