The aim of the current study is to model (non-wetting) liquid flow in a packed bed under the influence of gas flow. It has been observed experimentally that non-wetting liquid flows in a packed bed in form of small droplets and rivulets falling through the void regions. Continuum models have not been successful in predicting liquid flow paths when the liquid is injected through a point source in the packed bed. In the current study, we present a discrete deterministic model for modeling the liquid flow in a packed bed, under the influence of gas flow. When a high velocity gas blast in injected into a dry packed bed, a cavity or a void is formed in front of the nozzle. The cavity size increases with increasing gas velocity and exhibits hystersis in size upon increasing and decreasing gas flow rate. The cavity size is very important in determining the gas penetration into the packed bed. A proper gas flow profile prediction is necessary for determining it’s effect on the liquid flow behavior. Attempts at modeling cavity sizes have mostly been confined to experimental studies and development of correlations. Different correlations show different dependence on operating as well as bed parameters and a fundamental understanding of the cavity formation and hystersis phenomena is missing. We adopt a combined Eulerean-Lagrangian approach to study the above mentioned phenomena mathematically. Gas is modeled as a continua and solid as discrete (soft sphere D.E.M. approach). Hystersis and cavity formation studies are carried out in a 2D-slot rectangular packed bed. A discrete deterministic liquid flow model (developed and validated under structured packing conditions using x-ray radiography flow visualization technique), is used to study the effect of presence of liquid on the dry bed void size, when liquid is injected in a packed bed through a point source. It is found that the gas pushes the liquid away from the nozzle side wall. Also, the cavity sizes during gas velocity decreasing case are found to be larger in size than the void size obtained during velocity increasing case for the same inlet gas flow rate. This difference is void size leads to more gas penetration into the bed and thus more liquid shift away from the nozzle side wall. Presence of liquid is found to affect the void size (compared to dry bed size) negligibly.

<p>In this diploma work, the absorption of CO₂in different liquid solutions was studied by gas absorption in a randomly packed column. To characterize the absorption a few experiments with SO₂ absorption were made.The report has resulted due to the large amounts of carbon dioxide released into the atmosphere, mainly from fossil-fired power plants. To reduce these emissions, carbon dioxide can be separated from flue gas by different techniques such as CO₂ absorption with ammonia. The work consists of a theoretical and a laboratory part of measurements and calculations. In the experimental part a system of absorption and associated test equipment was constructed. Different liquid solutions of pure water, potassium carbonate solution and ammonia in various concentrations were used to catch carbon dioxide by countercurrent absorption. Also SO₂ was absorbed in the potassium carbonate solution to determine the gas film constant. The absorption efficiency of CO₂ ranged from a few percent in the experiment with water to up to 7% with potassium carbonate solution. The CO₂ absorption of ammonia varied with concentration and gave a separation of between 12 and 94%. Ammonia tests were made at both 10 and 20 °C. In general, a higher CO₂-capture at 20 °C was obtained as confirmed by theory.</p> / <p>I detta examensarbete har absorptionseffektivitet av CO₂ hos olika vätskelösningar undersökts genom gasabsorption i en slumpmässigt packad kolonn. För att karakterisera absorptionen absorberades även SO₂ i några experiment.</p><p>Rapporten är utförd med anledning av de stora mängder koldioxid som släpps ut i atmosfären, främst från fossileldade kraftverk. För att minska dessa utsläpp kan koldioxiden avskiljas från rökgaserna genom olika tekniker t.ex. genom CO₂-absorption med ammoniak.</p><p>Arbetet består av en teoridel och en laborativ del med mätningar och beräkningar. I den experimentella delen konstruerades ett system med en absorptionskolonn och tillhörande mätutrustning. Olika vätskelösningar bestående av rent vatten, kaliumkarbonatlösning och ammoniak i olika koncentrationer användes till att ta upp koldioxid genom motströms absorption. Även SO₂ absorberades i kaliumkarbonatlösning för att bestämma gasfilmkonstanten. Absorptionsgraden av CO₂ varierade från några få procent i försöket med vatten upp till 7 % med kaliumkarbonatlösningen. CO₂-absorptionen av ammoniak varierade med koncentrationen och gav en avskiljning på mellan 12 och 94 %. Ammoniakförsöken gjordes med både vid 10 och 20 °C. Generellt erhölls en bättre CO₂-avskiljning vid 20°C, vilket bekräftas av teorin.</p>

This experimental study explores the heat transfer from heated bare and finned tubular surfaces to particulates in packed bed cross flow. The results from this experiment will be used to help select the type of particulates that will be used. Additionally, these results will assist in estimating heat transfer in prototype and commercial particle to fluid heat exchangers (PFHX). This research is part of larger effort in the use of particulates in concentrating solar power technology. These solid particles are heated by concentrated sunlight to very high temperatures at which they are a suitable heat source for various thermal power and thermochemical cycles. Furthermore, one of the advantages of this concept is the ability to store thermal energy in the solid particles at relatively low cost. However, an important feature of any Particle Heat Receiver (PHR) system is the PFHX, which is the interface between the solar energy system and the thermal power or chemical system. In order to create this system material data is needed for the design and optimization of this PFHX. The paper focuses on the heat transfer properties of particulates to solid surfaces under plug flow conditions. The particulates will be evaluated for three grain sizes of sand and two grain sizes of proppants. These two materials will be tested at one, five and ten millimeters per second in order to see how the various flow rates, which will be required for different loads, will affect the heat transfer coefficient. Finally the heat transfer coefficient will also be evaluated for both finned and non-finned heat exchangers to see the effect that changes in the surface geometry and surface area have on the heat transfer coefficient. The heat transfer coefficient will help determine the appropriate material that will be used in the PHR system.

This study addressed the numerical modelling of flow and diffusion in packed beds of mono-sized spheres. Comprehensive research was conducted in order to implement various numerical approaches in explicit1 and implicit2 simulations of flow through packed beds of uniform spheres. It was noted from literature that the characterization of a packed bed using porosity as the only geometrical parameter is inadequate (Van Antwerpen, 2009) and is still under much deliberation due to the lack of understanding of different flow phenomena through packed beds. Explicit simulations are not only able to give insight into this lack of understanding in fluid mechanics, but can also be used to develop different flow correlations that can be implemented in implicit type simulations. The investigation into the modelling approach using STAR-CCM+®, presented a sound modelling methodology, capable of producing accurate numerical results. A new contact treatment was developed in this study that is able to model all the aspects of the contact geometry without compromising the computational resources. This study also showed, for the first time, that the LES (large eddy simulation) turbulence model was the only model capable of accurately predicting the pressure drop for low Reynolds numbers in the transition regime. The adopted modelling approach was partly validated in an extensive mesh independency test that showed an excellent agreement between the simulation and the KTA (1981) and Eisfeld and Schnitzlein (2001) correlations' predicted pressure drop values, deviating by between 0.54% and 3.45% respectively. This study also showed that explicit simulations are able to accurately model enhanced diffusion due to turbulent mixing, through packed beds. In the tortuosity study it was found that the tortuosity calculations were independent of the Reynolds number, and that the newly developed tortuosity tests were in good agreement with techniques used by Kim en Chen (2006), deviating by between 2.65% and 0.64%. The results from the TMD (thermal mixing degree) tests showed that there appears to be no explicit link between the porosity and mixing abilities of the packed beds tested, but this could be attributed to relatively small bed sizes used and the positioning and size of the warm inlet. A multi-velocity test showed that the TMD criterion is also independent of the Reynolds number. It was concluded that the results from the TMD tests indicated that more elaborate packed beds were needed to derive applicable conclusions from these type of mixing tests. The explicit BETS (braiding effect test section) simulation results confirmed the seemingly irregular temperature trends that were observed in the experimental data, deviating by between 5.44% and 2.29%. From the detail computational fluid dynamics (CFD) results it was possible to attribute these irregularities to the positioning of the thermocouples in high temperature gradient areas. The validation results obtained in the effective thermal conductivity study were in good agreement with the results of Kgame (2011) when the same fitting techniques were used, deviating by 5.1%. The results also showed that this fitting technique is highly sensitive for values of the square of the Pearson product moment correlation coefficient (RSQ) parameter and that the exclusion of the symmetry planes improved the RSQ results. It was concluded that the introduction of the new combined coefficient (CC) parameter is more suited for this type of fitting technique than using only the RSQ parameter. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012

The physiological benefits of flaxseed against pathological disturbances, such as cancers and heart diseases, are mainly attributed to its high lignan content. This study (Experiment 1) examined the application of pressurized low polarity water (PLPW) for extraction of lignans, proteins and carbohydrates from defatted flaxseed meal. Key processing conditions included temperature (130, 160, 190°C), solvent pH (4, 6.5 and 9), solvent to solid ratio (S/S) (90, 150 and 210 mL/g) and introduction of co-packing material (0 and 3 g glass beads). The addition of 3 g glass beads as co-packing material facilitated extraction by enhancing surface contact between the liquid and solid thus shortening extraction time. Elevated temperature accelerated the extraction rate by increasing the solid diffusion coefficient thereby reducing the extraction time. The maximum yield of lignans (99 %) was obtained at temperatures ranging from 160°C to 190°C, with solvent volume of 180 mL (90 mL/g meal) at pH 9. Optimal conditions for protein extraction (70 %) were pH 9, extraction volume of 420 mL (210 mL/g meal) and 160°C. Total carbohydrates yield was maximized at 50% recovery at pH 4 and 160°C with 420 mL solvent (210 mL/g meal). Increased temperature accelerated extraction, thus reducing solvent volume and time to reach equilibrium. For the extraction of proteins, however, a temperature of 130-160°C is recommended, as proteins are vulnerable to thermal degradation due to heat decomposition. The effects of flow rate and geometric dimensions for extraction of lignans and other flaxseed meal bioactives were further investigated in Experiment 2, based on the variables optimized in the previous experiment. Defatted flaxseed meal was extracted with pH 9 buffered water with meal to co-packing glass beads ratio of 1:1.5 at 5.2 MPa (750 psi) and 180°C. The aqueous extracts were analyzed for lignan, protein and carbohydrate using HPLC and colorimetric methods. The optimal extraction yields for lignan, protein and carbohydrate were found at flow rates of 1 to 2 mL/min with bed depth between 20 and 26 cm and a S/S ratio of 40 to 100 mL/g. The combination of low flow rate and high bed depth allowed the use of lower S/S ratio with reduced total solvent volume consumption. This study also evaluated the mass transfer kinetics governing the process of lignan extraction from flaxseed meal in a fixed bed extraction cell. Diffusion of solute into the continuously flowing solvent was mainly responsible for the mass transfer mechanism as flow rate did not increase proportionally with the yield and rate of extraction. The extraction kinetics were studied on the basis of two approaches: Fick’s diffusion equation and a two-site exponential kinetic model. The proposed two-site exponential kinetic model corresponding to the two-stage extraction (rapid and slow phases) successfully described the experimental data. Diffusivities attained from Fick’s diffusion model ranged from 2 x 10-13 to 9 x 10-13 m2s-1 while mass transfer coefficients were between 4.5 x 10-8 and 2.3 x 10-7 ms-1 for extraction of lignans at 180°C, pH 9 with 1:1.5 meal to co-packing material ratio.

Nano-liquid chromatography (nano-LC) was selected as analytical tool to develop different methods for chiral separations. Nano-LC offers several advantages over conventional LC, e.g., low sample requirement, short analysis time, easy coupling with mass spectrometer, and use of small amount of reagents, with a consequent low environmental pollution. In case of chiral separations, where expensive chiral stationary phases or chiral mobile phase additives (CMPA) have to be employed, nano-LC results very useful since it allows to perform analysis with small amount of this costly material. Initially, a derivatized β-cyclodextrin, heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin, was employed as CMPA for the chiral separation of some non steroidal anti-inflammatory drugs. The role of different achiral stationary phases in the separative process was investigated. The employed capillary columns were packed in the laboratory, following the slurry-packing procedure. Subsequently, the performance of a reversed phase C18 particulate packed column was compared with that one of a C18 monolithic column, in combination with cyclodextrins (heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin or hydroxypropyl--cyclodextrin) as CMPA. Finally, hydroxypropyl--cyclodextrin was selected as chiral selector to prepare chiral monolithic columns by one-step synthesis. For this aim, the cyclodextrin was activated as the allyl derivative. The composition of the polymeric mixture of the continuous beds was varied... [to full text] / Skysčių nano-chromatografija buvo pasirinkta kaip įrankis kurti įvairius chiralinių junginių atskyrimo metodus. Skysčių nano-chromatografija turi eilę privalumų, lyginant su tradiciniais skysčių chromatografijos metodais, pvz.: mažą bandinio poreikį, trumpą analizės trukmę, suderinamumą su masės spektrometrija ir nedideles tirpiklių, reagentų sąnaudas, todėl mažą aplinkos taršą. Chiralinių junginių analizei atlikti, kai reikalingos brangios chiralinės nejudrios fazės ar chiraliniai judrios fazes priedai, skysčių nano-chromatografija yra ypač naudinga, nes leidžia atlikti analizę su minimaliomis šių brangių medžiagų sąnaudomis. Pirmiausia, derivatizuotas β-ciklodekstrinas, heptakis (2,3,6-tri-O-metil) - β-ciklodekstrinas, buvo panaudotas kaip chiralinis nejudrios fazes priedas kai kurių nesteroidinių priešuždegiminių vaistų enantiomerams atskirti. Buvo įštirtas įvairių achiralinių nejudrių fazių vaidmuo atskyrimo procese. Šiuo tikslu naudojant suspensinį birių dalelių pakavimo metodą laboratorijoje buvo paruoštos kapiliarinės kolonėlės. Vėliau, buvo lyginama C18 biriais sorbentais pakrautų atvirkštinių fazių ir monolitinių kapiliarinių kolonėlių skiriamoji geba, chralinias judrios fazes priedais naudojant ciklodekstrinus (heptakis (2,3,6-tri-O-metil)-β-ciklodekstriną arba hidroksipropil-β-ciklodekstriną). Galiausiai, vienpakopės polimerizacijos būdu buvo gautos chiralines kapiliarines kolonėles, chiralniu selektoriumi naudojant hidroksipropil-β-ciklodekstriną. Šiuo tikslu... [toliau žr. visą tekstą]

Nano-liquid chromatography (nano-LC) was selected as analytical tool to develop different methods for chiral separations. Nano-LC offers several advantages over conventional LC, e.g., low sample requirement, short analysis time, easy coupling with mass spectrometer, and use of small amount of reagents, with a consequent low environmental pollution. In case of chiral separations, where expensive chiral stationary phases or chiral mobile phase additives (CMPA) have to be employed, nano-LC results very useful since it allows to perform analysis with small amount of this costly material. Initially, a derivatized β-cyclodextrin, heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin, was employed as CMPA for the chiral separation of some non steroidal anti-inflammatory drugs. The role of different achiral stationary phases in the separative process was investigated. The employed capillary columns were packed in the laboratory, following the slurry-packing procedure. Subsequently, the performance of a reversed phase C18 particulate packed column was compared with that one of a C18 monolithic column, in combination with cyclodextrins (heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin or hydroxypropyl--cyclodextrin) as CMPA. Finally, hydroxypropyl--cyclodextrin was selected as chiral selector to prepare chiral monolithic columns by one-step synthesis. For this aim, the cyclodextrin was activated as the allyl derivative. The composition of the polymeric mixture of the continuous beds was varied... [to full text] / Skysčių nano-chromatografija buvo pasirinkta kaip įrankis kurti įvairius chiralinių junginių atskyrimo metodus. Skysčių nano-chromatografija turi eilę privalumų, lyginant su tradiciniais skysčių chromatografijos metodais, pvz.: mažą bandinio poreikį, trumpą analizės trukmę, suderinamumą su masės spektrometrija ir nedideles tirpiklių, reagentų sąnaudas, todėl mažą aplinkos taršą. Chiralinių junginių analizei atlikti, kai reikalingos brangios chiralinės nejudrios fazės ar chiraliniai judrios fazes priedai, skysčių nano-chromatografija yra ypač naudinga, nes leidžia atlikti analizę su minimaliomis šių brangių medžiagų sąnaudomis. Pirmiausia, derivatizuotas β-ciklodekstrinas, heptakis (2,3,6-tri-O-metil) - β-ciklodekstrinas, buvo panaudotas kaip chiralinis nejudrios fazes priedas kai kurių nesteroidinių priešuždegiminių vaistų enantiomerams atskirti. Buvo įštirtas įvairių achiralinių nejudrių fazių vaidmuo atskyrimo procese. Šiuo tikslu naudojant suspensinį birių dalelių pakavimo metodą laboratorijoje buvo paruoštos kapiliarinės kolonėlės. Vėliau, buvo lyginama C18 biriais sorbentais pakrautų atvirkštinių fazių ir monolitinių kapiliarinių kolonėlių skiriamoji geba, chralinias judrios fazes priedais naudojant ciklodekstrinus (heptakis (2,3,6-tri-O-metil)-β-ciklodekstriną arba hidroksipropil-β-ciklodekstriną). Galiausiai, vienpakopės polimerizacijos būdu buvo gautos chiralines kapiliarines kolonėles, chiralniu selektoriumi naudojant hidroksipropil-β-ciklodekstriną. Šiuo tikslu... [toliau žr. visą tekstą]

During the last few decades, concerns about water shortages and pollution have increased. Consequently, environmental legislations and regulations for wastewater discharge have been issued. The objective of this work was to contribute in developing an efficient dsorbent for removing heavy metal ions from wastewater. The thesis focused on evaluating amine-modified SBA-15 as copper and other heavy metal ions adsorbent, by determining a variety of adsorptive properties with the aim of gaining a deep understanding of its behavior and to outline its advantages and limitations. The influence of synthesis conditions on the mesostructural stability of the resultant materials after different water treatments was systematically investigated. N2 adsorption results indicated that the material prepared via co-condensation and aged at 100 ºC was not stable and lost its ordered mesoporous structure after contacting water even at room temperature. Aging at 130 ºC and addition of inorganic salts resulted in materials that maintained their mesporous structure under different water treatments. The material synthesized in the presence of KCl was used as adsorbent for the rest of the thesis work. It was shown that the structural collapse observed in amine-modified SBA-15 prepared by conventional method when contacted with aqueous solutions is associated with the drying process, and not the treatment itself. This structural collapse was avoided by replacing water with more volatile liquids such as acetone, before drying. Amino-functionalized SBA-15 was tested for the removal of copper ions from aqueous solutions under different temperatures, pH, initial concentrations and agitation speeds. The obtained results indicated that the amino-functionalized SBA-15 was very efficient and equilibrium was achieved in less than 30 min at room temperature. The adsorption capacity increased dramatically with increasing temperature, initial copper concentration and pH. Under suitable conditions, the material exhibited high adsorption capacity even at very low copper concentration. To further investigate the effect of dsorption parameters, a 24 factorial design experiments were used to screen the factors affecting the copper removal efficiency. All the parameters main effects were significant within a 95 % confidence level. Surface composite design was used to develop a reliable model representing the adsorption process. The statistical tests used proved the adequacy of the second order model. Optimization of the factors levels was carried out and the recommended optimum conditions are: copper concentration of 20 mg/L, adsorbent/solution ratio of 1.57 g/L, pH of 6.5, and T = 294 K with 95% copper removal. The effect of regeneration conditions was investigated after three adsorption–desorption cycles, under different batchwise regeneration conditions. Using a composite surface design methodology, the effect of the regeneration conditions on the performance of the adsorbent was investigated. It was found that all the studied parameters have a statistically significant influence on the working dsorption capacity. With respect to structural properties and amine content, none of the factors was found to be significant. Regeneration using EDTA was found to be more efficient than acid treatment. Amino-functionalized SBA-15 was studied as potential absorbent for Cd2 +, Co2 +, Cu2 +, Zn2 +, Pb2 +, Ni2 +, Al3+ and Cr3 +. The adsorption capacity and selectivity of the material were investigated in single and multi-metal solutions. Using very dilute solutions, i.e., 10 ppm, more than 95% of cations were removed, except for Co2+ and Cr3 +, indicatingthe high sensitivity of the current adsorbent. The adsorption capacities in multi-metal solutions were lower than in single-metal ones because of competition between metallic elements for the amine groups. The adsorbent was not affected in the presence of sodium, potassium, and calcium, indicating that the ionic strength does not affect the adsorption properties. Application of this material to remove copper in tap water, river water, and electroplating wastewater was shown to be successful. Dynamic experiments were carried out on the adsorption of copper ions in a laboratory packed-bed of amine-modified SBA-15. Breakthrough curves were analyzed at different flowrates and after two adsorption-desorption cycles. Furthermore, a model based on mass balance was developed and tested for predicting the breakthrough curves under different experimental conditions used. The results suggested that the developed model was in good agreement with the experimental data. Bed regeneration was performed by circulating 0.2 M EDTA solution through the column for 30 min. Résumé Durant les quelques dernières décennies, les préoccupations concernant les pénuries d'eau et la pollution en général ont augmenté. Par conséquent, des législations et des réglementations environnementales pour les rejets d'eaux usées ont été introduites. L'objectif de ce travail était de contribuer au développement d'un adsorbant efficace pour éliminer les ions de métaux lourds des eaux usées. Cette thèse porte sur l'évaluation de SBA-15 modifiée avec des amines comme adsorbant pour le cuivre et d'autres ions de métaux lourds par la détermination d'une multitude de propriétés d'adsorption dans le but d'acquérir une profonde compréhension de son comportement et d’identifier ses avantages et ses limites. L'influence des conditions de synthèse sur la stabilité des matériaux mésoporeux obtenus après différents traitements a été étudié de façon systématique. Les résultats d'adsorption de N2 ont indiqué que le matériel préparé par co-condensation et vieilli à 100 °C n'était pas stable et a perdu sa structure mésoporeuse ordonnée après avoir été en contact avec l'eau même à température ambiante. Le vieillissement à 130 °C, avec ajout de sels inorganiques, a abouti à des matériaux qui ont maintenu leur structure mésoporeuse sous différents traitements en présence d'eau. Le matériau synthétisé en présence de KCl a été utilisé comme adsorbant pour le reste du travail de cette thèse. Il a été démontré que l'effondrement de la structure observé dans la SBA-15 modifiée aux amines, préparée par la méthode conventionnelle en contact avec des solutions aqueuses est associé avec le processus de séchage, et non le traitement lui-même. Cet effondrement de structure a été évité en remplaçant l'eau avec des liquides plus volatils tels que l'acétone, avant le séchage. La SBA-15 amino-fonctionnalisée a été testée pour l'élimination des ions de cuivre des solutions aqueuses à différentes températures, pH, concentrations initiales et vitesses d'agitation. Les résultats obtenus ont indiqué que la SBA-15 amino-fonctionnalisée était très efficace et l'équilibre a été atteint en moins de 30 min à température ambiante. La capacité d'adsorption a considérablement augmenté avec la température, la concentration initiale de cuivre et le pH. Sous des conditions appropriées, le matériau a manifesté une grande capacité d'adsorption, même à des concentrations très faibles en cuivre. Afin d’étudier l'effet des paramètres d'adsorption, un plan factoriel de 24 expériences a été utilisé pour dépister les facteurs affectant l'efficacité d'élimination du cuivre. Tous les effets principaux des paramètres étaient importants à 95% de niveau de confiance. La méthodologie de la surface composite a été utilisée pour développer un modèle fiable qui représente le processus d'adsorption. Les tests statistiques utilisés ont prouvé la pertinence du modèle de second ordre. L’optimisation des niveaux des facteurs a été effectuée et les conditions optimales recommandées sont: la concentration en cuivre de 20 mg/L, le rapport adsorbant/solution de 1.57 g/L, pH de 6.5 et T = 294 K pour l'élimination de 95% de cuivre. L'effet des conditions de régénération a été étudié après trois cycles d'adsorption-désorption, sous différentes conditions de régénération. En utilisant la méthodologie de la surface composite, l'effet des conditions de régénération sur la performance de l'adsorbant a été étudié. Il a été constaté que tous les paramètres étudiés ont une influence statistiquement significative sur la capacité de travail d'adsorption. En ce qui concerne les propriétés structurelles et la teneur en amine, aucun des facteurs n’a été jugé significatif. La régénération à l'aide d'EDTA a été jugée plus efficace que le traitement acide. La SBA-15 amino-fonctionnalisée a été étudiée comme absorbant potentiel de Cd2+, Co2+, Cu2+, Zn2+, Pb2+, Ni2+, Al3+ and Cr3+. La capacité d'adsorption et la sélectivité du matériau ont été étudiées dans des solutions mono- et multi-métalliques. En utilisant des solutions très diluées, soit 10 ppm, plus de 95% de cations ont été enlevés, sauf pour le Co2+ et Cr3+, indiquant la forte sensibilité de l'adsorbant. Les capacités d'adsorption dans les solutions multi-métalliques étaient inférieures à celles des solutions mono-métalliques en raison de la concurrence entre les éléments métalliques pour les groupes amine. L'adsorbant n'a pas été affecté par la présence de sodium, de potassium et de calcium, ce qui indique que la force ionique n'affecte pas les propriétés d'adsorption. L’usage avec succès de ce matériau pour éliminer le cuivre dans l'eau de robinet, l’eau de rivière et les eaux usées de galvanoplastie a été démontré. Des expériences dynamiques ont été réalisées sur l'adsorption des ions de cuivre par la SBA-15 amine-modifiée sur une colonne à lit fixe de laboratoire. Les courbes de perçage ont été analysées à des débits différents et après deux cycles d'adsorption-désorption. De plus, un modèle basé sur le bilan de matière a été développé et testé pour prédire les courbes de perçage sous les différentes conditions expérimentales utilisées. Les résultats suggèrent que le modèle développé est en bon accord avec les données expérimentales. La régénération du lit a été réalisée en faisant circuler une solution EDTA à 0.2 M à travers la colonne pendant 30 min.

The physiological benefits of flaxseed against pathological disturbances, such as cancers and heart diseases, are mainly attributed to its high lignan content. This study (Experiment 1) examined the application of pressurized low polarity water (PLPW) for extraction of lignans, proteins and carbohydrates from defatted flaxseed meal. Key processing conditions included temperature (130, 160, 190°C), solvent pH (4, 6.5 and 9), solvent to solid ratio (S/S) (90, 150 and 210 mL/g) and introduction of co-packing material (0 and 3 g glass beads). The addition of 3 g glass beads as co-packing material facilitated extraction by enhancing surface contact between the liquid and solid thus shortening extraction time. Elevated temperature accelerated the extraction rate by increasing the solid diffusion coefficient thereby reducing the extraction time. The maximum yield of lignans (99 %) was obtained at temperatures ranging from 160°C to 190°C, with solvent volume of 180 mL (90 mL/g meal) at pH 9. Optimal conditions for protein extraction (70 %) were pH 9, extraction volume of 420 mL (210 mL/g meal) and 160°C. Total carbohydrates yield was maximized at 50% recovery at pH 4 and 160°C with 420 mL solvent (210 mL/g meal). Increased temperature accelerated extraction, thus reducing solvent volume and time to reach equilibrium. For the extraction of proteins, however, a temperature of 130-160°C is recommended, as proteins are vulnerable to thermal degradation due to heat decomposition. The effects of flow rate and geometric dimensions for extraction of lignans and other flaxseed meal bioactives were further investigated in Experiment 2, based on the variables optimized in the previous experiment. Defatted flaxseed meal was extracted with pH 9 buffered water with meal to co-packing glass beads ratio of 1:1.5 at 5.2 MPa (750 psi) and 180°C. The aqueous extracts were analyzed for lignan, protein and carbohydrate using HPLC and colorimetric methods. The optimal extraction yields for lignan, protein and carbohydrate were found at flow rates of 1 to 2 mL/min with bed depth between 20 and 26 cm and a S/S ratio of 40 to 100 mL/g. The combination of low flow rate and high bed depth allowed the use of lower S/S ratio with reduced total solvent volume consumption. This study also evaluated the mass transfer kinetics governing the process of lignan extraction from flaxseed meal in a fixed bed extraction cell. Diffusion of solute into the continuously flowing solvent was mainly responsible for the mass transfer mechanism as flow rate did not increase proportionally with the yield and rate of extraction. The extraction kinetics were studied on the basis of two approaches: Fick’s diffusion equation and a two-site exponential kinetic model. The proposed two-site exponential kinetic model corresponding to the two-stage extraction (rapid and slow phases) successfully described the experimental data. Diffusivities attained from Fick’s diffusion model ranged from 2 x 10-13 to 9 x 10-13 m2s-1 while mass transfer coefficients were between 4.5 x 10-8 and 2.3 x 10-7 ms-1 for extraction of lignans at 180°C, pH 9 with 1:1.5 meal to co-packing material ratio.

Le tritium est un radioélément produit par fission ternaire ou activation neutronique au sein des réacteurs de fission et utilisé comme combustible dans les machines de fusion (comme, en autres, le JET en Angleterre ou le futur ITER à Cadarache). Des études sont actuellement en cours sur la gestion de cette ressource que ce soit en vue de son utilisation ou de son élimination d’effluents gazeux, liquides ou de déchets. Cette thèse se propose d’étudier la revalorisation du tritium en tant que combustible pour les machines de fusion par le biais d’un Réacteur Catalytique à Membrane (RCM). Celui-ci associe les phénomènes de conversion catalytique de l’eau tritiée, par échange isotopique avec le diprotium selon la réaction générique Q_2 O+H_2⇌H_2 O+Q_2 (Q=H,D ou T), et de perméation sélective, d’une membrane à base de palladium. Ce matériau présente une perméabilité exclusive aux isotopes de l’hydrogène H, D et T par formation respective d’hydrures, deutérures ou tritiures de palladium. Au sein du RCM, ces flux transmembranaires permettent, par retrait des produits de réactions, d’atteindre des taux de conversion plus élevés que dans un réacteur à lit fixe à parois imperméables (loi de Le Chatelier). Au CEA, un banc d’essais utilisant le deutérium comme simulant du tritium a été construit dans l’objectif d’étudier de manière séparée, à l’échelle du laboratoire, ces propriétés de conversion et de perméation ainsi que leur couplage. Grâce au développement d’une méthode permettant l’analyse simultanée des isotopologues de l’eau et du dihydrogène par spectrométrie de masse, il a été montré, d’une part, que le catalyseur à base de nickel utilisé présente une activité suffisante pour que l’état d’équilibre thermodynamique des réactions d’échange isotopique soit atteint très rapidement et d’autre part, que le flux de perméation des isotopologues du dihydrogène suit une loi de Richardson. Des analyses de sensibilités sur les paramètres opératoires montrent que les performances globales du RCM (i.e. facteur de dédeutération) croissent avec la température, la différence de pression transmembranaire, le débit de balayage et le temps de séjour dans le tube, mais passent par un maximum avec la variation de la teneur en vapeur d’eau lourde dans le gaz à traiter. Sur la base de ces observations, un modèle phénoménologique quantifiant les transferts de quantités de mouvement et de matière a été développé. Il rend compte du comportement global observé expérimentalement même si un effort reste à fournir sur la modélisation de la perméation des espèces hétéronucléaires. Grâce aux principes physiques sur lesquels il est basé et aux règles de similitudes existant entre les propriétés physico-chimiques des différents isotopologues (loi de Graham), ce modèle est aisément extrapolable au traitement d’espèces tritiées. / Tritium is produced in light and heavy water reactor fuel by ternary fission or neutron activation. This by-product is used as fuel in fusion fuel reactors such as JET in Culham or ITER in Cadarache (France). The growing interest of this research area will make the tritium fluxes increase; it is then worth addressing the question of its future whether it will be used or flushed out from liquid and gaseous effluents or waste. This thesis studies the recovery of tritium as fuel for fusion machines by means of packed bed membrane reactor (PBMR). Such a reactor combines catalytic conversion of tritiated water thanks to isotope exchange with hydrogen according to the reversible reaction Q_2 O+H_2⇌H_2 O+Q_2 (Q=H,D or T) and selective permeation of Q2 through Pd-based membrane. In fact, palladium has the ability to bond with hydrogen isotopes, creating a selective permeation barrier. In the PBMR, thanks to the reaction products withdrawal, these permeation fluxes drive the heavy water conversion rate, to higher values than those reached in conventional fixed bed reactors (Le Chatelier’s law). In order to study PBMRs, the CEA has built a test bench, using deuterium instead of tritium, allowing the analysis of their conversion and separation performances at the laboratory scale. An in-house method has been developed to determine simultaneously hydrogen and water isotopologues content by mass spectrometer analysis. It was experimentally shown that the activity of Ni-based catalyst used in this study was sufficient to allow the isotope exchange reactions to reach their thermodynamic equilibrium in a very short time. In addition, hydrogen permeation flux was shown to follow a Richardson’s law. Sensitivity studies performed on the PBMR’s main operating parameters revealed that its global performance (i.e. dedeuteration factor) increases with the temperature, the transmembrane pressure difference, the sweep gas flow rate and the residence time in the catalyst particle bed but reaches a maximum with the variation of heavy water content in the feed stream. According to these observations, a phenomenological 2D model, describing momentum and mass transfers, was developed. Simulations results are in good agreement with the general behavior observed experimentally. Results show that modeling of the permeation of heteronuclear species should account for crossed-interactions of the hydrogen isotopologues on the mass transfer of one specie. Nevertheless, thanks to the modeling approach used and the similitude rules existing between isotopologues’ physical and chemical properties (Graham’s law), this model can be easily extrapolated to the processing of tritium containing mixtures