Influence of Organic Phase Polarity on Interfacial Mechanism and Efficiency of Reactive Extraction of Acetic Acid with Tri-<i>n</i>-octylamine

Abstract

The reactive extractions of acetic acid, HAc, with tri-n-octylamine (TOA), Q, dissolved in three solvents with different dielectric constants (dichloromethane, butyl acetate, and n-heptane) without and with 1-octanol as phase modifier have been comparatively analyzed. The results indicated that the mechanism of the interfacial reaction between acid and extractant is controlled by the organic phase polarity. In absence of 1-octanol, the structures of the extracted complexes are HAc.Q for dichloromethane, HAc.Q2 for butyl acetate, and (HAc)2Q4 for n-heptane. These structures are modified by adding 1-octanol and become HAc.Q for extraction in dichloromethane or butyl acetate and (HAc)2Q2 for extraction in n-heptane, respectively. Although the presence of 1-octanol improves the extraction efficiency, it leads to the reduction of extraction constants for lower-polar solvents, influence that is more significant for n-heptane.