Gelmires Araújo Neves

O estado da arte sobre o uso de resíduos como matérias-primas cerâmicas alternativas

Os residuos industriais e urbanos vem-se tornando um dos mais serios problemas que a sociedade moderna enfrenta. Sua deposicao de forma inadequada provoca a degradacao do meio ambiente e a contaminacao dos mananciais de agua e do solo. Por outro lado, tecnicos da industria cerâmica se deparam com a escassez de reservas de materias-primas de boa qualidade em locais economicamente viaveis de exploracao. Assim, este trabalho objetiva apresentar uma visao geral da possibilidade de utilizacao dos residuos industriais e urbanos como materias-primas cerâmicas alternativas, enfocando a industria cerâmica como uma fonte economicamente viavel e ecologicamente correta para reciclagem de residuos.

Utilization of kaolin processing waste for the production of porous ceramic bodies

The kaolin processing industry generates large amounts of waste in producing countries such as Brazil. The aim of this study was to characterize kaolin processing waste and evaluate its suitability as an alternative ceramic raw material for the production of porous technical ceramic bodies. The waste material was physically and chemically characterized and its thermal behaviour is described. Several formulations were prepared and sintered at different temperatures. The sintered samples were characterized to determine their porosity, water absorption, firing shrinkage and mechanical strength. Fired samples were microstructurally analysed by X-ray diffraction and scanning electron microscopy. The results indicated that the waste consisted of quartz, kaolinite, and mica, and that ceramic formulations containing up to 66% of waste can be used for the production of ceramics with porosities higher than 40% and strength of about 70 MPa.

Estudo de argilas usadas em cerâmica vermelha

The aim of this work was to characterize clays industrially used for the production of ceramic bricks. The clays were characterized by particle size distribution, Atterberg limits and chemical composition determination, X-ray diffraction and differential thermal and gravimetric analyses. Test specimens were prepared by extrusion and fired at 800, 900 and 1000 oC. Fired test specimens were characterized in terms of water absorption and mechanical strength. Commercially produced ceramic bricks were also characterized in terms of water absorption and mechanical strength. The results showed that clays had plasticity limits in the range indicated for brick clay industry and are composed by kaolinite, quartz, mica and feldspars, with some samples presenting goethite and silicon-aluminous hydroxide. The suitability to produce ceramic bricks using the studied samples could be determined by the characterization process.

Statistical design for recycling kaolin processing waste in the manufacturing of mullite-based ceramics

Mineral extraction and processing industries have been cited as sources of environmental contamination and pollution. However, waste recycling represents an alternative recovery option, which is interesting from an environmental and economic standpoint. In this work, recycling of kaolin processing waste in the manufacture of mullite-based ceramics was investigated based on the statistical design of mixture experiments methodology. Ten formulations using kaolin processing waste, alumina and ball clay were used in the experiment design. Test specimens were fired and characterized to determine their water absorption and modulus of rupture. Regression models were calculated, relating the properties with the composition. The significance and validity of the models were confirmed through statistical analysis and verification experiments. The regression models were used to analyze the influence of waste content on the properties of the fired bodies. The results indicated that the statistical design of mixture experiments methodology can be successfully used to optimize formulations containing large amount of wastes.

Desenvolvimento de nanocompósitos polipropileno/argila bentonita brasileira: I tratamento da argila e influência de compatibilizantes polares nas propriedades mecânicas

In this work, polypropylene/bentonite and polypropylene/compatibilizer/bentonite nanocomposites were prepared by the melt intercalation method, using a counter-rotating intermeshing twin-screw extruder attached to a Haake System 90 Rheometer. Initially the natural bentonite clay, from Boa Vista - PB, was subjected to a purification process and then treated with sodium carbonate. Further, it was treated with ammonium quaternary salt to obtain an organoclay. The clays were characterized, according to granulometric, by laser diffraction, chemical analysis, infrared spectroscopy - FTIR, and X ray diffraction - XRD. The granulometric and chemical analysis results showed that the purification process was effective for removing the coarse fractions and eliminating some accessory minerals. FTIR and XRD results showed that the ammonium quaternary salt was incorporated to the clay, confirming the organophilization. In the subsequent stage of this work, the bentonite organoclay was incorporated to both polypropylene (PP) and PP/compatibilizer (PPgAA and PPgMA are polypropylenes grafting acrylic acid and maleic anhydride, respectively). The formation of nanocomposites as well as the properties of PP/ORG (ORG - organoclay) and PP/compatibilizer/ORG mixtures were analyzed by XRD, MET and mechanical properties. XRD and MET results showed that the formation of interlayer/flocculated nanocomposites has occurred for PP/compatibilizer/ORG systems. The mechanical properties results showed that some mechanical properties (final elongation and toughness) have been considerably improved.

Kaolin processing waste applied in the manufacturing of ceramic tiles and mullite bodies

In the last few years, mineral extraction and processing industries have been identified as sources of environmental contamination and pollution. The kaolin processing industry around the world generates large amounts of waste materials. The present study evaluated the suitability of kaolin processing waste as an alternative source of ceramic raw material for the production of ceramic tiles and dense mullite bodies. Several formulations were prepared and sintered at different temperatures. The sintered samples were characterized to determine their porosity, water absorption, firing shrinkage and mechanical strength. The fired samples were microstructurally analysed by X-ray diffraction. The results indicated that ceramic tile formulations containing up to 60% of waste could be used for the production of tiles with low water absorption (~ 0.5%) and low sintering temperature (1150 °C). Mullite formulations with more than 40% of kaolin waste could be used in the production of bodies with high strength, of about 75 MPa, which can be used as refractory materials.

Argilas bentoníticas de Cubati, Paraíba, Brasil: Caracterização física-mineralógica

O Estado da Paraiba possui jazidas de bentonitas utilizadas comercialmente em uma vasta gama de setores tecnologicos. No entanto, esses jazimentos estao se exaurindo apos dezenas de anos de exploracao. Assim, este trabalho tem por objetivo a caracterizacao fisico-mineralogica de bentonitas recentemente descobertas no municipio de Cubati, PB. As amostras estudadas foram secas a 60 oC e caracterizadas por meio de fluorescencia de raios X, picnometria de He, determinacao da distribuicao de tamanho de particulas, difracao de raios X, analise termica diferencial e gravimetrica e microscopia eletronica de varredura. Os resultados evidenciaram que as amostras sao bentonitas policationicas, apresentando teores de MgO, CaO e K2O semelhantes aos de outras bentonitas sul-americanas e que sao constituidas por argilomineral esmectitico e por quartzo e caulinita. As amostras apresentaram fracoes de particulas abaixo a 2 μm variando entre 31 e 41%, estando, no entanto, em elevado estado de aglomeracao.

Análise da influência do tratamento de purificação no comportamento de inchamento de argilas organofílicas em meios não aquosos

As argilas bentonitas possuem importantes funcoes em fluidos de perfuracao nao aquosos. No entanto, impurezas presentes na argila e a escolha inadequada do sal quaternario utilizado no seu processo de organofilizacao podem comprometer a compatibilidade do sistema argila-fluido. Assim, este trabalho tem por objetivo analisar a influencia do tratamento de purificacao e dos sais quaternarios de amonio no comportamento de inchamento de argilas organofilicas em meios nao aquosos. A argila bentonita foi purificada atraves de procedimento de sedimentacao e as argilas organofilicas foram preparadas utilizando-se cloreto de alquil benzil amonio (Dodigen), cloreto de diestearil dimetil amonio (Praepagen), cloreto de cetil trimetil amonio (Genamim) e brometo de cetil trimetil amonio (Cetremide). As argilas organofilizadas foram caracterizadas por difracao de raios X e determinacao da distribuicao do tamanho de particulas e, em seguida, submetidas ao ensaio de inchamento de Foster em ester, parafina e oleo diesel. Os resultados mostram que o processo de purificacao foi eficiente na reducao de impurezas presentes na bentonita e que a argila organofilica purificada tratada com Praepagen e Genamim apresenta valores de inchamento de Foster em ester, oleo diesel e parafina superiores aos obtidos com argilas organofilicas sem purificacao (natural) e comercial.

Utilização do Resíduo do Beneficiamento do Caulim na Produção de Blocos e Telhas Cerâmicos

The miner and processing industries of kaolin are an important economic sector in the state of Paraiba, however, they generate a large amount of wastes, which are source of contamination and pollution of environment. This work has as aim the characterization of the kaolin processing waste and the evaluation of its suitability as an alternative ceramic raw material for the production of bricks and roof tiles. The waste was characterized by chemical composition determination, X-ray diffraction, differential thermal and gravimetric analyses, particle size distribution, and morphological analysis by electronic scanning microscopy. Several formulations were prepared and samples bodies were prepared by uniaxial pressing and by extrusion. The sample bodies were fired at different temperatures. Sintered samples were characterized in terms of water absorption and mechanical strength. The results showed that the waste is composed by quartz, kaolinite and mica and that is possible incorporations of up to 50% in formulations for the production of ceramics bricks and roof tiles.

Aplicação da cinza da casca do arroz em argamassas de assentamento

A cinza produzida pela queima da casca do arroz tem potencial para ser utilizada na confeccao de argamassas por possuir, em sua constituicao, alto teor de silica (SiO2), podendo ser utilizada tambem como material pozolânico. Esta pesquisa objetivou verificar a viabilidade da utilizacao da cinza da casca do arroz (CCA) em argamassas de assentamento. Realizou-se a caracterizacao quimica e mineralogica da CCA e se determinou o indice de atividade pozolânica. Para as argamassas foi determinado o indice de consistencia e, em seguida, confeccionados corpos de prova de referencia (sem CCA) e tambem com percentuais de 6, 9, 15, 20 e 30% de CCA, como substituicao parcial do cimento, para o traco 1:2:9, em massa, e ensaiados apos periodos de cura de 28, 63 e 91 dias para determinacao da densidade de massa no estado endurecido, absorcao de agua e resistencia a compressao simples. Os resultados mostram que a CCA apresenta pozolanicidade e os corpos de prova com incorporacao da CCA forneceram valores superiores aos de referencia com relacao as propriedades fisicas e mecânicas, devido a provavel ocorrencia das reacoes pozolânicas e que a utilizacao da CCA e viavel, tanto do ponto de vista tecnico quanto ecologico.