The aim of this work is to use cheap raw materials, such as kaolin and ball clay, for the manufacture of ceramic membranes for application in effluent treatment from textile industry and to evaluate the influence of sintering temperature in the structural and morphological characteristics of those membranes. The ceramic mass was characterized by X-ray diffraction and thermal analysis. The membranes were characterized by scanning electron microscopy, Hg porosimetry, and water permeability with desalinated water. The variation in the sintering temperature directly affected the structural and morphological characteristics of the membranes. The increase in sintering temperature of the membranes has raised the average pores diameter from 0.116 to 0.179 µm but decreased the porosity of the membrane, from 40.30 to 25.16% for temperatures from 900 to 1100°C, respectively. The reduction in porosity of the membrane affected the water permeated flux and decrease from 35.82 Kg/h·m2(at 1000°C) to 15.68 Kg/h·m2(at 1100°C). All the membranes have been applied with success in the effluent treatment from textile industry, resulting in the decrease in turbidity and discoloration, reaching approximately 100% of rejection of solid particles.
Among the vast applications in which the α-alumina can apply, the literature has reported researches which aim to achieve better features of these materials varying the obtainment methodology and some post-obtainment techniques. Thus, this paper aims to evaluate how different milling time lengths of 15, 30, 45 and 60 minutes alter the structure and morphology of α-alumina powders synthesized by combustion reaction. The time and temperature of the combustion reaction were evaluated during the synthesis of the alumina. The samples of non-milled and milled alumina were characterized by XRD and particle size analysis. The results showed that the maximum achieved temperature of reaction was 598°C. The milling time length variation did not alter the stable α-Al2O3majority crystal phase present in all samples. The average particle diameter was reduced from 23.3 to 10.5 μm comparing the non-milled and the sample milled for 60s.
RESUMOEsse trabalho tem como objetivo obter membranas cerâmicas assimétricas para aplicação em processos de microfiltração e avaliar a influência do tempo de deposição (5 e 10 s) de uma dispersão de argila sobre um suporte tubular de alumina comercial e bentonita. O suporte tubular foi caracterizado por microscopia ótica e eletrônica de varredura e por porosimetria. A membrana assimétrica foi caracterizada por microscopia eletrônica de varredura e por porosimetria. Os resultados mostraram suportes porosos com espessura de 1092mm, diâmetro médio de poro de 0,99 mm e porosidade de 39%. A membrana assimétrica foi obtida com sucesso para os tempos de deposição avaliados, sendo classificada para aplicações em processos de microfiltração atingindo diâmetro médio de poro de 0,25 mm e porosidade de 35%.Palavras-chave: membrana assimétrica, membrana tubular, deposição, microfiltração. ABSTRACTThis paper aims to obtain asymmetric ceramic membranes for application in microfiltration processes and evaluate the influence of the deposition time (5 and 10 s) of a clay dispersion on commercial alumina and bentonite tubular support. The tubular support was characterized by optical and scanning electron microscopy and porosimetry. The asymmetric membrane was characterized by scanning electron microscopy and porosimetry. The results showed porous substrates with thickness of 1092mm, average pore diameter of 0.99 mm and porosity of 39%. The asymmetric membrane was successfully obtained for the evaluated deposition times, being classified for microfiltration processes applications.Keywords: asymmetric membrane, tubular membrane, deposition, microfiltration. INTRODUÇÃOA tecnologia de separação com membranas tem sido amplamente utilizada em biotecnologia, indústrias farmacêuticas e de alimentos ou para tratar outros efluentes industriais. Essa tecnologia oferece uma ampla gama de procedimentos capazes de recuperar, concentrar ou purificar solventes valiosos em todos estes campos científicos [1].As membranas inorgânicas apresentam vantagens sobre as orgânicas por poderem atuar sob condições em que as orgânicas apresentam restrições, como por exemplo, na presença de solventes, elevadas temperaturas e pressões. Procedimentos agressivos de limpeza química e/ou mecânica e esterilização são geralmente empregados em membranas e são propensos a causar danos na estrutura da membrana especialmente para as membranas orgânicas [2]. Entretanto, as membranas inorgânicas são normalmente mais caras do que as orgâ-nicas habituais. Nesse sentido, novas pesquisas com membranas usando materiais cerâmicos de custo mais baixo devem difundir o uso da tecnologia de membranas, especialmente para países emergentes, onde muitos problemas ambientais podem ser resolvidos com a utilização de membranas.
Resumo: Diante da diversidade na possibilidade de matérias-primas utilizadas na obtenção de membranas cerâmicas, a literatura tem apresentado crescimento no número de pesquisas para diversas áreas nas quais se enquadra essa tecnologia. Dessa forma, esse trabalho tem como objetivo obter a camada filtrante de membrana assimétrica, com argila, para aplicações em processos de microfiltração. O suporte da membrana foi obtido em geometria tubular através da mistura de alumina comercial e bentonita, já a camada filtrante foi obtida com argila. As massas cerâmicas para confecção do suporte e da camada filtrante foram caracterizadas por espectroscopia e difração de raios X. Tanto o suporte quanto a membrana foram caracterizados por microscopia óptica, microscopia eletrônica de varredura, porosimetria por intrusão ao mercúrio e análises de fluxo. Os resultados mostraram que a argila é eficaz na produção da camada filtrante da membrana, permitindo excelente adesão e homogeneidade de superfície, com espessura na faixa de 42 mm, atingindo fluxo de 90,83 L/h.m 2 e classificação para aplicações em processos de microfiltração.Palavras-chave: membrana, assimétrica, argila, microfiltração. IntroduçãoA tecnologia de membranas engloba um vasto campo dentro da ciência devido sua aplicação ser voltada para diversos setores industriais, laboratoriais, da medicina, de alimentos, entre outros. Podendo ser produzidas com materiais orgânicos ou inorgânicos, as membranas inorgânicas destacam-se por poder serem aplicadas em condições nas quais as orgânicas apresentam restrições como na realização de limpeza com ácido, cloro e solventes, não poder ser esterilizadas a temperatura elevada e exibir um tempo menor de vida quando comparadas as inorgânicas 1 . De acordo com o diâmetro de poro e porosidade atingidos pela membrana, esta pode ser classificada em diferentes processos de separação. Um desses processos é a microfiltração. Esse processo de separação com membranas é o mais próximo da filtração clássica. A microfiltração utiliza membranas porosas com poros na faixa entre 0,1 e 10 μm e porosidade variando de 5 a 70%. Dentre algumas aplicações recentemente reportadas na literatura fazendo-se o uso de microfiltração estão: separação de proteína do leite, Carpintero- A maioria das membranas cerâmicas são produzidas por óxidos, como por exemplo, óxido de alumínio, Ren et al.10 ; de zircônia, Zhu et al.11 e de titânio, Chang et al. 12. Esses óxidos são materiais nobres que encarecem a produção da membrana. Porém, a literatura tem reportado resultados satisfatórios para a aplicação a que se destina a membrana fabricada com argilas 4 . O termo argila é empregado para designar um material inorgânico natural, de granulometria fina, com partículas micrométricas que apresenta comportamento plástico quando adicionada uma determinada quantidade de água 13 . As argilas são constituídas pelos minerais argilosos de origem secundária (minerais secundários) e pelos minerais não-argilosos de origem primária (minerais primários), às vezes denominados de "impur...
The search of variations in the methodology for obtaining nanoferrites has attracted the interest of researchers in search of better results with regard to the structure and morphology of these materials. This study evaluates the effect of microwave power (50 and 70 W) in the structural and morphological characteristics of NiZn ferrite, using aniline as a fuel for combustion reaction. The aluminas were characterized by X-ray diffraction and scanning electron microscopy. The results showed that only the variation in microwave power is sufficient to change the structure of nanoferrites. The sample synthesized in power of 50 W was presented monophasic, illustrating the ferrite phase with crystallite size of 50.04 nm; and for 70 W, it was appeared, besides the ferrite phase, hematite and zinc oxide with a crystallite size of 17.07 nm. The morphology did not change significantly, the nanoferrites showed particles with similar geometry.
Given the opportunities that aluminas present in relation to the broad field of applications to which they refer, the literature has reported great diversity in methodology to obtain these materials in the search of generating the best properties. In this way, the aim of this work is to evaluate the use of different citric acid and metallic cation ratio on the structural and morphological characteristics of the alumina synthesized by Pechini method and calcined at 1100°C. The samples were characterized by X-ray diffraction, thermal analysis, particle size and scanning electron microscopy. The results showed a large amount of loss of mass after pyrolysis. The α-alumina phase was achieved for the two studied ratio reaching values for crystallite size of 41.4 and 52.5 nm, crystallinity of 88 and 91.2%, agglomerates size of 12.3 and 14μm, for the synthesized samples 2:1 and 3:1, respectively. According to the SEM images, the changes in the citric acid: metallic cation ratio did not significantly modify the morphology of the alumina.
Through different field of application and productive growth that membrane technology has been presented in the last years, the aim of this work is to prepare and characterize anisotropic porous ceramic membrane. The membrane were done with alumina, prepared by combustion reaction in microwave oven from urea as combustible and after deposited on support based on a commercial alumina. The results showed that it was obtained α-alumina as unique phase with average agglomerate size of 10µ and surface area of 33 m2/g. The alumina morphology was constituted by pre-sintering particles with hard agglomerates and/or aggregates. In relation to the membranes, it was observed a longitudinal section without cracks and uncovers support surface, also it can be observed grain formation well distributed and a layer of alumina with approximately 35.25µm. In relation to the permeate flux, the membrane presented initially values relatively high that is decrease with the permeation time, due to adsorption of water in the internal surface of the pores of the membrane, experiencing a decrease in size.
The aim of this study is to evaluate the effect of temperature during the synthesis of alumina by combustion in a muffle furnace. The alumina was characterized by X-ray diffraction, particles size distribution and scanning electron microscopy. The results showed that the synthesis temperature of the alumina can affect the structure of the produced samples. The size distribution of the median particle diameter reached higher value for the alumina synthesized at 500°C with 16.07 μm, the range of the total distribution of particles is introduced to the large alumina synthesized 500 and 600°C and close synthesized when 700 and 800°C. The phase of the alumina was identified only after the synthesized sample at 800°C with crystallite size of 22.16 and 6.75 μm synthesized samples 800 and 900°C, respectively. With respect to morphology, increased synthesis temperature was not enough to significantly change.
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