Reverse Osmosis Separations of Some Inorganic Solutes in Ethanol Solutions Using Cellulose Acetate Membranes

Reverse osmosis separations of 20 inorganic solutes from ethanol solutions were studied by using porous cellulose acetate membranes. The experimental results were analyzed by basic transport equations developed by Kimura and Sourirajan. On the basis of the above analysis the free energy parameters of ions were calculated and compared with the values obtained from water and methanol solvent systems. The study confirms that the difference in the free energy parameters among univalent cations and univalent anions is widened in the solvent of a lower dielectric constant; such an enhanced difference is further reflected in the increase of the difference among inorganic solute separations from the solvent of a lower dielectric constant. Consequently, fractionation of inorganic solutes can be performed more easily in ethanol solvent than in water and in methanol solvent.