Resumo Novos depósitos de argilas esmectíticas foram descobertos no estado da Paraíba, Brasil, melhorando a questão da escassez das argilas de melhor qualidade. Estudos mostram que o teor de umidade, tempo de cura e capacidade de troca de cátions de bentonitas aditivadas com carbonato de sódio influenciam diretamente na reologia de dispersões em meio aquoso. Sendo assim, este trabalho objetivou analisar a influência da variação de umidade e tempo de cura nas trocas catiônicas de argilas bentoníticas para fluidos de perfuração aquosos. As argilas foram beneficiadas por hidrociclonagem e caracterizadas física, química e mineralogicamente. Em seguida, foram aditivadas com carbonato de sódio variando o teor de umidade e o tempo de cura. A capacidade de troca de cátions foi determinada antes e após o processo de aditivação. As propriedades reológicas e de filtração foram determinadas por meio de viscosidades aparente e plástica e o volume de filtrado. Os resultados permitiram concluir que o tempo de cura e teor de umidade tem influência na capacidade de troca catiônica e nas propriedades reológicas e de filtração. Após 15 dias de cura das argilas, houve decréscimo das capacidades de troca de cátions e das propriedades reológicas e de filtração.
This study aimed to evaluate the potential of clays from the State of Paraíba to be used for medicinal, therapeutic and aesthetic treatments. The samples were characterized by X-ray diffraction, X-ray fluorescence chemical composition, thermogravimetry, differential thermal analysis, laser diffraction granulometric analysis, cation exchange capacity, and antimicrobial activity. Based on the study, it was concluded that the clays from the State of Paraíba had properties similar to those of commercial clay. The antimicrobial evaluation revealed that the samples showed no activity against the three bacterial strains of clinical interest: Staphylococcus epidermidis ATCC 12 228, Staphylococcus aureus ATCC 25 923, and Escherichia coli ATCC 25 922. Finally, it was concluded that the clays studied have the potential for technological applications in medicinal, therapeutic, and aesthetic treatments, and as raw material for obtaining biomaterials, due to their stability and biological safety.Este trabalho teve como objetivo avaliar a potencialidade das argilas do estado da Paraíba, visando suas aplicações em tratamentos medicinais, terapêuticos e estéticos. As amostras das argilas foram caracterizadas pelas técnicas de difração de raios X, composição química por fluorescência de raios X, termogravimetria, análise térmica diferencial, análise granulométrica por difração a laser, capacidade de troca catiônica e atividade antimicrobiana. Com base no estudo, concluiu-se que as argilas do estado da Paraíba apresentaram propriedades similares à argila comercial. A avaliação antimicrobiana revelou que as amostras não apresentaram atividade frente a três cepas bacterianas de interesse clínico: Staphylococcus epidermidis ATCC 12 228, Staphylococcus aureus ATCC 25 923 e Escherichia coli ATCC 25 922. Por fim conclui-se que as argilas estudadas possuem potencial tecnológico para aplicações em tratamentos medicinais, terapêuticos, estéticos e como matéria-prima para obtenção de biomateriais, em virtude da sua estabilidade e segurança biológica. Palavras-chave: argilas, biominerais, caracterização, tratamento medicinal.
In Brazil, bentonite clays are not naturally sodic and it is an industrial practice the sodium additivation, since sodium ion expands their lamellae allowing a larger amount of water to penetrate. The objective was to analyze the influences of the use of sodium carbonate on the clay during the additivation process, the moisture content and the cure time on cation exchange and viscosity of bentonite clay dispersions for water-based drilling fluids, since there is a shortage of studies on this subject. Newly discovered bentonite clays in Paraíba State, Brazil, were chemically, physically and mineralogically characterized and were additivated with sodium carbonate in aqueous solution (process 1) or in powder form (process 2). Samples with 25% to 60% of moisture (dry basis) were prepared and submitted to cure times of 7 to 45 days. Process 1, as expected, showed better results of cation exchange capacity, viscosity and filtrate volume. The ideal cure time was 15 days. After this period there was a reversal of the cation exchange reactions.
The physicochemical characteristics of cations may be able to modify the rheological properties of bentonite clays, such as their loads, exchangeable cation sizes adsorbed on clay minerals, hydration behaviors and different intercalations with the bentonite structural layer effect of the cations present on the rheology of dispersions of bentonite clays. In this way, the objective was to study the influence of Ca2+ on the rheological and filtration properties of dispersions of new occurrences of bentonite clays from the State of Paraíba, Brazil, in aqueous drilling fluids. Four bentonite clays were selected, being characterized chemically, physically and mineralogically. Sodium carbonate was then added to the clays, and the rheological and filtration behavior of their dispersions were studied. The results showed the direct influence of the Ca2+ present and its implications, resulting from physicochemical interactions, on the rheological and filtration properties of dispersions of bentonite clays.
New deposits of bentonite clays have been discovered in the Brazilian State of Paraíba; the most recent was at the municipality of Olivedos. Recent studies have discovered the presence of high levels of non-clay minerals that can produce unsatisfactory results when attempting to use these clays in drilling fluids. In order to make them suitable for this purpose, the MgO and CaCl 2 as chemical additives were used and their influences on the rheological properties of these clays were analyzed, using an experimental planning technique and statistical analysis. The samples were obtained using experimental modeling by the delineation of mixtures technique; first, the clays were transformed with sodium carbonate and then dosed with MgO and CaCl 2 . The rheological properties, apparent viscosity (AV) and plastic viscosity (PV) were determined according to the Petrobras standard (AV≥15 cP; PV≥4 cP). The results showed that the values of AV and PV increased considerably and that MgO was the additive that contributed most to the improvement of these properties, making these additives suitable for use in water-based drilling fluids. ResumoNovos depósitos de argila bentonítica foram descobertos no estado brasileiro da Paraíba, sendo o mais recente no município de Olivedos. Estudos recentes descobriram a presença de altos níveis de minerais não argilosos que podem produzir resultados insatisfatórios ao tentar usar essas argilas em fluidos de perfuração. Para torná-los adequados para esse fim, utilizaram-se MgO e CaCl 2 como aditivos químicos e analisaram-se suas influências nas propriedades reológicas dessas argilas, utilizando técnica de planejamento experimental e análise estatística. As amostras foram obtidas utilizando modelagem experimental pela técnica de delineamento de misturas; inicialmente as argilas foram transformadas com compostos de sódio e posteriormente dosadas com MgO e CaCl 2 . As propriedades reológicas, viscosidade aparente (AV) e viscosidade plástica (PV), foram determinadas de acordo com a normativa da Petrobras (AV≥15 cP; PV≥4 cP). Os resultados mostraram que os valores de AV e PV aumentaram consideravelmente e que o MgO foi o aditivo que mais contribuiu para a melhoria dessas propriedades, tornando-os adequados para uso em fluidos de perfuração à base de água. Palavras-chave: bentonitas de Olivedos, aditivos, fluidos de perfuração.
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