Enhanced crystallinity and thermal properties of cellulose from rice husk using acid hydrolysis treatment

Cellulose was extracted from rice husk (RH) using an integrated delignification process using alkaline treatment and acid hydrolysis (concentrated HNO₃) for lignocellulosic biomass dissolution. Cellulose yield and quality were assessed through analysis of lignocellulosic content, thermogravimetric, functional group, X-ray diffraction, and surface morphology. HNO₃ treatment showed an increment (2.01-fold) in the cellulose content and some enhancement in the crystallinity of cellulose (up to 40.8%). A slight increase was observed in thermal properties from 334.6 °C to 339.3 °C. Economic analysis showed chlorine extraction produce higher cellulose recovery (58%) as compared to HNO₃ (26.7%) with the total cost of operation using HNO₃ was double compared to chlorine extraction. The economic feasibility of HNO₃ can be improved using various progress in the pre-treatment process, chemical recycling and cellulose recovery process since adopting it is crucial for environmental sustainability.