Cellulose Nanocrystal Preparation via Rapid Hydrolysis of Wood Cellulose Fibers Using Recyclable Molten Ferric Chloride Hexahydrate

Abstract

Cellulose nanocrystals (CNCs) are clean and sustainable materials that have drawn significant attention in academia and industry because of their unique physicochemical properties. However, realizing economical and environmentally friendly production of CNCs remains a challenge. In this study, we proposed an innovative strategy to fabricate CNCs, which involves the acid hydrolysis pretreatment of wood cellulose fibers using innocuous and recyclable ferric chloride hexahydrate (FeCl 3 • 6H 2 O). During the molten FeCl 3 •6H 2 O treatment, the degree of polymerization (DP) of the cellulose fibers sharply decreased, along with the transformation of cellulose I to cellulose II crystallites. Molten FeCl 3 •6H 2 O quickly hydrolyzed cellulose fibers within 5 min at 80 °C, inducing a rapid decrease in the DP from 922 to 196, and the water-insoluble solid (WIS) retention reached 80.1%. CNCs were successfully produced from the mechanical disintegration of the WIS with a low energy input. Hence, the yield of CNCs is consistent with that of the WIS. Interestingly, the CNCs exhibited typical cellulose II crystallites, which were significantly different from those of the cellulose feedstock (cellulose I). Detailed characterization revealed that the CNCs had tunable numberaveraged heights of 10.4−26.9 nm and high thermal stability (a maximal weight loss temperature of 327 °C). Most notably, FeCl 3 • 6H 2 O was easily recycled from the hydrolysate after hydrolysis, with a high recovery of 94.0−94.5 wt %, using simple concentration and crystallization technologies. Thus, this study proposes a novel production technology for CNCs that is both economical and ecofriendly, providing new ideas for clean and large-scale production of CNCs.

Insights into the critical role of anions in nanofibrillation of cellulose in deep eutectic solvents

“…Similarly, recycled molten ferric chloride with strong acidity has been reported as an excellent solvent system for the preparation of CNC from hydrolyzed cellulose. It can penetrate into the cellulose molecular chain, destroy the hydrogen bond between cellulose molecules, and promote the disintegration of CNC (Yang et al 2023). However, molten ferric chloride can cause excessive damage to the cellulose crystal structure and corrode equipment, if the conditions of LA/ZnCl 2 DES treatment of cellulose were properly regulated, this might be a very good systems for preparing CNC.…”

Construction of composite films using carbon nanodots for blocking ultraviolet light from the Sun

“…30–33 More generally, interest in natural resources and their derivatives as sources of carbon has gradually increased over recent years. 11,21,34–36 Chitin is a natural biopolymer with wide sources and abundant reserves, 37,38 and its deacetylation product, chitosan, is widely utilised because of its abundant reserves, non-toxicity, good biocompatibility, and ease of biodegradation 39 and its use as a source of carbon has been gradually developed. 17 Polyvinyl alcohol (PVA) is a biodegradable, water-soluble, low-cost, film-forming and stable polymer, which has the potential to replace non-biodegradable polymers.…”

Effect of pH on water durability of cellulose nanofiber-reinforced starch film

“…Recycling of cellulose has been reported to be possible by dissolving in different chloride salts, such as LiCl [26,27], ZnCl 2 [28], CaCl 2 [29], and FeCl 3 [30]. Moreover, NaOH/ Urea solution [31][32][33] and ionic liquid [34][35][36] have also been widely reported to be used for recycling cellulose.…”