FUNDAMENTAL STUDIES AND POTENTIAL APPLICATIONS OF CLOUD POINT EXTRACTION By MELISSA ENSOR FREIDERICH A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY WASHINGTON STATE UNIVERSITY Department of Chemistry DECEMBER 2011 To the Faculty of Washington State University: The members of the Committee appointed to examine the dissertation of MELISSA ENSOR FREIDERICH find it satisfactory and recommend that it be accepted. ___________________________________ Kenneth L. Nash, Ph.D., Chair ___________________________________ Sue B. Clark, Ph.D. ___________________________________ James O. Schenk, Ph.D. ___________________________________ Glenn Fugate, Ph.D. ii ACKNOWLEDGMENT “There are two possible outcomes: if the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery.” Enrico Fermi “Failure is simply the opportunity to begin again, this time more intelligently.” Henry Ford “A man who carries a cat by the tail learns something he can learn in no other way.” Mark Twain The preceding quotes, to me, sum up my graduate school experience. The past five years have not been easy and often times seemed impossible. I need to acknowledge and thank the people who helped me get to where I am today because without them I would not have completed this journey. First of all, I want to thank my husband, John. He has been my rock and sometimes only friend and source of comfort during my time in Pullman. John never wavered in his support of me and usually believed in me more than I believed in myself. I would not have completed my Ph.D. without his unwavering love and encouragement. John, for putting up with me the last four years, you totally deserve a Camaro. If it were not for my parents, I would not be here at all. Additionally, they have been a source of constant support and encouragement the past five years. Thank you, Mom and Dad, for everything you have done for me. I hope this makes you proud. Also, thank you for not pushing or trying to encourage me to go into chemistry. That would almost certainly have backfired and then I would not have met John or be writing this, so thanks for that. iii Of course I cannot forget my advisor, Kenneth Nash. While we have had our differences over the years, graduate school would not have been what it was without him. I have learned and grown a lot as a scientist and person during the years I have spent working in the Nash group. Thank you, Ken, for your assistance and guidance over the past five years. I would like to thank Linfeng Rao, Guoxin Tian, Sergey Sinkov, and Greg Lumetta for allowing me to come to their respective laboratories and perform experiments that would have otherwise not been possible. Finally, I would like to thank the members of my committee Ken Nash, Sue Clark, Jim Schenk, and Glenn Fugate, for agreeing to be on my committee and committing to reading this thesis in its entirety. iv FUNDAMENTAL STUDIES AND POTENTIAL APPLICATIONS OF CLOUD POINT EXTRACTION Abstract by MELISSA ENSOR FREIDERICH, Ph.D. Washington State University December 2011 Chair: Kenneth L. Nash Separation of the components of nuclear fuel provides an interesting and complicated separation challenge as the trivalent lanthanides and actinides must be separated from each other. The difficulties of this separation have prompted exploration of novel separation techniques, such as cloud point extraction (CPE). CPE is an aqueous separation technique that utilizes a surfactant, in place of an organic solvent, for phase separation. The technique has shown utility for transition metal separations and some applicability to lanthanide separation. While numerous separation schemes have been demonstrated with CPE, very little fundamental research has been done to expand understanding of the mechanism of extraction and phase separation in the system. Current CPE systems have been developed using a “trial and error” approach with no insight into how to improve the separation. The focus of this dissertation was to develop a better fundamental understanding of the mechanism of extraction in CPE systems, as a means of improving separation system design. To achieve this goal a CPE system for lanthanide and actinide separation was designed and studied. The influence of electrolytes on the extraction behavior and system behavior was examined along with the influence of the surfactant on metal ligand complexation using radiometric v techniques, potentiometric titrations, uv-visible spectroscopy, and fluorescence spectroscopy. These studies combined to help give insight into a seemingly simple extraction system, showing CPE is in fact much more complicated than initially expected. The goal of these studies was to provide a better understanding of the CPE system to facilitate improved system design. vi TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................................... iii ABSTRACT .....................................................................................................................................v LIST OF TABLES ....................................................................................................................... xiii LIST OF FIGURES .......................................................................................................................xv I. INTRODUCTION .........................................................................................................1 I.1 CLOUD POINT EXTRACTION (CPE) .......................................................................2 I.2 CLOUD POINT TEMPERATURE (CPT) AND ELECTROLYTE EFFECTS ...........6 I.3 CPE OF METAL IONS .................................................................................................9 I.4 RESEARCH SCOPE ...................................................................................................16 I.5 LANTHANIDE CARRIER LIGANDS ......................................................................17 II. EXPERIMENTAL PROCEDURES AND METHODS .............................................19 II.1 MATERIALS .............................................................................................................19 II.2 INITIAL CPE EXPERIMENTS ................................................................................20 II.3 PMBP CPE EXPERIMENTS ....................................................................................22 II.4 CPT DETERMINATION ..........................................................................................23 II.5 KARL FISCHER ANALYSIS ...................................................................................24 II.6 FT-IR ANALYSIS .....................................................................................................24 II.7 pCH MEASUREMENTS ...........................................................................................25 II.8 POTENTIOMETRIC TITRATIONS .........................................................................25 vii II.9 UV-VISIBLE SPECTROSCOPY ..............................................................................26 II.10 FLUORESCENCE MEASUREMENTS .................................................................27 III. RESULTS AND DISCUSSION III.1 EXPLORATIONS OF CLOUD POINT EXTRACTION AND APPLICATION TO LANTHANIDES AND ACTINIDES III.1.1 RESULTS ...............................................................................................................29 III.1.1.18-HQ .........................................................................................................29 III.1.2 SYSTEM DESIGN ................................................................................................31 III.1.2.1 Surfactant Selection ................................................................................31 III.1.2.2 Ligand .....................................................................................................33 III.1.2.3 Salt Effects ..............................................................................................36 III.1.3 CLOUD POINT TEMPERATURE .......................................................................37 III.1.3.1 Alcohol Study .........................................................................................37 III.1.3.2 Electrolytes Study ...................................................................................38 III.1.4 CONCLUSIONS....................................................................................................41 III.2 DEVELOPMENT OF A CPE SEPARATION TECHNIQUE USING 1-PHENYL-3- METHYL-4-BENZOYL-5-PYRAZOLONE TO EXTRACT EU(III) AND AM(III) III.2.1 SYSTEM OPTIMIZATION ..................................................................................47 III.2.2 SLOPE ANALYSIS ..............................................................................................52 III.2.3 ACTINIDE PARTITIONING ...............................................................................54 III.2.4 METAL LOADING ...............................................................................................55 III.2.5 CONCLUSIONS....................................................................................................57 viii III.3 EFFECTS OF STRUCTURE-BREAKING AND STRUCTURE-MAKING ELECTROLYTES ON A NONIONIC CLOUD POINT EXTRACTION SYSTEM III.3.1 RESULTS ...............................................................................................................60