MODELING CHEMICAL EQUILIBRIUM OF ELECTROLYTE SOLUTIONS

ABSTRACT

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–Hückel 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 based rather than simply presenting the equations required for its implementation.

Keywords:

• electrolyte solutions
• ionic activity coefficients
• semi-empirical models

ACKNOWLEDGMENTS

This work was carried out under the “HERAKLITUS” project which is co-funded by the European Social Fund (75%) and National Resources (25%).