Selectivity Coefficient of Lysine for Strong Cation-Exchange Resins of the Ammonium Form

Abstract

The selectivity coefficients of both the mono- and divalent forms of lysine for cation-exchange resins of the ammonium form were measured on the basis of the mass action law, and found to increase with decreasing divinylbenzene (DVB) content and also to increase with increasing temperature, while they remained constant in the concentration range of 0.05 to 0.6 mol/1 at equilibrium. The signs of both the enthalpy and entropy changes for the ion-exchange are positive in this system. The selectivity coefficient for the monovalent form is well expressed by Gregor’s model including the contribution of differences in the molar volume and osmotic pressure, and the results for the divalent form suggest the contribution of the change in the conformation of water which reflects both the positive entropy and enthalpy changes.