Study on process optimization and mechanism of quartz sand acid leaching and purification

With quartz sand (SP1) from a certain place as the study object, its treatment conditions were optimized and the removal effect of key impurities was analyzed by adopting a stepwise single-acid or mixed-acid experimental scheme. The experiment had three stages: pretreatment, acid washing purification, and post-treatment. The SP1 samples and those subjected to optimal acid washing conditions were characterized using qualitative or quantitative tests such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry. The result showed when quartz sand was treated with 70 mL of hydrofluoric acid in a single-acid system at 120°C for 2 hours, with the purity reaching 99.9963%. For the mixed-acid system, the volume ratio of hydrofluoric acid, hydrochloric acid, and nitric acid was maintained at 1:6:2, and acid leaching was conducted under constant temperature conditions at 120°C for 5 hours. Under these parameters, the contents of aluminum and iron were reduced to 15.23 and 0.15 µg/g, respectively, with the purity of the acid-washed quartz sand reaching and the production yield reaching 99.9964% and 82.11%, respectively. Based on the comprehensive consideration of purification effectiveness and process economy, the volume ratio of hydrochloric acid, nitric acid, and hydrofluoric acid selected was 1:6:2, and acid washing purification was performed for a reaction time of 5 hours. The purity of the acid-washed quartz sand reached 99.996%, and the impurity removal mechanism of hydrogen fluoride on quartz sand was clarified, which provided a theoretical basis for the standardized production of quartz sand.