Study on the Purification of Low-Grade Silicon Ore Via Conventional Roasting Combined with Ultrasonic External Field Enhanced Leaching

To ensure the quality of silicon smelting products, minimizing impurities in the raw silicon ore is essential. This study analyzed the phase transformation and primary phase content of silicon ore subjected to roasting. The experimental results indicated that roasting at 900 °C increased the β-quartz phase content to 93.2%. An ultrasonic field-enhanced leaching method was employed to remove impurities. During the leaching process, mixed organic acids were used as a substitute for inorganic acids, and ultrasonication was employed to improve impurity removal. The effects of leaching temperature, ultrasonic treatment time, and ultrasonic power on the impurity leaching rate were investigated. Response surface methodology was applied to model the leaching process, predict optimal experimental conditions, and optimize the parameters based on actual experimental data. The results revealed that leaching temperature and ultrasonic treatment time significantly influenced the leaching process. The optimized experiment was compared with actual experimental results, and the optimal conditions were determined. Under a leaching temperature of 90 °C, ultrasonic treatment time of 2 h, and ultrasonic power of 200 W, the impurity iron leaching rate reached 96.10%, the aluminum removal rate reached 91.72%, and the SiO₂ purity reached 99.72%. Comparisons of optical microscopy and scanning electron microscopy analyses before and after leaching confirmed that the introduction of ultrasonic leaching effectively removed impurities and purified the silicon ore. This study provides excellent practical guidance for silicon ore purification.