Piranha Solution-Enabled Removal of Carbon Species from Silicon Kerf Loss for Improved Raw Silicon Recovery

High Resolution Image Download MS PowerPoint Slide The photovoltaic (PV) industry continues to expand rapidly, and the volume of silicon (Si) waste has surged, leading to substantial environmental challenges. This waste primarily comprises Si powder from kerf-loss slurry generated during wire-saw wafer cutting and scrap fragments produced during the Si ingot growing process. To lower the cost of crystalline Si production and reduce environmental pollution, recovering and purifying Si waste has become a subject of great interest. In this study, the effect of hydrogen peroxide as a novel oxidizing agent in the purification of metallurgical-grade Si through leaching with sulfuric acid was examined at various ratios. Specifically, the purification of silicon kerf using piranha solution with a mixture of sulfuric acid and hydrogen peroxide was investigated with a focus on carbon reduction. The results demonstrate that increasing the oxidative strength of the piranha solution, particularly by adjusting the hydrogen peroxide ratio, led to progressive purification. Treatments with higher peroxide concentrations, especially at a 1:1 ratio, yielded significant improvements in crystallinity, reductions in surface impurities, and substantial decreases in carbon content, confirming the efficiency of oxidative leaching for recycling kerf-derived silicon waste. Characterization using PXRD, FTIR, FESEM, and EDS revealed the initial presence of multiple contaminants such as native silicon oxide, metallic residues, and carbonaceous impurities. The reduction of impurities was further confirmed through carbon analysis conducted for the three different solution ratios.