【作者】 于飞；

【导师】 李德亮；

【作者基本信息】 河南大学 ， 环境科学， 2011， 硕士

【摘要】 随着现代工业的发展,极性有机物稀溶液的分离成为一个普遍的问题。可逆络合萃取法对极性有机物稀溶液的分离具有高效性和高选择性,受到越来越多研究者的关注。两性化合物同时具有Lewis酸和Lewis碱两种官能团,具有独特的化学、物理和生物性质,而被广泛的应用于化工、生物、制药等领域。在大量文献调研的基础上,本文选用三烷基胺(7301)为络合剂和7301+磷酸三丁酯(TBP)为萃取剂,采用络合萃取法对一类典型的两性有机物——吡啶甲酸[2-吡啶甲酸、3-吡啶甲酸(烟酸)和4-吡啶甲酸(异烟酸)]进行了较系统的研究,考察了络合剂浓度、稀释剂的种类、水相平衡pH值及溶质浓度对萃取平衡的影响；并在此基础上利用红外光谱推测萃取过程中的反应机制,建立了反应数学模型；根据大量的实验数据,找出影响萃取平衡的主要因素。结果表明：极性稀释剂有利于7301对吡啶甲酸的萃取；分配比在7301的浓度为0.4218mol/L时有最大值；随着水相平衡pH值的增大,分配比在溶质的中性分子(或两性离子)和阴离子区域内出现峰值；增大溶质吡啶甲酸的浓度,分配比降低。采用傅里叶红外光谱法对正辛醇体系中,吡啶甲酸、萃取剂及负载溶质的有机相进行分析,发现：在正辛醇体系中,吡啶甲酸可以通过与正辛醇之间的氢键作用直接进入有机相,与有机相本体中的7301反应；7301主要与吡啶甲酸中性分子(或两性离子)和阴离子发生反应,生成相同结构的离子缔合物,且水相平衡pH不影响7301和吡啶甲酸形成的萃合物的结构。在实验研究的基础上,根据pH对萃取平衡的影响和萃合物的结构,对7301/正辛醇+吡啶甲酸体系,同时考虑化学萃取和物理萃取作用,建立了分配比的表达式,并拟合出表观反应平衡常数K值。结果表明,模型拟合的精度是令人满意的。络合剂的表观碱度、稀释剂的极性及溶质的电性参数pKa和疏水性参数logP是影响萃取平衡的重要因素,并且对其与logK进行了关联。结果表明,在所研究的体系中,电性参数pKa和疏水性参数logP是造成吡啶甲酸分配比产生差异的主要原因。针对吡啶甲酸稀溶液体系,本文还采用7301+TBP混合络合剂体系对其进行了相平衡实验研究。结果表明,混合萃取剂7301+TBP对吡啶甲酸具有明显的协萃效应。混合萃取剂中,7301或TBP的浓度对萃取平衡影响较大；最大分配比出现在吡啶甲酸中性分子和阴离子区域；经红外光谱证实,协同-络合萃取过程中同时存在7301、TBP对溶质的络合反应和混合萃取剂对溶质的协同效应；萃取体系存在7301和TBP的最适宜比值,此时分配比较大；与7301络合萃取吡啶甲酸的过程一样,分配比随着吡啶甲酸的浓度的增大而减小更多还原

【Abstract】 With the development of the modern industry, the separation of polar organic species from diluent solution has become a widespread problem. As a highly effective and highly selective mothod for separating polar organic species, reactive exrraction has been received great attention.Amphoteric compounds, which contain two typical functional groups of Lewis acidic and Lewis basic groups, possess of particular physical, chemical and biological properties. They are widely used in the fields of chemical engineering, biological engineering, and pharmaceutical engineering etc. In the present thesis, reactive extractions of a kind of amphoteric compounds, namely pyridine carboxylic acids including picolinic acid, nicotinic acid and iso-nicotinic acid, using trialkylamine (7301) and 7301/tributylphosphate (TBP) as extractants, were systematically studied. The effects of concentration of extractants, diluents, equilibrium and initial concentration of pyridine carboxylic acids on distribution coefficient (D) were discussed. The mechanisms of 7301 reacting with pyridine carboxylic acids were deduced by Fourier Transformation infrared spectrometry. Also expressions of equilibrium D were proposed and the parameters of the apparent extraction equilibrium constants (K) were calculated by fitting experimental data. The key factors those affect extraction equilibrium were revealed.The polar n-octanol was a suitable diluent for extracting pyridine carboxylic acids with 7301 as extractant. D increased first and then decreased with the increase of concentrations of 7301 and there was a maximum when the concentration of 7301 is 0.4218mol/L. As pH increasing, D also increased first and then decreased, and was shown with a maximum in a pH range in which neutral (or zwitterion) and anionic pyridine carboxylic acids dominated. D was also found to be reduced with increasing initial concentrations of pyridine carboxylic acids.The interaction mechanisms between 7301 in n-octanol and pyridine carboxylic acids were validated by Infrared spectroscopic analysis. Pyridine carboxylic acids could complex with n-octanol through hydrogen-bonding, thus accelerated the transfer of pyridine carboxylic acids into organic phases to react with 7301.7301 mainly reacted with neutral (or zwitterion) and anionic pyridine carboxylic acids, and formed a type of ion-pair complexes. The equilibrium pH has no influence on the type of complexes.Based on the experimental results, simultaneously taking physical extraction and chemical extraction into account, expressions of D were proposed, and the apparent extraction equilibrium constants (K) were obtained by fitting experimental data. The results indicated that the precision of proposed model was satisfying.The apparent basicity of extractant, the polarity of diluents and the characteristic parameters of solutes (i.e. pKa and logP) were of great influences on extraction equilibrium. The relationships of them with logK were also presented in the thesis. It indicated that the differences of pKa and logP were the key factors which caused D to be different among picolinic acid, nictonic acid and iso-nicotinic acid.In addition, equilibrium studies of pyridine carboxylic acids extracted by a series mixtures of 7301 and TBP in n-octanol were also carried out. It was observed with obvious synergistic effect between 7301 and TBP. Concentrations of 7301 and TBP played important roles on extraction equilibrium. The maximum D values were also found to be in the pH range that neutral (or zwitterion) and anionic pyridine carboxylic acids dominated. It existed optimal ratio of 7301 to TBP at which the much higher D values were obtained. As the same as processes of pyridine carboxylic acids extracted by 7301, D values of the mixtures also decreased with the increasing initial concentrations of pyridine carboxylic acids. IR analysis indicated that there were three types of reaction during extraction processes, namely,7301 reacting with pyridine carboxylic acids to form binary complexes, TBP reacting with pyridine carboxylic acids to form binary complexes, and 7301 and TBP co-reacting with pyridine carboxylic acids to form ternary complexes.更多还原