Influence of temperature on the exchange of alkaline earth and transition metals on iminodiacetate resin

Abstract

Ion exchange equilibrium studies were carried out for Mg2+, Ba2+, Ca2+, Sr2+, Cu2+, Pb2+, Hg2+, Ag+, Mn2+, Ni2+, Fe3+ ions using Amberlite IRC 718, a weakly acidic ion exchanger containing the iminodiacetate group as a chelating functionality. Influence of temperature on the exchange equilibrium of these metal ions was studied in the temperature range 282-323 K. Exchange isotherms were plotted for these ions; which indicated a differential selectivity. Plots of the logarithm of selectivity coefficient and equivalent fraction of the metal ions in the exchanger phase gave the value of equilibrium constant (K-a). Based on the values of selectivity coefficient (K-c) values, selectivity of the resin for alkaline earth metal ions was in the order Sr2+ > Ba2+ > Ca2+ > Mg2+ and for transistion metals studied the selectivity was in the order Ni2+ > Cu2+ > Pb2+ > Mn2+ > Hg2+ > Fe3+ > Ag+. Various thermodynamic parameters were calculated and the results indicate the preferential uptake of divalent cations over Na+ ions.