Phase behavior and internal micro mechanism of separation acetonitrile from water by hydrophobic green solvents

As green solvents, deep eutectic solvents (DESs) have the advantages of low vapor pressure, non-toxicity, low cost, and broad application prospects in the field of azeotropic separation. In this work, lauric acid, capric acid and thymol were used as hydrogen bond donors to prepare four kinds of hydrophobic DESs for treating azeotropic systems in acetonitrile (MeCH) wastewater. The liquid-liquid equilibrium (LLE) data for Water - MeCH DESs system at 303.15 K and 1 atm were recorded. The extraction effects of different solvents were compared by measuring the distribution coefficient (beta) and selectivity (S). The data from molecular dynamics (MD) simulation were verified with the experiment results and the internal mechanism underlying the extraction of MeCH from water was studied. The interaction energy, radial distribution function (RDF) and spatial distribution function (SDF) of the DESs and water-MeCH system were obtained, which verified the feasibility of separating MeCH/water azeotropes from internal micro mechanism. The results of the MD simulation showed that hydrophobic DESs have a good extraction effect on MeCH, and the electrostatic force plays a leading role in the force between the DESs and MeCH. The feasibility of separating nitrile compounds from water and the subsequent treatment with DESs was verified. This study also provides a reference for further inter-laboratory research, and provides a simple, economical and environmental protection method for the monitoring and separation of similar substances related to environmental safety.

Automated summary

In this study, deep eutectic solvents (DESs) were used to treat azeotropic systems in acetonitrile wastewater. The performance of DESs in liquid-liquid equilibrium conditions was investigated through experiments and molecular dynamics simulations, confirming the feasibility of separating azeotropic mixtures using DESs and exploring the underlying mechanisms. The results showed that hydrophobic DESs had a good extraction effect on acetonitrile, with electrostatic force playing a leading role.