Cation exchange with reverse-micelles

Experimental and theoretical studies on the extraction of the cation K$ sp+$ and Mg$ sp{++}$ from a bulk aqueous phase to an organic phase using the water/dinonylnaphthalene sulfonic acid (HD)/heptane reverse-micellar system was conducted. The counter ion of the surfactant, H$ sp+$, was exchanged with the alkali metal cations in the aqueous phase. Two different types of experiments were conducted. The first set involved a constant total normality of ions while the second investigated the effect, of varying the normality of ions. Electrolyte solutions with molarities ranging from 0 to 1 were contacted with a reverse-micellar organic containing different concentrations of surfactant with different types of counter ions.The HD reverse-micellar extraction system exhibited behavior similar to that of conventional ion-exchange resin systems. A preferential extraction for Mg$ sp{++}$ over K$ sp+$ was observed. The efficiency of the extraction was high for low salt concentrations and it was independent of surfactant concentration. The amount of water uptake was low, with W$ sb{o}$ ranging between 4 and 10. For a wide range of salt and surfactant concentrations W$ sb{o}$ was independent of surfactant concentration. The HD surfactant showed a low solubility in the aqueous phase.The results of the equilibrium partition experiments were correlated using a thermodynamic model. Interaction parameters determined from binary system experimental data were used to predict the ternary system partition behavior. The ternary system predictions were compared with experimental results and found to be satisfactory