Thermodynamic analysis and experimental verification for silicon recovery from the diamond wire saw silicon powder by vacuum carbothermal reduction

Recovering silicon from waste material is profoundly significant in terms of making profit and encouraging development within the photovoltaic manufacturing industry. Eliminating oxygen is essential for the preparation of high purity silicon. However, a substantial amount of oxygen exists in diamond wire saw silicon powder (DWSSP), creating a barrier for the effective silicon recovery caused by a nonnegligible silicon loss. In this paper, amorphous silicon dioxide and the Si core - SiO2 shell structure was systematically characterized and confirmed. A thermodynamic calculation was then carried out to analyze the reduction reaction probability of silicon dioxide by vacuum carbothermal reduction. The results indicated that the reduction reaction could occur under the vacuum condition with lower temperature, while it could not under that of the atmospheric condition. Further, experiments were conducted to verify the reliability of the thermodynamic analysis, which are keeping in good agreement with thermodynamic results. Finally, the results confirmed that the vacuum carbothermal reduction method is a feasible alternative for silicon recovery from the DWSSP. This research provides contributions to understanding the recovery of silicon resources from DWSSP with the vacuum process, making it competitive with existing silicon recovery methods