EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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8 resultados
Resultados da Pesquisa
Item Reverse cationic flotation of iron ore by amide-amine : bench studies.(2022) Rocha, Geriane Macedo; Cruz, Marcus Vinicius Macedo da; Lima, Neymayer Pereira; Lima, Rosa Malena FernandesThis study evaluated the performance of a new collector amide-amine compared with a traditional etheramine in conventional reverse cationic flotation of a siliceous itabirite sample of the Quadrilatero Ferrı ́fero (d80 1⁄4 116 mm, 40% Fe and 41.2% SiO2). Statistical design of experiments was used to determine the influence of pH, collector and starch dosages on mass and Fe recoveries, Fe and SiO2 grade in the concentrate, Fe grade in the tailings and Gaudin's selectivity index (S.I). For the amide-amine, starch had no significant effect on mass recovery and in the Fe and SiO2 grade in the concentrate. For the same dosages, it was found that amide-amine was less selective than etheramine. However, at higher dosages, at pH 8 and without starch, concentrates with Fe >65% and SiO2 <5% grades were obtained, similar to the grades obtained with etheramine and starch at pH 10.5. The mass and Fe recoveries were higher and consequently, the Fe grades in the tailings were lower. These results indicate that, despite the higher dosage required, amide- amine is selective without starch, which is very interesting from the economic point of view and simplification of the process route, implying a great potential for its industrial application.Item Quartz and hematite activation by Zn, Ca and Mg ions in the cationic flotation route for oxidized zinc ore.(2021) Duarte, Geraldo Magela Pereira; Lima, Rosa Malena FernandesAnionic, cationic and cationic/anionic flotation is widely used in the concentration process for low-grade oxidized zinc ores. In the cationic flotation route, sodium silicate is used as a depressant for gangue minerals and amine as a collector for zinc minerals previously activated by sodium sulfide. However, the presence of polyvalent ions in aqueous solution can affect the surface properties of the various minerals and consequently, the selectivity of the process. This study evaluated the effect of Zn, Ca, and Mg ions, originated by the solubility of smithsonite and dolomite, on the surface properties of quartz and hematite. Microflotation tests showed the inefficiency of sodium silicate as a depressant for quartz in aqueous solution even when Zn, Ca, and Mg ions were not present. Activation of hematite by Zn ions was observed, impeding the separation of smithsonite and hematite (iron oxide). Results obtained from the microflotation and zeta potential tests were analyzed based on the speciation diagrams of the reagents and ions studied, as well as published studies.Item Effect of magnesium species on cationic flotation of quartz from hematite.(2020) Lelis, Deisiane Ferreira; Lima, Rosa Malena Fernandes; Rocha, Geriane Macedo; Leão, Versiane AlbisIn the Quadrilátero Ferrífero Region, located in the state of Minas Gerais – Brazil, the utilization of recycled water from the tailing dams in the reverse cationic flotation of siliceous iron ores is common practice. In such process, ore concentrates assigning dolomite (2.5% to 10%) besides quartz in the mineral gangue, do not reach the desired specification for the production of blast furnace pellets (≤2% SiO2) given the loss of selectivity occurring in the separation of quartz from the Fe-bearing minerals, which can be related to a rise in the ions Ca and Mg in an aqueous medium resulting from the dissolution of dolomite. With a view to improving the reverse cationic flotation route for this type of ore, fundamental studies (microflotation trials, zeta potential, adsorption/Fourier-transform infrared spectroscopy) into the effect of the Ca and Mg ions in the cationic flotation with the use of pure quartz and hematite mineral samples were carried out. The results attained with the Ca ions were presented in previous studies by the authors. The current investigation presents the results achieved with the Mg ions, added in water as MgCl2. In the microflotation trials carried out at pH 10.5, amine dosage for maximum recovery of quartz (2.5 ppm) and hematite (50 ppm) was applied. A strong depression of hematite by starch was confirmed, which did not occur with quartz. In the case of the Mg ions, a stronger depression effect was observed, if compared to starch, for the two minerals, starting from a dosage of 10 ppm of MgCl2. After the conditioning of both minerals with 10 ppm of MgCl2, followed by conditioning with 10 ppm of starch, the recoveries attained were negligible (3.5% to 4.4%). Based on thermodynamic data, zeta potential measurements, and infrared spectroscopy, it was concluded that the strong depression effect caused by the Mg ions on both minerals owes to the adsorption of the Mg2+ and MgOH+ species and also the precipitation of Mg(OH)2, where the starch is chemically adsorbed, preventing further amine adsorption. Only quartz recovery was reestablished after the complexation of the Mg ions in the water by ethylenediaminetetraacetic acid having close molar concentrations to the molar concentration of the Mg ions followed by starch conditioning. The results presented indicate the need for a reduction in the concentration of Mg in the water used, before flotation is conducted.Item Influence of Mn2+ ions on depression of quartz and spessartine in gondite ore.(2021) São José, Fábio de; Rodrigues, Guilherme Henrique Gualandi; Pereira, Carlos AlbertoLow-grade manganese ores that are composed of manganese oxides, wad, quartz, iron oxides, gibbsite, and especially of spessartine (Mn3 Al2 (SiO4 ) 3 ) are known as gondite. Spessartine is a mineral with a high content of silica (SiO2 ) and alumina (Al2 O3 ) that causes a decrease of the enrichment in manganese oxide concentrates by flotation, giving this ore more complexity for processing. Thus, by ensuring a higher selectivity between manganese oxides minerals and silicates, the use of gondite reserves becomes viable, and the correct reagent type can be useful for this objective. Moreover, there are few publications devoted to the study of spessartine in flotation. So, this study investigated the effects of Mn2+ ions on quartz and spessartine depression and showed positive results with the reduction of quartz floatability from 7.06% to 1.23% and the spessartine from 27.30% to 17.12% respectively when the Mn2+ (1000 mg/L) was added previously to the depressant. Zeta potential determinations showed that Mn2+ can act as a silicate activator, possibly by facilitating the SiO(OH)3 - adsorption. Infrared spectroscopy analysis revealed absorption bands at 3,450 cm-1 and 3,400 cm-1 frequency for quartz and spessartine and the adsorption of Mn(OH)2 was responsible for this result.Item Effects of calcium and chloride ions in iron ore reverse cationic flotation : fundamental studies.(2019) Lelis, Deisiane Ferreira; Cruz, Daniel Geraldo da; Lima, Rosa Malena FernandesIn this work, the simultaneous effects of Ca2+ and Cl− ions in an aqueous solution at pH 10.5 on the flotation of quartz (the main impurity in itabiritic iron ore) and hematite by starch and amine was investigated. A strong depression in the flotation of both quartz and hematite conditioned with CaCl2 was observed. This effect was higher for hematite than for quartz. Based on zeta potential measurements and the speciation diagram of calcium in aqueous solutions, the physical adsorption of Ca2+ on the surfaces of both minerals was inferred. The infrared spectrum of quartz conditioned with CaCl2 at pH 10.5 was similar to its reagent-free reference spectrum. However, a new band at the wavenumber of 1465 cm−1 was identified in the spectrum of hematite conditioned with CaCl2; this band did not exist in its reference spectrum. This new band may indicate the chemical adsorption of Cl− ions on the hematite surface. The complexation of Ca2+ by ethylenediaminetetraacetic acid enabled complete quartz recovery with amine. For hematite, recovery was partially restored, probably because of the positive chlorocomplexes on the hydrated iron surfaces of hematite, which prevented the adsorption of aminium ions at these sites. Therefore, the selective inverse cationic flotation of itabiritic iron ore at pH 10.5 in water containing Ca2+ is possibly only after complexing them with EDTA.Item Size-dependent kinetics of iron ore reverse flotation.(2020) Braga, Frederic Yann Armache; Luz, José Aurélio Medeiros da; Milhomem, Felipe de OrquizaFlotation experiments under pH 10.5 were performed using quartz/hematite artificial mixtures. The influence of particle size and monoamine unit consumption on the kinetic parameter was analyzed, in a fundamental level. The coarse quartz class was between 212 mm and 600 mm and the fine class was between 74 mm and 212 mm. Hematite particles were graded between 32 mm and 74 mm. Consumption of corn starch was 700 g/t. Consumption of monoamine was 80, 100, and 120 g/t. The first order kinetic model had better fit when compared to the rectangular one, although the correlation coefficient was higher than 0.950 in all cases. The iron recovery to the froth overflow was higher in the presence of coarse quartz and with high amine dosage (maximum value of 0.0307 s 1 ). The analysis of the surface areas available to the collector adsorption proved to be a good tool for the understanding of such complex phenomena. There is a competition between quartz and hematite surfaces for collector adsorption, which is damped by collector excess. This competition can explain the difference in the flotation kinetic parameter. Hematite flotation behavior was dependent on the presence of fine or coarse quartz.Item Complex fringes around magnetite porphyroclasts : growth and deformation history.(2011) Lagoeiro, Leonardo Evangelista; Barbosa, Paola Ferreira; Fueten, FrankDeformed strain fringes in iron formation rocks show complex quartz fiber patterns that grew alongside magnetite porphyroclasts embedded in a matrix of quartz and iron oxides during coaxial to non-coaxial deformation. These rocks have been deformed by a combination of processes involving microfracturing, pressure solution and dislocation glide at temperatures of approximately 300 °C. Detailed microstructural observation and crystallographic analysis show that quartz fiber growth is not controlled by the crystal faces. Quartz c-axis orientations of fibrous quartz indicate that these grains initially grew with their c-axes paralle to the fiber length. Late solid-state deformation of crystallized fibers comprised dislocation glide along basal plane and subsequent recrystallization. This produces aggregates of recrystallized grains consisting of equant to elongated quartz grains with straight and orthogonal grain boundaries.Item Nucleation and growth of new grains in recrystallized quartz vein : an example from banded iron formation in Iron Quadrangle, Brazil.(2010) Lagoeiro, Leonardo Evangelista; Barbosa, Paola FerreiraIntracrystalline microcracks developed in quartz single crystals deformed in greenschist metamorphic conditions. A detailed study of samples collected in tabular to lens shape quartz vein was carried out to investigate how the microcracks initiated and how the microstructures evolved with the progressive deformation. A combination of light and EBSD (electron backscatter diffraction) techniques was used to analyze the microstructures and determine the crystallographic orientation of quartz grains. The crystallographic orientations of microcracks indicate that they might have initiated parallel to the direction of one of the rhombohedral planes of the host crystals. It is suggested that new grains nucleated by rotation of broken fragments from the host grains. c-axes the of host are distributed in a small-circle close to the foliation plane while the c-axes of the new grains in microcracks are more scattered when compared with the host orientations. New grains grew with their c-axes approximately perpendicular to the shortening direction.