The SiO2 grade in quartz sand decreases by quartz sand size becoming finer, so washing and desliming of crude quartz sand is necessary before next step.
Scrubbing is the way to remove film iron and impurity minerals on the surface of quartz by mechanical force and crush these mineral aggregate. The quartz sand gets further purification by classification. There are two kinds of methods rob scrubbing and mechanical scrubbing.
The separation of mica and quartz is difficult, the effective methods: anionic collector in acid condition and anionic - cationic collector in alkaline condition. The purification of quartz sand can reach 99% after scrubbing, desliming, magnetic separation and flotation.
Dilute acid had a significant effect on removing iron and aluminum, and concentrated acid for the removal of titanium and chromium, and mixed acid for mineral impurity. Control various factors of acid leaching should be based on quartz final grade requirements, and as far as possible reduce the acid concentration, temperature and dosage to achieve quartz purification.
A quartz sand dressing plant in Yunnan with the main component was quartz sand accounting for 95-97%; siliceous cement accounting for 8-23%, the impurity minerals were hematite, limonite, etc. accounting for about 1-3%. The plant adopted screen classification - dry magnetic separation - dosing strong scrubbing-flotation process, the final indexes: SiO2 ≥ 97.62%, Fe2O3 ≤ 0.24, Al2O3 ≤ 1.11%.The poor indexes seriously affect the production and economic benefit. Therefore, the plant commissioned the Xinhai to reform technology. By dressing tests, Xinhai decided to adopt the screen classification - dry magnetic separation - dosing strong scrubbing - acid leaching process, specific index comparison as follow:
|Comparison of Reformation||Process||Concentrate Index|
|Before Reformation||screen classification - dry magnetic separation - dosing strong scrubbing-flotation process||SiO2≥97.62%，Fe2O3≤0.24，Al2O3≤1.11%|
|After Reformation||screen classification - dry magnetic separation - dosing strong scrubbing - acid leaching process||SiO2≥99.4%，Fe2O3≤0.052，Al2O3≤0.048%|
After the technical reformation, the purified quartz sand met the quality requirements of silicon powder, and it can be used in ceramic, paint, metal casting industry after the superfine grinding.