ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Phosphonium ionic liquids as new, reactive extractants of lactic acid

J. Marták and Š. Schlosser

Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia

E-mail: Stefan.Schlosser@stuba.sk

Received: 14 June 2006  Revised: 19 July 2006  Accepted: 24 July 2006

Abstract: Solvent properties of ionic liquids with trihexyltetradecylphosphonium cation and bis(2,4,4-trimethylpentyl)phosphinate anion (Cyphos IL-104) or chloride anion (Cyphos IL-101) were studied. IL-104 effectively extracted lactic acid (LA) with distribution coefficients above 40 at low acid concentrations. IL-104 extracted only undissociated acid (LAH) what supported the coordination mechanism of lactic acid extraction via H-bonding. In the extraction of lactic acid by phosphonium chloride (IL-101) an ion-exchange mechanism contributed remarkably to the extraction especially at basic pH where anionic form of this acid predominated. A high solubility of water in hydrophobic IL-104 up to 14.4 mass % was connected with the formation of reverse micelles. A dual mechanism of water extraction to phosphonium ionic liquids was identified, which consisted of water incorporation into reverse micelles and the inclusion of water into the hydrated complex of lactic acid with ionic liquid (IL). The extraction of lactic acid caused splitting of reverse micelles with liberation of water from the solvent. In the saturated solvent only hydration water remained in the complex of lactic acid with phosphonium ionic liquid, with the suggested structure (LAH)_p(IL)(H₂O)₂, where the value of p ranged from 1 to 3.

Keywords: extraction mechanism - lactic acid - ionic liquids - reverse micelles

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-006-0072-2

Chemical Papers 60 (5) 395–398 (2006)