Complete conversion of lignocellulosic biomass into three high-value nanomaterials through a versatile integrated technical platform

Abstract

An integrated technique of hydrothermal pretreatment coupling with deep eutectic solvent (DES) extraction was tailed to cleanly fractionate lignocellulose into three usable forms, i.e., water-soluble hemicellulose, cellulose-rich and lignin fractions, which were further upgraded to three nanomaterials, i.e., activated nanocarbons (ANCs), lignin-containing cellulose nanofibers (LCNFs), lignin nanospheres (LNSs) respectively. Almost 100% hemicellulose was solubilized in the hydrothermal pretreatment, which was used as carbon source to produce ANCs with rather high specific surface area (about 2680 m2 g−1) through in situ carbonation followed by activation. Cellulose-rich fraction was used to produce LCNFs with high aspect ratio (about 150) using facile mechanical refining. While the clean lignin fraction with enhanced amphiphilic properties was used to produce LNSs (223 nm diameter) using self-assembly method. The related mechanism was that condensed lignin could still be extracted by DES due to its excellent lignin solubility. The resulting lignin amphiphilicity provided a powerful driving force to enhance the self-assembly process thus compact LNSs was obtained. Meanwhile, the DES-swelled cellulose structure significantly facilitated the subsequent mechanical disintegration for LCNFs production. In this work, the proposed integrated technique platform realized the complete utilization concept of lignocellulosic biomass, and also provided three high-value nanomaterials product streams for downstream application towards an industrial relevant process.