Removing boron from the diamond wire saw silicon powder by MgF2-sintering synergized with Na2CO3-enhanced refining to prepare low-boron silicon

Recycling environmentally hazardous diamond wire saw silicon powder (DWSSP) to prepare low-boron silicon is crucial for environmental pollution and waste resources recycling. For reutilization, the decomposition of impurity-containing SiO2 layers and the removal of boron are the two main issues that need to be addressed. Therefore, the addition of MgF2 to DWSSP for sintering to damage the containing-impurities SiO2 layers and remove harmful boron was first studied. The results showed the SiO2 layer was effectively decomposed by reaction with MgF2 and the removal rate of harmful boron impurity was 86.9 % at 1300 degrees C for 120 min with 20 wt. % MgF2 addition. Subsequently, the effect of Na2CO3 on the removal of boron impurity in the refining process was analyzed, finding that 10 % Na2CO3 addition enhanced the boron removal rate to 95.6 % at 1600 degrees C for 60 min with CaO/SiO2 ratio of 1.2. Finally, the removal mechanism of harmful B impurities via MgF2-sintering synergized with Na2CO3-enhanced refining was analyzed. This work provides a simple and feasible alternative for recycling DWSSP to prepare low-boron silicon as feedstock for solar-grade silicon preparation.