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 (pKa). The extractability depended on the lgP for the solutes with pKa close to each other，if otherwise depended on pKa of the acid depended on it increased with increasing lgP of the acid and decreasing pKa. 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.