Document Type

Dissertation

Date of Award

1975

Keywords

Diffusion, Ion exchange resins, Solution (Chemistry), Dimethyl sulfoxide

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

S.K. Madan

Second Advisor

B. McDuffie

Third Advisor

Michael E. Starzak

Abstract

Diffusion coefficients, DBULK, of dimethyl sulfoxide (DMSO) were measured in free (“bulk”) aqueous mixtures by the capillary method using sulfur-35 labeled DMSO. The value of DBULK was found to pass through a minimum at approximately 33 mole percent DMSO as DMSO concentration was increased. The diffusion of DMSO in a typical polystyrenesulfonate resin (AG50W-X8) was studied as a function of solvent composition and temperature using an infinite volume-type apparatus. A combined particle-film diffusion equation was employed to obtain the intra-particle diffusion coefficients, D. The value of D decreased very rapidly with increasing mole percent DMSO up to approximately 33 mole percent DMSO, but leveled off thereafter which contrasts with the continued rapid drop of D found earlier for alkali ion diffusion under identical conditions. It is suggested that up to 33 mole percent DMSO the formation of DMSO-water associates (1:2) may cause significantly slower solvent transport through the constrictions of the resin phase, although merely higher viscosity (as distinct from obstriction) may account for part of the effect. On going to mixtures even richer in DMSO, once the 33 mole percent stoichiometric point is passed, more “free” DMSO is being added so that DDMSO reaches a plateau while DDMSO in the bulk phase starts to rise. The diffusion behavior of DMSO in aqueous DMSO media is seen to be a consequence of the strong DMSO-water interactions in the liquid phase, and the implications for ion exchange in DMBO-water mixed solvent systems are discussed in this context.

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