Acids extraction by amine-based extractants: An analysis of the effect of anion concentration in the aqueous phase using the donnan model

Riki Canari, Aharon M. Eyal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The concentration of an acid's anion in the aqueous phase affects that acid's extraction efficiency by amine-based extractants. The anion effect is explained by using the acid-dissociation equation in the case that the acid is mainly extracted though H-bonding or solvation. This explanation does not hold in the extraction of strong acids such as hydrochloric or dichloroacetic acid by a relatively strong base extractant (pKaB ≫ pKaA). To explain the anion effect in these systems, we reexamined our theory and modified it with the Gibbs-Donnan model. The modified theory shows that the proton activity in the organic phase could differ significantly from that in the aqueous phase, depending on the relative activities of the anions in those two phases. Thus, in turn, the relative activity of the anion affects the protonation of the amine in the organic phase, pKaB. Accordingly, the modified theory successfully explains the effect of the anion concentration on the extraction efficiency.

Original languageEnglish
Pages (from-to)1315-1320
Number of pages6
JournalIndustrial and Engineering Chemistry Research
Volume42
Issue number7
DOIs
StatePublished - 2 Apr 2003

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