From biomass to films: dual DES strategy enabling high-performance cellulose films

Efficient separation of cellulose from lignocellulosic biomass is essential for the development of sustainable cellulose-based materials. In this study, a two-step deep eutectic solvent (DES) pretreatment strategy was applied to selectively remove hemicellulose and lignin, thereby obtaining cellulose with high purity and structural integrity. The DES-treated residue exhibited an increased crystallinity index (55.72% → 74.36%) and specific surface area (0.5931 → 2.3452 m 2 /g), confirming the disruption of the dense biomass structure and the degradation of polysaccharides in non-crystalline regions. The recovered lignin showed lower molecular weight (Mw = 2972 g/mol, Mn = 1401 g/mol) and better homogeneity (PDI = 2.12). The purified cellulose was subsequently employed to fabricate cellulose-based films using [Emim][OAc]/DMSO (1:4) as solvent. The films exhibited excellent properties, including tensile strength of 25.6 ± 1.5 MPa, elongation at break of 40.5%, high transparency (90.73%), water content of 67.47%, and weight loss rate of 63.94% after 30 days. Structural analysis revealed compact crystalline regions, good compatibility between solvent and cellulose, and stable thermal and interfacial properties. These results demonstrate that dual DES pretreatment enables high-purity cellulose isolation and facilitates the preparation of biodegradable films with promising potential in agricultural applications.