Innovative technology for the production of high-purity sand silica by thermal treatment and acid leaching process

摘要

The production of high purity silica out of natural sand plays a critical role as a starting material in the industry of glass and high grade silicon. In this paper, we expose a novel processing method for the purification of sand silica. This method is a subsequent combination of thermal treatment and acid leaching. Firstly, samples of Tunisian natural sand were submitted to a rapid thermal annealing in an infra-red furnace under O-2 atmosphere at fixed temperature and time 1000 degrees C and 1 h, respectively. Subsequently, the samples were soaked in an aqueous acid solution composed hydrofluoric acid and a hydrochloric acid concentration. This last acid leaching step was intended to remove the gettered impurities during the annealing step. Various characterization techniques such as optical absorption, energy dispersive X-ray analysis, electronic paramagnetic resonance analysis and atomic absorption spectroscopy were used aiming to evaluate the effectiveness of this impurity gettering technology. The results show substantial reduction in all metallic impurities in silica after three successive purification cycles improving the purity from 99.7 to 99.9%.