Dissertations / Theses on the topic 'Solid liquid separation'

Livestock manure is a valuable resource for fertilizing and amendment, due to the high concentrations of plant nutrients. However, the increasing intensification of livestock farms combined to an improper manure management led to nutrient losses to air, water and soil. Among the manure treatment technologies that allow to reduce the environmental impact of livestock activities, solid-liquid separation is a widely applied technique that leads to a more appropriate nutrient application to fields and, thus, minimize nutrient losses and their related environmental problems. The evaluation of the different separating system and the optimization of this process is crucial in order to improve the performances of the treatment systems and the minimization of the environmental impact related to manure management. The present study aims to: (i) evaluate the solid-liquid separation treatment in a treatment plant under different operating conditions; (ii) investigate the optimization of the separation process through natural and synthetic chemicals. The performances of different solid liquid-separation techniques were evaluated under different operative conditions. In particular, the separation efficiency of two screw press separators were compared to the separation efficiency of a decanting centrifuge, in order to evaluate the separation system that allow a better biological removal nitrogen. Both the screw press and the decanting centrifuge treated digested slurry; moreover, the decanting centrifuge was run with the liquid fraction produced by the screw press and with the addition of flocculants. In all the trials, the decanting centrifuge presented a higher separation efficiency, producing a liquid fraction with a lower dry matter concentration and enabling a correct biological nitrogen removal. The effect of manure pre-treatments on solid liquid separation performances was also evaluated. In particular, the effect of manure acidification on three different separation techniques was studied. Pig slurry (pH = 7) and acidified pig slurry (pH = 5.5) were treated through (i) screw press, (ii) decanting centrifuge, (iii) flocculation combined to a belt thickener drainage. Acidified manure was easier to drain, leading to a lower retention of solid particles in the liquid fraction. This resulted in a decrease of the separation efficiency for all the analyzed parameters. Furthermore, The acidification caused the concentration in the solid fraction of particle related species to decrease, of dissolved monovalent species not to be affected, and of divalent cations to be increased. Chemical pre-treatments were investigated in order to improve the separation efficiency of mechanical separators for nutrient, especially nitrogen and phosphorus. In particular, the utilization of natural flocculants (such as chitosan) was compared to a synthetic flocculation treatment. A laboratory test was run treating the manure produced by pig livestock and anaerobic digestion plants were treated. In particular, 20 different manure samples were used: (i) 5 samples were collected from farrow-to-finish pigs livestock; (ii) 5 samples were collected from finishing pigs livestock; (iii) 10 samples were collected from co-digestion plants for energy production. The collected samples were flocculated through two different treatments: (i) a synthetic treatment (PAC+POLY), consisting in the addition of aluminum polychloride and a branched cationic polymer of medium molecular weight; (ii) a natural treatment (CHITOSAN). Different flocculant dosages were evaluated thrugh a jar test. The optimal dosage was assessed through: the floc size, the separation efficiencies of weight, total solids and total suspended solids. The optimal dosage of both the chitosan and the cationic polymer emulsions resulted highly dependent on the manure sample characteristics. Both the synthetic and the natural treatments allowed to improve the separation efficiencies, retaining a larger amount of solids and nutrients in the solid fractions. However, the chitosan addition lead to the formation of flocs more weak and with a non-well-defined structure compared to the synthetic treatment. For this reason, the separation efficiency of dry matter, volatile solids, nitrogen, phosphorus and potassium was lower for the chitosan optimal dosage compared to the synthetic treatment. Physico-chemical separation was also assessed through a pilot-scale experiment. The slurry was composed by the pig and cattle manure produced by 10 livestock farms and was treated by a pilot-scale flotating system working with the addition of aluminum polychloride and a branched cationic polymer of medium molecular weight. Optimal dosages were evaluated by a jar test. The pilot-scale separator allowed to separate the 67% of the total weight of the input slurry and the 88% of the total solids. The pilot-scale flotating system allowed separating a large amount of solid fraction, which can be more easily managed and treated through different processes. However, the input slurry presented a large amount of coarse particles, which led to the formation of bigger flocs that tended to settle instead of floating on the liquid surface. For this reason, the input slurry should be pre-treated in order to remove the lager particles from the liquid manure. Furthermore, linear polymers with a lower molecular weight could be more suitable for the flotating systems, since they lead to the formation of smaller aggregates that can float on the liquid surface more easily. Finally, the set-up of the pilot-scale flotator should be modified, in order to enhance the transportation of the solid particles to the liquid surface. In this way the solid-liquid separation of livestock slurries through flotation could be better evaluated. An empirical model was finally evaluated in order to predict solid-liquid separation efficiency and thus identify the more suitable separation technique according to farms’ needs. To define and validate the model, the necessary data were firstly collected through published papers. This bibliographical research allowed us to collect publications about solid liquid separation published from 2000 to 2010. Model definition and validation was carried out on each of the groups using the two methods: random and cross-validation. The use of additives, the animal species and the separation technique were identified to be the parameters that most affected the separation techniques. Therefore, the database was divided in 12 groups according to these parameters. The graphical analysis allowed us to distinguish several technological and operational conditions that affect separation efficiency. However, more parameters could be taken into account with more data. Furthermore, for 7 of the 14 subgroups it was possible to define and validate the predictive models. These present RRMSEs lower than 50% thus can be implemented in a decision support tool, enabling the identification of the most effective treatment option. For the remaining separation technologies and operative conditions, most of which include the use of flocculants, more available data are necessary to define and validate empirical predictive models. The results gathered through the experiments described in the previous sections allow us to better evaluate the different solid-liquid separation technologies and to define the most suitable systems for a manure treatment plant. In particular, the required characteristics of the resulting liquid and solid fractions may differ according to the whole treatment scheme and its primary scope. In this context, the available separation techniques present different separation efficiencies and, thus, lead to the production of liquid and solid fractions that have different concentrations of dry matter and nutrients. E.g. chemical-mechanical separation have a higher separation efficiency for dry matter and nutrients, compared to mechanical separators. Separation performances are also affected by operative conditions, such as manure type, pre-treatments and the flow rate of the input slurry. Manure characteristics are also affected by manure pre-treatments, which could modify physical, electrochemical and chemical properties of the input manure and, thus, influence the separation efficiency. Natural polymers allow to improve the separation efficiency for dry matter and nutrients. However, the optimization of physico-mechanical separation systems results higher with the utilization of synthetic additives, which lead to the formation of more structured aggregates; even though they could cause toxicity problems in soils or when the separated fractions are treated through biological processes (e.g. nitrification-denitrification or composting). Furthermore, the optimal dosage is highly dependent to the characteristics of the treated manure, therefore it is difficult to define guidelines that could give indication of the optimal dosage according to manure properties such as the dry matter content.During the combination of physical or mechanical separation with coagulation and/or flocculation pre-treatments, the selection of the optimal dosage and the more suitable type of chemical is strongly affected by manure characteristics. Therefore, the performances of a determined separation process may be negatively affected by the utilization of the wrong additive type. The identification of the more suitable separation process could be supported by a predictive model that could estimate the separation efficiency of a defined separator under different operative conditions. An empirical predictive model could give good indications for the separation systems more affected by the dry matter concentration of the input slurry (e.g. filtration or pressurized filtration), but the result less precise for other separation systems.

Mestrado em Biotecnologia - Industrial e Ambiental
Tipicamente, apenas um dos enantiómeros é responsável pelo efeito pretendido de um fármaco, sendo que o outro pode levar a respostas menos potentes ou até mesmo indesejadas. As entidades reguladoras praticam políticas restritas em relação à comercialização de fármacos como misturas racémicas. Assim, a indústria farmacêutica tem enfrentado desafios relacionados com o desenvolvimento de métodos para produção de fármacos oticamente puros. No entanto, e considerando a dificuldade acrescida na produção de enantiómeros puros por síntese direta, a síntese de misturas racémicas seguida da sua purificação surge como uma alternativa mais barata, simples e flexível. Os sistemas aquosos bifásicos (SABs) e os sistemas de duas fases sólida-líquida (SDFSL) são técnicas alternativas mais biocompatíveis que têm sido utilizados como técnicas de separação enantiosseletiva de fármacos e/ou aminoácidos com enantiosseletividades bastante promissoras. Para além disso, apresentam benefícios de custo, rapidez, simplicidade e versatilidade de operação e possibilidade de aumento de escala. Este trabalho foca-se no desenvolvimento de SABs e SDFSL constituídos por seletores quirais que possam atuar simultaneamente como solvente. Numa primeira abordagem o objetivo foi desenvolver novos SABs quirais, mais biocompatíveis, simples e eficientes. Para tal, SABs constituídos por açúcares, aminoácidos e líquidos iónicos quirais foram aplicados na resolução enantiomérica de ácido mandélico racémico. O sistema mais promissor, composto por [C1Qui][C1SO4] + K3PO4, obteve um excesso enantiomérico de -33.4%. Numa segunda abordagem, foi possível criar uma alternativa mais simples e mais eficiente recorrendo a SDFSL. Com estes sistemas, foi obtido o valor mais elevado de excesso enantiomérico deste trabalho, de 49.0%, através da precipitação enantiosseletiva do R-ácido mandélico por interação com [N4444][D-Phe].
Conventionally, only one of the enantiomers is responsible for the intended effect of a drug, whilst the other may lead to a less potent or even undesired response. Regulation entities are very strict regarding the commercialization of racemic drugs. Thus, pharmaceutical industry has been facing challenges related to the creation of methods to produce optically active drugs. However, considering the increased difficulty in the production of pure enantiomers by direct synthesis, the synthesis of racemic mixtures followed by their purification appears as a cheaper, simpler and more flexible alternative. Aqueous biphasic systems (ABS) and solid-liquid biphasic system (SLBS) are more biocompatible alternatives that have been used to separate racemic drugs and amino acids with promising enantioselectivities. Furthermore, these are cost-effective, quick, simple and operationally flexible. This work intended to develop ABS and SLBS using chiral selectors that can simultaneously act as solvents. In a first attempt, chiral ABS of better biocompatibility, simplicity and efficiency were developed. For that purpose, ABS constituted by sugars, amino acids and chiral ionic liquids (CILs) were applied for chiral resolution of racemic mandelic acid (MA). The most promising ABS was a system composed of [C1Qui][C1SO4] + K3PO4 which yielded the maximum enantiomeric excess of -33.4%. In a second approach, it was possible to create a simpler and more efficient technique resorting to SLBS. The enantiomeric excess value of 49.0% was achieved, by the enantioselective precipitation of the R-MA caused by interactions with [N4444][D-Phe].

Dairy manure treatment, using solid-liquid separation and microwave enhanced advanced oxidation process (MW/H₂O₂-AOP), was investigated. The objectives of the research were to determine: 1) the nutrient and metal composition of solid and liquid fractions of raw dairy manure following solid-liquid separation, 2) the effects of MW/H₂O₂-AOP operating factors of temperature, hydrogen peroxide (H₂O₂) dosage, acid concentration and heating time on sugar production and nutrient release from solid dairy manure. Solid-liquid separation of raw dairy manure, using a 1mm laboratory sieve, showed that solid fractions had a higher composition of TS and volatile solids (VS), while the liquid fractions were richer in nutrients and metals. Laboratory separation by screening alone was not effective in removing high amounts of nutrients and solids from the raw manure. Screening experiments were conducted using cellulose fibers to study the effects of temperature, acid concentration, H₂O₂ dosage and heating time on sugar production, with the aim of applying the results to dairy manure lignocellulosic material. Sugar production increased when acid concentration was increased from 1% to 3%, but decreased with an increase to 10%. More sugar was produced at 160°C compared to 120°C. Sugar production decreased with increasing time. Microwave irradiation of solid dairy manure at pH 2, temperatures of 80, 120 and 160°C, H₂O₂ dosages of 0 to 0.50 mL, and heating times of 10 to 20 min, showed that more sugars were released at higher temperatures. Temperature and hydrogen peroxide dosage were identified as the most important factors affecting solubilization of phosphorus and ammonia. Subsequently, a two-stage acid hydrolysis process, using MW/H₂O₂-AOP, was used to investigate sugar production and solubilization of phosphorus and ammonia from solid dairy manure at: 3% acid concentration, 120 and 160°C, 0 and 2 mL H₂O₂ and heating times of 20 and 60min. To enhance sugar production from solid dairy manure, the microwave should be operated at higher temperatures and shorter heating times with no H₂O₂. For ammonia and phosphorus solubilization, higher temperatures and longer heating times, in the presence of H₂O₂, would be advantageous. MW/H₂O₂-AOP is therefore an efficient means for treating diary manure for nutrient recovery.

La formation de gels de silice dans les procédés hydrométallurgiques est très souvent problématique pour la performance des étapes de séparation solide-liquide, en raison du colmatage des filtres. Ces étapes interviennent en aval des étapes de lixiviation visant à mettre en solution les éléments d'intérêts, notamment dans des milieux à forte acidité. Egalement mis en solution au cours de ces attaques acides, le silicium précipite alors sous forme d'oxyde de silicium et forme des gels extrêmement préjudiciables à la filtration. Dans le cadre d'une collaboration avec ERAMET Research, centre de recherche d'ERAMET, groupe minier français qui conçoit des procédés hydrométallurgiques, nous avons étudié l'influence des conditions de lixiviation d'un minerai spécifique sur la cinétique de dissolution du silicium ainsi que sur les mécanismes de précipitation de la silice en milieu acide. Nous avons montré qu'en-dessous d'une valeur de pH égale à 2, la silice polymérise pour former des gels suivant des mécanismes indépendants de la composition ionique de la solution. L'étude structurale des gels obtenus, réalisée par diffusion de rayonnement aux petits angles (SAXS) nous a conduit à proposer un modèle pour la mésostructure qui permet de comprendre leur impact sur les vitesses de filtration. Par la suite, des stratégies consistant à modifier la mésostructure des gels par des approches physiques ou physico-chimiques ont été considérées. Les résultats obtenus ont montré la possibilité d'utiliser à court terme ces stratégies pour améliorer la filtrabilité des gels de silice dans un procédé hydrométallurgique
The formation of silica gels in hydrometallurgical processes is very often problematic for the performance of the solid-liquid separation steps, due to clogging of the filters. These steps are carried out downstream of leaching aiming to solubilize the elements of interests, in particular in solutions with strong acidity. Also dissolved during acidic leaching, the silicon then precipitates in the form of silicon oxide and forms gels extremely detrimental to filtration. In collaboration with ERAMET Research, a research center of ERAMET, a french mining group that designs hydrometallurgical processes, we studied the influence of the leaching conditions of a specific ore on the dissolution kinetics of silicon as well as on the mechanisms of precipitation of silica in an acidic solution. We have shown that below a pH value of 2, silica polymerizes to form gels following mechanisms independent of the ionic composition of the solution. Based, on the structural study of the gels, carried out by small angle radiation scattering (SAXS) we proposed a model for the mesotructure, which explain the impact on filtration rates. Subsequently, strategies to modify the mesostructure of the gels by physical or physicochemical approaches were considered. The results have shown the potentialities of these strategies in the short term to improve the filterability of precipitated silica gels in a hydrométallurgical process

This thesis contains the results and discussion of an exploratory investigation into the application of Crossflow Microfiltration (CFMF) for solid/liquid separation in biological wastewater treatment systems. The principal objective of the study was to assess the influence of CFMF on the performance of identified biological wastewater treatment systems. It was not the objective to optimise filtration performance. A literature review indicated that the crossflow mode of filtration has been widely accepted as a unit operation in the fermentation industry. The filtration mode is now being applied not only for solid/liquid separation but also for separations on a molecular and ionic level. Very few applications of crossflow filtration in the context of biological wastewater treatment solid/liquid separation are reported in the literature. The reasons for this limited experience would appear to be the scale involved and the perceived high costs; separations in the fermentation industry are usually conducted at relatively small scale (laboratory or pilot-scale) and involve high-value products, justifying high capital and operating costs. Also, the high level of separation performance attained is perhaps not necessary for many wastewater treatment applications. No doubt these reservations are largely valid. However, these arguments cannot be applied equally to all filtration methods and wastewater treatment schemes. For example, the costs of microfiltration are substantially less than ultrafiltration or reverse osmosis, and in certain cases effluents with extremely low suspended solids contents may be required. In the light of these observations an investigation of CFMF for solid/liquid separation in biological wastewater treatment systems appears justified. Two biological treatment systems were selected for study: the Upflow Anaerobic Sludge Bed (UASB) reactor and the Activated Sludge system. The envisaged benefits accruing from the application of CFMF were different in each case.

Includes bibliographical references.
Wastewater treatment technologies have developed out of the need to protect receiving water bodies from the increasingly concentrated municipal and industrial waste streams generated through human activity. Of the methods available to clean wastewaters, biological nutrient removal (BNR) activated sludge (AS) is applied throughout South Africa and internationally as it has many advantages, notably it is cheaper to operate, does not introduce salinity into the water and is a simple and robust process. One of the key steps in the BNR AS process is the separation of biomass from the water. This is traditionally achieved by means of secondary settling tanks (SSTs), however recently the use of membranes for solid-liquid separation has gained popularity for the following reasons: Membranes are able to retain all solids and thus are insensitive to the settling characteristics of sludges, • they can be run at high concentrations and hence smaller reactor volumes are required, • membranes can produce a guaranteed high quality effluent free of pathogens and in some cases viruses too. • Additionally smaller reactor volumes and the obviation of SSTs allow a substantial wastewater treatment plant footprint reduction. Hence the combination of membranes in BNR AS is being increasingly applied. where much research has been conducted on the performance of membranes. The majority of the research has focused on the physical membrane performance, investigating the mechanisms of fouling, or on the membrane biological reactor (MBR) performance in removing organic compounds or nitrogen compounds from wastewater. There are however few case studies investigating BNR using membranes despite speculation that the inclusion of membranes may indeed affect the nature of the activated sludge biomass (Witzig et al., 2002).

The focus of this thesis is the study of turbulent solid-liquid stirred suspensions, which are involved in many common unit operations in the chemical, pharmaceutical and food industries. The studies of two-phase flows present a big challenge to researchers due to the complexity of experiments; hence there is a lack of quantitative solid and liquid hydrodynamic measurements. Therefore, an investigation of turbulence modulation by dispersed particles on the surrounding fluid in stirred vessels has been carried out, via two-phase fluorescent Particle Image Velocimetry (FPIV) and micromixing experiments. The main property of interest has been the local dissipation rate, as well as root-mean-square (rms) velocities and turbulent kinetic energy (TKE) of the fluid. Initially a single-phase PIV study was conducted to investigate the flow field generated by a sawtooth (EkatoMizer) impeller. The purpose of this study was to gain insight into various PIV techniques before moving on to more complex two-phase flows. Subsequently stereo-, highspeed and angle-resolved measurements were obtained. The EkatoMizer formed a good case study as information regarding its hydrodynamics is not readily available in literature, hence knowledge has been extended in this area. An analysis of the mean flow field elucidated the general structure of fluid drawn into the impeller region axially and discharged radially; the latter characterised the impeller stream. The radial rms velocity was considered to represent best the system turbulence, even though the tangential rms velocity was greater close to the blade; however the radial component was more prevalent in the discharge stream. Due to differences in rms velocities, TKE estimates obtained from two and three velocity components deviated, being greater in the latter case. Integral (1-D and 2-D) length scales were overestimated by the quantity W / 2 in the impeller region. Ratios of longitudinal-to-lateral length scales also indicated flow anisotropy (as they deviated from 2:1). The anisotropy tensor showed that the flow was anisotropic close to the blade, and returned to isotropy further away from the impeller. Instantaneous vector plots revealed vortices in the discharge stream, but these were not associated with flow periodicity. Alternatively, the vortex structures were interpreted as low frequency phenomena between 0-200 Hz; macro-instabilities were found to have a high probability of occurrence in the discharge stream. Dissipation is the turbulent property of most interest as it directly influences micromixing processes, and its calculation is also the most difficult to achieve. Its direct determination from definition requires highly resolved data. Alternative methods have been proposed in the literature, namely dimensional analysis, large eddy simulation (LES) analogy and deduction from the TKE balance. All methods were employed using 2-D and 3-D approximations from stereo-PIV data. The LES analogy was deemed to provide the best estimate, since it accounts for three-dimensionality of the flow and models turbulence at the smallest scales using a subgrid scale model. (Continues...).

Doutoramento em Engenharia Química
Os terpenos pertencem ao que é provavelmente a maior e mais diversificada classe de produtos naturais com aplicações em vários setores devido aos seus sabores e fragrâncias. O seu elevado número, variedade de estruturas e complexidade química, fazem deles uma classe de compostos onde há ainda muitos estudos a serem realizados e questões a serem respondidas tanto sobre as suas propriedades termofísicas e equilíbrio de fases como sobre o seu impacto nos processos de extração e purificação e no ambiente. Ambos são relevantes para o desenvolvimento de biorrefinarias, onde estes compostos podem desempenhar um papel importante dada a sua ubiquidade, valor económico e variedade de aplicações. Esta tese está relacionada com a extração de terpenos de fontes naturais e a sua posterior separação e purificação. Além do desenvolvimento de novos métodos experimentais para medir propriedades termodinâmicas e equilíbrios de fases, algumas abordagens teóricas foram também consideradas para o mesmo fim. Inicialmente, de forma a criar novas aplicações para estes compostos e tirando vantagem da sua baixa solubilidade em água, tal como demonstrado por novas e precisas determinações experimentais, os terpenos são utilizados para preparar solventes hidrofóbicos sustentáveis e de baixo custo, no âmbito dos solventes eutécticos profundos. Depois, com base nos coeficientes de atividade a diluição infinita e previsões do COSMO-RS, foi feita uma seleção de líquidos iónicos com potencial para o fracionamento de terpenos. Mais ainda, visando o desenvolvimento de novos processos de separação de terpenos, foram também formulados e caracterizados solventes eutécticos profundos compostos por sais de amónio e ácidos monocarboxílicos. Finalmente, e com o objetivo de desenvolver modelos precisos para o destino dos terpenos no ambiente, uma série de propriedades físico-químicas essenciais foi medida e modelada.
Terpenes belong to what is probably the largest and most diverse class of natural products with applications in several industries due to their flavor, and fragrance. Their high number, variety of structures and chemical complexity, make of them a class of compounds for which there are still many studies to be carried out and questions to be answered both concerning their thermophysical properties and phase equilibria and their impact in their extraction and purification processes and on their environmental impact. Both are relevant for the development of the biorefinery where these compounds may play an important role given their ubiquity, economic value and variety of applications. This thesis is related to terpenes extraction from natural sources and their subsequent separation and purification. Besides to the development of new experimental procedures for thermodynamic properties and equilibrium measurements, some theoretical approaches were also applied to this end. First, to create new applications for this compounds, and taking advantage of their very low solubility in water as shown by new and accurate experimental determinations, terpenes are used to prepare sustainable and cheap hydrophobic solvents within the deep eutectic solvents framework. After, based on the activity coefficients at infinite dilution measurements and COSMO-RS predictions a selection of ILs was made with potential for terpenes fractionation. Yet, and aiming at the development of new separation processes of terpenes, deep eutectic solvents composed of ammonium salts and monocarboxylic acids were also formulated and characterized. Finally, and targeting the development of accurate models for the fate of terpenes in the environment, a range of essential physicochemical properties of terpenes were measured and modelled.

La separation de particules solides immergees dans un liquide en ecoulement au travers d'un champ magnetique statique intense a ete etudiee. Des forces magnetiques, liees aux susceptibilites magnetiques et au gradient spatial de champ magnetique, ou bien des forces electromagnetiques, liees aux conductivites electriques et au mouvement relatif de l'element conducteur par rapport au champ magnetique, peuvent etre mises en oeuvre. La separation est effective lorsque ces forces agissent sur la trajectoire des particules perpendiculairement a la direction de l'ecoulement. Ce sont les forces precedemment citees agissant soit directement sur la particule, soit via le liquide par l'intermediaire de forces de pression. A partir de la distribution du champ magnetique delivre par un bobinage supraconducteur axisymetrique vertical, deux principes de separation sont proposes. Un exploite les zones de gradient de champ ou un ecoulement de liquide conducteur et/ou magnetique, de type cylindrique parallele a l'axe du bobinage permet d'obtenir des forces electromagnetiques et magnetiques. L'autre exploite la zone centrale de champ homogene ou un ecoulement de type conique convergent ou divergent, incline par rapport a l'axe du bobinage, permet d'obtenir des forces electromagnetiques. Les effets des forces electromagnetiques et magnetiques sur la deviation de particules sont demontres experimentalement grace a la conception et l'exploitation de dispositifs creant des ecoulements cylindrique ou conique dans les differentes zones de champ de bobinages supraconducteurs. Des solutions aqueuses a proprietes conductrices et/ou magnetiques chargees en particules de plexiglas sont testees. Une simulation numerique des aspects electromagnetiques induits dans le procede est developpee et validee a partir des ordres de grandeur deduits de l'approche theorique ou obtenus experimentalement.

Orientador: José Renato Zanini
Banca: Antônio Carlos Barreto
Banca: Tarlei Arriel Botrel
Banca: Luiz Carlos Pavani
Banca: Antônio Sergio Ferraudo
Resumo: Os hidrociclones são equipamentos amplamente utilizados pela indústria em processos envolvendo separação sólido-líquido, porém, ainda, pouco divulgados na agricultura irrigada brasileira. Buscou-se neste trabalho determinar a perda de carga e avaliar o desempenho de um hidrociclone de geometria "Rietema" como pré-filtro de partículas sólidas. Os testes foram realizados no Centro Federal de Educação Tecnológica de Uberaba - MG - Brasil utilizando um hidrociclone de geometria "Rietema". Este equipamento possui um diâmetro de 19,20 cm na parte cilíndrica e opera com vazões variando entre 10 m3 h-1 e 27 m3 h-1. Os materiais particulados usados em suspensão foram: solo franco-argiloso e areia de rio. Os resultados mostraram que a perda de carga máxima média foi de 52 kPa e 47 kPa para as suspensões aquosas de areia e solo, respectivamente. Seu melhor desempenho ocorreu operando com suspensão aquosa de areia, apresentando eficiência total de 92,31% para a vazão de 26,97 m3 h-1. Dentre as conclusões pode-se inferir que o equipamento avaliado é eficiente para remoção de partículas de areia, podendo ser utilizado como pré-filtro em sistemas de irrigação.
Abstract: The hydrocyclones are equipments widely used by industry in cases involving solid-liquid separation, but still, little reported in brazilian irrigated agriculture. The proposal of this research was to determining the head loss and evaluate the performance of a hydrocyclone of geometry "Rietema" as a pre-filter of solid particles. The tests were performed in the Centro Federal de Educação Tenológica de Uberaba - MG - Brazil using a hydrocyclone of Rietema geometry. This equipment has a diameter of 19.20 cm at the cylindrical part and operates with flows ranging between 10 m3 h-1 and 27 m3 h-1. The materials used in particulate suspension were: clay loam soil and sand from river. The results showed that the average maximum head loss was 52 kPa and 47 kPa of aqueous suspensions of sand and soil, respectively. Its best performance occurred operating with slurry of sand, presenting total efficiency of 92.31% for flow rate of 26.97 m3 h-1. Among the conclusions can be inferred that the equipment is judged effective at removing particles of sand and can be used as pre-filter in irrigation systems.
Doutor

Le secteur de la méthanisation à la ferme ou territoriale connait un fort développement, entrainant la production de grandes quantités de digestats. Si la fraction solide de ces digestats est généralement utilisée en tant qu’amendement organique, la fraction liquide peut être valorisée par la récupération des éléments minéraux bien que la présence de composés organiques pose des problèmes de traitement et d’élimination. Les objectifs de cette thèse sont i) de caractériser la fraction liquide des digestats et donner des premiers éléments pour leur futur traitement et ii) d’expliquer la variabilité des composés résiduels présents dans cette fraction liquide en relation avec l’origine des substrats, les paramètres du procédé de méthanisation et le type de séparation solide/liquide. Dans une première partie, nous avons caractérisé de manière détaillée onze digestats issus d’installations industrielles de co-digestion. Le fractionnement par neuf filtrations successives de la fraction liquide des digestats a permis de quantifier la contribution des matières en suspension, des colloïdes grossiers et fins et des matières dissoutes aux différents paramètres physico-chimiques et biologiques. Il a été montré la faible biodégradabilité aérobie des composés organiques dont la majeure partie se trouve dans la matière en suspension (> 1,2 µm). Pour élargir la base de données, nous avons caractérisé dix-huit digestats supplémentaires et un digestat de boues de station d’épuration dont les fractions liquides ont été fractionnées par deux filtrations successives (1,2 μm et 1 kDa). L’analyse en composantes principales, la classification hiérarchique et la matrice de corrélation réalisées sur l’ensemble des 30 digestats ont mis en avant l’impact majeur des techniques de séparation solide/liquide sur la composition de la fraction liquide des digestats. Dans le groupe des techniques de séparation hautement performantes, des sous-groupes ont permis de distinguer les digestats à base de boues d’épuration, ceux à base de lisiers porcins et ceux issus de procédés piston thermophiles. Dans le groupe des procédés de séparation à faible performance, les teneurs en DCO et matières sèches de la fraction liquide des digestats ont été corrélées aux teneurs en cultures énergétiques et fumiers bovins dans l’alimentation. Finalement, pour l’ensemble des digestats, le paramètre SUVA, lié à la teneur en matière aromatique et à la stabilisation des composés, a été corrélé au temps de séjour des digesteurs. Pour comprendre l’origine des composés résiduels observés dans la fraction liquide des digestats issus de la co-digestion avec de fortes proportions de fumier bovin, quatre réacteurs CSTR alimentés avec respectivement de la paille de blé, de la bouse de vache et du fumier ont été conduits pendant 48 semaines. Les performances de méthanisation ont mis en évidence le caractère âgé du fumier qui avait été partiellement dégradé pendant le stockage à la ferme. Ainsi la fraction liquide du digestat du fumier a présenté les plus fortes concentrations en composés organiques qui en outre présentaient une complexité, mesurée par fluorimétrie 3D, plus élevée que les autres substrats. La fraction liquide du digestat issue de la méthanisation de la paille a révélé les plus fortes proportions de DCO dans les fractions colloïdales et dissoutes. La faible biodégradabilité des composés organiques et leur forte proportion dans les matières en suspension suggèrent le développement de procédés physico-chimiques de séparation tels que la coagulation pour le traitement de la fraction liquide des digestats
Agricultural and centralized biogas plants are facing a fast development, leading to the production of huge amounts of digestates. Whereas the solid fraction of digestates is used as fertilizer, the liquid fraction can be valorized by the recovery of mineral materials, although the presence of organic compounds may be problematic for the treatment and disposal of this effluent. The objectives of this thesis are: i) to characterize the liquid fraction of digestates and to provide guidelines for its further treatment, ii) to explain the variability of residual compounds in the liquid fraction of digestates in relation with substrate origin, process parameters and the type of solid-liquid separation. In a first part, eleven digestates from full scale codigestion plants were thoroughly characterized. Their liquid fractions were fractionated by nine successive filtrations, which allowed quantifying the contribution of suspended particles, coarse and fine colloids and dissolved matter on several physico-chemical and biological parameters. Organic compounds were mainly found in suspended particles (> 1.2 µm) and presented low aerobic biodegradability. To enlarge the data base, eighteen more digestates from codigestion and one digestate from waste activated sludge were characterized; their liquid fractions were fractionated by two successive filtrations (1.2 μm and 1 kDa). Principal component analysis, hierarchical clustering analysis and correlation matrix carried out on the 30 digestates set, highlighted the major impact of the solid-liquid separation process on the composition of the liquid fraction of digestates. In the high performance separation process group, subgroups allowed separating digestates from sewage sludge, digestates from pig manure and digestates from plug-flow thermophilic processes. In the low performance separation process group, COD and total solids concentration in the liquid fraction of digestates were correlated to the percentage of energy crops and cow manure in the feed. Finally, SUVA parameter which accounts for aromatic compounds content and the stabilization of organic matter, was correlated to the retention time in digester for the whole digestates set. To understand the origin of residual compounds in the liquid fraction of digestates from co-digestion of high proportions of cattle manure, four CSTR reactors fed with wheat straw, cow dung and cow manure were operated for 48 weeks. Anaerobic digestion performances showed that cow manure had undergone some aerobic degradation during its storage at the farm. Therefore, the liquid fraction of manure digestate had the highest concentrations in organic compounds. In addition, these organic compounds had the highest complexity measured by 3D fluorimetry. The low biodegradability of organic compounds and their high percentage in suspended particles suggest the development of physico-chemical separation process such as coagulation for the treatment of the liquid fraction of digestates

Thesis (M. Eng.)(Chemical Engineering)--University of Pretoria, 2006.
Accompanied by a CD-ROM containing Matlab programs. Includes bibliographical references. Available on the Internet via the World Wide Web.

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Funep
Os hidrociclones são equipamentos amplamente utilizados pela indústria em processos envolvendo separação sólido-líquido, porém, ainda, pouco divulgados na agricultura irrigada brasileira. Buscou-se neste trabalho determinar a perda de carga e avaliar o desempenho de um hidrociclone de geometria “Rietema” como pré-filtro de partículas sólidas. Os testes foram realizados no Centro Federal de Educação Tecnológica de Uberaba - MG - Brasil utilizando um hidrociclone de geometria “Rietema”. Este equipamento possui um diâmetro de 19,20 cm na parte cilíndrica e opera com vazões variando entre 10 m3 h-1 e 27 m3 h-1. Os materiais particulados usados em suspensão foram: solo franco-argiloso e areia de rio. Os resultados mostraram que a perda de carga máxima média foi de 52 kPa e 47 kPa para as suspensões aquosas de areia e solo, respectivamente. Seu melhor desempenho ocorreu operando com suspensão aquosa de areia, apresentando eficiência total de 92,31% para a vazão de 26,97 m3 h-1. Dentre as conclusões pode-se inferir que o equipamento avaliado é eficiente para remoção de partículas de areia, podendo ser utilizado como pré-filtro em sistemas de irrigação.
The hydrocyclones are equipments widely used by industry in cases involving solid-liquid separation, but still, little reported in brazilian irrigated agriculture. The proposal of this research was to determining the head loss and evaluate the performance of a hydrocyclone of geometry “Rietema” as a pre-filter of solid particles. The tests were performed in the Centro Federal de Educação Tenológica de Uberaba - MG - Brazil using a hydrocyclone of Rietema geometry. This equipment has a diameter of 19.20 cm at the cylindrical part and operates with flows ranging between 10 m3 h-1 and 27 m3 h-1. The materials used in particulate suspension were: clay loam soil and sand from river. The results showed that the average maximum head loss was 52 kPa and 47 kPa of aqueous suspensions of sand and soil, respectively. Its best performance occurred operating with slurry of sand, presenting total efficiency of 92.31% for flow rate of 26.97 m3 h-1. Among the conclusions can be inferred that the equipment is judged effective at removing particles of sand and can be used as pre-filter in irrigation systems.

Orientador: Eugenio Spano Rosa
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O presente trabalho investiga os mecanismos de separação sólido-líquido em separadores tubo-ciclônicos. O trabalho é desenvolvido a partir de testes experimentais e simulação numérica. A etapa experimental investiga a influência do aumento de viscosidade sobre a eficiência do separador. Através de uma análise dimensional, os dados experimentais são reduzidos em grupos adimensionais. Obtem-se uma correlação entre a eficiência de separação e os grupos adimensionais. Ela revela como a eficiência depende dos parâmetros geométricos e operacionais do separador. A correlação obtida possibilita dimensionar estes separadores para cenários com elevada viscosidade. As simulações numéricas são realizadas utilizando um método de volumes finitos. O processo de separação é estudado através do adimensional Stokes. São introduzidos os conceitos de superfície de captura e tempo de residência de partículas. Define -se um importante parâmetro do escoamento, o comprimento de decaimento. Propõe-se um modelo unidimensional para o separador. Realiza-se com base neste modelo uma análise comparativa entre dois separadores. Os resultados são coerentes com dados experimentais e indicam quais características geométricas melhoram a eficiência do separador
Abstract: This work investigates the solid-liquid separation mechanisms in swirl tubes through experimental and numerical analysis. In the experimental phase, it is analyzed the impact of the viscosity increase on the separation efficiency of swirl tubes. The experimental data are reduced using dimensional analysis. A functional relationship between the separation efficiency and the dimensionless groups is obtained, allowing to calculate the separation efficiency dependency on the liquid viscosity, flow rate, particle size, and other geometrical parameters of the separator. This relationship helps to design these desander devices to scenarios with high viscosity. Numerical simulations are carried out in a structured grid using a finite volume method. Separation process is studied through the Stokes number. The concepts of capture surface and residence time of particles are introduced and an important flow field parameter, the length of decay is defined. A one-dimensional model is proposed for the swirl tube. A comparative analysis between two separators is done based on the one-dimensional model. The results are in agreement with experimental data and indicate which geometrical features help to improve the separator efficiency
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica

Magnetic photocatalysts were synthesised by coating a magnetic core with a layer of photoactive titanium dioxide. This magnetic photocatalyst is for use in slurry-type reactors in which the catalyst can be easily recovered by the application of an external magnetic field. The first attempt at producing this magnetic photocatalyst involved the direct deposition of titanium dioxide onto the surface of magnetic iron oxide particles. The photoactivity of these Fe3O4/TiO2 was lower than that of single-phase TiO2 and was found to decrease with an increase in the heat treatment. These observations were explained in terms of an unfavourable heterojunction between the titanium dioxide and the iron oxide core. Fe ion diffusion from the iron oxide core into the titanium dioxide matrix upon heat treatment, leading to a highly doped TiO2 lattice, was also contributing to the observed low activities of these samples. These Fe3O4/TiO2 particles were found to be unstable, with photodissolution of the iron oxide phase being encountered. This photodissolution was dependent on the heat treatment applied, the greater the extent of the heat treatment, the lower the incidence of photodissolution. This was explained in terms of the stability of the iron oxide phases present, as well as the lower photoactivity of the titanium dioxide matrix. In fact, the observed photodissolution was found to be induced-photodissolution. That is, the photogenerated electrons in the titanium dioxide phase were being injected into the lower lying conduction band of the iron oxide core, leading to its reduction and then dissolution. Thus, the approach of directly depositing TiO2 onto the surface of a magnetic iron oxide core proved ineffective in producing a stable magnetic photocatalyst. The introduction of an intermediate passive SiO2 layer between the titanium dioxide phase and the iron oxide phase inhibited the direct electrical contact and hence prevented the photodissolution of the iron oxide phase. Improvements in the photoactivity were seen to be due to the inhibition of both the electronic and chemical interactions between the iron oxide and titanium dioxide phases. Preliminary optimisation experiments revealed that a thin SiO2 layer is sufficient for inhibiting the photodissolution. The thickness of the TiO2 coating was found not to have a significant effect on the photocatalytic performance of the coated particles. Finally, heat treating for 20 minutes at 450??C was sufficient for converting the titanium dioxide into a photoactive phase, longer heating times had no beneficial effect on the photoactivity.

Mestrado em Engenharia do Ambiente - Gestão Ambiental - Instituto Superior de Agronomia
The increasing of population along with the decrease of agricultural area led to the intensification of agriculture and livestock production in order to continue to respond to the current food requirements. Consequently there has been an increase of animal waste that might be a source of environmental pollution. This study has as main objective to evaluate strategies for land application of slurry in relation to its environmental impact and the agronomic value of slurry. The following treatments were considered: acidification, solid-liquid separation and the impact of slurry incorporation shortly after its surface application. An assay in pots has been performed during which emissions of ammonia (NH3) and greenhouse gases (GHG) were monitored and also the concentration of nutrients in the soil solution. At the end of the assay, the production of fodder oats was evaluated as well as the export of nutrients associated. It has been concluded that the best combination of treatments is the surface application of acidified slurry without incorporation. As the method currently recommended is the injection of slurry, that has several limitations, it may be relevant to review the legislation concerning land application of livestock effluents, if future assays to full scale validate our results.

O processo de espessamento e clarificação dos efluentes das usinas de beneficiamento de carvão mineral com a adoção de sedimentadores é uma prática consagrada ao longo de todo o mundo uma vez que é necessário o reaproveitamento da água utilizada tanto por questões econômicas como ambientais. O primeiro sedimentador, tipo espessador, a entrar em operação industrial na região carbonífera de Santa Catarina foi instalado na Mina Barro Branco da Carbonífera Rio Deserto em 2007. O equipamento era dotado de lamelas de PVC e foi instalado como alternativa às bacias de decantação, que apresentam alto custo de construção e operação. Contudo, o equipamento se mostrou ineficaz devido a deposição de sólidos nas lamelas. Essa dificuldade levou a adoção de outros modelos de sedimentadores de fluxo vertical que não utilizam lamelas. Esse trabalho apresenta os dados disponíveis da operação do equipamento com as lamelas na Mina Barro Branco e resultados atuais da operação dos sedimentadores da Mina Esperança sem lamelas. Nesse segundo caso foi medida a vazão, concentração de sólidos e dos metais ferro, alumínio e manganês, nos fluxos de entrada e saída. No efluente clarificado mediu-se ainda o pH e a turbidez. Registraram-se dados de uma operação satisfatória, com impacto importante na redução dos custos no transporte e deposição dos rejeitos finos e no tratamento do overflow clarificado possibilitando o descarte de acordo com a Legislação Ambiental.
The process of thickening and clarifying the effluents of mineral coal processing plants with the use of settlers is a well-established practice throughout the world since it is necessary to reuse the water used for both economic and environmental reasons. The first settler, a thickener type, to enter into industrial operation in the Santa Catarina coal region was installed at the Barro Branco Mine of the Carbonifera Rio Deserto in 2007. The equipment was equipped with PVC lamellae and was installed as an alternative to the decantation basins, which have a high cost of construction and operation. However, the equipment proved to be ineffective due to deposition of solids in the lamellae. This difficulty led to the adoption of other models of vertical flow settlers that do not use lamellae. This work presents the available data of the operation of the equipment with lamellae in the Mina Barro Branco and current results of the operation of the settlers in the Mina Esperança without lamellae. In this second case the flow, concentration of solids and iron, aluminum and manganese metals in the inflow and outflow were measured. In the clarified effluent the pH and turbidity were also measured. Data were recorded for a satisfactory operation, with a significant impact on the reduction of costs in the transportation and deposition of the fine tailings and in the treatment of the clarified overflow, allowing the disposal according to the Environmental Legislation.

O minério de ferro produzido no complexo de Carajás traz consigo características mineralógicas que conferem um elevadíssimo teor de Fe em todas as suas frações granulométricas. Dessa forma, ao final da cadeia produtiva, tanto os produtos comerciais mais grosseiros quanto os finos contem cerca de 62% de Fe contido na sua composição. Importante destacar que em Carajás as fases no processamento desse minério são apenas para cominuição e classificação por tamanho. Não existem etapas de concentração e os produtos são diferenciados por suas respectivas curvas granulométricas: o “granulado” - mais grosseiro (> 13 mm), o “Sinter-Feed” (< 13 mm e > 0,5 mm) e o “pellet feed” (< 0,15 mm). Garantir a correta distribuição granulométrica da matéria prima é uma premissa de mercado. A ultima etapa da classificação é feita através de hidrociclones e gera um overflow ultrafino de altíssima superfície específica maior que 6.500 Blaine e com 45% até 95 % < 7 μm. E ainda possui um elevado teor de Fe - cerca de 62 %. Dessa forma os objetivos gerais dessa pesquisa buscaram a solução para essa oportunidade de recuperar e vender esses rejeitos. O estudo sugeriu através de ensaios com tecnologias capazes de desaguar os ultrafinos gerados para 9,00 % de umidade, que é o valor que permite a movimentação e o manuseio desses rejeitos, além de permitir sua incorporação na blendagem de produtos mais grossos. Desse modo, foram realizados experimentos em diversos laboratórios externos e em escala piloto na Usina de Carajás com amostras dos dois rejeitos ultrafinos das duas fases de hidrociclonagem: o natural e o moído. Ficou evidente que o equipamento tem de combinar necessariamente e de forma eficiente dois fatores essências ao desaguamento: elevadíssimas pressões e altas temperatura na operação desses ultrafinos. A produtividade atingida foi da ordem de 50 t/h x m² para o rejeito da hidrociclonagem do Sinter Feed e 40 t/h x m² para o rejeito dos hidrociclones da Moagem.
The Iron ore that is produced in Carajás mining complex brings mineralogical characteristics that give a very high Fe content in all its size fractions. Thus, at the end of the production chain both coarser and fine contains about 62% Fe contained in its composition. Importantly, in Carajás stages in the processing of this ore are for reduction and classification by size. There is thus no concentration steps and products are differentiated by their respective size distribution curves: the "grain" - coarser (> 13 mm), the "Sinter-Feed" (<13 mm and > 0.5 mm) and the "pellet feed" (<0.15 mm). Ensure proper particle size distribution of the raw material is a market premise. The last step of classification is made using hydrocyclones and generates an overflow ultrafine high specific surface area greater than 6.500 Blaine and with 45% to 95% <7 μm. And has a high Fe content - about 62%. The overall objectives of this research sought the solution to this opportunity to recover and sell these “tailings”. The study suggested by testing with technologies capable of flowing into the ultrathin generated to 9.00% of moisture, which is the value that allows movement and handling these wastes, and allows their incorporation into the blending of thicker products. Thus, experiments were carried out in several external laboratories and pilot-scale plant in the Carajás with samples of both ultrafine “tailings” of the two phases of hydrocycloning: the natural and the ground. It was evident that the equipment must necessarily match and two efficiently factors essences to dewatering: very high pressure and high temperature operation of these “tailings”. The productivity achieved was around 50 t/h x m² in reject of the Sinter Feed hydrocycloning and 40 t/h x m² to reject of the grinding hydrocyclones.

Dans le cadre de cette thèse, un ouvrage de type séparateur hydrodynamique est étudié pour répondre aux problématiques environnementales liées aux déversements de macro-déchets en mer. La première partie est destinée à l’analyse du fonctionnement hydraulique de l’ouvrage et son aptitude face au colmatage sur un pilote en laboratoire. Les données collectées vont ensuite permettre la validation d’une approche numérique capable de simuler l’écoulement. Cette technique est par la suite utilisée pour optimiser l’écoulement et la forme de la grille. Nous avons démontré, à partir de simulations numériques, l’intérêt d’une grille de type métal déployé pour obtenir des phénomènes d’agitations turbulentes et de gradient de pression important à l’amont de la grille. Ces phénomènes favoriseraient ainsi la dispersion des polluants et limiteraient les phénomènes de colmatage. La dernière partie de ce travail a été d’étudier le fonctionnement d’un ouvrage grandeur nature et d’observer son efficacité
The installation of hydraulic structures to separate particles is a key element to improve the quality of water bodies. This PhD work focus on the study of a hydrodynamic separator used to capture large wastes before their discharge into the see. Tangential separation mechanism along a screen is used in this device. The first part of the work consists in studying the hydraulic behavior and the clogging effectiveness of the device with laboratory experiments. A CFD multiscale approach was developed in this work to optimize the shape of the screen in order to avoid clogging. This method, validated against experimental data, allows us to predict that expanded metal stripes are useful to develop turbulence and pressure gradients upstream the screen. This hydrodynamic phenomenon favor particles and pollutants ejection near the apertures. The last part of the work was to study the hydrodynamic behavior and the real efficiency with in situ experiments

Dans une problématique de réduction des volumes de déchet, l’électro-compression (ou électro-déshydratation) apparaît être une technique efficace pour éliminer une grande partie de l’eau des boues résiduaires urbaines. Cette thèse de doctorat présente différentes contributions à l’étude de ce procédé appliqué à ce type de boues. Un lien entre les données cinétiques et énergétiques est établi par une étude expérimentale à l’échelle du laboratoire. D’autre part, un nouveau modèle relativement simple est proposé pour l’étude et la simulation de l’électro-compression et permet de mettre en avant les phénomènes prépondérants. Enfin, un protocole d’analyse ionique des filtrats et des tranches de gâteaux de boue a permis une étude de la migration des espèces chimiques au cours de l’électro-déshydratation
In the purpose to reduce waste amount, the electro-dewatering process is a promising technique to efficiently withdraw a large part of the water included in wastewater sludge. This PhD thesis contributes in various ways to the study of this technique. Lab-scale experiments showed correlations between dewatering kinetics and energy consumption of the process. Moreover, a new model, relatively simple, is proposed to study and simulate the process. This model highlights the main phenomena involved in the electro-dewatering. Finally, a study of the migration of chemical species during the dewatering process is carried out thanks to an analytical protocol measuring ions in filtrates and sludge slices.1

The purpose of the study is to purify human growth hormone from the fermentation broth by affinity chromatography. For this purpose, human growth hormone specific oligonucleotide aptamers are selected among an aptamer library
selected oligonucleotides were synthesized and used as ligands. Effect of pH on ligand-human growth hormone complex formation was investigated and the highest complex formation was obtained at pH= 7.0. Human growth hormone is separated from the fermentation broth with 99.8% purity and 41% overall yield. The equilibrium data obtained was described by Langmuir type isotherm where saturation constant (q0) and affinity constant (K) are calculated as 0.338 mg hGH/µ
mol aptamer and 0.059 mg hGH/ml, respectively. Further, equilibrium data obtained using aptamer affinity column was described by Langmuir type isotherm where saturation constant (q0) and affinity constant (K) are 0.027 mg hGH/µ
mol aptamer and 1.543 mg hGH/ml, respectively. It is possible that, selected aptamer can be used for purification of bulk amounts of recombinant human growth hormone by using aptamer affinity chromatography.

Thesis (Ph. D.)--School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005. Directed by Charles A. Eckert.
Charles L. Liotta, Committee Co-Chair ; Charles A. Eckert, Committee Chair ; Amyn S. Teja, Committee Member ; J. Carson Meredith, Committee Member ; Rigoberto Hernandez, Committee Member. Vita. Includes bibliographical references.

Les colonnes à bulles sont des contacteurs gaz-liquide très répandus en milieu industriel, notamment dans des applications de procédés chimiques, biologiques et minéralogiques. Dans la gamme de colonne à bulles disponible, l'airlift sous dépression est une innovation française présentant des caractéristiques très intéressantes pour le pompage hydraulique, le transfert de masse et la séparation des matières en suspension. Ce travail de thèse s'inscrit dans le cadre du développement de cet airlift amélioré, très utilisé dans le milieu industriel. L'objectif de la thèse est la caractérisation hydrodynamique de la colonne airlift sous dépression et l'analyse de ses capacités à assurer la fonction de séparation solide-liquide pour des particules en suspension. Le travail est exclusivement expérimental et le dispositif expérimental est constitué d'une colonne à bulles verticale transparente en plexiglass soumise à une dépression en tête et connectée à un bassin de recirculation hydraulique. L'analyse hydrodynamique a été réalisée à l'aide de capteur de pression différentielle pour l'étude globale et à l'aide d'une double sonde optique pour une caractérisation locale. Les résultats obtenus ont permis d'étudier le régime d'écoulement pour les principaux paramètres : le taux de vide, la vitesse d'ascension et le diamètre des bulles. La Vélocimétrie par Images des Particules a été appliquée pour visualiser et analyser les structures d'écoulement dans le bassin de recirculation. Les capacités extractives de la colonne ont été étudiées en eau douce avec ajout de produits tensioactifs. La caséine soluble et le Methyl Iso Butyl Carbinol (MIBC) sont les deux tensioactifs qui ont donné les meilleurs résultats en termes de séparation solide-liquide des matières en suspension. Ce travail a contribué à la compréhension de l'hydrodynamique des airlift sous dépression et a permis de mettre en évidence les potentialités de cette colonne dans le processus de séparation solide-liquide. Le travail ouvre aussi la voie à la modélisation numérique de l'hydrodynamique de la colonne en s'appuyant sur les résultats expérimentaux
Bubble columns are gas-liquid contactors widely used in industry, especially in chemical, biological and mineralogical process applications. In the range of bubble columns available, the vacuum airlift is a French innovation with very interesting characteristics for hydraulic pumping, mass transfer and suspended matter separation. This thesis work is part of the development of this improved airlift, which is widely used in the industrial environment. The objective of the thesis is the hydrodynamic characterization of the airlift column under vacuum and analysis of its capacities to ensure the solid-liquid separation function. This work is exclusively experimental and the experimental setup is a vertical bubble column in plexiglass under vacuum and connected to a recirculation basin. The hydrodynamic analysis was carried out using a differential pressure sensor for the global study and using a double optical probe for local characterization. Results obtained made it possible to study flow regime. The main parameters obtained are the void fraction, superficial velocity and bubbles diameter. Particle Image Velocimetry is applied to visualize and analyze the flow structures in the recirculation basin. The extracting capacities of the column were studied in tap water with the addition of surfactants. Soluble casein and Methyl Iso Butyl Carbinol (MIBC) are the two surfactants that have given the best results in terms of solid-liquid separation of suspended matter. This work contributed to the understanding hydrodynamics for vacuum airlift column and helped to highlight the potential of this column in the solid-liquid separation process. This work also opens the way to numerical modelling of airlift column hydrodynamics from experimental results

Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.
Committee Chair: Boris Mizaikoff; Committee Member: Andrew Lyon; Committee Member: Ching-Hua Huang; Committee Member: David Collard; Committee Member: Facundo M. Fernandez.

A computational and physical modelling study is made of the removal of inclusions from liquid steel by use of a novel form of hydrocyclone in which a solid conical core that replaces the conventional vortex finder acts as a guide to the spiralling liquid flow and acts also as a capture surface for disentrained inclusions. In preliminary investigations, an inviscid computational model is derived that is found to be effective in outlining the general behaviour of specific hydrocyclone flows when tested against published experimental results. The more generally applicable commercial CFD code Fluent is likewise tested, from which it is shown that, among the turbulence models available, the anisotropic turbulence typical of spiralling hydrocyclone flows requires a form of Reynolds stress model for effective computation. The conventional k-c model is found to be misleading. On this basis, mathematical modelling and optimal computational design of hydrocyclones containing an axial conical solid core show that the separation efficiency of the cyclone is profoundly enhanced by the presence of a core, and that by use of a particle tracking model effective centripetal migration of inclusion particles in steel will occur towards the core. Experiments with a water model of computed optimal cyclone designs provided effective validation of the numerical study. Photographically active particles of neutral density were tracked by a novel stroboscopic technique which permitted bi-directional observation revealing instantaneous velocity, spatial position and spiral angle. Using populations of low density particles having the same spectrum of Stokes velocity as inclusions in the size range 35 to 150 microns found typically in liquid steel, sampling by Coulter counter showed that effective separation to the core surface of particles down to an equivalent size of 30 microns was achieved. In a final step, a pilot cyclone design for use with steel was established and water model tests at full scale showed that stable cyclone flow and discharge are achievable with gravity feed to the cyclone.

Drilling, one of the stages of oil and gas exploration, now has as targets regions of great complexity, with high depths. Coated or contaminated cuttings with drilling fluid are a result of drilling. The drilling fluids are water-based or non-aqueous based liquids. A more restrictive environmental legislation and the need to reduce the costs of drilling (exploration and production) lead to optimization of solid-liquid separation and recycling drilling fluids. Because oil industry has to submit itself to ever more stringent environmental laws it has applied a great deal of investments on sustainability research. In this context, this work provides a study of the characteristics of drilling cuttings and synthetic drilling muds at different steps of the solids control sistem, in order to know their behavior and its change over the process. The concentration of water, organic phase and solids in the mud were measured. The density and particle size of the cuttings were analyzed. The rheology and thixotropy of the mud were investigated. For this, samples of drilling mud were collected throughout the solids control system of five PETROBRAS onshore drilling rigs in Bahia (BA). The concentrations index are so important when investigating the efficiency of operation of the equipments in the solids control. The density of solids is very close to the density of clays. The results show that the rheology of drilling mud in the solids control process behaves as a non-Newtonian fluid, pseudoplastic, viscoplastic and thixotropic. The particle size of solids varies with operating conditions and always presents two average diameters by sample. The cutting dryer, a vertical centrifuge, plays a key role in the waste disposal due the stringent environmental laws, especially on offshore platforms. Thus, in order to research the optimization or restructuration of this step in the waste disposal, a study was carried on this equipment and the main points of its structure and operation were reported.
A perfuração, uma das etapas da exploração de petróleo e gás, hoje objetiva cenários geológicos de grande complexidade, com elevadas profundidades. Como efluente da atividade exploratória há a geração de cascalhos contaminados ou revestidos com fluido de perfuração. Uma legislação ambiental mais rigorosa e a necessidade de reduzir os custos de perfuração (prospecção e produção) apontam para a necessidade de otimização da separação e reciclagem do fluido de perfuração de poços de petróleo e gás. A atividade petrolífera é desenvolvida em condições cada vez mais restritivas do ponto de vista ambiental, sendo incessantes os estudos e investimentos em busca da sustentabilidade. Como exemplos de equipamentos para o processamento da lama de perfuração podem ser citados as peneiras vibratórias, os hidrociclones e as centrífugas. Neste contexto, o presente trabalho traz um estudo detalhado das características dos sólidos e da lama de perfuração base n-parafina em diferentes pontos do processo de controle de sólidos, com o objetivo de investigar o comportamento dos mesmos e sua alteração ao longo do processo. Foram realizadas análises de concentração de água, fase orgânica e sólidos na lama, densidade dos sólidos, reologia e tixotropia da lama e granulometria dos sólidos. Para isso, amostras de lama de perfuração foram coletadas ao longo do sistema de controle de sólidos em cinco sondas de perfuração terrestre da Petrobras no interior da Bahia (BA). As concentrações analisadas são de grande importância na investigação da eficiência de operação dos equipamentos do processo de controle de sólidos. A massa específica dos sólidos é bem próxima da massa específica de argilas. Os resultados de reologia mostram que a lama de perfuração em todo o processo de controle de sólidos se comporta como um fluido não-newtoniano, pseudoplástico, viscoplástico e tixotrópico. A granulometria dos sólidos varia com as condições de operação e apresenta, no geral, dois diâmetros médios em cada corrente amostrada. O secador de cascalho, um tipo de centrífuga vertical, desempenha papel fundamental na adequação dos resíduos às leis ambientais de descarte, principalmente em plataformas offshore. Assim, visando futuramente a otimização ou mesmo reestruturação desta etapa do processo de descarte de resíduos, foi realizado um estudo sobre esse equipamento e levantado os pontos principais de sua estrutura e operação.
Mestre em Engenharia Química

Significant advances in the understanding of chemical interactions at the solid-liquid interface have been made in this research through the use of diagnostic separations as a surface analysis technique. Diagnostic liquid chromatography has been employed in a detailed investigation of the thermodynamic and kinetic quantities which describe the interactions associated with a temperature induced conformational change in the octadecyldimethylsilane moieties of two different bonded silica materials. As a result of this study the nature of the structure and interactions of the ∼20Å thick interfacial region which acts as the stationary phase in reversed-phase liquid chromatography (RPLC) has been elucidated. The location and orientation of the average intermolecular interactions in the solvated layer stationary phase for solutes of differing hydrogen bonding ability and geometry has been determined as affected by bonded surface coverage, solvent hydrogen bonding competition and the structure of the solvated layer. These refinements in the model of the stationary phase solvated layer provide a much more detailed and accurate description of the intermolecular interactions responsible for retention and selectivity in RPLC than was previously available. A new modification of the method of measuring column mobile phase volume in RPLC employing retention linearization of an homologous series of compounds has been described from fundamental themodynamic principles and a statistically valid data reduction approach. The added advantage of providing thermodynamic information about the chromatographic system under study is inherent in this new technique. The experimental and theoretical bases for the new separation technique of magnetic field-flow fractionation (magnetic FFF) have been demonstrated. It has been shown that FFF techniques can be used in a diagnostic mode to study the dynamic stability of particle suspensions. The application of an external magnetic field to non-aqueous suspensions of sub-micron sized γFe₂O₃ particles, whose surface character has been modified by the adsorption of water, has been shown to enhance the suspension stability with respect to sedimentation. With the choice of proper operational conditions, magnetic FFF has also been demonstrated to be useful in monitoring particle flocculation as a result of its ability to separate particle flocculates on the basis of size.

This work is focused on the study of penetration of pesticides and pharmaceuticals in the aquatic environment. The aim was to develop and verify the optimal method for long-term monitoring of the occurrence of selected pesticides and pharmaceuticals in surface waters. Two frequently used analgesics ibuprofen and diclofenac, and carbamazepine that is used to treat epilepsy, were chosen from the group of drugs. A group of 41 pesticides were selected for monitoring too. The attention was focused on a group of urea pesticides and phenoxyacetic acids, as well as on selected pesticides falling to the group of priority substances or identified as environmental quality standards. Some of pesticides were selected because their consumption in the Czech Republic exceeds 30 tons a year. Liquid chromatography with tandem mass spectrometry (LC / MS / MS) was used for the determination of selected analytes in surface waters. Two optimized analytical method were developed. Ten analytes were determined in negative ion mode and 34 analytes in positive ion mode. Solid phase extraction (SPE) was used for purification and concentration of the samples. Developed methodology was validated and used for monitoring of selected compounds in samples of surface waters from the Morava River basin. Samples were collected on the rivers Morava and Svratka monthly for two years. Samples from the river Blata and stream Nivnička were collected for one year. Surface water samples were also collected from the river Litava. Four samples were taken throughout the length of the flow during one day. Smaller streams were chosen for monitoring because of the probability of occurrence of pesticides. They flow abundantly agriculturally cultivated areas. Drugs ibuprofen and diclofenac were detected in all taken samples, carbamazepine mostly. Among the most commonly occurring pesticides were bentazon, diuron, isoproturon, carbendazim, MCPA, MCPP, propiconazole, tebuconazole and 2,4-D.

Novel settling characteristic metrics were developed based on the fundamental mechanisms of coagulation, flocculation, and settling. The settling metrics determined parameters that are essential in monitoring and optimizing the activated sludge process without the need for expensive or specialized equipment. Current settling characteristic measurements that don't require specialized instruments such as sludge volume index (SVI) or initial settling velocity (ISV), have no fundamental basis in solid-liquid separation and only indicate whether settling is good or bad without providing information as to limitations present in a sludge matrix. Furthermore, the emergence of aerobic granulation as a potential pathway to mitigate solid-separation issues further stresses the need for new settling characteristic metrics to enable integration of the new technology with the current infrastructure. The granule or intrinsic aggregate fraction in different types was of sludge was quantified by simulating different surface overflow rates (SOR). The technique named Intrinsic Settling Classes (ISC) was able to separate granules and floc by simulating high SOR values due to the lack of a flocculation time needed for granules. The method had to be performed in a discrete settling environment to characterize a range of flocculation behavior and was able to classify the granular portion of five different types of sludge. ISC was proven to accurately (±2%) determine the granule fraction and discrete particle distribution. The major significance of the test is its ability to show if a system is producing particles that will eventually grow to become granules. This methodology proved to be very valuable in obtaining information as to the granular fraction of sludge and the granular production of a system. Flocculent settling (stokesian) was found to be predominant within ideally operating clarifiers, and the shift to 'slower' hindered settling (non-stokesian) causes both failure and poor effluent quality. Therefore, a new metric for settling characteristics was developed and classified as Limit of Stokesian Settling (LOSS). The technique consisted of determining the total suspended solids (TSS) concentration at which mixed liquor settling characteristics transition from stokesian to non–stokesian settling. An image analytical technique was developed with the aid of MATLAB to identify this transition. The MATLAB tool analyzed RGB images from video, and identified the presence of an interface by a dramatic shift in the Red indices. LOSS data for Secondary activated-sludge systems were analyzed for a period of 60 days at the Blue Plains Advanced Wastewater Treatment Plant. LOSS numbers collected experimentally were validated with the Takacs et al. (1991) settling model. When compared to flux curves with small changes in the sludge concentration matrix, LOSS was found to be faster at characterizing the hindered settling velocity and was less erratic. Simple batch experiments based on the critical settling velocity (CSV) selection were used as the basis for the development of two novel parameters: threshold of flocculation/flocculation limitation (TOF/a), and floc strength. TOF quantified the minimum solids concentration needed to form large flocs and was directly linked to collision efficiency. In hybrid systems, an exponential fitting on a CSV matrix was proposed to quantify the collision efficiency of flocs (a). Shear studies were conducted to quantify floc strength. The methods were applied to a wide spectrum of sludge types to show the broad applicability and sensitivity of the novel methods. Three different activated sludge systems from the Blue Plains AWWTP were monitored for a 1 year period to explore the relationship between effluent suspended solids (ESS) and activated sludge settling and flocculation behavior. Novel metrics based on the transitional solids concentration (TOF, and LOSS) were also collected weekly. A pilot clarifier and settling column were run and filmed to determine floc morphological properties. SVI was found to lose sensitivity (r < 0.20) when characterizing ISV above a hindered settling rate of 3 m h-1. ISV and LOSS had a strong correlation (r = 0.71), but ISV was subject to change, depending on the solids concentration. Two sludge matrix limitations influencing ESS were characterized by transition concentrations; pinpoint floc formation, and loose floc formation. Pinpoint flocs had TOF values above 400 mg TSS L-1; loose floc formation sludge had TOF and LOSS values below 400 mg TSS L-1 and 900 mg TSS L-1, respectively. TOF was found to correlate with the particle size distribution while LOSS correlated to the settling velocity distribution. The use of both TOF and LOSS is a quick and effective way to characterize limitations affecting ESS.
Ph. D.

A novel strategy to investigate interfaces relevant to chromatographic separations is presented. The strategy in this dissertation relies on three key ideas: 1) design and fabrication of appropriate model of chromatographic interface, 2) use of forced dewetting to separate interfacial constituent of mobile phase from its bulk component yet preserves the interface, and 3) use of IR spectroscopy and ellipsometry to investigate the structure and thickness of isolated interface.Stratified structures of ultrathin (< 10 nm thick) silica films on gold using gold oxide as adhesive layer and wetting control agent are used as model solid phase. Such design provides chemical environment of bulk silica surface, does not introduce significant spectral background, is suitable for reflection-based spectroscopies, and allow for easy modification to mimic wide range of silica - solvent interfaces. Bare silica-water models capillary electrophoresis interfaces; water-methanol mixture at octadecylsilane-modified silica represents reversed phase liquid chromatography interfaces.Forced dewetting is used to decouple interfacial constituent of mobile phase from its bulk component; yet, the integrity of interface is preserved. This approach, combined with the use of IR spectroscopy and ellipsometry, allowed for ambient atmosphere characterization of these interfacial layers in terms of their structure, composition, and thickness for water at bare silica. Hydrogen bonding was probed in case of complex water-methanol binary mixture at octadecylsilane-modified silica surface.The analysis of residual water layers formed by forced dewetting at bare silica as a function of bulk solution pH shows that the structure of the interfacial layer is highly ordered compared to bulk, and is also pH dependent. Further, thicknesses of interfacial layers were found to be pH dependent and vary from ~6 (pH 1) to ~9 nm (pH 9). Gouy-Chapman-Stern double layer was found to be inadequate to satisfactorily describe observed trends. In addition, surface enhanced infrared absorbance phenomenon was also observed that aided increased quality of resulting IR spectra.The analysis of residual water-methanol layers formed by forced dewetting at octadecylsilane-modified silica surface as a function of gas phase atmosphere shows that the structure of the interfacial layer is highly dependent on the composition of gas phase. The observed changes indicate that condensation of methanol from gas phase into residual layer and/or evaporation of water from residual layer into gas phase may occur in used experimental setup used in this dissertation. For that reason, more precise quantification of relative amounts of water and methanol in residual layers was precluded. Yet, regardless of investigational conditions, two different hydrogen bonding environments for methanol were distinctively observed.

ENGLISH ABSTRACT: Leaching of nickel laterite was conducted with a solution of ammonia and ammonium carbonate in a closed vessel. The vessel used in this study was designed to leach and perform solid-liquid separation at the same time. For solid-liquid separation, stainless steel sintered metal filter media were used. The sintered metal filter medium was selected for its high strength to withstand pressure, chemical resistance to caustic solution and back flushing properties. Optimum leaching conditions were determined by varying temperature, ammonia concentration, ammonium carbonate concentration and oxygen pressure. After leaching and filtration, the pH of the leach liquor was measured and samples were analyzed for dissolved metals (Ni, Fe and Co) using atomic absorption spectrophotometry. The most significant variable effect on leaching of nickel was the ammonia concentration. The maximum dissolution of nickel from the unroasted ore was 11.90% at 4 M NH3, 100oC, 2 M (NH4)2CO3 and 2 bar O2 pressure. Optimization from the leaching data was done using response profiling and desirability in Statistica software. Optimum leaching conditions were determined to be 3 M NH3, 2 M (NH4)2CO2, 100oC and 2 bar O2 pressure. The mineralogy of the ore before and after leaching was studied to understand why nickel extraction from unroasted ore was poor. XRF analysis of solids after leaching showed that iron, silicon, and magnesium remained the same. The only metal which showed significant decrease from solids was nickel. XRD analysis of solids after and before leaching showed that most mineral phases present in the ore are not affected by the leaching solution. SEM with EDS detection was used to determine nickel distribution within the ore. The results showed that nickel is mostly associated with iron. The iron is surrounded by magnesium and silicon. Silicate minerals do not react with ammonia and ammonium carbonate solution. From filtration experiments, the filtration differential pressure had no significant effect on the filtration rate. An average filtration rate of 0.29±0.07 ml/min.cm2 was obtained. The filtration rate from these experiments was very low. The main reason was due to quick pore clogging of sintered metals. Pore clogging was found to be mainly on the surface of the filter medium. Laterites have been found to have low permeability due a lot of clay present in the ore. Rheological studies on this ore showed that the ore has shear thickening behavior. However, a very clear filtrate was obtained. After each leach and filtration experiment, the sintered metals was unblocked by back flushing with water and air. Back flushing was successful because all 18 experiments were carried out using the same sintered filter medium. The effect of roasting the ore prior to leaching was investigated using optimum conditions obtained when leaching the unroasted ore. There was a slight improvement in nickel extraction when the ore was roasted. The average percentage extraction of nickel from 3 experimental runs was 19.25%±0.19 at 100oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. Some part of nickel in the ore was unextractable due to association of nickel with recrystallized silicate minerals in the reduced ore. Roasting improved permeability of the ore. The filtration rate improved significantly after roasting the ore. The average filtration rate was 2.60±0.05 ml/min.cm2. Dissolution kinetics of the unroasted and roasted saprolitic laterite were investigated with regard to the effects of temperature, ammonia concentration, ammonium carbonate concentration, and oxygen pressure. For the unroasted ore, it was found that dissolution rate and degree of nickel extraction increases with increasing temperature. Increase in ammonia concentration improves the degree of nickel extraction. Nevertheless, nickel extraction does not depend entirely on ammonia concentration because even when ammonia concentration is high and ammonium carbonate concentration is zero nickel extraction is low. An increase in ammonium carbonate concentration also increases the degree of nickel extraction. Ammonium carbonate is critical for the extraction, since ammonium ions in the solution prevent hydrolysis of the nickel ammine complex. Oxygen did not have a significant effect on the degree of nickel extraction. The leaching of nickel laterite was found to be a two stage leaching process. In the first stage, the dissolution of nickel is faster but after 15 minutes, the reaction rate is reduced. The reaction rate is reduced by inert minerals which host nickel. These minerals contain iron magnesium and silicon. The fast dissolution of nickel in the first stage represents leaching of free nickel in the ore. The data for the second stage of leaching was analyzed by the shrinking core model, and the results suggested that the dissolution rate is controlled by mixture kinetics (ash layer diffusion and surface reaction control). The activation energy for the dissolution reaction was calculated as 56.5 KJ/mol. The reaction order with respect to ammonia and ammonium carbonate were determined to be 0.3 and 0.26 respectively. For the roasted ore, the highest degree of nickel extraction was obtained at 60oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. The percentage extraction under these conditions was 28.7%. Temperature did not have a significant effect on the leaching rate. An increase in NH3 and (NH4)2CO3 increased the final extraction of nickel but did not have any effect on leaching rate in the first stage of leaching. In the absence of ammonium carbonate, nickel extraction is almost zero. The experimental data did not give linear fit to the shrinking core models investigated for the unroasted ore. The reason for this could be due to the sampling time interval which was too far apart, or the leaching behavior of roasted nickel is complicated and cannot explained by shrinking core model alone. Leaching experiments demonstrate that for a high degree metal extraction and improved reaction kinetics with ammonia and ammonium carbonate, the solution temperature should be high (>100oC) for the unroasted ore. In order to leach at high temperature with ammonia and ammonium carbonate a closed vessel is required to prevent reagent loses. The reaction kinetics showed that the reaction is controlled mostly by ash layer diffusion; this indicates that a low degree of nickel extraction in the unroasted saprolitic laterite is due to inert minerals (ash layer) which host nickel within the ore. In order to obtain a high degree of nickel extraction, the ore needs to be roasted under reducing conditions. Roasting conditions need to be carefully controlled to ensure high dissolution of nickel. In fact optimum roasting conditions which will give maximum dissolution of nickel, must be determined before working with the bulk of the ore.
AFRIKAANSE OPSOMMING: Logingstoetse van saprolitiese lateriet met 'n oplossing van ammonia en ammonium karbonaat is gedoen in 'n druk houer. Die logingsvat vir hierdie studie is ontwikkel om die loging sowel as die vloeistof – vastestof skeiding te doen. Gesinterde metaal filter medium was gebruik vir die vloeistof – vastestof skeiding aangesien dit die volgende eienskappe vertoon; die vermoë om druk te weerstaan, die chemiese weerstand teen bytsoda oplossing, asook voordelige terugspoel eienskappe. Optimum loogkondisies is bepaal deur die temperatuur, ammoniak konsentrasie, ammonium karbonaat konsentrasie, en suurstof druk te varieer. Na loging en filtrasie is die pH van die loogvloeistof gemeet en monsters is deur atoom absorpsie spektrofotometrie geanaliseer vir opgeloste metale (Ni, Fe en Co). Die veranderlike wat die grootste effek op die loging van nikkel gehad het was die ammoniak konsentrasie. Die maksimum herwinning van nikkel van uit ongeroosterde erts was 11.9 % by 4 M NH3, 100 oC, 2 M (NH4)2CO3 en 2 bar O2 druk. Optimisering van die loogdata is gedoen deur die respons profiel te analiseer met Statistica sagteware. Optimum loogkondisies was bepaal as 3 M NH3, 2 M (NH4)2CO2, 100 oC en 2 bar O2 druk. Die mineralogie van die erts voor en na loging is bestudeer om te bepaal waarom die nikel opbrengs van ongeroosterde erts so laag was. XRF analise van die vastestof na loging het gewys dat yster, silikon en magnesium nie deur loging affekteer is nie. Slegs nikkel het 'n merkwaardige afname getoon. XRD analsiese van die vastestof voor en na loging wys dat die meeste mineraal fases teenwoordig in die erts nie deur die loogoplossing affekteer is nie. SEM met EDS deteksie is gebruik om die nikkel verspreiding in die erts te bepaal. Die resultate wys dat nikkel meestal met yster assosieer. Die yster is omring deur magnesium en silikon. Silikaat minerale reageer nie met ammoniak en ammonium karbonaat oplossing nie. In filtrasie eksperimente is daar gevind dat die filtrasie differensiële druk geen noemenswaardige effek op die filtrasie tempo gehad het nie. Die gemiddelde filtrasietempo was 0.29+0.07 ml/min.cm2. Die filtrasie tempo van hierdie eksperimente was baie laag, hoofsaaklik as gevolg van blokkasie van porieë van die sinter metaal filter medium. Dit is gevind dat blokkasie van porieë hoofsaaklik op die oppervlak van die filter medium plaasvind. Lateriedes toon 'n lae deurlaatbaarheid as gevolg van die erts se hoë klei inhoud. Rheologiese studies op hierdie erts wys dat die erts skuif verdikking (“shear thickening”) gedrag vertoon. 'n Baie helder filtraat is egter verkry. Die gesinterde metale is na elke loog en filtrasie eksperiment skoongemaak deur terugspoeling met water en lug. Hierdie procedure was suksesvol, aangesien al 18 eksperimente met dieselfde filter medium uitgevoer is. Die effek van erts roostering voor loging is ondersoek by die optimum kondisies wat verkry was vir die loging van ongeroosterde erts. Nikkel ekstraksie het effens verbeter met geroosterde erts. Die gemiddelde persentasie ekstraksie van nikkel van drie eksperimentele lopies was 19.25 % + 0.19 by 100 oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar suurstofdruk. 'n Gedeelte van die nikkel in die erts was onherwinbaar as gevolg van die assosiasie van nikkel met her-gekristaliseerde sillikaat-minerale in die gereduseerde erts. Die porositeit van die erts is verbeter deur dit te rooster. Die filtrasie tempo het merkwaardig verbeter nadat die erts gerooster is. Die gemiddelde filtrasie tempo was 2.6+0.05 ml/min.cm2. Kinetika vir die oplossing van ongeroosterde en geroosterde saprolitiese lateriet is ondersoek, met in ag geneem die effekte van temperatuur, ammonia konsentrasie, ammonium karbonaat konsentrasie en suurstofdruk. Vir ongeroosterde erts is gevind dat die oplossingstempo en graad van nikkel ekstraksie toeneem met toenemende temperatuur. Toename in ammoniak konsentrasie lei tot 'n toename in nikkel ekstraksie, maar nikkel ekstraksie is nie alleenlik afhanklik van ammoniak nie. 'n Toename in ammonium karbonaat konsentrasie lei ook tot 'n toename in nikkel ekstraksie. Ammonium karbonaat is krities vir die ekstraksie, aangesien ammonium ione in die oplossing die hidrolise van die nikkel-amien kompleks verhoed. Suurstof het nie 'n merkwaardige effek op die totale nikkel ekstraksie gehad nie. Vir die bepaling van reaksie kinetika is 100˚C gebruik as die logingstemperatuur. Die loging van saprolitiese nikkel lateriet vind in twee stadia plaas. In die eerste fase is die oplossing van nikkel vinnig, maar na 15 minute neem die reaksietempo af. Die reaksietempo word verlaag deur inerte minerale wat teenwoordig is in die nikkel erts. Hierdie minerale bevat yster, magnesium en silikon. Die vinnige oplossing van nikkel in die eerste fase verteenwoordig die loging van vry nikkel in die erts. Die data vir die tweede stadium is geanaliseer deur die krimpende kern model, en die resultate dui aan dat die oplossingstempo deur 'n gemengde meganisme beheer word (as laag diffusie en oppervlak reaksie beheer). Die aktiveringsengergie vir die oplossingsreaksie was bereken as 56.5 kJ/mol. Die reaksieorde ten opsigte van ammoniak en ammonium karbonaat is onderskeidelik bepaal as 0.3 en 0.26. Die hoogste graad van nikkel ekstraksie vir die geroosterde erts is verkry by 60oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar O2 druk. Die persentasie ekstraksie by hierdie kondisies was 28.7 %. Temperatuur het nie 'n merkwaardige effek op loogtempo gehad nie. 'n Toename in NH3 en (NH4)2CO3 het die graad van nikkel ekstraksie laat toeneem, maar het nie enige effek op die loogtempo gehad nie. In die afwesigheid van ammonium karbonaat het byna geen nikkel ekstraksie plaasgevind nie. Die eksperimentele data het nie 'n lineêre passing vir die krimpende kern model soos vir die ongeroosterde erts ondersoek gegee nie. Die rede hiervoor is dat die monsternemings interval te groot was, of dat die logings karakteristiek van geroosterde nikel gekompliseerd is en nie alleen deur die krimpende kern model voorspel kan word nie. Logings eksperimente wys dat die temperatuur hoog moet wees (> 100 oC) om 'n hoë graad van nikkel ekstraksie te verkry met die ongeroosterde erts. 'n Geslote reaktor word benodig om by 'n hoë temperatuur met ammoniak en ammonium karbonaat te loog om reagens verliese te verhoed. Die reaksie kinetika word grootliks deur aslaag diffusie beheer. Hieruit kan gesien word dat 'n lae graad van nikkel ekstraksie uit die ongeroosterde saprolitiese lateriet die gevolg is van nie-reaktiewe minerale (aslaag) waarin die nikkel binne die erts bevat word. Om 'n hoë graad van nikkel ekstraksie te verkry moet die erts onder reduserende kondisies gerooster word. Rooster kondisies moet versigtig beheer word om hoë oplossing van nikkel te verseker. Optimum rooster kondisies om maksimum nikkel oplossing te verkry, moet bepaal word voordat daar met groter hoeveelhede erts gewerk kan word.

La premiere partie de ce manuscrit presente les resultats d'un travail de modelisation moleculaire applique aux interactions entre une proteine et une surface plane constituee d'un polymere synthetique qui porte des charges. Apres avoir expose les diverses composantes du modele, la methodologie employee et les interactions mises en jeu, nous simulons l'adsorption de deux proteines, l'alpha-lactalbumine et le lysozyme. L'ordre de retention des proteines ainsi que les selectivites calculees sont en accord avec l'experience. Dans une seconde phase, le modele subit une deuxieme serie de tests, vis-a-vis de mutants de la beta-lactoglobuline. Les resultats sont en accord avec l'experience et l'inclusion de l'alpha-lactalbumine dans cette serie conforte encore la fiabilite du modele. Les effets de la prise en compte des charges des residus histidines sont discutes. Dans une deuxieme partie, nous nous interessons a la modelisation des interactions electrostatiques telles qu'elles apparaissent en chromatographie d'affinite pour ion metallique immobilise. La methodologie employee est tres differentes puisqu'il s'agit d'un ligand de petite taille interagissant avec une proteine et non plus d'une surface. Notre approche recherche les sites potentiels de fixation sur la base de l'energie d'interaction avec une optimisation de la configuration du ligand dans le site. Nous mettons en evidence les sites preferentiels d'adsorption du (1,4,7-triaza)cyclononane complexe a un ion cu#2#+ sur l'alpha-lactalbumine et le lysozyme. Les dimeres du ligand et leurs diverses conformations sont envisages avec des possibilites de formation de structures en poignees qui evoquent des modes de reconnaissance specifiques. Ce travail a permis d'explorer les divers modes d'adsorption d'une proteine sur une surface plane modele ou une surface comportant des ligands greffes. Dans chaque cas, des orientations preferentielles de la proteine par rapport au support ont pu etre mises en evidence au niveau moleculaire et les approches developpees pour leur etude ont permis d'obtenir un bon accord avec l'experience.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Lorsqu'un solide est en contact avec un liquide, des phénomènes physico-chimiques conduisent à polariser l'interface. Deux zones de charge, de signe opposé, apparaissent à cette interface, une dans le solide et l'autre dans le liquide, formant ainsi la double couche électrique (DCE). Par rapport à la littérature existante, l’originalité de ce travail est de s’intéresser à la DCE à l’interface acier inoxydable 304L /film passif d’oxyde/ solution de NaCl (0.01M) en couplant des caractérisations électrochimiques, électriques et physiques. Une méthodologie de caractérisation par voie électrochimique en utilisant les méthodes de spectroscopie d’impédance (SIE) et de voltammétrie cyclique (CV) a été mise au point pour accéder à deux paramètres: la capacité effective et la densité surfacique de charge. Des modifications de la concentration de l'électrolyte, du potentiel appliqué et de l'état de surface ont ensuite été réalisées : la capacité effective de la DCE dépend principalement de la concentration et du potentiel et la densité surfacique de charge croît avec la concentration. Dans la gamme étudiée, la rugosité a une faible influence sur la capacité effective mesurée. Des analyses physico-chimiques de la surface ont permis de caractériser les films passifs formés sur l'acier, sans révéler de différences significatives entre les surfaces avant et après immersion. Un autre paramètre caractéristique de la DCE, la densité volumique de charge à la paroi, a été aussi déterminé par la méthode d'électrisation par écoulement du liquide. Les 3 méthodes de caractérisation (SIE, CV et électrisation) confirment l'influence de la concentration sur les caractéristiques de la DCE
When a metal is immersed in an electrolyte, a charge distribution is created at the interface and a potential is set up across the two phases. The separation between charges give rise to what are known as electric double layers (EDL). Compared to the usual solid/liquid interfaces investigated in the literature, this study is dedicated to the EDL at the stainless steel 304L / passive film / NaCl (0.01M) interface by combining electrochemical, electrical and physical methods. First, a methodology has been set up to characterise the EDL by the electrochemical methods: Electrochemical Impedance Spectroscopy (EIS) and cyclic voltammetry (CV). Both the effective capacity and the surface charge density were evaluated. Then, several parameters were investigated such as the electrolyte concentration, the applied potential and the influence on the EDL of the surface preparation. The results showed that the double layer capacitance depends mainly on the concentration of the electrolyte and on the applied potential. The roughness seems to have a poor influence on the measured capacitance. Various physico-chemical analysis were performed in order to characterise the passive films formed at the surface: no significant difference could have been evidence between the surfaces before and after immersion. Finally, the volume charge density was also determined by the liquid flow electrification measurement. Whatever the characterization techniques used (EIS, CV or flow electrification), the same trend was observed with regard to the influence of the concentration on the characteristics of the EDL