Recovery of silicon carbide from waste silicon slurry by using flotation

The amount of waste silicon slurry increases as the wafer production raises. The slurry is generally disposed using incineration or land-filling. Separating high-purity SiC from waste silicon slurry can reduce costs for enterprises and assist in waste reuse and recycling. In this study, flotation was applied to separate SiC and Si from waste silicon slurry through hydrophilicity and hydrophobicity of the particle surface. By controlling the concentration of hydrofluoric acid and the oxidation reduction potential of the two stages flotation, the SiC can be separated from Si. The optimal condition of first stage flotation is 0.8 mol/L of HF at -400 mV, while 0.6 mol/L of HF and -300 mV was applied in the second stage. Under these conditions, approximately 52.8% of SiC was recovered with the grade of 98.1 %.