Microwave-assisted glucose production from Ofada-rice husk via alkaline pretreatment and acid hydrolysis: Kinetic and optimization study

This study examined the possibility of converting rice husk substrate into glucose using microwave-enabled alkali pretreatment and acid hydrolysis. The kinetic data were collected using Saeman’s model, while the experimental conditions for the hydrolysis of cellulose to glucose were optimized by response surface methodology using Box Behnken experimental design. As the cellulose dosage increases from 10 g/L to 50 g/L, and the ZnCl2 increases from 2 mg/L to 11 mg/L, the glucose yield increased from 94.19 mg/g to 98.90 mg/g. A comparison of the R square values of all the kinetic models reveals that the conversion of cellulose follows a first-order reaction. A maximum glucose yield of 96.55% (p < 0.05) was obtained at 4.50 mg/L ZnCl₂ and 50 g/L substrate concentration. FT-IR analysis of rice husk confirmed the presence of cellulose, hemicellulose, lignin, and silica with strong O-H, C=O, C=C, and Si-O vibrations indicate both organic and inorganic components. Notably, silica-related peaks (1067, 658, and 587 cm⁻¹) highlight its high silica content, making rice husk valuable for biofuel. These findings confirm that alkaline pretreatment is an effective strategy to enhance the hydrolysis of rice husk, improving glucose yield and reaction kinetics while requiring careful control to minimize degradation losses. KEY WORDS: Acid hydrolysis, Alkali pretreatment, Cellulose, Glucose, Rice husk Bull. Chem. Soc. Ethiop. 2025, 39(10), 1919-1936. DOI: https://dx.doi.org/10.4314/bcse.v39i10.4