Binary Mixture of TOPO-DA DES and Dichloromethane: Physicochemical–Structural Aspects and Extraction Scrutiny of Eu (III) /Y (III)

Deep eutectic solvents (DESs), consisting of a mixture of two compounds, are emerging as a new generation of solvents. The binary mixture of hydrophobic DES based on tri-n-octylphosphine oxide (TOPO) and decanoic acid (DA), and its mixture with dichloromethane (DCM), has been considered in the present study to know about the molecular interaction that exists in the system based on their physico-chemical properties and DFT analysis. Its use for the extraction of europium and yttrium has been examined. In this connection, the density, molar volume, apparent molar volume, dielectric constant, refractive index, and ultrasonic velocity and their excess properties have been determined. It has been observed that on increasing the mole fraction of DES density and dielectric constant of the mixture decreased, while values of molar volume, volume fraction, apparent molar volume, refractive index, and ultrasonic velocity increased. The observed properties ensure that weak interactions, such as nonspecific or hydrogen bonding, exist in the binary system. The interaction between TOPO-DA DES and dichloromethane is weak, as observed from DFT analysis in terms of interaction energy. FTIR and Raman spectral studies show a slight shifting of peaks, supporting weak interaction. Binary mixture of DES + DCM shows better extraction efficiency with europium than with yttrium.