Gibbs Energies of Transfer of Alkali Metal Cations between Mutually Saturated Water−Solvent Systems Determined from Extraction Experiments with Radiotracer ¹³⁷Cs

Abstract

Thermodynamic standard Gibbs energies of transfer of alkali metal cations related to Cs+ cation [DeltatG degrees*,(Cs+)-[DeltatG degrees*,(M+)] between several mutually saturated solvents of the type water-solvent were calculated from determined extraction exchange constants Kexch degrees,*(Cs+/M+). The used liquid-liquid extraction method with radioactive tracing by 137Cs permits attaining higher precision of the values as compared to the methods used up to now. The data for o-nitrophenyloctyl ether, 1,2-dichloroethane, and 1-octanol were compared with literature sources and recommended absolute values of DeltatG degrees,*M+) are reported. For dissociating solvents, the dependences of [DeltatG degrees,*(Cs+) - [DeltatG degrees,*(M+)] on Gibbs energy of hydration of an ion, DeltaGhydr degrees are straight lines either for four cations Cs+, Rb+, K+, and Na+ (nitrosolvents) or for three cations Cs+, Rb+, and K+ (1,2-dichloroethane and 1-octanol). The hydration of Na+ and still more of Li+ in the water-saturated organic phase is apparent from the results. This manifests for high-water-content equilibrium 1-octanol even in a reversal of the values [i.e., DeltatG degrees*,(Li+) being more negative than DeltatG degrees,*(Na+)], although for Cs+, Rb+, and K+, the general trend is conserved. Water-saturated 1-octanol is thus slightly less basic than water, but the overall selectivity is very low. For one studied nondissociating solvent, dioctyl sebacate, the trend of the dependences of log Kexch degrees,*(CsB/M+) on DeltaGhydr degrees is similar to that of Kexch degrees,*(Cs+/M+) for polar solvents, but different for different anions B, thus reflecting ion association in the organic phase.

Synergistic effect of dicarbollide anions in liquid–liquid extraction: a molecular dynamics study at the octanol–water interface

“…The more hydrophilic the cation, the highest amount of dragged water, possibly explaining why the free energies of transfer of Na + , K + , Rb + and Cs + dicarbollide salts from water to octanol are quasi-identical. 81 Formally, cation complexes like Eu(BTP) 3 3+ behave like a big cation, and their interfacial behavior depends on the nature of the oil phase, and on the presence of CCD À anions. In the absence of CCD À anions, the complex adsorbs at the octanol, as well as chloroform interfaces with water.…”

Molecular dynamics study of dicarbollide anions in nitrobenzene solution and at its aqueous interface. Synergistic effect in the Eu(iii) assisted extraction

“…It has a low miscibility with water, however, and has been used as a receiving phase in ion extraction. [23][24][25] Basically it differs in nature from chloroform or octanol and lacks the amphiphilic topology of fatty alcohols where dicarbollides can also be dissolved, and it will thus be interesting to compare these solvents. Furthermore, on the theoretical side, there have been Monte Carlo and MD reports on the structure of the NBZ liquid dry [26][27][28] or humid, 29 on the neat NBZ-water interface, 30 and on the corresponding migration and distribution of ions like NMe 4 + , 31 Ca 2+ 32 or TBA + Br À (tetrabutylammonium bromide).…”

The transfer of neutral molecules, ions and ionic species from water to wet octanol

“…As can be seen in Table 5, we have not used a number of values; either our descriptors or the experimental data must be 22 have determined log P ion (oct) relative to Cs + for the alkali metal cations. The variation of log P ion (oct) over the five cations is very small, as we find from literature data, and as we calculate, see Table 5.…”