DEMIN - Departamento de Engenharia de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/510
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Resultados da Pesquisa
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 Precipitation of a layered double hydroxide comprising Mg2+ and Al3+ to remove sulphate ions from aqueous solutions.(2018) Guimarães, Damaris; Rocha, Natasha Cristina Machado da; Morais, Rafaela Aparecida Pedro de; Resende, Andréia De-Lazarri Bicalho Peixoto; Lima, Rosa Malena Fernandes; Costa, Geraldo Magela da; Leão, Versiane AlbisThis work presents an alternative route to remove sulphate ions from aqueous solutions, which is simple and fast, and its efficiency of sulphate removal is slightly influenced by temperature (26 °C–70 °C) and pH (4–12). The lowest residual sulphate concentration was about 60 mg L−1, which was observed in continuous experiments using wastewater (26 °C, pH 6 and initial sulphate concentration of 630 mg L−1). All these outcomes together have not been observed in the current most used processes of sulphate precipitation, i.e. gypsum and ettringite precipitation. Sulphate removal experiments were carried out in the batch and continuous systems using synthetic solutions. In these conditions, about 75% of sulphate ions were removed for an initial ion concentration of 1800 mg L−1. A continuous test was also performed using a wastewater sample in addition to a synthetic solution. The system reached steady-state conditions after four residence times (40 min) in the experiment with synthetic solutions, whereas three residence times (30 min) were necessary for the tests with the wastewater (initial sulphate concentration of 630 mg L−1). In the latter case, the sulphate removal efficiency was approximately 90%. The characterisation of the experimentally precipitated solids was carried out by DRX, FTIR, SEMEDS, elemental analysis and thermal analysis. These techniques showed that, except in pH 4, the sulphate removal process occurred due to the precipitation of a layered double hydroxide, comprising Mg2+ and Al3+ as its metallic ions and nitrate (due to the salts used for precipitation) and sulphate anions occupying its interlayer space.Item Effect of EDTA on quartz and hematite flotation with starch/amine in an aqueous solution containing Mn2+ ions.(2016) Lelis, Deisiane Ferreira; Leão, Versiane Albis; Lima, Rosa Malena FernandesIn this paper, a detailed study of the influence of Mn2+ ions on quartz and hematite flotation (at pH 10.5 with starch/amine as depressor/collector) in the absence and presence of ethylenediaminetetraacetic acid (EDTA) is presented. By using zeta potential measurement and a careful analysis of manganese species present in water for dosages in which manganese hydroxide precipitated, we confirmed that the depression of both minerals by Mn2+ ions is due to the following: (i) the adsorption of Mn hydroxy complexes (Mn2(OH)3+ and Mn(OH)+); (ii) Mn2+ and mainly (iii) the precipitation of Mn(OH)2 on mineral surfaces. These effects hindered the adsorption of amine species on the surfaces of the minerals (quartz and hematite). EDTA was used to complex Mn2+ to restore the recoveries of both minerals. This was confirmed by the species distribution diagrams of Mn and EDTA–Mn in water. Conditioning with starch followed by amine at pH 10.5 enabled a selective separation of these minerals.Item Remoção de sulfato de efluentes industriais por precipitação.(2011) Ferreira, Bruno Christiano Silva; Lima, Rosa Malena Fernandes; Leão, Versiane AlbisO objetivo deste trabalho foi estudar a remoção de íons sulfato, encontrados em efluentes de diversas atividades do setor mínero/metalúrgico. Os processos de remoção de sulfato desses efluentes são, em geral, caros e com baixa eficiência de remoção para essa espécie. Foram estudadas duas alternativas de tratamento para soluções ricas em sulfato. A primeira consistiu na investigação da remoção do íon em pH ácido, na forma de jarosita. Na segunda, foi estudada a remoção do sulfato como etringita, em pH alcalino. A etringita mostrou-se uma boa opção para o tratamento de efluentes líquidos contendo sulfato, pois apresentou baixa solubilidade em água em pH acima de 11,5. Em seguida, foi investigada a precipitação química de sulfato em soluções sintéticas contendo 1.500 mg/L do íon, em temperatura ambiente (22±1º C), observando-se remoções próximas de 85% em sistemas contínuos de precipitação. Esses estudos mostram a redução dos teores finais de sulfato a valores inferiores a 250 mg/L, ou seja, abaixo do que é recomendado pela legislação brasileira.Item Mine water treatment with limestone for sulfate removal.(2012) Silva, Adarlêne Moreira; Lima, Rosa Malena Fernandes; Leão, Versiane AlbisLimestone can be an option for sulfate sorption, particularly from neutral mine drainages because calcium ions on the solid surface can bind sulfate ions. This work investigated sulfate removal from mine waters through sorption on limestone. Continuous stirred-tank experiments reduced the sulfate concentration from 588.0 mg/L to 87.0 mg/L at a 210-min residence time. Batch equilibrium tests showed that sulfate loading on limestone can be described by the Langmuir isotherm, with a maximum loading of 23.7 mg/g. Fixed-bed experiments were utilized to produce breakthrough curves at different bed depths. The Bed Depth Service Time (BDST) model was applied, and it indicated sulfate loadings of up to 20.0 g (SO4)2− /Lbed as the flow rate increased from 1 to 10 mL/min. Thomas, Yoon–Nelson and dose–response models, predicted a maximum particle loading of 19 mg/g. Infrared spectrometry indicated the presence of sulfate ions on the limestone surface. Sulfate sorption on limestone seems to be an alternative to treating mine waters with sulfate concentrations below the 1200–2000 mg/L range, where lime precipitation is not effective. In addition, this approach does not require alkaline pH values, as in the ettringite process.Item Manganese and limestone interactions during mine water treatment.(2010) Silva, Adarlêne Moreira; Cruz, Flávio Luciano dos Santos; Lima, Rosa Malena Fernandes; Teixeira, Mônica Cristina; Leão, Versiane AlbisManganese removal from mining-affected waters is an important challenge for the mining industry. Addressed herein is this issue in both batch and continuous conditions. Batch experiments were carried out with synthetic solutions, at 23±2 ◦C, initial pH 5.5 and 8.3 g limestone/L. Similarly, continuous tests were performed with a 16.5 mg/L Mn2+ mine water, at 23 ◦C, initial pH 8.0 and 20.8 g limestone/L. Calcite limestone gave the best results and its fine grinding proved to the most effective parameter for manganese removal. In either synthetic solutions or industrial effluents, the final manganese concentration was below 1 mg/L. A change in limestone surface zeta potential is observed after manganese removal and manganese carbonate formation was suggested by IR spectroscopy. The conclusion is that limestone can remove manganese from industrial effluents for values that comply with environmental regulations.Item Influência da adição de fluorsilicato de sódio sobre a flotabilidade de minerais de manganês e quartzo com oleato de sódio.(2011) Andrade, Emily Mayer de; Leão, Versiane Albis; Lima, Rosa Malena FernandesEsse trabalho apresenta e discute resultados de ensaios de microflotação e determinação de potencial zeta dos minerais rodonita, rodocrosita e quartzo, na presença de fluorsilicato e oleato de sódio em pH 9 e pH 11. Verificou-se que, para concentrações de Na2SiF6 abaixo de 10mg/L, houve maior depressão do quartzo em relação à rodonita no valor de pH 9 e que a flotabilidade da rodocrosita foi pouco afetada para os valores de pH 9 e 11. Resultados de medidas de potencial zeta versus pH indicaram que o ponto isoelétrico da rodonita (pH=2,8) coincidiu com o reportado em literatura, enquanto que os valores determinados para quartzo (pH<2,0) e rodocrosita (pH=10,8) apresentaram pequena divergência. Para os três minerais, a presença de oleato e/ou silicato de sódio foi capaz de tornar mais negativa a magnitude do potencial zeta dos três minerais em meio básico. Fundamentando-se nos resultados experimentais e, também, na especiação dos reagentes estudados (oleato e fluorsilicato de sódio), foi possível fazer inferências sobre mecanismos de adsorção dos mesmos sobre os três minerais de interesse.