Flotation separation of SiC from wastes in the silicon wafer slicing process

In the silicon wafer slicing process from a single silicon crystal, the crystal is sliced by using a wire saw with the lubricating oil containing SiC powders. After the slicing, a mixture of SiC and the ground Si is discharged from the process. The particle sizes of SiC and Si are 10 pin and I pin respectively, and the weight ratio of the two is about 9: 1. The SiC and Si particles are separated from the lubricating oil with a filter press, and the particles are burned to yield SiC and SiO2. From the viewpoint of waste minimization and resources preservation, the valuable SiC particles should be separated from SiO2 particles and recovered. The flotation method can be applied for this purpose. The cationic surfactants used are dodecyltrimethylammonium chloride and trimethyloctylammonium chloride. The adsorption amount of the surfactants was measured for SiC and SiO2 particles. The flotation behavior of SiC and SiO2 was investigated by changing pH. gas flow rate and flotation time in the presence of dodecyltrimethylammonium chloride. The purity and yield of SiC was also studied in the flotation process comprising of roughing, cleaning and scavenging steps. The values of purity and yield of SiC were 99.7% and 96.7% respectively in the total flotation process.