Electromigration of ions

Electromigration of Ions movement of ions under an electric field. 

Figure 5 Configuration of capillary isotachophoresis. The arrangement shown is close to a real Instrument. The capillary is often made of plastic. The semipermeable membrane prevents electro-osmotic and hydrodynamic flows of the electrolyte but allows electromigration of ions. A conductivity detector is often used. It has miniature electrodes placed inside the capillary.

Figure 10.423 Electromigration of ions and flow directions in an ion reflux device.

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. 

Figure 7. Schematic representation ofprocesses of electromigration / diffusion of ions and formation of insulation passive layer on the boundary current collector / conductive polymer.

In this electroseparation type of chromatography (Fig. 8.8), electromigration of the ions is combined with adsorption effects which are characteristic of chromatography by using a capillary column (diameter 75 pm) filled with a stationary phase of very fine particles (1-3 pm). This can be done because of the absence of a pressure drop across the column. 

Electrodialysis (ED) is a unit operation for the separation or concentration of ions in solutions based on their selective electromigration through semi-permeable membranes under the influence of a potential gradient (Lacey and Loeb, 1972 Strathmann, 1992). Owing to their selectivity, ion-exchange membranes (IEM) allow transport of only cations (cation-exchange membranes) or anions (anion-exchange membranes) and thus can be used to concentrate, remove, or separate electrolytes. 

W.R. Walters D.W. Weisner and L.J. Marek, Concentration of Radioactive Aqueous Wastes Electromigration Through Ion-exchange Membranes, Ind. Eng. Chem. 47, 61 (1955). 

Okamoto, M. et al., Dependencies of pH and current density on the isotope effect occurred by the electromigration of uranyl ions in a... 

Fig. 4 Imposing an electrical potential gradient across a charged membrane produces a convective solvent flow in the direction of counter-ion transport (i.e., from anode-to-cathode in the case of skin). This electroosmotic effect (EO) adds to electrorepulsion (ER) to enhance the transport of cationic compounds during iontophoresis (4a) while acting against the electromigration of anions (4b).

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