Hydrogen isotope effects in the dehydration of polystyrene-divinylbenzene type ion-exchange resins and the structure of electrolyte solutions. 1. Li+ form of variously cross-linked Dowex 50W resins

Hydrogen isotope effects in the dehydration of the lithium form of strong acid polystyrene-divinylbenzene type ion exchangers (Dowex 50W) of varying cross-linking (2 to 12% DVB content) have been determined by a Rayleigh distillation type technique. The single-stage separation factors, α, were dependent only on n/sub w/ and were independent of resin cross-linking. At n/sub w/ approx. = 4, α was lower than α/sub w/, the separation factor for pure water distillation at the same temperature. In the region of n/sub w/ = 10 to 12, α was greater than α/sub w/ and reached a maximum value. Beyond n/sub w/ approx. = 12, α decreased gradually with n/sub w/ but remained greater than α/sub w/. These results have been interpreted in terms of the hydration of lithium ions in the resin phase. These data indicate that the counterions in resin phase water behave like single ion solutions, provided counterion-water interactions are much greater than counterion-ionogenic group interactions. The resin network seems to influence the outermost layers (beyond the second hydration shell) of water molecules via hydrophobic interactions. 1 figure, 3 tables