Upgrading low grade quartz up to 99 plus quartz by chemical leaching

Abstract

Vein quartz is the major source of silicon for manufacturing of solar cells, computer chips, and silicon carbide. The aim of the investigation was to enhance the purity of exporting semi processed vein quartz by acid leaching. Particle size reduction processes crushing, grinding and milling increase the amount of iron in the quartz and this secondary iron concentration needs to be removed to produce more purified quartz. Thus, in this research quartz was obtained using raw quartz near Badulla area. Raw quartz was processed using primary and secondary crushers and then it was separated into four size fractions (125μm, 500μm, 1mm, and 8mm). Acid leaching was employed for iron removal. Atomic Absorption Spectrophotometer (AAS) was used to measure iron content before and after the leaching. As preliminary studies, Hydrochloric acid (HCl) and Nitric acids (HNO3) were employed for the leaching and Liquid- Solid ratio was 5:1. According to the results which were observed as preliminary study HCl was chosen for the leaching and effect of the HCl for the removal of iron was examined. The particle size of the quartz, leaching time, concentration of the reagents was used as parameters. Leaching was done under normal atmospheric conditions (250C, 1atm). The acid leaching of vein quartz resulted in a reduction of 60 – 65% iron from the original value. Since iron dissolution is a photochemical reaction practical was conducted in controlled conditions (250 – 500 lux). Progressive amount of leaching (60 – 65%) of iron from quartz was obtained under following conditions, a higher concentration of HCl (5M), smallest size fraction (0- 125μm), and 60 hrs. leaching time. Under these conditions, higher purity of quartz powder can be achieved.