Metal-ion separation by dialysis through solvent membranes

High specificity membranes for selective ion transport are described. In contrast to common dialysis and electrodialysis membranes, discriminating the passage of species because of either size or charge, the present membranes appear to involve a simple solubility mechanism. With the aim of utilizing such membranes as a tool for hydrometallurgical separations, an acid feed solution containing uranyl, iron, aluminum, and nitrate ions was chosen for study. When an alkyl-phosphoric ester containing polymeric membrane was used, uranyl nitrate could be separated from this solution with practically complete selectivity. Permeability depended principally on the distribution coefficients between the aqueous phases in contact with the membrane and the membrane phase. To be of practical value, the lifetime of the membranes would have to be extended.