Cette thèse a consisté en la fabrication d’électrodes de charbon actif frittées par SPS destinées aux supercondensateurs à double couche électrochimique. L’influence des paramètres de frittage (température, pression, durée du palier isotherme et vitesses de chauffe et de refroidissement) sur les propriétés structurales et microstructurales des pastilles de charbon actif a été évaluée par diffraction des rayons X, microscopie électronique à balayage et en transmission, spectrométrie de photoélectrons X, mesures de surface spécifique et de volume microporeux et détermination des propriétés mécaniques. Les performances électrochimiques des pastilles de charbon actif frittées sélectionnées pour leurs bonnes propriétés de volume microporeux, de résistance mécanique à l’électrolyte et de masse volumique élevée ont été déterminées par mesures galvanostatiques et de spectrométrie d’impédance. Un gain en capacité volumique de 31% a été obtenu pour un supercondensateur composé d’électrodes de charbon actif pur de 200 μm d’épaisseur frittées à 1100°C – 50 MPa par rapport à un supercondensateur composé d’électrodes de production de Blue Solutions. Cependant sa résistance série est deux fois supérieure à celle d’un supercondensateur de production de volume identique. Des résultats prometteurs de frittage multi-pastilles, possédant des propriétés microstructurales proches, indiquent une voie possible d’industrialisation du procédé SPS pour la fabrication d’électrodes frittées de charbon actif destinées aux supercondensateurs. / This thesis has consisted in the manufacturing of activated carbon electrodes sintered by SPS for Electric Double-Layer Capacitors (EDLCs). The influence of sintering parameters (temperature, pressure, isothermal dwell duration, heating and cooling rates) on structural and microstructural properties of sintered activated carbon pellets has been evaluated by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectrometry, specific area and microporous volume measurements and determination of mechanical properties. The electrochemical performances of sintered activated carbon pellets selected for their good properties in terms of microporous volume, mechanical resistance in the electrolyte and high density were determined by galvanostatic and impedance spectrometry measurements. A 31% increase of the volumetric capacity was obtained for a supercapacitor composed of 200 μm thick electrodes of pure activated carbon sintered at 1100°C – 50 MPa, relative to a supercapacitor composed of industrial electrodes from Blue Solutions company. However, its serial resistance is twice larger than that of an industrial of identical volume. Promising results of multi-pellet sintering, possessing close microstructural properties, indicate a possible way of industrialization of SPS process for the manufacturing of sintered activated carbon electrodes for supercapacitors.

Made available in DSpace on 2017-07-10T18:08:08Z (GMT). No. of bitstreams: 1 Eduardo Luiz Schneider.pdf: 569932 bytes, checksum: e3cef119c5d0e4b5c131836c91f0d834 (MD5) Previous issue date: 2008-02-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this study was evaluated the adsorption capacity of phenolics compounds on activated carbon. The carbon used in this work was chemically prepared from coconut shell and presented a surface area of 1181 m2 g-1. We ve done kinetics tests, equilibrium and thermodynamics tests, and also tests to verify the influence of physics and chemicals parameters on adsorption process, using the following phenolics compounds: p cresol, m cresol, phenol and hydroquinone. The data obtained in the equilibrium tests, ambient temperature (27ºC) and natural pH (liquid solution pH) of each compound, was used to adjust the adsorption isotherms. The models used were Freundlich, Langmuir, Redlich Peterson, Toth and Tempkin, being the best model that described the data, in the most of times, Redlich Peterson. The maximum quantity adsorbed of each compound followed the order: p cresol (Qmáx ≈ 47 mg g-1) > m cresol (Qmáx ≈ 45 mg g-1) > phenol (Qmáx ≈ 38 mg g-1) > hydroquinone (Qmáx ≈ 37 mg g-1). The kinetics tests were conducted in order to determinate the equilibrium time and verification of adsorption kinetics behavior of each compound. The equilibrium time for all compounds was 12 hours, but some of them reached the equilibrium before that time. The order of adsorption speed was: phenol (teq = 110 min) > p cresol (teq = 270 min) > m cresol (teq = 500 min) > hydroquinone (teq = 1000 min). Moreover, the kinetics data were adjusted to four models, being them: pseudo first order, pseudo - second order, intraparticle and Bangham. To phenol, the model that showed the best results was the pseudo model second order equation, to the cresols was the Bangham´s model and to the hydroquinone the pseudo second order and intraparticle. The thermodynamics tests were conducted in the following temperatures: 10, 20, 30, 40 and 50ºC and it were verified that adsorption process was exothermic and spontaneous. With thermodynamics data obtained, was possible determinate ΔHºads, ΔSºads e ΔGºads and to realize the heterogeneity study of activated carbon surface area. Moreover, we did tests to evaluate the pH, carbon mass and initial compound concentration influence on adsorption process. We verified that increasing the pH, the adsorption suffers prejudiced due to compounds dissociation. Increasing the carbon mass, the compound adsorbed quantity increases too, because there are more available sites to the adsorption. And increasing the initial compound concentration, the adsorption is favored because it increases the concentration difference of compound in the fluid and the carbon surface area, besides having more molecules to be adsorbed. In a general view, it was evaluated the capacity of phenol absorption in liquid solution on activated carbon, prepared from coconut shell, justified by the recent society preoccupation about the environment, were the industrial water waste which may contain harmful compounds to it, like phenol. So the studies of more efficient and better relation cost/benefit methods, to the removal of phenol are extremely important. / Neste estudo foi avaliada a capacidade de adsorção de fenóis sobre carvão ativado. O carvão utilizado neste trabalho foi preparado quimicamente a partir do endocarpo de coco e apresentou área superficial de 1181 m2g-1. Foram realizados testes cinéticos, de equilíbrio e termodinâmicos, além de testes para verificar a influência de parâmetros físicos e químicos no processo de adsorção, utilizando os seguintes compostos fenólicos: p cresol, m cresol, fenol e hidroquinona. Os dados obtidos nos testes de equilíbrio, temperatura de 28ºC e pH natural (pH do composto em solução aquosa) de cada composto, foram utilizados para o estudo de isotermas de adsorção. Os modelos utilizados foram Freundlich, Langmuir, Redlich Peterson, Toth e Tempkin, sendo o modelo que apresentou os melhores resultados, a isoterma de Redlich Peterson. A quantidade adsorvida máxima de cada composto seguiu a seguinte ordem: p cresol (Qmáx ≈ 47 mg g-1) > m cresol (Qmáx ≈ 45 mg g-1) > fenol (Qmáx ≈ 38 mg g-1) > hidroquinona (Qmáx ≈ 37 mg g-1). Os testes cinéticos foram realizados para determinação do tempo de equilíbrio e verificação do comportamento cinético da adsorção de cada composto. A ordem de velocidade de adsorção, ou seja, o tempo para cada composto atingir o equilíbrio foi a seguinte: fenol (teq ≈ 110 min) > p cresol (teq ≈ 270 min) > m cresol (teq ≈ 500 min) > hidroquinona (teq ≈ 1000 min). Além disso os dados cinéticos foram ajustados a quatro modelos cinéticos, sendo eles: pseudo primeira ordem, pseudo segunda ordem, intraparticula e Bangham. Para o fenol o modelo que apresentou os melhores resultados foi a equação de pseudo segunda ordem, para os cresóis foi o modelo de Bangham e para a hidroquinona o modelo de pseudo segunda ordem e intraparticula. Os testes termodinâmicos foram realizados nas temperaturas de 10, 20, 30, 40 e 50ºC e foi verificado que o processo de adsorção é exotérmico e espontâneo. Com os dados termodinâmicos obtidos, foi possível determinar as grandezas termodinâmicas ΔHºads, ΔSºads e ΔGºads e também realizar um estudo da heterogeneidade da superfície do carvão ativado. Além disso, foram realizados testes para avaliar a influência do pH, da massa de carvão e da concentração inicial do adsorbato no processo de adsorção. Foi verificado que, aumentando o pH a adsorção é prejudicada devido à dissociação dos compostos. Aumentando a massa de carvão aumenta a quantidade de adsorbato adsorvida devido ao aumento de sítios disponíveis para a adsorção. E aumentando a concentração inicial do adsorbato a adsorção também é favorecida pois aumenta a diferença de concentração do adsorbato no seio do fluido e na superfície do carvão, além de haver mais moléculas para serem adsorvidas. De um modo geral, foi estudado e avaliado a capacidade de adsorção de fenóis em solução aquosa sobre carvão ativado preparado a partir do endocarpo de coco, justificado pela recente preocupação da sociedade com o meio ambiente, onde o tratamento de efluentes industriais que contenham compostos nocivos ao ambiente, como os fenóis, tem se tornado alvo de grande preocupação, e portanto, o estudo de métodos mais eficientes e com melhor relação custo/beneficio para a remoção dos mesmos são de extrema importância.