Efficient Recovery of Silicon from Silicon Slag by Interface Modification Combined with Flotation

A large amount of silicon slag is inevitably produced during the smelting and purification process of silica sand. The recycling of silicon from industrial silicon slag has become an urgent problem in the silicon production industry. In this study, the aim is to separate and recover silicon with purity above 95% by flotation method and to ensure recovery rate above 50%. The hydrofluoric acid was used to modify the surface of silicon slag. The silicon was separated from the silicon slag by flotation. The floating samples were further purified with hydrochloric acid. It improved the silicon grade of the samples by about 5%. Recovered silicon samples were obtained with a high recovery rate and grade. The composition and interfacial distribution characteristics of the silicon slag were investigated. The flotation conditions were investigated from three aspects: the type of collector, the size of the mineral particles, and the pH of the slurry. The feasibility of using hydrochloric acid to improve the silicon grade was verified by XRF. The flotation mechanism was investigated by zeta potential analysis, calculation of flotation agent composition, contact angle testing, and XPS characterization.