Simple and High-Effective Purification of Metallurgical-Grade Silicon Through Cu-Catalyzed Chemical Leaching

摘要

A simple and effective method for the removal of impurities from large-sized particle metallurgical-grade silicon (MG-Si) powders based on Cu-catalyzed chemical leaching (CuCCL) has been proposed and discussed. The leaching behaviors of the main metallic impurities (Fe, Al, Ca, Ti, Ni, V and Cu) were investigated using various leaching approaches. The typical precipitates at Si grain boundaries before and after leaching were observed and analyzed by scanning electron microscopy and energy dispersive x-ray spectroscopy. The leaching results show that the order of impurity removal efficiency, from highest to lowest, is CuCCL?>?HF-H~(2)O~(2)leaching?>?HF leaching. After CuCCL, the total metal impurity concentration can be reduced from 6759?ppmw to 193.41?ppmw. The numerous micro-scale “channels” introduced by CuCCL are beneficial for the removal of impurities, especially for the non-dissolving metal impurities, such as calcium and aluminum. The results indicated that CuCCL is promising as an industrial purification method to produce solar-grade silicon.