Investigations on hydrobromination of silicon in the presence of silicon carbide abrasives as a purification route of kerf loss waste

Hydrobromination of three types of silicons (reagent grade silicon (RG-Si), metallurgical grade silicon (MG-Si), and kerf loss silicon (KL-Si)) has been investigated in a flow reactor with and without abrasive grains of silicon carbide (SiC) under various conditions. All the silicons reacted with HBr to form bromosilanes around 400 °C, irrespective of the presence or absence of SiC. The reactivity of each Si sample was evaluated with respect to the conversion of HBr, while the purity of products was analyzed after hydrolyzing them to silicon dioxide. Metal impurities such as Al, Fe, and Ni in the starting materials were dramatically reduced in the hydrolyzed products. The addition of SiC did not cause any increase in impurities. Rather, it resulted in an improvement of the reaction kinetics in a temperature region of 350–400 °C, probably as a result of better heat transfer in the reactant owing to the high thermal diffusivity of SiC. This demonstrates that the bromination reaction is effective to extract pure silicon from kerf loss waste even where SiC is present.

► Hydrobromination of different types of silicon materials. ► Purification of sawing waste without pre-removing silicon carbide particles. ► Kinetic investigation on Si bromination in the precence and absence of silicon carbide.