Complete utilization of passion fruit husk into multiple functional materials by the combination of ionic liquid and organic acid pretreatment

As the depletion of fossil energy, the utilization of renewable energy especially the lignocellulosic biomass has become increasingly critical. However, the recalcitrant nature of lignocellulose presents substantial challenges in its efficient processing. In this study, the combination of ionic liquids (ILs) and organic acid emerges as a promising, sustainable, and cost-effective method for lignocellulose pretreatment. This study investigated the pretreatment of passion fruit husks, an agricultural by-product, using a system of IL 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and levulinic acid (LA), a biomass-derived carboxylic acid, to effectively separate cellulose and lignin. Co-solvents such as ethanol, water and acetone were applied to reduce the viscosity of the pretreatment system and improve mass transfer efficiency during biomass pretreatment. The optimal pretreatment condition was found to be 3 h reaction time, 130 °C, and ethanol as co-solvent at 10 wt% of the pretreatment system. The cellulose-rich residues were prepared into lignin containing nanocellulose (LCN), which were then utilized as emulsifiers in the preparation of Pickering emulsions. These emulsions demonstrated exceptional storage stability over prolonged periods. Additionally, the lignin-rich pretreatment solution was incorporated as an active additive into polyvinyl alcohol (PVA) to produce composite films, which exhibited excellent UV-blocking capabilities and mechanical strength (46.37 MPa for tensile strength and 747.62 % for the elongation at break at 40 wt% lignin). This sustainable biorefinery strategy enables the comprehensive conversion of passion fruit husk biomass into bio-based multifunctional nanomaterials, offering promising applications in diverse industrial sectors. • [BMIM]Cl−levulinic acid could remove lignin while retain cellulose. • Lignin-containing nanocellulose (LCN) was obtained from the cellulose rich residues. • LCN was utilized as emulsifiers in the preparation of Pickering emulsions. • Lignin rich pretreatment solution was incorporated into PVA to obtain composite films. • Composite films displayed excellent UV-blocking capabilities and mechanical strength.