Introdução É importante o desenvolvimento de sistemas de controle de poluição do ar que sejam eficientes, além de aplicáveis à condição nacional e pra proteção da saúde humana, uma vez que os compostos do grupo BTEX são tóxicos. Objetivo - Avaliar o desempenho de sistema de tratamento biológico para vapores de BTEX e investigar as melhores condições de operação para os critérios de projeto adotados. Métodos. Trata-se de trabalho experimental com utilização de unidade piloto constituída de coluna de vidro (diâmetro interno de 80 mm e altura total de 1,2 m) tendo no seu interior um meio filtrante composto vegetal e anéis de Pall - que serviram de suporte para os microrganismos e onde se realizou a biodegradação. Foram monitorados parâmetros como temperatura, perda de carga, vazão, concentração dos gases na entrada e na saída, que constituíram a base para desenvolver intervenções e melhorar seu desempenho. A análise dos gases foi feita por fotoionização (PID) em aparelho portátil. Conclusões - Conclui-se que é viável o tratamento biológico para remoção do BTEX de efluentes gasosos, nas condições operacionais adotadas, com eficiência máxima de remoção em torno de 90 por cento . A máxima eficiência foi obtida para tempo de retenção de 2,4 min., carga superficial do gás de 11,9 m3/m2xh, carga mássica no leito de 67 g/m3xh e capacidade de eliminação de 4 g/m3xh. O uso de anéis de Pall misturados ao composto evitou que valores elevados de perda de carga. Foi relevante a participação da adsorção. A utilização de composto mostrou-se viável como alternativa para a biodegradação do BTEX, fortalecendo seu uso com essa prática ambiental / Introduction - It is important to develop control systems for air pollution that are efficient, applicable to the national condition and to the protection of human health, since the group BTEX compounds are toxic. Objective - To evaluate the performance of biological treatment system for BTEX vapors and investigate the best operating conditions for the design criteria adopted. Methods - This experimental work used a pilot plant consisting of a glass column (internal diameter 80 mm and height of 1.2 m) filled with a filter medium - compost and Pall rings - which supported microorganisms and where biodegradation was carried out. Parameters were monitored such as temperature, pressure drop, flow rate, gas concentration at the inlet and outlet, which formed the basis for developing interventions and improve their performance. The gas analysis was measured by photoionization (PID) in a portable device. Conclusions -. We conclude that it is feasible biological treatment for removal of BTEX emissions, operating in the adopted conditions, with maximum removal efficiency (ER) of around 90 per cent . The maximum efficiency was obtained for empty bed retention time (EBRT) of 2.4 min, surface loading (SL) of 11.9 m 3 /m 2 xh, concentration load (CL) g/m3xh 67 and elimination capacity (EC) of 4 g/m 3 xh. The use of Pall rings mixed with the compost prevented high levels of pressure drop. It is relevant the participation of adsorption process. The use of compost proved to be feasible as an alternative to the biodegradation of BTEX, strengthening its use in the environmental practice

Le procédé de captage du CO2 en post-combustion par absorption chimique est aujourd'hui la technologie la plus mature en vue d'une réduction des émissions de CO2 issues de procédés industriels. Les deux principales limitations de la technologie sont la pénalité énergétique engendrée par le procédé, et la formation de produits de dégradation potentiellement toxiques pour l'Homme et l'environnement. Dans le cadre de ce projet de thèse, trois solvants innovants ont été présélectionnés pour leurs bonnes propriétés thermodynamiques de captage : les mélanges 1-méthylpipérazine / pipérazine (1MPZ /PZ), diméthylaminoéthanol / pipérazine (DMEA/PZ) et méthyldiéthanolamine/monoéthanolamine (MDEA/MEA). Ces trois solvants ont été étudiés en termes de stabilité chimique dans des conditions représentatives des conditions industrielles du captage de CO2 en post-combustion sur un dispositif expérimental construit par EDF R&D Chatou. Des méthodes analytiques complémentaires impliquant les chromatographies liquide et gazeuse ont été développées dans l'objectif de suivre les teneurs en amines constituantes du solvant au cours du temps, et d'identifier et quantifier les potentiels produits de dégradation formés aussi bien dans la phase liquide du solvant que dans les fumées traitées émises. Au vu des résultats obtenus au cours de ce projet, le solvant MDEA/MEA semble offrir le meilleur compromis en termes de stabilité chimique et de besoins énergétiques requis pour le procédé. Ce solvant présente des taux de dégradation inférieurs aux mélanges 1MPZ/PZ et DMEA/PZ, et permettrait une réduction de l'énergie au rebouilleur de l'ordre de 10 % par rapport à la MEA 30 %, solvant modèle au procédé. / Post-combustion CO2 capture using amine solvents is nowadays the most promising technology to limit the CO2 emissions from already existing power plants. The two main limitations of the process are the high energy penalty and the irreversible degradation of amines involving the formation of degradation products potentially toxic for human and the environment. Within the scope of this project, three innovative solvents were selected for their good thermodynamic properties for CO2 capture: the blends 1-methylpiperazine / piperazine (1MPZ/PZ), dimethylaminoethanol / piperazine (DMEA/PZ) and methyldiethanolamine/monoethanolamine (MDEA/MEA). The three blends were degraded in conditions representative of industrial conditions for post-combustion CO2 capture on a lab scale pilot plant constructed by EDF R&D. Complementary analytical methods involving gas and liquid chromatography were developed in order to monitor the stability of the constituent amines, and to identify and quantify potential degradation products formed. These methods permitted the characterization of both the liquid phase of the solvent and the gaseous phase corresponding to the treated flue gas. Results obtained during this project showed that the blend MDEA/MEA would offer the best compromise in terms of chemical stability and energy needed for the process. This solvent presents degradation rates lower than the blends 1MPZ/PZ and DMEA/PZ and would enable a reduction of the reboiler heat duty in the range of 10% when compared to MEA 30% the benchmark solvent of the process.

Este trabajo ha sido realizado en el contexto de los proyectos PPQ2000-0240 y BQU2002-03357, financiados por el Ministerio de Educación y Ciencia, así como las estancias breves de investigación realizadas en el Institut Européen des Membranes (Montpellier, Francia) bajo la supervisión de la Dra. Anne Julbe y en el Departamento de Ingeniería Química de la Universidad de Hiroshima (Japón) bajo la dirección del Prof. Masashi Asaeda.La pervaporación es la evaporación selectiva de un componente de una alimentación líquida al poner ésta en contacto con una membrana semi-permeable. Esta tesis propone la utilización de membranas cerámicas para mejorar la deshidratación de disolventes orgánicos mediante pervaporación. Con este propósito, este trabajo se divide en las etapas siguientes:1. Caracterización funcional de membranas cerámicas comerciales de PV, en ensayos de separación de una mezcla estándar agua/isopropanol. 2. Síntesis de membranas de sílice-zirconia, SiO2-ZrO2. Las membranas de SiO2-ZrO2 han sido preparadas mediante dos rutas del método sol-gel: (1) la ruta del gel polimérico y slip casting y (2) la ruta del sol coloidal y hot coating. Se ha caracterizado la morfología y estructura de estas membranas. La caracterización funcional en PV ha sido llevada a cabo en la separación de mezclas sintéticas de agua y disolvente orgánico.3. Desarrollo de aplicaciones industriales utilizando las membranas cerámicas, en especial, la valorización de una corriente cetónica residual procedente del proceso de fabricación de antioxidantes para el caucho, y la recuperación de tetrahidrofurano y acetona de efluentes industriales contaminados con agua. En el primer caso, se estudió el comportamiento de dos membranas des sílice comerciales y en el segundo caso, el funcionamiento de una membrana comercial de zeolita NaA. 4. Modelado matemático del flujo de agua a través de membranas cerámicas de PV, en función de la temperatura y de la actividad de agua en la alimentación.5. Validación de este modelado con los datos de PV obtenidos para las membranas comerciales y las membranas de desarrollo propio de SiO2-ZrO2, con precisión aceptable. / This work has been performed within the projects PPQ2000-0240 and BQU2002-03357, financed by the Spanish Ministry of Science and Education, as well as the short research stays performed at the Institut Européen des Membranes (Montpellier, France) under the supervision of Dr. Anne Julbe and at the Chemical Engineering Department of the Hiroshima University (Japan) under the direction of Prof. Masashi Asaeda. Pervaporation is the selective evaporation of one component of a liquid mixture by a membrane, which is in direct contact with the liquid phase. This work proposes the use of ceramic membranes to improve the pervaporative dehydration of organic solvents. With this purpose, the work has been developed into several stages:1. Functional characterisation of PV commercial ceramic membranes. 2. Synthesis of silica-zirconia, SiO2-ZrO2, membranes, as the literature points out to a higher stability of mixed oxide membranes at high water contents and temperatures. SiO2-ZrO2 membranes were prepared by two routes of the sol-gel method: (1) polymeric gel route and slip casting and (2) colloidal sol route and hot coating, The morphology and structure of these membranes were characterised by static procedures (FE-SEM, N2 adsorption-desorption, FTIR, XRD). The functional characterisation in PV of these membranes was performed.3. Development of PV ceramic membranes on industrial applications, mainly the valorisation of a residual ketonic stream coming from the production process of rubber antioxidants, and the recovery of THF and acetone from industrial effluents contaminated with water. In the case of the ketonic mixture, the performance of the commercial PV silica membranes was analysed at different working temperatures. 4. Mathematical modelling of water flux across PV ceramic membranes, as a function of the temperature and water activity in the feed.5. Validation of this model to the PV data obtained for the commercial silica membranes and also for the SiO2-ZrO2 non-commercial membranes, with acceptable accuracy. This work contributes to achieve a deeper insight on the structure-performance relationship of PV ceramic hydrophilic membranes, in order to improve their qualities towards implementation into actual industrial processes where these membranes can solve significant problems within economic and environmental contexts.

Gas-expanded liquids (GXLs) are novel and environmentally benign solvent systems with applications in reactions, separations, nanotechnology, drug delivery, and microelectronics. GXLs are liquid mixtures consisting of an organic solvent combined with a benign gas, such as CO2, in the nearcritical regime. In this work, molecular dynamics simulations have been combined with experimental techniques to elucidate the cybotactic region or local environment in gas-expanded liquids. Molecular dynamics simulations show clustering of methanol molecules in carbon dioxide-methanol mixtures. This clustering was not observed in carbon dioxide-acetone mixtures. Furthermore, addition of carbon dioxide enhances diffusivity of solutes in gas-expanded media as shown by both simulations and Taylor-Aris dispersion experiments. Finally, local structure and local compositions around pyrene in carbon dioxide-methanol and carbon-dioxide acetone were investigated using simulations and UV-vis spectroscopy.

The first goal of this work focused on the development of an amine dehydrogenase (AmDH) from a leucine dehydrogenase using site-directed mutagenesis. We aimed at reductively aminating a prochiral ketone to a chiral amine by using leucine dehydrogenase (LeuDH) as a starting template. This initial work was divided into two stages. The first focused mutagenesis to a specific residue (K68) that we know is key to developing the target functionality. Subsequently, mutagenesis focused on residues known to be in close proximity to a key region of the substrate (M65 and K68). This approach allowed for reduced library size while at the same time increased chances of generating alternate substrate specificity. An NAD+-dependent high throughput assay was optimized and will be discussed. The best variants showed specific activity in mU/mg range towards deaminating the target substrate. The second goal of this work was the development of a thermostable glucose dehydrogenase (GDH) starting with the wild-type gene from Bacillus subtilis. GDH is able to carry out the regeneration of both NADH and NADPH cofactors using glucose as a substrate. We applied the structure-guided consensus method to identify 24 mutations that were introduced using overlap extension. 11 of the tested variants had increased thermal stability, and when combined a GDH variant with a half-life ~3.5 days at 65℃ was generated--a ~10⁶increase in stability when compared to the wild-type. The final goal of this work was the characterization of GDH in homogeneous organic-aqueous solvent systems and salt solutions. Engineered GDH variants showed increased stability in all salts and organic solvents tested. Thermal stability had a positive correlation with organic solvent and salt stability. This allowed the demonstration that consensus-based methods can be used towards engineering enzyme stability in uncommon media. This is of significant value since protein deactivation in salts and organic solvents is not well understood, making a priori design of protein stability in these environments difficult.

Interconnection layers fabricated during back end of line processing in semiconductor manufacturing involve dry etching of a low-k material and deposition of copper and metal barriers to create copper/dielectric stacks. After plasma etching steps used to form the trenches and vias in the dielectric, post etch residues (PER) that consist of organic polymer, metal oxides and fluorides, form on top of copper and low-k dielectric sidewalls. Currently, most semiconductor companies use semi aqueous fluoride (SAF) based formulations containing organic solvent(s) for PER removal. Unfortunately, these formulations adversely impact the environmental health and safety (EHS) requirements of the semiconductor industry. Environmentally friendly "green" formulations, free of organic solvents, are preferred as alternatives to remove PER. In this work, a novel low temperature molten salt system, referred as deep eutectic solvent (DES) has been explored as a back end of line cleaning (BEOL) formulation. Specifically, the DES system comprised of two benign chemicals, malonic acid (MA) and choline chloride (CC), is a liquid at room temperature. In certain cases, the formulation was modified by the addition of glacial acetic acid (HAc). Using these formulations, selective removal of three types of PER generated by timed CF₄/O₂ etching of DUV PR films on Cu was achieved. Type I PER was mostly organic in character (fluorocarbon polymer type) and had a measured thickness of 160 nm. Type II PER was much thinner (25 nm) and consisted of a mixture of organic and inorganic compounds (copper fluorides). Further etching generated 17 nm thick Type III PER composed of copper fluorides and oxides. Experiments were also conducted on patterned structures. Cleaning was performed by immersing samples in a temperature controlled (30 or 40° C) double jacketed vessel for a time between 1 and 5 minutes. Effectiveness of cleaning was characterized using SEM, XPS and single frequency impedance measurements. Type II and III residues, which contained copper compounds were removed in CC/MA DES within five minutes through dissolution and subsequent complexation of copper by malonic acid. Removal of Type I PER required the addition of glacial acetic acid to the DES formulation. Single frequency impedance measurement appears to be a good in situ method to follow the removal of the residues. High water solubility of the components of the system in conjunction with their environmental friendly nature, make the DES an attractive alternative to SAF.

This thesis focuses on my endeavors to prepare new porous polymeric monoliths that are viable to use as supports in flow-through processes. Polymer monoliths of various porous properties and different chemical properties have been prepared utilizing the thermally induced phase separation (TIPS) phenomenon and step-growth polymerization reactions. The aim has been to find appropriate synthesis routes to produce separation supports with fully controlled chemical, physical and surface properties. This thesis includes preparation of porous monolithic materials from several non-cross-linked commodity polymers and engineering plastics by dissolution/precipitation process (i.e. TIPS). Elevated temperatures, above the upper critical solution temperature (UCST), were used to dissolve the polymers in appropriate solvents that only dissolve the polymers above this critical temperature. After dissolution, the homogeneous and clear polymer-solvent solution is thermally quenched by cooling. A porous material, of three dimensional structure, is then obtained as the temperature crosses the UCST. More than 20 organic solvents were tested to find the most compatible one that can dissolve the polymer above the UCST and precipitate it back when the temperature is lowered. The effect of using a mixture of two solvents or additives (co-porogenic polymer or surfactant) in the polymer dissolution/precipitation process have been studied more in depth for poly(vinylidine difluoride) (PVDF) polymers of two different molecular weight grades. Monolithic materials showing different pore characteristics could be obtained by varying the composition of the PVDF-solvent mixture during the dissolute­ion/precipitation process. Step-growth polymerization (often called polycondensat­ion reaction) combined with sol-gel process with the aid of porogenic polymer and block copolymer surfactant have also been used as a new route of synthesis for production of porous melamine-formaldehyde (MF) monoliths. In general, the meso- and macro-porous support materials, for which the synthesis/preparation is discussed in this thesis, are useful to a wide variety of applications in separation science and heterogeneous reactions (catalysis).

Thesis (Ph.D. (Pharmaceutical Chemistry)--North-West University, Potchefstroom Campus, 2009.

Thesis (Ph.D. (Pharmaceutical Chemistry)--North-West University, Potchefstroom Campus, 2009.

Gas-expanded liquids (GXLs) are a unique class of tunable solvents with unlimited potential. A wide range of solvent properties and solvent interactions and complexes are possible by adjusting the amount of the gas component (in situ) or changing the organic liquid. Aside from solvent tunability, there are environmental and processing benefits to using GXLs. Organic solvent use is decreased, the gas component can be vented off facile separations, and the gas can act as an antisolvent for selective solute precipitation. As a result there are numerous reaction and extraction schemes and materials processing applications that could benefit from GXL use. Unfortunately, important molecular-level details that can drive a chemical process are largely unknown and limit GXL use in industrial and specialty applications. The work presented in this uses a synergistic study of experiments and computer simulations to explore solvation processes and molecular interactions in GXLs and the effects on macroscopic observables like spectroscopy, transport, and reactions. Steady-state solvation of a laser dye is studied with spectroscopy (UV/vis and fluorescence) and molecular dynamics simulations (MD). Both experiment and theory show that organic enrichment occurs in the vicinity of the solute called the cybotactic region. Subsequently, the solvent dynamics arising by electronically perturbing the solute are studied with MD simulation. Unexpected dynamics are observed and are dependent on the organic component and gas composition. The diffusion of heterocyclic compounds is studied with MD simulations and compared to the Taylor-Aris diffusion study of former group members. The experiments and simulations do not agree, but solvent structures obtained by simulation are shown to provide valuable insight into solvent-dependent absorption spectroscopy, or solvatochromism. Finally, dissociation constants of alkylcarbonic acids that form in situ in CO2/alcohol mixtures are presented from spectroscopic measurements. Spectroscopic techniques to measure dissociation constants are well known; however, the high-pressure and multiple equilibria associated with alkylcarbonic acids hinder straight-forward measurement and analysis.