Abstract: To address the problem that physical beneficiation can hardly remove minerals on particle surfaces,inclusions, and impurities within the crystal lattice during the preparation of quartz sand from quartz sandstone,quartz sandstone from a certain area in Hebei with a SiO2 content of 98.07% was used as the raw material.After pretreatment by crushing,grinding classification,and magnetic separation to a particle size of 0.212~0.106 mm,a quartz sand flotation concentrate with a SiO2 content of 99.67% was obtained by flotation purification.The purification effect under the synergistic action of acid leaching and chlorination roasting was systematically studied.The results show that during acid leaching,hydrofluoric acid made a prom inent contribution to impurity removal.When 0.8 mol/L hydrofluoric acid and 4 mol/L phosphoric acid were mixed at a volume ratio of 1∶1 and used for leaching at 80 ℃ for 4 h,the removal rates of Al,Fe,and Ti reached 85.28%,67.64%,and 16.75%,respectively.To further improve the purification efficiency,chlorination roasting was introduced.Quartz sand was mixed with 3% sodium chloride and subjected to chlorination roasting at 900 ℃ for 4 h,and a process system of "acid leaching pretreatment (primary acid leaching)-chlorination roasting-secondary acid leaching" was established.Finally,the removal rates of Al,Fe,and Ti increased to 89.86%,79.43%,and 56.18%,respectively;The SiO2 content of the quartz sand increased from 99.670% to 99.979%,and the total impurity content decreased to 212.1 mg/kg.This study reveals the synergistic mechanism of acid chemical etching and chlorination roasting on impurity migration/replacement and surface dissolution-mediated removal in quartz,providing an efficient and feasible process route for purifying quartz sandstone to prepare high-purity quartz sand.

Key words: quartz sandstone,high-purity quartz sand,acid leaching,chlorination roasting,impurity removal,mixed acid