A review of hydrometallurgy techniques for the removal of impurities from metallurgical-grade silicon

Hydrometallurgy is considered a promising method to produce solar-grade silicon (SOG-Si) from metallurgical-grade silicon (MG-Si) due to its advantages of low cost, simple operation, and easy control. Researchers have investigated different hydrometallurgy techniques for impurity removal from MG-Si. This study systematically reviews hydrometallurgy techniques for the removal of impurities from MG-Si and provides perspectives in this field. Traditional leaching techniques, including single-acid leaching, successive acid leaching, and mixed acid leaching, are summarized. These methods face challenges for preparing high-purity silicon because of the insoluble impurities in MG-Si. Intensive methods for improving impurity removal in hydrometallurgical processes, including adding oxidizing agents, introducing external fields, and increasing the impurity exposure to the etchants, are classified and discussed. The combinations of secondary refining processes and hydrometallurgical processes are efficient in removing insoluble impurities from MG-Si. Representative research topics and the results of these combination methods are classified and summarized. It is expected that this review will help researchers select appropriate hydrometallurgy techniques for producing low-cost SOG-Si.