Enhanced acid leaching of metallurgical grade silicon in hydrofluoric acid containing hydrogen peroxide as oxidizing agent

The effect of hydrogen peroxide as a novel oxidizing agent on purifying metallurgical grade silicon (MG-Si) by leaching with hydrofluoric acid was investigated as a function of temperature, leaching duration, stirring and hydrofluoric acid concentration. It was found that adding oxidizing agent resulted in enhancing the extraction of impurities from MG-Si as compared to that without oxidizing agent, especially for some non-dissolving elements in the acid like copper. After 2 h of leaching MG-Si with an acid mixture composed of 1 mol L− 1 hydrofluoric acid and 2 mol L− 1 hydrogen peroxide, the purity of MG-Si increased from 99.74 to 99.99%, which was higher than 99.97% obtained without hydrogen peroxide addition. Based on cracking shrinking model, the leaching MG-Si with the mixture was under chemical reaction control. Furthermore, to investigate the reaction mechanism on leaching MG-Si, the micro-structural evolutions of MG-Si before and after exposure to each etchants were revealed.