Remoção do alcatrão de correntes de gaseificação de biomassa: processos e catalisadores

Biomass gasification is a technology that has attracted great interest in synthesis of biofuels and oxo alcohols. However, this gas contains several contaminants, including tar, which need to be removed. Removal of tar is particularly critical because it can lead to operational problems. This review discusses the major pathways to remove tar, with a particular focus on the catalytic steam reforming of tar. Few catalysts have shown promising results; however, long-term studies in the context of real biomass gasification streams are required to realize their potential.

Tratamentos térmico e químico para remoção de óxidos alcalinos de cinzas de capim elefante

Elephant grass ash (EGA) was produced at 700 °C, with two different treatments: hot water (EGAhw) or acid solution (EGAas). The efficiency of the treatments at removing the potassium oxide was evaluated with the aim of using the EGA as a pozzolanic mineral addition for cement-based composites. Characterizations were carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), pozzolanic activity by electric conductivity and application of the kinetic-diffusive model. The analysis evidenced that the chemical treatment was more efficient for removing potassium oxide. The pozzolanic activity test and the kinetic parameters for the EGAas indicated that this ash is suitable for cement-based composites.

Avaliação da remoção de fármacos e de desreguladores endócrinos em águas de abastecimento por clarificação em escala de bancada

In this work, the efficiency of clarification treatment (coagulation, flocculation and sedimentation) with polyaluminum chloride (PAC) and aluminum sulfate (SA) as coagulants was evaluated in the removal of 7 microcontaminants (diclofenac - DCF, sulfamethoxazole - SMX, ethinylestradiol - EE2, bisphenol-A - BPA, estradiol - E2, estrone - E1 and estriol - E3) in water of low and high turbidity. The clarification treatment led to poor removal rates (40% at most) for all microcontaminants except SMX which exhibited intermediate removal efficiency (67 to 70%). Overall, PAC application yielded better performance compared to SA.

Análise exploratória aplicada a espectros de reflexão total atenuada no infravermelho com transformada de Fourier (ATR-FTIR) de blendas de biodiesel/diesel

In this study, hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to classify blends produced from diesel S500 and different kinds of biodiesel produced by the TDSP methodology. The different kinds of biodiesel studied in this work were produced from three raw materials: soybean oil, waste cooking oil and hydrogenated vegetable oil. Methylic and ethylic routes were employed for the production of biodiesel. HCA and PCA were performed on the data from attenuated total reflectance Fourier transform infrared spectroscopy, showing the separation of the blends into groups according to biodiesel content present in the blends and to the kind of biodiesel used to form the mixtures.

Adsorção de alfa-lactalbumina do soro de leite em hidroxiapatita: efeito do pH e da temperatura e análise termodinâmica

The nutritional and functional benefits offered by whey protein α-lactalbumin justify the great interest in its manufacture in large quantities at a high purity level. Hydroxyapatite is a calcium phosphate material able to adsorb proteins and can be synthesized at low production cost. Therefore, this work evaluated the adsorption of α-lactalbumin on hydroxyapatite using solid-liquid phase equilibrium data reported as adsorption isotherms. Van't Hoff's thermodynamics analysis showed that the adsorption process is entropically driven.

Remoção do ácido mefenâmico em água utilizando carvão ativado em pó, lama vermelha e oxidação com cloro

The use of activated carbon powder (ACP), red mud and oxidation with chlorine to remove mefenamic acid in water are described, aimed at their application as a complement to sewage treatment processes in Brazil. A study on the behavior of mefenamic acid in water was performed by evaluating its dissolution for different concentrations and times. Subsequently, the optimal conditions for removal of mefenamic acid were investigated using ACP adsorption at different pH and concentrations, and red mud adsorption using different pH. The utilization of different pH and times was also investigated to establish the ideal conditions for chemical oxidation of the drug. Among the different conditions studied, the best condition for drug removal by ACP and red mud were 100% and 96%, respectively, while the best condition for chemical oxidation occurred using solutions with pH 6 and 7 and reaction times of 30 and 60 minutes.

APLICAÇÃO DE ÓXIDOS DE FERRO NANOESTRUTURADOS COMO ADSORVENTES E FOTOCATALISADORES NA REMOÇÃO DE POLUENTES DE ÁGUAS RESIDUAIS

New techniques for treating wastewater, particularly the removal or degradation of organic pollutants and heavy metals, among other pollutants, have been extensively studied. The use of nanostructured iron oxides as adsorbent and photocatalyst for the removal of these contaminants has proved a promising approach, not only because of their high treatment efficiency, but also for their cost-effectiveness, having the flexibility for in situ and ex situ applications. In this review, we briefly introduced the most used kinds of iron oxide nanoparticles, some synthesis techniques for iron oxide nanostructure formation, their potential benefits in environmental clean-up, and their recent advances and applications in wastewater treatment. These advances range from the direct applications of synthesized nanoparticles as adsorbents for removing toxic contaminants or as catalysts to oxidize and break down noxious contaminants (including bacteria and viruses) in wastewater, to integrating nanoparticles into conventional treatment technologies, such as composite photocatalytic filters (membranes, sand and ceramic) that combine separation technology with photocatalytic activity. Finally, the impact of nanoparticles on the environment and human health is briefly discussed.

DETERMINAÇÃO DO TEOR DE BIODIESEL EM DIESEL EMPREGANDO O ENSAIO COLORIMÉTRICO DO ÁCIDO HIDROXÂMICO

The aim of this paper was to use colorimetric assays for hydroxamic acid to quantify the biodiesel content in diesel and compare it with the traditional method (infrared spectroscopy, using the EN 14078 method). Samples were prepared from B2 to B10 with two kinds of diesel - S500 (red) and S50 (yellow) - to obtain two calibration curves. Through statistical methods it was shown that the slopes of the straight lines obtained for the different types of diesel were the same. Thus, the type of diesel did not influence the results of the colorimetric assay for hydroxamic acid. Real samples collected from gas stations were analyzed by both methods (colorimetry and EN 14078). By applying Student's t-test it was concluded that the methods could be considered statistically equivalent. Therefore, it was confirmed that the colorimetric assay for hydroxamic acid is suitable for detecting and quantifying the content of biodiesel in biodiesel/diesel blends and can also be easily adapted to field analyses.

DESENVOLVIMENTO DE ENSAIO PARA ANÁLISE QUALITATIVA DE BIODIESEL EM MISTURAS DIESEL-BIODIESEL PARA APLICAÇÃO EM POSTOS REVENDEDORES DE COMBUSTÍVEIS

In this study, we developed a method for the visual detection of biodiesel in petrodiesel-biodiesel (BX) blends through the aminolysis of the methyl or ethyl esters of fatty acids that are found in biodiesel and that are absent from diesel and vegetable oils. This method is based on three reactional stages, which produce a dark red and easily visualized complex in the presence of biodiesel. In the absence of biodiesel, there is no dark red coloring, whereas in the presence of diesel or vegetable oil, there is a light red to yellow coloring. This simple, practical, inexpensive, and effective procedure may be applied by petrol stations to guarantee to consumers and resellers the presence of biodiesel in diesel blends, regardless of the BX blend's initial coloring or of the sulfur found in the diesel. In short, it ensures a safe fuel tank fill-up with BX blend.

TRATAMENTO DA VINHAÇA POR ADSORÇÃO EM CARVÃO DE BAGAÇO DE CANA-DE-AÇÚCAR

The aim of this study was to develop an effective and economically viable technology for the treatment of vinasse, prior to its disposal in the soil for fertirrigation, aiming this way at reducing the environmental impacts generated by inadequately discarding this effluent. The primary treatment of vinasse by adsorption was evaluated. Adsorbents were prepared from sugar cane bagasse and their efficiency evaluated in relation to the treatment of vinasse. The process of preparation of activated carbon consisted of carbonizing bagasse at different temperatures followed by chemical activation with NaOH. The carbon samples obtained by solely carbonizing sugar cane bagasse were more efficient for removing turbidity of vinasse than samples activated with NaOH. The sample carbonized at 800 °C was the most efficient for removing turbidity of wastewater (83%). During a process of adsorption of vinasse in two stages, it was possible to obtain color removal, turbidity and COD of approximately 76, 85 and 69%, respectively. After the adsorption step of vinasse, the solid waste generated in the second stage of adsorption can be burned in the boilers of the power plant itself, affording an energy of 4606 cal g-1.

Remoção de íons metálicos de soluções aquosas, por apatitas sintéticas, usando o método de troca iônica em coluna

Foi investigada a remoção dos íons Al3+, Mn2+, Cu2+, Zn2+, Cd2+ and Pb2 +, em solução aquosa, por apatitas sintéticas usando o método de coluna. Sob as mesmas condições, hidroxiapatitas foram mais seletivas para a remoção de cátions que carboapatitas. Usando hidroxiapatita, a capacidades de troca aumentaram na seguinte ordem: Mn2+ < Zn2+ < Cu2+ < Cd2+ < Al3+ < Pb2+. A seqüência acima é similar a obtida em trabalhos prévios, usando o método de batelada. Análises de DRX e IV indicaram a formação de uma fase única atribuída a uma Pb-apatita.

Hidrogeneoftalato de potássio como molécula modelo para estudos de adsorção sobre TiO2

Este trabalho teve por objetivo utilizar o hidrogenoftalato de potássio como molécula modelo para estudos de adsorção em TiO2. Os resultados de adsorção do hidrogeneoftalato sobre TiO2 se ajustaram aos modelos de adsorção propostos por Langmuir e Freundlich, sendo que o modelo de Freundlich descreveu melhor o fenômeno. A adsorção foi função da temperatura e a capacidade de adsorção aumentou de 2,4 para 4,5 mg.g-1 quando se elevou a temperatura de 20 para 30ºC.

Processos diurnos e noturnos de remoção de NO2 e NH3 atmosféricos na região de Araraquara-SP

Os óxidos de nitrogênio e a amônia são os mais importantes compostos gasosos nitrogenados emitidos para a atmosfera e possuem grande interesse ambiental. Na atmosfera, esses compostos podem sofrer diversas reações resultando em mudanças nas propriedades químicas e físicas da atmosfera. Atividades humanas, principalmente relacionadas com produção de alimentos, energia e uso de fertilizantes têm aumentado as emissões dessas espécies nitrogenadas para o ambiente, causando distúrbios no seu ciclo natural. Com o objetivo de avaliar as variações dos níveis de concentração e inferir sobre os processos de remoção de compostos de nitrogênio da atmosfera na região de Araraquara, foram feitas determinações em paralelo de amônia (NH3) e dióxido de nitrogênio (NO2). Os resultados de concentração mostraram a estreita correlação entre esses compostos na atmosfera, que sugerem diferentes processos de remoção em diferentes épocas do ano.

Obtenção da fase peroviskita via microemulsão

Pequenas partículas de fase peroviskita de BaMnO3 foram preparadas por dois métodos: a rota da coprecipitação convencional (RCC) e o método convencional de microemulsão (MCM). As técnicas instrumentais utilizadas para caracterizar as amostras foram: microscopia eletrônica de varredura (SEM), difratometria de raios X (XRD), termogravimetria (TG) e análise térmica diferencial (DTA). A síntese de materiais em sistemas coloidais auto-organizados tem por objetivo aumentar a homogeneidade de tamanho e forma das partículas. Nos últimos anos aumentou a busca por materiais mais uniformes visando o aperfeiçoamento da microestrutura. A rota de microemulsão é um método alternativo para a síntese de materiais porque permite o controle da relação entre as concentrações de água e do tensoativo, (w), o qual controla o tamanho das gotículas de microemulsão denominadas microreatores. Peroviskita pura obtida de microemulsão forma-se em temperatura menor do que a fase precipitada, e resulta.em partículas com distribuição de tamanho mais adequada, de aproximadamente 0,1 mm de diâmetro comparado com a média de 0,5 mm das partículas coprecipitadas.

Estudo da adsorção/dessorção de 2,4-D em solos usando técnica cromatográfica

Este trabalho estudou a adsorção e a desorção do herbicida ácido 2,4-Diclorofenoxiacético (2,4-D) em solo da região de Urbano Santos - MA. A região possui campos de cultivo de eucaliptos para obtenção de celulose. Para a limpeza dos campos, antes da plantação e nos primeiros 12 meses de plantio, são aplicados herbicidas, dentre os quais destacamos o 2,4-D. A isoterma de Freundlich foi utilizado como modelo para este estudo e a concentração de 2,4-D foi determinada por cromatografia líquida de alta eficiência (CLAE), acompanhada de ensaios de recuperação para garantir a confiabilidade dos dados obtidos na investigação de adsorção/dessorção. Os resultados indicaram que o 2,4-D apresenta maior adsorção à matéria orgânica do solo estudado, quando comparado a outros tipos de solo, o que pode resultar em pequena diminuição em sua tendência de lixiviação e de degradação microbiológica. Entretanto, este herbicida apresenta elevado potencial de lixiviação quando comparado a outros pesticidas.