Hydrometallurgical purification of metallurgical grade silicon

Abstract

The effects of the particle size of ground metallurgical grade silicon (MG-Si), the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size less than 0.1 mm was most effective for acid leaching; the extraction yield of impurities was increased by 9% with HF leaching compared with HCl leaching and HNO 3 leaching, and increased by 7% with ultrasonic stirring compared with mechanical stirring. The principle of hydrometallurgical purification of metallurgical grade silicon under ultrasonic fields was also discussed.

Effect of oxidizing agents on the hydrometallurgical purification of metallurgical grade silicon

“…3a). A similar effect of particle size has been reported by Ma et al (2009), Yu et al (2007, Zhang et al (2009) andDietl (1983). They have shown that the metallic impurities precipitate at the grain boundaries and it is required to grind the MGSi to a size well below the grain diameter to expose the metallic impurities on the surface of the particles thus favoring effective contact with the lixiviant.…”

“…For the removal of Fe and Ti from such alloy phases it is required to leach the MGSi with hydrofluoric acid (Santos et al, 1990). Despite our findings and those of Ma et al (2009), Santos et al (1990 were successful in removing~50% Al, 80% Fe, 25% Ca and 98% Ti by treating MGSi with 2 M HCl at 50°C for 8 h, which is a relatively mild condition as compared to the present investigation. However, these authors did not report the nature of the Fe and Ti alloy phases present in their MGSi samples.…”

“…Since 1927 (Tucker, 1927) a number of research groups have reported the purification of MGSi by acid leaching. Ma et al (2009) have shown that extractions increased with decreasing particle size, and obtained better extraction results with HF as compared to HCl or HNO 3 . Yu et al (2007) have investigated the influence of different acids, their concentration, reaction time and particle size on the extraction of iron and aluminum.…”

“…The drawback of successive leaching or the use of mixed acids is that it results in high production costs and a long production time. and Ma et al (2009) have studied the ultrasonic acid leaching of MGSi, and found that leaching under ultrasonic conditions is more effective than under simple magnetic stirring. Xie et al (2011) have successfully obtained more than 90% extraction of iron by pressure leaching of MGSi with hydrochloric acid.…”

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

“…Margarido et al made a dynamic mechanism analysis for the Fe-Si alloy on the refining under acid leaching route and pointed out that the acid leaching process conformed to the cracking shrinking model controlled by chemical reaction [10][11]. Ma et al pointed out that the extraction yield of impurities increased by 9 % with HF leaching more than with HCl and nitric acid (HNO 3 ) in the leaching of MG-Si [12].…”