Determination of Extractant Solubility in Ionic Liquids by Thermogravimetric Analysis

ABSTRACT

The high thermal stability typical of many room temperature ionic liquids (RTILs) is exploited as the basis of a method employing thermogravimetric analysis (TGA) for the determination of the solubility of various metal ion extractants in these solvents. The approach is simple, applicable to extractants lacking functional groups that would permit their ready quantification by other methods, and requires only small (mg) quantities of sample. These features of the method, along with its limitations, are illustrated by the determination of the solubility of representative examples of several common extractant families, including bis(2-ethylhexyl)phosphoric acid (HDEHP) and di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6), in a series of 1,3-dialkylimidazolium (C_nmim⁺)-based ionic liquids.

KEYWORDS:

• Extractant solubility
• ionic liquids
• thermogravimetric analysis

Acknowledgments

The authors thank Mr Paul Rickert of Argonne National Laboratory and Dr Bruce Moyer of Oak Ridge National Laboratory for the generous gift of CMPO and Bob-Calix, respectively.

Additional information

Funding

This work at UWM was financially supported by the Single Investigator Small Group Research (SISGR) Program of the Office of Basic Energy Sciences of the United States Department of Energy through subcontract with Brookhaven National Laboratory. Support from NSF-MRI 1531870 is gratefully acknowledged for the acquisition of TTU’s 500-MHz multi-nuclear NMR spectrometer.