University of Kentucky UKnowledge Theses and Dissertations--Chemistry Chemistry 2017 ARSENIC REMOVAL WITH A DITHIOL LIGAND SUPPORTED ON MAGNETIC NANOPARTICLES John Hamilton Walrod II University of Kentucky, [email protected] Author ORCID Identifier: https://orcid.org/0000-0003-1875-6546 Digital Object Identifier: https://doi.org/10.13023/ETD.2017.314 Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Walrod, John Hamilton II, "ARSENIC REMOVAL WITH A DITHIOL LIGAND SUPPORTED ON MAGNETIC NANOPARTICLES" (2017). Theses and Dissertations--Chemistry. 83. https://uknowledge.uky.edu/chemistry_etds/83 This Doctoral Dissertation is brought to you for free and open access by the Chemistry at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Chemistry by an authorized administrator of UKnowledge. For more information, please contact [email protected]. STUDENT AGREEMENT: I represent that my thesis or dissertation and abstract are my original work. Proper attribution has been given to all outside sources. I understand that I am solely responsible for obtaining any needed copyright permissions. I have obtained needed written permission statement(s) from the owner(s) of each third-party copyrighted matter to be included in my work, allowing electronic distribution (if such use is not permitted by the fair use doctrine) which will be submitted to UKnowledge as Additional File. I hereby grant to The University of Kentucky and its agents the irrevocable, non-exclusive, and royalty-free license to archive and make accessible my work in whole or in part in all forms of media, now or hereafter known. I agree that the document mentioned above may be made available immediately for worldwide access unless an embargo applies. I retain all other ownership rights to the copyright of my work. I also retain the right to use in future works (such as articles or books) all or part of my work. I understand that I am free to register the copyright to my work. REVIEW, APPROVAL AND ACCEPTANCE The document mentioned above has been reviewed and accepted by the student’s advisor, on behalf of the advisory committee, and by the Director of Graduate Studies (DGS), on behalf of the program; we verify that this is the final, approved version of the student’s thesis including all changes required by the advisory committee. The undersigned agree to abide by the statements above. John Hamilton Walrod II, Student Dr. David A. Atwood, Major Professor Dr. Mark A. Lovell, Director of Graduate Studies ARSENIC REMOVAL WITH A DITHIOL LIGAND SUPPORTED ON MAGNETIC NANOPARTICLES Dissertation A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By John Hamilton Walrod II Lexington KY Director: Dr. David A. Atwood, Professor of Chemistry Lexington KY 2017 Copyright © John Hamilton Walrod 2017 ABSTRACT OF DISSERTATION ARSENIC REMOVAL WITH A DITHIOL LIGAND SUPPORTED ON MAGNETIC NANOPARTICLES Exposure to arsenic (As) in water, the ubiquitous toxin that poses adverse health risks to tens of millions, is the result of both anthropogenic and geochemical mobilization. Despite recent publicity and an increased public awareness, the dangers associated with arsenic exposure rank among the top priorities of public health agencies globally. Existing sequestration applications mainly include reductions and adsorption with zero-valent metals and their oxides. The performance of adsorption media is known to preferentially favor aqueous As(V) over As(III) due to the charge of the dissolved oxyanion. Magnetic nanoparticles (MNP) have been the focus of multidisciplinary research efforts for the removal of aqueous toxic metals and metalloids since they can be magnetically separated from the treated water. This improves isolation and allows for regeneration of the MNP, reducing cost and resource consumption. This research is focused on As(III & V) sequestration through the use of synthetic ligands N,N’bis(2- mercaptoethyl)isophthalamide (abbreviated BDTH2) and 2,2’- (isophthaloybis(azanaediyl))bis-3-mercaptopropanoic acid (abbreviated ABDTH2). Additionally, As(III) sequestration with ABDTH2 functionalized on silica core-shell MNP (ABDTH2 MNP), magnetite MNP (ABDTH2@MNP), and commercial silica beads (ABDTH2 Si60) is demonstrated. Both BDTH2 and ABDTH2 are effective precipitation agents for the removal of As(III) through the formation of S-As covalent bonds. ABDTH2 MNP reduced a 200 ppb As(III) batch solution to below 10 ppb at pH 5,7, and 9. Additionally, complete removal was achieved in the presence of anions at concentrations of 200, 500, and 1000 ppb. This system was evaluated for the removal of total arsenic from industrial solutions accumulated during the production of renewable biogas in landfills. Direct precipitation with BDTH2 and ABDTH2 was inhibited by the complex matrix. However, batch removal with ABDTH2@MNP was effective in removing 82% of the inorganic arsenic. Sequestration of arsenic and speciation from these industrial solutions remains a challenge. KEYWORDS: Arsenic Removal, Magnetic, Nanoparticles, Water Filtration, Chelation John Hamilton Walrod II Date: 7/28/2017 ARSENIC REMOVAL WITH A DITHIOL LIGAND SUPPORTED ON MAGNETIC NANOPARTICLES By John Hamilton Walrod II Dr. David A. Atwood Director of Dissertation Dr. Mark A. Lovell Director of Graduate Studies Date: 7/28/2017 ACKNOWLEDGEMENT I would like to thank Dr. Atwood and group members for the experiences we shared in the lab. I am very grateful to the staff at Environmental Research Training Laboratories (ERTL), Dr. Gary Jacobs and Gerald Thomas at the Center for Applied Energy Research (CAER), Dr. Nadine Kabengi at Georgia State University, and Dr. DeLong and group members from the Physics Department at UK for technical assistance operating various analytical instruments. I would also like to thank my parents, Dr. John Hamilton Walrod and Jane Walrod, for their endearing support. I will always cherish our late night phone calls about life. I would also like to thank my wife, Jennilee Walrod, and daughter, Emma Walrod. None of this would have been possible without their love and support. iii TABLE OF CONTENTS ACKNOWLEDGEMENT ................................................................................................. iii LIST OF TABLES ............................................................................................................. ix LIST OF SCHEMES.......................................................................................................... xi LIST OF FIGURES ......................................................................................................... xiii LIST OF ABBREVIATIONS AND SYMBOLS ............................................................. xv Arsenic ............................................................................................................... 1 1.1 Arsenic Sulfur Chemistry ...........................................................................................1 1.2 Current Remediation ................................................................................................10 1.3 Limitations of Sulfhydryl Based Strategies .............................................................19 1.4 Conclusions ..............................................................................................................21 BDTH2 and ABDTH2: Dithiol Chelating Ligands ........................................... 21 2.1 Introduction ..............................................................................................................21 2.2 Results and Discussion .............................................................................................25 2.2.1 Synthesis and Characterization ......................................................................... 25 2.3 Experimental ............................................................................................................27 2.3.1 Reagents............................................................................................................ 27 2.3.2 Analytical Techniques ...................................................................................... 27 2.4 Synthesis ...................................................................................................................28 2.4.1 BDTH2 Synthesis .............................................................................................. 28 2.4.1.1 Charcterization ........................................................................................... 28 2.4.2 ABDTH2 Synthesis ........................................................................................... 28 2.4.2.1 Characterization ......................................................................................... 29 2.5 Conclusions ..............................................................................................................29 Aqueous Arsenite Precipitation with Dithiols BDTH2 and ABDTH2.............. 30 3.1 Introduction ..............................................................................................................30 3.1.1 BDTH2 and ABDTH2 Interactions with Aqueous Arsenite ............................. 30 3.1.2 Arsenic Leaching and Soft Metal Preferences ................................................. 32 iv 3.1.3 BDTH2 and ABDTH2 Arsenate Interactions ...................................................