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 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 Calcination and characterisation studies of a Brazilian manganese ore tailing.(2014) Pereira, Mário J.; Lima, Margarida Márcia Fernandes; Lima, Rosa Malena FernandesThis paper discusses the systematic analysis of the results of calcination as a function of size fraction performed on a sample of Brazilian silicate–carbonate manganese ore tailing at 800 °C. The raw materials and the corresponding calcination products were analysed using several analytical techniques, including determination of density, specific surface area and porosity, chemical analysis and X-ray diffraction. Themorphology and chemical composition of the calcination products were analysed by using scanning electronic microscopy equipped with energy-dispersive X-ray spectrometer (SEM/EDS). Results indicate that the manganese ore tailing consists of silicates, namely, spessartine (Mn3Al2(SiO4)3), tephroite (Mn2(SiO4)) and rhodonite ((Mn,Fe,Mg,Ca)5(SiO3)5) and rhodochrosite (MnCO3). The loss of CO2 and OH during the thermal decomposition of the carbonate (rhodochrosite and dolomite) and hydrated minerals (kaolinite, muscovite and antigorite) in air atmosphere at 800 °C resulted in: (1) decrease of the specific surface area and porosity, (2) increase in the density and Mn grade from 27.6% to 32.2% and (3) increase in SiO2 grade from 26.7% to 30.1%. These results indicate that this material is within the chemical specifications of Fe–Si–Mn alloy.