Study on the Purification Process of Waste Silicon Powder in the Synthesis Process of Organosilicon Monomer

Due to waste contact and waste slurry generated in the production process of silicone monomer after copper extraction of the residue (WSP), a significant accumulation leads to environmental pollution and waste of resources. Therefore, there is an urgent need to explore a suitable method to recover the silicon resources therein. In this study, the morphology and composition of WSP are systematically investigated, and the optimized method of removing impurities by combining low-temperature oxidative roasting and mixed acid leaching is proposed, by taking advantage of the low-temperature oxidizability of amorphous carbon as well as the corrosive effect of HF on the SiO 2 layer. Carbon removal using oxidative roasting of WSP is analyzed, and the effects of different roasting temperatures and times on carbon removal are explored. The effects of HF concentration, acid leaching temperature, and time on the impurity leaching rate are studied. The results show that the removal of impure carbon is as high as 98.46% when roasted at 500 °C for 3 h in the atmosphere. The optimal conditions for mixed-acid leaching are as follows: HF concentration of 4 mol·L −1 ; leaching temperature of 70 °C; 2 h period. The removal rates of Cl, Ca, and Fe are superior to 99%, and the removal rates of Al and Ti are superior to 94%. This simple method is key for the recovery of silicon resources from WSP.