Effect of pH on dicarboxylic acids extraction by amine-based extractants

Riki Canari, Aharon M. Eyal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

The work presented here studies the effect of pH on the extraction of malic, maleic, and glutaric acids by Primene JMT, tris(2-ethylhexyl)amine, and tri-n-octylamine and the IR and NMR spectra of the formed organic phases. Three categories were found: (1) In the first case, the extractant is a weaker base than both anions of the acid, i.e., pHhn < pka1 < pKa2. The undissociated acid is the dominant species in the organic phase. Extraction is mainly due to H-bonding or solvation interactions and shows a drop-off at pH≈pKa1. (2) For systems in which pKa1 < pHhn < pKa2, at acid-to-amine molar ratios greater than 1, undissociated acid is above-stoichiometrically extracted, R3NH+⋯AH-⋯HAH in addition to ion-paired acid. As the pH is increased, the undissociated acid is neutralized first. Thus, the extraction curve shows a drop-off at pH ν pKa1. At stoichiometric loading, the monovalent ion pair, R3NH+⋯AH-, becomes the dominant species. Upon further pH elevation, the protonated amine R3NH+ is the neutralized acid. (3) In systems where pKa1 < pKa2 < pHhn, the divalent ion pair R3NH+⋯A2-+ HNR3 is formed. Thus, the extraction curve shows an additional drop-off at pH ≈ pKa2.

Original languageEnglish
Pages (from-to)1293-1300
Number of pages8
JournalIndustrial and Engineering Chemistry Research
Volume42
Issue number7
DOIs
StatePublished - 2 Apr 2003

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