Anion effect on selectivity in crown ether extraction of alkali metal cations

Journal Article · Wed Apr 21 00:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00061a062· OSTI ID:6299389

Olsher, U ^[1]; Hankins, M G; Kim, Youn Doo; Bartsch, R A ^[2]

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1. Weizmann Inst. of Sciences, Rehovat (Israel)
2. Texas Tech Univ., Lubbock (United States)

For the solvent extraction of metal ions and their transport across liquid membranes by neutral ionophores, concomitant transfer of one or more aqueous-phase anions into the organic medium is required for electroneutrality. The efficiencies of metal ion extraction and liquid membrane transport flux exhibit a pronounced inverse dependence on the solvation energy of the accompanying anion. Scattered literature reports suggest that the selectivity of metal ion extraction and transport by neutral synthetic and natural ionophores may also be affected by anion variation. To explore this possibility, the authors have determined the influence of anion variation in competitive alkali metal cation extractions from aqueous solutions into chloroform by cis-syn-cis-dicyclohexano-18-crown-6 (1). The anion effect in solvent extraction of alkali metal cations by 1 was assessed by extracting aqueous solutions of Li[sup +], Na[sup +], K[sup +], Rb[sup +], and Cs[sup +] (0.020 M in each) having a common anion with an equal volume of a 0.010 M chloroform solution of the crown ether. The series of aqueous-phase anions (bromide, iodide, nitrate, perchlorate, and thiocyanate) was chosen to include both hard (e.g., nitrate) and soft (e.g., thiocyanate) anions. The overall extraction efficiency decreases in the order: perchlorate > iodide, thiocyanate > nitrate > bromide. On the basis of the concentration of crown ether, the total extraction efficiency ranges from 63% for competitive extraction of the alkali metal perchlorates to only 1.0% loading for extraction of the alkali metal bromides. 26 refs., 3 tabs.

• DOE Contract Number: FG05-88ER13832
• OSTI ID: 6299389
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 115:8; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
ALKALI METAL COMPOUNDS
MEMBRANE TRANSPORT
SOLVENT EXTRACTION
ANIONS
CHLOROFORM
ETHERS
EXPERIMENTAL DATA
SOLUTIONS
CHARGED PARTICLES
CHLORINATED ALIPHATIC HYDROCARBONS
DATA
DISPERSIONS
EXTRACTION
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
IONS
MIXTURES
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
SEPARATION PROCESSES
400105* - Separation Procedures
400201 - Chemical & Physicochemical Properties
360606 - Other Materials- Physical Properties- (1992-)