Liquid ‑ nitrogen quenching induced pore evolution and quantitative structure– activity modeling for high‑purity quartz purification

Chemical purification is the key route to produce high-purity quartz sand (≥ 4N), yet the relationship between micro-pore evolution and purification efficiency remains unclear. In this study, natural quartz sand was subjected to liquid-nitrogen quenching and hydrothermal acid leaching, and the effects of calcination temperature, calcination time, quenching frequency, and mechanical grinding on pore distribution were systematically investigated. A quantitative predictive model describing the multi-factor interactions between pore structure, impurity removal rate, and quartz purity was established. The results showed that thermal expansion and phase transformation are the dominant factors for pore evolution, and connectivity microcracks can significantly improve the purity and impurity removal rate of quartz sand. Thermal expansion causes the specific surface area of quartz sand to decrease to 45%–55% of the raw sample, while high temperature also promotes the segregation of impurity elements. Phase transformation has a significant impact on pore connectivity, and the highest purity of acid-washed quartz sand can reach 99.93%, with an average removal rate of aluminum elements being approximately 80%. Partial correlation analysis confirmed the strong correlation between different pore types. The regression model follows a quadratic polynomial framework, with R² values ranging from 0.896 to 0.994, indicating its high reliability. This study elucidated the quantitative structure-activity relationship between pore structure and purification performance, providing a theoretical basis for the optimization of the high-purity quartz sand production process.