Correlation between equilibrium and NMR spectroscopic data in the study of the selectivity of cross-linked ionic polymers

摘要

Ion-exchange equilibrium and ~(31)P NMR measurements were used for the study of the ion-exchange distribution of phosphonic acid anions in various types of ion-exchange materials. An equation was derived for the calculation of ion-exchange selectivity coefficients of the monovalent and bivalent anions from the pH dependence of the measured distribution coefficient of the acid. The equation derived was also used to calculate the hydrogen ion concentration inside the polymer phase. ~(31)P NMR spectra of the equilibrium resin phase were studied as a function of pH. On the basis of the relationship derived for the pH dependence of the observed ~(31)P NMR shift of phosphonic acid the resin phase the chemical shifts of the monovalent and bivalent anions were calculated. The linear relationship observed between the calculated selectivity coefficients and the resin-phase ~(31)P chemical shifts proves that interactions responsible for ion-exchange selectivity (thermodynamic data) and chemical shifts (spectroscopic data) are strongly correlated in the systems studied.