Jerzy Strzelbicki

Transport of alkali metal cations across liquid membranes by crown ether carboxylic acids

Abstract Competitive alkali metal transport from an alkaline aqueous source phase through a chloroform phase to an acidic aqueous receiving phase facilitated by nine crown ethers with pendant carboxylic acid groups has been investigated. Transport selectivity is controlled by the size of the polyether cavity of the carrier. Increasing the lipophilicity of the carrier, while maintaining a constant polyether cavity size, enhances the total transport rate but does not affect the selectivity. There is poor agreement between the results of competitive transport and the behavior anticipated on the basis of single cation transport studies.

Solvent extraction of alkali metal cations from aqueous solutions by crown ether carboxylic acids

Abstract Competitive solvent extractions of alkali metal cations from aqueous solutions by the crown ether carboxylic acids sym-dibenzo-13-crown-4-oxyacetic acid, 2; sym-dibenzo-19-crown-6-oxyacetic acid, 3, and sym-dibenzo-14-crown-4-oxyacetic acid, 4, in chloroform have been conducted. Influences of aqueous phase pH and metal ion concentrations upon the concentrations of metals and complexing agent in the organic phase are assessed and compared with those reported for sym-dibenzo-16-crown-5-oxyacetic acid, 1. Extraction selectivity orders of K > Rb > Na ≍ Cs > Li, K > Rb ≥ Na ≍ Cs > Li, and K > Na > Rb > Cs ≍ Li were found for extractions using 2, 3, and 4, respectively. In terms of selectivity and metal extractability, 3 surpasses 1, 2, and 4.

Crown Ethers in Separation of Alkali Metal Cations1

Strzelbicki, J., Strzelbicka, B., Schugerl, K. and Bartsch, R. A., 1990. Crown ethers in separation of alkali metal cations. Proceedings of the International Solvent Extraction Conference 1990, Kyoto, Japan, July 16 - 21, 1990. Results are presented on separation of alkali metal cations (AMC) using a protonionizable and a neutral crown ether. sym-(Decyl)dibenzo-16-crown-5-oxyacetic acid was used as a selective ion-carrier in separation of Na+ from a mixture of Li+, Na+, K+ and Rb+ by means of hollow fiber supported liquid membranes. Selectivity of the permeation was very high. No Rb+ was transported in the system and Na/Li and Na/K selectivity coefficients reached 80 and 42, respectively. Expensive and/or commercially unavailable compounds involved and complicated operation were disadvantages of this process. In separation of AMC by liquid-liquid extraction, mixtures of dicyclohexano-18-crown-6 with di(2-ethylhexyl)phosphoric acid or with di(2-ethylhexyl)monothiophosphoric acid were used for complexation of AMC and their transfer into an organic phase. Selectivity of one stage liquid-liquid extraction was lower compared to liquid supported membrane process. On the other hand, reagents used in solvent extraction are commercially available, relatively inexpensive and the process is simple to perform.

Separation of Alkali Metal Cations by Polymer-Supported Liquid Membranes Using Ionizable Crown Ethers12

Strzelbicki, J., Strzelbicka, B., Lubboch, E. and Bartsch, R. A., 1990. Separation of alkali metal cations by polymer-supported liquid membranes using ionizable crown ethers. Proceedings of the International Solvent Extraction Conference 1990, Kyoto, Japan, July 16 - 21, 1990. sym-(Decyl)dibenzo-16-crown-5-oxyacetic acid (1) and sym-(decyl)dibenzo-16-crown-5-oxymethylphosphoric acid monoethyl ester (2) were tested as ion carriers for selective transport of alkali metal cations through polymer-supported liquid membranes. Influence of an ionizable group, temperature, organic membrane solvent, and the pH of the aqueous source solution on metal cation permeation was investigated. It was found that sodium cation was selectively transported from the aqueous mixture of Li+, Na+, K+ and Rb+. Selectivity and rate of permeation were strongly influenced as well by the molecular structure of an ion carrier as by process variables. The highest selectivity was obtained with 1. The permeation rate increased with increasing temperature and it was slower if n-octyl 2-nitrophenyl ether was used as solvent in the organic phase compared to n-pentyl 2-nitrophenyl ether. No remarkable influence of the pH of the source solution on Na+ transport rate from basic solutions was found.