Purification of Quartz from East Qinling Granitic Pegmatite for the Preparation of High-Purity Quartz Sand

High-purity quartz is an important raw material for strategic emerging industries, including photovoltaics and semiconductors. To improve the deep removal of impurities from granitic-pegmatite quartz and clarify the effects of calcination–water quenching, a quartz concentrate from the East Qinling Mountains was selected as the feed material. Calcination–water quenching, HF–HCl–HNO3 mixed-acid leaching, and chlorination roasting were systematically investigated. The results showed that calcination temperature markedly affected quartz-sand whiteness and the occurrence of residue-like surface attachments. Treatment at 900 °C substantially reduced these attachments and enhanced subsequent acid-leaching efficiency. At final HF, HCl, and HNO3 concentrations of 1, 2, and 1 mol/L, respectively, Al, Ca, Fe, K, Na, and other impurities were effectively removed, reducing the total concentration of 15 impurity elements to 19.43 μg/g. The inclusion area fraction decreased from 0.97% to 0.38%. Subsequent chlorination roasting at 900 °C further reduced the total impurity concentration to 17.26 μg/g, increased the nominal SiO2 purity to 99.9982%, and decreased the inclusion area fraction to 0.31%. These results demonstrate the potential of East Qinling granitic-pegmatite quartz as a feedstock for photovoltaic-grade high-purity quartz sand.