Rice husk silica derived nanomaterials for sustainable applications

Rice husk (RH) is an abundant and sustainable waste biomass. Silica-rich RH can be converted to biofuels (e.g., bio-oil, vapors) and biochars simultaneously via thermochemical processes such as pyrolysis, gasification. Bio-oil can be further upgraded into renewable biofuels (e.g., biodiesel) by using the RH-derived catalysts. Meanwhile, vapors from organic matters decomposition can be converted to value-added syngas for energy purpose or chemical synthesis by using the RH silica materials, which are used for gas cleaning or catalytic reforming. In general, the applications of RH-derived biochars mainly include soil remediation, pollutants removal, silicon battery materials, and so on. This paper reviewed recent progresses in the syntheses of RH silica materials and their sustainable applications, especially in energy and environment functional materials. As for the environmental issues, the RH-silica materials can remove heavy metals and organic contaminants in soil amendment, wastewater treatment, and gas purification by means of adsorption, catalysis and integrated processes. In summary, biomass with high content of silica can become a potential resource of low cost precursors for the production of high value-added silica/silicon materials for practical applications.