Across liquid surfactant membranes, alkali

Actinides, in nitric acid waste, 182 Advancing-front model, ELMs, 18,68 Alkali metal cations transport across bulk liquid membranes, 89-92 transport across liquid surfactant membranes, 93-95 transport across polymer-supported liquid, 95-96... 

An idealized schematic diagram of alkali metal cation transport across a liquid surfactant (emulsion) membrane by an lonizable crown ether is shown in Figure 7. Thus a metal cation is transported from an external aqueous source phase across the liquid surfactant membrane which forms the outer surface of the emulsion droplet into an interior aqueous receiving phase. Metal ion transport is driven by a pH gradient and back transport of protons from the internal to the external aqueous solution according to the mechanism illustrated earlier in Figure 1. In this system, transport is rapid due to the thin organic membrane. 

Figure 8. Influence of Polyether Ring Size Upon Competitive Transport of Alkali Metal Cations Across a Liquid Surfactant Membrane by (a) (b) 2, and (c) 3. (Adapted with permission...

In the present paper, we examine the influence of structural variation within series of crown ether carboxylic acid and crown ether phosphonic acid monoalkyl ester carriers upon the selectivity and efficiency of alkali metal transport across three types of liquid organic membranes. Structural variations within the carriers include the polyether ring size, the lipophilic group attachment site and the basicity of ethereal oxygens. The three membrane types are bulk liquid membranes, liquid surfactant (emulsion) membranes and polymer-supported liquid membranes. 

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