Fabricação de vidros utilizando sílica proveniente da cinza da casca de arroz

Abstract

This research aimed to evaluate the use of rice husk ash in the production of glass and later the production of glass microspheres, contributing to a more appropriate destination for this residue. Among the various types of glasses composition, it was chosen to produce soda-lime glasses that are used in a lot of applications, including the production of glass microspheres. During the production process, chemical and thermal treatments were applied to the rice husk in order to obtain a silica with lower metallic impurities, particularly iron and manganese ions, elements known to color the glass, thus allowing the production of glasses with maximum transparency in the visible region of the electromagnetic spectrum. The chemical treatments were applied with two types of acid aqueous solutions, hydrochloric and sulfuric, in two different concentrations, 4 and 10% m/m. Associated with the chemical treatment, the heat treatment was carried out at two different temperatures, 600 and 800º C. Ash composition was evaluated by X-ray Fluorescence measurements and the transparency of the produced glasses was measured by Uv-Vis spectrophotometry. The results showed that the chemical treatment using H2SO4 and HCl acids decreased the percentage of metal ions. Specifically, for the case of chemical treatment using 10% of HCl, the measured transmittance spectra were very close to the reference sample: glass made using sand as a source of silica. On the other hand, both chemical treatments significantly improved glass transparency when compared to untreated samples. With the samples optimized in terms of transparency, the production process of microspheres was performed by the flame spheroidization method. In the production of microspheres, it was successful for particles with average diameter around 125 micrometers. The presented results show that the chemical treatment is efficient in the removal of impurities that cause color in the glasses and that these glasses can be used in the production of microspheres.