Separation of silicon carbide and silicon powders in kerf loss slurry through phase transfer separation method with sodium dodecyl sulfate addition

Abstract

Kerf loss slurry, generated during the silicon wafer slicing for solar cell fabrication, contains silicon carbide (SiC) and silicon (Si) powders. This study investigated the addition of sodium dodecyl sulfate (SDS), a surfactant collector, for the separation of SiC and Si powders in kerf loss slurry by using phase transfer separation method. Methyl isobutyl carbinol (MIBC) and water were used as the two phases. First, the characteristics of SiC and Si powders transferred from water phase to MIBC phase without and with SDS addition were investigated separately. Second, the separation of SiC and Si powders in kerf loss slurry was conducted. The results indicated that the effectiveness of SDS addition on improving the transfer from water phase to MIBC phase was better for the SiC powder than for the Si powder. The transferred fraction of SiC increased to >90% below pH 5 and reached near 100% at pH 3 when 0.5 kg/ton SDS was added, whereas that of Si increased to >25% below pH 5 and reached nearly 80% at pH 3 at the same SDS dosage. SDS addition improved the separation of SiC and Si in kerf loss slurry at an optimal pH of 5. Higher SDS dosage aided in higher SiC recovery in the MIBC phase and higher Si purity in the water phase. When 2 kg/ton SDS was added, the purity and recovery of SiC in the MIBC phase were 80.7% and 98.3%, respectively, and those of Si in the water phase were 97.0% and 70.1%, respectively. By adding SDS at a specific pH and dosage, the transfer of SiC powders from the water phase to MIBC phase can be selectively improved; thus, the separation of SiC and Si powders can be enhanced. Moreover, the effective separation of SiC and Si powders can be achieved by conducting a one-step phase transfer separation operation.