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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. |
