Aliquat 336萃取醋酸的平衡特性

选择Aliquat 336为萃取剂 ,氯仿、正辛醇和煤油为稀释剂 ,醋酸稀溶液为分离溶质 ,研究了稀释剂种类、反应剂浓度、水相 pH值、溶质在水相的浓度等因素对醋酸萃取分配系数的影响 ,分析了Aliquat 336萃取醋酸的机理 ,并在此基础上建立了描述萃取平衡的数学模型 .结果表明 :萃取结果基本符合反应剂与稀释剂的简单加和 ;稀释剂对萃取效果的影响显著 ,随Aliquat 336浓度的增大 ,氯仿和煤油为稀释剂时的萃取能力较正辛醇增加得快 ;随 pH值的变化D存在一个最大值 ,该值只与反应剂在有机相中的浓度有关 .Aliquat 336萃取醋酸存在阴离子交换和化学缔合两种机制 ,表观的阴离子交换反应平衡常数K₁在有稀释剂的条件下比纯反应剂时有所增大 ,其中氯仿的影响相对较大 ,表观的化学缔合反应平衡常数K₂ 在有稀释剂的条件下表现为 ,惰性稀释剂煤油对K₂ 的影响不明显 ,氯仿具有强化的作用 ,而正辛醇具有削弱Aliquat 336与醋酸化学缔合的能力 .

EXTRACTION EQUILIBRIUM OF ACETIC ACID WITH QUATERNARY AMINE--Aliquat 336

The extraction of acetic acid from an aqueous solution into solutions of quaternary amine,Aliquat 336,in different diluent,n-octanol,chloroform and kerosene,was investigated under various pH,concentration of Aliquat 336 and solute.The style of complex formation was discussed,and a model describing the equilibrium was proposed.The distribution coefficient,D,fitted the simple additive property of Aliquat 336 and the diluent.Diluent affected the D apparently; the D in chloroform and kerosene increased quicker than that in n-octanol with the Aliquat 336 concentration in organic phase.There was a maximum value for D against pH,which depended on the Aliquat 336 concentration only,and the pH value responding to the maximum D was 4.0～4.3 and 3.7～4.2 for 25% Aliquat and 50% Aliquat system,respectively.Acetic acid was bonded to Aliquat 336 by both ion exchange and chemical association,and diluent affected their parameters obviously.The apparent constant of ion exchange,K ₁,increased in diluent,especially in chloroform.The apparent constant of association,K ₂,increased in chloroform also,decreased in n-octanol,and kerosene affected K ₂ not apparently.