~Ms~Sorofcivil and Environmental Engineering

Rice University The synthesis, characterization, and application of iron oxide nanocrystals in magnetic separations for arsenic and uranium removal by John Thomas Mayo A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE Doctor of Philosophy Vicki L. Covin, Kenneth S. Pitzer Schlumberger Professor of Chemistry ~ms~sorofCivil and Environmental Engineering entOiliiWhitmire, Professor of Chemistry HOUSTON, TEXAS August 2011 11 ABSTRACT The synthesis, characterization and application of iron oxide nanocrystals in magnetic separations for arsenic and uranium removal by John Thomas Mayo Arsenic and uranium in the environment are hazardous to human health and require better methods for detection and remediation. Nanocrystalline iron oxides offer a number of advantages as sorbents for water purification and environmental remediation. First, highly uniform and crystalline iron oxide nanocrystals (nMAG) were prepared using thermal decomposition of iron salts in organic solutions; for the applications of interest in this thesis, a central challenge was the adaptation of these conventional synthetic methods to the needs of low infrastructure and economically disadvantaged settings. We show here that it is possible to form highly uniform and magnetically responsive nanomaterials using starting reagents and equipment that are readily available and economical. The products of this approach, termed the 'Kitchen Synthesis', are of comparable quality and effectiveness to laboratory materials. The narrow size distributions of the iron oxides produced in the laboratory synthesis made it possible to study the size-dependence of the magnetic separation efficiency of nanocrystals; generally as the diameter of particles increased they could be 111 removed under lower applied magnetic fields. In this work we take advantage of this size dependence to use magnetic separation as a tool to separate broadly distributed populations of magnetic materials. Such work makes it possible to use these materials in multiplexed separation and sensing schemes. With the synthesis and magnetic separation studies of these materials completed, it was possible to optimize their applications in water purification and environmental remediation. These materials removed both uranium and arsenic from contaminated samples, and had remarkably high sorption capacities - up to 12 wt% for arsenic and 30 wt% for uranium. The contaminated nMAG is removed from the drinking water by either retention in a sand column, filter, or by magnetic separation. The uranium adsorption process was also utilized for the enhanced detection of uranium in environmental matrices. By relying on a-particle detection in well-formed and dense nMAG films, it was possible to improve soil detection of uranium by more than ten-thousand-fold. Central for this work was a detailed understanding of the chemistry at the iron oxide interface, and the role of the organic coatings in mediating the sorption process. lV ACKNOWLEDGEMENTS I would like to thank Dr. Vicki L. Colvin, my PhD. advisor and chair of my thesis committee, for valuable instruction and her efforts to provide my research with constant funding. Obviously, without her, none of this would be possible. I would also like to thank Dr. Mason B. Tomson and Dr. Kenton H. Whitmire for participating as my thesis committee. I would like to thank my past and current fellow group members: Dr. Cafer Yavuz, Dr. John Fortner, Dr. Arjun Prakash, Dr. William Yu, Dr. Joshua Falkner, Denise Benoit, Seung Soo Lee, Dr. Huiguang Zhu, Dr. Carolina Avendano, Dr. Feng Li, Zuzanna Lewicka, Chris Jones, Natalia Gonzalez-Pech, Dr. Jennifer Jamison, Yihua Yu, Dr. Karl Krueger, Dr. Tushar Prasad, Adina Boyd, Elizabeth Quevedo-Contreras, Erika Bryant, Aniway Lomeda, Hema Puppala, Min Jung Cho, Dr. Ali Al-Somali, Dr. Yunping Liu, Dr. Christie Sayes, Dr. Qingbo Zhang, Jackson Myers, Camila Zies, Dr. Junyan Zhang, Jieying Jing, Dr. Jing Li, Dr. Rajeev Wahi, and Dr. Rajesh Rengarajan. I would also like to thank the undergraduate researchers that have contributed to this project: Helen D'Couto, Lauren Harrison, Wayne Lin, Louis Chen, David Morse, Angelina Tran, Arely Cantu, Carmen Sucheki, Jessica Cox, Jennifer Wang, Courtney Payne, Edward Larkin, Andy Caughey, Raymond Verm, Roger Basu, Bertram Shih. I would like to thank some of my collaborators at Rice University: Dr. Mason B. Tomson, Dr. Douglas Natelson, Dr. Stephan Link, Dr. Sujin Yean, Dr. Lili Cong, Dr. Sungbae Lee, Dr. Alexandra Fursina, Dr. Alexei Tchemiak, Dr. Jesse Farrell, Dr. Heather Shipley, and Dr. Amy Kan. I would also like to thank all of those at Rice University that have given me significant guidance: Teresa Champion, Dr. Jonathan Brege, Dr. Mary McHale, Brittany Oliva, Dr. Gongmin Fu, Ping Zhang, Dr. Bo Chen, Dr. Angelo Benedetto, v Dr. Wenhua Guo, Dr. Rizia Bardhan-Pint, Alvin Orbaek, Dr. Erika Bakota, Dr. Chris Hamilton, Dr. Chris Crouse, Seunghyun Lee, Sophia Phounsavath, Dr. Dell Doyle, Jorge Fallas, Dr. Liling Zeng. I would also like to thank some of the professors at University of St. Thomas, my undergraduate university, for their previous guidance: Dr. Thomas Malloy, Dr. Gerald Gries, Dr. John Palasota, Dr. William Tinnerman, Dr. Michelle Stieger, Fr. Patrick Braden, Dr. Paul Knopp, Dr. Sheila Waggoner, and Dr. Louie Galloway. I would like to thank my family for always believing in me and for enabling and encouraging me to seek out what I want from this life and not be swayed by what others would want me to do. I feel that even though I have been somewhat isolated from them for these past years, they have been very accommodating to me when I am available to see them. I would specifically like to thank my mother, Rita Mayo, for the dedication of her life to me and for constant guidance with the unfamiliar. I would like to thank my father, Thomas Mayo, for the wisdom that he has taught me throughout my life. I would like to thank my sister, Leslie Tullos, for always thinking of me and never letting her little brother go without when in need. I would especially like to thank Courtney Payne, my loving fiancee, for always being there for me and for tolerating me during my efforts to complete my graduation requirements. And finally I would like to thank all of the organizations that have provided financial support for my research, without them none of this could be possible: the National Science Foundation through the Center for Biological and Environmental Nanotechnology, the Robert A. Welch Foundation, and the United States Environmental Protection Agency. Vl TABLE OF CONTENTS ABSTRACT .............................................................................................................................. ii ACKNOWLEDGEMENTS ..................................................................................................... iv TABLE OF CONTENTS ......................................................................................................... vi LIST OF FIGURES AND TABLES ........................................................................................ ix DEDICATION ........................................................................................................................ xii CHAPTER 1 : INTRODUCTION ............................................................................................ 1 1.1 Magnetite ........................................................................................................................ 1 1.2 History of Magnetite ....................................................................................................... 2 1.3 Magnetite in Nature ........................................................................................................ 2 1.4 Nanoscale Magnetite ....................................................................................................... 3 1.5 Improvement of Drinking Water .................................................................................... 3 CHAPTER 2 : LITERATURE REVIEW ................................................................................. 6 2.1 Introduction ..................................................................................................................... 6 2.2 Magnetism ....................................................................................................................... 6 2.3 Uses ofNanoscale Magnetite ........................................................................................ 10 2.4 Magnetic Applications of Magnetite and Magnetic Separations .................................. 11 2.5 Arsenic as a World Health Issue ................................................................................... 12 2.6 Uranium as a World Health Issue ................................................................................. 12 2.7 Batch Isotherms for Adsorption .................................................................................... 13 2.8 Adsorption Applications ofNanoscale Magnetite ........................................................ 14 2.9 Biomedical Applications ofNanoscale Magnetite ....................................................... 15 2.10 Biomedical Applications ofNanoscale Magnetite Utilizing Magnetic Separation .... 16 2.11 Improving the Synthesis of CdSe Quantum Dots ....................................................... 18 CHAPTER 3 : NANOPARTICLE SYNTHESIS AND SURF ACE MODIFICATION ........ 19 3.1 Introduction ..................................................................................................................

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