Artigos Científicos - IG

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Ação sonoquímica e influência das condições de tratamento térmico na preparação de cimentos do sistema binário CaO-Al2O3
(2010-03) LOURENÇO, Rafaela Roberta; EXPOSITO, Caio Cesar Dente; ANGÉLICA, Rômulo Simões; RODRIGUES, José de Anchieta
Cements of the CaO-Al2O3, binary system were prepared through a sonochemical process at room temperature followed by heat treatment. The conventional production consists of a reaction in which a stoichiometric mixture of lime and bauxite or alumina is melted or sintered. High temperatures and energy consumption is an inconvenience associated to this type of synthesis. In the sonochemical process, the initial reagents, calcia and alumina, are put in an aqueous suspension under the action an ultrasonic bath during some time. After that, the material is heat treated, after the evaporation of water. Ultrasonic waves can induce changes in the surface morphology of the particles, including size reduction of them. Consequently, the reagent particles become more reactive and this facilitates the final synthesis of the calcium aluminates during the heat treatment. The action of ultrasonic waves and the influence of thermal treatment conditions were studied on two initials molar compositions calcia:alumina of 1:1 and 1:2. Temperatures of 1000, 1200 and 1300 ºC for 1 and 6 h were employed. SEM and X-ray diffraction were used to characterize the obtained materials and the phases were semi-quantified through Rietveld method. In addition, mechanical strength of the products was evaluated through splitting tensile tests. Pastes consisting of cement, alumina and water were prepared using the calcium aluminates prepared through the sonochemical process and commercial cement as reference.
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Adsorção de fenol e benzeno em montmorilonita modificada com brometo de hexadeciltrimetilamônio
(2014-12) SANTOS, Sheila Silva dos; LEMOS, Vanda Porpino; VILAÇA, A. L. C.; TAVARES, Laís Conceição; QUEIRÓZ, Leandro Santos
This study evaluates the intercalation of the smectite dioctahedric state of Acre, Brazil, with the quaternary ammonium salt bromide, hexadecyltrimethylammonium (HDTMA) at concentrations ranging from 1 to 5 times the value of the original clay CEC and its application in the adsorption of phenol and benzene in the liquid phase. The materials were characterized by microanalysis X-ray diffraction, scanning electron microscopy /energy dispersive spectroscopy and infrared spectroscopy. The adsorption processes were carried out in simple systems and measurements of the concentrations of phenol and benzene were performed by spectrophotometry in the ultraviolet region. The results indicated that the intercalation of smectite with HDTMA provided approximately 78.8 expansion (range d001: 1.47 nm to 1.91 nm) and sharp decrease of the interlayer positions of elements such as Na, Ca, Mg and K, together by delamination/exfoliation of the clay original. In adsorption processes of phenol and benzene at HDTMA-arg 5 the following results were obtained: qmax = 4.44 and 35.8 mg.g-1; KL= 0.076 and 0.115 L.g-1; ΔGº = -16.85 and -18.38 kJ.mol-1, respectively. These data indicated that the adsorption of benzene and phenol in liquid phase in the organophilic HDTMA-arg 5 were favorable, spontaneous and physical interactions.
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Adsorção de molibdato em minerais de argilas naturais e modificadas com ácido sulfúrico, ácido húmico e uréia
(2013-03) PEREIRA, Patrícia Magalhães; LEMOS, Vanda Porpino; RODRIGUES, E.; FAIAL, Kelson do Carmo Freitas
Clay sediments from the municipalities Assis Brazil (Acre), were leached with solutions of sulfuric acid, humic acid and urea, to evaluate the retention capacity of molybdate in these materials and to investigate the feasibility of the adsorption processes at solid-solution interfaces. The materials were characterized from data of XRD, FTIR spectra, surface charge and chemical composition. The Langmuir isotherm models, Freundlich and Sips were used to fit the experimental data of adsorption. The minerals identified in the clay sediments were smectite, kaolinite, illite, quartz, albite, calcite and microclineo. The chemical modification leads amorphization of the modified sample with sulfuric acid and delamination along the plane 001 of the modified sample with urea. The settings defined by mathematical parameters (KL,Kf) of the adsorption isotherms, evaluation Ce vs. qe, pH vs. Qe, Qmax (sips) and Kd, indicated that the S10H15 sample is more efficient in the adsorption MoO42- ,with com qMax = 6.83 mg. L-1.
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Águas subterrâneas em Rondônia: análise estatística de dados hidroquímicos, organolépticos e bacteriológicos
(2009-12) ZUFFO, Catia Eliza; ABREU, Francisco de Assis Matos de; CAVALCANTE, Itabaraci Nazareno; NASCIMENTO, Gerson Flôres
In order to improve the ongoing process of managing groundwaters in the State of Rondonia we collected the results of 384 physical-chemical and / or bacteriological analyses of wells on file in the 2nd Socio-Economic and Ecological Zonation of the State of Rondonia, Brazil - ZSEE / RO, submitted by localities. We then treated and reorganized these data according to hydrographic basins using spreadsheets. We sought to characterize the quality of groundwater in major watersheds of the state of Rondonia by considering physical (color, pH and turbidity), chemical (chloride, total iron, sulfate, oxygen consumption, total hardness, calcium hardness, magnesium hardness, total solids, nitrogen as nitrite, nitrogen as nitrate, free carbon dioxide and HCO3 alkalinity) and bacteriological (standard bacterial counts of most probable number of coliform bacteria, most probable number of fecal coliform bacterial, most probable number of colonies - membrane filter method) properties. In order to test the adjustment of the data obtained to a normal distribution, we used the Kolmogorov-Smirnov method, modified by Lilliefors. The study revealed that the groundwater analyzed had good physical-organoleptic properties; the basins of the Madeira and of the Machado rivers showed the greatest changes in pH values, chloride and nitrate, indicative of a loss of quality of groundwater resources depending on population density. The Abunan river basin revealed the highest risk of fecal contamination, with water samples generally showing results that exceeded the bacteriological standards, thus requiring treatment by chlorination or boiling and filtration before human consumption.
Acesso aberto (Open Access)
Ambiente flúvio-deltáico influenciado por maré e tempestade da Formação Rio Maria, leste da Província Carajás (SE) do Cráton Amazônico
(2012-12) NASCIMENTO, Marivaldo dos Santos; OLIVEIRA, Camila Vilar de; ALTHOFF, Fernando Jacques
The Rio Maria Formation is a siliciclastic sedimentary sequence deposited in an eiperic sea formed along of eastern edge of the Carajás Province – the oldest Archean province of the Amazonian Craton – being intruded by rapakivi-type granite (1.88 Ga). Four facies associations have been recognized: prodelta-distal bar, delta-front/shoreface, delta-plain/distributaries and fluvial channels. Large-scale hummocky-swaley cross-stratifications (> 1 m) attest storm waves-influenced in upper shoreface deposits (tempestites). Bipolar cross-beddings with drape and reactivation surfaces reflect tidal-influence. Quartzarenite, sublitharenite and subarkose modal frameworks indicate stable continental block (craton interior) source. Heavy-minerals assemblages (e.g. zircon, tourmaline, staurolite, epidote, etc.) provide evidence of contribution from felsic plutonic igneous and metamorphic rocks. Well-rounded zircon grains can be associated to reworked sediments or metamorphic sources. These litotypes can be related to Rio Maria Block, which includes granitoid and metassedimentary rocks of the Rio Maria granite-greenstone terrain (3.0 – 2,86 Ga).
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Análise faciológica da Formação Alter do Chão (Cretáceo, Bacia do Amazonas), próximo à cidade de Óbidos, Pará, Brasil
(2012-03) MENDES, Anderson Conceição; TRUCKENBRODT, Werner Hermann Walter; NOGUEIRA, Afonso César Rodrigues
Cretaceous deposits of the Alter do Chão Formation, exposed on the banks of the Amazon river, near the town of Óbidos - PA, record a succession of sandstones, conglomerates and mudstones. Seven lithofacies have been recognized which comprise massive conglomerate (Cm), trough cross-bedded sandstone (St), planar cross-bedded sandstone (Sp), climbing cross-laminated sandstone (Sl), massive mudstone (Mm), bioturbated mudstone (Mb) and deformed mudstone (Md). These facies are organized in fining-upward cycles, 1 to 6m thick, and have been grouped into two associations: channel fill and overbank deposits belonging to a fluvial meandering system. The channel-fill deposits include lenticular gravel bars composed of facies Cm and St, sandy bedforms with facies St, Sp and Sl, and lateral accretion bar, consisted of facies St, Sp and Mm, but with distinct migration with regard to that of the sandy bed forms. While paleocurrent measurements from facies St and Sp of sandy bedforms indicate a preferred orientation of paleoflow to SW and a subordinate flow to S, the lateral accretion bar migrates to E/ESE. The following overbank elements have been recognized based on their geometric relationships: muddy floodplain deposits including abandoned channel plug, crevasse splay channel filled with facies St and Sp and natural levee deposits composed of facies St, Sl and Mm. While the muddy channel plug overlies sandstones, the crevasse channel fill is in contact with mudstones of the floodplain and also cuts through fine-grained sandstones and mudstones interpreted as natural levee deposits. Adjacent muddy lenses in the same stratigraphic level on sandstone but with smaller width than that of the abandoned channel are attributed to swales, filled during floods, capping lateral accretion bar.
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Aplicação de Al-PILC na adsorção de Cu2+, Ni2+e Co2+ utilizando modelos físico-químicos de adsorção
(2007) GUERRA, Denis de Jesus Lima; AIROLDI, Claudio; LEMOS, Vanda Porpino; ANGÉLICA, Rômulo Simões; VIANA, Rúbia Ribeiro
Smectite sample from the Serra de Maicuru area (Pará state, northern Brazil, Amazon region) were used for the pillaring process with Al13. Aluminum pillared clay (Al-PILC) was characterized by XRD, SEM and EDS. the textural analysis using nitrogen adsorption-desorption isotherms. The aim of this paper is to study in how Al-PILC adsorb heavy metals. The adsorption of Cu2+, Ni2+, Co2+ ions from aqueous solution in room temperature by Al-PILC have been carried out. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data, with the first model well adjusted with r = 0.999. The one-surface Langmuir equation provided the best fit to the data. The Freundlich equation presented limitations in rises concentrations, but acceptable values of parameters were obtained (Kf and n) with the use of the three models. The parameters were used to calculate the amount adsorbed Nf, a function constant Cs.
Acesso aberto (Open Access)
Aplicação de dados multisensor (SAR e ETM+) no reconhecimento de padrões de uso e ocupação do solo em costas tropicais: Costa Amazônica, Amapá, Brasil
(2009) SANTOS, Valdenira Ferreira dos; POLIDORI, Laurent; SILVEIRA, Odete Fátima Machado da; FIGUEIREDO JÚNIOR, Alberto Garcia de
Environmental studies require information on land use and land cover. This paper presents the applicability of multi-sensor satellite data (optical and radar) for land use and land cover on the Amapá coastal plain for mapping and recognition of natural and anthropogenic dynamics. This area is influenced by the Amazon River, by tides (tidal bore) and by the Intertropical Convergence Zone (ITCZ). Anthropogenic processes are associated with water buffalo ranching. The environmental information was acquired from previous data and field observation and was correlated with remote sensing data (JERS-1, RADARSAT-1, image from ETM+ sensor from Landsat 7 and DEM SRTM), digitally processed for multi-sensor, multi-scale and multi-date approach. Eight patterns of land use and land cover were identified (mangrove, "várzea" forest, arbustive vegetation area, freshwater marsh, anthropic field, intertidal plain, estuarine channel and lakes) as well with indication of natural and anthropogenic geomorphic features. The results from the evaluation of remote sensing data and the techniques applied demonstrated the potential of the remote sensing tool for studying environments in highly dynamic tropical coastal areas of difficult access. However, these tools may present some limitations once applied to application to the Amazon coast, which is a region under strong dynamic natural and anthropogenic processes.
Acesso aberto (Open Access)
Aplicação de Zr/Ti-PILC no processo de adsorção de Cu(II), Co(II) e Ni(II) utilizando modelos físico-químicos de adsorção e termodinâmica do processo
(2008) GUERRA, Denis de Jesus Lima; AIROLDI, Claudio; LEMOS, Vanda Porpino; ANGÉLICA, Rômulo Simões; VIANA, Rúbia Ribeiro
The aim of this investigation is to study how Zr/Ti-PILC adsorbs metals. The physico-chemical proprieties of Zr/Ti-PILC have been optimized with pillarization processes and Cu(II), Ni(II) and Co(II) adsorption from aqueous solution has been carried out, with maximum adsorption values of 8.85, 8.30 and 7.78 x10-1 mmol g-1, respectively. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data with a linear regression process. The energetic effect caused by metal interaction was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.
Acesso aberto (Open Access)
Aspectos texturais do magmatismo e tramas da tectônica impostas ao Granito Chaval na Zona de Cisalhamento Santa Rosa, extremo Noroeste da Província Borborema
(2014-12) GORAYEB, Paulo Sérgio de Sousa; LIMA, Aline Maria Meiguins de
The Northwestern region of Borborema Province features a wide variety of granitic bodies with diverse nature and tectonic evolution, since the Paleoproterozoic to Early Paleozoic, presenting higher incidence related to Neoproterozoic emplaced at different stages of Brasiliano (Panafrican) orogeny. One of these examples is the Chaval Granite representing a batholith body intruded in orthogneisses of Granja Complex and supracrustal rocks of Martinópole Group, outcropped near the Ceará and Piauí Atlantic coasts, Northeastern Brazil. The batholith is partly covered by Cenozoic coastal deposits and sedimentary rocks of the Paleozoic Parnaíba Basin. The Chaval Granite has a striking textural feature, which is represented by porphyritic highlighting microcline megacrysts in syenogranites and monzogranites, and many others textural/structural features of magmatic origin. They allowed interpreting the plutonic evolution at relatively shallow crustal level emplacement acting processes of fractional crystallization, magma mixing with intense magmatic flow, and gravitational force due to density difference of magma that lead to fluctuation of megacrysts of microcline and plagioclase in the residual magma, and accommodation of small bodies of leucogranite and pegmatites in the final stages of plutonic magmatic evolution of such plutonism. On the other hand, across the Eastern half of the pluton, there is a rich collection of shear structures related to the tectonic construction of the Santa Rosa Transcurrent Shear Zone, which led to tectono-metamorphic transformations superimposed on magmatic features that reached peak metamorphic conditions in the low amphibolite facies. Cartographically, three homogeneous structural domains were individualized, and each of them presents a variety of petrographic-structural features of the Chaval of igneous or tectonic nature. The plutonic rocks were deformed and progressively modified Eastward, in which the rocks change to darker gray, and comminution and dynamic recrystallization processes are reduced, as well as the coarse-grained granites are progressively, as well as the size of the phenocrysts to thinner dimensions, keeping their porphyroid characteristics, being accentuated the mylonitic features to achieve the main portion of Santa Rosa Transcurrent Shear Zone. As main structural features, there is the ondulatory extinction, cleavage and twining bending, twinning deformation, anastomosing foliation, badinage, S-C foliation, mineral stretching lineation, rotated and segmented crystals, lenticular, almondy or fish forms of porphyroclasts, pressure shadow, and ribbon quartz. The products of this shear deformation result in the formation of protomylonites, mylonites, and ultramylonites. These mylonite zones represent areas with the highest concentration of deformation that can gradually follow their textural and mineralogical changes, setting up a classic sequence of progressive heterogeneous deformation by simple shear in brittle-ductile and ductile conditions. The emplacement of Chaval Granite happened at the end of the Cryogenian (approximately 630 Ma) and can be interpreted as syn-tardi tectonic magmatism regarding the Brasiliano event. The process that generated the Santa Rosa Shear Zone resulted from lateral extravasation crustal masses in ductile flow took place in the final increments of deformation of a continental collision on an oblique thrust system, which built the Northwest Ceará Shear Belt, and happened at the end of Brasiliano (Panafrican) orogeny in Northwest Borborema Province.
Acesso aberto (Open Access)
Atividade pozolânica de arenito zeolítico da região Nordeste do Brasil
(2012-06) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
In northeastern Brazil, sedimentary zeolites occur associated with sandstones of the Corda Formation (Parnaiba Paleozoic Basin), discovered in the 2000s. These sandstones are composed of quartz, natural zeolites (estilbite) and clay minerals (smectite). Preliminary studies have shown that this sandstone can be used as a pozzolanic material in Portland-cement-based systems after the material has been sieved to remove the quartz and after thermal activation because the estilbite has low pozzolanic activity. The main objective of this study was to determine the best particle size distribution that yields the highest smectite and zeolite concentration, besides the best temperature for higher pozzolanic activity. The experimental program employed the zeolitic sandstone passing through a #200 and #325 mesh sieve and calcination at the following temperatures: 150°C, 300°C and 500°C. Chemical analysis of the sieved samples was carried out by X-ray fluorescence spectroscopy and X-ray diffractometry, while mineralogical characterization was done by X-ray and thermogravimetric analysis and thermogravimetry..To assess reactivity, calorimetry driving and mechanical tests for pozzolanic activity in hydrated lime and cement Porltand were performed. The results showed that the sample sieved through at #200 mesh was the most suitable because it had a higher concentration of estilbite and a higher percentage of material seived compared to the sample sieved at #325 mesh, 15% and 2% respectively. The 500°C calcination temperature was accompanied by increased pozzolanic activity due to changes in estilbite and smectite cristalinity; the more moderate temperatures of 150°C and 300°C were not sufficient to achieve similar results. The mortars with sandstone sieved at #200 mesh and calcinated at 500°C reached the minimum limits required for a material to be considered as pozzolanic, i.e, 6 MPa for hydrated lime mortars and 75% for the pozzolanic index activity (PAI).
Acesso aberto (Open Access)
Atividade pozolânica dos resíduos cauliníticos das indústrias de mineração de caulim da Amazônia
(2011) BARATA, Márcio Santos; ANGÉLICA, Rômulo Simões
The Capim and Jari regions, northern Brazil, are the main Kaolin mining areas in the Amazon region. They encompass the biggest high-grade (high whiteness) kaolin reserves for the paper coating industry. During the beneficiation of this kaolin, different kinds of processed and non-processed wastes are generated. The main objective of this work was to evaluate the reactivity of pozolans produced after calcinations and milling of such residues, by the comparison of the mineralogical composition and the type of kaolinite from the two regions (different kinds of structural order/disorder). The heating temperature to produce the pozolans was evaluated in order to obtain the better reactivity with lower energy consumption. The results showed that the pozolans obtained from both residues exhibited high reactivity, also better than those commercially available. Those obtained from kaolinites with high structural defects needed lower temperatures in comparison with low-defects kaolinites. The use of the former kaolinites reduces the production costs to obtain pozolans without losing quality in terms of reactivity.
Acesso aberto (Open Access)
Avaliação da resistência ao desgaste de aluminas nanométricas produzidas a partir da decomposição térmica de acetato de alumínio liofilizado
(2007-12) FAGURY NETO, Elias; KIMINAMI, Ruth Herta Goldschmidt Aliaga
Wear resistance tests, using the pin-on-disk test method with sliding pairs, were carried out on pins produced from alumina powders prepared by thermal decomposition of lyophilized aluminum acetate. Alumina powders of a-Al2O3 and g-Al2O3 phases, with and without sintering additives (MgO and La2O3), were used to produce wear pins. In addition, pins made of commercial alumina (A1000 SG) were tested and the results compared. The tests, carried out according to the ASTM standard, indicated that the pins made with a-Al2O3 powder showed high wear resistance, a finding corroborated by mass loss tests and scanning electron microscopy. The g-Al2O3 pins showed an intermediary performance while the A1000 SG pins showed less interesting results.
Acesso aberto (Open Access)
Avaliação do desempenho ambiental e racionalização do consumo de água no segmento industrial de produção de bebidas
(2013-12) CAVALCANTE, Luciana Miranda; MACHADO, Luiza Carla Girard Teixeira; LIMA, Aline Maria Meiguins de
The Amazon region, with a high hydric potential, has attracted companies that require significant volumes of water; therefore, control instruments are necessary to monitor this trend. In this study, the degree of rationing of water use by beverage industries in Para state and the behavior of the sector are discussed. The subjects' variables were classified according to four study dimensions (environmental management, water management, wastewater management, and advanced measures for rationing) that compose the rationing level of water industrial management. The independent variables were associated by size, industry type, packaging used, water availability and the economic value of water. The data show that beverage production has a significant water footprint, higher than 15,250 m3/day, and that small industries have the highest relative consumptions (more than 7 L of water/beverage L). In general, the sector does not ration significant quantities of water; a better result was obtained for water management. However, some more efficient measures could be adopted, especially with regard to water reuse in cooling towers. Analysis of the variables shows that the rationing level is directly dependent on the size of the industry and on the type of product. Consumption tends to be lavish. In response to this situation, public policies should be prioritized to determine the water footprint of products and environmental cost should be considered in the overall cost of production.
Acesso aberto (Open Access)
Avaliação experimental de métodos de armadilhas de sedimentos para determinação do transporte costeiro da praia da Romana, ilha dos Guarás (nordeste do Pará)
(2012) RANIERI, Leilanhe Almeida; EL-ROBRINI, Maâmar
The Romana Beach is ruled by waves, with an average height of 1,5 m, winds (average of 4,6 m/s) predominantly from the NE and semidiurnal meso-macrotidal (ranging from 4,3 m - march/2010; 3,4 m - august/2010). The methodology consisted of sediments samples with traps and intensity measurements of longshore currents and local winds during the months of january, march and august 2010. In the wind traps, the accumulated weight of sediments was very low, ranging from 0,02 g to 0,8 g (maximum occurred in August in the eastern sector, as well as the wind speed: 6,7 m/s). Larger quantities of sediment were collected from the eastern to the western sectors, coinciding with the prevailing wind direction (NE), whose maximum speed occurred in august (6.7 m/s in the eastern sector). In the portable traps, the minimum weight occurred in march (eastern sector, ebb tide: 0,74 g/h/m3), and the maximum in january (central sector, rising tide:139 g/h/m3). The intensity of the longitudinal currents ranged from 0,20 m/s (ebb tide) to 1,41 m/s (rising tide). It was concluded that the largest forcing of sediment transport on the beach is the flood tide current, which intensifies the longitudinal currents from the eastern to the west sectors. Secondly, the NE winds which minimize the loss of sediments on the beach, especially in the central and eastern sectors. Then the waves, maintain the direction of E-W transport because to their incidences on the coast with direction NE.
Acesso aberto (Open Access)
Avaliação preliminar do emprego de arenito zeolítico da região nordeste do Brasil como material pozolânico para cimento Portland
(2011-12) PICANÇO, Marcelo de Souza; ANGÉLICA, Rômulo Simões; BARATA, Márcio Santos
Natural zeolites usually exhibit pozzolanic activity without any additional treatment, e.g. thermal activation. They have been used for building since the ancient Roman Empire times in the production of hydraulic cements and concretes. Nowadays, there are many discussions involving the natural zeolites pozzolanic reactivity in the incorporation of the Portland cement composition. The appropriate use of pozzolans enables the production of special cements with lower manufacturing cost and with a greater durability in comparison with the corresponding cements without addition. In Brazil, zeolite consumption comes either from the importation of foreign countries or synthetic products. No zeolite mine is available in the country and only few geological occurrences were already described in the literature without any commercial interest. In northeast Brazil, the Geological Survey (CPRM) discovered zeolite-bearing sandstones related to Cretaceous sedimentary rocks of the Parnaíba Paleozoic Basin. The main purpose of this paper is to evaluate the possible use of such sandstones as pozzolan for using in Portland cements (CPI-S). A bulk sample of the zeolitic sandstone (AZ) was collected in the field. In the laboratory, preparation included drying, milling and sieving at the following grain-size fractions, in order to remove quartz and concentrate the zeolite: 100# (AZ-1), 200# (AZ-2) and 325# (AZ-3). After mineralogical evaluation, the AZ-2 fraction was selected for further analysis and assays. The experimental study was mainly based on mineralogical characterization, including: X-ray diffraction (XRD), chemical analysis and heat flow calorimetry, besides pozzolanic activity assay and compressive strength. The results show that the mineralogical composition of the zeolitic sandstone is mainly quartz, zeolite (stilbite) and smectite. Stilbite is the main pozzolanic phase, and the smectite can also play an important role. The hydration of the Portland cement was accelerated due to the very fine grained nature of the material. Meanwhile, the reactivity obtained was slightly below the standard requirements to be used in industrial scale. Additional studies should be carried out in order to evaluate if a further thermal treatment (between 300 °C and 500 °C) may increase the pozzolanic activity due to the stilbite destruction around this temperature. The same happens with kaolinite that needs thermal treatment above 550 ºC to convert to the amorphous phase metakaolin in order to be used as one of the most commons pozzolans in the cement industry. The main purpose was to contribute for the production of an alternative kind of cement which produces less pollution to the environment (CO2 decrease in the atmosphere) with cost saving. In addition, it is expected to contribute for the exploitation of the sedimentary zeolites occurrences which have been relatively well studied from a geological point, but are still not mined.
Acesso aberto (Open Access)
Basaltos almofadados da Suíte Ofiolítica Morro do Agostinho: registros de fundo oceânico na porção centro-oeste do Cinturão Araguaia
(2013-12) MIYAGAWA, Luciana de Jesus Penha Pamplona; GORAYEB, Paulo Sérgio de Sousa
Along the domain of low metamorphic grade (Midwestern portion) of the Araguaia Belt, outcrop dozens mafic and/or ultramafic bodies of ophiolitic suites. An example is the Morro do Agostinho Ophiolite Suite, in the surroundings of the city of Araguacema (Tocantins) that configures a small isolated body that sustains the Morro do Agostinho and is tectonically emplaced in meta-sandstones, slates and phyllites of Couto Magalhães Formation (Tocantins Group). The Morro do Agostinho Ophiolite Suite consists of serpentinized peridotites, basalts and ferriferous cherts. The association of basalts is characterized by a significant layer of submarine pillow lavas overlying serpentinized peridotites. The basalts were classified into massive and hialobasalts types. Massive basalts are homogenous, with intersertal texture that is essentially composed of thin laths and acicular crystals of plagioclase and clinopyroxene and present rare crystals of olivine, chalcocite and chalcopyrite. Hyalobasalt shows ultra-fast cooling features (quenching) as spherulites, radial, acicular and skeletal crystals of plagioclase and clinopyroxene with forms of swallowtail. Geochemical data, including (La/Yb)n and (La/Sm)n ratios less than 1, indicate a subalkaline-tholeiitic MORB nature of the basalts. These rocks show that during the geological evolution of Araguaia Belt, there was an oceanization stage of Araguaia Basin, with litospheric mantle's exposure, followed by lava's extravasation and sedimentation of cherts and banded iron formation in deep ocean environment. After sedimentary filling of the Couto Magalhães Formation (Tocantins Group), the tectonic inversion, which led to the exhumation of the ophiolitic bodies, especially along thrust surface, with fragmenting and tectonic mixing with supracrustal rocks, accompanied by regional metamorphism under conditions of low green schist facies. The Morro do Agostinho Ophiolite Suite therefore represents a small allochthonous fragment of a well-preserved ocean mantle/crust lithosphere, similar to the others examples found in the Araguaia Belt who marks the Araguaia Basin's moment of oceanization during the Neoproterozoic.
Acesso aberto (Open Access)
Bathymetric trends of northeastern Brazilian snappers (Pisces, Lutjanidae): implications for the reef fishery dynamic
(2005-09) FRÉDOU, Thierry; FERREIRA, Beatrice Padovani
The investigation of bathymetric distribution of five snappers caught along the Brazilian Northeastern coast by artisanal fleets through the analysis of the catch composition and relative abundance (CPUE) showed that, on the overall, fished mean size increased along depth and that particular species dominated the catch according to the depth strata. Mutton snapper, L. analis, yellowtail snapper, L. chrysurus, and dog snapper, L. jocu were mainly caught at intermediate depth (20-80m) whereas lane snapper, L. synagris, and silk snapper, L. vivanus, inhabit respectively shallow (<20m) and deep (>80 m) waters. Each fleet category exploited preferentially a particular combination of species and their size range. The fleet dynamic of the Northeast Brazil is technologically heterogeneous and determines the catch composition. Geographical distribution of the fishery and technical interaction between fleets and gears should be considered by the management of these species in order to maintain the sustainability of the stock and to guarantee the continuance of the resource.
Acesso aberto (Open Access)
Batólito Guaporeí: uma extensão do Complexo Granitoide Pensamiento em Mato Grosso, SW do Cráton Amazônico
(2013-03) NALON, Patrícia Alves; SOUSA, Maria Zélia Aguiar de; RUIZ, Amarildo Salina; MACAMBIRA, Moacir José Buenano
The Guaporeí Batholith is located in the Vila Bela da Santíssima Trindade region, at Mato Grosso State (Brazil), and crops out over 240 km2 along the NW direction. It is situated in the Paraguá Terrane, included in the Rondonian-San Ignacio Province, in the southwestern portion of the Amazonian Craton. The batholith is made up of monzogranite, with subordinate granodiorite, quartz monzonite and syenogranite, shows coarse porphyritic/porphyroclastic texture, is metamorphosed in the greenschist facies and mylonitized along shear zones. The biotite is the main primary mafic mineral, sometimes associated with amphibole. Geochemical data indicated high-potassium calc-alkaline and metaluminous to peraluminous character, probably generated in continental arc environment, and evolved by fractional crystallization associated to crustal assimilation. Two stages of deformation related to the evolution of San Ignacio compressional orogeny were identified and are characterized by stretching and lineation, and development of S1 and S2 foliations. Dating by single zircon Pb-evaporation method yields a crystallization age of 1,314 ± 3 Ma, whereas Sm-Nd whole rock isotope data indicate a TDM model age of ca. 1.7 Ga and a negative value for εNd (t = 1,3) of -14, suggesting crustal contribution in the magma genesis. The obtained data indicate similarities between these rocks and those of the Pensamiento Granitoid Complex, in the Bolivian counterpart, and put in evidence that the Guaporeí Batholith is an extension of this complex.
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 Simões
This 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.