Effect of wet oxidation on recovery of silicon from wire saw slurry by liquid–liquid extraction

• Liquid–liquid extraction of Si in slurry is realized.
• Significant effect of wet oxidation is found.
• Optimal degree of oxidation is identified.
• Optimal {O} wt% is found to follow a linear relation with Si content.

Recovering high purity silicon from wire saw slurry generated in silicon wafer production is of great importance, and process suitable for large scale application is yet to be developed. Liquid–liquid extraction method using kerosene as the oil phase was explored in the present study. Wet oxidation of the samples was carried out to find its effect on the purity of recovered Si and its yield. We found that the liquid–liquid extraction is an effective method to recover Si from the slurry if it is wet oxidized to an appropriate degree. When the fraction of Si consumed in oxidation is around 0.034, it can be recovered with high purity and yield. This corresponds to an oxygen content in the Si–SiC mixture which follows the relation {O}wt%=4.0×10-3(1+9Siwt%). The mechanism for the effect of wet oxidation on the recovery of Si and the rationality for the existence of optimal degree of oxidation were discussed.