三烷基氧膦反应萃取一元羧酸的规律

化学萃取法对有机羧酸稀溶液的分离具有高效性和高选择性.萃取剂的相对碱性是表征萃取剂性质的重要参数.选取三烷基氧膦（TRPO）为萃取剂，煤油为稀释剂，甲酸、乙酸、丙酸、丁酸、己酸、一氯乙酸、二氯乙酸、三氯乙酸、乳酸9种一元羧酸为被萃溶质，研究了溶质种类、TRPO浓度对萃取剂相对溶质的相对碱度（pK_a,BS）的影响，探索了从化学反应基本理论出发研究络合萃取平衡规律的可行性.实验结果表明，对于TRPO/煤油萃取剂体系，pK_a,BS值不随TRPO的浓度而变化;而溶质的亲油性和酸性对pKa,BS值影响显著;从基本理论出发推证的只包含溶质的pK_a以及萃取剂的pK_a,BS的描述反应萃取平衡规律的数学表达式可以预测TRPO萃取有机羧酸的平衡规律，并对水溶性较小或萃取平衡分配系数较小体系的pK_a,BS值测定提出了简单、易行的修正方法.

Reactive extraction equilibria behavior of monocarboxylic acids by trialkyl phosphine oxide

On the basis of literature survey, trialkyl phosphine oxide(TRPO) was selected as the extractant. Nine kinds of mono-carboxylic acids, formic, acetic, propionic, butyric, caproic, monochloroacetic, dichloroacetic, trichloroacetic and lactic acids, were used as solutes to be extracted. Kerosene was investigated for their abilities to affect the relative basicity of extractant (pK_ a,BS). The dependence of TRPO concentration, hydrophobicity and pK_a of the acid on pK_ a,BS was studied in order to explore the feasibility of mathematical models based on the chemical reactive theory to describe the extractive equilibrium behavior with only two parameters, hydrophobicity and pK_a,that affect pK_ a,BS.The pK_ a,BS value hardly changed with TRPO concentration, while the properties of carboxylic acid, hydrophobicity and pK_a affect pK_ a,BS obviously.The mathematic models proposed in this paper could be used to predict the extractive equilibrium of monocarboxylic acid extracted by TRPO.A simple and feasible modification method for measuring pK_ a,BS was also suggested.