EXTRACTION OF SILICA FROM BURNT PADDY HUSK

Rice husk, an abundant agricultural byproduct, contains a high percentage of silica, making it a potential raw material for sustainable and cost-effective silica production. This study focuses on the extraction of silica from burnt paddy husk using two distinct methods: pretreatment with acid leaching before combustion and non-pretreatment, where the husk undergoes direct combustion. Acid pretreatment, widely used to remove metallic and organic impurities, was expected to enhance silica purity and recovery. However, the results revealed a significant impact of the pretreatment process on silica yield. For the non-pretreated method, the rice husk was combusted directly. Subsequent silica extraction from this ash yielded a silica content of 80%, highlighting the effectiveness of the extraction process in concentrating silica. Conversely, in the pretreatment method, the rice husk was subjected to hydrochloric acid leaching before combustion to remove mineral impurities. While this method successfully reduced impurity levels, the silica content of the extracted product dropped to 75%, indicating significant silica loss during the acid leaching process. The observed reduction in silica yield in the pretreated ash is attributed to dissolution of soluble silica species during acid leaching, structural alterations of silica in the husk matrix, and potential volatilization during combustion. These findings emphasize the need to optimize pretreatment parameters to balance impurity removal and silica retention. The study contributes to agricultural waste valorization and sustainable material production.