Phosphonium and Ammonium Ionic Liquids with Aromatic Anions: Synthesis, Properties, and Platinum Extraction

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Contents Vol 63(3)

doi:10.1071/CH09340

Phosphonium and Ammonium Ionic Liquids with Aromatic Anions: Synthesis, Properties, and Platinum Extraction*

Anja Stojanovic ^A ^D ^E, Daniel Kogelnig ^A ^D, Lisa Fischer ^B, Stephan Hann ^B, Markus Galanski ^A, Michael Groessl ^C, Regina Krachler ^A, Bernhard K. Keppler ^A

^A University of Vienna, Department of Inorganic Chemistry, Waehringer Strasse 42, 1090, Vienna, Austria.
^B Department of Chemistry, Division of Analytical Chemistry, University of Natural Resources and Applied Life Sciences, Muthgasse 18, 1190, Vienna, Austria.
^C Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
^D Both authors contributed equally to this work.
^E Corresponding author. Email: anja.stojanovic@univie.ac.at





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Australian Journal of Chemistry 63(3) 511–524 http://dx.doi.org/10.1071/CH09340
Submitted: 17 June 2009 Accepted: 26 August 2009 Published online: 26 March 2010

Abstract

Several hydrophobic long-chain quaternary ammonium and phosphonium ionic liquids (ILs) with functionalized aromatic anions were prepared following a metathesis route using tricaprylmethylammonium chloride (Aliquat 336) and trihexyl(tetradecyl)phosphonium chloride (Cyphos IL101) as precursors. The incorporation of aromatic anions bearing hydroxy-, methoxy-, thiol-, and thioether functionalities as well as tetraphenylborate anions resulted in an increased chemical stability of the ILs and an alteration of their physico-chemical properties. Furthermore, aromatic anions significantly decreased the water solubility and water uptake of both ammonium and phosphonium-based ILs. Thiol- and thioether ILs were applied for the extraction of platinum from aqueous phase using liquid phase micro-extraction. Time dependent studies showed a rapid elimination of up to 95% platinum after 30 min. With a leaching of the anion <0.01 wt-% into the aqueous media, the evaluated ILs were found to be suitable as extracting agents for platinum from aqueous solutions.

^* This paper is based on the poster “Thioether-functionalized ionic liquids and their task specificity for platinum uptake using liquid phase micro-extraction” presented at COIL₃, 3rd Congress on Ionic Liquids, May 31–June 4 2009, Cairns, Australia.