Application Of Hydrophobic Deep Eutectic Solvents In Separation Of Aqueous Azeotrope

In recent years,designable deep eutectic solvents(DES)composed of hydrogen bond donors(HBDs)and hydrogen bond acceptors(HBAs)have been used as new green solvents.The synthesis and related applications of DESs and hydrophobic DESs(HDESs)have received increasing attention from researchers.Their components are mostly natural biological components and organic acids,which have established their non-toxic properties.Therefore,they meet the requirements of many solvents toxicity treatment methods in terms of environmental safety and biomass treatment.Compared to other traditional organic solvents and most ionic liquids,DESs and HDESs have advantages in different viscosities,densities,and their acidity.Its advantages in acidity,alkalinity,and volatility make it an alternative solvent with great development potential.Their advantages of low volatility,non-toxicity,and environmental protection make them more in line with the high standards for environmental governance and waste liquid treatment applications than traditional solvents and ionic liquids,meeting the feasibility of achieving green solvents.By changing the components of HBDs and HBAs to form solvents with different properties,the designability of the extraction solvents can be satisfied and the targeted analyte can be extracted directionally to meet the experimental requirements under specific conditions.The corresponding DESs were prepared and characterized using menthol,thymol terpenoids,and long carbon chain carboxylic acids as HBAs and HBDs,respectively.The experimental data of the DESs-acetonitrile-water,DESs-tert butanol-water,and DESs-isopropanol-water systems were determined by liquid-liquid extraction at298.15 K and 1 atm atmospheric pressure,the distribution coefficient(β)and selectivity(S)of the azeotrope system in the DESs and water phases were calculated.Based on experiments,molecular dynamics(MD)was used to simulate the entire extraction and separation process.The interaction in the microscopic perspective of the extraction and separation process was clarified through calculation of interaction energy,radial distribution function,spatial distribution function,and self-diffusion coefficient.The separation effects of different DESs on acetonitrile-water,tert butanol-water,and isopropanol-water systems were clarified,The law and mechanism of extracting and separating low alcohol azeotropes and other compounds with similar properties from water by hydrophobic DESs were revealed.The experimental results from the liquid-liquid equilibrium(LLE)experiment show that the hydrophobic DESs used in this work can effectively separate the azeotrope of acetonitrile(Me CH)-water and lower alcohol-water.From the distribution coefficient and selectivity,it can be seen that its value is much greater than 1,which proves that HDESs can better extract and separate lower alcohol azeotropes and other compounds with similar properties in the experiment.In the experiment of extracting and separating acetonitrile,Thymol: Capric acid(1:1)has the best extraction efficiency among the four DESs,and reveals that the interaction between HBAs and Me CH dominates.For the study of extraction of low carbon alcohol,using menthol as HBA and octanoic acid,decanoic acid,and lauric acid as HBDs,DESs were synthesized to explore the performance of extraction and separation of tert butyl alcohol.The non random two liquid model(NRTL)was applied to linearly corrected LLE experimental data,and the root mean square difference was less than 2%,demonstrating the applicability of the model.At the same time,combining experiments and MD simulation,it is proved that the DES formed by menthol and capric acid has the best extraction effect,and the extraction performance of the extractant is inversely proportional to the concentration composition of the azeotrope.On this basis,the extraction performance of three different HDESs,menthol,thymol,and geraniol combined with decanoic acid,was investigated for the extraction of isopropanol,and the best extraction solvent was selected.The optimal ratio and conditions were determined through experiments at different compositions and temperatures,and the interaction and mechanism between the components were analyzed.Therefore,this work verifies that HDESs provide a simple,economical,and environmentally friendly protection scheme for treating low alcohol azeotropes and other compounds with similar properties in water.Molecular dynamics simulation can be applied to the safe treatment of azeotrope resource recovery,and can be used as a reference standard for solvents selection,providing a research basis for extraction at the micro mechanism level.