Complete valorization of bamboo biomass into multifunctional nanomaterials by reactive deep eutectic solvent pretreatment: Towards a waste-free biorefinery

The introduction of nanotechnology into conventional biorefinery will facilitate complete valorization of lignocellulosic biomass. In this work, a microwave-assisted deep eutectic solvent (DES) pretreatment was developed for one-pot fractionation of bamboo biomass into three scalable fractions (cellulose-rich residue, lignin and recovered DES), which were then respectively upgraded to three value-added bio-based nano -materials, namely lignin-containing cellulose nanofibrils (LCNFs), lignin nanoparticles (LNPs) and carbon quantum dots (CDs). After the mild and rapid DES pretreatment (130 degrees C, 20 min), 51.0% cellulose-rich residue was recovered accompanied by 90.6% delignification ratio. The cellulose-rich residues were mechanically fibrillated into LCNFs with a width of 5-20 nm. In-situ esterification of carboxylic acid groups from DES with cellulose hydroxyl groups improved the hydrophobicity of LCNFs. The LCNFs film prepared exhibited excellent hydrophobic (water contact angle of 103.3 degrees). In-situ esterification, condensation and cleavage reactions of lignin during DES fractionation enhanced its amphiphilicity and facilitated lignin self-assembly into LNPs with di-ameters of 30-75 nm. Furthermore, using the recovered DES as carbon precursors, CDs were successfully pre-pared by a typical hydrothermal method, which provides a new approach for the disposal of waste DES. In short, the proposed waste-free biorefinery scheme realizes the complete valorization of bamboo biomass into bio-based multifunctional nanomaterials, which can be further applied in various downstream fields.

Automated summary

A microwave-assisted deep eutectic solvent (DES) pretreatment was developed to fractionate bamboo biomass into three scalable fractions for the production of value-added bio-based nano-materials. Cellulose-rich residue was recovered and upgraded into lignin-containing cellulose nanofibrils (LCNFs), lignin nanoparticles (LNPs), and carbon quantum dots (CDs) using in-situ esterification and hydrothermal methods.