Hydrometallurgical purification of solar cell silicon scraps through chemical etching with HF-HNO3-H2SO4

The top-cut scraps of silicon ingots are a major source of waste in the production of polysilicon solar cells. In this study, purification of solar cell silicon scraps through chemical etching was carried out. Certain parameters, such as solvent types, etching temperature, ultrasonic power, and ultrasonic frequency were investigated. The optimal conditions were determined to be HF – H2SO4 – HNO3 mixed acid, reaction temperature of 60 °C, ultrasonic frequency of 45 kHz and ultrasonic power of 240 W. Chemical analysis demonstrated that iron was removed. Inclusions were removed under the observation of a microscope. Results indicated that the solar-cell silicon scraps were purified at a low cost.