The presence of micropollutants, particularly pesticides, in surface waters across Canada has been of concern not only for their environmental impact, but also for their potential effects on human health and recalcitrant nature to conventional water treatment methods. Although ozone has been mainly applied for disinfection of drinking water, oxidation of trace organics by ozonation has been considered potentially effective. In an effort to meet increasingly stringent drinking water regulations, different solid catalysts have been used to enhance the removal of water contaminants by ozonation. In spite of the increasing number of data demonstrating the effectiveness of heterogeneous catalytic ozonation, the influence of different factors on the efficiency of micropollutants oxidation is still unclear.<p> In the present work, application of three solid catalysts in ozonation of two model micropollutants in pure water was examined using a laboratory-scale reaction system over a range of operating conditions. The three catalysts investigated were activated carbon, alumina, and perfluorooctyl alumina, and the two model micropollutants were the pesticides atrazine and 2,4-dichlorophenoxyactic acid. The effects of solution pH, presence of a radical scavenger, pesticide adsorption on catalyst, and catalyst dose on micropollutant removal were investigated. Solution pH was found to significantly influence the catalyst ability to decompose ozone into free hydroxyl radicals. The effect of these free radicals was markedly inhibited by the radical scavenger resulting in a negative impact on pesticides degradation. In general, the removal rate of pesticides was found to increase with increasing doses of catalyst.<p> In the ozonation process in the presence of activated carbon, atrazine removal rates increased four and two times when using a catalyst dose of 0.5 g L-1 at pH 3 and 7, respectively, whereas observed reaction rates for 2,4-D increased over 5 times in the presence of 1 × 10-4 M tert-butyl alcohol at pH 3. In the ozonation system catalyzed by 8 g L-1 alumina, the observed reaction rate constant of atrazine removal notably improved at neutral pH by doubling the micropollutant removal rate. For the pesticide 2,4-D in the presence of 1 × 10-4 M tert-butyl alcohol at pH 5, the observed removal rate was over ten times higher than that for the non-catalytic ozonation process using also using a catalyst dose of 8 g L-1. Modification of alumina to produce perfluorooctyl alumina resulted in a material able to significantly adsorb atrazine, while not exhibiting affinity for adsorption of 2,4-D. In spite of its adsorptive properties, perfluorooctyl alumina was found to enhance neither molecular ozone reactions nor ozone decomposition into hydroxyl radicals. Thus, the observed removal rates for atrazine and 2,4-D by ozonation in the presence of perfluorooctyl alumina did not increase significantly.

Ozonation is an efficient method to degrade refractory organics in textile wastewaters. In recent years, catalytic ozonation is applied to reduce ozone consumption and to increase chemical oxygen demand and total organic carbon (TOC) removal efficiencies. The ozonation of two industrial dyes, namely Acid Red-151 (AR-151) and Remazol Brilliant Blue R (RBBR) was examined separately both in a semi-batch reactor and also in a fluidized bed reactor (FBR) by conventional and catalytic ozonation with alumina and perfluorooctyl alumina (PFOA) catalysts. The conventional and catalytic ozonation reactions followed a pseudo-first order kinetics with respect to the dye concentration. The highest COD reductions were obtained in the presence of the catalysts at pH=13, with alumina for AR-151 and with PFOA for RBBR. Residence time distribution experiments were performed to understand the degree of liquid mixing in the reactor. The behaviour of the FBR was almost equivalent to the behaviour of one or two completely stirred tank reactors in series in the presence of the solid catalyst particles. The volumetric ozone-water mass transfer coefficients (kLa) were found at various gas and liquid flow rates and catalyst dosages in the FBR. A model was developed to find kLa in the reactor by comparing the dissolved O3 concentrations in the experiments with the model results. kLa increased significantly by the increase of gas flow rate. Higher catalysts dosages at the fluidization conditions yielded higher kLa values indicating higher rates of mass transfer. Dye ozonation experiments without catalyst and with alumina or PFOA catalyst were conducted at different conditions of the inlet dye concentration, gas and liquid flow rates, inlet ozone concentration in the gas, catalyst dosage, particle size and pH. The dye and TOC removal percentages were increased with the increase of gas flow rate and with the decrease of both the liquid flow rate and inlet dye concentration. The addition of the catalyst was beneficial to enhance the TOC degradation. The ozone consumed per liter of wastewater was much lower when the catalyst was present in the reactor. In terms of TOC removal and O3 consumption, the most efficienct catalyst was PFOA. According to the organic analysis, the intermediate by-products were oxalic, acetic, formic and glyoxalic acids in RBBR and AR-151 ozonation. The dye and dissolved ozone concentration profiles were predicted from a developed model and the model results were compared with the experimental results to obtain the enhanced kLa values. The presence of the chemical reaction and the catalysts in the FBR, enhanced the kLa values significantly. The enhancement factor (E) was found as between 0.97 and 1.93 for the non-catalytic ozonation and 0.96 and 1.53 for the catalytic ozonation at pH = 2.5. The dimensionless number of Hatta values were calculated between 0.04-0.103 for the sole ozonation of RBBR and AR-151 solutions. According to the calculated Ha values, the reaction occurred in the bulk liquid and in the film being called as the intermediate regime in the literature.

Textile wastewaters are highly colored and non-biodegradable having variable compositions of colored dyes, surfactants and toxic chemicals. Recently, ozonation is considered as an effective method that can be used in the treatment of industrial wastewaters / catalytic ozonation being one of the advanced oxidation processes (AOPs), is applied in order to reduce the ozone consumption and to increase the chemical oxygen demand (COD) and total organic carbon (TOC) removals. In this study, catalytic ozonation of industrial textile wastewater (ITWW) obtained from AKSA A.S. (Yalova, Istanbul) textile plant has been examined in a three phase fluidized bed reactor at different conditions. The effects of inlet chemical oxygen demand concentration (CODin), pH, different catalyst types [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage on ozonation process were determined. Moreover, the changes in the organic removal efficiencies with gas to liquid flow rate ratio were investigated. The dispersion coefficients (DL) and volumetric ozone-water mass transfer coefficients (kLa) were estimated at various gas and liquid flow rates in order to observe the effect of liquid mixing in the reactor on ozonation process. It was observed that increasing both gas and liquid flow rates by keeping their ratio constant provided higher organic removal efficiencies due to the higher mixing in the liquid phase. The dyes present in ITWW sample were known to be Basic Blue 41 (BB 41), Basic Red 18.1 (BR 18.1) and Basic Yellow 28 (BY 28). The &ldquo / absorbance vs. concentration&rdquo / calibration correlations were developed to estimate the amounts of these colored dyes in the ITWW sample. This provided the opportunity to examine the degradation of each dye in this wastewater separately. While PFOA catalyst was found to increase the removal efficiency of BY 28 at an acidic pH of 4, alumina yielded highest color removals for BB 41 and BR 18.1 at a pH of 12. The highest TOC and COD reductions being 24.4% and 29.5%, respectively, were achieved in the catalytic ozonation of the ITWW using alumina as the catalyst at a pH of 12 and at a gas to liquid flow rate ratio of 1.36 (QG = 340 L/h, QL = 250 L/h). At the same conditions, also the highest overall color removal in terms of Pt-Co color unit, namely 86.49%, were obtained due to the lower BY 28 concentration in the WW sample than those of the BB 41 and BR 18.1. In addition, the oxidation of BB 41, BR 18.1 and BY 28 dyes were investigated in a semi-batch reactor by sole and catalytic ozonations with alumina and PFOA catalyst particles. The sole and catalytic ozonation reactions followed a pseudo-first order kinetics with respect to dye concentration. The highest TOC and COD removals being 58.3% and 62.9%, respectively, were obtained at pH of 10 for BB 41 and 55.2% and 58.8%, respectively, for BR 18.1 with alumina catalyst. On the other hand, for BY 28 PFOA catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%, respectively, at pH of 4.

Environmental regulations have imposed limitations on a wide variety of organic and inorganic pollutants in industrial textile wastewaters. There are several degradation methods used in literature studies. Among these methods ozonation is one of the most considered way to degrade refractory chemicals in textile wastewaters. In recent years, catalytic ozonation as being one of the advanced oxidation processes (AOPs), is applied to reduce the ozone consumption and to increase the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removals. Ozonation and catalytic ozonation of single and mixed dye solutions have been examined both in a semi-batch reactor and also in a three phase fluidized bed reactor. The dyes that are used in this study are Basic Blue 41 (BB-41), Basic Yellow 28 (BY-28) and Basic Red 18.1 (BR-18.1), these dyes are obtained from AKSA A.S. (Yalova, Istanbul) textile plant. In order to measure the concentration of each dye in the mixed dye solution, &ldquo / absorbance vs. concentration&rdquo / calibration correlations were developed. The effect of inlet dye concentration, inlet gas and liquid flow rates, pH, catalyst type [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage were determined experimentally. Catalyst characterization analyses were done in order to determine the maximum number of times that the catalyst can be used and it was found to be 3 times. Gas washing bottle experiments are conducted to find the v amount of ozone required to oxidize one mole of each dye used in the study. Oxidation of BB-41, BR-18.1 and BY-28 dyes were investigated in a semi-batch reactor as single dye solutions by sole and catalytic ozonation with alumina and PFOA catalyst particles. The highest TOC and COD removals being 58.3% and 62.9%, respectively, were obtained at pH of 10 for BB-41 and 55.2% and 58.8%, respectively, for BR-18.1 with alumina catalyst. On the other hand, for BY-28 PFOA catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%, respectively, at pH of 4. Minimum fluidization velocity (uL,min), the hold-up values of gas, liquid and solid phases, the dispersion coefficients (DL), and volumetric ozone-water mass transfer coefficients (kLa) were estimated at various gas and liquid flow rates in order to observe the effect of liquid mixing in the reactor on ozonation process. While PFOA catalyst was found to be effective in oxidizing BY-28 in acidic conditions (pH=4), BR-18.1 and BB-41 are degraded in alkaline medium (pH=10) with alumina catalyst better compared to acidic conditions. For catalytic ozonation reactions in fluidized bed reactor, the highest dye removals in mixed dye solution were observed for BY- 28 being 99.29% for gas flow rate (QG) of 340 L/h, liquid flow rate (QL) of 150 L/h and pH=4, initial dye concentration being 30 mg/L of each dye with PFOA catalyst, while for BR-18.1 and BB-41 being 95.39% and 97.95% respectively for QG = 340 L/h, QL = 150 L/h and pH=10, initial dye concentration being 30 mg/L of each dye with alumina catalyst. The highest TOC and COD reductions, 25.2% and 32.4%, respectively, were achieved in the catalytic ozonation of the mixed dye using PFOA as the catalyst at a pH of 4 and at a gas to liquid flow rate ratio of 2.26 (QG = 340 L/h, QL = 150 L/h). Highest dye removals were obtained at the same gas and liquid flow rates as those of the highest TOC and COD reductions in the experiments. Empirical TOC removal equations were obtained as a function of inlet TOC concentration, solution pH, gas and liquid flow rates.

Made available in DSpace on 2014-12-17T14:06:48Z (GMT). No. of bitstreams: 1 JoseRCQ.pdf: 1649143 bytes, checksum: 51cca0511bbe445cfdc5a7308f841ccf (MD5) Previous issue date: 2007-09-14 / The system in-Ceram Alumina, produced by VITA, consists in a technique of prepare of a substructure of ceramics to dental crowns. First burning is made in the alumina decanted by slip casting process under a stone die that reproduces the tooth prepared to receive a crown. In a second burning, alumina is infiltrated by vitreous system, giving to this set a high mechanic resistance. In this work, it s made a study of the composition of a new infiltrating material more used nowadays, giving to alumina desirable mechanics proprieties to its using like substructure of support to ceramic s crown used in the market today. The addition of Lanthanum oxide (frit A) and calcium oxide (frit B) was made in attempt to increase the viscosity of LZSA and to reduce fusion temperature. The frits were put over samples of alumina and took to the tubular oven to 1400?C under vacuum for two groups (groups 1 and 2). For another two groups (groups 3 and 4) it was made a second infiltration, following the same parameters of the first. A fifth group was utilized like group of control where the samples of pure alumina were not submitted to any infiltrating process. Glasses manifested efficient both in quality and results of analysis of mechanic resistance, being perfectly compatible with oral environment in this technical requisite. The groups that made a second infiltration had he best results of fracture toughness, qualify the use in the oral cavity in this technical question. The average of results achieved for mechanic resistance to groups 1, 2, 3, 4 and 5 were respectively 98 MPa, 90 MPa, 144 MPa, 236 MPa and 23 MPa / O sistema In-Ceram Alumina, fabricado pela VITA, consiste numa t?cnica de confec??o de uma infra-estrutura cer?mica para coroas dentais. Uma primeira queima ? realizada na alumina depositada pelo processo de slip casting sob um troquel de gesso que reproduz o dente preparado para receber a coroa. Numa segunda queima, a alumina ? infiltrada por um sistema v?treo, conferindo a este conjunto uma elevada resist?ncia mec?nica. Neste trabalho procurou-se estudar a composi??o de um novo material infiltrante baseado no sistema Li2O ZrO2 SiO2 Al2O3 (LZSA) com adi??o de La2O3 ou CaO, a fim de substituir o material importado mais usado atualmente (In-Ceram glass da Vita Zahnfabrik), proporcionando a alumina as propriedades mec?nicas desej?veis para seu emprego como infra-estrutura de suporte ?s coroas puras de cer?mica utilizadas na odontologia, diminuindo custos frente a esse sistema oferecidos hoje no mercado. O acr?scimo de ?xido de lant?nio (frita A) e ?xido de c?lcio (frita B) foi realizado na tentativa de aumentar a viscosidade do LZSA e diminuir a sua temperatura de fus?o. As fritas foram depositadas sobre amostras de alumina e levadas ao forno tubular a 1400?C sob v?cuo em dois grupos (1 e 2). Para outros dois grupos (3 e 4) foi realizada uma segunda infiltra??o, seguindo os mesmo par?metros da primeira. Um 5? grupo foi utilizado como grupo controle onde as amostras de alumina pura n?o foram submetidas a qualquer processo infiltrat?rio. Os vidros se mostraram eficazes tanto na qualidade da infiltra??o como nos resultados das an?lises de resist?ncia mec?nica. Os grupos que foram submetidos ? dupla infiltra??o obtiveram melhores resultados de resist?ncia mec?nica, sendo perfeitamente compat?veis com o meio oral nesse quesito t?cnico. A m?dia dos resultados obtidos para resist?ncia mec?nica para os grupos 1, 2, 3, 4 e 5 foram respectivamente 98 MPa, 90 MPA, 144 MPA, 236 MPa e 23 MPa

Made available in DSpace on 2014-12-17T14:06:54Z (GMT). No. of bitstreams: 1 ClaudiaAMS_DISSERT.pdf: 2577371 bytes, checksum: 741bbb91aaccd5dd4b233f1b8017a831 (MD5) Previous issue date: 2010-03-29 / The continuous advances in ceramic systems for crowns and bridges infrastructure getting researchers and manufacturers looking for a material that has good mechanical properties and aesthetic. The purpose of this study was to verify in which composition and sintering temperature the ceramic system for infrastructure composed of alumina and zirconia would have the best mechanical properties. With this objective we made in UFRN laboratories 45 test bodies in the form of rectangular bars with the following dimensions: 30mm x 8mm x 3mm, where we separated by the sintering temperature: 1200?C, 1300?C and 1400?C, and by comp osition: 33% Zirconia + 67% Alumina; 50% Zirconia + 50% Alumina and 25% Zirconia + 75% Alumina, these test bodies were not infiltrated with glass. Also, were made nine test bodies by a technical from a laboratory with a commercial ceramic system: in the Ceram Zirc?nia (Vita - Zahnfabrik) with the following dimensions: 20mm x 10mm x 0.5mm, these test bodies following all recommendations of the manufacturer and were infiltrated with glass. Were realized optical and electronic microscopy analyses, hardness testing, resistance to bending in three points, porosity and bulk density. After analysis of the results we verified that with the increasing of sintering temperature, increased the value of resistance to bending, but with the same temperature there was no significant difference between the different compositions, samples made with the commercial ceramic that were infiltrated, presented a resistance to bending six times greater than the samples sintered to 1400?C and which have not been infiltra ted. There was no significant difference between the values of apparent porosity for the samples made in UFRN laboratories, but the samples of commercial ceramic obtained 0% in porosity apparent value. In tests of Rockwell Hardness there is an increase in the value of Hardness, with the increase of sintering temperature for the samples not infiltrated. Samples infiltrated showed similar values as the samples sintered in 1400?C. There was no significant difference between the values of apparent density among samples manufactured in UFRN laboratories and samples made with a commercial ceramic / Os avan?os constantes dos sistemas cer?micos para infra-estruturas de coroas e pontes fazem com que os pesquisadores e fabricantes busquem um material que tenha boas propriedades mec?nicas e est?ticas. O intuito deste trabalho foi verificar em qual composi??o e temperatura de sinteriza??o o sistema cer?mico a base de alumina e zirc?nia para infra-estrutura teria as melhores propriedades mec?nicas. Com este objetivo confeccionamos nos laborat?rios da UFRN 45 corpos-e-prova em forma de barras retangulares com as seguintes dimens?es: 30mm x 8mm x 3mm, onde os separamos por temperatura de sinteriza??o: 1200?C, 1300?C e 1400?C; e por composi??o: 33% Zirc?nia + 67% Alumina; 50% Zirc?nia + 50% Alumina e 25% Zirc?nia + 75% Alumina, estes corpos-de-prova n?o foram infiltrados com vidro. Foram confeccionados ainda nove corpos- e-prova por um t?cnico de laborat?rio com um sistema cer?mico comercial o In Ceram Zirc?nia (Vita Zahnfabrik) com as seguintes dimens?es: 20mm x 10mm x 0,5mm, estes corpos-de-prova seguiram todas as recomenda??es do fabricante e foram infiltrados com vidro. Foram realizadas an?lises por microscopia ?tica e eletr?nica, ensaios de dureza, de resist?ncia ? flex?o em tr?s pontos, porosidade e densidade aparente. Ap?s a an?lise dos resultados verificamos que com o aumento da temperatura de sinteriza??o, aumentamos o valor da resist?ncia ? flex?o, sendo que dentro da mesma temperatura n?o houve diferen?a significante entre as diferentes composi??es, as amostras confeccionadas com a cer?mica comercial e que foram infiltradas apresentaram uma resist?ncia ? flex?o seis vezes maior que as amostras sinterizadas ? 1400?C e que n?o foram infiltradas. N?o houve diferen?a significante entre os valores da porosidade aparente para as amostras confeccionadas nos laborat?rios da UFRN, j? as amostras da cer?mica comercial obtiveram um valor de 0% de porosidade aparente. Nos ensaios de Dureza Rockwell verifica-se um aumento no valor da Dureza, com o aumento da temperatura de sinteriza??o das amostras n?o infiltradas. As amostras infiltradas apresentaram valores similares aos das amostras sinterizadas ? 1400?C. N?o houve diferen?a significante entre os valores de densidade aparente entre as amostras confeccionadas nos laborat?rios da UFRN e as amostras confeccionadas com a cer?mica comercial

Neste trabalho, inicialmente, foram obtidos TPSs (amidos termoplásticos) com diferentes concentrações de amido e plastificantes, por processamento em câmara de mistura, com o objetivo de determinar formulações para estudo em extrusora reativa. As formulações de TPS que apresentaram os melhores resultados de torque reométrico foram as que continham 39%m/m de amido. Investigou-se a influência da velocidade da rosca na obtenção de TPS por extrusora reativa, e os resultados mostraram que este parâmetro teve pequena influência na estabilidade do amido termoplástico, sendo possível utilizar 150 rpm de rotação. Foram produzidas 5 blendas com razões de TPS:PEBDL variando de 30:70; 40:60; 50;50; 60:40 e 70:30 para o desenvolvimento de um sistema ligante para a injeção de alumina pelo processo de moldagem de pós (MPI), a partir das quais foi possível analisar a influência do TPS no PEBDL, através de análises de MEV, IF, TGA, DMA e propriedades mecânicas. Quanto maior a concentração de TPS nas blendas, mais heterogênea foi a morfologia observada por MEV e menor o módulo de armazenamento e de perda obtidos por DMA. Este comportamento foi similar ao encontrado pela análise de resistência à tração, que apresentou propriedades mecânicas pobres para elevadas concentrações de TPS. Foram escolhidas três blendas para testar como veículo orgânico em feedstocks de alumina, com carga de partícula sólida de 45%, 50% e 55%v/v de Al2O3. A carga crítica para o sistema ligante-partículas sólidas determinada por reometria de torque foi de 50%v/v de alumina. / In this work, TPSs (thermoplastic starch), with different concentrations of starch and plasticizers for processing in the mixing chamber, were obtained in order to determine formulations for study in a reactive extruder. The TPS formulations that showed the best results for the rheometric torque were those containing 39% w/w starch. The influence of the screw speed to obtain TPS in the reactive extruder was investigated and the results showed that this parameter had little influence on the stability of the thermoplastic starch, allowing the use of 150 rpm rotation speed. Five blends were produced, with TPS:LLDPE ratios of 30:70; 40:60; 50:50; 60:40 and 70:30, to develop a binder for alumina injection by the powder molding process (MPI). From these five systems it was possible to analyze the influence of TPS in LLDPE through SEM analyzes, MFI, TGA, DMA and mechanical properties. The higher the concentration of TPS in blends, more heterogeneous morphology was observed by SEM and the lowest storage and loss modulus were obtained by DMA. This behavior was similar to that found by analysis of tensile strength, which showed poor mechanical properties for high concentrations of TPS. Three blends were chosen for testing as an organic vehicle in alumina feedstocks, with solid particles load of 45%, 50% and 55% v/v of Al2O3. The critical load for the system binder-solid particles, determined by torque rheometry, was 50% v/v of alumina.

Esta tese investigou o efeito da taxa de resfriamento em partículas de Al2O3, Al2O3 - TiO2, e Al2TiO5 aspergidas por pistola a plasma e submetidas a diferentes taxas de resfriamento (alta: aspersão contra um substrato metálico a 100 mm de distância da pistola de plasma, e baixa: contra uma superfície de água, a 300 mm de distância). Os resultados foram avaliados por microscopia eletrônica de varredura (com EDX) e por difração de raio X para a caracterização de fases e cálculo de tamanho de cristalito por Single Line. O óxido Al2TiO5 na forma de pó quase amorfo com composição estequiométrica de tialita (tialita*) aspergido foi obtido por coprecipitação, a partir dos precursores TiCl4 e Al(NO4)3, tratado termicamente a 400, 600, 800, 900, 1000, 1200, 1300 e 1400 °C, com 6 h de patamar. Nos tratamentos térmicos com 6 horas de patamar a 800 °C e mais nitidamente a 900 °C, é identificada a formação parcial da fase tialita; desta forma, foram realizados tratamentos térmicos a 900, 1000 e 1100 °C, porém com 30 minutos de patamar. A Al2O3-a com tamanho de cristalito micrométrico foi obtida para menores taxas de resfriamento. Com o aumento da taxa de resfriamento, predominaram nanocristalitos de alumina Al2O3-g, coexistindo com fase amorfa. Já para a titânia, a fase rutilo pode ser obtida mesmo com altas taxas de resfriamento. Quando a tialita* foi submetida à alta taxa de resfriamento, levou exclusivamente à formação da fase metaestável tialita b como estrutura cristalina. No entanto, o mesmo pó, a taxas de resfriamento não tão altas, resultou na obtenção de tialita b, Al2O3-a e rutilo. Tratamentos térmicos da tialita* propiciaram a formação de tialita b, e incipientemente anatásio, com tamanho de cristalito muito pequeno (abaixo de 30 nm). À medida que a temperatura de tratamento térmico aumentou, surgiram simultaneamente as fases Al2O3-a, rutilo e tialita b. A obtenção de fases metaestáveis só foi possível quando o tamanho de cristalito era pequeno – abaixo de 100 nm, o que evidenciou a importância do número de átomos na superfície, como fator de estabilização (ou metaestabilização) de fases obtidas foras do equilíbrio. / This thesis investigated the effect of cooling rate of Al2O3, Al2O3 - TiO2 and Al2TiO5 particles plasma sprayed and subjected to different cooling rates (high: to spray against a metal substrate to 100 mm away from the plasma gun, and low: against a surface of water, 300 milimeters away). The results were evaluated by scanning electron microscope (with EDX) and X ray diffraction to characterize phases and crystallite size through Single Line. The sprayed Al2TiO5 oxide was a quasi-amorphous powder with stoichiometric composition of tialite (tialita*) obtained by co-precipitation from precursors TiCl4 and Al(NO4)3, heat treated at 400, 600, 800, 900, 1000, 1200, 1300 and 1400 °C with 6 hours of dwell. In the heat treatments with 6 hour of dwell at 800 ° C and more explicitly at 900 °C, is identified partial formation of tialite phase; then, heat treatments were performed at 900, 1000 and 1100 ° C, but with 30 minutes of dwell. Basically, a-Al2O3 with micrometer crystallite size was obtained for smaller cooling rates. By increasing the cooling rate, there were predominantly g-Al2O3 nanocrystallites coexisting with amorphous phase. However, for the titania, the rutile phase could be obtained even with high cooling rates. When tialita* was subjected to high cooling rate, exclusively, metastable b tialite was observed as crystalline phase. However, the same powder, with cooling rates not so high, resulted in b tialite, a-Al2O3 and rutile. Heat treatments of tialita* provided the formation of b tialite, and incipiently anatase with crystallite size very small (below 30 nm). As the heating treatment temperature was increased, there were simultaneously a-Al2O3, rutile and b tialite phases. Metastable phases were obtained only when the crystallite size was small - less than 100 nm. This highlighted the importance of the number of atoms on the surface as a stabilizing factor (or metastabilization) to produce phases out of equilibrium.

141 f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-03-22T16:05:41Z No. of bitstreams: 1 Tese final Ednaldo Sousa.pdf: 2728911 bytes, checksum: ab82406a11153fd2c6032629dc6be132 (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-06-04T14:33:45Z (GMT) No. of bitstreams: 1 Tese final Ednaldo Sousa.pdf: 2728911 bytes, checksum: ab82406a11153fd2c6032629dc6be132 (MD5) / Made available in DSpace on 2013-06-04T14:33:45Z (GMT). No. of bitstreams: 1 Tese final Ednaldo Sousa.pdf: 2728911 bytes, checksum: ab82406a11153fd2c6032629dc6be132 (MD5) Previous issue date: 2012 / CNPq / A emissão de poluentes atmosféricos, tais como, monóxido de carbono (CO), óxidos de enxofre (SOX) e óxidos de nitrogênio (NOX) é, atualmente, um dos maiores problemas encontrados em processos industriais. O óxido nítrico (NO) representa cerca de 95% de toda emissão de NOX para a atmosfera. Uma das principais fontes de emissão de NOX são as unidades de regeneração de catalisadores de craqueamento catalítico em leito fluidizado (FCC). Nesse trabalho, foram utilizados catalisadores de irídio suportados em aluminas (0,1-1,0%/Al2O3) e em aluminas modificadas com índio (0,1%Ir/InxAl2-xO3). Os catalisadores foram preparados pelo método de impregnação úmida, sendo que para os suportes foi utilizado o método da combustão. Os materiais obtidos foram avaliados cataliticamente na redução de NO com CO na presença de O2, H2O e SO2. Todos os catalisadores mostraram-se ativos e hidrotermicamente estáveis em toda região de temperatura investigada (250 – 600°C) operando sobre alta velocidade espacial. O s catalisadores que não continham In em suas formulações apresentaram uma pequena desativação na presença de SO2, enquanto que, para os que possuíam In a presença de SO2 no meio reacional aumentou a atividade dos catalisadores, comprovando o efeito promotor deste metal. Catalisadores com baixo teor de Ir mostraram-se mais ativos do que os com altos teores. A influência do O2 no meio reacional também foi investigada, onde foi verificada uma forte dependência da presença do mesmo para a atividade do catalisador. Na ausência de O2, os catalisadores investigados tiveram uma significativa redução da atividade tanto na redução de NO quanto na conversão de CO. Avaliando o efeito do pré-tratamento, verificou-se que as amostra préreduzidas tiveram um maior desempenho no teste catalítico do que as pré-oxidadas. Sugerindo assim, que o sítio ativo para a redução de NO com CO sobre catalisadores de irídio é o Ir0. Todos os catalisadores demonstraram alta conversão de CO e seletividade a CO2. / Salvador

Neste trabalho, inicialmente, foram obtidos TPSs (amidos termoplásticos) com diferentes concentrações de amido e plastificantes, por processamento em câmara de mistura, com o objetivo de determinar formulações para estudo em extrusora reativa. As formulações de TPS que apresentaram os melhores resultados de torque reométrico foram as que continham 39%m/m de amido. Investigou-se a influência da velocidade da rosca na obtenção de TPS por extrusora reativa, e os resultados mostraram que este parâmetro teve pequena influência na estabilidade do amido termoplástico, sendo possível utilizar 150 rpm de rotação. Foram produzidas 5 blendas com razões de TPS:PEBDL variando de 30:70; 40:60; 50;50; 60:40 e 70:30 para o desenvolvimento de um sistema ligante para a injeção de alumina pelo processo de moldagem de pós (MPI), a partir das quais foi possível analisar a influência do TPS no PEBDL, através de análises de MEV, IF, TGA, DMA e propriedades mecânicas. Quanto maior a concentração de TPS nas blendas, mais heterogênea foi a morfologia observada por MEV e menor o módulo de armazenamento e de perda obtidos por DMA. Este comportamento foi similar ao encontrado pela análise de resistência à tração, que apresentou propriedades mecânicas pobres para elevadas concentrações de TPS. Foram escolhidas três blendas para testar como veículo orgânico em feedstocks de alumina, com carga de partícula sólida de 45%, 50% e 55%v/v de Al2O3. A carga crítica para o sistema ligante-partículas sólidas determinada por reometria de torque foi de 50%v/v de alumina. / In this work, TPSs (thermoplastic starch), with different concentrations of starch and plasticizers for processing in the mixing chamber, were obtained in order to determine formulations for study in a reactive extruder. The TPS formulations that showed the best results for the rheometric torque were those containing 39% w/w starch. The influence of the screw speed to obtain TPS in the reactive extruder was investigated and the results showed that this parameter had little influence on the stability of the thermoplastic starch, allowing the use of 150 rpm rotation speed. Five blends were produced, with TPS:LLDPE ratios of 30:70; 40:60; 50:50; 60:40 and 70:30, to develop a binder for alumina injection by the powder molding process (MPI). From these five systems it was possible to analyze the influence of TPS in LLDPE through SEM analyzes, MFI, TGA, DMA and mechanical properties. The higher the concentration of TPS in blends, more heterogeneous morphology was observed by SEM and the lowest storage and loss modulus were obtained by DMA. This behavior was similar to that found by analysis of tensile strength, which showed poor mechanical properties for high concentrations of TPS. Three blends were chosen for testing as an organic vehicle in alumina feedstocks, with solid particles load of 45%, 50% and 55% v/v of Al2O3. The critical load for the system binder-solid particles, determined by torque rheometry, was 50% v/v of alumina.