Effect of Grinding Liberation on Recovery of Silicon from MG-Si Waste Slag by Flotation

Abstract

Metallurgical-grade silicon-re ned waste slag (MGSRS) was produced during the MG-Si re ning production process, which occupies huge amounts of land resources, caused the loss of nearly 110,000 tons of MG-Si every year. Though, it is of great signi cance to recover the elemental silicon in MGSRS.However, because silicon is tightly wrapped by slag and di cult to separate, resulting in the di culty of silicon recovery. In this study, silicon recovery powders were obtained through the process of grinding liberation and otation separation. The effect of grinding time on the liberation of MGSRS and the otation recovery of silicon was studied. The liberation mechanism of MGSRS was further discussed. The results showed that the liberation degree of silicon particles was 79.45% (grinding for 15 min), which was 7.94% higher than that of silicon particles after 5 min grinding time, and 77.15% of the silicon particles were fully liberated. The otation recovery of silicon can increase from 10.5-78.7% with the appropriate collector. Mechanism study shows that during the grinding process, silicon was separated along the (111) surface, and Ca 2 Al 2 SiO 7 had the largest amount of liberation along the (211) plane. More unsaturated sites of aluminum and calcium ions were observed on the silicate surface, which were favorable for adsorption with the reagent and bene cial to the silicon recovery. These results indicated that the silicon and slag of MGSRS can be su ciently separated through grinding and otation, and the purity of recovered silicon is about 70%. The silicon resources in MGSRS were recovered economically and could be used as the raw materials for the preparation of silicon alloy and high purity silicon.