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The overall objective of this research was to develop and assess a new method, named remedial extraction and catalytic hydrodehalogenation (REACH), for removing and destroying soil contaminants. In particular, I considered hydrophobic halogenated organic compounds (HHOCs). In this research, I developed a closed-loop treatment process that catalytically destroys the contaminants of concern, and does not generate a secondary waste stream. Mixtures of water and ethanol appear to be good candidates for the extraction of 1,2,4,5-tetrachlorobenzne (TeCB) or pentachlorophenol (PCP) from contaminated soil. Palladium-catalyzed hydrodehalogenation (HDH) was applied for destroying TeCB or PCP in mixtures of water and ethanol in a batch mode. The experimental results are all consistent with a Langmuir-Hinshelwood model for heterogeneous catalysis. Major findings that can be interpreted within the Langmuir- Hinshelwood framework are as follows: the rate of HDH depends strongly on the solvent composition, increasing as the water fraction of the solvent increases; the kinetics of the HDH reaction are apparently first-order with respect to the concentration of TeCB in the solvent; and the HDH rate increases as the catalyst concentration in the reactor increases. Also, TeCB is converted rapidly and quantitatively to benzene, with only trace concentrations of 1,2,4-trichlorobenzene appearing as a reactive intermediate. PCP is transformed to phenol by sequential reductive dehalogenation to tetrachlorophenols, then to trichlorophenols, then to phenol. The degradation of PCP does not follow firstorder kinetics, probably because of competitive reactions of intermediate products that are generated during PCP degradation. Following the batch studies, the REACH technology was applied in continuous mode under baseline conditions for a span of 7 weeks to treat soils that had been synthetically contaminated by HHOCs in the laboratory. Extraction of TeCB and PCP from soils was almost completed within two days by a 50:50 mixture of water and ethanol. Higher reaction rates were observed for TeCB than for PCP. The activity of the catalyst was slowly lost as contaminant mass was removed from the soil. The deactivated catalyst was successfully regenerated with a dilute sodium hypochlorite solution. The results of this research suggest that REACH could be a viable technology for some contaminated soils.

Remediation of trichloroethylene (TCE) and other chlorinated solvents is of great concern due to their toxicity and their persistence in the environment. Iron has been used extensively in the past decade as a subsurface reactive agent for the remediation of dense, nonaqueous-phase liquids (DNAPLs). Permeable reactive barrier walls (PRBW) have been installed at many sites around the country to treat contaminated plumes resulting from the presence of DNAPL pools. The use of zero-valent metals, such as iron, to effectively reductively dechlorinate DNAPLs has been employed as the reactive material in these PRBWs (Gillham et al., 1993). However, limited work has been conducted to compare the kinetics of TCE degradation related to various manufacturing sources of iron and the pretreatment the iron receives prior to subsurface installation. Determination of iron reactivity through kinetic studies makes it possible to compare different types of iron and the effects that pretreatment has on reactivity. This research utilized rate studies, scanning electron microscopy, and BET surface area analysis for iron particles that were obtained from several sources. Peerless Metal Powders and Abrasive, Inc., Connelly-GPM, Inc., and Alfa Aesar Inc., produced the iron particles using various manufacturing techniques, and nanoscale iron was synthesized in our laboratory. By utilizing zero-headspace batch vial experiments and gas chromatography, changes in TCE concentration were determined. The data obtained produced linear first order rate plots from which dehalogenation rate constants were obtained. The rate constants were normalized by iron mass, solution volume, and surface area. The pretreatment techniques employed in this study, including ultrasonication and acid washing, demonstrated a beneficial effect by removing oxide precipitates from the iron surface, thus increasing the reactivity of the iron. Mass loading studies revealed how physical factors, associated with the experimental setup, could influence reaction rates. Surface area studies confirmed that the smaller iron particles, such as the nanoscale iron, have a greater surface area per unit mass. The large mass and volume normalized rate constant, kMV, obtained for the nanoscale iron was a result of this high surface area. However, the calculated surface area normalized rate constant, kSA, for the nanoscale iron was significantly lower than those for the granular iron samples tested. It was concluded that differences in surface area normalized rate constants, between different iron particle types, could be attributed to inherent characteristics of the iron, such as composition and crystal structure.

REDUCTIVE DEHALOGENATION OF GAS-PHASE TRICHLOROETHYLENE USING HETEROGENEOUS CATALYTIC AND ELECTROCHEMICAL METHODSXiumin Ju, Ph.D.The University of Arizona, 2005Director: Dr. Robert G. ArnoldThe first part of this work investigates catalytic hydrodechlorination (HDC) of gas-phase trichloroethylene (TCE) using 0.5 wt.% Pt/g-Al2O3 and 0.0025 wt.% Pt/SiO2 in packed-bed reactors. TCE was efficiently transformed on the platinum surface using H2 as reducing agent. The main products of the reaction were ethane and chloroethane. In the case of Pt/Al2O3, more than 94% TCE conversion efficiency was maintained for over 700 hours of operation at 100ºC at a residence time of 0.37 seconds. At 22ºC, severe catalyst deactivation was observed. Catalyst deactivation was attributed to coking and chlorine poisoning. A series of treatments including (i) hydrogen gas addition at high temperature (oxygen free) to remove chlorine and (ii) oxygen addition at 500ºC to remove coke were attempted to regenerate the deactivated catalyst. Only hydrogen treatment partially restored catalyst activity. When using Pt/SiO2, catalyst deactivation was severe even at 100ºC, probably due to low surface area of Pt and the silica support. Adding KOH to the packed Pt/SiO2 catalyst during (otherwise) normal operation slowed catalyst deactivation. Adding O2 to the influent improved catalyst activity and slowed deactivation.The second part of this research involves the destruction of gas-phase TCE using an electrochemical reactor similar in design of a polymer electrolyte membrane (PEM) fuel cell. With a proton-conducting membrane in the middle, the anode and cathode comprised of carbon cloth and carbon-black-supported Pt were hotpressed together to form a membrane electrode assembly (MEA). TCE contaminated gas streams were fed to the cathode side of the fuel cell, where TCE was reduced to ethane and hydrochloric acid. The results suggest that TCE reduction occurs via a catalytic reaction with atomic hydrogen that is reformed on the cathode's surface rather than an electrochemical reduction via direct electron transfer. Substantial conversion of TCE was obtained, even in the presence of molecular oxygen in the cathode chamber. The process was modeled successfully by conceptualizing the cathode chamber as a plug flow reactor with a continuous source of H2(g) emanating from the boundary.

Doctor of Philosophy / Department of Chemistry / Stefan Kraft / Highly toxic aromatic halogenated compounds such as PCB’s, PCDF’s and PCDD’s act as persistent organic pollutants and can bio-accumulate. These compounds are highly stable to oxidation, reduction and thermal degradation. Current remediation technologies are expensive and can cause the formation of even more toxic byproducts. It is clear that an environmentally friendly and inexpensive remediation technology is required. Our goal was the synthesis of dehalogenation catalysts incorporating aromatic side arms for the pre-concentration of the substrates to the catalysts. We envisioned that aromatic side arms would allow the aggregation of catalyst and substrate to form a pre-complex that would enhance rates of dehalogenation. Rapid and stereochemically predictable synthesis of N and C functionalized nickel cyclam complexes were a priority for this project. Synthesis of N-functionalized cyclam molecules and subsequent metal incorporation proceeds smoothly to form trans(III) nickel cyclam complexes. However longer reaction times, initiation periods and short catalyst lifetimes made these complexes unsuitable for long-term study. Cyclization of dipeptides and tetrapeptides using a metal template in basic conditions led to the formation of cyclopeptide nickel complexes with stereochemistry retained from the peptide precursors. Free cyclopeptides could be isolated from the nickel complexes by treatment with HCl. Cyclopeptides are reduced to the cyclam molecules via a LAH reduction in low to moderate yields. Nickel incorporation into the cyclam molecules produced C-functionalized nickel catalysts with stereochemical integrity maintained throughout the synthesis. Intermolecular CH-π interactions can be seen in the solid state for the nickel cyclam complexes with aromatic side arms. Reduction data show that the C-functionalized catalysts do not show improved rates of reduction for several aromatic substrates but small rate enhancements are observed for the reduction of chloronaphthalene over the unfunctionalized catalyst.

Polymers containing bulky tetraphenylthiophene (TP) moieties were prepared by different coupling reactions. Firstly, 2,5-bis(4-bromophenyl)-3,4-diphenylthiophene (TP-Br) was coupled together by either NiCl2/PPh3 or n-BuLi to form polymers with TP as the repeat unit. The resulting polymers (PTP-NiCl2 and PTP-BuLi) are easily soluble in organic solvents and are photoluminescent (PL) materials (

Perfluorooctane sulfonate (PFOS) and related perfluoroalkyl surfactants (PFAS) are ubiquitous contaminants of increasing public concern due to their environmental persistence, toxicity, and bioaccumulation. These perfluorinated compounds have been used for more than half a century in a wide variety of industrial and consumer products ranging from stain repellents such as Teflon® to aqueous fire-fighting foams and to grease-proof food packing. The public health and environmental risks posed by PFAS have driven environmental agencies and the industry to restrict their use to specific applications where they cannot be replaced by other chemicals. The sources and pathways of PFOS and its derivatives in the environment are not well understood. Analysis of environmental samples is critical to understand the fate, transport and persistence of these emerging contaminants. Techniques based on fluorine nuclear magnetic resonance (¹⁹F NMR) spectroscopy and high performance liquid chromatography (HPLC) with suppressed conductivity detection were successfully developed to monitor the presence of PFAS in water samples. Chromatographic separation of C₄ to C₈ PFAS surfactants was achieved using a C₁₈ reversed-phase column and a mobile phase consisting of a mixture of boric acid and acetonitrile at mixing ratios ranging from 75:25 to 45:55 (v/v). The combination of these two techniques was very effective for characterization and routine quantification of PFOS and related chemicals. Analytical methods based on ¹⁹F NMR, HPLC-suppressed conductivity detection, and liquid chromatography with tandem mass spectrometry (LC-MS/MS) were employed to characterize commercial PFOS samples. Linear and branched PFOS isomers in a percentage ratio of 75:25 were identified. Municipal wastewater treatment systems are one of the major sources of PFAS emissions into the environment. The presence of PFAS in sewage sludge from two wastewater treatment plants in Tucson, Arizona, was investigated. Sludge samples were washed with acetic acid and extracted with a mixture of acetic acid and methanol. The extract was cleaned and concentrated by means of solid phase extraction. LC-MS/MS operating in the selective ion monitoring (SIM) mode was employed to assess the presence of perfluorosulfonates, perfluorosulfonamides, and perfluorocarboxylates in sewage sludge samples. PFOS was the only perfluoroalkyl chemical detected in municipal sludge samples at a concentration of 77 ± 5 g kg⁻¹ sludge dry weight. Cost-effective treatment techniques for removing PFAS from industrial effluents are needed to minimize discharges of these pollutants. Reductive dehalogenation is widely applied to the degradation of highly chlorinated compounds. Hence, the susceptibility of PFOS and related compounds to biological and chemical reductive dehalogenation was evaluated in batch assays. PFAS were not reductively dehalogenated by different microbial consortia even after periods of incubation exceeding 2 y, confirming the high resistance of these compounds to microbial degradation. The anaerobic biodegradability of PFOS and perfluorobutane sulfonate (PFBS) samples exposed to electrochemical pretreatment with boron-doped diamond film electrodes was also investigated. The oxidation decreased the concentration of PFAS and dissolved organic carbon in solution, confirming the destruction of these compounds. However, the oxidative treatment did not enhance the susceptibility of PFAS to microbial degradation even after extended periods of incubation (> 1 y). In contrast, PFOS was reductively dehalogenated with a biomimetic system based on vitamin B12 as the catalyst and Ti(III) citrate as the reducing agent. The optimal treatments conditions of the reaction were 260 μM vitamin B₁₂, 36 mM Ti(III) citrate, 70°C and solution pH 9.0. Interestingly, branched PFOS isomers were more prone to degradation by vitamin B₁₂ catalysis compared to the linear isomer. Removal of 3 mol Fper mol of technical PFOS and 12 mol F- per mol of branched PFOS isomers was achieved. Defluorination of PFOS was also observed at environmental relevant conditions of 30°C and pH 7.0, albeit at lower degradation rates. Fluoride and carbon dioxide were identified as the major products of the chemical defluorination. Traces of partially fluorinated volatile compounds were also detected in the headspace. The feasibility of removing PFAS compounds from aqueous streams by sorption onto granular activated carbon (GAC), zeolite, and wastewater treatment sludge was examined in batch isotherm experiments. The fluorocarbon chain and the functional group influenced sorption of the anionic surfactants, PFOS adsorbed more strongly to GAC than perfluorooctanoic acid (PFOA) and PFBS. Activated carbon showed the highest affinity for PFOS (Freundlich K(F) values of 36.7 to 60.9) followed by the hydrophobic, high-silica zeolite NaY (Si/Al 80, K(F) of 31.8) and lastly anaerobic sludge (K(F) of 0.95 to 1.85). GAC sorption is a suitable treatment for the removal of anionic perfluoroalkyl surfactants when present at low concentrations. Fluoride has been identified as the major product of the reductive dehalogenation of PFOS and derivatives. Thus, the toxicity of inorganic fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes was also studied. Fluoride concentrations ranging from 18 to 43 mg L⁻¹ caused 50% inhibition (IC₅₀) of the activity of propionate- and butyratedegrading microorganisms and of acetate-utilization by methanogens evaluated under mesophilic and thermophilic conditions. All other microbial populations evaluated in this study, i.e., glucose fermenters, aerobic glucose-degrading heterotrophs, denitrifying bacteria, and H₂-utilizing methanogens tolerated fluoride at very high concentrations (> 500 mg L⁻¹). In the same manner, H₂-utilizing methanogens also tolerated PFOS and PFBS at concentrations as high as 200 and 500 mg L⁻¹, respectively.

abstract: Organic compounds are influenced by hydrothermal conditions in both marine and terrestrial environments. Sedimentary organic reservoirs make up the largest share of organic carbon in the carbon cycle, leading to petroleum generation and to chemoautotrophic microbial communities. There have been numerous studies on the reactivity of organic compounds in water at elevated temperatures, but these studies rarely explore the consequences of inorganic solutes in hydrothermal fluids. The experiments in this thesis explore new reaction pathways of organic compounds mediated by aqueous and solid phase metals, mainly Earth-abundant copper. These experiments show that copper species have the potential to oxidize benzene and toluene, which are typically viewed as unreactive. These pathways add to the growing list of known organic transformations that are possible in natural hydrothermal systems. In addition to the characterization of reactions in natural systems, there has been recent interest in using hydrothermal conditions to facilitate organic transformations that would be useful in an applied, industrial or synthetic setting. This thesis identifies two sets of conditions that may serve as alternatives to commonplace industrial processes. The first process is the oxidation of benzene with copper to form phenol and chlorobenzene. The second is the copper mediated dehalogenation of aryl halides. Both of these processes apply the concepts of geomimicry by carrying out organic reactions under Earth-like conditions. Only water and copper are needed to implement these processes and there is no need for exotic catalysts or toxic reagents. / Dissertation/Thesis / Masters Thesis Geological Sciences 2020

This work focused on using a microbubble dispersion to deliver hydrogen and carbon dioxide to anaerobic consortia to stimulate their ability to reductively dehalogenate tetrachloroethylene all the way to ethene and ethane. A continuous flow system, consisting of six anaerobic soil column bioreactors, inoculated with sediments from Virginia Tech's Duck Pond, was used for this study. Two columns received microbubbles containing hydrogen and carbon dioxide, two received sodium propionate, and two were not fed a substrate. A 30 micromolar PCE solution was delivered to the consortia at 3 ml/min. Microbubbles containing a mixture of 90% hydrogen and 10% carbon dioxide were effectively produced in a closed spinning disk generator, and were acceptable for delivering the gases to the columns. After the biodegradation study was completed, the microbubbles were found to have a pH of 4.4, due to the carbon dioxide. Microbubbles amended with NaOH to 0.01 molar yielded pH neutral microbubbles with improved stability. Methane was measured in all six columns throughout the experiment, verifying that methanogens were present. Methane levels were highest in the propionate columns, showing the the methanogens there were more active. Methane levels in the microbubble columns were similar to those in the control columns. Propionate and acetate were not detected in the columns where propionate was fed, showing that proton reducers and acetoclastic methanogens were both active. Recovery of PCE and the degradation products was almost 90% in the microbubble and control columns where most of the PCE was recovered in the effluent. The predominant product in both systems was TCE, although some ethene was detected in all four columns. The control consortia produced TCE averaging about five micromolar while the microbubble columns averaged about two micromolar TCE. One of the components of the microbubbles probably caused the lowered amounts of PCE reduction. That some ethene was seen in the microbubble columns suggests different conditions can be found to stimulate the further reduction of PCE with hydrogen and carbon dioxide microbubbles. The product recovery in the propionate columns was about 64%. Over half of the injected PCE was dechlorinated to ethene and ethane. / Ph. D.

This thesis consists of two major chapters, each with its own introduction, experimental section and discussion. The TG4T/daunomycin and G4/daunomycin complexes described in Chapter One are two out of only five crystallographic quadruplex/ligand structures reported to date. In both structures daunomycin molecules stack onto a terminal G quartet preventing the G4 quadruplex from destacking and unwinding. The number of interacting ligand molecules depends on the quadruplex structure itself. The G4 quadruplex can accommodate four daunomycin molecules within one layer, while the TG4T tetraplex only accommodates three. In both structures daunosamine moieties form hydrogen bonds with the quadruplex but only daunosamine moieties from the TG4T/daunomycin structure make slight incursions into the quadruplex grooves. Both structures are stabilised by π-π interactions, hydrogen bonds, Van der Waals contacts and electrostatic interactions. The daunomycin/TG4T complex is the first ever reported and the only structure where a ligand interacts directly with the quadruplex groove. Chapter Two describes nine crystal structures of Hoechst 33258 analogues with d(CGCAAATTTGCG)2 and d(CGCGAATTCGCG)2 oligonucleotides, and is divided into two sections. Section A includes seven structures with Halogenated Hoechst 33258 analogues that are potential agents in radiotherapy, phototherapy, radioimmunotherapy or photoimmunotherapy, and the structure of the precursor. In all of the examined complexes the ligand binds to the minor groove but not all halogen substituents refine to 100% occupancy. The refined occupancies of the halogen atoms reveal that the degree of carbon-halogen cleavage is highest for ortho and lowest for para substitution. Among meta substituents pointing outside the minor groove, bromine atoms had a higher occupancy than the larger iodines. The position of the halogen atom in the minor groove is influenced by additional substituents on the phenyl ring. In most cases the bulky halogen atom is facing outside of the minor groove. Only in the 3-iodo-5-isopropylHoechst complex is iodine positioned towards the floor of the groove allowing the big isopropyl group to face outside. Section B describes the structure of a carborane-containing ligand (JW-B) bound to the minor groove of d(CGCAAATTTGCG)2. The analysis shows that is possible to position boron-rich moieties close to the cell nucleus, and JW-B may have potential in Boron Neutron Capture Therapy. / Data file restricted at the request of the author, but available by individual request, use the feedback form to request access.