Innovative method for rice straw valorization into nanocellulose, lignin and silica

Abstract

Nanocellulose was extracted from rice straw biomass using alkaline pretreatment, H2O2 bleaching and acidic hydrolysis. A novel solution was come up with where the acidic liquid after hydrolysis was used for adjusting the pH of the black liquor from pretreatment to produce lignin- and silica-rich precipitates as functional byproducts. Following this method, crystalline nanocellulose with length < 300 nm and high crystallinity of >80 % can be attained. Silica-rich precipitate was refined using a low temperature thermal treatment process for increased silica purity while maintaining a high degree of amorphous (> 75 %). Economic assessment shows that only around $23 is needed to produce 920 g of crystalline nanocellulose, 1.2 kg of highly amorphous bio-silica and 330 g of soda lignin. Such results show that these novel production methods have high economic efficiencies and should be considered for scaling up or be studied for similar biomass materials.