Reduction of Iraqi Sand to Produce Silicon with High Purity

Abstract

This study deals with extraction of silicon from Iraqi sand. The sand was supplied by State Company for Mining Industries from Um-Erdhuma Formation in Anbar Province. It is found that Iraqi sand has 98% of silica (SiO₂).Pyrometallurgy and hydrometallurgy processes were applied for extraction of silicon by reduction and leaching respectively. Reduction was carried out in an alumina crucible by using magnesium powder with particle size of 75μm as reducing agent under argon gas. Several parameters were studied to determine the best results that affected the extraction of silicon. These parameters involved the reduction temperatures (750,850,950) ̊C and ratio of Mg/SiO₂ (2:1, 2.5:1, 3:1).The best conditions for the reduction of Iraqi sand to produce silicon were, at 850 ̊C, 2:1 Mg/SiO₂ with 99.3% purity and at 950 ̊C, 3:1 Mg/SiO₂ with 99.2 %purity. Leaching processes were done for purification of produced silicon by using 4:1 volume ratio of 4M HCl and 4M CHᴈCOOH respectively for one hour at 70 ̊C. Additional purification step was done by using H₂SO₄ acid, which was diluted by 1:4 ratio for three hours at 100 ̊C.