Chapter 6: Micropollutants’ Extraction from Aqueous Systems Using Ionic Liquids and Deep Eutectic Solvents^†

This chapter reports on Molecular Dynamics (MD) and Quantum Chemical (QC) calculations for micropollutants’ extraction from aqueous environments. Two separate Deep Eutectic Solvents (DESs) consisting of dl-menthol as a hydrogen bond acceptor (HBA) and two carboxylic acids (octanoic acid and dodecanoic acid) as hydrogen bond donors (HBDs) were adopted. The noncovalent interactions, structural properties and hydrogen bonding extent via MD simulation highlighted the enhanced and favorable interactions of the DES components with the pesticides as compared to water. Further, transport properties elaborated the affinity of the pesticides, namely acetamiprid and imidacloprid, towards the DES-rich phase. The distribution coefficients (β) obtained by simulation were 8.67 and 6.25, respectively, and the selectivity (S) values were 102.38 and 71.86, for acetamiprid and imidacloprid systems, respectively. Within QC, the charge transfer (CT) process confirmed the direction of charge transfer from DES to pesticide and the NBO analysis and the HOMO–LUMO studies established the stable character of both the DESs. A slight increase in the O (HBA)⋯H (HBD) distance confirmed the increased interaction between the DES and pesticide. The DES–pesticide optimized clusters confirmed interactions between the pesticide and DES at a distance ranging from 2.896 to 3.77 Å for imidacloprid and from 1.724 to 2.03 Å for acetamiprid, which are validated by MD simulation.