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Herein, carboxyl-rich cellulose nanocrystals (CNC) were obtained through a designed TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) mediated oxidation process without any subsequent mechanical treatment, which was proved to be widely suitable for commonly used cellulosic sources, including fibril-like fibers and lignocellulose biomasses. CNC prepared from the acid-free process showed better dispersion stability, less aggregation, higher aqueous UV transmittance and crystallinity compared with that from sulfuric acid hydrolysis process. Furthermore, the residuals in the insoluble precipitate were further conducted ultrasonic treatment and extra CNC was obtained from the oxidized cotton and ramie cellulose while cellulose nanofibril (CNF) was extracted from rice straw and pine powder, attributing to their different native structures. The total yields of nanocelluloses (NCs) were up to 63.2–68.3 %, improving the utilization ratio of the raw materials. This work provided a widely applicable acid- and mechanic-free route in fabricating CNC with inherent carboxyl groups and described an understanding of the relationship between the native structure of raw materials and their products, which is beneficial for improving the application of NCs.

Ionic liquid-based lignocellulose aerogel systems have attracted significant focus in advanced material research due to their intrinsic environment-friendly properties. Use of co-solvent is deemed useful in improving these systems efficiency without affecting reaction dynamics. Herein, a green synthesis strategy is reported to produce highly porous, physically cross-linked lignocellulose aerogel by dissolving lignocellulose biomass obtained from the cotton stalk in 1-allyl-3-methylimidazolium chloride/dimethyl sulfoxide (AmimCl/DMSO) co-solvent system. Samples with different concentrations were treated under both cyclic conventional freezing-thawing conditions (−20 °C to 20 °C) and liquid nitrogen freezing-thawing conditions (−196 °C to 20 °C) followed by solvent exchange and freeze drying. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis of these lignocellulose samples showed that conventional freezing-thawing treated samples exhibit hierarchical 3D open porous “web-like” structure with a low specific surface area and larger dominant pore diameter. On the other hand, use of liquid nitrogen freezing-thawing treatment resulted in the creation of “film-like” porous structure with a higher specific surface area and relatively smaller dominant pore diameter. Quantitative analysis through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA) verified that cyclic freezing-thawing treatment has potential to fix all major components of lignocellulose in a matrix. The proposed strategy is not only environmentally benign but also the cost-effective making an ionic liquid-based system more commercially viable.

Attributed to low cost, renewable, and high availability, cellulose-based aerogels are desirable materials for various applications. However, mechanical robustness and functionalization remain huge challenges. Herein, we synthesized a recoverable, anisotropic cellulose nanofiber (CNF) / chitosan (CS) aerogel via directional freeze casting and chemical cross-link process. The chitosan was performed as strength polymers to prohibits the shrinkage and retains the structural stability of 3D cellulose nanofiber skeleton, endowing the composite aerogel with satisfactory deformation recovery ability (without loss under 60 % stress cycled 100 times). The CNF/CS composite aerogel has ultralow density (∼8.4 mg/cm3), high temperature-invariant (above 300 °C) and high porosity (98 %). The CNF/CS aerogel demonstrates anisotropic thermal insulation properties with low thermal conductivity (28 mWm−1 K−1 in rational direction and 36 mW m−1 K−1 in the axial direction). Moreover, the composite aerogel (water contact angle ∼148°) exhibited outstanding oil/water selectivity and high absorption capacity (82–253 g/g) for various oils and organic solvents. Therefore, the multifunctional CNF/CS composite aerogels are potential materials for thermal management and oil absorption applications.

The aim of this work is to improve the economic value of corn husk, and to make better use of corn husk nanocellulose (NC). Corn husk NC was extracted via acid hydrolysis, TEMPO oxidation and high intensity ultrasonication methods, which was named AH-NC, TO-NC and US-NC, respectively. The NC was carefully characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and particle size and zeta potential analyzer. The results showed the preparation methods didn’t change the main chemical structure of cellulose. The crystallographic form of the three kinds of NC still was cellulose I. However, the effects of preparation methods on the morphology and properties were obvious. Among the three kinds of NC, TO-NC had the largest aspect ratio, and the best dispersion stability in diameter, but very low thermal stability. The AH-NC exhibited the highest crystallinity and best thermal stability, but a small aspect ratio. US-NC possessed low crystallinity and poor dispersion stability.

Cellulose nanocrystal (CNC) was extracted from Carex meyeriana Kunth (CMK) by a combination of TEMPO oxidation and mechanical homogenization method, and used to remove methylene blue (MB) from aqueous solution. After alkali-oxygen treatment, the aqueous biphasic system (polyethylene glycol/inorganic salt) was applied to further remove lignin from CMK. The characteriazation of CNC, and the effects of H2O2 dosage, CNC dosage, adsorption time, and initial MB concentration on the MB removal capacity of CNC were investigated. The results showed that the removal percentage of MB by CNC was raised with the increase of H2O2 and CNC dosage. The adsorption kinetics of prepared CNC followed the pseudo-second-order model, and the adsorption isotherms fitted well to the Langmuir model with a calculated maximum adsoption capacity of 217.4mg/g, which was higher than those of CNC extracted by acid hydrolysis method, indicating CNC extracted from CMK had promising potentials in the field of MB adsorption.