Determination of ion exchange equilibrium constants of strongly acidic resins with alkaline-earth metals by means of the potentiometric titrations technique

(A) recently developed methodology for the determination of ion exchange eq uilibrium constants has been applied to ion exchange systems of 1:2 stoichi ometry. Potentiometric titrations with variable ionic strength were carried out. Ionic medium titrations were performed for the estimation of the liqu id junction potential. The modified Bromley's methodology and the Wilson mo del were used for the estimation of the activity coefficients of the specie s in the aqueous and resin phase, respectively. A modification of the Hende rson equation is used for the estimation of liquid junction potentials in t he mixtures including 1:2 electrolytes. Equilibrium constants for the H+/M2 + (M = Mg, Ca, Sr and Ba) exchange systems in the strongly acidic resins Do wex CM-15 and Dowex C650 were studied. (C) 1999 Elsevier Science B.V. All r ights reserved.