WATER SORPTION ISOTHERMS AND CATION HYDRATION IN DOWEX 50W AND AMBERLYST-15 ION-EXCHANGE RESINS

Water sorption isotherms of gel-type Dowex 50WX4 and Domex 50WX8 and m acroreticular Amberlyst-15 in H+, Na+, and alkaline earth metal ionic forms have been determined at 298 +/- 1 K using the isopiestic techniq ue. The hydration numbers of cations derived from the analysis of the water sorption isotherms using the D'Arcy and Watt equation compare we ll with those reported for similar types of ion exchangers obtained us ing other techniques. An interesting feature that has emerged from the analysis is the presence of a constant amount of water having bulk st ructure in Amberlyst-15, irrespective of the nature of the cations, po ssibly those filling the pores of the exchanger. The present study, th us, indicates the structural differences between the water present in the gel phase and in the pores of the macroreticular Amberlyst-15.