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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

UTILIZAÇÃO DE DIFERENTES MATERIAIS COMO ADSORVENTES NA REMOÇÃO DE NITROGÊNIO AMONIACAL / DIFFERENT MATERIALS AS ADSORBENTS FOR THE REMOVAL OF NITROGEN AMMONIACAL

Silva, Naiana Pommerening da 09 January 2015 (has links)
The discharge of effluents without proper treatment, in water bodies has been one of the main environmental problems in aquatic systems. Macronutrients launched, such as nitrogen can cause the effect known as eutrophication leading to deterioration of the receiving body, smell, dissolved oxygen reduction, etc. Therefore, it is necessary to the viability of alternative processes to minimize the impact on the environment. Among them we can highlight the adsorption. In this work was up to evaluate the potential of ammonia nitrogen removal of Typha domingensis (Taboa) and activated carbon adsorption process by using synthetic wastewater produced from ammonia chloride solution (NH4Cl). Were used as adsorbents activated carbon, shoot and rhizome the Typha sp. The adsorption experiments were carried out in Wagner shaker with NH4 concentrations of 80, 160, 250 and 350 mg/L; solid sorbent concentration of 4 and 8 g/l and the residence time of 15, 30, 45, 60, 75, 90, 105 and 120 min., stirred at a speed of 15 rpm at a temperature 20±2 °C. The initial and resulting concentration was determined by spectrophotometry UV-VIS technique the method Nessler described in Vogel 1991. Was determined specific area and apparent density of the materials. The adsorption isotherms were generated in the models of Langmuir and Freundlich. The values found for specific surface area activated carbon, leaf, root and bagasse were 1357, 8270, 6708 and 10613 m²/g respectively. The resulting values of bulk density for activated carbon, leaf, root and bagasse were 0.885; 0.15; 0.27 and 0.24 g/cm³ respectively. There was little variation in the final concentration of ammonia in relation to the contact time for both materials. Leaf, root and bagasse showed no removal of ammonia at low concentrations (80 and 160 mg/L), so increasing the final concentration of the solution being added to the mass of 8 g/l. Positive results were found in concentrations of 250 and 350 mg/L, with a mean removal the 6 % for the materials. The activated carbon had removed 14 % at a concentration of 80 mg/L weight 4 g/l. The ammonia removal is greater with increasing the amount of activated carbon (8 g/L), since the plant largest removals was the mass 4 g/l of adsorbent. The removal efficiency is small for the temperature used in the experiments (20°C) and improves over the course of increasing contact time. The Freundlich model was the best fit for the activated carbon in the masses of 4 and 8 g/L, resulting correlation coefficient R² = 0.8702 and R² = 0.8936, respectively. However, the activated carbon can be used as an adsorbent for the removal of ammonia in domestic wastewater. The plant did not show satisfactory results ammonia removal at lower concentrations and is not suitable for use in sewage treatment. / O lançamento de efluentes, sem o devido tratamento, em corpos hídricos tem sido um dos principais problemas ambientais dos sistemas aquáticos. Os macronutrientes lançados, como o nitrogênio pode causar o efeito conhecido como eutrofização levando a deterioração do corpo receptor, odor, redução de oxigênio dissolvido, etc. Diante disso, faz-se necessário a viabilização de processos alternativos visando minimizar o impacto no meio ambiente. Entre eles pode-se destacar a adsorção. Neste trabalho teve-se como objetivo avaliar o potencial de remoção de nitrogênio amoniacal da Typha domingensis (Taboa) e do carvão ativado, por processo de adsorção, utilizando solução de cloreto de amônia (NH4Cl). Foram utilizados como adsorventes o carvão ativado, a parte aérea e o rizoma raízes da Typha sp. Os ensaios de adsorção foram realizados no agitador de Wagner com as concentrações de NH4 de 80, 160, 250 e 350 mg/L; concentração de sólido sorvente de 4 e 8 g/L e tempo de residência de 15, 30, 45, 60, 75, 90, 105 e 120 min., sob agitação com velocidade de 15 rpm, e temperatura de 20±2°C. A concentração inicial e resultante foi determinada pela técnica de espectrofotometria UV-VIS, pelo método de Nessler. Foi determinada a área específica e densidade aparente dos materiais. Foram geradas as isotermas de adsorção nos modelos de Langmuir e Freundlich. Os valores encontrados de área superficial específica para o carvão ativado, folha, raiz e bagaço foram de 1357, 8270, 6708 e 10613 m²/g respectivamente. Os valores resultantes de densidade aparente para carvão ativado, folha, raiz e bagaço foram 0,885; 0,15; 0,27 e 0,24 g/cm³ respectivamente. Houve pouca variação da concentração final de amônia em relação ao tempo de contato para ambos os materiais. Folha, raiz e bagaço não apresentaram remoção de amônia nas menores concentrações (80 e 160 mg/L) e, sim aumento da concentração final da solução, sendo maior para a massa de 8 g/L. Resultados positivos para estes materiais foram encontrados nas concentrações de 250 e 350 mg/L, apresentando remoção média de 6% para os materiais. O carvão ativado apresentou remoção de 14% na concentração de 80 mg/L com massa de 4 g/L. A remoção de amônia é maior com o aumento da quantidade de carvão ativado (8 g/L), já na planta as maiores remoções foram na massa de 4 g/L de adsorvente. A eficiência de remoção é pequena para a temperatura utilizada nos experimentos (20°C) e melhora com o decorrer do aumento do tempo de contato. O modelo de Freundlich foi o que melhor se ajustou para o carvão ativado nas massas de 4 e 8 g/L, obtendo coeficiente de correlação R² = 0,8702 e R² = 0,8936, respectivamente. Contudo, o carvão ativado pode ser utilizado como adsorvente na remoção de nitrogênio amoniacal em esgoto doméstico. A planta não mostrou resultados satisfatórios de remoção de amônia nas concentrações mais baixas, não sendo indicada para uso em tratamento de esgoto doméstico.
322

Impact de la texture de matériaux carbonés poreux sur la modification chimique d’électrodes de supercondensateurs : vers une meilleure intégration des molécules dans les dispositifs hybrides / Impact of porous carbonaceous material texture on supercapacitors’ electrodes chemical modification. : toward a better integration of molecules in hybrid devices

Benoit, Corentin 27 March 2017 (has links)
L’intégration des énergies renouvelables pour la production d’électricité impose une bonne maîtrise des flux énergétiques et le développement de nouveaux dispositifs de stockage de l’électricité est devenu un élément clé pour corriger l’intermittence des énergies éolienne et photovoltaïque. Parmi les dispositifs de stockage électrochimiques existants, les batteries se caractérisent par une grande densité d’énergie, mais souffrent d’une faible puissance, tandis que les supercondensateurs électrochimiques ont une faible densité d’énergie, mais conservent l’avantage d’une grande puissance. La difficulté à réunir ensemble puissance et énergie laisse vacant un large domaine du diagramme de Ragone, devenu la cible de nouveaux dispositifs hybrides. Une stratégie récente pour améliorer les performances des dispositifs de stockage consiste à greffer des molécules électroactives sur les matériaux d’électrodes, afin d’ajouter une contribution faradique au stockage. Cette approche modulaire permet de construire un matériau hybride sur mesure en fonction de l’application visée, mais la stratégie du greffage montre des limitations et des efforts restent à faire pour concilier les bonnes propriétés des molécules et du carbone, souvent utilisé pour cette application. Au cours de cette thèse, l’impact des propriétés de texture de matériaux carbonés poreux sur la modification chimique d’électrodes de supercondensateurs a été étudié afin de rationaliser la sélection des carbones et améliorer l’intégration des molécules. Dans cette perspective, le greffage du liant, jusqu’à présent considéré comme une masse "morte", sera considéré comme une alternative au greffage du carbone. / The integration of renewable energy into the production of electricity, forces us to conceive innovative charge storage systems to deal with the issue of the intermittent supply of wind and solar-generated electricity. At present, electric storage devices range from electrochemical capacitors, which can supply high power densities but suffer from low energy densities, to batteries, which are considered as a high-energydensity and low-power-density technology. The difficulty of combining the high power density of supercapacitors with the high energy density of batteries creates a large free area in the Ragone diagram that is targeted by new hybrid energy systems. A recent strategy consists in grafting fast redox-active small molecules onto the surface of porous carbons for producing organic storage devices at the frontier between electrochemical capacitors and batteries. This modular approach allows designing universal electrode materials applicable both for anode and cathode, but efforts are still needed for improving the integration of molecules in the microporous structure of carbons. In this thesis, we have studied the impact of textural properties of a series of carbons on the electrochemical performances of the corresponding carbon-molecules composite materials to rationalize the selection of carbons and enhancing the integration of molecules in the microposity of carbons. An novel approach, presented at the end of this work, for improving performance without decreasing the double-layer capacitance contribution and hindering the ionic transportation is to use the binder for the charge storage by grafting molecules onto its polymeric skeleton.
323

Metodos no convencionales para el tratamiento de aguas contaminadas con productos farmaceuticos / Traitements d'eau polluée par des produits pharmaceutiques

Quesada Penate, Isariebel 27 March 2009 (has links)
Des solutions modèles de lévodopa et de paracétamol, représentatives d'effluents pharmaceutiques, ont été traitées par adsorption et par des techniques non conventionnelles comme les ultrasons, l'oxydation en voie humide catalytique et le procédé séquentiel adsorption-oxydation ADOX, en utilisant des charbons actifs comme adsorbants et/ou catalyseurs. Les isothermes d'adsorption des deux composés sur trois charbons actifs ont été caractérisées, puis en oxydation, la puissance et la fréquence optimales des ultrasons ont été déterminées. Enfin, les études de cinétique d'oxydation catalytique en réacteur discontinu et du procédé séquentiel adsorption-oxydation en lit fixe ont montré que les propriétés morphologiques et les groupes superficiels présents sur le charbon actif jouent un rôle fondamental quand ce dernier est réutilisé pour plusieurs cycles d'oxydation. / The treatment of model aqueous solutions of paracetamol and levodopa, similar to those of pharmaceutical effluents, was studied. Adsorption and non conventional techniques, such as ultrasound, catalytic wet air oxidation and the sequential adsorption-oxidation AD-OX process, were evaluated. The activated carbons were used as adsorbents and catalysts. The adsorption isotherms of both products were experimentally determined on three activated carbons and then, the corresponding mathematical models were fitted. For oxidation under US, the optimal values of the ultrasonic power and frequency were determined. Finally, the kinetic study of CWAO of paracetamol and levodopa in a batch reactor and the sequential adsorption-oxidation of paracetamol in a fixed bed column showed that the morphological properties and the surface groups of activated carbons play an important role for the recycling of the carbons as catalysts.
324

Elaboration d'hydrogels composites chitosane/charbon actif à visée cicatrisante par procédés d'inversion de phase / Elaboration of chitosan/activated carbon composites hydrogels for wound dressings applications by phase inversion processes

Venault de Bourleuf, Antoine 24 September 2010 (has links)
Des hydrogels composites de chitosane et de charbon actif ont été préparés par séparation de phase induite par (i) contact de la solution de polymère avec une solution aqueuse de non-solvant (procédé par immersion) et (ii) pénétration de vapeurs de non-solvant dans la solution de polymère (procédé VIPS). La caractérisation multi-échelle (SAXS, WAXS, MEBE, module élastique, tests de diffusion) des gels a montré que le mode de contact n'avait pas d'influence sur les propriétés fonctionnelles des gels. Les structures obtenues sont homogènes, poreuses et amorphes. Elles conviennent pour constituer la couche de pansements cicatrisants en contact avec les plaies de type escarre. Un modèle original de gélification du chitosane, couplant transferts de matière, transferts de chaleur et réactions chimiques, a été élaboré. Il a permis de déterminer les temps caractéristiques de gélification, d'approcher les profils de concentration des espèces, et de corroborer la non-influence du procédé sur la structuration des matrices finales, par l'analyse des transferts mis en oeuvre. / Chitosan/Activated carbon composite hydrogels were prepared by phase separation induced by (i) immersing the polymeric solution in a non-solvent solution (wet process) and (ii) exposing the polymeric solution to non-solvent vapors (VIPS process). The multi-scale characterization approach (SAXS, WAXS, MEBE, storage modulus, diffusion tests) did not evidence any influence of the contact mode on the functional properties of the gels. Final structures are homogeneous, porous and amorphous. They are suitable to constitute the wound dressings layer in contact with eschar-like sores. An innovative chitosan gelation model was developed coupling mass transfers, heat transfers and chemical reactions. It permitted to forecast gelation times and concentration profiles. Simulation also corroborated the non-influence of the process on the final structuring of the matrices, analyzing transfers throughout the elaboration.
325

Produção de carvão ativado a partir de resíduos de coco, banana e laranja

Cavalcante, Valmir Rocha 12 May 2015 (has links)
Made available in DSpace on 2017-06-01T18:20:44Z (GMT). No. of bitstreams: 1 valmir_rocha_cavalcante.pdf: 556560 bytes, checksum: 7b21935e12943475da1325d0153dd7b8 (MD5) Previous issue date: 2015-05-12 / The increasing use of alternative waste activated carbon production ramped up this research project with the aim to develop new activated coals from coconut residue utilization, the banana and orange as precursor material, favoring the sustainability of the environment. Specific analyses were carried out and officers, noting the textural and chemical characteristics of these materials, since the literature does not describe the characteristics of activated carbon derived from the precursor material that will be used. First collected the fiber-to-dried coconut and banana and orange bagasse/cark for subsequent preparation of this material by impregnation with ZnCl2, chemical activation and performing a test for evaluating the efficiency of the coal. The results were an activated carbon with carbon mass fixed in all samples (coconut/banana = 25/75), (coconut/banana = 75/25), (coconut/orange = 75/25), showing efficiency in the reduction of pH, electric conductivity values and turbidity of the water. Therefore, the production of activated carbon from waste coconut, banana and orange presented, comparatively, the characteristics of activated coals ever produced for other waste and proved to be a viable alternative for the industry that has a vested interest in large-scale production, benefiting the industry and the environment. The activated carbon of banana and orange decreased the pH and electric conductivity; and the Orange was more effective in reducing turbidity in 98.4%. / A crescente utilização de resíduos alternativos para a produção de carvão ativado potencializou este projeto de pesquisa com o intuito de desenvolver novos carvões ativados a partir da utilização do resíduo do coco, da banana e da laranja como material precursor, favorecendo a sustentabilidade do ambiente. Foram realizadas análises específicas e oficiais, verificando as características texturais e químicas desses materiais, uma vez que a literatura não descreve as características do carvão ativado proveniente do material precursor que será utilizado. Primeiramente coletou-se a fibra-de-coco seco e bagaços/cascas de banana e de laranja para posterior preparação desse material através da impregnação com ZnCl2, da ativação química e da realização de um teste de avaliação da eficiência do carvão. Os resultados obtidos foram um carvão ativado com massa de carbono fixo em todas as amostras (coco/banana = 25/75), (coco/banana = 75/25), (coco/laranja = 75/25), apresentando eficiência na diminuição dos valores de pH, CE e turbidez da água. Portanto, a produção de carvão ativado a partir de resíduos de coco, banana e laranja apresentaram, comparativamente, as características dos carvões ativados já produzidos por outros resíduos e mostrou ser uma alternativa viável para a indústria que tem interesse em produção de larga escala, beneficiando a indústria e o ambiente. O carvão ativado de banana e laranja diminuiu os valores de pH e CE; e o de laranja foi mais efetivo na redução da turbidez em 98,4 %.
326

Efeito do laser de baixa potência associado ao uso de carvão ativado no processo de reparo ósseo em tíbia de ratos / Effect of low level laser associated with activated carbon in bone repair of rats

Sampaio, Alexandre Botelho de Abreu 17 December 2014 (has links)
Submitted by Nadir Basilio (nadirsb@uninove.br) on 2016-05-19T14:48:16Z No. of bitstreams: 1 Alexandre Botelho de Abreu Sampaio.pdf: 1511081 bytes, checksum: 0c16332d21fef3838342a4bf3977e18e (MD5) / Made available in DSpace on 2016-05-19T14:48:16Z (GMT). No. of bitstreams: 1 Alexandre Botelho de Abreu Sampaio.pdf: 1511081 bytes, checksum: 0c16332d21fef3838342a4bf3977e18e (MD5) Previous issue date: 2014-12-17 / The bone defects are caused by several factors and the repair process can be slow, where inflammatory and proliferative phases of remodeling of this tissue are extremely important for the quality of the repair. There are several therapies where the main is the surgery and in this case, the use of bone substitutes can be indicated. However the repair process may require assistance. Thus, the use of activated charcoal as bone substitute when the implementation of low-power laser to aid bone repair can be an alternative to these problems. The aim of this study was to verify the use of activated carbon as bone substitute and the interaction with the laser in the process of bone repair in rat tibias, assessing biochemical, histological and biomechanical changes. Material and methods: male wistar rats, 35 were used between 150 g to 200 g, with 3 months of age. The animals were anesthetized with ketamine hydrochloride and Association (90mg/Kg and 10mg/Kg, IP). Once anesthetized, the animals were put on surgical table, the skin was dissected and were made monocortical bone defects in the central region of the right tibia of mice. Immediately after surgery the rats were randomized and divided into the following groups: control (CTL), untreated Injury (NT), Lesion treated with activated carbon (CA), Lesion treated with association of activated carbon and laser 830nm, 6J-100mW (CA+L) and injury treated with Hydroxyapatite (HA). After 28 days the animals were euthanized with overdose of the same anesthetic, blood was collected and the tibia was taken for biochemical, histological and biomechanical analysis. Results: the NT group reduction in bending forces and histological changes related to disorganization of the tissue. The groups showed no CA+L and HA improves mechanical properties, however, the CA+L group presented histological aspects of improvement. Only the CA group presented better flexion forces, related with improvement of histological aspects and reduced levels of alkaline phosphatase. The NT groups, CA+L and HA presented high alkaline phosphatase levels. Conclusion: the use of activated carbon seems to improve the bone repair induced in this study. The laser association with activated carbon showed no improvement of biomechanical properties in spite of the histological results have a better aspect. / Os defeitos ósseos são causados por diversos fatores e o processo de reparo pode ser lento, onde as fases inflamatória, proliferativa e de remodelação deste tecido são extremamente importantes para a qualidade do reparo. Existem diversas terapias onde a principal é a cirúrgica e neste caso, o uso de substitutos ósseos pode ser indicado. No entanto o processo de reparo pode necessitar de auxilio. Assim, a utilização do carvão ativado como substituto ósseo quando a aplicação do laser de baixa potência para auxilio do reparo ósseo pode ser uma alternativa para estes problemas. O objetivo deste trabalho foi verificar a utilização do carvão ativado como substituto ósseo e a interação deste com a laserterapia, no processo de reparo ósseo em tíbias de ratos, avaliando alterações histológicas, bioquímicas e biomecânicas. Material e Métodos: Foram utilizados 35 ratos wistar, entre 150g à 200g, com 3 meses de idade. Os animais foram anestesiados com associação de cloridrato de quetamina e (90mg/Kg e 10mg/Kg, IP). Depois de anestesiados, os animais foram colocados em mesa cirúrgica, a pele foi dissecada e foram confeccionados defeitos ósseos monocorticais na região central da tíbia direita dos ratos. Imediatamente após a cirurgia os ratos foram randomizados e divididos nos seguintes grupos: Controle (CTL), Lesão não tratado (NT), Lesão tratado com carvão ativado (CA), Lesão tratado com associação do carvão ativo e laser 830nm, 6J – 100mW (CA+L) e lesão tratado com Hidroxiapatita (HA). Após 28 dias os animais foram eutanasiados com hiperdosagem do mesmo anestésico, o sangue foi coletado e a tíbia foi retirada para análises histológicas, bioquímicas e biomecânicas. Resultados: O grupo NT apresentou redução nas forças de flexão e alterações histológicas relacionadas a desorganização do tecido. Os grupos HA e CA+L não apresentaram melhora das propriedades mecânicas, porém, o grupo CA+L apresentou melhora dos aspectos histológicos. Somente o grupo CA apresentou melhora das forças de flexão, relacionado com melhora dos aspectos histológicos e redução dos níveis de fosfatase alcalina. Os grupos NT, CA+L e HA apresentaram níveis de fosfatase alcalina elevados. Conclusão: A utilização de carvão ativado parece melhorar o reparo ósseo induzido neste estudo. A associação do laser com o carvão ativado não apresentou melhora das propriedades biomecânicas apesar dos resultados histológicos apresentarem um aspecto melhor.
327

Purification of Indoor Air Pollutants Utilizing Hydrophobic Adsorbents

Yun, Ji Sub 05 January 2021 (has links)
Sick building syndrome (SBS) is a particular concern in places with inadequate ventilation and frequently attributed to chemical contaminants such as volatile organic compounds (VOCs)released from indoor sources that are frequently encountered in everyday life such as adhesives, carpeting, upholstery, manufactured wood products, copy machines, pesticides, cleaning agents inside buildings, plumbing vents, and painting. Furthermore, it is a major issue for modern human beings who spend most of their time indoors or must stay indoors for self-isolation due to special circumstances such as the coronavirus disease-19 (COVID-19) pandemic that occurred in 2019 and 2020. Main indoor VOCs are trichloroethylene (TCE), benzene, toluene, and para-xylene (p-xylene). In general, these compounds are not present in indoor spaces at acute concentrations, but prolonged exposure to these compounds can have chronic health effects such as allergic sensitization, increased cancer risks, and respiratory diseases. In this study, the adsorption process with various advantages has been applied to remove VOC’s using commercially available hydrophobic adsorbents. The hydrophobic adsorbents can contribute to reducing the possibility of chemical adsorption (chemisorption) of moisture from the air, which can decrease the capacity of adsorbent by clogging the pores. The adsorption of these major VOCs was investigated in this work for three major types of industrial hydrophobic adsorbents: activated carbons, zeolites, and polymer. This study will show the investigation into finding the most promising hydrophobic adsorbent for removal of TCE, benzene, toluene, and p-xylene, which are the main VOCs found indoors. The promising hydrophobic adsorbent has been determined by comparing Henry’s law constants and heat of adsorption values for the different adsorbents, which were estimated by using a concentration pulse chromatographic technique by utilizing a gas chromatograph equipped with a flame ionization detector. For all adsorbents, Henry’s law constants at room temperature of p-xylene were always the highest followed by toluene, benzene, and TCE. For all adsorbates, Henry’s law constants at room temperature of AC BPL and HiSiv 3000 were higher than the other hydrophobic adsorbents. For a developing modern society dealing with a pandemic, this study can contribute to producing the optimized gas masks and indoor filters for the removal of indoor air pollutants, which can help people who suffer from SBS. It can also help society for taking preventative actions towards dealing with SBS.
328

Caractérisations de matériaux pour la réalisation de supercondensateurs pour des applications automobiles / Characterization for materials for electrochemical capacitor and its further use in automotive applications

Liu, Yinghui 03 May 2018 (has links)
Dans le cadre d’une Convention CIFRE, la thèse est financée par la société Renault, ce travail vise à développer un supercondensateur carbone-carbone dont le coût de fabrication est compatible avec le marché automobile ; c’est en effet leur coût élevé qui constitue encore à l’heure actuelle un frein à leur développement. Dans une première partie de ce travail, il a été montré que l’essentiel du coût repose en grande partie sur la purification de l’électrolyte utilisé mais surtout du carbone activé, qui est le matériau actif d’électrode. Notre travail s’est donc focalisé sur l’étude du vieillissement électrochimique de cellules de supercondensateurs de laboratoire assemblées avec différents carbones, afin d’essayer d’identifier les phénomènes responsables du vieillissement. Un autre objectif a été d’identifier les caractéristiques que doivent présenter les carbones alternatifs candidats au remplacement des carbones commerciaux. L’étude réalisée dans ce travail de thèse a permis de définir deux modes de vieillissement différents suivants les carbones utilisés. Un premier type de vieillissement entraîne l’augmentation conjointe de la résistance série équivalente et de la capacité, dû à une dégradation/oxydation du carbone à l’électrode positive. Un second mode de vieilissement mène à l’augmentation seule de la résistance série équivalente par la formation d’une couche d’interface solide conductrice ionique. Quelque soit le mode vieillissement, aucune corrélation directe n’a pu être établie avec les fonctions de surface des carbones activés. La piste la plus probable repose sur le taux et la nature des impuretés présentes dans le carbone activé, certaines étant électroactives, voire pouvant jouer un rôle catalytique. / In the context of a CIFRE Convention, the thesis is financed by Renault s.a.s., this work aims at developing a carbon-carbon supercapacitor whose manufacturing cost is compatible with the automotive market, which still hinders their development. In a first part of this work, it has been shown that the cost mainly depends on the purity of the materials used: electrolyte but also activated carbon, the electrode active material. Our work has therefore been focused on the study of the electrochemical aging of laboratory supercapacitor cells assembled with different carbons, to identify their ageing mechanisms and to define the key features alternative carbons must achieve to replace commercial carbons. This work has evidenced two different modes of aging, depending on the carbon used. A first ageing mode results in the joint increase of the equivalent series resistance as well as the capacity, due to a degradation / oxidation of the carbon at the positive electrode. A second mode leads to the sole increase in equivalent series resistance by the formation of an ionic conductive solid interface layer. Whatever the aging mode, no clear influence of the surface functions of activated carbons could be evidenced. The most likely assumption is based on the content and the nature of the impurities present in the activated carbon, some of which are electroactive and can even play a catalytic role.
329

Optimalizace adsorpce kyseliny ferulové na různých typech adsorbentů / Optimalization of ferulic acid adsorption on different types of adsorbents

Bariyeva, Aizat January 2019 (has links)
This thesis deals with optimalization processes of adsorption of ferulic acid on different types of sorbents. Specifically, was used the activated carbon as a sorbent of heterogeneous character and Amberlyst A-21 and Amberlit XAD-16 as macroporous polymer sorbents. The ferulic acid is fully characterized in the theoretical part and are discussed the problems of adsorption processes. To determination of the phenolic acid were used UV-VIS and HPLC instrumental methods. The main aim of the experimental part is to optimize various parameters of adsorption, including the construction of adsorption isotherms, determination of maximum adsorption capacity of individual sorbents, study of kinetics and mechanisms of adsorption. Determination of the influence of salt was studied to assess the impact of the inorganic salts on the ferulic acid adsorption capacity. Based on these parameters, was carried out determination of an optimal pH value on 3, with an optimal adsorbent load (m/V ratio = 0,009 gml-1) and a contact time of 50 min for all three adsorbents. Equilibrium studies described by adsorption isotherms and the Langmiur model fitted the best, and the maximum adsorption capacities were determined for all three sorbents with 150,4 mgg-1 for activated carbon, 209,1 mgg-1 for Amberlyst A-21 and 82 mgg-1 for Amberlyte XAD-16. In the study of kinetic models was selected pseudo-second model for all three adsorbents, which correlated with the results obtained by the Langmuir isotherm. The decrease in adsorption capacity in the determination of NaCl influence was 4 % for activated carbon, for macroporous polymer sorbents was decreased by 52 % and 55 % for Amberlyst A-21 and Amberlyt XAD-16 respectively. In a selectivity test under optimized conditions, adsorption strength increased in the order of sinapic acid ferulic acid p-coumaric acid for polymeric sorbent XAD-16 and activated carbon. For the A-21 sorbent the adsorption strength increased in the order of p-coumaric acid ferulic acid sinapic acid. The results of the work indicate the suitability of all three sorbents for the phenolic acid adsorption.
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Understanding the Impacts of Harmful Algal Blooms on Biologically-Active Filtration for Drinking Water Treatment

Jeon, Youchul January 2020 (has links)
No description available.

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