CRYSTALLIZATION OF GLASSES OBTAINED BY RECYCLING GOETHITE INDUSTRIAL-WASTES TO PRODUCE GLASS-CERAMIC MATERIALS

Goethite waste, originated in the hydrometallurgy of zinc, was characterized and recycled, in combination with raw materials, for producing glass-ceramic (GC) materials. Four base compositions were prepared with an Fe2O3 content ranging from 15 to 25 wt%. The mixtures were melted at 1400-1450-degrees-C and quenched to obtain the glass. The nucleation and crystallization temperatures and the activation energy of the crystallization process were determined by differential thermal analysis. The glass samples were nucleated at 660-degrees-C for times ranging from 1 to 4 h and crystallized at 800-900-degrees-C for 1 to 4 h. X-ray diffraction and fluorescence analysis were performed on the glasses and GC samples and the crystalline phases characterized. The percentage of crystallinity was determined as a function of the temperature and duration of the thermal treatment. The fractional factorial experimental approach was carried out on the 20 wt% Fe2O3 CoMPosition with the aim of evaluating the influence of the nucleation temperature and time, the crystallization temperature and time and the presence of a reducing agent on the glass devitrification process.