High-Purity Silica Produced from Sand Using a Novel Method Combining Acid Leaching and Thermal Processing

The production of high-purity silica from natural sand is crucial as it is a primary material in the high-grade silicon industry. This paper presents a new processing method for purifying sand silica. This process is a subsequent combination of annealing thermal and acid etching. First, samples of Algerian Sahara sand were subjected to rapid thermal annealing in an infrared furnace at 900 °C for 1 h. Subsequently, the samples were etched using an aqueous solution containing hydrofluoric and hydrochloric acid. This last acid etching step is designed to eliminate any gettered impurities that may have been migrated during the annealing process. Various characterization techniques were employed to evaluate the effectiveness of this impurity removal process, such as X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy. The results show a substantial reduction in all metallic impurities in silica after two successive purification cycles, improving the purity from 94.63 to 99.87% and the removal efficiencies for critical eleven contaminants such as Fe (93.92%), Al (98.41%), and Ca (> 99.99%).