EM - Escola de Minas

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Characterization and concentration by selective flocculation/magnetic separation of iron ore slimes from a dam of Quadrilátero Ferrífero – Brazil.
(2020) Lima, Rosa Malena Fernandes; Abreu, Francisco de Paula Vitor Fonseca
In this paper the results of size, chemical and mineralogical characterizations as well as the concentration tests performed with a slimes sample of iron ore from a dam at the Quadrilátero Ferrífero in the state of Minas Gerais, Brazil are presented. The sample was constituted by 75 % of slimes (particles –10m). The main minerals identified by X-ray diffractometry and thermal analysis were: goethite, hematite, quartz and kaolinite. The sample grades were: Fe (∼51.4 wt.%.), SiO2 (∼15.1 wt.%), Al2O3 (∼3.4 wt.%), P (0.097 wt.%) and LOI (∼7 wt.%). During the optimized bench testing condition of selective flocculation/magnetic separation (pH = 10.5, sodium silicate and corn starch =50 g/ton, magnetic strength =3575 G) by experimental statistical planning design, the mass recovery was of 48.4 %. There was an increase of 8 % in Fe grade and a decrease of 50 % in both SiO2 and Al2O3 grades when compared with the feed. Agglomeration studies with the obtained concentrate will be performed in future.
Effect of magnesium species on cationic flotation of quartz from hematite.
(2020) Lelis, Deisiane Ferreira; Lima, Rosa Malena Fernandes; Rocha, Geriane Macedo; Leão, Versiane Albis
In 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.
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 Fernandes
In 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.

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