Degradação de atrazina por processo foto-Fenton monitorado por injeção seqüencial e cromatografia a líquido de alta eficiência

Processos de fotodegradação de compostos orgânicos tóxicos têm sido bastante estudados. Este trabalho trata da aplicação do processo foto-Fenton para a degradação de atrazina em água (composto modelo). O efeito das concentrações dos seguintes compostos foi avaliado: peróxido de hidrogênio (2 a 6 mmol L-1) e ferrioxalato de potássio (0,2 a 1 mmol L-1). Os experimentos foram realizados em um reator com lâmpada UV - 8W (254nm). O processo de fotodegradação foi monitorado por medidas de espectrofotometria de absorção molecular automatizada por injeção seqüencial (SIA) para determinação de peróxido de hidrogênio e por cromatografia a líquido de alta eficiência (CLAE) para determinação de atrazina e metabólitos. Os experimentos demonstram que o processo de foto-Fenton é viável para o tratamento de atrazina em água.

Tablas para saber el valor líquido de la plata segun su peso : desde 1/8 de onza hasta 138 marcos y ley de once dineros a doce ... /

Mode of access: Internet.

Desenvolvimento de material BaCexPr1-xO3 (0 ≤ X ≤ 1) com estrutura perovskita para oxidação catalítica do CO a CO2 em reator de leito fixo

Barium Cerate (BaCeO3) is perovskite type structure of ABO3, wherein A and B are metal cations. These materials, or doped, have been studied by having characteristics that make them promising for the application in fuel cells solid oxide, hydrogen and oxygen permeation, as catalysts, etc .. However, as the ceramic materials mixed conductivity have been produced by different synthesis methods, some conditions directly influence the final properties, one of the most important doping Site B, which may have direct influence on the crystallite size, which in turn directly influences their catalytic activity. In this study, perovskite-type (BaCexO3) had cerium gradually replaced by praseodymium to obtain ternary type materials BaCexPr1-xO3 and BaPrO3 binaries. These materials were synthesized by EDTA/Citrate complexing method and the material characterized via XRD, SEM and BET for the identification of their structure, morphology and surface area. Moreover were performed on all materials, catalytic test in a fixed bed reactor for the identification of that person responsible for complete conversion of CO to CO2 at low operating temperature, which step can be used as the subsequent production of synthesis gas (CO + H2) from methane oxidation. In the present work the crystalline phase having the orthorhombic structure was obtained for all compositions, with a morphology consisting of agglomerated particles being more pronounced with increasing praseodymium in the crystal structure. The average crystal size was between 100 nm and 142,2 nm. The surface areas were 2,62 m²g-1 for the BaCeO3 composition, 3,03 m²g-1 to BaCe0,5Pr0,5O3 composition and 2,37 m²g-1 to BaPrO3 composition. Regarding the catalytic tests, we can conclude that the optimal flow reactor operation was 50 ml / min and the composition regarding the maximum rate of conversion to the lowest temperature was BaCeO3 to 400° C. Meanwhile, there was found that the partially replaced by praseodymium, cerium, there was a decrease in the catalytic activity of the material.

Avaliação da influência de surfactantes químico e biológico na hidrólise enzimática de casca de coco verde após pré-tratamento ácido/alcalino e com peróxido de hidrogênio alcalino

In Brazil many types of bioproducts and agroindustrial waste are generated currently, such as cacashew apple bagasse and coconut husk, for example. The final disposal of these wastes causes serious environmental issues. In this sense, waste lignocellulosic content, as the shell of the coconut is a renewable and abundant raw material in which its use has an increased interest mainly for the 2nd generation ethanol production. The hydrolysis of cellulose to reducing sugars such as glucose and xylose is catalysed by a group of enzymes called cellulases. However, the main bottleneck in the enzymatic hydrolysis of cellulose is the significant deactivation of the enzyme that shows irreversible adsorption mechanism leading to reduction of the cellulose adsorption onto cellulose. Studies have shown that the use of surfactants can modify the surface property of the cellulose therefore minimizing the irreversible binding. The main objective of the present study was to evaluate the influence of chemical and biological surfactants during the hydrolysis of coconut husk which was subjected to two pre-treatment in order to improve the accessibility of the enzymes to the cellulose, removing this way, part of the lignin and hemicellulose present in the structure of the material. The pre-treatments applied to coconut bagasse were: Acid/Alkaline using 0.6M H2SO4 followed by 1M NaOH, and the one with Alkaline Hydrogen Peroxide at a concentration of 7.35% (v/v) and pH 11.5. Both the material no treatment and pretreated were characterized using analysis of diffraction X-ray (XRD), Scanning Electron Microscopy (SEM) and methods established by NREL. The influence of both surfactants, chemical and biological, was used at concentrations below the critical micelle concentration (CMC), and the concentrations equal to the CMC. The application of pre-treatment with coconut residue was efficient for the conversion to glucose, as well as for the production of total reducing sugars, it was possible to observe that the pretreatment fragmented the structure as well as disordered the fibers. Regarding XRD analysis, a significant increase in crystallinity index was observed for pretreated bagasse acid/alkali (51.1%) compared to the no treatment (31.7%), while that for that treated with PHA, the crystallinity index was slightly lower, around 29%. In terms of total reducing sugars it was not possible to observe a significant difference between the hydrolysis carried out without the use of surfactant compared to the addition of Triton and rhamnolipid. However, by observing the conversions achieved during the hydrolysis, it was noted that the best conversion was using the rhamnolipíd for the husk pretreated with acid/alkali, reaching a value of 33%, whereas using Triton the higher conversion was 23.8%. The coconut husk is a residue which can present a high potential to the 2nd generation ethanol production, being the rhamonolipid a very efficient biosurfactant for use as an adjuvant in the enzymatic process in order to act on the material structure reducing its recalcitrance and therefore improving the conditions of access for enzymes to the substrate increasing thus the conversion of cellulose to glucose.

Avaliação da influência de surfactantes químico e biológico na hidrólise enzimática de casca de coco verde após pré-tratamento ácido/alcalino e com peróxido de hidrogênio alcalino

In Brazil many types of bioproducts and agroindustrial waste are generated currently, such as cacashew apple bagasse and coconut husk, for example. The final disposal of these wastes causes serious environmental issues. In this sense, waste lignocellulosic content, as the shell of the coconut is a renewable and abundant raw material in which its use has an increased interest mainly for the 2nd generation ethanol production. The hydrolysis of cellulose to reducing sugars such as glucose and xylose is catalysed by a group of enzymes called cellulases. However, the main bottleneck in the enzymatic hydrolysis of cellulose is the significant deactivation of the enzyme that shows irreversible adsorption mechanism leading to reduction of the cellulose adsorption onto cellulose. Studies have shown that the use of surfactants can modify the surface property of the cellulose therefore minimizing the irreversible binding. The main objective of the present study was to evaluate the influence of chemical and biological surfactants during the hydrolysis of coconut husk which was subjected to two pre-treatment in order to improve the accessibility of the enzymes to the cellulose, removing this way, part of the lignin and hemicellulose present in the structure of the material. The pre-treatments applied to coconut bagasse were: Acid/Alkaline using 0.6M H2SO4 followed by 1M NaOH, and the one with Alkaline Hydrogen Peroxide at a concentration of 7.35% (v/v) and pH 11.5. Both the material no treatment and pretreated were characterized using analysis of diffraction X-ray (XRD), Scanning Electron Microscopy (SEM) and methods established by NREL. The influence of both surfactants, chemical and biological, was used at concentrations below the critical micelle concentration (CMC), and the concentrations equal to the CMC. The application of pre-treatment with coconut residue was efficient for the conversion to glucose, as well as for the production of total reducing sugars, it was possible to observe that the pretreatment fragmented the structure as well as disordered the fibers. Regarding XRD analysis, a significant increase in crystallinity index was observed for pretreated bagasse acid/alkali (51.1%) compared to the no treatment (31.7%), while that for that treated with PHA, the crystallinity index was slightly lower, around 29%. In terms of total reducing sugars it was not possible to observe a significant difference between the hydrolysis carried out without the use of surfactant compared to the addition of Triton and rhamnolipid. However, by observing the conversions achieved during the hydrolysis, it was noted that the best conversion was using the rhamnolipíd for the husk pretreated with acid/alkali, reaching a value of 33%, whereas using Triton the higher conversion was 23.8%. The coconut husk is a residue which can present a high potential to the 2nd generation ethanol production, being the rhamonolipid a very efficient biosurfactant for use as an adjuvant in the enzymatic process in order to act on the material structure reducing its recalcitrance and therefore improving the conditions of access for enzymes to the substrate increasing thus the conversion of cellulose to glucose.

Produção de biogás a partir da co-digestão de resíduos da geração de energia

Aplicações de microalgas tem tornado esses micro-organismos importantes em pesquisas com fins tanto comerciais como energéticos. A biofixação de CO2 por microalgas é vista como uma forma economicamente viável e ambientalmente sustentável para mitigar as emissões de CO2 e geração de biomassa para obtenção de bioprodutos de alto valor agregado como os biocombustíveis. Na digestão anaeróbia da biomassa de microalgas a adição de um cosubstrato rico em carbono pode facilitar o processo de produção de biogás. O glicerol possui alta concentração de carbono orgânico e é solúvel em água. Neste sentido, a combinação de ambos os substratos pode solucionar um dos principais problemas para o processo de digestão, que reside no equilíbrio da razão (C/N). Co-digestão anaeróbia consiste na digestão anaeróbia de uma mistura de dois ou mais substratos com composições complementares. O objetivo do estudo foi avaliar a geração de biogás através da co-digestão anaeróbia de biomassa de Spirulina sp. LEB 18 e glicerol bruto. Para a realização do estudo foram construídos e operados sete biorreatores com volume útil de 1,5 L, alimentados com 5, 6, 10, 15 e 20 g.L -1 da mistura de biomassa de Spirulina e glicerol. A adição de diferentes quantidades de glicerol (5 e 10 g.L -1 ) foi utilizada como um suplemento na digestão anaeróbia em sistema de batelada. A razão C/N variou de 3,3×103 a 23,7. Os ensaios foram realizados a 35 °C, em reatores equipados com sistema de coleta de gás, alimentação e retirada do efluente líquido, operados em batelada sequencial. O efluente líquido dos reatores foi analisado quanto ao pH, nitrogênio amoniacal e alcalinidade. O volume de biogás produzido diariamente foi medido em gasômetro de frasco invertido. Em todos os ensaios, os valores médios de pH variaram de 7,0 a 7,3 e nitrogênio amoniacal de 62,02 a 1100,99 mg.L-1 . A alcalinidade do efluente variou entre 1133,37 e 3578,98 mg.L-1 CaCO3. Em todos os ensaios com adição de glicerol houve incremento na produção específica de biogás (0,16 – 0,24 d -1 ) quando comparado ao ensaio em que somente biomassa microalgal era alimentada no processo (0,03 L.d-1 ), demonstrando ser esta uma alternativa interessante para a produção de biocombustível e concomitante agregação de valor ao glicerol residual da produção de biodiesel.

Tratamento didático do erro na produção escrita dos alunos do 1.º ciclo do ensino básico : um estudo de caso

Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e Ensino do 1.º Ciclo do Ensino Básico.