Navegando por Autor "NEVES, Roberto de Freitas"
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Item Acesso aberto (Open Access) Alumina para utilização cerâmica, obtida a partir do rejeito de beneficiamento de caulim(1997-12) FLORES, Silvia Maria Pereira; NEVES, Roberto de FreitasThe 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.Item Acesso aberto (Open Access) Application of bauxite waste from amazon region in the heavy clay industry(2013-12) HILDEBRANDO, Edemarino Araujo; SOUZA, José Antônio da Silva; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasIn this work, a method was developed for the application of red mud, an alkaline leaching waste, from a bauxite processing plant located in northern Brazil (Amazon region) as starting material for heavy clay products. Samples were prepared by pressing blends of red mud and clay, which were then fired at temperatures from 900 ºC to 1190 ºC. Characterization was carried out by chemical analysis, differential thermal analysis (DTA) and X-ray diffraction (XRD), and the following ceramic properties were evaluated: water absorption, linear shrinkage and flexural strength. In order to evaluate the Na+ stability in the dense ceramic, leaching tests were also carried out on the specimens after sintering process. Results indicated that samples with 50 and 70 wt% of red mud are proper for being used in the production of ceramic bodies, due to its excellent properties, mainly high mechanical resistance and low water absorption, showing thus, an option to minimizing the environmental impacts caused by the aluminum industry.Item Acesso aberto (Open Access) Beneficiamento de uma argila tipo paligorskita da bacia de S. Luis-Grajaú, região de Alcântara, MA, e sua utilização como adsorvente de fósforo(2014-03) RODRIGUES, Gabriela Monice Arruda; NEVES, Roberto de Freitas; ANGÉLICA, Rômulo SimõesThis study used a sample from the basin of S. Luís-Grajaú, Maranhão state, Brazil,consisting of a mixture of predominantly palygorskite and dolomite, approaching the existence of this new occurrence, suggesting a processing method and its application as phosphorus adsorbent, once dolomite is a pH soil corrector while palygorskite has the function of nutrients carrier. First, chemical and mineralogical characterizations were performed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and separation of sand, silt and clay fractions. Sedimentation and phosphorus adsorption experiments were also performed, with determination of kinetic curve. After the X-ray diffraction analysis, results show that the sample consists mainly of palygorskite and dolomite. Illite, chlorite and quartz are also determined. It was also possible to see that the different types of disaggregation used show no significant differences in the diffraction patterns of the samples. The sand-silt-clay separation, although it is only based on the size of the material, showed a reasonable efficiency for material separation, as the sedimentation tests, where it was noticed that after 24 h, dolomite had disappeared from the supernatant. Determination of the kinetic curve revealed that the adsorption period of 2 h is not sufficient for phosphorus adsorption, requiring 24 h to reach the reaction equilibrium. Sorption tests showed efficiency higher than 91% of the initial phosphorus in solution, and the maximum quantity adsorbed per gram of sample was 0.607 mg. The correlation with the adsorption isotherm models studied, showed better results for Langmuir-Freundlich isotherm, with correlation coefficient of 0.9993, which can be attributed to the fact that adsorption occurs in more than one layer.Item 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 FreitasThe 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.Item Acesso aberto (Open Access) Caulins amazônicos: possíveis materiais de referência(2013-09) SANTOS, Suzianny Cristina Arimatéa; ROCHA JUNIOR, Carlos Augusto Ferreira da; SILVA, Liliane Nogueira da; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasKaolin is a product originated by the weathering action of aluminum silicates, such as feldspars, which in the Amazon region is favored by warm and humid climate. Used in fabrication of refractory, cement, pharmaceuticals, catalysts, paper coating and filler and other several purposes. This study aims to characterization and comparison of kaolins for paper coating and in natura from different regions in Pará ( Rio Capim, Jarí and Vila do Conde) of sedimentary origin with kaolins used as reference materials (IPT-28, IPT-32, IPT-42, KGa-1b e KGa-2). The characterizations were carried out by methods of chemical, physical and mineralogical analyses: Particle size distribution, X-Ray Diffraction, X-Ray Fluorescence, Scanning Electron Microscopy, Differential Thermal Analysis. The results showed as main mineral phase in all kaolin studied the kaolinite, with different degrees of "crystallinity". The Amazon kaolins presented high and low degree of structural order as well as reference materials. With respect to the properties of chemical composition, both materials showed levels of SiO2 + Al2O3 above 90%, low levels of Na2O and TiO2, with average of 0.6% and 1.92%, respectively for the reference materials, and for amazon kaolins were 0.3% and 1.62% to TiO2. The particle size analysis showed variances of the D50 from 0.7 to 9 µm to the amazon kaolins and from 1.7 to 6 µm to the reference materials. The sedimentary amazon kaolins, with low levels of impurities and found in large quantities, suggest a strong potential for use as reference kaolins.Item Acesso aberto (Open Access) Color and shade parameters of ultramarine zeolitic pigments synthesized from kaolin waste(2014-08) MENEZES, Raquel Aranha de; PAZ, Simone Patrícia Aranha da; ANGÉLICA, Rômulo Simões; NEVES, Roberto de Freitas; PERGHER, Sibele Berenice CastellãUltramarine pigments were successful synthesized from zeolite A obtained from kaolin waste. This waste has been used as an excellent source of silicon and aluminum for zeolite synthesis because of its high kaolinite concentrations and low contents of other accessory minerals. The cost is naturally less than the industrialized product. Color additives (Sulfur and Sodium Carbonate) were mixed with different proportions of zeolite A and further calcined for 5 h at 500 °C. They were characterized by XRD and XRF in addition to visual classification by color and shade. These products show colors from blue to green at different shades, both influenced by the amount of additives and cooling rate after calcination. Thus, a different quantity of the same additives in the same zeolitic matrix provides an increase in the color intensity. Cooling rate after calcination induces the color change which is substantially important in the pigments production.Item Acesso aberto (Open Access) Estabilidade térmica da zeólita A sintetizada a partir de um rejeito de caulim da Amazônia(2008-09) MAIA, Ana Áurea Barreto; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasZeolite A was calcined at 200, 400, 600, 800 and 1000 °C for 2h to evaluate its thermal stability. The zeolite A was synthesized using kaolin waste from kaolin processing industries for paper coating located in the Amazon region. Both zeolite A and further calcined products were characterized by X-ray diffraction analysis and scanning electron microscopy. The zeolite A structure remained stable up to 600 °C, where only small variations in peak intensities were observed. At 800 °C the diffraction pattern still exhibited zeolite A but with the absence of some peaks. At 1000 °C nepheline, mullite and probably sodalite were formed. The zeolite A was also heated at 900 and 950 °C to check the two exothermic peaks observed in the DTA curve. The X-ray diffraction analysis indicated the presence of nepheline, sodalite and mullite.Item Acesso aberto (Open Access) Investigação da reatividade e da cinética de dissolução do metacaulim em ácido sulfúrico(2013-06) LIMA, Paula Elissa Antonio de; ANGÉLICA, Rômulo Simões; SCHELLER, Thomas; NEVES, Roberto de FreitasA study about reactivity and dissolution kinetics of metakaolin was carried out using kaolin for paper coating derived from the Rio Capim region, Pará state, northern Brazil. The kaolin was burned at 600, 700, 800, 900 and 1000 ºC during 2 h in order to obtain metakaolin, followed by leaching with sulfuric acid at constant temperatures within the 50-95 ºC ± 3 ºC range. In the leachings, amounts of sulfuric acid corresponding to 10% above the stoichiometric values were used with respect to aluminum present in the material. Samples were collected in predetermined intervals every 15 min until a total time of 3 h, which were subjected to aluminum analysis by the EDTA titrimetric method. The results showed that the reactivity of burned kaolin decreased with the increase of burning temperature and that the dissolution kinetics of aluminum from metakaolin obtained by burning at 700 ºC followed the methods of homogeneous reaction used: integral method, method of half-lives and method of initial rates. 96.25 kJ/mol of activation energy was found as well as leaching reaction of the first order with respect to aluminum from metakaolin and the first order with respect to acid concentration. Researches carried out previously, using one of the reagents with excess above 90% and models of heterogeneous reaction, are consistent with the data found in this paper developed with only 10% excess.Item Acesso aberto (Open Access) 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 daExtensive 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.Item Acesso aberto (Open Access) Produção de zeólita analcima a partir de caulim amazônico(2013-12) MORAES, Cristiane Gomes; RODRIGUES, Emerson Cardoso; ANGÉLICA, Rômulo Simões; MACÊDO, Emanuel Negrão; NEVES, Roberto de FreitasIn the north of Brazil large mineral reserves are found, which have been exploited in recent decades typically generating large volumes of waste to the environment. In the specific case of the kaolin is the main product exported is for paper coating (commodity) with low value. Its production also generates a massive waste composed mainly of high purity kaolinite, but with no specification to cover paper, being discarded or used in other less noble application. As zeolites are more noble materials and present silica and alumina, one of the goals of this work was the development of the production process of the zeolite analcime from kaolin waste, diatomite and sodium hydroxide solution. In the other hand, the methods described for obtaining zeolites are developed in an alkaline medium, typically using an excess of sodium hydroxide in the reaction, causing environmental and economic problems. The synthesis process of zeolite analcime semi-continuous is described, using excess of sodium hydroxide to be recovered and reused in a new process cycle. The process consisted in five consecutive cycles in an autoclave by reaction of calcined kaolin, diatomaceous earth as a source of additional silica, aqueous solution of sodium hydroxide, and fresh sodium hydroxide solution, and recycled. The reaction process was developed at 210 °C for 24 h. The product obtained at the end of each cycle was analcime zeolite characterized by XRF, XRD, DTA / TG, SEM. The production process of analcime showed high yield and reuse of sodium hydroxide through recycle to be technically feasible.Item Acesso aberto (Open Access) Síntese de zeólita do tipo faujasita a partir de um rejeito de caulim(2012-12) HILDEBRANDO, Edemarino Araujo; ANGÉLICA, Rômulo Simões; NEVES, Roberto de Freitas; DIAZ, Francisco Rolando ValenzuelaZeolitic materials were synthesized using as main source of silicon and aluminum an industrial waste generated during the processing of kaolin for paper coating, the starting material and formed phases as reaction products were characterized by XRD, SEM and DRIFT. The synthesis process occurred in hydrothermal conditions and the effects, time-temperature, as well as the relations Si/Al and Na/Al were considered. The results show that in the methodology developed from kaolin waste, initially calcined at 700 ºC for 2 h, subjected then reaction in alkaline medium at 90 ºC for 48 h in presence of additional silica was obtained faujasite-type zeolite with good crystallinity as phase predominant in the synthesis product.Item Acesso aberto (Open Access) Síntese de zeólita do tipo faujasita: comparação entre caulim beneficiado e caulim flint(Universidade Federal do Pará, 2015-06) ROCHA JUNIOR, Carlos Augusto Ferreira da; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasThe main purpose of this work is the synthesis of faujasite zeolite using three different kinds of kaolin from the Amazon region, Brazil: two kaolin from the beneficiation process for paper coating and hard or flint kaolin, a non-processed kaoling from the mining site. Analysis of the reaction products of kaolin showed the formation of faujasite zeolite. Flint kaolin showed a lower potential with respect to zeolitization ratio Si/Al equal to 2, compared to processed kaolins, probably related to the iron present in the structure. New results show a complete change in the formation of faujasite, which turns to be the main mineralogical phase after iron removal.Item Acesso aberto (Open Access) Síntese de zeólitas a partir de cinza volante de caldeiras: caracterização física, química e mineralógica(2012-03) ROCHA JUNIOR, Carlos Augusto Ferreira da; SANTOS, Suzianny Cristina Arimatéa; SOUZA, Célio Augusto Gomes de; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasAlong the years, worldwide industrial development has causing a growing generation of residues, bringing potentials environmental problems. A study of the characteristics of these wastes, as well as the development of techniques for their use in new processes becomes indispensable for the environment preservation. The main purpose of this work is to evaluate the possible use of two important industrial residues from the Amazon region for zeolite synthesis: (a) the fly ash (particle size < 100 µm) that comes from burning of mineral coal in boiler; and (b) the microsilica, a by-product of the reaction between quartz and coal in the production of metallic silicon and alloys iron-silicon.The following chemical, physical and mineralogical characterization methods were carried out: X-ray diffractometry, X-ray fluorescence, scanning electron microscopy, granulometric analysis, differential thermal and thermogravimetric analysis (DTA-TG). The analyses were carried out at the following conditions: 60, 100, 150 and 190 °C, Na2O/A2O3 molar ratio of 5 and Si/Al molar ratio ranging from 2.12 to 15, and reaction time of 24 h. The results of the fly characterization demonstrate its enormous potential as raw material for the zeolite synthesis. SiO2 and Al2O3 represent more than 50% of its composition, mineralogical phases defined, low humidity content, low particle size (d90 < 10 µm), among others. Mineralogical analyses of the synthesized products showed the formation of some zeolite types, as follow: analcime, phillipsite, sodalite, zeolite P and tobermorite. The results show that the mixture fly ash-microsilica in these reaction conditions point to a promising material for zeolite synthesis.Item Acesso aberto (Open Access) Síntese e caracterização de argila esmectita Zn-estevensita(2014-06) HILDEBRANDO, Edemarino Araujo; VALENZUELA, Maria das Graças da Silva; NEVES, Roberto de Freitas; DIAZ, Francisco Rolando ValenzuelaClay of the smectite group was successfully obtained at a low temperature hydrothermal processing using sodium metasilicate, zinc nitrate and urea as precursor materials. During the synthesis step, the molar composition of the mixture and the temperature remained constant varying the reaction time. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance Fourier Transform infrared spectroscopy, differential thermal analysis and thermogravimetry, cation exchange capacity (CEC) and BET surface area measurements. The results show that in the methodology utilized is obtained Zn-stevensite with specific surface area of 171.6-203.4 m2/g and good crystallinity as present single phase in the reaction product after static synthesis at 90 ºC for 44 to 138 h, indicating that, the increased synthesis time is an important parameter for crystallization process of the clay.Item Acesso aberto (Open Access) Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado(2010) PAZ, Simone Patrícia Aranha da; ANGÉLICA, Rômulo Simões; NEVES, Roberto de FreitasBasic sodalite was successfully synthesized by hydrothermal method using kaolin waste as source of Aluminum and Silicon. This waste is mainly composed by kaolinite and is produced in large amount by kaolin processing industries for paper coating from the Amazon region. Initially, the waste has been calcined at 700 ºC for 2 h and then reacted with the following solutions: Na2CO3 and mixture of Na2CO3 + NaOH to 150 ºC with autogenous pressure for 24 h. The raw materials and transformed materials were characterized by XRD, FTIR and SEM. In both studied media, well-crystallized, basic sodalite was the only phase synthesized, while in the literature usually a mixture of zeolites is obtained.Item Acesso aberto (Open Access) Utilização de rejeito de caulim da Amazônia na síntese da zeólita A(2007-09) MAIA, Ana Áurea Barreto; CORREA, Edinelson Saldanha; ANGÉLICA, Rômulo Simões; SOUZA, Célio Augusto Gomes de; NEVES, Roberto de FreitasZeolite A and Hydroxysodalite were synthesized after kaolin wastes from kaolin processing industries for paper coating, located in the Amazon region. The waste is mainly composed by kaolinite, which has the same SiO2/Al2O3 ratio requested for those two zeolites. Thereby, synthesis process may occur in two steps: 1) the kaolin was submitted to thermal treatment, through calcination process at 700 °C for 2 h, in order to obtain the metakaolinite phase. The metakaolinite obtained reacted with NaOH solution, in hydrothermal conditions, using autoclaves, at the following temperatures: 80, 110 and 150 °C for 24 h. The starting materials were identified and characterized by means of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis and synthesis products were characterized by means of XRD, SEM, Thermal Methods (DTA-DTG) and Fourier Transformed Infrared Spectroscopy (FTIR). A mixture of Zeolite A and Hydroxysodalite was obtained through this process at 150°C. In the temperature of 110 ºC there was only the Zeolite A formation. Nevertheless, in the lowest synthesis temperature (80°C) there was no crystalline material formation for the established conditions.Item Acesso aberto (Open Access) Zeólita A sintetizada a partir de rejeitos do processo de beneficiamento de caulim(2012-06) SANTANA, Daniela Lira de; SARAIVA, Augusto Cesar Fonseca; NEVES, Roberto de Freitas; SILVA, Denilson Luz daRaw materials were used to synthesize zeolite A as an alternative and more economical source of silica and aluminum, using waste from the kaolin of the paper industry. Zeolites are crystalline substances with a structure characterized by a framework of linked tetrahedra, each one consisting of four oxygen atoms surrounding a cation. The development of processes for the synthesis of zeolites is of great interest for use in the areas of purification, adsorption and catalysis.The starting materials for the synthesis of zeolite A consisted of wastes from kaolin beneficiation of paper companies of Pará state, Brazil.The zeolite was obtained after calcination at 85 and 110 ºC during 24 h.The chracterization of the starting material was performed by X-ray diffraction, chemical analysis, thermogravimetric and differential thermal analysis, and scanning electron microscopy.The characterization of zeolite A was done by X-ray diffraction and scanning electron microscopy. The kaolin waste used as starting material showed to be essentially kaolinite mineral. For the temperatures and time used in the synthesis it was possible to form the crystalline phase of zeolite A for the two starting materials.