Green production of thermally stable and dispersible cellulose nanofibrils from wheat bran using a recyclable deep eutectic solvent–Fenton system

Wheat bran is a cellulose-rich agricultural byproduct; however, its utilization remains limited owing to poor processability. Herein, a combined deep eutectic solvent (DES)–Fenton system was developed to produce thermally stable and dispersible cellulose nanofibrils (CNFs) from wheat bran. The effects of the solid–liquid ratio (1:10, 1:25, 1:50, and 1:100 g/g), DES molar ratio (1:1, 2:1, and 3:1), and Fenton reagent amount (0.45, 0.9, 1.35, and 1.8 μmol/g DES) on the particle size, yield, zeta potential, and carboxyl content of the CNFs were examined, and their morphology, microstructure, and thermal stability were characterized. Under the optimal conditions (solid–liquid ratio 1:50 g/g, DES molar ratio 1:1, and Fenton reagent amount 0.9 μmol/g DES), CNFs were obtained, with a particle size of 285.13 nm, zeta potential of −38.07 mV, relative crystallinity of 43.97%, and maximum decomposition temperature of 345.3 °C. DES could be recycled and reused seven times to produce acceptable CNFs with a particle size of 575.37 ± 21.89 nm and yield of 24.76% ± 3.15%. A preliminary techno-economic analysis using Aspen Plus V14 and Aspen process economic analyzer revealed that at an 80% DES recovery rate, the static payback period was ~0.76 years, indicating the economic feasibility of the DES–Fenton process. DES replenishment was the major cost contributors, and improving DES recovery could significantly enhance the economic performance of the process. These findings suggest DES–Fenton treatment as a green and efficient method for the valorization of wheat bran, an agricultural waste, into CNFs.