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 HNO₃ 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 > <i>o</i>-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