Navegando por Assunto "Metakaolin"

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Ativação alcalina para a produção de geopolímeros a partir de resíduo industrial
(Universidade Federal do Pará, 2018-02-02) BRITO, Woshington da Silva; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
The sustainable construction of the future, and has low energy consumption and greenhouse gas emissions must also adopt the principle of reuse of wastes impacting the environment generated by the productive chain. The aluminum production chain has as one of the leading waste impact on the environment the gray generation. The present study focused on the research and development of a cement-based material. Refers to an inorganic polymer, formed by the activation of amorphous aluminosilicates (Al2O3. SiO2), which react in a strongly alkaline medium, called geopolymer. As a raw material furnace fly ash, mineral residue from the combustion of the boilers of the company of the municipality of Barcarena-PA; As a source of aluminosilicate, and the kaolin that underwent the process of burning at 800 ºC that became metakaolin; And the alkaline medium of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), used as activators. As fly ash partially crystallizes during burning and loses some of its amorphous state, so are its reactive properties to chemically combine during the geopolymerization reaction are reduced. To increase reactive properties of fly ash and added metakaolin. As the main analyzes, no X-ray diffraction (XRD), X-ray fluorescence (FRX), scanning electron microscopy (SEM) and EDS. Tests of resistance to compression of the traces in the hardened state were also carried out and the rheological test of the geopolymer was carried out at the start of the reaction in the fresh state. For Davidovits ratios in the range of 2.5 to 3.23, the best geopolymers with compressive strength were obtained reaching 25 MPa in 24 hours of cure. For 60 days of cure at room temperature the geopolymers reached a resistance of 45, 36 MPa. The research carried out through the characterization analysis of the samples and the mechanical and rheological tests were presented in a satisfactory way and demonstrated that the residues of fly ash and metakaolin, when activated with sodium silicate and sodium hydroxide, are an alternative for the possible application of Geopolymer materials in construction.
Acesso aberto (Open Access)
Desenvolvimento de processo de zeólita A utilizando o caulim da Amazônia e aplicação na adsorção de Cu+2
(Universidade Federal do Pará, 2014-08-22) MORAES, Cristiane Gomes; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
Around the world millions of tons of inorganic waste are produced every day in mining and mineral processing. These wastes are stored in sedimentation basins or discarded in landfills, and very often are thrown directly into the environment without any treatment process. However, alternative recycling and/or reuse should be investigated and, where possible. This work shows studies in order to reuse the kaolin waste from Amazon, from a kaolin processing company for paper covering. For the synthesis of the zeolite in static and dynamic hydrothermal processes, was used as the silicon source and the aluminum kaolin waste, which passed through the calcination procedure in a muffle at 600°C to obtain metakaolin; and as sodium source chose to 5M sodium hydroxide solution. In the static method was used stainless steel autoclaves, in an oven at 110°C, using 1,75g of metakaolin, varying the time of synthesis and the mass of sodium hydroxide and the dynamic process, we used 100g of metakaolin, mass 34,5g sodium hydroxide; at 95°C under stirring system, varying the time of synthesis, in order to determine the optimal conditions in the synthesis of the zeolite in the process. Matches materials and zeolitic products obtained in the syntheses were characterized by: X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis and thermogravimetric (DTA/TG), X-ray fluorescence (XRF) and particle size analysis. There is the possibility of scale-up, since the zeolite obtained, the dynamic process in time of 30 min. Data from adsorption experiments determined by iodometric technique copper alloys and metal and minerals, adjusted by Langmuir and Freundlich suggest that the static and dynamic zeolitic materials have good adsorptive capacity reached 95% efficiency for concentrations in the range of 50 to 100mg/L, thereby demonstrating that these materials are efficient and cost effective alternative when used for the removal of heavy metals, in the case of copper, the treatment of industrial effluents.
Acesso aberto (Open Access)
Estudo da influência do tempo de reação e do teor de “Na” na síntese de zeólitas
(Universidade Federal do Pará, 2013-04-05) RODRIGUES, Emerson Cardoso; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
This work aims to synthesize zeolite type "A" using as raw kaolin filler. The synthesis of zeolites was performed in a short time and without agitation. The starting materials and the product were identified and characterized by X ray Diffraction (XRD), Fluorescence Spectrometry, X Ray, Scanning Electron Microscopy (SEM), Grain Size Analysis and Gravimetric and Differential Thermal Analysis (DTA and TG). In the synthesis process was used as the silica source and the alumina metakaolinite, which has been calcined at a temperature of 600 ° C for 2 hours threshold firing in a muffle type furnace. As a source of sodium was used a solution of sodium hydroxide 5 M in the system was also added distilled water. Various syntheses were performed inside an oven at 110 °C. The variation in reaction time and sodium content were the variables in the process. The results of the synthesis of zeolite A proved satisfactory, especially in time of 10 h with a ratio Al / Na = 0.57. The reaction time and amount of sodium are directly proportional to the formation of another phase called zeolitic Hydroxysodalite. From the zeolite A, by ion exchange with a solution of calcium chloride was obtained zeolite 5A without agitation.
Acesso aberto (Open Access)
Estudo de aproveitamento do resíduo do beneficiamento de caulim como matéria prima na produção de pozolanas para cimentos compostos e pozolânicos
(Universidade Federal do Pará, 2004-01-16) LIMA, Jefferson Maia; CARNEIRO, Arnaldo Manoel Pereira; http://lattes.cnpq.br/9191655335324358
The use of residue in civil construction can to become a activity of extreme important and more frequent, mainly due to amount available with potential of recycling, possible reduction of environments impacts. The kaolin industries produces two type of residue. The residue contain clay mineral kaulinite show potentially of is to employ by pozzolanas at the construction civil industry. This research evaluates the technical viability to production of pozzolanas from mixtures in various percentagens of kaulinitic residue with limestone, wanting increase the reactivity. The contents of replacement of cement for pozzolanas is of 10%, 20%, 30%, 40%, 50% e 60% was studied. The cement employed was CP I S 32 and the pozolanas was made in the laboratory. The following tests in the experiment cements were carried out: specific gravity, specific surface area, water of normal consistency, setting time and compressive strength. Also, were carried out mineralogical tests in the pozolanas. The incorporation of pozzolanas allowed to mortar obtain compressive strengths more than it reference even though in high contents. Due to the pozzolanas show a considerable hydraulic characteristic this it occurred. It waits of residue burned becomes a higher pozzolana to employ at the civil construction, mainly along with cement, mortars and concretes in the substitution of burning clays from natural deposits despite necessity of adding tests for confirmation and complementation of effects was observed.
Acesso aberto (Open Access)
Estudo de ligante geopolimérico obtido a partir de metacaulim e escória granulada de alto forno
(Universidade Federal do Pará, 2022-12-06) MORAES, Mario Henrique Moreira de; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357
The need for alternative materials to replace Portland cement is a contemporary discussion. Those new and alternative materials must have a sustainable character and good durability to supply the demand of the civil construction sector and mitigate the environmental crises caused by the industry, such as the high emission rate of CO2. In this context, geopolymeric binders appear as materials produced by different solid precursors in contact with an alkaline activator, with zero CO2 emission and mechanical properties and durability compatible or superior to that of Portland cement. Thus, this study aimed to evaluate the geopolymeric binder obtained from the combination of metakaolin (MK) and ground granulated blast furnace slag (GGBFS) with three different molar concentrations of sodium hydroxide (8, 10, and 12 M) for the alkaline activator. Dosages were established from the partial mass substitution of MK by GGBFS, coded as G0 (100% MK 0% EAF), G20 (80% MK 20% EAF), and G40 (60% MK 40% EAF). XRD, XRF, and SEM analyses were conducted for solid precursors. Geopolymer pastes properties were evaluated in the fresh state regarding setting time and in the hardened state based on physical tests, average compressive strength, and fracture morphology. Results showed that the MK and the GGBFS have adequate reactivity and chemical composition for the geopolymer synthesis, with the presence of calcium in the GGBFS actively contributing to the reduction of the setting time and gain of mechanical resistance of the dosages. As for the hardened state, higher levels of water absorption are intrinsically related to a decrease in mechanical strength, with fracture analysis revealing the presence of pores and micropores that favor the propagation of cracks. Statistical analysis found that the interaction between the analyzed factors significantly influenced the properties of the materials, with 85.35% (R2 = 0.8535) of the model being able to explain the variation in compressive strength of geopolymers as a function of the factors used in the regression, limited to the chosen range of variables. The G40M12 formulation showed the highest compressive strength value (38.08 MPa) and the ideal synthesis parameters defined were the rotational frequency at 150 RPM, a partial replacement of MK by GGBFS of 40%, and the NaOH concentration of 12 M. Finally, from the correlation of the evaluated characteristics, the developed geopolymeric binders showed technological potential as alternative and sustainable materials, with properties comparable to those of Portland cement.
Acesso aberto (Open Access)
Estudo de rotas tecnológicas para a síntese de geopolímeros com adição de micropartículas de vidro: análise da influência do tamanho e forma das partículas
(Universidade Federal do Pará, 2025-02-14) MODESTO, Alex da Silva; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287
The sustainable construction of the future requires materials that consume less energy, emit fewer greenhouse gases and reuse waste that is harmful to the environment, such as discarded glass, one of the main waste products in the production chain. This research developed geopolymers, inorganic polymers formed by the activation of amorphous aluminosilicates in an alkaline medium, using me-takaolin and blast furnace slag as precursors and recycled glass microparticles as an additive. Com-positions were formulated with glass contents ranging from 0% to 60%, in particle size ranges of < 38 μm, 38-45 μm, 45-75 μm and 75-180 μm, and alkaline hydroxide and sodium silicate activators. Compression tests carried out on cylindrical specimens after 7 days of curing revealed that the addi-tion of 40% glass with a grain size of 38-45 μm resulted in an 80% increase in compressive strength compared to the unmodified material, reaching values of over 40 MPa. Microstructural analysis by SEM and EDS confirmed greater density and reduced porosity in the geopolymer matrix. Tensile adhesion tests also indicated the viability of the material as a substrate for coatings, meeting the demands of the construction industry. It is concluded that geopolymers with added recycled glass combine high mechanical performance and sustainability, promoting circular economy and repre-senting a viable alternative to the use of Portland cement.
Acesso aberto (Open Access)
Influência da temperatura de síntese do metacaulim para uso em pastas geopoliméricas
(Universidade Federal do Pará, 2022-12-09) BRANDÃO, Luis Felipe Alencar; SILVA, Alisson Clay Rios da; http://lattes.cnpq.br/7389345867032737; https://orcid.org/0000-0001-9186-2287; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357; https://orcid.org/0000-0001-7313-1229
Geopolymers are a type of alkali-activated cement, composed of one or more precursors (sources of aluminosilicates), in general metakaolin, and an alkaline activating solution. This type of cement is known to have low carbon emissions and high initial strength gain, besides being able to incorporate several industrial wastes in its structure and also be compatible for the creation of reinforced concrete or not. Therefore, this work aims to study the influence of kaolin processing temperature for its transformation into metakaolin, in addition to evaluating the best proportion of SiO2/Al2O3 between the range of 3.5, 4 and 4.5 regarding compressive strength. For this purpose, kaolin of commercial origin was used as raw material for the production of the precursor, solutions based on sodium silicate and sodium hydroxide as an alkaline activator. The kaolin was processed at 3 different temperatures (550 °C, 650 °C and 750 °C), originating 3 different precursors, MK- 550, MK-650 and MK-750, respectively. From this, cylindrical specimens were made to evaluate the compressive strength of the geopolymer paste. And by combining with the evaluation of the 3 sio2/Al2O3 contents, 9 analysis points were established. Through diphratometry (XRD), it is possible to notice that there was full amorphization of the kaolin at 750 °C. And when rehearsing the test specimens with cure for 7 days at room temperature, it was found that the best formulation was for SiO2/Al2O3 = 4.0, with 25.2 MPa. After a reduction in the total water content of the system, there was an increase in resistance to 46 MPa at 7 days and when waiting 28 days for the cure of this series, a reduction was noticed to 29 MPa, possibly related to alkali excesses. Further tests show that the water absorption and porosity of the material is 40 % and 48 % respectively. It is concluded that by calcinar kaolin at 750 °C it is possible to produce a precursor for geopolymers of good resistance, being more economical energetically than usual in the literature researched.
Acesso aberto (Open Access)
Produção de material zeolítico a partir de caulim da Amazônia em escala semi piloto: aplicação na adsorção de cobre
(Universidade Federal do Pará, 2019-06-27) RODRIGUES, Emerson Cardoso; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
This work aims to synthesize a zeolite product composed of zeolite type "A" plus sodalite using as filler kaolin starting material. The synthesis of Zeolites was carried out in a short time and in a system with agitation, in a reactor of stainless steel with a volume of approximately 0.001 m3, that is, in semi-pilot scale. The system was heated by steam from a boiler. The X ray diffraction (XRD), X ray Fluorescence Spectrometry, Scanning Electron Microscopy (SEM), Granulometric Analysis and Differential and Gravimetric Thermal Analysis (DTA and TG) were identified and characterized. In the synthesis process the metakaolin was used as the source of silica and alumina, which was obtained at 600 ° C for 2 hours of calcination in a muffle furnace. A 5M sodium hydroxide solution was used as the sodium source. Several syntheses were carried out for a maximum duration of 180 minutes. Every 30 minutes aliquots of the product were taken for the study of reaction kinetics. The results of the zeolite syntheses were satisfactory and the product obtained was applied to the adsorption of Cu2+ ions, in which the influence of the variables: time, temperature, pH and adsorbent quantity were evaluated. The determination of the best adsorption model was performed by the Monte Carlo method via Markov Chain and through the Akaike Information Criterion the isotherms that were closest to the presented results were established. The results obtained were compared with other studies available in the literature and showed significant values, which characterize the process of zeolite production and adsorption as promising and efficient.
Acesso aberto (Open Access)
Síntese e Caracterização da Zeólita Ferrierita (FER) a partir de resíduo caulinítico: a influência dos parâmetros do processo
(Universidade Federal do Pará, 2024-06-06) VILHENA, Thefeson Oliveira; MAIA, Ana Áurea Barreto; http://lattes.cnpq.br/0820112425394964; https://orcid.org/0000-0002-1880-1442
The present work addresses the synthesis of ferrierite zeolite from kaolin residue from the Amazon region. Ferrierite is a high-silica zeolite with a topology considered complex due to its structure, which presents a three-dimensional arrangement of atoms with intersecting perpendicular channels. It is widely used in catalysis, adsorption, ion exchange, among other processes. Its synthesis from alternative materials, such as kaolin residue, offers a recyclable and cost-reducing approach. Thus, kaolin residue from the Amazon was used as a source of Si and Al for the synthesis of ferrierite. In this context, thermal treatment of the kaolin residue was carried out to obtain metakaolinite for the formation of the reaction mixture. Since the Si/Al ratio of metakaolinite was insufficient to achieve the objectives, silica gel was added to the reaction mixture, along with other reagents, sources of other necessary elements/constituents, such as compounds with compensating cations (Na+ and K+) and a structural directing agent (ethylenediamine). The methodology of the IZA (International Zeolite Association) was used for the synthesis of ferrierite, and to reduce the synthesis time, an aging step of the silica gel solution was added to make it more reactive. The hydrothermal process took place at a constant temperature of 180°C. The research investigates the influence of different process parameters, such as aging time and synthesis time of ferrierite, as well as the combined use of different compensating cations. The products were characterized by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analysis. The results showed that ferrierite was effectively synthesized from 48 hours onwards. However, with the extension of the synthesis time, ferrierite with higher crystallinity was obtained. The use of different compensating cations also led to the formation of the ferrierite phase with the prolonged synthesis time. Furthermore, the research highlighted the importance of the aging step of the silica gel solution, which proved to be very effective for the synthesis of ferrierite zeolite.