Effect of Magnesium Addition on Removal of Impurities from Silicon by Hydrometallurgical Treatment

摘要

Hydrometallurgical treatment of silicon is an effective process for the removal of metallic impurities for producing solar grade silicon feedstock. In the present research, the removal of impurities from silicon is studied through the addition of Mg into a commercial silicon, its solidification, and acid leaching. The effect of concentration of HC1, temperature and leaching duration on the removal of impurities are studied. It is shown that the impurities such as P, Fe, Al, Ti, Ca,... are effectively removed through the applied method and Mg improves the segregation and the removal of the impurities. Scanning electron microscopy examination of the samples indicates the disintegration and dissolution of Mg_2Si phase in acid leaching which causes the chemical and physical removal of the impurities existing in the phases between the silicon grains. It is shown that the leaching process rate can be optimized through the control of the acid leaching conditions.