Study on the Extraction of Acetamiprid and Imidacloprid from an Aqueous Environment Using Menthol-Based Hydrophobic Eutectic Solvents: Quantum Chemical and Molecular Dynamics Insights

The current work reports on molecular dynamics (MD) and quantum chemical (QC) calculations for two pesticide systems through extraction from an aqueous environment. 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) at 298.15 K temperature and atmospheric pressure were adopted in our studies. The nonbonded interaction energy; radial, combined, and spatial distribution functions; and hydrogen bonding extent of various components were obtained via MD simulations that highlighted the enhanced and favorable interactions of the DES components with pesticides as compared to water. Further, transport properties, such as the mean squared displacement and diffusivity of compounds within the phases, were evaluated with the help of Einstein's diffusivity equation to obtain the affinity of the pesticides, namely, acetamiprid and imidacloprid, toward the DES-rich phase. The extractive characteristics of pesticides, such as the distribution coefficient (β), selectivity (S), and extraction efficiency (% EE), were calculated from the simulation and were fitted with the experimental data. The β values obtained by simulation were 8.67 and 6.25, respectively, and 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 CT from DES to the pesticide, and the NBO analysis 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 the pesticide. The DES–pesticide optimized clusters confirmed the interactions between the pesticide and the 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 simulations. The highest occupied molecular orbital–lowest unoccupied molecular orbital studies displayed the active sites involved in CT and interactive operations. This was confirmed by the structural findings of the MD simulation, which were initially validated by the experimental results.