Effect of Water on the Interaction of Tributyl Phosphate Esters and Phosphine Oxides with Imidazolium-based Room Temperature Ionic Liquids

Ruma Joshi, Chemistry

Second Place: Graduate Interdisciplinary Research Presentation

Abstract: Room temperature ionic liquids (RTIL) are solvents which are potentially useful in extractions and separations because of their low vapour pressure, low flammability, and high polarity. Uranium metal can be dissolved in a solution containing nitric acid and tributylphosphate (TBP), forming a uranyl(VI)-TBP complex which is extracted into the RTIL. TBP and tributylphosphine oxide (TBPO) both form strong complexes with uranium and are stable in nitric acid. It is important to understand the chemical interactions at play in RTIL/metal/ligand system's as this will aid in the development of more efficient extractions using RTIL solvents. We are using FTIR, Raman, and NMR spectroscopic methods to study the interactions of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-Tf2N), TBP or TBPO and water. Significant shifts in the 1H NMR signal are seen for the imidazolium ring C2–H protons when TBP or TBPO is added to the solution, suggesting that TBP and TBPO interact with protons on the EMIM+ imidazolium ring through hydrogen bonding. Our 1H NMR and IR spectra also indicate that TBP and TBPO interacts strongly with water in  EMIM-Tf2N.  Based on our 1H NMR results, we can say that the interaction of TBP or TBPO with water is much greater  than the interaction of TBP and TBPO with EMIM+. We also intend to study the effect of uranyl(VI) on these interactions.