Navegando por Autor "FLORES, Silvia Maria Pereira"

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Alumina para utilização cerâmica, obtida a partir do rejeito de beneficiamento de caulim
(1997-12) FLORES, Silvia Maria Pereira; NEVES, Roberto de Freitas
The kaolin processing for paper covering produces a great volume of residues formed primarily by kaolinite claymineral, here the starting material for the synthesis of ammonium alumen aiming to obtain free sodium alumina with fine grade for ceramic manufacturing. The synthesis process to obtain ammonium alumen consisted of the following procedures: residues calcination and sulphuric leaching of metakaolinite followed by neutralization/crystallisation of aluminum sulphate solution with ammonium hydroxide concentrated solution. The effect of calcination temperature (650 °C, 700 °C and 750 °C), calcination time of residues (30 min, 60 min and 120 min), sulphuric acid concentration as well as leaching temperature (70 °C, 80 °C and 90 °C) on the kinetics of aluminum leaching were studied. The influence of pH on ammonium alumen crystallization was also studied. Data on chemical analysis, XRD, DTA, TGA and granulometry of the material utilized and synthesized are presented and discussed.
Acesso aberto (Open Access)
Aproveitamento do rejeito de caulim na produção de alumina para cerâmica e sílica de baixa granulometria
(Universidade Federal do Pará, 2000-11-29) FLORES, Silvia Maria Pereira; NEVES, Roberto de Freitas; http://lattes.cnpq.br/9559386620588673
The Amazon region detains 10% of the world reserves of kaolim. Since the seventy's, two great amazonic beds of kaolim are explored, producing kaolim for paper cover. In the beneficiation process, it's generated an elevated volume of polluted industrial residue which is deposited in extensivas and onerous lagoons of sedimentation. Because of the residue is very voluminous, these lagoons become an environmental problem of great proportions, due the extensivas deforested areas used for their constructions ( Barata, 1998). In this work, are suggested altematives of economic utilization of this residue, which is constituted, mainly, by a suspension of the claymineral kaolinite, for the production of pozolane, aluminium sulphate, the synthesis of the ammonium alum and alumina for ceramics utilization. The methodology constitutes in the drying and the calcination of the residue, followed by the extraction of the AI retained by the acid lixiviation H2SO4 ) followed by the ammonium alum crystallisation, for the reaction with the concentrated NH4OH, by means of pH control, and later calcination at 1200°C, getting a-Al2O3, with no sodium and Iow granulometry. From the aluminas obtained, are made bodies of proof smashed and sintered at 1600°C, to the determination of the ceramics properties, which are compared to one of the commercial alumina. After the acid lixiviation for the AI extraction, results as an insoluble material, an amorphous silica, for which it is suggested, as an additional contribution, an economic application, using it as artificial pozolane in building portland cement, making mechanics tests for the evaluation of its performance. The material that were used and synthesized were characterized throught the use of the X ray diffraction, eletronic scanning microscopy, the infra-red spectroscopy, thermogravimetry, differential thermic analisys, particle size analysis, specific area BET, porosity, chemical analisys throught umid means and throught X ray fluorescence.
Acesso aberto (Open Access)
Mineralogia e geoquímica da zona de alteração do depósito de Salobo, Serra dos Carajás
(Universidade Federal do Pará, 1989-07-31) FLORES, Silvia Maria Pereira; OLIVEIRA, Nilson Pinto de
The Salobo 3A copper deposit, located in the Mineral Province of Carajás, State of Pará, is part of a set of sulphide copper occurrences, in a sequence of metasedimentary and matavolcanic rocks, which is more than 70 km long. The product resulting from the alteration, in an equatorial climate, of these mineralized rocks reaches a thickness of 70 to 100 m and presents as a particularity the absence of copper mineralization typical of oxidation zones, preserving, however, approximately, the copper contents of the primary ore. For this research, three profiles were selected for mineralogical and geochemical studies, aiming to identify the Cu support phases, as well as the behavior of some important elements (Ni, Co, Au, Ag. Mo) along the profiles. Mineralogical studies allowed us to conclude that the profiles studied have a low degree of maturity. As a result, it was only possible to characterize horizons in the profiles from the identification of the nature of the clay-minerals present, which were identified as: clay-minerals 15 Å (smectite, vermiculite), 10 Å (illite), 7 Å ( kaolinite) and interstratified (hydrobiotite). The data obtained allow us to conclude that: a) the most important copper support phases are the alteration products of biotites: hydrobiotite and vermiculite. b) Ni, after its release from primary minerals, seems to remain bound to smectite and in some cases to vermiculite, when at depth. Close to the surface or in more mature profiles, Ni seems to be associated with Fe and Mn oxyhydroxides. c) in the destabilization of ferromagnesian minerals, the released Co seems to remain in the profiles, absorbed on the Fe and Mn oxy-hydroxides. d) Au, probably originated from the most magnetic shales, shows to be associated with secondary Fe minerals, and may also be adsorbed in clays, close to the surface. e) Ag may be originally replacing part of the Cu in the chalcopyrite and, in the destabilization of this, it is associated mainly with Mn oxides and Fe hydroxides. f) Mo, originating from molybdenite, must be adsorbed on Fe oxyhydroxides or on clay minerals, requiring more detailed studies for more precise conclusions. Although lateritic enrichment in Cu in Salobo soils was expected, what was observed is that there is only temporary conservation of this element in the intermediate stages of alteration of biotites which, once altered to the point of phyllosilicates 1:1, with the maturation of the profile , will tend to lose this Cu, leached by the percolation waters.