ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Liquid-liquid equilibria of butyric acid for solvents containing a phosphonium ionic liquid
Ján Marták and Štefan Schlosser
Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237 Bratislava, Slovakia
Received: 14 June 2007 Revised: 2 August 2007 Accepted: 3 August 2007
Abstract: L/L equilibrium data of butyric acid (BA) in aqueous solutions contacted with the solvents containing ionic liquid (IL), trihexyl-(tetradecyl)phosphonium
bis 2,4,4-trimethylpentylphosphinate (Cyphos IL-104), and a related model are presented. IL-104 and its solutions in dodecane
were found to be effective solvents of BA. The values of the distribution coefficients of BA were higher than those for solvents
with the widely used extractant trioctylamine, especially at low acid concentrations and were also several-fold higher than
those of lactic acid (LA). IL extracted BA only in its undissociated form (BAH) at pH well below pK
a of the acid. The loading of IL was independent of IL concentration and it achieved a value higher than four at saturation.
Complexes with 1–5 molecules of BA per one IL molecule were supposed in the mass action model in which the reactive formation
of complexes (BAH)
(IL)(H2O)2 was supposed. Up to 10 % of the total extracted BA was extracted physically by dodecane as a monomer and dimer, in the solvent.
The water content in the organic phase steeply decreased with the BA concentration, which was caused by splitting water-IL
reverse micelles due to the formation of the BAH/IL complexes.
Keywords: extraction - L/L equilibria - butyric acid - phosphonium ionic liquid - modelling
Full paper is available at www.springerlink.com.
Chemical Papers 62 (1) 42–50 (2008)