Estudo da influência do óxido de cálcio nas reações de estado sólido na produção de agregado cerâmico a base de aluminossilicatos e resíduo do processo Bayer

Abstract

The most important worry involving the generation of industrial waste is associated with the effects those materials can have on the environment and human health, considering that the dangerous waste produced by the industry requires particular care and attention, because if managed improperly, it can become a serious environmental threat. Therefore, this paper demonstrates the studies conducted to recycle the residue from the Bayer process, as a raw material in the production of synthetic aggregate, intended for civil construction. Furthermore, this paper has analyzed the influence of calcium oxide in the solid state reactions during sintering in the production of ceramic aggregates based on residue from bauxite processing because this oxide, besides being a melting material, also influences the formation of glass with lower viscosity, and may positively influence the mechanical strength of the material. For the conformation of the aggregates a composition based on bauxite residue and silica was adopted with and without the addition of calcium oxide. The pellets were produced in a rotating cylinder and sintered at temperatures of 1180, 1200 and 1250 °C with a burn time of 3 hours. For the characterization of the raw materials the techniques of X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TG) were employed. For the characterization of the aggregate, scanning electron microscopy (SEM), XRD and DSC tests were performed on the formulations composed of bauxite residue and clay with and without the addition of calcium oxide. The physical and technological properties determined were: Water absorption, apparent porosity and apparent specific mass. The results of this paper indicate that bauxite residue can be used as a source of alternative raw material for the production of synthetic ceramic aggregate. The results obtained also prove that the use of calcium oxide directly influenced the solid state reactions, especially in the mullite formation reaction. Therefore, the production of synthetic aggregate with the addition of calcium oxide proved to be a promising destination for the Bayer process residue.