Consideration on modeling of Nb sorption onto clay minerals

Sorption distribution coefficient (Kd) of niobium-94 on minerals are an important parameter in safety assessment of intermediate-depth disposal of waste from core internals etc. The Kd of Nb on clay minerals in Ca(ClO4)2 solutions were, however, not successfully modeled in a previous study. The high distribution coefficients of Nb on illite in Ca(ClO4)2 solutions were successfully reproduced by taking Ca–Nb–OH surface species into account. Solubility of Nb was studied in Ca(ClO4)2 solutions and the results were reproduced by taking an aqueous Ca–Nb–OH complex species, CaNb(OH)6+, into account in addition to previously reported Nb(OH)6− and Nb(OH)72−. Based on this aqueous speciation model, the Ca–Nb–OH surface species responsible for the sorption of Nb on illite in Ca(ClO4)2 solutions was presumed to be X_OCaNb(OH)6. Although uncertainties exist in the speciation of aqueous Ca–Nb–OH species, the result of this study proposed a possible mechanism for high distribution coefficient of Nb on illite in Ca(ClO4)2 solutions. The mechanism includes Ca–Nb–OH complex formation in aqueous, solid and surface phases.

Imidazolium-based dicationic ionic liquids: highly efficient extractants for separating aromatics from aliphatics

Imidazolium-based dicationic ionic liquids (DILs) are potential alternative solvents for the extraction of aromatics from aliphatics with both high selectivity and high distribution coefficient.

Ethylsulphate-Based Ionic Liquids in the Liquid–Liquid Extraction of Pyrrole and Pyridine from Isododecane at 298.15 K

Ternary liquid-liquid equilibria for four systems containing ionic liquids {1-ethyl-3-methylimidazolium ethylsulphate ([EMIM][EtSO4]) and 1-ethyl-3-methylpyridinium ethylsulphate ([EMPY][EtSO4])}(1)+pyrrole/pyridine(2)+isododecane (3) have been determined at 298.15 K. The solute distribution coefficient and selectivity were calculated from experimental LLE data. All systems showed high distribution coefficient and selectivity values at the entire range of pyrrole or pyridine in feed. The consistency of experimental data was ascertained by applying the Othmer-Tobias and hand equations. Furthermore, the experimental LLE data have been compared and correlated using COSMO-RS, NRTL and UNIQUAC models. The influence of aromatic structure without inside ring of cation has a significant role on denitrification process at 298.15 K.

Calciumisotopenseparation mit Kryptanden als Komplexbildner / Separation of Calcium Isotopes with Cryptand Complexes

The calcium isotope separation in the liquid-liquid extraction system H2O/CHCl3 is investigated using [2.2.1] and [2.2.2] cryptands for complex formation as well as without complexing agent. An extraction procedure is used which allows the transfer of larger amounts of calcium into the CHCl3 phase although the high distribution coefficient favours calcium in the H2O phase. Without complexing agent in the extraction system, enrichment of the lighter calcium isotopes is already evident in the CHCl3 phase which is just the same as when using [2.2.1] cryptand. In the case of [2.2.2] cryptand as a complexing agent, the isotope separation is higher. The separation factor is calculated to be α = 1 + ε = 1.011 for 40Ca/ 48Ca without complexing agent or with [2.2.1] cryptand and α = 1.015 in the system with [2.2.2] cryptand. For 40Ca/44Ca the ε-value is smaller by nearly a factor of two. These separation factors are the highest which are determined in chemical systems for calcium isotopes