Extraction of alkali halides from their aqueous solutions by crown ethers

Abstract

Publication costs assisted by Israel Chemicals, Limited Potassium and sodium halides can be extracted from their aqueous solutions by dibenzo-18-crown-6 and dicyclohexo-18-crown-6 dissolved in protic solvents, which solvate the anions effectively. Both separate ions and ion pairs are extracted, the order of extractability among the halides being fluoride > iodide > bromide > chloride, apparently reflecting the solvation of the anions. The solubility of the crown ethers in a series of solvents are correlated with the solvent properties. The results are summarized in a prescription for selecting the best crown ether/solvent combination for effective extraction of the alkali halides.

The Removal of Cesium from Medium-Active Waste Solutions

“…The values for DB-21-C-7 and DB-24-C-8 are given as example in Table 3. This behaviour can be explained in agreement with other authors [11,12] by the insufficient solvation of anions in solvents of lower polarity. The extraction coefficients for nitromethane which are higher than those for nitrobenzene in spite of similar dielectric constants, may be attributed to the higher acceptor number [25] of nitromethane.…”

“…2). Thus, HN0 3 acts as salting-out reagent the high NO J concentration of which promotes the ion-pair formation [12,13] preceding the extraction. An appreciable extraction of HN0 3 does not take place at this concentration.…”

“…This may be attributed to the insufficient solvation of the anions by the organic solvent. Solvation is improved by adding alcohols, e. g. methanol, n-butanol [10], 2-ethylhexanol [ 11 ], or phenols such as nonylphenol [11], The use of protic solvents such as m-cresol or 2,4-dimethylphenol [12,13] leads to a better solvation, too. Essentially more effective extraction systems can be obtained by replacing the anions only slightly soluble in organic solvents by anions which are voluminous, more polarizable and less hydrophilic [10].…”

Theoretical Study on 15-Crown-5 Complex With Some Metal Cations

“…In addition to the nature of counter anion, the extraction of metal cations with neutral crown ethers also require the concomitant transfer of counter ionic species from the aqueous phase into the organic phase. Some improvement in extraction efficiency of metal salt by crown ether can be obtained by modification of the organic solvent medium [22], while the concomitant transfer of counter ionic species can be avoided by using proton-ionizable crown ethers [23][24]. So the result of this theoretical research in the gas phase is in line with the results of experimental research ever done before.…”

Extraction of cesium-137 from nitric acid medium in the presence of macrocyclic polyethers

“…Nitrobenzene was chosen as diluent as most of the benzo substituted crown compounds have appreciable solubility in it. 6 Heteropoly acids have been used for Cs extraction from pH conditions. 7 A combination of phosphotungstic acid with dibenzo 21 crown 7 have shown in an earlier report great promise for Cs extraction.S The combination of this reagent with DB18C6 was, therefore, employed for Cs extraction at lower acidities (<3M HNO3).…”