Organic liquid membrane, proton-coupled

To take advantage of the attractive features of proton-coupled transport, we (9-12) and others (14-17) have utilized crown ether compounds with pendant carboxylic acid groups. The mechanism of proton-coupled transport of a monovalent metal cation across an organic liquid membrane is illustrated in Figure 1. Thus the carrier, which remains in the organic membrane, is deprotonated at the organic phase-alkaline aqueous source phase interface and complexes the metal cation (Step 1). The electroneutral complex... 

The performance of calixarenes as cation carriers through H20-organic solvent H20 liquid membranes has also been studied.137 In basic metal hydroxide solutions, the monodeprotonated phenolate anions complex and transport the cations, while [18]crown-6 does not, under the same conditions. Low water solubility, neutral complex formation and potential coupling of cation transport to reverse proton flux have been cited as desirable transport features inherent in these molecules.137... 

Isotherms for the interfacial tension at an aqueous/organic interface show that the new di-(p-alkylphenyl)phosphoric acids 3-6 adsorb at the interface stronger than do commercially available DEHPA (1) or Cyanex 272(2). From the interfacial fluxes for single transition metal cation species transport across a bulk kerosene membrane, the following selectivity orders were derived Zn(II) > Cu(II) > Co(II) > Ni(II) for 1, 5, and 6 Cu(II) > Zn(II) > CoJI) > Ni(II) for 2 and 3 and Cu(II), Zn(II) > CoJI) > Ni(II) for 4. Similar selectivity orders were observed in competitive transport of these transition metal cations across emulsion liquid membranes in which a high utilization degree of the carrier was demonstrated. The di-(p-alkylphenyl)phosphoric acids 3-6 are found to be efficient carriers for proton-coupled transport of transition metal cations from a weakly acidic aqueous source phase across an emulsion liquid... 

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