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

Goethite waste, originated in the hydrometallurgy of zinc, was charact erized and recycled, in combination with raw materials, for producing glass-ceramic (GC) materials. Four base compositions were prepared wit h 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 nucleati on and crystallization temperatures and the activation energy of the c rystallization process were determined by differential thermal analysi s. 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-r ay diffraction and fluorescence analysis were performed on the glasses and GC samples and the crystalline phases characterized. The percenta ge of crystallinity was determined as a function of the temperature an d duration of the thermal treatment. The fractional factorial experime ntal approach was carried out on the 20 wt% Fe2O3 CoMPosition with the aim of evaluating the influence of the nucleation temperature and tim e, the crystallization temperature and time and the presence of a redu cing agent on the glass devitrification process.