Studies On The Law Of Organic Acids And Bases Extracted By Ionic Liquids

This thesis investigated the extraction ability and driven forces of a series of hydroxyl,benzyl,ether and dialkyl functionalized ionic liquids（ILs）for organic acids and alkaloids.The main contents and results are as follows:（1）A series of hydroxyl,benzyl and dialkyl functionalized ILs were synthesized.Effects of aqueous pH value,salt added,phase volume ratio and the chemical structures of the ILs on the extraction efficiency of the three antioxidants,gallic acid（GA）,vanillic acid（VA）and syringic acid（SA）have been investigated.The experimental results indicated that the extraction ability of the ILs highly depended on their chemical structures and the hydrophobicity of the three acids.For the ILs with perchlorate（ClO₄^?）as anion,the introduction of hydroxyl group on the cation improved significantly the extraction ability of ILs for GA,but had no effects on the extraction process of VA and SA.For the extraction of VA and SA,the hydrophobic interaction between ILs and VA or SA should also be considered.The contribution ofπ–πstacking between ILs and organic acids to the extraction efficiencies can be neglected.Thermodynamic analysis confirmed that hydrogen bonding was the main driving force underlying the transfer of the three acids from water to the IL phase.The three acids and ILs could be recovered and recycled,respectively by taking the advantage of pH dependence of the extraction efficiencies.These results suggested the ILs containing perchlorate anion exhibited potential applications in extraction of the three antioxidants from aqueous phase.（2）A series of hydroxyl,benzyl and dialkyl functionalized ILs were synthesized and their extraction abilities for inapic acid（SA）,ferulic acid（FA）,caffeic acid（CA）and p-coumaric acid（p-CA）in the aqueous solution were investigated.The experimental results suggested that the extraction efficiencies of the four hydroxycinnamic acids were significantly influenced by the pH values,salt added,phase ratio,and the chemical structures of the ILs.The ILs with CF₃SO₃^-anion had higher extraction ability for hydroxycinnamic acids because of the stronger hydrogen-bonding strength of CF₃SO₃^-.The combination of cation and anion,both of which have strong hydrogen-bonding ability,generates a hydrogen-bonding-functionalized IL,[C₄C₁₁OHim]CF₃SO₃,which has strongest hydrogen-bonding ability and strongest extraction ability for hydroxycinnamic acids.Thermodynamic analysis suggested that hydrogen-bonding interaction was the major driving force;meanwhile,the influence of hydrophobic interaction and steric hindrance between ILs and hydroxycinnamic acids should be considered when interpreting the extraction behavior of ILs.（3）A series of dialkyl functionalized ILs were synthesized and their extraction abilities for two alkaloids,quinine and gramine were investigated.Effects of aqueous pH value,phase volume ratio,concentration of two alkaloids and the chemical structures of the ILs on the extraction efficiency have been investigated.The experimental results suggested that the extraction ability of ILs had no clear relationship with the alkyl chain length on the IL cation and depended on the hydrophobicity and hydrogen-bonding strength of the IL anion.The CF₃SO₃^--based ILs were stable against hydrolysis and exhibited better extraction ability for the two alkaloids.Thermodynamic analysis suggested that the extraction of the two alkaloids was an entropy-driven process.（4）A series of ether and dialkyl functionalized ILs were synthesized.Effects of aqueous pH value,phase volume ratio,concentration of alkaloid and the chemical structures of the ILs on the extraction efficiency of hordenine have been investigated.Experimental results indicate that the ether-functionalized ILs possess stronger extraction ability than the dialkylimidazolium-based ones.Driving forces of the extraction processes include hydrogen-bonding interaction,hydrophobic interaction and steric hindrance effect.The extraction efficiency is highly dependent on the pH of aqueous phase.The recovery of hordenine from the IL phase and the recycling of the IL phase can be realized by using the pH swing effect.