三辛胺萃取一元羧酸的平衡规律(Ⅰ) 萃取平衡特性

EXTRACTION EQUILIBRIA BEHAVIOR OF MONOCARBOXYLIC ACIDS BY TRIOCTYLAMINE (Ⅰ) EXTRACTION EQUILIBRIA

以三辛胺 (TOA)为反应萃取剂 ,正辛醇、甲基异丁基酮 (MiBK)、正己烷、四氯化碳和氯仿为稀释剂 ,甲酸、乙酸、丙酸、丁酸、戊酸、一氯乙酸、二氯乙酸、三氯乙酸、乙醇酸、乙醛酸、乳酸为被萃溶质 ,开展了萃取平衡特性的实验研究 .结果表明 ,羧酸的亲油性和酸性是影响TOA萃取羧酸的关键参数 .萃取平衡条件下 ,羧酸的酸性差别较小时 ,TOA的负载率主要取决于羧酸的亲油性lgP ,且lgP越大 ,TOA负载率越高 ;羧酸的酸性差别较大时 ,TOA的负载率主要与羧酸的酸性pKa 有关 ,且pKa 越小 ,TOA负载率越高 .稀释剂种类、TOA浓度对TOA的表观碱度和TOA的负载率有影响 ,TOA负载率Z <1时 ,稀释剂对羧酸萃取平衡的促进作用为正辛醇≥氯仿 >MiBK >四氯化碳≥正己烷 ,且TOA的负载率随TOA浓度的增大而减小 .TOA的表观碱度是定量表现萃取剂在萃取分离环境中性质的重要参数 .

Extraction process based on chemical complexation is of higher capacity and selectivity for dilute polar organic solution. In this paper, phase equilibrium governing the reactive extraction of formic, acetic, propionic, butyric, valeric, monochloroacetic, dichloroacetic, trichloroacetic, glycolic, lactic and glyoxylic acids from aqueous solution into solutions of trioctyl amine (TOA) in the diluents, 1-octanol, chloroform, 4-methyl-2-pentanone (MiBK), n-hexane and tetrachloromethane were investigated. The results showed that the extractability depended on the hydrophobicity (lgP) of the acids and the acidity of the acids (pK a). The extractability depended on the lgP for the solutes with pK a close to each other,if otherwise depended on pK a of the acid depended on it increased with increasing lgP of the acid and decreasing pK a. Also, the extractability depends on diluent type and TOA concentration, and under the condition of TOA loading less than 1, the extractability in various diluents shows 1-octanol≥chloroform>MiBK>tetrachloromethane>n-hexane. The specific basicity of TOA is one of the most important parameters indicating extractant dependence on solvent directly.