Approach to the surface characteristics of the H+ and H+-La3+ forms of cation-exchange resins by measurement of the heat of immersion

Surface characteristics of H+ and its multivalent cation-exchanged resins, which have been used as catalysts, were probed by measurement of the heats of immersion in 1-nitropropane, n-hexane, and water. It was found that the electrostatic field strengths (F) calculated from the heats of immersion in 1-nitropropane and n-hexane increased with increasing ratios of the exchanged multivalent cation (La3+) in the univalent form (H+) cation-exchange resin. This tendency was also observed in the differences in F between the La3+ exchanged resins and H+ form of the resin by using the calorimetric data obtained from the heats of immersion in water. These results suggest that the exchanged La3μ ion does not homogeneously interact with three univalent anionic sites (SO3-) of the cation-exchange resin, but interacts with only two SO3- ions, that is, the La3+ ion is localized on the surface of the resin. The difference in F obtained from the heats of immersion into water was found to be useful as a simple and rapid criterion of the surface characteristics of the cation-exchange resins. 18 references, 4 figures, 1 table