An electrochemical and theoretical comparison of ionic transport through a polystyrene based titanium-vanadium (1:2) phosphate membrane

Ionic potentials were measured across polystyrene based titanium-vanadium (1:2) phosphate membranes with 1:1 electrolytes at different concentrations. These observed values are found to compare well with membrane potentials calculated from theoretical equations derived by Teorell-Meyer-Sievers (TMS). Membrane parameters have been used to examine the validity of the theory utilized. The observed values of membrane potentials have been found to decrease with an increase of electrolyte concentration and follow the sequence Li(+)> Na(+)> K(+) and are potentials all positive. This shows that the membrane is cation-selective. The ion mobilities of electrolytes are significantly affected by groups of fixed charge in the membrane. The distribution coefficient values were observed to diminish with increasing electrolyte concentration and follow the sequence KCl > NaCl > LiCl. The values of fixed charge density and charge effectiveness obtained by this simple method are in good agreement with those reported in literature. The charge effectiveness values are found to increase with the hydration radii of the electrolytes. (C) 2011 Elsevier B.V. All rights reserved.