Utilization of High-Silicon Iron Ore Tailings for 4N8 High-Purity Quartz Powder Production via Two-Stage Acid Leaching

This study investigates the process mechanisms for preparing 4N8 high-purity quartz powder from high-silicon iron ore tailings. Silicon concentrate obtained by wet high-intensity magnetic separation was used as the raw material, with impurities removed through a two-stage acid leaching process. The effects of acid concentration, temperature, time, and liquid–solid ratio on impurity removal were examined. Thermodynamic analysis shows that HF enhances the dissolution of Fe and Al impurities. In the first stage, response surface optimization determined the optimal conditions: acid concentration of 11.69 mol/L, temperature of 99.5 °C, and reaction time of 6.3 h, yielding SiO₂ purity of 99.949%. Kinetic analysis indicates Fe leaching is controlled by a chemical reaction (activation energy: 66.69 kJ/mol), while Al leaching is limited by internal diffusion (activation energy: 13.64 kJ/mol). The second-stage leaching, conducted at 10 mol/L acid concentration, 250 °C, and a liquid–solid ratio of 5:1 for 9 h, further reduced impurities. The final 4N8 high-purity quartz powder was obtained through fine grinding and high-temperature treatment. These findings provide theoretical guidance for the high-value utilization of iron ore tailings in applications such as semiconductors and photovoltaics.