DISSERTATION CATALYTIC STRATEGIES FOR ENHANCING ELECTROCHEMICAL OXIDATION OF 1,4-DIOXANE: TiO2 DARK ACTIVATION AND MICROBIAL STIMULATION Submitted by Jeramy R. Jasmann Department of Chemistry In partial fulfillment of the requirements For the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Summer 2016 Doctoral Committee: Advisor: Thomas Borch Co-Advisor: Jens Blotevogel Delphine Farmer William Sanford James Neilson Michael Elliot Copyright by Jeramy Roland Jasmann 2016 All Rights Reserved ABSTRACT CATALYTIC STRATEGIES FOR ENHANCING ELECTROCHEMICAL OXIDATION OF 1,4-DIOXANE: TiO2 DARK ACTIVATION AND MICROBIAL STIMULATION 1,4-dioxane, a probable human carcinogen, is an emerging contaminant currently being reviewed by the U.S. Environmental Protection Agency for possible health-based maximum contaminant level regulations. As both stabilizer in commonly used chlorinated solvents and as a widely used solvent in the production of many pharmaceuticals, personal care products (PPCPs), 1,4-dioxane has been detected in surface water, groundwater and wastewater around the U.S. It is resistant to many of the traditional water treatment technologies such as sorption to activated carbon, air stripping, filtering and anaerobic biodegradation making 1,4-dioxane removal difficult and/or expensive. State-of-the art technologies for the removal of 1,4-dioxane usually apply advanced oxidation processes (AOPs) using strong oxidants in combination with UV-light and sometimes titanium dioxide (TiO2) catalyzed photolysis. These approaches require the use of expensive chemical reagents and are limited to ex situ (i.e. pump and treat) applications. Here, at Colorado State University’s Center for Contaminant Hydrology, innovative flow-through electrolytic reactors have been developed for treating groundwater contaminated with organic pollutants. The research presented in this dissertation has investigated catalytic strategies for enhancing electrochemical oxidation of 1,4-dioxane in flow-through reactors. Two types (abiotic and biotic) of catalysis were also explored: (1) dark, electrolytic activation of insulated, inter-electrode TiO2 pellets to catalyze the degradation of organic pollutants in the ii bulk solution by reactive oxygen species (ROS), and (2) adding permeable electrodes upstream of dioxane-degrading microbes, Pseudonocardia dioxanivorans CB1190, to pre-treat mixed contaminant water and provide O2 stimulation to these aerobic bacteria. For the abiotic form of catalysis, we characterized the properties of novel TiO2 inter- electrode material, and elucidated the properties most important to its catalytic activity, using 1,4-dioxane as the model contaminant. The TiO2 was novel in its use as an “inter-electrode” catalyst (not coated on the electrode and not used as a TiO2 slurry) and in the mechanism of its catalytic activation occurring in dark (not photocatalysis) and insulated (not typical electrocatalysis) conditions. Further studies were performed using electrochemical batch reactors and probe molecules in order to gain mechanistic insights into dark catalysis provided by detached TiO2 pellets in an electrochemical system. The results of our investigations show that electrolytic treatment, when used in combination with this catalytically active inter-electrode material, can successfully and efficiently degrade 1,4-dioxane. Benefits of catalyzed electrolysis as a green remediation technology are that (1) it does not require addition of chemicals during treatment, (2) it has low energy requirements that can be met through the use of solar photovoltaic modules, and (3) it is very versatile in that it could be applied in situ for contaminated groundwater sites or installed in-line on above-ground reactors to remediate contaminated groundwater. Although, 1,4-dioxane appears to be resistant to natural attenuation via anaerobic biodegradation, some aerobic bacteria have been shown to metabolize and co-metabolize 1,4- dioxane. For example, growth-supporting aerobic metabolism/degradation of 1,4-dioxane by Pseudonocardia dioxanivorans CB1190, has been demonstrated in laboratory studies. However, previous studies showed that this biodegradation process is inhibited by the presence of iii chlorinated solvents such as 1,1,1-trichlorethane (1,1,1-TCA) and trichloroethene (TCE). This could dramatically impact the success for in situ 1,4-dioxane biodegradation with P. dioxanivorans since chlorinated solvents are common co-contaminants of 1,4-dioxane. Our previous investigations into electrolytic treatment of organic pollutants both ex and in situ showed that effective degradation of chlorinated solvents like TCE was achievable. In addition, the electrolysis of water generates molecular O2 required by the CB1190 bacteria as well. This led us to hypothesize that the generation of O2 could enhance aerobic biodegradation processes, and the concurrent degradation of co-solvents could reduce their inhibitory impact on 1,4- dioxane biodegradation. In flow-through sand column studies presented here, we investigate the electrolytic stimulation of Pseudonocardia dioxanivorans CB1190, with the expectation that anodic O2 generation would enhance aerobic biodegradation processes, and concurrent degradation of TCE would reduce the expected inhibitory impact on 1,4-dioxane biodegradation. Results show that when both electrolytic and biotic processes are combined, oxidation rates of 1,4-dioxane substantially increased suggesting that aerobic biodegradation processes had been successfully stimulated. In summary, the results of this dissertation provide evidence of (1) efficient removal of recalcitrant 1,4-dioxane, especially with the addition of inter-electrode TiO2 catalysts, (2) elucidate possible mechanistic pathways for electro-activated dark TiO2 catalysis, and (3) provide evidence for successful synergistic performance for electro-bioremediation treatment during simulated mixed, contaminant plume conditions. iv ACKNOWLEDGEMENTS Thank you God for this amazing opportunity and for bringing so many special people into my life during this time. Thank you God for listening to my prayers, providing me with blessing when I needed them most [Matthew 6:25-34], and helping my family to make it through this challenging financial season as an intact, active, healthy and truly joyous family of five: “The Jasmann Five” (only we don’t sing…well). By diving deeper into science, I continue to be impressed by your creation and the natural laws you have put into motion [Romans 1:19-20]. These laws of chemistry, thermodynamics, electromagnetism and others, are what provide endless discoveries for us to make as scientist. I would like to thank my advisors Dr. Thomas Borch and Dr. Jens Blotevogel who have provided invaluable guidance and helped me to establish a remarkable foundation in hypothesis- driven research. Without their advice, support, and friendship, my journey to this publication would not have been possible. I would like to thank Dr. Borch for his enthusiasm for science and for working with me to find an interdisciplinary research problem with applicable outcomes relevant to the protection of human health and the environment; it was exactly what I had hoped for. I would like to thank Dr. Blotevogel for his desire to research practical remediation solutions for recalcitrant environmental contaminants (a tough and uncertain field at times), and his outstanding intellectual contributions when discussing difficult scientific problems, especially when providing critical revisions and structure to my writing near the end of my time here. I would like to thank Dr. Tom Sale of the Center for Contaminant Hydrology (CCH) who has been a close collaborator throughout my doctoral work and who made it possible for my entire Ph.D. program to be funded by industry-university collaborations he has formed over the years. v Dr. Sale has an uncanny ability to distill industry problems down to their most important needs in order to target the problem and investigate solutions most efficiently. I would also like to thank Gary Dick, our laboratory manager in the CCH, who was instrumental in the experimental design phase when building my flow-through electrochemical reactors. His retirement midway through my program left a gaping hole, losing his unmatched mechanical expertise and losing the continuous stream of oddly funny jokes and quips he seemed to always have at the ready. I would like to recognize the financial assistance that made this work possible. I thank Dr. Masayuki Shimizu for conducting the synchrotron radiation-based XRD with me at the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Thank you to Dr. Yury Desyaterik, Ali Boris and Robert Young for their patient guidance in the use of LC/ESI-TOF-MS, and LC/UV, respectively. My work was primarily supported by E. I. du Pont de Nemours and Company (DuPont) and The Chemours Company, along with complementary support from General Electric, three outstanding companies who recognize the environmental concern posed by 1,4-dioxane, and were committed to fully funding my research to discover novel, effective, and economical remediation options. I met many fellow researchers and students throughout this processes that I consider both friends and colleagues. Many members of the Borch group and CCH laboratory group have made lasting impressions