Clusius-Dickel Separation: A New Look at an Old Technique

The Clusius-Dickel (CD) technique couples thermal diffusion to a counter-current, natural convective flow to effect separation of molecules of different molecular weights or shapes in liquid or gaseous solutions. Materials separable by the technique include: aqueous biological solutions, isotopes in both gas and liquid states, aqueous solutions of both ionized and un-ionized materials, organic solutions, liquid metallic solutions, fused salt solutions, and gas mixtures including ortho and para-hydrogen. The technique was discovered in the late 1930s by K. Clusius and G. Dickel but fell into relative obscurity for commerical applications about 20 years after its discovery. The reasons for its decline included a number of deleterious apparatus and operating features among which were large power requirements, costly equipment construction, and small processing volumes. The present study, however, after critically reexamining the Clusius-Dickel separation (CDS) technique, concludes that the objectionable features of the technique can probably be circumvented by a number of means among which are: utilizing modified cell designs; combining the CD technique with other separative techniques or principles, i.e., electrophoresis, field flow fractionation (FFF), adsorption (parametric pumping), or chemical reactions; and conducting the CD operation in space environments. The first two means would benefit still further from space environments. It is also concluded that the potential of the technique for separations of biological and other aqueous solutions has been largely overlooked. Furthermore, the CD principle appears to offer novel application such as solar water desalination, enery conversion devices, and a use for waste heat. In addition to presenting the mentioned critical reexamination and protential applications, the present document reviews the history and theoretical basis of the technique.