TOPO-decanoic acid based DES – Structural insights using DFT, physico-chemical investigations and extraction efficiency of DES diluted with chloroform

Abstract

Deep eutectic solvents (DESs) are recently regarded as evolving candidates in the field of separation science in order to achieve sustainability. In the present work, hydrophobic TOPO-Decanoic acid DES has been synthesized and scrutinized by FTIR and 1HNMR studies. The structures of TOPO (Tri-octyl phosphine oxide), decanoic acid, chloroform, DES and DES + chloroform have been optimized employing B3LYP functional using DFT-D3 of Grimme’s method. The HOMO-LUMO (Eg) energy gap, bond lengths, mulliken charges,dipole moment and interaction energy has been evaluated using DFT. The geometry optimization provides the bond parameters which explain about the existence of non-bonded interactions. DES and DES + chloroform show more reactiveness as compared to its constituents evident from the chemical potential value. Physico-chemical properties such as density, volumetric (V), dielectric constant (ε), refractive index (nD) and ultrasonic velocity (U) of the hydrophobic TOPO-Decanoic acid DES diluted with polar cosolvent chloroform have been determined over a wide range of mole fraction of DES at 298.15 K. The excess properties such as VE, εE, nDE and UE have been calculated to predict the type of inter-molecular interaction existing within the components of the DES diluted chloroform mixture. Different mixing rules have been used to estimate properties such as dielectric permittivity, refractive index and ultrasonic velocity. Various acoustic parameters such as Z, βs, and (Lf)mix of binary mixtures are evaluated to predict about the presence of inter molecular interactions within the mixture components. The prepared hydrophobic eutectic mixture in chloroform has been further used for extraction of Y (III) and Eu (III). The solvent extraction of Eu (III) showed better performance as compared to that of Y (III).