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Anion Effects in the Extraction of Metal Ions Into Room-Temperature Ionic Liquids (RTILS) Sarah Lynn Garvey University of Wisconsin-Milwaukee

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Anion Effects in the Extraction of Metal Ions Into Room-Temperature Ionic Liquids (RTILS) Sarah Lynn Garvey University of Wisconsin-Milwaukee University of Wisconsin Milwaukee UWM Digital Commons Theses and Dissertations May 2013 Anion Effects in the Extraction of Metal Ions into Room-Temperature Ionic Liquids (RTILS) Sarah Lynn Garvey University of Wisconsin-Milwaukee Follow this and additional works at: https://dc.uwm.edu/etd Part of the Analytical Chemistry Commons Recommended Citation Garvey, Sarah Lynn, "Anion Effects in the Extraction of Metal Ions into Room-Temperature Ionic Liquids (RTILS)" (2013). Theses and Dissertations. 100. https://dc.uwm.edu/etd/100 This Dissertation is brought to you for free and open access by UWM Digital Commons. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of UWM Digital Commons. For more information, please contact [email protected]. ANION EFFECTS IN THE EXTRACTION OF METAL IONS INTO ROOM-TEMPERATURE IONIC LIQUIDS (RTILs) by Sarah Lynn Garvey A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Chemistry at The University of Wisconsin-Milwaukee May 2013 ABSTRACT ANION EFFECTS IN THE EXTRACTION OF METAL IONS INTO ROOM-TEMPERATURE IONIC LIQUIDS (RTILs) by Sarah Lynn Garvey The University of Wisconsin-Milwaukee, 2013 Under the Supervision of Professor Mark L. Dietz, Ph.D. As part of a broader program directed at the development of improved approaches to the removal of actinides and heat-producing fission products from spent nuclear fuel, the fundamental aspects of the partitioning of selected metal ions between aqueous solution and various room-temperature ionic liquids (ILs) containing a neutral extractant have been investigated. Prior work has shown that in contrast to the partitioning of alkaline earth cations into conventional solvents in the presence of a crown ether, which is known to proceed via a single pathway (i.e., neutral complex extraction), their extraction into an IL is often a complex, multi-path process in which the ionic liquid itself plays an active role. Specifically, in addition to the extraction of a neutral complex, ion exchange involving a protonated extractant molecule or the cationic constituent of the ionic liquid can also comprise important modes of ion transfer. In an effort to clarify the factors governing the balance among these various pathways, the influence of the aqueous phase and IL anions has been examined. In addition, the effect of the presence of an extractable anion - (here, TcO4 ) has been explored. The results indicate that the predominant mode of extraction of an alkaline earth cation by crown ethers is strongly influenced by both the aqueous phase anion (with low hydration energy favoring neutral complex extraction) ii and the IL anion (with hydrophilic anions also favoring extraction of a neutral species). The nature of the extracted species has also been determined to influence the preferred mode(s) of partitioning. That is, for an extractable anion, additional pathways are observed, with ion exchange involving either a cation-crown ether-nitrato ion-pair or the anionic constituent of the IL representing important routes for extraction. In related work, the radiolysis of two families of ILs has been examined and the structural features of the IL cation and anion leading to satisfactory radiolytic stability have been identified. Taken together with the extraction studies, these results represent an important step in the development of viable, IL-based separation systems for the removal of fission products from nuclear waste streams and for their analytical-scale separation for subsequent determination. iii © Copyright by Sarah L. Garvey, 2013 All Rights Reserved iv DEDICATION This is dedicated to my husband, Michael, whose love, support, and knowledge helped me get through this journey, and to my parents, who have always supported my decisions and encouraged my love for the sciences. v Table of Contents LIST OF FIGURES .......................................................................................................... ix LIST OF TABLES ........................................................................................................... xii ACKNOWLEGEMENTS ............................................................................................... xiii CHAPTER 1: INTRODUCTION ...................................................................................... 1 1.1 Overview and Scope ................................................................................................ 1 1.2 Ionic Liquids ............................................................................................................ 4 1.3 Solvent Extraction of Metal Ions into Conventional Organic Solvents and Ionic Liquids .................................................................................................................. 7 1.4 Overview of the Chapters ....................................................................................... 9 1.5 References .............................................................................................................. 10 CHAPTER 2: EFFECT OF AQUEOUS PHASE ANION ON METAL ION EXTRACTION INTO ROOM-TEMPERATURE IONIC LIQUIDS (RTILS) .............. 15 2.1 Introduction ........................................................................................................... 15 2.2 Experimental ......................................................................................................... 17 2.2.1 Materials ...................................................................................................... 17 2.2.2 Instruments .................................................................................................. 17 2.2.3 Methods ....................................................................................................... 18 2.3 Metal Ion Extraction from Acidic Nitrate Media .............................................. 19 2.3.1 Nitric acid and crown ether dependencies of DM for extraction into aliphatic alcohols by DCH18C6 .......................................................................... 19 + - 2.3.2 Nitric acid dependency of DM for extraction into Cnmim Tf2N ILs by DCH18C6 ............................................................................................................ 22 2.4 Metal Ion Extraction from Acidic Chloride Media ............................................ 28 2.4.1 Hydrochloric acid and crown ether dependencies of DM for extraction into aliphatic alcohols by DCH18C6 ................................................................... 28 + - 2.4.2 Chloride anion co-extraction into Cnmim Tf2N ILs upon metal ion extraction by DCH18C6 ...................................................................................... 33 2.4.3 Acid dependency of DSr for extraction from chloride media into + - Cnmim Tf2N ILs by DCH18C6 .......................................................................... 34 + - 2.4.4 Metal ion extraction into C10mim Tf2N : Comparison of halide anions ..... 37 2.4.5 Acid dependency of DM for extraction from chloride media into + - Cnmim Tf2N ILs by DCH18C6 .......................................................................... 38 + - 2.4.6 Crown ether dependency of DM for extraction into Cnmim Tf2N ILs by DCH18C6 ............................................................................................................ 40 2.5 Conclusions ............................................................................................................ 42 2.6 Acknowledgements ................................................................................................ 43 2.7 References .............................................................................................................. 43 vi CHAPTER 3: EFFECT OF IONIC LIQUID ANION ON METAL ION EXTRACTION INTO ROOM-TEMPERATURE IONIC LIQUIDS(RTILS) .......................................... 47 3.1 Introduction ........................................................................................................... 47 3.2 Experimental ......................................................................................................... 49 3.2.1 Materials ...................................................................................................... 49 3.2.2 Instruments .................................................................................................. 50 3.2.3 Methods ....................................................................................................... 51 3.3 Effect of IL Anion on the Mutual Solubility of ILs and Water ........................ 52 + 3.4 Metal Ion Extraction into Cnmim Ionic Liquids from Acidic Chloride Media ............................................................................................................................ 55 + 3.5 Metal Ion Extraction into Cnmim Ionic Liquids from Acidic Nitrate Media ............................................................................................................................ 60 3.6 Ionic Liquid Anion Effects on Extraction Efficiency and Selectivity ............... 67 3.7 Conclusions ............................................................................................................ 71 3.8 Acknowledgements ................................................................................................ 71 3.9 References .............................................................................................................. 72 CHAPTER 4: PERTECHNETATE EXTRACTION FROM
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