The conventional devices (e.g., stirred and tubular dializers) employed in Donnan dialysis experiments do not permit precise description of the associated hydrodynamics. Consequently, detailed analysis of the transport mechanism (e.g., decoupling of boundary layer and membrane diffusion effects) is often difficult. In an effort to alleviate this difficulty, the rotating diffusion cell (RDC) introduced by Albery et al. (J. Chem. Soc., Faraday Trans. I, 72 (1976) 1618-1624) has been adapted to the study of Donnan dialysis. The porous filter used in the original design has been replaced with an ion-exchange membrane (Nafion® 117, DuPont). The membrane, which separates the reservoir and receiving solutions, is mounted on the base of a hollow rotating cylinder which contains a stationary baffle. The rotation of the cylinder causes well-defined fluid motion on both sides of the membrane so that boundary layer and membrane diffusion control can be readily distinguished and studied. Application of the RDC to Donnan dialysis is illustrated with the Nafion membrane/CoSO4-H2SO4 system.
All Science Journal Classification (ASJC) codes
- General Materials Science
- Physical and Theoretical Chemistry
- Filtration and Separation