Utilization of Silica in Rice Hulls as Raw Materials for Silicon Semiconductors

Highly pure silicon and silicon compounds are required in high technology products such as semiconductors and solar cells. Rice hulls consist of 71 to 87wt% organic components such as cellulose and 13 to 29wt% inorganic components. In rice hulls, 87 to 97wt% of the inorganic components are silica (Sio(2)). Rice plants absorb water-soluble siliceous ions via the roots. These ions are transported to stems, leaves and rice hulls by sap flow. In rice hulls, siliceous ions accumulate at the cuticle outside of the epidermis. The production of pure silicon compound (SiCl(4)) and of silicon metal as the starting material for purification from rice hull ash is proposed to utilize rice hull SiO(2) in high technology industries. In one process, Sio(2) in rice hull ash reacts with C1(2) on the presence of C and is converted to SiCl(4).