Rhenium hepta-oxide (Re2O7) is the most prominent Re compound industrially produced as a by-product of molybdenum roasting process. This material is highly soluble in water resulting in formation of ReO4– anions dissolved in a weak acid medium. For ReO4– extraction, different ion exchange (IX) resins can be used to adsorb the metal containing anion. Ion exchange reactions are generally obscure with unknown stoichiometric coefficients simply assumed equal to unity by majority of researchers. These coefficients play a significant role in the thermodynamics and kinetics calculations carried out for design and optimization of the IX systems. Combining the experimental data obtained for the three different brands of resins used in this investigation with the equilibrium correlations, the stoichiometric coefficients of the ReO4– anion exchange reactions with Cl– anion were mathematically determined. Utilizing the stoichiometric coefficients obtained and measuring the effect of temperature on the rhenium distribution ratio between solution and the resins, the apparent standard Gibbs free energies of the ion exchange reactions for standard states were evaluated for followings: (a) ionic resin: resin leached in 1 normal hydrochloric acid aqueous solution, (b) metal containing solution: 1 normal potassium perrhenate and (c) salt produced by exchange reaction: 1 normal potassium chloride dissolved in water were determined. The said reactions were found to be as follows:
(j/mol) for Amberlite,
(j/mol) for Varion
(j/mol) for Purolite
Anionic resins.
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