Aqueous solutions, electromigration

The progress achieved in the field of isotope electromigration in metals, salts, and aqueous solutions since the meeting on isotope separation in Paris in 1963 is reported. It is shown that the temperature dependence of the isotope effect in liquid metals leads to the conclusion that it is a result of classical atom—atom interactions. Isotope effects in molten salts are smaller than in classical ionic gases. A three stage model is proposed for an explanation of the temperature dependences of the isotope effects in molten salts. The available data of the relative difference in mobilities of isotopes in aqueous solutions are summarized. 

In the last few years isotope separation in aqueous solutions by counter-current electromigration has found renewed interest. The reason for this renaissance is the hope that isotope effects in dissociation equilibria might substantially increase the effective relative difference in mobilities and make aqueous solutions a medium for a successful separation of isotopes. In this review we have summarized the available relevant data. 

In reversed-phase liquid chromatography (RPLC) and electromigration techniques (CEC, CZE), aqueous solutions of methanol, acetonitrile, tetrahydrofu-ran, and dioxane are used as eluents. In this mode of LC, a fundamental concern is the pruity of water, which can contain phenols, hydrocarbons, etc. Tetra-hydrofuran is used frequently as the solvent in gel permeation chromatography. It must be stabilized by butylated hydroxytoluene used as antioxidant. Similarly, when halogenated solvents (e.g., trichloroethylene) are used triethanolamine is added as a... 

Milanov, M., Roesch, F., Khalkin, V.A., Henniger, U., and Hung, T.K, (1987) Electromigration of ions of radionuclides without carriers in electrolytes. Hydrolysis of Bi(III) in aqueous solution. Radiokhimiya, 29, 21-28. 

Qualitative observations on the nature of the soluble aqueous species present in sulfate solutions indicate that sulfate complexes are much more stable than perchlorate, chloride or nitrate complexes (383). Electromigration studies at SO4 Zr ratios greater than 1 1 show that anionic sulfate complexes are formed (384). In spite of complexing by sulfate, hydrolysis does occur (4S4) and metal polymeric hydroxy species are formed (393) in 0.006 M zirconium solutions. 

The solution of these equations subject to the boundary conditions must generally be carried out numerically although the procedures are not described here. Two limiting cases are one in which electroosmosis is the dominant removal mechanism for the dissolved contaminant and one where electromigration is the principal removal mechanism. The removal of aqueous soluble organics would be principally by electroosmosis, and the removal of soluble metal ions would be mainly by electromigration. 

Electromigration of carrier-free radionuclides. 5. Ion mobilities and hydrolysis of Np(V) in aqueous perchlorate solutions. Radiochim. Acta, 42, 43-46. Runde, W. and Kim, J.L (1994) Chemical Behaviour of Trivalent and Pentavalent Americium in Saline NaCl-Solutions. Studies of Transferability of Laboratory Data to Natural Conditions. Report RCM-01094, Technische Universitat Miinchen, 236 pp. Runde, W., Neu, M.P., and Clark, D.L. (1996) Neptunium(V) hydrolysis and carbonate complexation experimental and predicted neptunyl solubility in concentrated NaCl using Pitzer approach. Geochim. Cosmochim. Acta, 60, 2065-2073. 

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