Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-12-29T16:22:07Z No. of bitstreams: 1 LidianeAlvesDeMorais_TESE.pdf: 2444711 bytes, checksum: 23f2b53145f8389d4a45f7f7c2040146 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-02T17:55:19Z (GMT) No. of bitstreams: 1 LidianeAlvesDeMorais_TESE.pdf: 2444711 bytes, checksum: 23f2b53145f8389d4a45f7f7c2040146 (MD5) / Made available in DSpace on 2017-01-02T17:55:19Z (GMT). No. of bitstreams: 1 LidianeAlvesDeMorais_TESE.pdf: 2444711 bytes, checksum: 23f2b53145f8389d4a45f7f7c2040146 (MD5) Previous issue date: 2016-05-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Um dos materiais que atualmente est? em destaque s?o os compostos de ni?bio, por apresentarem caracter?sticas como acidez, propriedades oxidativas e fotocatal?ticas e por ser um dos metais mais abundantes do pa?s, sendo o Brasil o maior produtor mundial. Este trabalho avaliou a efici?ncia da fotocat?lise heterog?nea de materiais de ni?bio na oxida??o de metanol e na inativa??o do microrganismo Escherichia Coli. Foram sintetizados catalisadores a base de ni?bio Nb2O5 e foram feitas imobiliza??es (coating) utilizando ?xido de ni?bio. Diante das caracteriza??es, foi poss?vel verificar a forma??o de esp?cies de ?xido de ni?bio e niobatos de s?dio dependendo da metodologia de s?ntese adotada. Esses materiais foram avaliados na oxida??o de metanol em diferentes concentra??es de catalisadores e apresentaram uma efici?ncia na forma??o do formalde?do proveniente da oxida??o, esta efici?ncia est? diretamente relacionada com a concentra??o dos catalisadores, sendo o material de niobato de s?dio o que apresentou maior efici?ncia, devido as suas propriedades texturais, ?pticas, sendo este um material promissor no ramo da fotocat?lise. Para os sistemas de imobiliza??o (coating), verificou-se que o revestimento ideal ? obtido com tr?s imobiliza??es, estes materiais foram analisados na oxida??o de metanol e na inativa??o de microrganismo Escherichia Coli. Estes sistemas (coating) mostram uma boa atividade na oxida??o de metanol, apesar de apresentar resultados inferiores quando comparados aos materiais em suspens?o de ?xido de ni?bio, por?m a grande vantagem dos sistemas imobilizados em rela??o ao de suspens?es s?o a sua reutiliza??o. Em rela??o ? inativa??o da Escherichia Coli, foi verificado que os sistemas imobilizados n?o s?o muitos ativos e que o microrganismo ? bastante dependendo do meio em que se encontra. / One of the materials that is currently highlighted are the compounds of niobium, because they have features like acidity, oxidative and photocatalytic properties and for being one of the most abundant metals in the country, Brazil is the world's largest producer. In this scenario, the work has to evaluate the efficiency of heterogeneous photocatalysis niobium materials in the oxidation of methanol and the inactivation of Escherichia coli using immobilization systems ?coating? and suspension. Commercial niobium oxide (Nb2O5) was evaluated in suspension and immobilization in different systems (tubes and rings) for photocatalytic processes for water treatment (methanol oxidation and inactivation of Escherichia coli). From the results of the commercial Nb2O5 characterizations was observed the presence of an amorphous structure with heat thermal treatment at temperatures above 550 ?C becomes crystalline phases, however, this fact produce a significant aggregation of the particles which reduced the specific area and the photocatalytic activity. The not calcined Nb2O5 material showed a higher activity, for both oxidation of methanol as for the inactivation of bacterial tests, the latter being very sensitive to the chemical composition water. Immobilization of the photocatalyst reactor walls prevents the need for removal of Nb2O5 particles after treatment, but significantly reduction its activity. In contrast, immobilization in a fixed-bed (rings) led to a moderate reduction in activity, which is counteracted by improvement in the long-term stability of the material. Niobium catalysts were synthesized using a refluxing method with and without the use of NaOH in different conditions of synthesis and characterized by different techniques in order to verify the phase formation of niobium. From the results of X-ray diffraction for the synthesized materials were recorded forming of species niobium oxide and sodium niobates depending on the adopted synthesis methodology. The catalytic activity of these materials was evaluated in the oxidation of methanol in relation to the amount of catalyst in which the activities have different behaviors have been dependent on the structure, surface and morphological parameters. Materials with sodium niobate structure have a lineal tendency of activity in relation to the mass of catalysts, while the materials niobium oxide structure have an abrupt loss of their catalytic activity at higher catalyst concentrations, indicating that the dispersion of the light is higher in these catalysts as increases the amount of particles in suspension. Among the materials synthesized and analyzed in the oxidation of methanol, which was more efficient, was the material of sodium niobate NaNbO3 to their textural properties, optical, which is a promising material for photocatalysis.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-12T13:44:02Z No. of bitstreams: 1 AmisonRickLopesDaSilva_DISSERT.pdf: 3032672 bytes, checksum: 3706691ab11516af6b2311a9f7d98456 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-16T16:12:13Z (GMT) No. of bitstreams: 1 AmisonRickLopesDaSilva_DISSERT.pdf: 3032672 bytes, checksum: 3706691ab11516af6b2311a9f7d98456 (MD5) / Made available in DSpace on 2017-01-16T16:12:13Z (GMT). No. of bitstreams: 1 AmisonRickLopesDaSilva_DISSERT.pdf: 3032672 bytes, checksum: 3706691ab11516af6b2311a9f7d98456 (MD5) Previous issue date: 2016-07-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A oxida??o eletroqu?mica ? um tipo de processo que pode ocorrer diretamente no ?nodo, a partir de uma transfer?ncia direta com a superf?cie, ou tamb?m atrav?s de uma oxida??o indireta mediante a gera??o de esp?cies ativas de oxig?nio as quais podem ser fisicamente adsorvidas (na forma de radicais hidroxila (?OH), ou quimicamente adsorvidas (oxig?nio se apresenta em estrutura de ?xido), na superf?cie do eletrodo. Esse processo est? relacionado ao tipo do material an?dico utilizado e a sua atividade eletrocatal?tica. Por?m, essa atividade pode ser tamb?m, prejudicada devido ? forma??o de filmes polim?ricos, rea??es paralelas de produ??o de oxidantes bem como, a rea??o de evolu??o de oxig?nio. Dentre os materiais eletrocatal?ticos mais estudados encontra-se os filmes de diamante dopado com boro (DDB). O eletrodo de DDB possui excelentes propriedades tais como estabilidade eletroqu?mica a elevadas densidades de correntes, estabilidade a corros?o, superf?cie inerte com baixas propriedades de adsor??o e dureza. A alta efici?ncia do DDB para remo??o dos compostos org?nicos ? atribu?da ? capacidade de produzir uma grande quantidade de radicais hidroxilas mediante a eletr?lise da ?gua. Estes radicais apresentam alta reatividade com os compostos org?nicos, devido ? sua fraca intera??o (fracamente adsorvido) com o filme de DDB s?o tamb?m, n?o seletivos e mineralizam completamente poluentes org?nicos com uma alta efici?ncia de corrente. Entretanto, alguns compostos org?nicos s?o de f?cil degrada??o em rela??o a outros, bem como, alguns compostos org?nicos tamb?m interagem com a superf?cie do DDB. Assim, devido ? necessidade de entender o processo qu?mico em escala molecular, a inclus?o de estudos te?ricos computacionais esta sendo de maior interesse, na qual s?o desenvolvidos c?lculos f?sico-qu?micos advindos da qu?mica qu?ntica, utilizando a Teoria do Funcional da Densidade (DFT). A DFT trata sistemas com muitos el?trons usando fun??es que representam a densidade eletr?nica das mol?culas a fim de se obter: propriedades eletr?nicas, cargas at?micas e energias dos intermedi?rios que comp?e a superf?cie de energia potencial de uma rea??o qu?mica, avaliar a estabilidade de modo comparativo entre compostos e entender os mecanismos de rea??o seguidos e propostos. Assim, o objetivo deste trabalho foi o uso de DDB para o estudo do comportamento eletroqu?mico de compostos org?nicos (hidroquinona, catecol, resorcinol, ?cido ac?tico, ?cido f?rmico e ?cido ox?lico) bem como o entendimento do processo de degrada??o, dos mesmos quando eletrolisados. Al?m disso, estudos computacionais referentes ao comportamento das esp?cies qu?micas frente ao eletrodo de DDB com a inten??o de obter as configura??es de intera??o do composto org?nico na superf?cie do eletrodo ou no entendimento de desvendar as intera??es entre as esp?cies oxidantes fortes em solu??o com os compostos org?nicos durante sua degrada??o. / The Electrochemical Oxidation is a kind of process that can occur directly at the anode from a direct transfer to the surface, or also by means of indirect oxidation by the generation of active oxygen species which can be physically adsorbed (in form of hydroxyl radical (? OH)), or chemically adsorbed (oxygen is present in oxide structure) on the electrode surface. this process is related to the type of anode material used and its electrocatalytic activity. However, this activity can also be impaired due to the formation of polymeric films, production of parallel oxidant reactions as well reaction of oxygen evolution. Among the most studied electrocatalytic material is diamond films doped with boron (BDD). the BDD electrode has excellent electrochemical properties such as stability at high current densities, corrosion stability, inert surface with low adsorption properties, and hardness. The high efficiency of the BDD for removal of organic compounds is attributed to their ability to produce a large amount of hydroxyl radicals by the electrolysis of water. These radicals have high reactivity with organic compounds, due to their weak interaction (weakly adsorbed) with the film BDD, they are also not selective and completely mineralize organic pollutants with a high current efficiency. However, some organic compounds are easy to degradation than others, as well as certain organic compounds also interact with the surface of BDD. Thus, because of the need to understand the chemical process at the molecular level, including computational theoretical studies that are of most interest, which are developed physico-chemical calculations arising from quantum chemistry, using Density Functional Theory (DFT). The DFT is systems with many electrons using functions representing the electron density of molecules in order to obtain electronic, atomic charges and derivatives of energy the potential energy surface of a chemical reaction, to evaluate the stability of the compounds and understand the reaction mechanisms followed and proposed. The objective of this work was the use of BDD to study the electrochemical behavior of organic compounds (hydroquinone, catechol, resorcinol, acetic acid, formic acid and oxalic acid) as well as the understanding of the degradation process of the same when in electrolysis. Moreover, computational studies on the behavior of chemical species across the BDD electrode with the intention of obtaining the organic compound interaction settings on the surface of the electrode or the understanding to unravel the interactions between strong oxidizing species in solution with organic compounds during its degradation.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-02-02T11:57:41Z No. of bitstreams: 1 MarcellaJordannaSilvaMontorilAraujo_DISSERT.pdf: 3443985 bytes, checksum: 367c6ae398c4c1ef8054fbb595d56752 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-02-06T20:29:13Z (GMT) No. of bitstreams: 1 MarcellaJordannaSilvaMontorilAraujo_DISSERT.pdf: 3443985 bytes, checksum: 367c6ae398c4c1ef8054fbb595d56752 (MD5) / Made available in DSpace on 2017-02-06T20:29:13Z (GMT). No. of bitstreams: 1 MarcellaJordannaSilvaMontorilAraujo_DISSERT.pdf: 3443985 bytes, checksum: 367c6ae398c4c1ef8054fbb595d56752 (MD5) Previous issue date: 2016-07-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A ind?stria t?xtil gera um grande volume de efluentes que, muitas vezes, s?o descartados no meio ambiente sem estarem devidamente tratados. Esses efluentes s?o formados de mol?culas org?nicas e caracterizam-se por apresentar cor, que alteram as propriedades da ?gua deixando-a impr?pria para o consumo. Para o tratamento desses efluentes, a utiliza??o de processos catal?ticos heterog?neos de custo baixo pode ser vantajoso. As argilas v?m sendo bastante estudadas como suportes catal?ticos em raz?o de sua abund?ncia na crosta terrestre e seu baixo custo. Portanto, neste trabalho as argilas vermiculita e bentonita foram usadas como suporte para o catalisador oxihidr?xido de ni?bio e pelo m?todo de deposi??o-precipita??o foram obtidos comp?sitos formados por esses materiais. Os comp?sitos Nb/argila foram caracterizados e as principais t?cnicas mostraram que ocorreu uma modifica??o em cada argila. Os resultados de difratrometria de raios X (DRX) indicaram que ocorreu uma diminui??o da intensidade da reflex?o e um deslocamento do pico principal de ambas as argilas quando o oxihidr?xido de ni?bio ? adicionado na estrutura. As an?lises de espectroscopia na regi?o do infravermelho mostram bandas de adsor??o de ambos os materiais nos comp?sitos Nb/argila, dando a indicativa de que o comp?sito foi realmente formado. As imagens de microscopia eletr?nica de varredura tamb?m confirmaram essa modifica??o de estrutura. Foram realizados testes de oxida??o e oxida??o fotocatal?tica com os comp?sitos obtidos e o teste de oxida??o fotocatal?tica foi o que apresentou melhores resultados, pois o comp?sito de vermiculita (Nb/V0) apresentou uma maior atividade fotocatal?tica removendo 98% da cor do corante alaranjado de metila em 90 minutos de rea??o enquanto que o material comp?sito de bentonita (Nb/B0) removeu apenas 63% durante o mesmo tempo de rea??o. Essa atividade ? devido o comp?sito Nb/V0 ter apresentado um menor valor de band gap (3,08eV) que o comp?sito Nb/B0 (3,33eV). / The textile industry produces a large volume of waste that often is discarded into the environment without being properly treated. These effluents are made of organic molecules and are characterized by their color that alter the properties of water which leave it unfit for consumption. For the treatment of these effluents, the use of heterogeneous catalytic processes of low cost can be advantageous. Clays have been widely studied as catalyst supports because of their abundance in the Earth's crust and its low cost. Therefore, in this study the clays vermiculite and bentonite were used as support for the catalyst oxyhydroxide niobium and by the method of deposition-precipitation it was obtained composites formed from these materials. The composite Nb/clay were characterized and the main techniques showed that was changes in each clay. The results X-ray diffractometer (XRD) showed that there was a decrease in reflection intensity and a shift of the main peak of both clays when oxyhydroxide niobium is added to the structure. The spectroscopic analyzes show infrared adsorption bands of in both materials composite Nb/clay which indicates that the composite was actually formed. The scanning electron microscopy images also confirmed that structure modification. Oxidation and photocatalytic oxidation tests were performed with the obtained composite and photocatalytic oxidation test showed the best results, because the vermiculite composite (Nb/V0) showed higher photocatalytic activity by removing 98% of the color orange dye methyl in 90 minutes of reaction while the composite material of bentonite (Nb/B0) removed only 63% over the same reaction time. This activity is due to the composite Nb/V0 have presented a smaller value of band gap (3,08eV) than the composite Nb/B0 (3,33eV).

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-02-13T19:11:34Z No. of bitstreams: 1 JoseEudesLimaSantos_DISSERT.pdf: 3350275 bytes, checksum: 443cfc73179e127026de513be3703670 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-02-14T00:17:28Z (GMT) No. of bitstreams: 1 JoseEudesLimaSantos_DISSERT.pdf: 3350275 bytes, checksum: 443cfc73179e127026de513be3703670 (MD5) / Made available in DSpace on 2017-02-14T00:17:28Z (GMT). No. of bitstreams: 1 JoseEudesLimaSantos_DISSERT.pdf: 3350275 bytes, checksum: 443cfc73179e127026de513be3703670 (MD5) Previous issue date: 2016-07-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Este trabalho teve como objetivo sintetizar o eletrodo Ti/TiO2-nanotubos/PbO2 por anodiza??o eletroqu?mica e eletrodeposi??o, investigar a produ??o de esp?cies oxidantes fortes e degrada??o eletroqu?mica do corante t?xtil sint?tico Vermelho ?cido 1. Para tanto, os nanotubos de TiO2 foram produzidos por anodiza??o eletroqu?mica em eletr?lito misto org?nico-inorg?nico, calcinados e, ent?o, decorados com PbO2 por eletrodeposi??o. Os nanotubos de TiO2 decorados com PbO2 foram caracterizados pelas t?cnicas de Microscopia Eletr?nica de Varredura, Difra??o de Raios X e por medidas potenciodin?micas. A determina??o de esp?cies oxidantes fortes foi realizada pelo m?todo ISCO (persulfato) e rea??o de aprisionamento de spin por RNO (radical hidroxila). A eletr?lise galvanost?tica da amostra sint?tica contendo o corante AR1 nos ?nodos Ti/Pt e Ti/TiO2-nanotubos/PbO2 foi monitorada por espectrometria de UV-vis?vel e demanda qu?mica de oxig?nio. Foi verificado que o eletrodo Ti/TiO2-nanotubos/PbO2 tem alto sobrepotencial para a rea??o de evolu??o de oxig?nio sendo um eletrocatalisador ruim para essa rea??o. Al?m disso, uma produ??o significante de radicais hidroxila e persulfato ? alcan?ada em Ti/TiO2-nanotubos/PbO2 quando comparado a Ti/Pt principalmente em densidade de corrente de 60 mA cm-2. Ele tamb?m mostrou melhor desempenho na remo??o do AR1 com descolora??o total do mesmo em 90 min e decaimento da demanda qu?mica de oxig?nio em 64% na densidade de 60 mA cm-2 e maior efici?ncia energ?tica em ambas as densidades de corrente de 7,5 e 60 mA cm-2 frente o eletrodo de Ti/Pt. Portanto, o eletrodo de Ti/TiO2-nanotubos/PbO2 exibe boas propriedades catal?ticas para aplica??es ambientais, tal como oxida??o an?dica. Al?m disso, a concentra??o dos oxidantes foi dependente do material do eletrodo e das condi??es de oxida??o an?dica. / This study aimed to synthesize the Ti/TiO2-nanotube/PbO2 electrode by anodizing electrochemistry and electroplating, investigate the production of strong oxidizing species and electrochemical degradation of synthetic textile dye Acid Red 1. Therefore, the TiO2 nanotubes were produced by anodizing electrochemistry in organic-inorganic mixed electrolyte, calcined and then decorated with PbO2 by electrodeposition. TiO2 nanotubes decorated with PbO2 were characterized by electron microscopy Scan, X-Ray Diffraction techniques and potentiodynamic measurements. The determination of strong oxidizing species was performed by ISCO method (persulfate) and spin trapping reaction by RNO (hydroxyl radical). The galvanostatic electrolysis of synthetic sample containing the dye AR1 in anodes Ti/Pt and Ti/TiO2-nanotube/PbO2 was monitored by UV-visible spectrometry and chemical oxygen demand. It was found that the Ti/TiO2-nanotube/PbO2 electrode has a high overpotential for the reaction of oxygen evolution is a bad electrocatalyst for this reaction. Furthermore, a significant production of hydroxyl radicals and persulfate is achieved in Ti/TiO2-nanotube/PbO2 compared to Ti/Pt mainly current density of 60 mA cm-2. It also showed better performance in the removal of AR1 complete discoloration with the same 90 min and decay of chemical oxygen demand by 64% the density of 60 mA cm-2 and greater efficiency in both current densities of 7.5 and 60 mA cm-2 across the electrode Ti/Pt. Therefore, the electrode Ti/TiO2-nanotube/PbO2 exhibits good catalytic properties for environmental applications, such as anodic oxidation. Furthermore, the concentration of the oxidizing electrode was dependent on the material and the anodic oxidation conditions.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-02-20T22:36:45Z No. of bitstreams: 1 MichellSmithGomesDaSilva_DISSERT.pdf: 497467 bytes, checksum: 682d0d320bb5da2124c9690a67fc0e26 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-02-23T23:07:42Z (GMT) No. of bitstreams: 1 MichellSmithGomesDaSilva_DISSERT.pdf: 497467 bytes, checksum: 682d0d320bb5da2124c9690a67fc0e26 (MD5) / Made available in DSpace on 2017-02-23T23:07:42Z (GMT). No. of bitstreams: 1 MichellSmithGomesDaSilva_DISSERT.pdf: 497467 bytes, checksum: 682d0d320bb5da2124c9690a67fc0e26 (MD5) Previous issue date: 2016-08-02 / ?guas com turbidez e cor aparente baixas a moderadas s?o eventualmente desafiadoras para tratar, principalmente em Esta??es de Tratamentos de ?gua (ETAs) de ciclo completo com clarifica??o por decanta??o (ETAs ?convencionais?). Esse tipo de ?gua pode ser coagulada no mecanismo de varredura, geralmente com dose de coagulante elevada, a fim de produzir flocos sediment?veis que sejam removidos no decantador. Contudo a coagula??o no mecanismo de adsor??o e neutraliza??o de cargas ? vantajosa, com dose usualmente mais baixa, sendo que, nesse caso, haver? apenas a desestabiliza??o das part?culas e a forma??o de flocos muito pequenos (n?o sediment?veis) que ser?o removidos nos filtros. Em alguns casos a ETA possibilita o by-pass da ?gua diretamente para os filtros (com ou sem pr?-flocula??o), pois as unidades de decanta??o praticamente perdem sua fun??o e a ETA, embora fisicamente seja configurada como de ciclo completo, opera como um sistema de filtra??o direta. Apesar das vantagens desta configura??o, ? geralmente mais dif?cil para o operador encontrar a dose e pH adequados para coagula??o no mecanismo de adsor??o e neutraliza??o de cargas. O objetivo deste trabalho foi adequar uma ETA com tais caracter?sticas. Fizemos ensaios em jarteste simulando a tecnologia de ciclo completo e de filtra??o direta descendente, e tratamentos como pr?-oxida??o, coagula??o, pr?-oxida??o com coagula??o e adsor??o com coagula??o, variando as doses dos respectivos produtos em cada tratamento e em pH diferentes. Todos os tratamentos realizados atenderam a Portaria 2.914/11 para cor aparente, por?m somente os tratamentos em que houve a coagula??o atenderam para turbidez e cor aparente simultaneamente, sendo os melhores resultados do tratamento de pr?-oxida??o com coagula??o. / Water with turbidity and color apparent low to moderate are sometimes challenging to treat, especially in Water Treatment Plants (WTP) of full cycle with clarification by decantation (WTPs "conventional") because should be coagulated preferably in adsorption-neutralization mechanism loads. Such water can be coagulated in the sweep mechanism, generally with a high dose of coagulant, to produce settleable flocs which are removed in the decanter. However, it is also possible, in an advantageous overall, making the water coagulation at adsorption and charge neutralization mechanism with usually lower dose, and in this case there will be only a destabilization of the particles and formation of tiny floc (not settleable) to be removed on the filters. In some cases WTP enables the bypass of water directly to the filter (with or without pre-flocculation), since the decantion units practically lost its function and ETA, although it is physically configured as a complete cycle, it operates as a direct filtration system. Despite the advantages of this configuration, it is generally more difficult for the operator to find the dose and pH suitables for the adsorption and charge neutralization mechanism. The objective was to adapt a WTP with such characteristics. We did jartest tests simulating the complete cycle and downstream direct filtration, and treatments as pre-oxidation, coagulation, preoxidation with coagulation and adsorption coagulation, varying dosages of the respective products in each treatment and at different pH. All treatments performed attended Ordinance 2.914/11 for apparent color, but only the treatments in which there was coagulation attended for turbidity and apparent color simultaneously, and the best results of treatment of pre-oxidation with coagulation.

Made available in DSpace on 2014-12-17T15:42:00Z (GMT). No. of bitstreams: 1 Mariele ISM_DISSERT.pdf: 4704397 bytes, checksum: 9fa1538bc3d6948d492f9a6c378eaf62 (MD5) Previous issue date: 2012-07-20 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The oxidative desulfurization process (ODS) of a commercial diesel fuel was performed under mild conditions in the presence of catalysts based on vanadium or manganese, supported on alumina, clays (commercial, natural and pillared) and zeolites (NaX, NaY, beta, mordenite and ZSM-5). The catalysts were synthesized by wet impregnation and characterized by X-ray diffraction, textural analysis by N2 adsorption and scanning electron microscopy. The dibenzothiophene (DBT) was used as sulfur compound in catalytic evaluation. The reactions were performed using acetonitrile as solvent and the hydrogen peroxide as oxidant at 55?C. The reaction products were analized by gas chromatography (GC-FID). In the studied conditions, the process was efficient due to the DBT was converted to its corresponding sulfone. Both DBT and corresponding sulfone were extracted by the solvent. Removals and oxidations up to 100% of sulfur compound were achieved. The catalysts supported on ZSM-5 zeolite showed are more effective for oxidation reaction of sulfur compound, presenting the best results. It was observed for oxidation reaction, that vanadium catalysts were more effective and manganese catalysts showed best results for removal of sulfur compounds / O processo de Dessulfuriza??o Oxidativa (ODS) de um diesel comercial foi realizado em condi??es suaves na presen?a de catalisadores ? base de van?dio ou mangan?s, suportados em aluminas, argilas (comerciais, naturais e pilarizadas) e ze?litas (NaX, NaY, beta, mordenita, ZSM-5). Os catalisadores foram sintetizados via impregna??o ?mida e caracterizados por difra??o de raios-X, an?lise textural por adsor??o e dessor??o de nitrog?nio e microscopia eletr?nica de varredura. O dibenzotiofeno (DBT) foi utilizado como o composto de enxofre nos testes catal?ticos. As rea??es foram realizadas usando como solvente acetonitrila e como oxidante o per?xido de hidrog?nio a temperatura de 55?C. Os produtos de rea??o foram analisados por cromatografia gasosa (CG-FID). Nas condi??es estudadas o processo mostrouse eficiente, o DBT foi convertido para sua respectiva sulfona. Ambos DBT e a sulfona foram extra?dos pelo solvente. Remo??es e oxida??es de 100% do composto de enxofre foram alcan?adas. Os catalisadores suportados na ze?lita ZSM-5 mostraram-se mais efetivos para a rea??o de oxida??o do composto sulfurado, apresentando os melhores resultados. Observa-se para a rea??o de oxida??o que os catalisadores de van?dio foram mais efetivos, e os catalisadores de mangan?s apresentaram melhores resultados na extra??o dos compostos sulfurados

Made available in DSpace on 2014-12-17T14:06:57Z (GMT). No. of bitstreams: 1 SamuelNC_DISSERT.pdf: 3182728 bytes, checksum: 8bfe4bb2137c514846453d3aeb267c09 (MD5) Previous issue date: 2012-05-11 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / It seeks to find an alternative to the current tantalum electrolytic capacitors in the market due to its high cost. Niobium is a potential substitute, since both belong to the same group of the periodic table and because of this have many similar physical and chemical properties. Niobium has several technologically important applications, and Brazil has the largest reserves, around 96%. There are including niobium in reserves of tantalite and columbite in Rio Grande do Norte. These electrolytic capacitors have high capacitance specifies, ie they can store high energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor because is growing demand in the production of capacitors with capacitance specifies increasingly high, this because of the miniaturization of various devices such as GPS devices, televisions, computers, phones and many others. The production route of the capacitor was made by powder metallurgy. The initial niobium powder supplied by EEL-USP was first characterized by XRD, SEM, XRF and laser particle size, to then be sieved into three particle size, 200, 400 e 635mesh. The powders were then compacted and sintered at 1350, 1450 and 1550?C using two sintering time 30 and 60min. Sintering is one of the most important parts of the process as it affects properties as porosity and surface cleaning of the samples, which greatly affected the quality of the capacitor. The sintered samples then underwent a process of anodic oxidation, which created a thin film of niobium pent?xido over the whole porous surface of the sample, this film is the dielectric capacitor. The oxidation process variables influence the performance of the film and therefore the capacitor. The samples were characterized by electrical measurements of capacitance, loss factor, ESR, relative density, porosity and surface area. After the characterizations was made an annealing in air ate 260?C for 60min. After this treatment were made again the electrical measurements. The particle size of powders and sintering affected the porosity and in turn the specific area of the samples. The larger de area of the capacitor, greater is the capacitance. The powder showed the highest capacitance was with the smallest particle size. Higher temperatures and times of sintering caused samples with smaller surface area, but on the other hand the cleaning surface impurities was higher for this cases. So a balance must be made between the gain that is achieved with the cleaning of impurities and the loss with the decreased in specific area. The best results were obtained for the temperature of 1450?C/60min. The influence of annealing on the loss factor and ESR did not follow a well-defined pattern, because their values increased in some cases and decreased in others. The most interesting results due to heat treatment were with respect to capacitance, which showed an increase for all samples after treatment / Procura-se encontrar uma alternativa para os atuais capacitores eletrol?ticos de t?ntalo existentes no mercado, devido ao seu alto custo. O ni?bio ? um substituto em potencial, pois ambos pertencem ao mesmo grupo da tabela peri?dica e devido a isso t?m v?rias propriedades f?sicas e qu?micas semelhantes. O ni?bio apresenta diversas aplica??es tecnologicamente importantes e o Brasil possui as maiores reservas mundiais, em torno de 96%. Existe inclusive ni?bio contido em reservas de tantalita e columbita no Rio Grande do Norte. Esses capacitores eletrol?ticos possuem alta capacit?ncia especifica, ou seja, podem armazenar altas energias em volumes pequenos comparados a outros tipos de capacitores. Esse ? o principal atrativo desse tipo de capacitores, pois existe uma crescente demanda na produ??o de capacitores com capacit?ncia especifica cada vez mais alta, isso devido ? miniaturiza??o de diversos aparelhos como GPSs, televisores, computadores, celulares e muitos outros. A rota de produ??o do capacitor foi feita atrav?s da metalurgia do p?. O p? de ni?bio inicial fornecido pela EEL-USP foi primeiramente caracterizado atrav?s de DRX, MEV, granulometria a laser e FRX, para ent?o ser peneirado em tr?s granulometrias, 200, 400 e 635mesh. Os p?s foram ent?o compactados e sinterizados em 1350, 1450 e 1550?C usando dois patamares, 30 e 60min. A sinteriza??o ? uma das partes mais importantes do processo, pois afeta propriedades como porosidade e limpeza superficial das amostras, que afetaram grandemente a qualidade do capacitor. As amostras sinterizadas sofreram ent?o um processo de oxida??o an?dica, que criou um filme fino de pent?xido de ni?bio sobre toda a superf?cie porosa da amostra, este filme ? o diel?trico do capacitor. As vari?veis do processo de oxida??o influenciaram no desempenho do filme e conseq?entemente do capacitor. As amostras foram caracterizadas atrav?s de medidas el?tricas de capacit?ncia, fator de perdas, ESR, densidade relativa, porosidade e ?rea superficial. Ap?s as caracteriza??es foi feito um tratamento t?rmico de recozimento em atmosfera de ar a 260?C por 60min. Ap?s esse tratamento foram feitas novamente as medidas el?tricas. A granulometria do p? e a sinteriza??o afetaram a porosidade e por sua vez a ?rea especifica das amostras. Quanto maior a ?rea do capacitor, maior sua capacit?ncia. O p? que apresentou capacit?ncia mais alta foi o com menor granulometria. Temperaturas e tempos de sinteriza??o maiores causaram amostras com ?rea superficial menores, por?m, por outro lado a limpeza superficial de impurezas foi maior para esses casos, de maneira que deve ser feito um balanceamento entre o ganho que se obt?m com a limpeza das impurezas e a perda com a diminui??o da ?rea especifica. Os melhores resultados foram obtidos para a temperatura de 1450?C/60min. A influ?ncia do tratamento t?rmico de recozimento no fator de perdas e na ESR n?o seguiu um padr?o bem definido, pois seus valores aumentaram em alguns casos e diminu?ram em outros. Os resultados mais interessantes devido ao tratamento t?rmico foram com rela??o ? capacit?ncia, que apresentou um aumento para todas as amostras ap?s o tratamento

Made available in DSpace on 2014-12-17T14:13:53Z (GMT). No. of bitstreams: 1 MarcoAMS_TESE.pdf: 4598195 bytes, checksum: 64f542a86c9a48f91e63fe82fc791428 (MD5) Previous issue date: 2013-10-08 / Recent years have seen a significant growth in surface modifications in titanium implants, resulting in shorter healing times in regions with low bone density. Among the different techniques, subtraction by chemical agents to increase oxidation has been applied for surface treatment of dental implants. However, this technique is generally unable to remove undesirable oxides, formed spontaneously during machining of titanium parts, raising costs due to additional decontamination stages. In order to solve this problem, the present study used plasma as an energy source to both remove these oxides and oxidize the titanium surface. In this respect, Ti disks were treated by hollow cathode discharge, using a variable DC power supply and vacuum system. Samples were previously submitted to a cleaning process using an atmosphere of Ar, H2 and a mixture of both, for 20 and 60 min. The most efficient cleaning condition was used for oxidation in a mixture of argon (60%) and oxygen (40%) until reaching a pressure of 2.2 mbar for 60 min at 500?C. Surfaces were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), adhesion and cell proliferation. SEM showed less cell spreading and a larger number of projections orfilopodia in the treated samples compared to the control sample. AFM revealed surface defects in the treated samples, with varied geometry between peaks and valleys. Biological assays showed no significant difference in cell adhesion between treated surfaces and the control. With respect to cell proliferation, the treated surface exhibited improved performance when compared to the control sample. We concluded that the process was efficient in removing primary oxides as well as in oxidizing titanium surfaces / Nos ?ltimos anos, tem-se observado um crescimento nas modifica??es superficiais em implantes de tit?nio, que abrevia o tempo de cicatriza??o em regi?es com baixa densidade ?ssea. Dentre as diferentes t?cnicas, a de subtra??o por agentes qu?micos para aumentar a oxida??o vem sendo aplicada para tratamentos superficiais de implantes dentais. Por?m esta t?cnica geralmente n?o propicia a remo??o dos ?xidos indesej?veis formados espontaneamente durante a usinagem de pe?as de tit?nio, aumentando assim o custo, por exigir etapas adicionais para a descontamina??o. Com o objetivo de solucionar esse problema, utilizou-se neste trabalho o plasma como fonte energ?tica, tanto na remo??o desses ?xidos quanto como na oxida??o de superf?cie de tit?nio. Neste sentido, discos de Ti foram tratados em descarga por c?todo oco, usando-se uma fonte de tens?o DC vari?vel e sistema de v?cuo. Previamente, as amostras foram submetidas a processo de limpeza, utilizando-se atmosfera de Ar, H2 e mistura, em tempos de 20 e 60 min. A condi??o de limpeza mais eficaz foi utilizada para a oxida??o, numa mistura de arg?nio (60%) e oxig?nio (40%), at? atingir a press?o de 2,2 mbar durante 60 min, a 500?C. As superf?cies foram caracterizadas por microscopia eletr?nica de varredura (MEV), difra??o de raios X (DRX), microscopia por for?a at?mica (AFM), ades?o e prolifera??o celular. Na microscopia eletr?nica de varredura (MEV), observou-se um menor espraiamento celular e uma maior quantidade de proje??es ou filop?dios nas amostras tratadas, em compara??o ? amostra-controle. A microscopia de for?a at?mica (AFM) mostrou, nas amostras tratadas, defeitos nas superf?cies com geometria variada para picos e vales. Nos ensaios biol?gicos, houve diferen?as significativas na ades?o e prolifera??o celular, em que a superf?cie tratada apresentou um maior desempenho quando comparada com a amostra-controle.Concluiu-se que o processo foi eficiente tanto na remo??o dos ?xidos prim?rios quanto na oxida??o da superf?cie do tit?nio

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-04T20:50:47Z No. of bitstreams: 1 AndreLuisLopesMoriyama_TESE.pdf: 5424215 bytes, checksum: 7e441e3f7c8e167e83a6733578cbcab5 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-05T22:00:58Z (GMT) No. of bitstreams: 1 AndreLuisLopesMoriyama_TESE.pdf: 5424215 bytes, checksum: 7e441e3f7c8e167e83a6733578cbcab5 (MD5) / Made available in DSpace on 2016-01-05T22:00:58Z (GMT). No. of bitstreams: 1 AndreLuisLopesMoriyama_TESE.pdf: 5424215 bytes, checksum: 7e441e3f7c8e167e83a6733578cbcab5 (MD5) Previous issue date: 2014-11-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Esta tese ? parte de pesquisa sobre novos materiais para catalisadores e sensores de g?s mais ativos, sens?veis, e seletivos. O objetivo desta tese foi desenvolver e caracterizar ferrita de cobalto em diferentes morfologias, a fim de estudar sua influ?ncia sobre a resposta el?trica e a atividade catal?tica do material. Foi tamb?m de hierarquizar estes nanocristalitos para obter maior difusividade do g?s no material. Os p?s foram produzidos via hidrot?rmica e solvot?rmica, e foram caracterizados por termogravimetria, difra??o de raios X, microscopia eletr?nica de varredura, microscopia eletr?nica de transmiss?o (difra??o de el?trons, simula??es de alta resolu??o), e espectroscopia de energia dispersiva. As propriedades catal?ticas e el?tricas foram testados em presen?a dos gases CO e NO2, este ?ltimo em diferentes concentra??es (1- 100 ppm), e a diferentes temperaturas (temperatura ambiente at? 350 ?C). Nanooctaedros com tamanho m?dio de 20 nm foram obtidos por via hidrot?rmica. Determinou-se que a forma dos cristalitos est? principalmente associada ? natureza do agente precipitante e ? presen?a de ?ons OHno meio de rea??o. Por via solvot?rmico, foram preparados p?s esf?ricos de CoFe2O4 e com tamanho de cristalitos de 8 e 20 nm. Os p?s de CoFe2O4 apresentam uma resposta forte a pequenas quantidades de NO2 (10 ppm a 200 ?C). Os nanooctatedros tem maior sensibilidade do que os cristalitos esf?ricos de mesmo tamanho, e apresentam menor tempo de resposta e menor tempo de retorno. Estes resultados foram confirmados atrav?s da modelagem da cin?tica de resposta e de recupera??o do sensor. Testes iniciais de atividade catal?tica na rea??o de oxida??o do CO entre 100 ? e 350 ? C mostram que o efeito do tamanho ? predominante em rela??o ao efeito da forma no que diz respeito ? convers?o da rea??o. A morfologia dos cristalitos nanom?tricos influenciou a taxa da rea??o. Uma maior taxa de rea??o ? obtida em presen?a de nanooctaedros. A fim de melhorar as propriedades de detec??o e catal?ticas do material, n?s desenvolvemos uma metodologia de hierarquiza??o de nanocristalitos que envolve o uso de templates a base de carbono. / This thesis is part of research on new materials for catalysis and gas sensors more active, sensitive, selective. The aim of this thesis was to develop and characterize cobalt ferrite in different morphologies, in order to study their influence on the electrical response and the catalytic activity, and to hierarchize these grains for greater diffusivity of gas in the material. The powders were produced via hydrothermal and solvothermal, and were characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy (electron diffraction, highresolution simulations), and energy dispersive spectroscopy. The catalytic and electrical properties were tested in the presence of CO and NO2 gases, the latter in different concentrations (1-100 ppm) and at different temperatures (room temperature to 350 ? C). Nanooctahedra with an average size of 20 nm were obtained by hydrothermal route. It has been determined that the shape of the grains is mainly linked to the nature of the precipitating agent and the presence of OH ions in the reaction medium. By solvothermal method CoFe2O4 spherical powders were prepared with grain size of 8 and 20 nm. CoFe2O4 powders exhibit a strong response to small amounts of NO2 (10 ppm to 200 ? C). The nanooctahedra have greater sensitivity than the spherical grains of the same size, and have smaller response time and shorter recovery times. These results were confirmed by modeling the kinetics of response and recovery of the sensor. Initial tests of catalytic activity in the oxidation of CO between temperatures of 100 ?C and 350 ?C show that the size effect is predominant in relation the effect of the form with respect to the conversion of the reaction. The morphology of the grains influence the rate of reaction. A higher reaction rate is obtained in the presence of nanooctahedra. In order to improve the detection and catalytic properties of the material, we have developed a methodology for hierarchizing grains which involves the use of carbonbased templates.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-04-26T19:29:13Z No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-04-28T23:50:33Z (GMT) No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) / Made available in DSpace on 2016-04-28T23:50:33Z (GMT). No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) Previous issue date: 2015-03-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Na ind?stria do petr?leo, a ?gua produzida ? o maior volume l?quido produzido com grande capacidade poluidora. Dentre os contaminantes org?nicos, os arom?ticos apresentam o principal risco ao meio ambiente e ? sa?de da popula??o principalmente BTEX. Ao longo dos ?ltimos anos, a eletroqu?mica tem se mostrado eficiente na degrada??o desses compostos, envolvendo apenas a utiliza??o de el?trons como reagentes. Entretanto, o desenho do reator eletroqu?mico, hidrodin?mica e, consequentemente, o coeficiente de transfer?ncia de massa s?o par?metros determinantes na efici?ncia do processo eletroqu?mico. Dentro desse contexto, o objetivo deste trabalho foi investigar geometrias de c?lulas eletroqu?micas, visando determinar os coeficientes de transfer?ncia de massa e entender a sua hidrodin?mica. Foram estudadas c?lulas em batelada e em fluxo, variando a pot?ncia da agita??o, posi??o da agita??o e espa?amento entre os eletrodos, empregando a t?cnica de corrente limite, com um gradiente de concentra??o de 4 a 24 mmol/dm? de K4[Fe(CN)]6 em propor??o molar de 2:1 para K3[Fe(CN)]6 em meio de NaOH 0,5 mol/dm?, a fim de determinar a corrente limite, e consequentemente o coeficiente de transfer?ncia de massa (km). Os resultados obtidos mostraram claramente que na c?lula em batelada, o aumento da agita??o e a posi??o da agita??o influenciaram o km; na c?lula em fluxo, o afastamento dos eletrodos n?o mostra influencia significativa quando a agita??o (fluxo) ? direcionada ? superf?cie do eletrodo; e ainda, as c?lulas em fluxo se mostraram mais eficientes no que diz respeito ? elimina??o de resist?ncias f?sicas inerentes ao tratamento eletro-oxidativo. Por fim, os resultados alcan?ados mostraram que ? poss?vel a aplica??o do reator eletroqu?mico no tratamento de BTX, uma vez que foi identificada uma geometria com o melhor coeficiente de massa, favorecendo a oxida??o das esp?cies na superf?cie do eletrodo, de forma mais r?pida e eficiente. / The oil and gas production processes generate large volumes of waste with high toxicity. In this industry, produced water is the most produced liquid volume with great polluting capacity. Among the organic contaminants, the aromatics, mainly BTEX, present a major risk to the environment and people's health. Over the past years, many studies have been conducted under the electrooxidation of aromatic compounds, showing that the electrochemical degradation is efficient for these substances, even more importantly, the process involves only the use of electrons as reactants. However, the design of the electrochemical reactor, hydrodynamics and mass transfer coefficients are critical parameters on the efficiency of the electrochemical process. In this context, the objective of this study was to investigate geometries of electrochemical cells, to determine the mass transfer coefficients and understand their hydrodynamics. Cells were studied in batch and flow design, varying stirring rate, the stirring position and spacing between electrodes. In order to determine the current limit, and thus the mass transfer coefficient (Km), it was used a concentration gradient of K4[FeCN]6 / K3[FeCN]6 (2:1) from 4 to 24 mM, in medium of 0.5 M NaOH. The results clearly showed that regarding the batch cell, increasing stirring rate and changing its position promote a considerable effect on Km; in the flow cell, no influences were achieved when the spacing of the electrodes was modified when the stirring (flow) is directed to the electrode surface; and, the flow cells are more efficient with regard to the elimination of inherent physical resistance to the electrochemical treatment. Finally, the results showed that the application of reactor is possible to treat electrochemically BTX because the better geometry has been identified, favoring the oxidation of the species on the electrode surface more rapidly and efficiently.