Fully upgrade lignocellulose to three nanomaterials by combinational pretreatment: Refining straw waste to pesticide nanocarrier

Abstract

To achieve the maximum value from lignocellulosic biomass, an integrated biorefinery based on molecule-level design is required. In this study, a combination of hydrothermal pretreatment (HTP) coupling deep eutectic solvent (DES) pretreatment was proposed to produce three upgraded products, namely hemicellulose-derived activated nanocarbon (ANC), lignin nanosphere (LNS), and lignin-containing cellulose nanofiber (LCNF) pesticide nanocarrier, from rice straw. The hydrothermal filtrate, which consists of 100% hemicellulose, was converted into value-added nanocarbon by in-situ carbon sequestration. The upgraded nanocarbon exhibited an excellent specific surface area (2692.3 m2 g−1) and a high degree of graphitization, which value-added attributes could increase revenue to integrated biorefinery. The subsequent DES extraction increased the phenolic –OH content and further aggregated the lignin condensed structure, which facilitated lignin nanosphere preparation by the self-assembly process. Meanwhile, the DES swelling of cellulose facilitated the nanofibrillation of LCNF, which was used as a pesticide carrier to improve pesticide utilization efficiency by simple cationic modification. The residual lignin with functional groups facilitated the crosslinking between the lignin fragments and cellulose fibers by hydrogen bonding interactions, which endowed LNCF highly entangled network and unique lignin properties. The functionalized LCNF exhibited enhanced adhesion and unique anti-UV ability for pesticide deposition and retention. This work realized the all-components upgrading of lignocellulose and inspired the development of sustainable and viable biorefineries.