Studies On The Separation Performance Of Ionic Liquids And Their Interactions With Solutes

As a class of novel mediums and functional materials, ionic liquids have obtained remarkable achievement in green chemistry during recent ten years. Ionic liquids exhibit many interesting properties such as nonvolatile, nonflammable, broad liquid range, superior solubility and tunable properties, and their application has been extended into areas of chemical synthesis, material innovation, environmental science, separation technology, and biocatalysis. The unique physicochemical properties and potential industrial applications drive the rapid development of ionic liquids researches.As a part of the project supported by the National Nature Science Foundation of China (No. 20573034), this thesis deals with the separation performance of ionic liquids and their interactions with dyes, amino acids, proteins, and organic pollutants. The main contents are as follows:1. The equilibrium partitioning of anionic dyes (methyl orange, orange G, eosin yellow) between ionic liquids and water was studied systematically. Different experiments designs were used to analyze the effect of equilibrium time, pH values, temperature, structure of ionic liquids, and addition of salts on the partitioning of the dyes. The main driving force for the transfer of dyes from water to the ionic liquids was examined from a thermodynamic study. Based on these results, an approach has been suggested for dyes wastewater pollutant control.2. Formation of a new ionic association species was observed between cation of the ionic liquids and anion of the cationic dyes (methylene blue and malachite green). The composition and equilibrium constant of the association species were determined by spectroscopy and conductometry. The association species was used, as active material, to prepare ionic selective electrode. Detailed experiments were conducted to optimize the composition of plasticizer, ionophore, and ionic additives of the electrode. The optimal electrode was successfully used to determin the concentration of ionic liquids in aqueous solutions, at the level of 10^-6 mol·L^-1, by determination of anionic concentration of the ionic liquids.3. The binodal curves and tie line length were determined for aqueous two-phase systems based on the hydrophilic ionic liquids ([C₄mim]Cl, [C₆mim]Cl, [C₄mim]Br, [C₆mim]Br, [C₈mim]Br, [C₁₀mim]Br) and salts (KOH, K₂HPO₄, K₃PO₄, K₂CO₃) at 298.15K. The partitioning of amino acids (tryptophan, tyrosine, Phenylalanine, leucine, and valine) was studied in both aqueous two-phase and hydrophobic ionic liquids - water systems. The interaction between amino acids and ionic liquids were analyzed in detail. The effect of pH values, structure of amino acids and ionic liquids, the component concentration of aqueous two-phase system on the partitioning of amino acids were also examined. Finally, a green separation process based on ionic liquids was proposed.4. Ionic liquid-based aqueous two-phase systems have been employed for extraction of proteins (bovine serum albumin, lysozyme, cytochrome c, trypsin, andγ-globulins). Partition coefficients and the related transfer thermodynamic parameters were determined. The possible structure change information of proteins in ionic liquid-rich phase was probed by UV-visible and Fourier transform infra-red spectroscopy. The enzyme activity of trypsin in ionic liquids solution was determined by the Nα-Benzoyl-L-arginine ethyl ester hydrochloride method.5. Thermodynamic parameters were determined for the transfer of some organic pollutants (phenols, phenyl amines, furfural, and 5-methylfurfural) at 298.15K. The effect of pH values, temperature, structure of organic pollutants and ionic liquids, concentration and type of added salts on the organic pollutants partitioning was also investigated. A green separation method was proposed for the organic pollutants removal by ionic liquids.