OPTIMIZATION OF THE ELECTROCHEMICAL PRE-CONCENTRATION OF f-ELEMENTS By

168 Pages·2014·1.85 MB·English

by  Jamie Doyle

OPTIMIZATION OF THE ELECTROCHEMICAL PRE-CONCENTRATION
OF f-ELEMENTS

By

JAMIE L. DOYLE

A dissertation submitted in partial fulfillment of
the requirements for the degree of

DOCTOR OF PHILOSOPHY

WASHINGTON STATE UNIVERSITY
Department of Chemistry

AUGUST 2014

©Copyright by JAMIE L. DOYLE, 2014
All Rights Reserved
©Copyright by JAMIE L. DOYLE, 2014
All Rights Reserved
To the Faculty of Washington State University:
The members of the Committee appointed to examine the
dissertation of JAMIE L. DOYLE find it satisfactory and recommend that
it be accepted.

______________________________
Sue B. Clark, Ph.D., Chair

Kenneth L. Nash, Ph.D.

Mark Engelmann, Ph.D.

Nathalie A. Wall, Ph.D.

Frank Cheng, Ph.D.

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ACKOWLEDGEMENTS

There are many people that I owe thanks to for their help and encouragement throughout
my progress in graduate school. I would like to start my thanks with my family. Although I live
a slight distance from them, they have given me so much support, encouragement, and humor to
help me achieve my career goals.
Next, I would like to thank my mentor Dr. Sue Clark for allowing me to work in her lab.
The experience has been amazing and I feel like I could not have had a better role model and
mentor. I also have to thank her for the opportunity to teach with her, I had so much fun and
truly enjoyed the experience. In addition to the mentorship I received from Dr. Clark, I also have
to thank my committee, Dr. Jim Schenk, Dr. Ken Nash, Dr. Nathalie Wall, Dr. Frank Cheng, and
Dr. Mark Engelmann for their help, advice, and guidance on my project. It has been a real
pleasure working with each of them and I have appreciated my time getting to know them
professionally and personally. I would like to extend a special thank you to Dr. Jim Schenk, who
originally inspired me to pursue my advanced degree and focus in electrochemistry. The time I
had with him was unforgettable. He was not only an amazing neuroscientist, electro- and
analytical chemist with a rich history of stories to share and advice to bestow to future scientists,
but he was a wonderful person and friend.
In addition to my family and committee who contributed greatly to my personal and
professional growth, I have to thank my friends and colleagues at WSU. My past and present
Clark lab-mates: Dr. Schumacher, Dr. Kurosaki, Dr. McDonald, Dr. House, Dr. Zhang, Amber,
Mat, Kevin, Morgan, Sam, Amanda, and Heather; thank you for your time, patience, attention,
advice, and support to make me a better chemist. I benefited greatly from my experiences
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working with Dr. Schumacher and Dr. Kurosaki who taught me many valuable skills and had an
immense amount of patience with my endless questions.
Last but not least by any measure, thank you to my friends at WSU and abroad. I would
not have had nearly as much fun in graduate school without you, nor would I have been able to
carry on! Not only have I made so many memories with so many excellent people, but you have
all been so patient with my wayward movie/lyric quotes, randomness, endless talking, and for
some, long epic car rides complete with serenades. With that, I can only conclude by saying one
last very heartfelt thank you to all, and to remind everyone, they do move in herds.

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OPTIMIZATION OF THE ELECTROCHEMICAL PRE-CONCENTRATION
OF f-ELEMENTS
Abstract

by Jamie L. Doyle, Ph.D.
Washington State University
August 2014

Chair: Sue B. Clark
Rapid pre-concentration of trace lanthanide cations in aqueous solution has been
achieved using mercury film electrodes to reduce time associated with sample preparation.
Although effective, this technique has shown minimal sample pre-concentration when applied to
trace level plutonium (Chapter 2). With potential applications in nuclear forensics and
environmental monitoring, maximum sample pre-concentration is critical for the greatest
sensitivity. Through work investigating various characteristics of aqueous matrices (Chapter 3),
optimal working conditions have been found and applied to f-element pre-concentration.
Additional work was completed in elucidating the mechanism of interaction between the metal
cations and mercury film of the electrode to further optimize the technique (Chapter 4 and 5).
The presence of the mercury film has been observed to be a critical component in the pre-
concentration. This dependence most likely results from an amalgamation adsorption
mechanism.

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TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS………………………………………………………………………iii
ABSTRACT………………………………………………………………………………….........v
LIST OF TABLES……………………………………………………………………………......ix
LIST OF FIGURES…………………………………………………………………………….....x
CHAPTER 1
1.1 INTRODUCTION………………………………………………………………………...1
CHAPTER 2: CHARACTERIZATION OF ELECTROCHEMICAL PRE-CONCENTRATION
OF PLUTONIUM
2.1 ABSTRACT……………………………………………………………………………...28
2.2 INTRODUCTION……………………………………………………………………….28
2.3 METHODS AND MATERIALS………………………………………………………...30
2.4 RESULTS AND DISCUSSION…………………………………………………………32
2.5 CONCLUSION…………………………………………………………………………..37
CHAPTER 3: OPTIMIZATION OF AQUEOUS CONDITIONS FOR ELECTROCHEMICAL
PRE-CONCENTRATION OF f-ELEMENTS
3.1 ABSTRACT……………………………………………………………………………...42
3.2 INTRODUCTION……………………………………………………………………….42
3.3 METHODS AND MATERIALS………………………………………………………...44
3.4 RESULTS AND DISCUSSION…………………………………………………………46
3.5 CONCLUSION…………………………………………………………………………..55
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CHAPTER 4: INVESTIGATION INTO THE ADSORPTOIN MECHANISM OF
LANTHANUM ON A THIN MERCURY FILM
4.1 ABSTRACT……………………………………………………………………….……..61
4.2 INTRODUCTION…………………………………………………………………….…61
4.3 METHODS AND MATERIALS………………………………………………………...64
4.4 RESULTS AND DISCUSSION…………………………………………………………66
4.5 CONCLUSION…………………………………………………………………………..73
CHAPTER 5: DETERMINATION OF THE MECHANSIM OF PLUTONIUM DURING THE
ELECTROCHEMICAL PRE-CONCENTRATION WITH A THIN MERCURY FILM
ELECTRODE
5.1 ABSTRACT…………………………………………………………………………...…79
5.2 INTRODUCTION……………………………………………………………………….79
5.3 METHODS AND MATERIALS……………………………………………………..….81
5.4 RESULTS AND DISCUSSION………………………………………………………....84
5.5 CONCLUSION…………………………………………………………………………..91
CHAPTER 6
6.1 CONCLUSION…………………………………………………………………………..96
6.2 FUTURE WORK………………………………………………………………………...98
APPENDIX………………………………………………………………………………...…….95
CHAPTER 7: EXPERIMENTALLY DETERMINED PARAMETERS AND CALCULATIONS
7.1 Introduction…………………………………………………………………..…………101
7.2 Electroactive Area Measurement………………………………..…………………..….101
7.3 Diffusion Coefficient Studies…………………………………………………………..103
CHAPTER 8: SUPPLEMENTAL FIGURES TO DISSERTATION CHAPTERS
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8.1 Changes in Voltammetric Signal with Mercury Film …………………..………….110
8.2 Solution Speciation Comparison of La3+ and Pu3+………………………….……...112
8.3 Speciation of La3+ with Increasing Chloride Concentration …………………..…...114
8.4 α-Spectroscopy Results of 241Am ……………………………………………….....118
CHAPTER 9: DETAILED EXPERIMENTAL ELECTROCHEMICAL PROCEDURES
9.1 Introduction…………………………………………………………………………120
9.2 Electrode Polishing and Cleaning…………………………………………………..120
9.3 Electrochemical Procedures ………………………………………………………..121
9.4 Sample Preparation for Final Analysis……………………………………………..125
CHAPTER 10: REVIEW OF ELECTROANALYTICAL TECHNIQUES
10.1 Chronoamperometry …………..……………………………………..…………….....129
10.2 Cyclic Voltammetry ………………………………………………………………......131
CHAPTER 11: RAW DATA
11.1 Introduction ………………………………………………………………….……137
11.2 Mercury Film Formation Raw Potentiostat Data………………………………….138
11.3 Lanthanum Adsorption Raw Potentiostat Data……………………………………142
11.4 Lanthanum Stripping Raw Potentiostat Data……………………………………...146
11.5 Cyclic Voltammetry Raw Potentiostat Data………………………………………150
11.6 ICP-MS Raw Results of La………………………………………………………..153
11.7 ICP-MS Raw Results of Pu……………………………………………………….154
11.8 Raw α-Spectroscopy Results for Pu……………………………………………….155

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LIST OF TABLES
1.4.1 Standard Reduction Potentials of Lanthanides………………………...………….8
1.7.1 Effect of Potential on Metal Adsorption…………………………………………15
7.3.1 Comparison of the Calculated La Moles Adsorbed to ICP-MS……………......107
7.3.2 Comparison of the Calculated Pu Moles Adsorbed to ICP-MS……………..…107
8.4.1 Results of α-Spectroscopy of 241Am Pre-Concentration………………………..118
8.4.2 Comparison of α-Spectroscopy Results of 241Am Pre-Concentration………….118
11.6.1 Raw ICP-MS La3+ Data……………………………….………………………..153
11.7.1 Raw ICP-MS 239Pu and 242Pu Data……………………….…………………….154

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