Síntese e caracterização da magnetita obtida a partir de rejeito de Bauxita da mina de Juruti, Pará, Brasil

Abstract

This research presents a study on the use of solid and inorganic bauxite tailings from the exploration of this ore in the city of Juruti in the state of Pará. The material was used as the basis for the production of a Ferrite with a spontaneous magnetism, Magnetite (Fe3O4), through the development of a chemical route. The bauxite tailings has about 62% of hematite, which can be converted to a magnetite and allows an application for this waste that is discarded in the mine tailings basins, causing environmental risks. The use of this residue in the synthesis of Magnetite (Fe3O4) represents a proposal to be added to the efforts to solve this environmental issue. The synthesis process started with a treatment with hydrochloric acid (HCl), which was able to aggregate Fe III as ferric chloride (FeCl3), the material obtained was dried at 80 °C for 48 hours. Then, ammonium hydroxide (NH4OH) and ammonium acetate (CH3COONH4) were used to obtain the iron acetate hydroxide (IAH), by magnetic stirring and drying at 80 oC for 12 hours. The last step consisted in the thermal treatment at 600 oC under nitrogen gas flow (N2) for 2 hours with a constant flow rate of 2 L/min. With this route of synthesis, from bauxite tailings, a sample containing three distinct crystalline phases was obtained: Magnetite (Fe3O4), Hematite (α-Fe2O3) and Anatase (TiO2). The samples were characterized by X-ray diffraction and Infrared spectroscopy. The research was able to determine a chemical route to obtain Magnetite in a laboratory scale, which generates the possibility of exploitation of the tailings on an industrial scale.