Studies on the Use of Ionic Liquids as Potential Extractants of Phenolic Compounds and Metal Ions

Abstract

The present work was aimed at investigating the usefulness of 1‐(n‐alkyl)‐3‐methylimidazolium‐derived ionic liquids (ILs) in liquid–liquid separation processes. For this purpose, a series of 1‐(n‐alkyl)‐3‐methylimidazolium tetrafluoroborates and hexafluorophosphates were prepared by standard synthetic methods and characterized by ¹H NMR. Experiments were performed to assess the influence of the alkyl group and the anion on the physical properties of the IL. Equilibrium studies on the extraction of heavy metal ions (copper, zinc, and chromium) and some common pollutant aromatic compounds (phenol, tyrosol, and p‐hydroxybenzoic acid) from aqueous media then were performed with some selected ILs. The effects of temperature and the pH on the distribution ratio of solutes between the IL/aqueous phases also were analyzed. The results suggest that some of the ionic liquids tested are adequate to extract metal ions and organic compounds from aqueous solutions, with a high efficiency in some instances.

Keywords:

• Ionic liquid (IL)
• Liquid–liquid extraction
• Organic solutes
• Metal ions

Acknowledgments

Karin Kovárová, Ana Jesus, and Guadalupe Rodrigues are thanked for their help in part of this work. We also thank João M. N. Fareleira for fruitful discussions. Financial support of this work by Fundação para a Ciência e a Tecnologia (FCT, Portugal) with European Community (FEDER) and national funds, including a grant to STMV through Centro de Química Estrutural/Programmatic funds, is gratefully acknowledged. Karin Kovárová thanks the Socrates program for a scholarship.