Acid/Base characterizations of metal oxide surfaces are often used to explain their catalytic behavior. However, the vast majority of these studies have been performed on powders or supported oxides, and there is very little information available in the literature on the interaction of acid/base probe molecules with well-defined oxide surfaces of known coordination geometry and oxidation state. The well-defined, single crystal surfaces of Cu₂O (111), SnO₂ (110), and Cr₂O₃ (101̲2) were investigated for their acid/base properties by the interactions between the probe molecules and the well-defined surface features. The adsorption of NH₃ at cation sites was used to characterize the Lewis acidity of SnO₂ (110) and Cu₂O (111) surfaces. The adsorption of CO₂, a standard acidic probe molecule, was used to characterize the Lewis basicity of the oxygen anions on SnO₂ (110), Cu₂O (111) , and Cr₂O₃ (101̲2) surfaces. BF₃, while not a standard probe molecule, has been tested as a probe of the Lewis basicity of the oxygen anions on SnO₂ (110) and Cr₂O₃ (101̲2). By studying probe molecules on well-defined metal oxide surfaces with known coordination geometry and oxidation state, an overall evaluation of NH₃, CO₂, and BF₃ as probe molecules can be made using the surfaces studied. NH₃ probed differences in Lewis acidity of Sn cations on SnO₂ (110), which had differences in coordination environments and oxidation states. But, NH₃ adsorption failed to provide any direct information on differences in Lewis acidity of Cu cations in different local coordination geometries on Cu₂O (111). CO₂ is a poor probe of the Lewis basicity of oxygen anions on the metal oxide surfaces studied here. CO₂ does not strongly adsorb to either SnO₂ (110) or Cu₂O (111). On Cr₂O₃ (101̲2), CO₂ does interact with oxygen sites but in two different coordinations, which vary with surface condition, making a comparison of basicity difficult. In the cases studied here, CO₂ either does not adsorb, or it does not provide a clear set of results that can be related simply to Lewis basicity. BF₃ seems to be a much better probe of the Lewis basicity than CO₂ for the well-defined metal oxide surfaces studied here. On SnO₂ (110) and Cr₂O₃ (101̲2), the boron atom of BF₃ directly interacts with oxygen sites by accepting their electrons. BF₃ thermal desorption seems to provide a direct measure of the Lewis basicity of different surface oxygen species as long as they are thermally-stable in vacuum. / Ph. D.

Design and preparation of novel host/guest systems, such as pseudorotaxanes, semirotaxanes, rotaxanes and catenanes, with high association constants, enhanced yields and the abilities to respond to external stimuli are of great importance and significance due to their topological novelty and potential application. The convergence of supramolecular chemistry with polymer science provides an important way to extend the scope of polymer and material sciences by incorporating designed host/guest systems into polymers, and the resulting non-covalently linked supramolecular polymers are expected to have unusual properties due to their unique architectures compared with traditional polymers. After discovery of bis(meta-phenylene)-32-crown-10 (BMP32C10) derivative/paraquat complexes, for about a quarter century only “taco”-shaped complexes were observed by X-ray crystallography. Here, by the self-assembly of a BMP32C10 bearing two electron-donating groups (carbazoles) with electron-accepting paraquat derivatives, the first [2]pseudorotaxane and the first pseudocryptand-type poly[2]pseudorotaxane based on BMP32C10 were isolated as crystalline solids as shown by X-ray analyses. The first dual component pseudocryptand-type [2]pseudorotaxanes were designed and prepared via the self-assembly of synthetically easily accessible BMP32C10 pyridyl, quinolyl and naphthyridyl derivatives with paraquat. The formation of the pseudocryptand structures in the complexes remarkably improved the association constants by forming the third pseudo-bridge via H-bonding with the guest and π-stacking of the heterocyclic units. A pseudocryptand-type [2]pseudorotaxane was formed via the self-assembly of a dipyridyl BMP32C10 derivative and a paraquat derivative. Due to the basicity of the pyridyl group, which forms the third pseudo-bridge of the pseudocryptand, this pseudorotaxane represents the first system with acid-base adjustable association constants, i. e., finite both under acidic and neutral conditions. The first pseudocryptand-type supramolecular [3]pseudorotaxane was designed and prepared via the self-assembly of a bispicolinate BMP32C10 derivative and a bisparaquat. The complexation behavior was cooperative. In addition, the complex comprised of the BMP32C10 derivative and a cyclic bisparaquat demonstrated strong binding; interestingly, a poly[2]pseudocatenane structure was formed in the solid state for the first time. Two novel BMP32C10 cryptands, bearing covalent and metal complex linkages, were designed and prepared. By employing the self-assembly of these biscryptands, which can be viewed as AA monomers, and a bisparaquat, which can be viewed as a BB monomer, the first AA/BB-type linear supramolecular polymers with relatively high molecular weights were successfully prepared. Via the self-assembly of two BMP32C10-based cryptands, bearing covalent and metal complex (ferrocene) linkages, with dimethyl paraquat, novel [3]pseudorotaxanes were formed statistically and anticooperatively, respectively. From a hydroxyl-functionalized secondary ammonium salt a [2]semirotaxane and a [2]rotaxane were prepared successfully with dibenzo-24-crown-8 (DB24C8). X-ray analysis of a single crystal of the [2]semirotaxane confirmed its semirotaxane nature. In addition, the formation of the [2]semirotaxane can be reversibly controlled by adding KPF6 and 18C6 sequentially. This system affords a way to prepare novel supramolecular polymers. Dibenzo-30-crown-10 (DB30C10) derivatives and pyridine-based DB30C10 cryptands were prepared by employing the templating method established by our group. A [2]pseudorotaxane was prepared based on DB30C10 diol and paraquat diol. The [3]pseudorotaxane formed via the self-assembly between DB30C10 cryptand and bisparaquat diol occurred in a cooperative manner. In addition, a bromo-functionalized DB30C10 cryptand was successfully designed and prepared. An alkyne-functionalized DB30C10 cryptand was designed and is under preparation; its precursors have been prepared successfully. In the future, based on these functionalized cryptands and paraquat salts, AA and AB type monomers will be prepared. Via the self-assembly between these monomers, non-covalent supramolecular polymers with high molecular weight will be afforded. A novel DB30C10 cryptand bearing an organometallic bridge, ferrocene, was prepared via 1-(3'-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) coupling of the crown ether diol with ferrocene dicarboxylic acid. The cryptand is dimerized in the solid state via π, π-stacking and hydrogen bonds. The ferrocene-based cryptand formed novel [2]pseudorotaxanes with paraquat and diquat PF₆ salts with association constants (Kₐ) of 1.7 ± 0.1 x 10³ and 4.2 ± 0.3 x 10⁴ M⁻¹ in acetone-d₆, respectively. In order to prepare linear polycatenanes, the preparation of which represent a real synthetic challenge, a series phenanthroline derivatives were designed and prepared. A “U” shaped monomer was successfully prepared in relative high yield with good solubility. In the future, real linear polycatenanes will be prepared. In addition, a novel diphenanthroline-based BMP32C10 derivative was prepared in high yield and the complexation behavior between it and dimethyl paraquat was studied. / Ph. D.

Les réactions de transfert de proton se retrouvent abondamment dans la nature et sont des processus cruciaux dans plusieurs réactions chimiques et biologiques, qui se produisent souvent en milieu aqueux. Les mécanismes régissant ces échanges de protons sont complexes et encore mal compris, suscitant un intérêt des chercheurs en vue d’une meilleure compréhension fondamentale du processus de transfert. Le présent manuscrit présente une étude mécanistique portant sur une réaction de transfert de proton entre un acide (phénol fonctionnalisé) et une base (ion carboxylate) en phase aqueuse. Les résultats obtenus sont basés sur un grand nombre de simulations de dynamique moléculaire ab-initio réalisées pour des systèmes de type « donneur-pont-accepteur », où le pont se trouve à être une unique molécule d’eau, permettant ainsi l’élaboration d’un modèle cinétique détaillé pour le système étudié. La voie de transfert principalement observée est un processus ultra-rapide (moins d’une picoseconde) passant par la formation d’une structure de type « Eigen » (H9O4+) pour la molécule d’eau pontante, menant directement à la formation des produits. Une seconde structure de la molécule d’eau pontante est également observée, soit une configuration de type « Zündel » (H5O2+) impliquant l’accepteur de proton (l’ion carboxylate) qui semble agir comme un cul-de-sac pour la réaction de transfert de proton. / Proton transfer reactions are found abundantly in nature and are critical processes in several chemical and biological reactions, which often occur in aqueous medium. The mechanisms governing these proton exchanges are complex and poorly understood, sparking interest of researchers for a better fundamental understanding of the transfer process. This manuscript presents a mechanistic study for a proton transfer reaction between an acid (functionalized phenol) and a base (carboxylate ion) in aqueous phase. The results are based on a large number of Ab-initio molecular dynamics simulations performed for a “donor-bridge-acceptor” type of system, where the bridge is a single molecule of water, allowing the development of a detailed kinetic model for this system. The transfer channel mainly observed is an ultra-fast one (less than a picosecond), through the formation of a Eigen-like (H9O4+) structure for the bridging water molecule, leading directly to the formation of the products. A second structure of the bridging water molecule is also observed, which is a Zündel-like (H5O2+) configuration involving the proton acceptor (carboxylate ion), which seems to act as a dead-end for the proton transfer reaction.

A despeito dos avanços instrumentais, as titulações continuam sendo largamente aplicadas em laboratórios de química analítica. Seu amplo uso está relacionado com a boa exatidão em aplicações bem estabelecidas e freqüente indicação como método de referência (p. ex., farmacopéias), equipamentos simples, comuns e de custo reduzido, consumo moderado de tempo e de reagentes. Entre as técnicas de titulação, destacam-se as potenciométricas (TP), empregadas universalmente para a quantificação de um ou mais componentes ácidos ou básicos em soluções aquosas ou não aquosas, possibilitando ainda determinar as constantes de dissociação de ácidos e de protonação de bases. Na análise de dados de TP são, via de regra, empregados os métodos clássicos (derivadas), porém, para sistemas compreendendo componentes multiprotonáveis, as inflexões das curvas de titulação deixam ser nítidas, especialmente em baixas concentrações. Nestas condições desfavoráveis, ainda assim podem-se obter resultados satisfatórios recorrendo a métodos de linearização das curvas ou analisando os dados por regressão não linear (RNL), facilmente implementáveis em computadores, hoje disseminados nos laboratórios. Outra técnica clássica para acompanhamento de titulações é a condutimétrica (TC), menos utilizada que a TP nos dias atuais, salvo para ácidos ou bases muito fracas, servindo para prover dados complementares em estudos de formação de complexos ou na caracterização de amostras ambientais. Tipicamente os pontos estequiométricos coincidem com a intersecção de segmentos de reta. Para amostras muito diluídas, com sistemas multipróticos ou com elevada concentração de eletrólitos em relação às espécies tituladas, a interpretação gráfica fica dificultada e a precisão decai. Pesquisas recentes mostraram que é possível aproveitar informações obtidas por TP para alimentar modelos de regressão não linear de TC e, assim, obter informações mais completas das amostras estudadas. No presente trabalho, avançou-se nesta linha criando programas computacionais para a análise simultânea de dados obtidos por TC e TP, empregando o método de RNL e minimizando os desvios (ou o quadrado dos desvios) dos dois conjuntos completos de dados para prover caracterização mais completa das amostras e melhoria na precisão dos resultados. Um programa de simulação de dados de TC e TP das mais diversas combinações e concentrações de sistemas ácido-base, com recursos para acrescentar erros aleatórios às variáveis simuladas, foi também desenvolvido. Permitiu verificar a validade e potencialidade do método da TPC-RNL e aperfeiçoar o programa de análise simultânea de dados. O programa de TPC-RNL foi aplicado inicialmente à re-avaliação de dados de titulações de água de chuva anteriormente coletadas e analisadas por outro colaborador do grupo. Como exemplo de aplicação original a amostras reais difíceis tanto para a TC como a TP isoladamente, determinou-se, por TPC, baixas concentrações de ácidos orgânicos de baixo peso molecular em amostras obtidas do produto de oxidação acelerada do biodiesel. Os resultados se mostraram compatíveis com os obtidos por outro pesquisador que recorreu à eletroforese capilar, sendo que o pH, a condutividade e a força iônica das amostras também foi reproduzida pelo programa Peak Master alimentado com as concentrações ajustadas por RNL / Despite all the advances in instrumental techniques, titrations are still widely applied in analytical chemistry laboratories. Its widespread use is associated with good accuracy, well established applications, simple, readily available and low cost equipment, moderate consumption of time and reagents and frequent indication as a reference method (eg., Pharmacopoeias). Potentiometric titrations (PT) outstands among other techniques, being universally used for the quantification of one or more basic or acidic components in aqueous or non aqueous samples and enabling further determination of the dissociation constants of acids and bases. Data analysis of PT with the glass electrode is typically done by finding the inflections of the curves with help of simple derivatives. However, PT curves of systems with multiprotonable components, specially at very low concentrations, fail to show sharp inflections. Under such unfavorable conditions, satisfactory results can still be obtained by using curve linearization methods or nonlinear regression (NLR) methods, now at the reach of every laboratory computer. Another classic technique for following titrations is conductivity (CT), less used routinely than PT nowadays except for very weak acids or bases, but still valuable as a complementary technique in equilibrium studies of complex formation or for the characterization of environmental samples. The stoichiometric points of simple CTs are found at the intersection of line segments. For very dilute samples or for multiprotic systems or with high concentrations of electrolytes compared to the species to be titrated, the graphical interpretation becomes difficult and the accuracy declines. Recent research has shown that it is possible to harness information obtained by PT to render non-linear regression models of CT solvable, thus extracting more complete information of the samples. This dissertation is devoted to the development and evaluation of software for the simultaneous analysis of data from CT and PT gathered together in the laboratory or by simulation, using the method of NLR with minimization of the weighted deviations (or their squares) of the two full data sets to provide more complete characterization of the samples and to improve the precision of the results. A simulation program for generating CT and PT curves for freely combined acid-base systems over a wide concentration range, with features to add random errors to the simulated variables was also developed. The simulator was used to evaluate the validity and potentiality of the PCTNLR method and improve the software of simultaneous data analysis. The program of PCT-NLR was applied firstly to the re-evaluation of data from titrations of rainwater collected and analyzed previously by another contributor to the group. As an original application example to real samples that are difficult for CT or PT separately, low concentrations of organic acids of low molecular weight were determined by PCT-NLR in samples from accelerated biodiesel oxidation tests. The results were consistent with those obtained by another researcher who used the capillary electrophoresis. The pH, ionic strength and conductivity of the samples were also reproduced by the program Peak Master using concentrations adjusted by NLR

A obstrução uretral é uma condição clínica comum em gatos, caracterizada por alterações metabólicas e do equilíbrio hidroeletrolítico e ácido-básico que são potencialmente fatais. Dentre as causas de obstrução uretral, a cistite idiopática é a mais frequentemente observada em diversos estudos. Outras causas incluem urolitíase, tampões uretrais e infecção do trato urinário. Em muitos casos, os gatos encontram-se em estado crítico e a morte pode ocorrer em decorrência de alterações metabólicas, como estado urêmico avançado e hipercalemia. As principais alterações eletrolíticas e do equilíbrio ácido-básico relatadas são hipercalemia, acidose metabólica, hiponatremia e hipocalcemia ionizada. Embora a obstrução uretral seja muito frequente na rotina clínica, estudos para caracterizar a população de gatos acometida ainda são escassos no Brasil. Características relacionadas ao manejo, dieta e perfil dos tutores podem influenciar na manifestação da doença. Os objetivos do presente estudo foram avaliar os parâmetros clínicos e as alterações hematológicas, bioquímicas, urinárias, eletrolíticas e ácido-básicas presentes em gatos com obstrução uretral e a associação entre estas variáveis. Além disso, objetivou-se conhecer as principais causas de obstrução uretral nos gatos atendidos no Hospital de Clínicas Veterinárias da Universidade Federal do Rio Grande do Sul. Para isso, foram incluídos no estudo 28 gatos com diagnóstico de obstrução uretral no período de dezembro de 2015 a dezembro de 2016. Foram obtidos dados referentes ao histórico, exame físico, coletados sangue e urina, além da realização de exames de imagem (radiografia e ultrassonografia abdominal). Em todos os gatos foram realizados hemograma, bioquímica sérica, análise de pH, gases e eletrólitos sanguíneos, urinálise e urocultura. Após, todos os pacientes foram tratados de acordo com um protocolo pré-estabelecido. A causa mais comum de obstrução uretral neste estudo foi a cistite idiopática, que ocorreu em mais de 60% dos casos, seguida de tampões uretrais e infecção do trato urinário. Nenhum caso de urolitíase foi diagnosticado, o que pode ser explicado por fatores como idade, ambiente e estilo de vida dos animais. A maioria dos gatos obstruídos apresentou múltiplos sinais sistêmicos, assim como alterações metabólicas, eletrolíticas e do equilíbrio ácido-básico, principalmente azotemia, hiperlactatemia, acidose metabólica, hipercalemia e hipocalcemia ionizada. Hipotermia, depressão do estado mental, bradicardia e desidratação foram os parâmetros clínicos que tiveram maior quantidade de associação com as alterações metabólicas e podem ser considerados bons preditores clínicos destas desordens. Por outro lado, o lactato não foi considerado um bom preditor de alterações clínicas e laboratoriais neste estudo. / Urethral obstruction is a common and potentially life-threatening condition, characterized by severe metabolic, electrolyte and acid-base disturbances. Among the causes of urethral obstruction, idiopathic cystitis is the most frequent in several studies. Other causes include urolithiasis, urethral plugs and urinary tract infection. In many cases, cats are critically ill and death may occur due to metabolic alterations, such as advanced uremic status and hyperkalemia. The main electrolyte and acid-base balance disorders reported are hyperkalemia, metabolic acidosis, hyponatremia and ionized hypocalcemia. Although urethral obstruction is a very common condition, there are few studies characterizing the population affected by the disease in Brazil. Characteristics related to management, diet and owner’s profile can influence the manifestation of the disease. The aim of the present study was to evaluate the association of clinical, haematological, biochemical, urinary, hydroelectrolyte and acid-base parameters in male cats with urethral obstruction. In addition, the objective was to determine the causes of urethral obstruction in male cats admitted to the Veterinary Teaching Hospital of Federal University of Rio Grande do Sul. Twenty-eight cats diagnosed with urethral obstruction were included in the study between December 2015 and December 2016. Data regarding medical history and physical examination were obtained. Blood and urine were collected, and imaging tests were performed (abdominal radiography and ultrasonography). Complete blood count, serum chemistry, blood pH, gas and electrolyte, urinalysis and urine culture were performed. All patients were treated accordingly to a previous established protocol. The most common cause of urethral obstruction in this study was idiopathic cystitis, which occurred in more than 60% of cases, followed by urethral plugs and urinary tract infection. No diagnosis of urolithiasis was achieved which could be explained by factors like age, environment and life style of cats. Most of obstructed cats presented with multiple systemic clinical signs, as well as, metabolic, electrolyte and acid-base alterations. The main disorders found were azotemia, hyperlactatemia, metabolic acidosis, hyperkalemia and ionized hypocalcemia. Hypothermia, depressed mental status, bradycardia and dehydration were the clinical parameters with the greatest amount of associations with the metabolic alterations and can be considered as good predictors of metabolic disorders. On the other hand, lactate was not considered a good predictor of clinical and laboratory abnormalities in this study.

Les molécules d’intérêt biologique ont pour caractéristique principale de participer aux processus biologiques, que ce soit au sein d’un organisme du monde du vivant, ou bien dans l’espace (exobiologie). Dans ces deux cas, l’eau joue un rôle prépondérant sur les propriétés des systèmes considérés. Les simulations numériques constituant désormais un élément incontournable pour l’interprétation des expériences, l’objectif de cette thèse sera de tenter de reproduire par des méthodes de chimie quantique les spectres IR expérimentaux relatifs à deux systèmes hydratés : les aérosols de nitrate, présents dans l’atmosphère, ainsi que les bases d’acides nucléiques microhydratées. Ce travail présente une même démarche afin d’obtenir la meilleure adéquation possible entre théorie et expérience. Tout d’abord, le modèle géométrique permettant de représenter au mieux nos systèmes a été recherché à partir de l’utilisation du code GSAM développé au laboratoire. Puis, nous nous sommes attachés à déterminer la méthode théorique la plus adaptée à l’étude de chacun des systèmes. Pour ce faire, différentes méthodes de calcul de structure électronique (dont B3LYP et ses analogues prenant en compte les interactions à moyenne et longue portée B3LYP-D et CAMB3LYP), de traitement vibrationnel (VPT2, VCI-P ou bien DM) ont été testées. L’évolution expérimentale observée pour les nombres d’onde associés aux cinq modes de vibration de l’ion nitrate en fonction du nombre de molécules d’eau au sein de l’aérosol est ainsi reproductible en utilisant un modèle d’agrégats d’agrégats du type (NaNO3,nH2O)3 au niveau calculatoire B3LYP/6-311+G(d,p) à 15cm-1 près. En ce qui concerne les bases d’acides nucléiques (X=C, T, U, A et G) microhydratées, la meilleure représentation d’un environnement aqueux est constitué d’un modèle explicite du type X,nH2O avec n=1 à 5 -déterminé à partir de l’application du code GSAM-, associé à un modèle implicite tel que PCM. La comparaison des nombres d’onde dans la zone de signature vibrationnelle 1000-1800cm-1 pour chaque base et à deux niveaux calculatoires différents B3LYP et B3LYP-D a conduit globalement à favoriser la première. En revanche, les méthodes de traitement vibrationnel dépendantes et indépendantes du temps donnent des résultats voisins dans cette zone, avec un coût calculatoire moins important pour la méthode VPT2. / Molecules with biological interest participate to biological processes in living organisms or in space (exobiology). Water plays a predominant part on properties of considered systems.Since computations take an important part in interpretation of experiments, the aim of this phD will be to try to reproduct IR experimental spectra with methods of quantum chemistry for two different hydrated systems : nitrate aerosols and microhydrated nucleic acid bases. This work presents a same approach to obtain the best agreement between experience and theory. First, the geometrical model for representation of hydration was investigated with the GSAM code developed at the laboratory. Then, the most adapted theoretical method was determined for studies of each system. Different methods of determination of electronic structure, especially B3LYP and their analogs considering medium and long range interactions B3LYP-D and CAMB3LYP, and vibrational treatments (VPT2, VCI-P and MD) were tested. The experimental evolution observed for wavenumbers associated to the five vibrational modes of the nitrate ion depending on the number of water molecules within the aerosol is reproducible using a model of aggregates of molecular clusters labeled (NaNO3,nH2O)3 at the B3LYP/6-311+G(d,p) level of theory : the average discrepancy between theory and experience reaches 15cm-1. Concerning microhydrated nucleic acid bases (X=C, T, U, A et G), the best representation of aqueous environment is made of an explicit model labeled X,nH2O with n=1 to 5 -determined from the application of the GSAM code-, with an implicit one like the PCM model. The comparison of wavenumbers calculated at the B3LYP and B3LYP-D levels of theory in the 1000-1800cm-1 spectral region which represents the vibrational signature for each base favoured the first method. But time-dependent and time-independent methods of vibrational treatment provide comparable results in this region, with a computational cost less important for the VPT2 approach.

This thesis examines sulfide oxidation in 4 physically and mineralogically diverse acid sulfate soil (ASS) materials collected from coastal floodplain sites in north-eastern New South Wales. The aim of this study is to gain further understanding of the process of sulfide oxidation in ASS materials, which will allow improved and more effective management strategies to be applied to these materials. The process of sulfide oxidation was examined using laboratory incubation experiments. The oxidation of pyrite was the primary cause of initial acidification of the ASS materials studied. Although the acid volatile sulfur fraction increased in concentration by an order of magnitude over the initial 8 days of incubation, the subsequent oxidation of this fraction did not result in substantial acidification. Sulfate (SO42-) was the dominant sulfur species produced from sulfide oxidation, however, water-soluble SO42- was a poor indicator of the extent of sulfide oxidation. The sulfoxyanion intermediates thiosulfate (S2O32-) and tetrathionate(S4O62-) were only detected in the early stages of incubation, and their relative abundance appeared to be pH dependent. The diminishing presence of these 2 sulfur species as oxidation progressed was indicative that ferric iron (Fe3+) and bacterial catalysis were driving the oxidation processes. The rate of sulfide oxidation, and consequent rate of acidification, was highly dependent on the soil pH and oxygen availability. Accelerated sulfide oxidation was only observed at low pH (i.e. pH < 4.0) when oxygen availability was not limited. The application of sub-optimal amounts of neutralising agents prevented severe soil acidification in the short-term (i.e. up to 2 months), but had little effect on decreasing the rate of sulfide oxidation and acidification in the long-term. Sub-optimal amounts of CaCO3 accelerated sulfide oxidation and acidification of the peaty marcasitic ASS material resulting in elevated soluble Fe and Al concentrations. For some of the ASS materials, sub-optimal applications of seawater-neutralised bauxite refinery residue (SNBRR) also resulted in elevated soluble Al concentrations. The response of partially-oxidised ASS materials to the exclusion of oxygen was variable. The rate of sulfide oxidation, acidification and the production of soluble oxidation products generally decreased markedly when subjected to anoxia. However, especially in highly acidic ASS materials (i.e. pH < 3.5), sulfide oxidation and acidification generally occurred (albeit at much slower rates), most probably due to oxidation by Fe3+. Rapid sulfide re-formation occurred in the peat ASS material that had been oxidised for 63 days, with 0.47% reduced inorganic sulfur (SCR) formed over 60 days of anoxia. Biogeochemical sulfide formation consumes acidity, however, sulfide re-formation was ineffective in reversing acidification under the conditions of this experiment. The peroxide oxidation methods examined were method dependent and substantially underestimated peroxide oxidisable sulfur, sulfidic acidity and net acidity. The precipitation of jarosite during peroxide oxidation was a major factor contributing to the underestimation in these ASS materials. Clay mineral dissolution may contribute towards the underestimation of both sulfidic and net acidity using peroxide oxidation methods. The atmospheric loss of sulfur and acidity was also identified as a possible additional interference. This study has shown that the initial pH of an ASS material is a useful indicator (additional to those already used) of the potential environmental hazard of an ASS material when oxygen is expected to be non-limiting, such as when ASS materials are excavated and stockpiled. The recommended action criteria need to be reassessed as the data indicate that the current criteria are conservative for alkaline and neutral ASS materials, but should be lowered for all acidic ASS materials (i.e. pH < 5.5) to 0.03% sulfide regardless of texture. Alternative strategies are necessary for the management of ASS materials that are subject to oxidation when the addition of optimal rates of neutralising materials cannot be ensured. The treatment of sites containing actual ASS materials by management strategies that rely on oxygen exclusion need to be accompanied by strategies that include either acid neutralisation or containment in order to reduce acid export from the site. The peroxide oxidation methods examined were subject to substantial interferences, and consequently are unable to reliably provide accurate measurements of the reduced inorganic sulfur fraction, sulfidic acidity, and net acidity in ASS materials.

The chemistry of mineral surfaces is of great importance in many different areas including natural processes occurring in oceans, rivers, lakes and soils. Manganese (hydr)oxides are one important group to these natural processes, and the thermodynamically most stable trivalent manganese (hydr)oxide, manganit (γ-MnOOH), is studied in this thesis. This thesis summarises six papers in which the surface chemistry of synthetic manganite has been investigated with respect to surface acid-base properties, dissolution, and adsorption of Cd(II) and the herbicide N-(phosphonomethyl)glycine (glyphosate, PMG). In these papers, a wide range of analysis techniques were used, including X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), potentiometry, electrophoretic mobility measurements and wet chemical techniques, in order to obtain a more complete understanding of the different processes occurring at the manganite-water interface. From the combined use of these techniques, a 1-pKa acid-base model was established that is valid at pH&gt;6. The model includes a Na+ interaction with the surface: =MnOH2+½ --&gt; =MnOH-½ + H+ log β0 (intr.) = -8.20 = -pHiep =MnOH2+½ + Na+ --&gt; =MnOHNa+½ + H+ log β0 (intr.) = -9.64 At pH&lt;6 the manganite crystals dissolve and disproportionate into pyrolusite (β-MnO2) and Mn(II)-ions in solution according to: 2 γ-MnOOH + 2H+ --&gt; β-MnO2 + Mn2+ + 2H2O log K0 = 7.61 ± 0.10 The adsorption and co-adsorption of Cd(II) and glyphosate at the manganite surface was studied at pH&gt;6. Cd(II) adsorption displays an adsorption edge at pH~8.5. Glyphosate adsorbs over the entire pH range, but the adsorption decreases with increasing pH. When the two substances are co-adsorbed, the adsorption of Cd(II) is increased at low pH but decreased at high pH. The adsorption of glyphosate is increased in the entire pH range in the presence of Cd(II). From XPS, FTIR and EXAFS it was found that glyphosate and Cd(II) form inner sphere complexes. The binary Cd(II)-surface complex is bonded by edge sharing of Mn and Cd octahedra on the (010) plane of manganite. Glyphosate forms inner-sphere complexes through an interaction between the phosphonate group and the manganite surface. The largest fraction of this binary glyphosate complex is protonated throughout the pH range. A ternary surface complex is also present, and its structure is explained as type B ternary surface complex (surface-glyphosate-Cd(II)). The chelating rings between the Cd(II) and glyphosate, found in aqueous complexes, are maintained at the surface, and the ternary complex is bound to the surface through the phosphonate group of the ligand.

TDO utilizes b-type heme as a cofactor to activate dioxygen and insert two oxygen atoms into free L-tryptophan. We revealed two unidentified enzymatic activities of ferric TDO from Ralstonia metallidurans, which are peroxide driven oxygenation and catalase-like activity. The stoichiometric titration suggests that two moles of H2O2 were required for the production of one mole of N-formylkynurenine. We have also observed monooxygenated-L-tryptophan. Three enzyme-based intermediates were sequentially detected in the peroxide oxidation of ferric TDO in the absence of L-Trp including compound I-type and compound ES-type Fe-oxo species. The Fe(IV) intermediates had an unusually large quadrupole splitting parameter of 1.76(2) mm/s at pH 7.4. Density functional theory calculations suggest that it results from the hydrogen bonding to the oxo group. We have also demonstrated that the oxidized TDO was activated via a homolytic cleavage of the O-O bond of ferric hydroperoxide intermediate via a substrate dependent process to generate a ferrous TDO. We proposed a peroxide activation mechanism of the oxidized TDO. The TDO has a relatively high redox potential, the protonated state of the proximal histidine upon substrate binding as well as a common feature of the formation of ferric hydroxide species upon substrate or substrate analogues binding. Putting these together, we have proposed a substrate-based activation mechanism of the oxidized TDO. Our work also probed the role of histidine 72 as an acid-base catalyst in the active site. In H72S and H72N mutants, one water molecule plays a similar role as that of His72 in wild type TDO. MauG is a c-type di-heme enzyme which catalyze the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. Its natural substrate is a monohydroxylated tryptophan residue present in a 119-kDa precursor protein of methylamine dehydrogenase (MADH). We have trapped a novel bis-Fe(IV) intermediate from MauG, which is remarkably stable. A tryptophanyl radical intermediate of MADH has been trapped after the reaction of the substrate with the bis-Fe(IV) intermediate. Analysis by high-resolution size-exclusion chromatography shows that MauG can tightly bind to the biosynthetic precursor and form a stable complex, but the mature protein substrate does not.

The goal of this study was to characterize the binding sites on the surface of wheat roots, Triticum turgidum, involved in the adsorption of protons and metals, and quantify the thermodynamic constants needed for a surface complexation model to predict metal binding. The adsorption of protons, Cd(II), Cu(II), and Ni(II) to the root surface as a function of pH and ionic strength in single metal exposure scenarios was quantitatively described using potentiometric titrations, batch metal adsorption experiments, and the least squares fitting program FITEQL. Model predictions from single metal exposures were compared to measured metal adsorption concentrations when roots were exposed to binary and ternary combinations of the metals. Proton dissociation was a function of three discrete monoprotic acid sites on the root surface with log proton dissociation constants of -4.50, -6.23, and -7.37 respectively, upon which varied ionic strength had no effect. The total proton binding capacities for the three sites were 2.58 x 10-4, 1.29 x 10-4, and 2.58 x 10-4 M, respectively. Metal complexation was best described by a two-site model having conditional stability constant log values of 3.04 and 3.30 for Cd(II), 3.21 and 3.25 for Cu(II), and 2.83 and 2.84 for Ni(II) at ionic strength 0.01M. At ionic strength 0.1 M the conditional stability constants log values were 2.37 and 3.36 for Cd(II), 3.11 and 2.56 for Cu(II), and 2.18 and 3.00 for Ni(II). When roots were exposed to binary or ternary mixtures of the metals, the two monoprotic acid single metal model did not provide ideal fits to the data indicating that adsorption in a metal mixture scenario cannot be considered additive and is dependent on the combination of metals present in the exposure environment. The experimentally determined proton dissociation constants and metal stability constants could be used in commercial geochemical speciation programs such as Visual MINTEQ to predict metal adsorption to plants. / Natural Sciences and Engineering Research Council of Canada, The Mining Association of Canada, Ontario Power Generation, Environment Canada.