Study On The Construction And Application Of Imidazolium Ionic Liquid Aqueous Two-phase System

Aqueous two-phase extraction is a new liquid-liquid extraction technology.Compared with the traditional extraction and separation technology,it has many advantages such as simple operation,strong controllability,low energy consumption and easy amplification.It has been widely used in biological,chemical and other fields.Ionic liquid aqueous two-phase system?ILATPS?is developed on the basis of the aqueous two-phase system?ATPS?and combines the advantages of ionic liquids and aqueous two-phase systems.In fact,ionic liquids?IL?are known for their two major features:‘green'?no pollution?and‘designable'?anionic and cationic combinations?.These two highlights make the ionic liquid two-phase system applied to the separation and extraction of various substances.Amino acids,proteins,and phenolic compounds are three types of substances that play a very important role in the metabolism of organisms.The traditional separation methods have some disadvantages,such as the use of organic solvents,cumbersome process,time-consuming and laborious and other shortcomings.Therefore,it would be very meaningful to study the extraction of these three types of materials with ILATPS.In this thesis,a polymer/inorganic salt/ionic liquid aqueous two-phase system was firstly constructed,and the distribution of L-phenylalanine in the system was studied.Then the system was used to extract papain,the influence of various factors on the extraction rate of papain was studied and the mechanism of extraction was studied.Finally,the system was upgraded to an ionic liquid/inorganic salt aqueous two-phase system.The extraction of syringic acid in the system was studied and an ionic liquid recovery system was constructed.The main research contents and results are as follows:?1?The PEG600/NaH₂PO₄/IL aqueous two-phase system was constructed and the phase diagram of the system was studied.The system that composed of 40wt%PEG600+12wt%Na H₂PO₄·2H₂O+44wt%H₂O+4wt%IL to extract L-phenylalanine.The effects of temperature and ionic liquid on the extraction of L-phenylalanine in aqueous two-phase system were investigated.The results show that amino acids are mainly extracted into the polyethylene glycol rich phase.The partition coefficient(K_Phe)of L-phenylalanine and the partition coefficient of the ionic liquid(K_IL)in the syste m are t he s ma llest w he n I L is 1-decyl-3-methylimda zo lium c hlor ide([C₁₀mim]Cl),K_Phe=1.457±0.064,K_IL=0.567±0.087.When IL is 1-octyl-3-methyl-imidazolium chloride?[C₈ mim]Cl?,both K_Phe and K_IL are maximal,K_Phe=5.403±0.109,K_IL=13.587±0.25.The enrichment trend of ionic liquids in the aqueous two-phase system is basically consistent with the enrichment trend of L-phenylalanine in the aqueous two-phase system.The results of thermodynamics show that the enrichment process of L-phenylalanine to polyethylene glycol is a spontaneous exothermic process,and the enthalpic changes are the main driving forces ruling the amino acid partitioning.Addition of a little ionic liquid?4wt%?in the PEG600/NaH₂PO₄ aqueous two-phase system can significantly improve the amino acid distribut ion.?2?The PEG400/NaH₂PO₄/IL aqueous two-phase system was constructed and the phase diagram of the system was drawn.The effects of salt concentration,polymer concentration,ionic liquid type,ionic liquid concentration and other factors on the extraction of papain in aqueous two-phase systems were investigated.Finally the best ionic liquid and the optimal concentration of the components were selected for extraction.In addition,the samples were scanned and determined by UV,FTIR,DLS and CD,the structural changes of papain after two-phase extraction were studied.The results showed that the optimum system composition for extracting papain was20 w t%P EG4 00+24%N a H₂ PO ₄·2 H₂ O+4 w t%[C ₄ m im]C l?1-b ut y l-3-me t hy-limidazolium chloride?and the optimal extraction temperature was 318.15 K,and the optimal protein extraction concentration was 5mg/mL.The extraction rate of papain in the aqueous two-phase system was 92.47±1.65%,and K_Papain=2.14±0.13 with these conditions,the extraction rate was 72.45±1.76%,K_Papain=1.27±0.15 without ionic liquid.UV and FTIR spectra showed that there was no chemical reaction between ATPS and protease.DLS analysis showed that the addition of a small amount of ionic liquid led to a decrease in the average particle size and dispersion of the entire system,papain was more stable and homogenous in the system.CD analysis showed that when 4wt%of[C₄ mim]Cl and[C₈mim]Cl were added,the?-helix ratio of papain was reduced by about 2%,while the?-sheet ratio of papain was increased by 4.1%and2.1%respectively.There is a slight increase both?-helix ratio and?-sheet ratio of papain when IL is the[C₄mim]OAC?1-butyl-3-methylimidazolium acetate?.?3?The ionic liquid/inorganic salt aqueous two-phase system was constructed.The effects of salt type,concentration,concentration of IL on the distribution of syringic acid in ILATPS were investigated.The composition of the system that is most favorable for extraction of syringic acid was selected and further designed for the recovery of ionic liquids and the back extraction of syringic acid.The test results show that the optimal composition of the extraction system is 25wt%[C₄ mim][CF₃SO₃]?1-butyl-3-methylimidazolium trifluoromethanesulfonate?+20wt%Na₂SO₄?sodium sulfate?and 20wt%[C₄mim][CF₃SO₃]+10wt%Na₂CO₃?sodium carbonate?,the optimal extracttemperature is 298.15 K,the optimal concentration of syringic acid is3×10^-3mol/L,the extraction rates were 96.66±1.01%?Na₂SO₄?and 95.11±0.87%?Na₂CO₃?.Syringic acid is mainly extracted to the ionic liquid-rich phase when the salt is Na₂SO₄;however,when the salt is Na₂CO₃,syringic acid is mainly extracted to the inorganic salt-rich phase.The recovery system is that[C₄ mim][CF₃SO₃]+Na₂SO₄is used to extract syringic acid to the ionic liquid phase as the first step,and the second step is to extract syringic acid to the salt phase with[C₄mim][CF₃SO₃]+Na2CO3 to recover the ionic liquid and back extraction of target.The syringic acid was extracted again with the recovered ionic liquid,the extraction rates were higher than 93.34%,which proved that the properties of the recovered ionic liquid have not changed.The same system was used to extract the caffeic acid,and the extraction efficiencies was over 96%;the recovery of the ionic liquid could also be achieved.