Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-03-10T13:44:20Z No. of bitstreams: 1 PDF - Maria Natália Costa e Silva.pdf: 1280209 bytes, checksum: df5d2a51e71f30434a166906afcbecd3 (MD5) / Made available in DSpace on 2016-03-10T13:44:20Z (GMT). No. of bitstreams: 1 PDF - Maria Natália Costa e Silva.pdf: 1280209 bytes, checksum: df5d2a51e71f30434a166906afcbecd3 (MD5) Previous issue date: 2014-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The greater input of nutrients, such as nitrogen and phosphorus, from various anthropogenic uses of watersheds is one of the causes of the high growth rate of algae and cyanobacteria. Algae bloom impacts the quality of water causing taste and odor problems due to chemicals and toxins, called cyanotoxins, produced by these microorganisms. This situation, observed in sources of water supply, is worrying since the conventional treatment used by 70% of the water treatment stations in Brazil are not able to effectively remove those toxins. Studies performed by research groups around Brazil have shown the coexistence of two cyanobacteria, Microcystis aeruginosa and Cylindrospermopsis raciborskii, producers of the cyanotoxins microcystin and saxitoxins, respectively, which justifies the study of the removal of these toxins concomitantly. The aim of this study was to evaluate the ranking in removing microcystin-LR and saxitoxins-STX by adsorption on granular activated carbon (GAC) from different sources and particle sizes. Two types of palm coconut shell charcoal with the following mesh sizes 8x30 (FDG) and 12x40 (FDF) were used. A mineral charcoal with a 12x25mesh (FCM) was also used. The adsorption was made by filtration columns. The cyanotoxins were extracted from cultures of pure strains of M. aeruginosa and C. raciborskii. The method used for quantification was the immunoassay ELISA. First, we analyzed the removal efficiencies of MC-LR with each type of charcoal using samples of treated and distilled water. The filters were operated at a 66.3 m 3 /m 2 .d filtration rate. The results of this first phase showed a more effective removal of FDF (67.3%), although the average removal of FCM was higher (72.3%). In the second phase of the study, we analyzed the concomitant removal of MC-LR and STX using FDF at a 35.1 m 3 /m 2 .d filtration rate. The average removals of 58.9% and 92.5%, respectively, showed that the removal of saxitoxins is better, although we cannot assume that this toxin excels in the ranking. As for the difference between the filtration rates, we found that the removal is better with filters operating at a lower rate. / O aporte maior de nutrientes como nitrogênio e fósforo provenientes dos diversos usos antrópicos das bacias hidrográficas é um dos responsáveis pela alta taxa de crescimento de algas e cianobactérias. O bloom desses microrganismos modifica a qualidade da água, produzindo substâncias que conferem gosto e odor à água e até mesmo substâncias tóxicas, como as cianotoxinas. Essa situação presente nos mananciais de abastecimento é preocupante uma vez que o tratamento convencional utilizado por 70% das estações de tratamento de água no Brasil não são efetivamente capazes de remover tais substâncias tóxicas. O registro por grupos de pesquisa em todo país da presença conjunta de cianobactérias como a Microcystis aeruginosa e Cylindrospermopsis raciborskii, potencialmente produtoras das cianotoxinas microcistinas e saxitoxinas, respectivamente, justifica o estudo da remoção dessas toxinas em concomitância. O carvão ativado granular (CAG) é a tecnologia de tratamento avançado utilizada nesse trabalho que objetiva avaliar a hierarquização da remoção de microcistina-LR e saxitoxina STX por meio da adsorção em CAG de natureza e granulometrias distintas. Foram utilizadas colunas de filtração com dois carvões de casca de coco de dendê com granulometrias 8x30mesh (FDG) e 12x40mesh (FDF) e um carvão mineral com granulometria 12x25mesh (FCM). As cianotoxinas foram extraídas de cultivos de cepas puras de M. aeruginosa e C. raciborakii potencialmente produtoras e foi utilizado o método por imunoensaio ELISA para quantificação. Primeiramente foram analisadas as eficiências de remoção de MC-LR em cada tipo de carvão com águas de estudo formadas por água tratada e água destilada. Os filtros foram operados com taxa de filtração 66,3m³/m².d e os resultados dessa etapa evidenciaram remoção mais efetiva para o FDF (67,3%) apesar de a remoção média do FCM (72,3%) ter sido maior. Na segunda etapa do trabalho foi analisada a remoção em concomitância de MC-LR e STX e utilizou-se o FDF a uma taxa de 35,1m³/m².d em que as médias de remoção de 58,9% e 92,5%, respectivamente, evidenciaram que a saxitoxina apresenta melhor remoção, mas não se pode assumir que sobressai nessa hierarquia. Quanto à diferença nas taxas de filtração aplicadas, encontrou-se melhor remoção nos filtros operados com menor taxa.

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:32:41Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:36:32Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Made available in DSpace on 2014-09-15T18:36:32Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) Previous issue date: 2014-03-11 / In this work, activated carbon beads were prepared through carbonization of styrene-divinylbenzene (Sty-DVB) copolymers synthesized in the presence of soybean oil as diluent and cobalt ferrite nanoparticles dispersed in the organic phase. Firstly, a cobalt ferrite gel was prepared through co-precipitation technique with posterior surfactant action by oleic acid. The copolymer and the composites containing cobalt ferrite were obtained through suspension polymerization. Four matrixes were obtained, which have the following differences: the cobalt ferrite content (2 or 5 %), the amount of hydroxyethylcellulose used in the synthesis and the realization or not of a purification step before thermal treatments. Soybean oil was chosen as diluents in order to evaluate its effects on the synthesized materials considering the polymerization possibility due fat acid unsaturations and its low volatility. All synthesized materials were characterized by the following analysis: DRX, FTIR, TGA, nitrogen adsorption measurements (specific surface area, pore volume and pore size distribution), MEV and catalytic activity in the ethyl-benzene dehydrogenation reaction. Further, the composites had metal content evaluate by AAS. The soybean oil and the ferrite gel had a strong influence on the textural properties of copolymers and their respective activated carbons. All obtained activated carbons were active in relation to ethylbenzene dehydrogenation reaction. However, the activated carbon obtained from pure copolymer, i.e., without cobalt ferrite, presented the highest specific surface area, catalytic activity and selectivity. This catalyst also had the best stabilization of catalytic properties during evaluated reaction time. / Neste trabalho, esferas de carvão ativado foram preparadas através da carbonização de copolímeros estireno-divinilbenzeno (Sty-DVB) sintetizados na presença de óleo de soja como diluente e de nanopartículas de ferrita de cobalto dispersas na fase orgânica. Inicialmente, preparou-se um gel de ferrita de cobalto através da co-precipitação da ferrita de cobalto e posterior surfactação da mesma por ácido oleico. O copolímero e os compósitos poliméricos contendo gel de ferrita de cobalto foram obtidos através da técnica de polimerização em suspensão. Quatro matrizes foram sintetizadas, diferenciando-se apenas quanto ao conteúdo de gel de ferrita de cobalto (2 ou 5%), quantidade de hidroxietilcelulose usada na síntese e realização ou não de uma etapa de purificação antes dos tratamentos térmicos. O óleo de soja foi escolhido como diluente, a fim de avaliar a interferência de suas propriedades nos materiais sintetizados considerando a possibilidade de polimerizar-se devido à insaturações dos ácidos graxos e a sua baixa volatilidade. Todos os materiais sintetizados foram submetidos à caracterização através de análises de DRX, FTIR, TGA, adsorção física de nitrogênio (medidas de área superficial específica, volume de poros e distribuição de tamanhos de poros), MEV e atividade catalítica na reação de desidrogenação do etilbenzeno. Além disso, os compósitos (copolímeros contendo gel de ferrita de cobalto) tiveram os teores de metais quantificados por AAS. Foi verificado que o óleo de soja e a presença do gel de ferrita durante a polimerização influenciam nas propriedades texturais dos copolímeros e dos carvões sintetizados. Todos os carvões ativados obtidos mostraram-se ativos na reação de desidrogenação do etilbenzeno. Entretanto, o carvão obtido do copolímero puro (sem ferrita de cobalto) foi o que apresentou maiores valores de área superficial específica, taxas de conversão e de seletividade, além de uma maior estabilização durante os testes catalíticos realizados.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Este trabalho teve como objetivo estudar a adsorÃÃo de compostos poliaromÃticos em materiais nanoporosos para avaliar a reduÃÃo do teor destes compostos em misturas complexas de hidrocarbonetos. O destilado naftÃnico estudado neste trabalho foi produzido a partir de diferentes tipos de petrÃleos naftÃnicos nacionais, este produto tem alta aplicabilidade na indÃstria sisaleira (produÃÃo de fibras) por ser estÃvel e com alto ponto de fulgor, o que oferece seguranÃa no seu manuseio. Entretanto, por nÃo sofrer nenhum tratamento, o produto possui uma alta concentraÃÃo de compostos aromÃticos. Desta forma, Ã importante reduzir as concentraÃÃes desses compostos, sobretudo dos poliaromÃticos, para tornar os produtos menos perigosos Ãs pessoas que trabalham com o seu manuseio. AtravÃs de vÃrios mÃtodos analÃticos, foi possÃvel traÃar o perfil dos compostos aromÃticos presentes nas amostras da carga. Foram pesquisados e testados vÃrios adsorventes comerciais, dentre os materiais, destacaram-se os carvÃes ativados. AtravÃs dos experimentos em coluna, foi possÃvel avaliar a capacidade de adsorÃÃo em leito fixo dos carvÃes ativados, estimar parÃmetros de transferÃncia de massa e simular o comportamento breakthrough dos sistemas estudados. A dinÃmica de adsorÃÃo em leito fixo com misturas sintÃticas de poliaromÃticos foi utilizada para avaliar a capacidade dos melhores materiais (AC1 e AC2) e verificar a difusividade efetiva no interior das partÃculas. Foram avaliadas as propriedades fisico-quÃmicas e o teor de poliaromÃticos apÃs o tratamento. Os resultados confirmaram a eficiÃncia dos carvÃes ativados para utilizaÃÃo em processos de modulaÃÃo do teor de compostos poliaromÃticos do destilado naftÃnico estudado. / The removal of aromatics from mineral naphthenic oil by adsorption was studied. Commercial adsorbents were evaluated using batch experiments. The equilibrium data were fitted using the Langmuir equation. Column experiments were performed for three activated carbons samples that presented the best batch adsorption properties. A simulation model was used to predict the breakthrough curves for adsorption and desorption runs. After three cycles of adsorption/desorption, using n-hexane as eluent, only a slight decrease in aromatics capacity was observed. Activated carbon seemed to be adequate for aromatics removal in this system. Textural properties and detailed study of adsorption was performed using synthetic mixtures of pyrene. The adsorption capacities of adsorbents were obtained by batch experiments in three different temperatures and the isotherms were well adjusted by Langmuir equation. The dynamic adsorption was evaluated by successive breakthrough curves. The dynamic adsorption isotherms were well obtained from these experiments and were also well adjusted by Langmuir equation. The general model that account both internal and external resistances of mass transfer were used to predict the breakthrough curves and estimate the pore diffusivity.

A presente pesquisa descreve o preparo, caracterização e aplicação de novos adsorventes aplicados ao tratamento de efluentes contendo corantes. Os adsorventes produzidos neste estudo foram: Carvão ativado produzido por pirólise assistida por micro-ondas (AMWCST), a partir de um lodo coletado em uma Estação de Tratamento de Efluentes de curtume; e, biomassa fúngica tratada termicamente (BTV) a partir do fungo Trametes sp SC-10, os quais foram caracterizados de acordo a suas propriedades de textura e química de superfície e foram aplicados na remoção de corantes em solução aquosa e efluentes. Nesta pesquisa também se avaliou a eficiência do processo combinado entre coagulação-floculação e adsorção usando o AMWCST. Em suas propriedades estruturais, o AMWCST apresentou uma área superficial BET de 491,0 m2 g-1 e um volume total do poro de 0,440 cm3g-1, com distribuição de tamanho de poro majoritariamente mesoporosa; entretanto o BTV apresentou baixa área superficial destacando-se a formação de mesoporos. Foram estudados os equilíbrios e cinéticas de adsorção e sua correlação com modelos empíricos, para os sistemas AMWCST/PA-210 (Preto Ácido 210), e VA-357(Vermelho Ácido 357) e BTV/ AA-161 (Azul ácido 161). Para os dois primeiros sistemas empregando carvão ativado, a isoterma de adsorção de Liu foi a que descreveu melhor os dados de adsorção com capacidades máximas de 1108 mg g-1 e 589,5 mg g-1 a 298 K para PA-210 e VA-357. Para os estudos cinéticos, o modelo de ordem fraccionário de Avrami foi o melhor modelo ajustado para os dados experimentais. A BTV no entanto, mostrou uma capacidade máxima de biossorção de AA-161 de 221,7 mg g-1 a 303 K. O modelo de Langmuir foi o modelo que melhor descreveu os dados experimentais de equilibrios de biossorção e o Modelo Fraccionário de Avrami foi o que melhor descreveu a cinética de biossorção para o corante. A eficiência de remoção do adsorvente AMWCST no efluente sintético simulado foi de 93,79% e do BTV em um efluente simulado similar ao do processo de acabamento molhado de couro foi de 89,47%, indicando que a BTV é também um bom biossorvente para o tratamento de efluentes industriais. Finalmente, enquanto ao estudo de combinação de processos de coagulação-floculação com adsorção usando o AMWCST, este mostrou resultados eficazes na remoção do corante PA-210, em efluentes do processo de acabamento molhado, obtendo 85,20% de remoção do corante em comparação com o carvão comercial, o qual apresentou 88,64%. Além disso, utilizando o AMWCST, obtiveram-se reduções de 68,44%, 13,44% e 42,81% para COT, sódio total e amônio. / The present research describes the preparation, characterization and application of new adsorbents for the treatment of effluents contaminated with dyes. An adsorbent was activated carbon produced by pyrolysis microwave-assisted (AMWCST), from a sludge collected at a tannery Treatment Plant; The other adsorbent was a thermally treated fungal biomass (BTV) from Trametes sp. SC-10 fungi, which were characterized according to their texture and surface chemistry properties and were applied in the removal of dyes in aqueous solution and effluents. In this research, the efficiency of the combined coagulation-flocculation and adsorption process using the AMWCST was also evaluated. As for the texture properties, the AMWCST presented a BET surface area of 491.0 m2g-1 and a total pore volume of 0.440 cm3g-1, with mesoporous pore size distribution; However, BTV presented low surface area, highlighting the formation of mesopores. As for adsorption equilibria and kinetics and their correlation with theoretical models, for the AMWCST / AB-210, and AR-357 and BTV/AB-161 systems. For the first two systems using activated carbon, the Liu adsorption isotherm was the model that best described the adsorption data with maximum capacities of 1108 mg g-1 and 589,5 mg g-1 at 298 K for AB- 210 and AR- 357. For the kinetic studies, the Avrami fractional order model was the best-fit model for the experimental data. BTV however, showed a maximum AB-161 biosorption capacity of 221.7 mg g-1 at 303K. The Langmuir model was the model that best described the experimental data of biosorption equilibria and the Avrami Fractional Model best described the kinetics of biosorption for the dye. The adsorption efficiency of the AMWCTS in the synthetic simulated effluent was 93.79% and the BTV in a simulated effluent similar to that of the wet-end process in the leather industry was 89.47%, indicating that BTV is also a good biosorbent for the treatment of industrial effluents. Finally, while studying the combination of coagulation-flocculation processes with adsorption using the AMWCST, it showed efficient results in the removal of the AB-210 dye in wet-end process effluents, obtaining 85.20% dye removal compared with commercial activated carbon, which had 88.64%. In addition, using AMWCST, reductions of 68.44%, 13.44% and 42.81% were obtained for TOC, total sodium and ammonium.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-02-20T18:37:20Z No. of bitstreams: 1 2017 - Rayssa de Medeiros Morais.pdf: 2513069 bytes, checksum: 0a51c44b7c496c4aea2fc3ff92d026bf (MD5) / Made available in DSpace on 2018-02-20T18:37:20Z (GMT). No. of bitstreams: 1 2017 - Rayssa de Medeiros Morais.pdf: 2513069 bytes, checksum: 0a51c44b7c496c4aea2fc3ff92d026bf (MD5) Previous issue date: 2017-02-16 / CNPq / This study had as an objective to produce activated carbon (ACs) from Bambusa vulgaris, Eucalyptus dunnii and endocarp of Cocos nucifera; characterize the materials produced and evaluate their potential for adsorption of the methylene blue compound, contaminant of the textile industry. For this, activated carbon was produced via physical, using the water vapor as the activating agent. BET surface area (SBET), scanning electron microscopy (SEM), Boehm titration method (BOEHM), point of zero charge (pHpzc) and thermogravimetric analysis (TGA) were characterized. In order to evaluate these materials application, adsorption studies were performed with a contaminant from the textile industry, the methylene blue dye which was considered as a model compound for several adsorption studies. The precursors studied have produced excellent ACs which can be used as adsorbents in aqueous media. The ACs produced from bamboo and eucalyptus obtained superior performance to that produced from the coconut endocarp, which was used as a quality comparative in this study. All the ACs showed very close characteristics, but the activated carbon of bamboo and eucalyptus had better performance with a SBET superior than 500 m2 g-1, removal percentage above 90% at equilibrium time and maximum adsorption capacity around of 300 mg g-1. The three ACs produced obtained pHpzc from 7.0 to 7.5, presented predominance of acidic groups on their surface, mainly the carboxylic groups, and the analysis of the obtained micrographs showed a porosity development due to the activation. The materials have shown good thermal stability, and the regeneration process is possible with small mass losses. Although the bamboo AC has SBET superior to the eucalyptus AC, this did not guarantee that it obtained better performance in adsorption kinetics for the methylene blue, which confirms that other factors such as pore size influence the adsorption process. The bamboo and eucalyptus ACs fit better to the Langmuir model (monolayer), while the coconut AC to the Freundlich (multilayer) model. Finally, it is concluded that the different precursors studied allowed the activated carbons production with excellent textural and adsorptive characteristics; and further studies should be conducted to improve even more the qualities. / Este estudo teve por objetivo produzir carv?es ativados (CAs) a partir de Bambusa vulgaris, Eucalyptus dunnii e endocarpo do Cocos nucifera; caracterizar os materiais produzidos e avaliar seu potencial para adsor??o do composto azul de metileno, contaminante da ind?stria t?xtil. Para isso, foram produzidos carv?es ativados por via f?sica, utilizando como agente ativante o vapor d??gua. Os mesmos foram caracterizados por ?rea superficial BET (SBET), microscopia eletr?nica de varredura (MEV), m?todo titulom?trico de Boehm (BOEHM), pH do ponto de carga zero (pHPCZ) e an?lise termogravim?trica (ATG). Com finalidade de avaliar a aplica??o destes materiais foram realizados estudos de adsor??o com um contaminante da ind?stria t?xtil, o corante azul de metileno, sendo este tido como um composto modelo para diversos estudos de adsor??o. Os precursores estudados produziram excelentes CAs que podem ser utilizados como adsorventes em meio aquoso. Os CAs produzidos a partir de bambu e eucalipto obtiveram desempenho superior ao produzido a partir do endocarpo de coco, que foi usado como comparativo de qualidade neste estudo. Todos os CAs apresentaram caracter?sticas muito pr?ximas, por?m os carv?es ativados de bambu e de eucalipto obtiveram um melhor desempenho com uma SBET superior a 500 m2 g-1, percentual de remo??o acima de 90% no tempo de equil?brio e capacidade m?xima de adsor??o por volta de 300 mg g-1. Os tr?s CAs produzidos obtiveram pHPCZ entre 7,0-7,5, apresentaram predomin?ncia de grupos ?cidos em sua superf?cie, principalmente os grupos carbox?licos, e pela an?lise das micrografias obtidas apresentaram um desenvolvimento da porosidade devido ? ativa??o. Os materiais mostraram possuir boa estabilidade t?rmica, e o processo de regenera??o ? poss?vel, com pequenas perdas de massa. Apesar do CA de bambu possuir SBET superior ao CA de eucalipto, isto n?o garantiu que o mesmo obtivesse melhor desempenho na cin?tica de adsor??o para o azul de metileno, o que confirma que outros fatores como o tamanho de poros influenciam o processo de adsor??o. Os CAs de bambu e eucalipto se ajustaram melhor ao modelo de Langmuir (monocamada), enquanto o CA de coco ao modelo de Freundlich (multicamada). Por fim, conclui-se que os diferentes precursores estudados propiciaram a produ??o de carv?es ativados com excelentes caracter?sticas texturais e adsortivas; e a posteriori novos estudos devem ser conduzidos para aprimorar ainda mais essas qualidades.

Nanoporous materials for gas purification and thermal insulation have been studied and developed for application in many areas. It is known that a single adsorbent may not adequately control multiple contaminants. Further the utilization of nanoporous material as thermal insulator in building applications is limited due to high cost. Moreover, in view of the global environmental movement for clean air and reduction of heating energy consumption in built environment, the development of new and better nanoporous materials will not only facilitate major advances in gas adsorption and thermal insulation technology, but also meet the new challenges that cannot be met with the nanoporous materials that are currently available. This thesis presents a synthesis of new nanoporous silica based materials, and the characterization and application of these materials for molecular filtration and thermal insulation. Commercial nanoporous materials have been used for benchmarking for the pore properties, the applicability, and the performance of these new materials. First a double metal-silica adsorbent has been synthesized. The preparation procedure is based on the use of sodium silicate coagulated with various ratios of magnesium and calcium salts which yields micro-meso porous structures in the resulting material. The results show that molar ratios of Mg/Ca influence the pore parameters as well as the structure and morphology. The bimodal pore size can be tailored by controlling the Mg/Ca ratio. In the second synthesis, pure mesoporous silica, SNP has been prepared using glycerol as pore forming agent and monovalent salts as coagulant. This leads to material with large surface area and uniformed pore size centred at 43 or 47 nm.  The materials further exhibits a low bulk density in the range of 0.077 to 0.122 g/ml and possess a high porosity in the range of 95-97%. The influence of acid type (organic or inorganic) on the pore parameters and on the tapped density has also been investigated.   A synthesis method has also been developed for the preparation of carbon-silica composites. The method involves a number of routes, which can be summarised as addition of activated carbon particles to (I) the paste, (II) the salt solution, or (III) with the sodium silicate solution. In route II and III the activated carbon is present before coagulation. The routes presented here leads to carbon-silica composites possessing high micro porosity, meso porosity as well as large surface areas. The results further shows that pore size distribution may be tailored based on the route of addition of the carbon particles. Following route I and III a wide pore size (1-30 nm) was obtained whereas by route II a narrow pore size (1-4 nm) was observed.     MgCa-silica chemisorbents were also developed using either potassium hydroxide or potassium permanganate as impregnate chemicals. A direct or post-impregnation procedure was employed. The results revealed that the impregnate route and amount cause a reduction in both specific surface area and pore volume. Finally the thermal conductivity and dynamic adsorption of H2S, SO2 andtoluene were measured. Results show that at room temperature and atmospheric pressure, a thermal conductivity of 28.4 and 29.6 mW/m.K were obtained for the SNP mesoporous silicas. The dynamic adsorption behaviour of the chemisorbents and composites indicate their ability to absorbed H2S, SO2 andtoluene respectively. The highest H2S uptake corresponds to chemisorbents with 11.2-13.6 wt% KMnO4. The effect of impregnation route, amount of KMnO4 and its location in the pore system are likely the key factors in achieving a large H2S uptake. For SO2 adsorption, the highest uptake capacity was observed for MgCa-68/32-KOH. The results further suggest that the key to large SO2 uptake is as a result of the synergetic effect between large mesopore diameter and extensive mesopore volumes. Carbon-silica composites with carbon content 45 wt % exhibits high toluene adsorption with composite via route I having the highest toluene adsorption capacity (27.6 wt % relative to carbon content). The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1-30 nm) bimodal pore system consisting of extensive mesopore channels (2-30 nm) as well as large surface area. These capacity values of carbon-silica composites are competitive to results obtained for commercial coconut based carbon (31 wt %), and better than commercial alumina-carbon composite (9.5 wt %). / <p>QC 20130408</p>

Hydrothermal synthesis is a widely used technique for the preparation of fine particles. It can be carried out in batch or flow systems, although most studies have used batch reactors below 200 C. More recently, however, continuous hydrothermal synthesis has been employed in near- and supercritical water to obtain metal oxide particles. This technique offers tremendous promise for control of particle characteristics due to the rapidly changing properties of water with temperature and pressure in the critical region. However, the role of temperature in this process is not completely understood. Moreover, agglomeration of particles remains a problem in both batch and continuous hydrothermal techniques. This work is concerned with the use of continuous hydrothermal synthesis at near-critical and supercritical conditions to obtain iron oxide and lithium iron phosphate nanoparticles. Factors that affect size, size-distribution, and morphology of nanoparticles were investigated and the results have been used to resolve differences in the literature concerning the effect of temperature on particle size. It was shown that agglomeration can be minimized by using a protective polymer coating and this appears to be an effective method to control particle size. The continuous hydrothermal technique was also extended to materials other than metal oxides by synthesizing lithium iron phosphate. Differences in the particle sizes obtained using the batch and continuous methods were shown to be due to the different mechanisms of particle formation in the two techniques. Better particle characteristics (size, size distribution and morphology) were obtained using the continuous hydrothermal technique than using the batch hydrothermal method. Iron oxide nanoparticles were also deposited on the surface and in the pores of activated carbon pellets in a batch reactor in order to minimize agglomeration of particles. The resulting iron oxide activated carbon nanocomposites exhibited significant catalytic performance in the oxidation of propanal. Therefore, the use of supercritical water to deposit metal oxide particles on hydrophobic surfaces offers promise for carbon-supported catalyst preparation without the use of toxic or noxious solvents.

In this study production and characterization of activated carbon from an agricultural waste, pistachio-nut shells, was investigated. To determine optimum production conditions by chemical activation method, effect of tempreature (300, 500, 700 and 900 oC) and effect of impregnation ratio (1:1, 2:1 and 3:1 as activation agent:sample) were investigated by applying two different methods (raw material activation and char activation) and with two different activation agents (phosphoric acid and potassium hydroxide). To produce activated carbon, all the impregnated samples were heated to the final activation temperature under a continuous nitrogen flow (100 cm3/min) and at a heating rate of 10 oC/min and were held at that temperature for 1 hour. Pore structures of activated carbons were determined by N2 adsorption and micro-mesopore analysis was made by &ldquo / Non-local Density Functional Theory&rdquo / and &ldquo / Monte Carlo Simulation&rdquo / method (NLDFT-Monte Carlo Simulation Method). BET surface areas of produced activated carbons were found from N2 adsorption data in the relative pressure range of 0.01 to 0.15. BET surface areas of phosphoric acid activated carbons by raw material activation method were found between 880 and 1640 m2/g. The highest value of the BET surface area was obtained in the case of the activated carbon which was produced with an impregnation ratio of 3/1 (g H3PO4/g raw material), at an activation temperature of 500 oC. The repeatibility was also investigated on phosphoric acid activated carbons which were produced with conventional raw matererial activation method. Results showed that, both the BET surface area values and pore size distributions were consistent among themselves. On the other hand char activation experiments with phosphoric acid produced activated carbons having lower BET surface areas than the ones obtained with raw material activation method by creating mesoporous structure. When the same char activation method was tried with potassium hydroxide, it was concluded that elevated temperatures could help in producing activated carbons with high BET surface areas by creating microporous structure. Results also showed that properties of activated carbon such as ash content, slurry pH value, true density, elemental composition, methylene blue number and surface morphology were strongly affected by both production conditions and production method, as pore structure was affected considerably.

This study combined photocatalytic technology with activated carbon cellulose-paper filter (ACCF) adsorption to decompose gaseous pollutants. Gaseous pollutants were initially adsorbed by activated carbon and could be further decomposed by photocatalytic technology. This study selected acetone (CH3COCH3) as gaseous pollutants. Two market available photocatalysts (photocatalysts¢¹and¢º) were coated on ACCF by impregnation to decompose acetone in a batch photocatlytic reactor. Operating parameters investigated in this study included initial acetone concentration (4.1~10.2 £gM), reaction temperature (40~70¢J), and water vapor (0~20 %). The incident UV light of 365 nm was irradiated by a 20-watt low-pressure mercury lamp placing above the batch photocatalytic reactor. The ACCF coated with TiO2 was placed at the center of the photocatalytic reactor. Acetone was injected into the reactor by a gasket syringe to conduct the photocatalytic tests. Reactants and products were analyzed quantitatively by a gas chromatography with an electron capture detector (GC/DCD) and a flame ionization detector followed by a methaneizer (GC/FID-Methaneizer). Finally, a Langmiur-Hinshewood (L-H) kinetic model was proposed to describe the rate of photocatalytic reaction. Results obtained from the photocatalytic tests indicated that photocatalyst¢º was better than photocatalyst¢¹ for the decomposition of acetone. Experimental results indicated that the size range of self-produced TiO2 photocatalyst by sol-gel was 20~70 nm. The end products were mainly CO and CO2, which resulted in the mineralization ratio up to 98%. Results obtained from the operating parameter tests revealed that the increase of initial acetone concentration enhanced the amount of acetone adsorbed on ACCF, which however did not increase the reaction rate of acetone. Although the increase of reaction temperature could reduce the amount of acetone adsorbed on ACCF, the decomposition rate of acetone could be promoted, so as the yield rate and mineralization ratio of products (CO and CO2). The increase of water vapor could slightly decrease the amount of acetone adsorbed on ACCF. The competitive adsorption phenomenon between acetone and water molecules on active sites could decelerate the decomposion of acetone. Moreover, the ACCF would not be saturated since the adsorbed acetone could be further decomposed quickly by the photocatalysts, which made the TiO2/ACCF more effective on removing acetone and lasted longer than the conventional ACCF. Finally, a modified bimolecular Langmuir-Hinshelwood kinetic model was developed to investigate the influences of initial acetone concentration reaction, temperature, and relative humidity on the promotion and inhibition for the photocatalytic oxidation of acetone. The modified L-H kinetic model could successfully simulate the photocatalytic reaction rate of acetone. Thus, the reaction rate of acetone over TiO2/ACCF could be described by the modified L-H kinetic model.

En aquesta tesi, proposem la fabricació y la caracterització d’un microconcentrador de gasos, per ser acoblat amb un microsistema de detecció, per millorar el seu límit de detecció davant els gasos tòxics. Aquest estudi s’aplica especialment al benzè, que es un compost d’alta cancerigenitat. El preconcentrador proposat esta basat en estructura plana, que, es una opció de fabricació més simple y permet una millor aïllament tèrmic amb el resta d’unitats del microsistema, qu’els estructures 3D proposats a la literatura. No obstant, els factors de concentració obtinguts amb l’estructura plana queden generalment més baixos, per causa de la menor quantitat de material absorbent que pot acollir. En aquesta tesis, es va superar aquest problema mitjançant l’utilització del carboní actiu, un adsorbent d’alta capacitat d’adsorció, així com l’optimització de les condicions de funcionament del dispositiu. Finalment, acoblant el microconcentrador amb un micro-cromatògraf, vam aconseguir una detecció sensible y selectiva del benzè en barreja amb altres volàtils a l’aire. / The present thesis focuses on the fabrication and characterization of a gas microconcentrator for to be coupled with a detection microsystem, in order to lower its detection limit towards toxic gases and vapours in contaminated areas. This study was more especially applied to the preconcentration of benzene, a cancerigenic compound at low ppb level. A preconcentrator based on a planar structure was proposed regarding its simpler fabrication, better thermal insulation and lower power consumption, compared to the 3D structures proposed conventionally in literature. In order to obtain higher concentration factors with such structure, its small size was compensated by using a high adsorption capacity adsorbent such as activated carbon as well as the optimization of the preconcentration conditions of the device. Finally, the microconcentrator was validated as injection unit when coupled with a microchromatographic system, where a sensitive and selective analysis of benzene in mixture with other VOCs was achieved.