Preparation of Activated Carbon and Silica Particles from Rice Straw

An efficient three-step process using toluene/ethanol, NaClO2, and KOH has been successfully devised to isolate pure cellulose from rice straw while generating two filtrates as activated carbon and silica precursors. The NaClO2 dissolution filtrate contains oxidized lignin and hemicellulose as carbon precursors as well as sodium carbonates as activating agents for direct carbonization (800 °C) into highly porous (0.90 cm 3/g), high specific surface area (997 m2/g), activated carbon particles (100-500 nm). The KOH dissolution filtrate contains mainly potassium silicate that could be precipitated by dilute acidified poly(ethylene oxide) and calcinated (500 °C) to pure, uniformly sized (100-120 nm), nonporous silica nanospheres. Deriving these additional activated carbon and silica particles along with nanocellulose creates advance materials while fully utilizing all major components in rice straw, the highest quantity agricultural crop byproduct in the world. © 2014 American Chemical Society