Electrochemical capacitors, now often termed supercapacitors, are high power electrochemical energy storage devices that complement or replace high power batteries in applications ranging from wind turbines to hybrid engines to uninterruptable power supplies to electronic devices. My dissertation explores the applications of relatively uncommon techniques for both supercapacitor material syntheses and gaining better mechanistic understanding of factors impacting electrochemical performance of supercapacitors. From fundamental ion electroadsorption studies made possible by using small angle neutron scattering (SANS), to the systematic investigations of coating thickness and microstructure in metal oxide / carbon nanocomposite electrodes realized through the novel use of the atomic layer deposition (ALD) technique, new avenues of material characterization and fabrication have been studied. In this dissertation I first present the motivation to expand the knowledge of supercapacitor science and technology, and follow with an in-depth literature review of the state of the art. The literature review covers different types of supercapacitors, the materials used in the construction of commercial and exploratory devices, an exploration of the numerous factors which affect supercapacitor performance, and an overview of relevant materials synthesis and characterization techniques The technical objectives for the work performed in this dissertation are then presented, followed by the contributions that I made in this field in my two primary research thrusts: advances to the understanding of ion electroadsorption theory in both aqueous and organic electrolytes through the development of a SANS-based methodology, and advances to metal-oxide carbon nanocomposites as electrodes through the use of ALD. The understanding of ion electro-adsorption on the surface of microporous (pores < 2 nm) solids is largely hindered by the lack of experimental techniques capable of identifying the sites of ion adsorption and the concentration of ions at the nanoscale. In the first research thrust of my dissertation, I harness the high penetrating power and sensitivity of neutron scattering to isotope substitution to directly observe changes in the ion concentration as a function of the applied potential and the pore size. I have conducted initial studies in selected aqueous and organic electrolytes and outlined the guidelines for conducting such experiments for the broad range of electrode-ions-solvent combinations. I unambiguously demonstrate that depending on the solvent properties and the solvent-pore wall interactions, either enhanced or reduced ion electro-adsorption may take place in sub-nanometer pores. More importantly, for the first time I demonstrate the route to identify the critical pore size below which either enhanced or reduced electrosorption of ions takes place. My studies experimentally demonstrate that poor electrolyte wetting in the smallest pores may indeed limit device performance. The proposed methodology opens new avenues for systematic in-situ studies of complex structure-property relationships governing adsorption of ions under applied potential, critical for rational optimization of device performance. In addition to enhancing our understanding of ion sorption, there is a critical need to develop novel supercapacitor electrode materials with improved high-energy and high-power characteristics. The formation of carbon-transition metal oxide nanocomposites may offer unique benefits for such applications. Broadly available transition metal oxides, such as vanadium oxide, offer high ion storage capabilities due to the broad range of their oxidation states, but suffer from high resistivities. Carbon nanomaterials, such as carbon nanotubes (CNT), in contrast are not capable to store high ion content, but offer high and readily accessible surface area and high electrical conductivity. In the second research thrust of my thesis, by exploiting the ability of atomic layer deposition (ALD) to produce uniform coatings of metal oxides on CNT electrodes, I demonstrated an effective way to produce high power supercapacitor electrodes with ultra-high energy capability. The electrodes I developed showed stable performance with excellent capacitance retention at high current densities and sweep rates. Electrochemical performance of the oxide layers were found to strongly depend on the coating thickness. Decreasing the vanadium oxide coating thickness to ~10 nm resulted in some of the highest values of capacitance reported to date (~1550 F·g⁻¹VOx at 1 A·g⁻¹ current density). Similar methodology was utilized for the deposition of thin vanadium oxide coatings on other substrates, such as aluminum (Al) nanowires. In this case the VOₓ coated Al nanowire electrodes with 30-50% of the pore volume available for electrolyte access show volumetric capacitance of 1390-1950 F cc⁻¹, which exceeds the volumetric capacitance of porous carbons and many carbon-metal oxide composites by more than an order of magnitude. These results indicated the importance of electrode uniformity and precise control over conformity and thickness for the optimization of supercapacitor electrodes.

Rare earth elements (REEs) are critically important for high-tech, renewable energy and defense industries. However, rare earth minerals (REMs) are stable compounds, requiring aggressive conditions to decompose them for their extraction and use. One exception is the ion-adsorption clays (IACs) that are mined in South China. They were formed in nature via the adsorption of the REE ions on clay minerals; therefore, they can be readily extracted into solution under mild conditions using the ion-exchange leaching process using (NH4)2SO4 as lixiviant. It also happens that IACs are the largest source of the heavy rare earth elements (HREEs) that are critical, especially for the defense industry. At present, more than 80% of the HREEs are produced commercially from the IACs mined in Southeast Asia. The objective of the present research was to study the fundamental mechanisms involved in the formation and processing of IACs using the ion-change leaching process. The first part of the project was the synthesis of IACs by contacting kaolinite samples with known concentrations of rare earth chloride (REECl3) solutions at different pHs and analyzing the synthetic IACs for XPS studies. It was found that the REE adsorption on kaolinite stays constant in acidic pHs. At pH 7 and above, adsorption density increases sharply, possibly due to the formation of REE(OH)3 and/or REE(OOH). The IACs formed under these conditions responded well to the ion-exchange leaching process by reducing the pH to below 7. In the second part of the study, the effect of iron (Fe3+) species co-adsorbing with REEs on the kaolinite surface was studied. Unlike the colloidal phases of IACs formed at pH > 7, the synthetic IACs formed in the presence of iron did not respond to the ion-exchange leaching process using (NH4)2SO4 as lixiviant. This problem has been solved by subjecting the synthetic IACs to a reducing condition to convert the Fe3+ to soluble Fe2+ species at pH < 7. The driving force for the standard exchange leaching process is the large differences between the hydration enthalpies of the Ln3+ ions that are in the range of -3,400 kJ/mole and that of the NH4+ ions (-320 kJ/mole). In the present work, alkylammonium ions (CnH2nNH4+) of varying chain lengths were used as novel lixiviants and obtained excellent results. Since these are surface active species, their concentrations in the vicinity of the clay minerals that are negatively charged would be substantially higher than in the bulk. As a result, it was possible to achieve the same level of leaching efficiencies as obtained using ammonium sulfate at approximately ten times lower reagent dosages. One of the problems associated with extracting REEs from coal-based clays is that the REE concentrations are typically in the range of 300 to 600 ppm, which makes it difficult to extract the critical materials economically using ion-exchange leaching and other processes. As a means to overcome this issue, the REE-bearing particles, including IACs and REMs, were liberated by blunging and subsequently upgraded using the hydrophobic-hydrophilic separation (HHS) process. The results showed that blunging outperformed grinding in liberating the REE-bearing particles from the clayey materials in coal. It was shown that one can improve blunging by increasing the disjoining in the thin liquid films present between clay and other minerals by controlling the double-layer (EDL) forces. These findings should enhance our understanding of the fundamental mechanisms involved in upgrading critical materials and thereby increase the economic viability of REE recovery from coal-based materials. / Doctor of Philosophy / Rare earth elements (REEs) play a vital role in numerous modern industries, advanced technological applications, and defense industries. The United States accounts for about 15 % of the global demand for REEs. However, the country heavily relies on imported Chinese raw materials, creating vulnerability in the U.S. supply chain. REEs are rarely found in concentrations suitable for mining, and in certain cases, extracting and processing conventional REE deposits come with significant environmental hazards. The limited availability of rare earth elements (REEs) raises concerns regarding their production despite their critical role in high-tech industries. Consequently, various federal agencies and private enterprises have recently attempted to identify promising alternative resources due to these complex challenges. REEs have been found in several major coal basins and are evidenced to be associated with coal byproducts such as kaolinite clays–one of the major host materials of IACs. This research investigates the recovery of rare earth elements (REEs) from clayey materials through various processes. Emphasis is placed on the synthesis of ion-adsorption clays from kaolinite, and the factors influencing the ion-exchange leaching process are being studied. Furthermore, the impact of iron co-adsorption on REE binding to kaolinite is being examined, and reductive leaching is being evaluated as a means to overcome the hindrance caused by iron passivating layers. Novel lixiviants are being tested as alternatives to conventional lixiviant ((NH4)2SO4) for REE extraction. The application of hydrophobic-hydrophilic separation techniques for extracting REE-bearing particles from coal clay samples is also being explored, with a comparison made between grinding and blunging processes. Overall, valuable insights into the efficient recovery of REEs from clay minerals are being obtained, contributing to the development of cost-effective and novel approaches for their extraction.

Alternating copolymers represent a special class of copolymers in which the two comonomers copolymerize in a regular alternating sequence along the polymer chain. Of particular interest in our group are the stilbene-maleic anhydride/maleimide alternating copolymers. These copolymers possess sterically congested backbones and precisely placed functional groups arising from the strictly alternating copolymerization. The research in this dissertation is focused on the synthesis, characterization, and potential application of functionalized copolymers that contain semi-rigid alternating copolymer sequences. The fluorescence properties of a series of non-conjugated, tert-butyl carboxylate functionalized alternating copolymers were investigated. Extraordinarily high fluorescent intensity with excellent linearity was observed for the di-tert-butyl group-containing stilbene and maleic anhydride alternating copolymer in THF. We attributed the origin of the strong fluorescence to the “through space” π – π interactions between the phenyl rings from the stilbene and C=O groups from the anhydride. The fluorescence was maintained when the copolymer was deprotected and hydrolyzed and the resulting carboxylic acid-functionalized copolymer was dissolved in water at neutral pH. The tert-butyl carboxylate functionalized alternating copolymer sequences were incorporated into highly crosslinked polymer networks using suspension polymerization. After removing the tert-butyl groups by acidic hydrolysis, the surface area of the networks increased significantly. Using this facile two-step strategy, we were able to achieve nanoporous polymers with BET surface area up to 817 m2/g and carboxylic acid-functionalized surfaces. The BET surface area of deprotected polymers increased with increasing crosslinking density, and the stilbene-containing polymers showed systematically higher BET surface area than the styrene-containing polymers due to the stiffness of the alternating sequences. The resulting nanoporous polymers have potential to be employed as solid sorbents for CO2. The same tert-butyl carboxylate functionalized alternating copolymer sequences were also incorporated into microgels via miniemulsion polymerization. The miniemulsion technique ensured the successful synthesis of microgels with ~100 nm diameter using solid stilbene and maleimide monomers. The resulting tert-butyl carboxylate-containing microgels were converted into carboxylic acid-containing aqueous microgels by acid hydrolysis. These aqueous microgels showed good and reversible lead and copper ion adsorption capacities. Amine-functionalized nanoporous polymers were synthesized by the post-modification of highly-crosslinked divinylbenzene-maleic anhydride polymers. High amine-contents were achieved by covalently attaching multiamines to the acid-chloride functionalized polymer surface. The resulting polymers showed medium to high BET surface areas (up to 500 m2/g) and high CO2 capture capacities. / PHD

Poly-γ-glutamic acid (γ-PGA) is a biopolymer made up of repeating units of L-glutamic acid, D-glutamic acid or both. γ-PGA is water soluble, non-toxic and biodegradable, and can be used safely in a variety of applications that are increasing rapidly. This study investigated the production of HMW γ-PGA by five Bacillus species (B. licheniformis 1525, B. licheniformis NCTC 6816, B. licheniformis ATCC 9945a, B. licheniformis ATCC 9945a and B. subtilis (natto) ATCC 15245) in GS, C and E media for the removal of heavy metals in wastewaters. The highest γ-PGA yields of 11.69 g/l and 11.59 g/l were produced by Bacillus subtilis (natto) ATCC 15245 in GS medium and medium C respectively. Upon characterization, γ- PGAs with different properties (crystallinity, acid/salt form and molecular weights ranging from 2.56 × 105 Da to 1.65 × 106 Da) were produced. The water soluble, non-toxic, HMW (Mw 1.65 × 106 Da) γ-PGA produced by B. subtilis (natto) ATCC 15245 in medium C was investigated as a sorbent for the removal of heavy metal ions including Cu2+, Zn2+, Ni2+, Cd2+ and Ag+. The results showed that the removal of metals by γ-PGA was more dependent on the concentration of γ-PGA than the solution pH. The highest metal ions removal of 93.50%, 88.13%, 90.21%, 90.56% and 86.34% by HMW γ-PGA were obtained for Cu2+, Zn2+, Ni2+, Cd2+ and Ag+ respectively. The presence of interfering metal ions could hinder the adsorption of individual metal ions by γ-PGA. The affinities of heavy metal ions for γ-PGA followed the order: Cu2+ > Zn2+ > Ni2+ > Cd2+. The effect of molecular weight of γ-PGA on metal removal was also investigated, and it was found that metal ion adsorption capacity of γ-PGA strongly depended on its molecular weight. The maximum amount (93.50%) of Cu2+ sorbed by HMW γ-PGA was higher compared to that (59.48%) sorbed by LMW γ-PGA. Isotherm models showed that the Redlich-Peterson best described the metal adsorption capacity of γ-PGA. It was also found that a multisite adsorption mechanism occurred via the complexation of metal ions with the free α-carboxyl and possibly the amide functional groups in γ-PGA.

xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Altering and controlling the properties of solid surfaces in aqueous or other liquid phase environments has been a sought after objective for decades. With the discovery of chemisorbed self-assembled monolayers, this dream has become a reality. Oxide and metal surfaces can now be readily coated with an array of commercially available products to produce a desired fnctionality. The presence of these coatings on solid surfaces affects properties of the interfacial region by altering interfacial electrostatic fields, changing the structure of interfacial water molecules and altering the interactions of adsorbed species. This dissertation reports on in situ studies of adsorption at several solid/aqueous interfaces using vibrational sum-frequency spectroscopy, a surface specific technique. These studies are augmented by the use of atomic force microscopy and contact angle goniometry to characterize the prepared surfaces and their interactions with adsorbates. The studies investigate how changes in the surface structure and chemistry, as well as the bulk aqueous phase, affect interfacial structure. The studies within are primarily focused on the interactions of water with bare and functionalized fused silica and the relationship between the aqueous phase composition and the structure of fluorocarbon and hydrocarbon self-assembled monolayers. The variations in aqueous structure are then examined in detail using ionic strength controlled experiments to understand the direct interactions of water hydrophobically coated silica. This analysis is followed by an investigation of the competitive adsorption of methanol and water at fluorocarbon and hydrocarbon monolayers which show spectroscopic signatures of the interaction strength between fluorocarbons and hydrocarbons. Further studies are performed using butylammonium chloride to verify these spectroscopic signatures and reveal different molecular structures of adsorbed species at chemically different hydrophobic surfaces. Lastly, specific ion effects on the CaF 2 /water interface are shown using equilibrium and time-resolved sum-frequency spectroscopy. The results of all these studies have implications for an array of surface chemical applications from mineral flotation to biocompatibility. This dissertation includes previously published co-authored material. / Committee in charge: Thomas Dyke, Chairperson, Chemistry; Geraldine Richmond, Advisor, Chemistry; James Hutchison, Member, Chemistry; Mark Lonergan, Member, Chemistry; Qusheng Jin, Outside Member, Geological Sciences

Made available in DSpace on 2014-07-29T15:12:43Z (GMT). No. of bitstreams: 1 dissertacao rafael gomes da silveira 2010.pdf: 606651 bytes, checksum: c482224a3bb2815edeb926f5afa40486 (MD5) Previous issue date: 2010-11-29 / Neste trabalho, sílica gel com área superficial especifica (S BET ) de 407 m 2.g-1 foi modi cada com a mol ecula de 3-cloropropiltrimetoxissiliano (CPTMS), seguida da reação de funcionalização com os ligantes N-benzoiltioureia (BT) e N-benzoil- N' -amino-N"-(2-piridil)-guanidina (BG) via rota heterogênea, obtendo os materiais Si- BT e Si-BG, respectivamente. Os ligantes e os materiais funcionalizados foram caracterizados por ponto de fusão, espectroscopia de infravermelho, análises elementares de cloreto e de nitrogênio, medidas de porosidade e termogravimetria. A anáalise de nitrogênio indicou a presença de 2,14.10 ??4 e 8,30.10-6 mols de BT e BG por grama de materiais - Si-BT e -Si-BG, respectivamente. As medidas de área superficial, volume de poros e de diâmetro médio dos poros dos materiais, mostraram uma diminuição de sua área superficial em relação ao material de partida. Os espectros de infravermelho apresentaram bandas características dos ligantes N-benzoiltiouréeia, N-benzoil-N'-amino- N" -(2-piridil)-guanidina, bem como dos grupos cloropropil e dos grupos BT e BG covalentemente ligados na sílica. As superfícies funcionalizadas adsorveram íons Cu(II) e Co(II), em soluções aquosas e etanólicas num sistema de batelada, a 25 C. Os dados cinéticos mostraram que o tempo necessário para que o sistema atinja o equilíbrio foi de aproximadamente 60 minutos em ambos os casos. As isotermas de adsorção dos íons metálicos em equilíbrio com - Si-BT e -Si-BG mostraram que os sistemas estão de acordo com o modelo proposto por Langmuir, onde a capacidade máaxima de adsorção N f .g-1 (mol.g-1) (experimental e teórico) mostra que o Cu(II) tem a nidade ligeiramente maior que o Co(II), tanto em solução aquosa quanto em etanólica, para ambas as superfícies funcionalizadas. palavras chave: sílica, funcionalização, N-benzoiltiour eia, N-benzoil-N'-amino-N"-(2-piridil)-guanidina, adsorção de íons.