Navegando por Assunto "Caulim duro"

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Acesso aberto (Open Access)
Avaliação da formação zeolítica em sínteses com diferentes proporções de Si/Al via processo hidrotermal a partir de caulim durp (flint)
(Universidade Federal do Pará, 2023-02-23) FERREIRA, Aline Lopes; PINHEIRO, Alice dos Prazeres; http://lattes.cnpq.br/6671972168040423; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
The zeolite synthesis is composed of several reactional factors, in which changing a condition can significantly modify the intensity trend of the zeolite crystals or even the type of zeolite formed. In this context, this work aims to explore the change in the Si/Al ratio in different time periods and analyze the formed product. Initially, the characterization of hard kaolin was carried out through FRX, DRX, MEV, TG, DTG and DSC analyses. Subsequently, the hard kaolin was calcined at 650 °C for 2 hours, with the aim of transforming the starting material into metakaolinite, facilitating the restructuring into zeolite in the reaction medium of the dynamic hydrothermal process. Altogether, 7 hydrothermal syntheses with different Si/Al ratios were carried out, each lasting 6 hours. In each synthesis, aliquots were removed every half hour and filtered, the liquid of which was used to carry out the titration, while the particulate material from the period of 1, 2, 4 and 6 hours was applied for verification in the X-Ray Diffractogram (DRX) and MEV. In all products, the crystalline phases referring to zeolite A, sodalite and in some points of faujasite and cancrinite were observed. In view of the data obtained, it was verified that all the compositions used had satisfactory results with zeolite formation from 1 hour of synthesis, that is, a short period of time. Furthermore, it was possible to verify in a visible way, through the intensity of the peaks and appearance or disappearance of zeolite types, the interference of time and the proportion of Si/Al in the medium. In addition to the XRD, the dendrogram analysis was used in order to identify clusters, that is, which products had similar characteristics, being able to analyze intervals of better formation. The MEV was carried out with the 1-hour material, verifying the characteristic morphology of zeolite A and sodalite, mainly in the proportions of Si/Al=1 and 1,5. The concentration of NaOH in the medium, verified by titration, showed little consumption of this reagent throughout the synthesis. However, it was concluded that the reaction conditions applied to the hard kaolin showed the capacity to form zeolites, allowing the verification of the formation.
Acesso aberto (Open Access)
Caracterização mineralógica e geoquímica e estudo das transformações de fase do caulim duro da região do Rio Capim, Pará
(2003-12) CARNEIRO, Bruno Santana; ANGÉLICA, Rômulo Simões; SCHELLER, Thomas; CASTRO, Elton Anderson Santos de; NEVES, Roberto de Freitas
The Capim region (Pará State, northern Brazil) is the most important kaolin district in the Amazon region, with the largest Brazilian reserves of high whiteness kaolin for the paper coating industry. The main ore (soft kaolin horizon) is located at a depth of about 20 m, being covered by a hard, iron-rich kaolin level, also called flint or semi-flint kaolin, besides a sandy-clay overburden. The beneficiation of this kaolin produces large volumes of wastes, composed mainly of coarse-grained kaolinite, deposited in basins that occupy extensive areas. The main objective of this work is to carry out mineralogical and geochemical studies of the hard kaolin, and to evaluate its thermal transformations through calcination up to 1500 oC. The results show a mineralogical composition dominated kaolinite. The evaluated thermal transformations allows us to describe a series of chemical reactions from kaolinite to metakaolinite and further development of spinel, cristobalite and mullite. For the two analyzed samples, such transformations can start at different temperatures as a result of the different chemical compositions, mainly the iron contents.