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Navegando por Assunto "Bentonita"

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    Argamassas para dessalinização de alvenaria mista de edifício histórico de Belém
    (Universidade Federal do Pará, 2013-09-05) LOUREIRO, Alexandre Máximo Silva; SANJAD, Thais Alessandra Bastos Caminha; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607; http://lattes.cnpq.br/8950586647715771
    In the historical monuments of Belém structural masonry, along with the foundations and pillars, are responsible for supporting the building (VASCONCELLOS, 1979). These masonry are made of stone and solid bricks with lime mortar setting and can present various pathologies among which stand out the action of salt efflorescence and moisture. These two agents cause detachment of layers, mortar spraying, the appearance of cracks in masonry, and whitish appearance (HENRIQUES, 1994; CHAROLA, 2000). The research has as main objective the identification, characterization and attenuation of salt efflorescence, through study of the masonry of the right transept of the Church of St. Alexandre, located in historic downtown of Belém- PA. For this, laboratory techniques were used in order to understand the favorable process conditions of salt efflorescence, the damage to the materials, the kinds of salts and which materials are effective for desalination. First was the mapping the masonry and mapping damage to verify the current situation and the most degraded areas. Was subsequently performed the physical, chemical and mineralogical characterization: 1) physical characterization by sieve analysis, trace analysis and analysis of the moisture content of the masonry, 2) chemical characterization through qualitative and quantitative testing of salts and 3) characterization mineralogy by X-ray diffraction. The X-ray diffraction was also used to evaluate the efficacy of four types of desalination mortars containing clay (bentonite and kaolin) and sand in different ratios. At the end of the study it was found that the suggested techniques for characterization and mapping of the masonry proved efficient and aided in the correct diagnosis of the existing problem. Moreover, the research showed which kinds of mortar are recommended to desalination of masonry damaged by salt efflorescence.
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    Avaliação da influência dos cátions Na+, Ca2+ e Mg2+ na desativação de Ca, Mg-Bentonitas
    (Universidade Federal do Pará, 2015-04-28) CARMO, Andre Luiz Vilaça do; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
    In Brazil there is no occurrence of sodium bentonite, because of that, companies that explore this mineral raw material using a denominated sodium activation process, which is the exchange of cations in the interlayer space by Na+. Through this process, the bentonite present considerable improvements in their properties rheologies. However, after some time, these properties decline, which has been called deactivation. Thus, the objective of this study was to evaluate the influence of cations Na+, Mg 2+ and Ca2+ in the bentonite deactivation. For this, three bentonite considered calcic, from the state of Paraíba, and a magnesian, coming from the state of Maranhão, were studied in its natural form, activated and washed. The mineralogical phases of the samples were identified by X-ray Diffraction (XRD), chemical composition by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and cations in the interlayer by Cation Exchange Capacity (CEC). The rheological properties’ study was carried out by swelling. The XRD patterns showed that the dioctahedral smectite is the dominant mineral phase. There was the improvement in swelling results of all bentonite after the sodium activation, as well as subsequent decrease in the swelling value over 95 days (deactivation). Only one of the bentonite remained activated. The swelling results of washed bentonite showed increased for approximately the first 35 days, with subsequent decrease. The chemical composition results showed that a small amount of Na+ is removed from the washed bentonite. Furthermore, these results indicate that not only Na+ influences the swelling, but also Ca2+ and Mg2+ cations.
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    Caracterização química, mineralógica e aplicações potenciais da bentonita associada a basaltos intemperizados da Formação Mosquito, Bacia do Parnaíba, Sul do Maranhão
    (Universidade Federal do Pará, 2010-03-01) PAZ, Simone Patrícia Aranha da; NEVES, Roberto de Freitas; http://lattes.cnpq.br/9559386620588673; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607; https://orcid.org/0000-0002-3026-5523
    In the city of Formosa da Serra Negra (Maranhão state, northern Brazil), extensive outcrops of weathered basalts are found, which show enough clay contents to be a potential bentonitic material. The basalts are related to the Jurassic Mosquito Formation (Parnaíba Sedimentary Paleozoic Basin). In this work these saprolites were referred as Formosa bentonite, and the main purpose was to characterize their mineralogical and chemical composition for further potential applications. X-ray diffraction results show that montmorillonite is the main mineral present along with minor amounts of hematite, K-feldspar, magnetite and kaolinite. The Formosa Bentonite was compared with four reference bentonites: Chocolate and Bofe (from the famous Paraiba state deposits), SWy-2 and SAz-1 (from the Clay Mineral Society). Although these bentonites have showed a wide chemical, mineralogy and texture variation, common for such material, the similarities were convincing to increase the expectations of a new Brazilian bentonite. The present montmorillonite was successfully pillared with aluminium polyhydroxications. Results showed that the pillarization process increased the basal spacing of the natural clay from 15.3 to 18.7 Å and the surface area from 55.9 to 180.3 m2/g, proper for catalytic and adsorption applications. Adsorption tests were also carried out for Cu2+ in aqueous solution using the natural and pillared Formosa Bentonite. Surprisingly, in the three evaluated process variables (pH, contact time and adsorption equilibrium) the natural bentonite exhibited a better adsorptive capacity in comparison with the pillarized one. This is of special value if one intends to use these bentonites in natura, for instance, for wastewater treatment. They are environmentally correct, economically viable and assure low cost.
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    Cristaloquímica de esmectitas dioctaédricas em bentonitas brasileiras
    (Universidade Federal do Pará, 2025-07-01) VEGA PORRAS, David Enrique; PAZ, Simone Patrícia Aranha da; http://lattes.cnpq.br/5376678084716817; https://orcid.org/0000-0002-5880-7638
    Bentonites are mineral inputs of great industrial interest due to the physicochemical properties of clay minerals from the smectite group. These properties, resulting from the complex crystal chemistry and small particle size of smectites, include various layer charge, swelling capacity, and cation exchange capacity. In Brazil, the main bentonite deposits are located in the municipality of Boa Vista, Paraíba, which accounts for >70% of the country’s production. However, the progressive depletion of these varieties has motivated the search for new deposits. Among them, the Formosa deposit, in the state of Maranhão, stands out. Although both the Boa Vista and, to a lesser extent, the Formosa bentonites have been extensively studied in their <2 μm or coarser fractions, the crystal chemistry of their smectites has not yet been fully elucidated. This is due not only to the typical chemical and structural complexity of smectites, but also to the difficulty of obtaining pure smectite phases and the interference of accessory minerals. In this context, this thesis presents a detailed study of the crystal chemistry of smectite from the Formosa deposit, comparing it with three commercial varieties from Boa Vista: Bofe, Chocolate, and Verde Lodo. The <2 μm, 0.1-2 μm, and <0.1 μm fractions were analyzed, with the latter being the main focus of the study. The analyses included XRD (Rietveld method), FTIR, TEM-EDS, SEM, XRF, AAS, TG, and Mössbauer spectroscopy. These smectites, previously described as montmorillonites, also exhibit significant tetrahedral layer charge. In fact, the four samples show a tetrahedral charge of approximately 0.15 per half unit cell, sufficient to induce swelling after the Hofmann-Klemen treatment. The octahedral symmetry of all four samples was trans-vacant, influenced by both the Fe content and the tetrahedral charge. The structural and chemical similarities between the Formosa and Boa Vista smectites, along with similar smectite content in the <2 μm and <0.1 μm fractions – as quantified by the Rietveld method – demonstrated that the Formosa deposit is a potential alternative to the Boa Vista bentonites.
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    Diferenciação catiônica de bentonitas por infravermelho: um estudo dos efeitos da hidratação dos cátions trocáveis
    (Universidade Federal do Pará, 2020-04-13) RODRIGUES, Andréia Oliveira; PAZ, Simone Patrícia Aranha da; http://lattes.cnpq.br/5376678084716817; https://orcid.org/0000-0002-5880-7638
    In the bentonite industry, the most common procedure for quality control of the ore and the sodium activation process is the swelling method. However, this tool is restricted only to the differentiation of the sodium and non-sodium types, not considering the other cationic varieties. The analysis of the composition of exchangeable cations requires laborious procedures, with daily cationic exchanges (between 3 and 6 days) and chemical analysis Via Humid, which would be unfeasible for this type of industry. Despite this, knowledge of the cationic type is of paramount importance, as it would help in the implementation of a technological route of better quality and efficiency of sodium activation. In this context, he sought in this work to establish cationic differentiation parameters for bentonites based on near and medium infrared spectroscopy for the investigation of hydration of exchangeable cations. Particle size distribution (DTP) and N2 BET adsorption-desorption isotherms were also used. Eleven smectites were studied, including one Mg-montmorillonite and two from the Clay Minerals Society repository: SWy-2 (Na-montmorillonite) and SAz-1 (Ca-montmorillonite). The clay fraction obtained by granulometric separation was characterized by FRX, DRX, CTC and PCZ. Previous heat treatment by drying at 105 ºC for 24 h and dehydration at 400 ºC for 2 h. Exchangeable cations and hydration influenced the absorption bands of water molecules in the near and medium spectral region, showing that they are strongly influenced by the size and charge of the ions (monovalent and divalent). The cationic differentiation was observed by the intensity of these bands. Absorptions close to 3620 cm-1 were attributed to water directly linked to cations, however, differentiation was only possible in samples dried at 105 ºC, because at this temperature they still remain hydrated. The reduction in the intensity of this band is due to the decrease in the water content, due to dehydration of the interlayer after heating to 400 ºC, which does not favor differentiation. The absorptions close to 3430 cm-1 were attributed to the adsorbed water molecules, as well as the complex band in 7072 cm-1, obtaining a spectrum, in descending order, Ca, Mg and Na. DRIFT spectroscopy in the nearby region was considered a simple, fast and low-cost analysis technique that allowed to distinguish different types of bentonites.
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    Ocorrência de uma nova bentonita brasileira nos basaltos intemperizados da formação Mosquito, bacia do Parnaíba, sul do Maranhão
    (2011-12) PAZ, Simone Patrícia Aranha da; NEVES, Roberto de Freitas; NEUMANN, Reiner; COSTA, Geraldo Magela da
    Extensive weathered basalt outcrops can be found in the vicinities of the Formosa da Serra Negra town, southern of Maranhão state, northern Brazil. They exhibit typical clay texture and an enormous potential to be used and explored as bentonite. This work deals with the chemical and mineralogical characterization of this material that has been named as Formosa Bentonite. The main following methods and analytical techniques were used: XRD, XRF, SEM, Mössbauer spectroscopy and CEC in total sample and after grain size separation. Two samples from the main Brazilian "Paraíba bentonites" (Chocolate and Bofe types) were used for comparison purposes. The results show that the Formosa bentonite exhibit some chemical and mineralogical differences in comparison with the two reference samples, although the main and most important feature is the presence of montmorillonite as the major mineral phase.
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    Quantificação mineralógica de bentonitas via DRX usando um método combinado Rietveld-Le Bail-Padrão Interno
    (Universidade Federal do Pará, 2020-04-09) VEGA PORRAS, David Enrique; PAZ, Simone Patrícia Aranha da; http://lattes.cnpq.br/5376678084716817; https://orcid.org/0000-0002-5880-7638
    In the bentonite industry ore quality control has been traditionally carried out using the swelling parameter, denominating those that swell as naturally sodium bentonites and those that do not as naturally non-sodium bentonites. However, the properties of the bentonites can vary due the quantity and cationic type of montmorillonite. These variations cannot always be predicted, because there is no consolidated and practical method for clays mineralogical quantification. A quantification via PXRD using the conventional Rietveld method via X-ray diffractometry is only reliable when all the crystalline structures of the mineral phases are known. This is not the case for bentonites, since the montmorillonite shows turbostratic disorder that is not considered in the available structural models, making it the mineralogical quantification a major challenge. Thus, in this work, was generated a calibrated hkl phase model for a so-called Formosa Mgmontmorillonite applying the combined Rietveld-Le Bail-Internal Standard method developed by Paz et al. (2018). The montmorillonite was obtained via centrifugation according to the Stokes law by particle size separation of the clay fraction (< 2 μm) from the Formosa bentonite. The sample was characterized by XRD, XRF, FTIR, SEM, MS and PSD, finding a low concentration of other mineral phases (impurities). According to the XRF and MS analysis, it is classified as a beidellitic montmorillonite with octahedral charge of >50 %. Quantitative results were satisfactory using the hkl model for montmorillonite-fluorite binary mixtures with montmorillonite content >50 % (statistical indices χ2 and RBragg < 5). The method was reproducible for three replicates of the montmorillonite-fluorite binary mixture (80-20%). The greater precision and reproducibility of the results, shows that the calibrated hkl phase model can be used satisfactorily for the mineralogical quantification of bentonites (60-80% montmorillonite content). These results showed that the combined method is a convenient and fast procedure, essential requirements for an industrial application, allowing deal with phases that have partial crystallographic information and handling severe diffractometric effects of structural disorder, such as turbostratic disorder, typical of clay minerals.
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