Abstract
Biionic and multiionic potentials arising across parchment supported nickel and cobalt phosphate membranes using various combinations of 1:1 electrolytes at different concentrations have been measured. The intramembrane permeability ratio of cations has been derived using the plotting method. Conductivity of membranes in contact with simple 1:1 electrolytes has been experimentally determined in order to evaluate selectivity of membranes using the predetermined values of the intramembrane permeability ratio. The selectivity sequence of both the membranes has been found as K +>Na +>Li +, which on the basis of the Eisenman-Sherry model of membrane selectivity, points towards the weak field strength of the charge groups on the membrane matrix. Perfect Donnan exclusion of coions was realized in the dilute limit of the external solution. Potentiometric selectivity constants K ij pot have also been evaluated by the improved method of Buck et al. based on the integrated form of the Nernst-Planck flux equation.
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