Alkali Metal Ion Partitioning with Calix[4]arene-benzo-crown-6 Ionophore in Acidic Medium: Insights from Experiments, Statistical Mechanical Framework, and Molecular Dynamics Simulations.

The current work reports the experimental and predicted interfacial behavior of metal ion extraction from aqueous phase-diluent system using a newly synthesized calix-benzo-crown-6 (CBCBGA) ionophore. Conductor-like screening model for real solvents was used to predict the selectivity at infinite dilution for the metal ion complexes in both aqueous and diluent phases. The selectivity for Cs-CBCBGA extraction was found to be higher than that of other metal ions, namely, K, Na, and Rb. This was confirmed by the experimental distribution coefficients obtained in the diluents system at 3 M HNO along with 0.01 M CBCBGA/organic solvents. The high selectivity of Cs-CBCBGA complex over other complexes (K, Rb, and Na) in nitrobenzene was also confirmed and validated by the highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap (i.e., 0.13114 > 0.12411 > 0.11719 > 0.11561 eV) and interaction energy (i.e., -68.25 > -57.11 > -55.52 > -52.37 kcal/mol). The interaction and free energies of the extraction were found to increase with the dielectric constant of the organic solvents, namely, nitrobenzene > o-nitrophenyl hexyl ether > 1-octanol > chloroform. Overall, a higher selectivity of Cs ion over that of other metal ions (K, Na, and Rb) was obtained for the newly synthesized CBCBGA ionophore in a radioactive waste solution.