Preparation and characterization of functional nanocomposites based on lignin nanoparticles and cellulose nanofibers from holistic rapid-formic acid fractionation of bamboo

The urgent need for using renewable resources instead of fossil sources has attracted extensive research activities on the development of biodegradable materials from biomass. Due to the highly recalcitrant nature of lignocellulose, it is essential to develop an efficient fractionation approach which may facilitate the subsequent conversion. Herein, in a holistic rapid-formic acid fractionation of bamboo chip under the optimized conditions at 145 °C for 45 min of cooking, with a solvent ratio of 85:15 (formic acid:water, v/v), wood:solvent ratio of 1:7, relatively pure hemicelluloses, lignin and cellulose were sequentially obtained as fractionated streams. The bamboo-originated cellulose, as a raw material, was easily converted into cellulose nanocrystals (CNCs) using TEMPO oxidation in a short time in comparison to wood Kraft pulp. The dissolved lignin was processed into nanoparticles (lignin-NPs), which exhibited sphere morphology and a uniform particle size distribution. Dispersions of CNCs and lignin-NPs were prepared and further filtrated to result in nanocomposite membranes. The nanocomposite membranes, in varied compositional ratios of CNC and lignin-NP, were elaborately characterized with SEM, TG-DSC, and mechanical property analysis. These all-bamboo-originated nanocomposite membranes showed to possess superior tensile strength and thermal stability as compared to pure CNC-based membrane. This study presents a promising and green pathway in achieving novel high value-added wood-based nanomaterials.