Abstract: As a pre-treatment unit for preparing solar-grade silicon (SG-Si) by metallurgic method,wet purification could remove most metallic impurities and non-metallic impurities,such as boron.Experiment researched a new method to remove boron from SG-Si with mixed hydrofluoric acid-sulfuric acid as leaching agent and with organic solvent methanol as post-treatment agent.Samples were characterized by ICP and other analysis methods.When SG-Si powder had been leached at optimized conditions as follows:mass fraction of sulfuric acid was 55%,mass fraction of hydrofluoric acid was 7%,reaction temperature was 70 ℃,reaction time was 4 h,and liquid-solid mass ratio 8∶1,it was found that mass fraction of impurity boron in SG-Si was reduced to 3.867×10^-6 from 6.893×10^-6 and the removal rate was 41.9% after acid leaching;on the basis of the former procedure,mass fraction of impurity boron was reduced to 3.84×10^-6 and the removal rate was 44.29% when treated with organic solvent.Experiment proved the feasibility of the method and provided a new reference for researching on the pre-treatment of SG-Si by hydrometallurgy.

Key words: solar-grade silicon, hydrometallurgy, organic solvent, purification