Solvent Extraction of Alkali Metal Cations

Whether the solvated cation and the solvated anion are dissociated in the organic phase or form an ion pair K CwCr(SH) depends primarily on the permittivity of this solvent (see Section 3.2.3). Substituted phenols were proposed by Marcus and coworkers [45 7] for this purpose. 4-Fluorophenol is the best solvent in combination with DB-18-C-6 for the selective extraction of KCl from aqueous solutions according to Marcus et al. [47]. 

The selective extraction of Cs (with particular regard to the removal of fission product Cs from active nuclear waste) was effectively achieved by the use of the large dicarbolide anion (cobalt bis(dicarbolide), [(l,2-C2B Hjj)2-3-Co]). The history of the use of this anion for the solvent extraction of alkali met cations from aqueous solutions was reviewed by Kyrs [48] and its subsequent development by Rais and Gruener [49]. 

A comprehensive paper on the distribution of alkah metal and ammonium cations between mutually saturated liquids (water and an organic solvent) is that by Rais and Okada [50]. Contrary to the data in Table 4.2, which pertain to pure water and neat nonaqueous solvents, the data for quite immiscible but stiU mutually saturated phases can be obtained from distribution and electrochemical data. The latter provide the standard ionic distribution potential, A (p °(/), usually obtained from cyclic voltammetry, the asterisk denoting an abbreviation of where o(a) and a(o) 

The exchange equilibrium constant T (Cs/M) involves a solution of cesium dicarbolide, denoted by CsB, dissolved in the organic phase contacted with an aqueous solution of the cation M and some hydrophilic anion, such as nitrate, for exchange partition equilibrium to be attained, at which stage K (Cs/M) = K °The values of A G (7) for two solvents, 

0- nitrophenyl octyl ether and 1,2-dichloroethane, at 25°C are shown in Table 8.5 for the univalent cations M studied by Rais and Okada [50]. Exchange constants, log 7C JCs/M), were also reported for these ions for the solvents 1-nitropropane, 

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