Cellulose最新文献

In this work we show that it is the molecular weight in a variety of natural and treated plant yarns that is the dominant factor in controlling both the rate of dissolution and the dissolution activation energy in the ionic liquid 1-ethyl-3-methylimidazolium acetate. We have used an alkali treatment (sodium hydroxide) to primarily reduce the molecular weight of three natural plant yarns (hemp, cotton and flax) in order to investigate how dissolution depends on molecular weight, composition and crystallinity. Dissolution experiments were carried out on both the raw and alkali-treated yarns. Chemical composition, crystallinity, and molecular weight were determined for all these six yarns. After dissolution, the partially dissolved yarns were coagulated in water, resulting in a composite material with an undissolved inner core surrounded by a dissolved and coagulated outer skin region. The growth of this dissolved and coagulated fraction was tracked using optical microscopy, showing it to increase with dissolution time and temperature. Time–temperature superposition was found to hold in all cases, allowing a dissolution activation energy to be determined. The width of the outer skin of the coagulated region was found to be directly proportional to the square root of the dissolution time, demonstrating that the limiting factor for dissolution is the diffusion of the ionic liquid. Finally, all the mercerised yarns were found to dissolve faster than their natural versions, suggesting that molecular weight is a contributing factor in affecting the speed of dissolution.

Carboxymethylcellulose ammonium salt (NH₄-CMC) is a water-soluble cellulose derivative. Although less commonly used than sodium salts, NH₄-CMC offers the advantage of leaving no residual metal salts after firing, making it suitable for applications such as batteries. Another key feature of NH₄-CMC is its conversion to a water-insoluble form upon heating. It is generally assumed that heating releases NH₃ from NH₄-CMC, yielding water-insoluble acidic CMC (H-CMC). However, the detailed reactions have not been characterized. In this study, NH₄-CMC was heated at 105 °C, 150 °C, and 170 °C to examine the behavior of the ammonium salt and the development of water-insoluble properties. At 105 °C, the polymer remained water-soluble after 1 h, but became nearly insoluble after 3 h of heating. At 150 °C, complete water insolubility was achieved within 1 h. A reduction in nitrogen content was observed during heating, indicating NH₃ elimination and the formation of H-CMC. Furthermore, amide formation was also strongly inferred. The formation of H-CMC and amide under heating causes insolubility in water, despite the presence of some unreacted ammonium salt. Slight depolymerization was observed within this temperature range.

In this study, a green and efficient ultrasound-assisted alkali-acid synergistic strategy was developed for the high-yield extraction of cellulose from tea residue, combined with a recyclable aminosulfonic acid recovery system to achieve green and low-carbon production. Orthogonal experiments were conducted using a NaOH-H₂O₂ system (4% NaOH, 2% H₂O₂, solid–liquid ratio 1:10, ultrasonication for 50 min) optimized the alkali pretreatment, achieving a preliminary extraction yield of 34.07%. This was followed by sulfamic acid hydrolysis under optimized conditions (15% sulfamic acid, solid–liquid ratio 1:15, ultrasonication for 70 min), increasing the cellulose yield to 75.46%. Through a multi-step recovery process comprising dilution and sedimentation, flocculation-assisted precipitation, filtration separation, rotary concentration, and crystallization collection, the average recovery rate of aminosulfonic acid reached 94.68%. Characterization by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) confirmed that the extracted cellulose has an intact molecular structure, high crystallinity, and good thermal stability. This work provides a promising green pathway for the high-value utilization of agricultural industrial waste.

This study presents a combination of three different pretreatments of sugarcane bagasse (SCB) aimed at increasing levoglucosan (LGA) yield during fast pyrolysis. SCB samples were subjected, individually or in combination, to the following pretreatments: distilled-water leaching, torrefaction at 290 °C for varying residence times (5, 7.5, and 10 min), and fungal decay employing white rot (Trametes versicolor) or brown rot (Coniophora puteana) over durations, ranging from 2 to 12 weeks, respectively. The combined pretreatment of torrefaction (5 min) and fungal degradation by C. puteana for 12-weeks considerably reduced the hemicellulose (by 61.04%) and lignin (by 56.61%) content of the SCB, while increasing the cellulose concentration by 153.4%, leading to enhanced LGA production during fast pyrolysis. Additionally, the optimal pretreatment conditions involved water-leaching followed by torrefaction for 7.5 min at 290 °C, combined with and the action of the white rot fungus Trametes versicolor during 4 weeks which after rapid pyrolysis leads to the highest LGA yield of 11.59%. The combined pretreatments effectively improved SCB’s chemical composition and enhanced the properties of its bio-oil produced during fast pyrolysis process.

A sustainable cellulose-based hydrogel was developed from the invasive aquatic plant Typha angustifolia, utilizing plant-derived cellulose as a robust matrix and plant extract as a reducing agent for CuO nanoparticle synthesis, resulting in a green nanocomposite hydrogel (CuO–CNCH). The nanocomposite was synthesized via an environmentally friendly method, and comprehensive characterization using FTIR, XRD, SEM, EDX, TEM, and XPS confirmed successful crosslinking, uniform embedding of CuO nanoparticles, and homogeneous structural integrity, while XPS analysis verified the + 2 oxidation state of Cu and surface composition of CuO NPs in CuO–CNCH. SEM and TEM analyses revealed a well dispersed nanoparticle distribution within the hydrogel pores. Thermal analysis (TGA/DTG) demonstrated enhanced thermal stability of CuO–CNCH upto 280 °C compared to pure cellulose hydrogel, indicating suitability for high temperature applications and potential industrial use. The catalytic performance of CuO–CNCH was evaluated for the degradation of four synthetic dyes Rhodamine B (RhB), Crystal Violet (CV), Chicago Blue (CB), and Methyl Orange (MO) under visible light in the presence of sodium borohydride (NaBH₄). Using catalyst doses of 1.85–2.75 gm and optimized NaBH₄ concentrations, the hydrogel achieved exceptionally high degradation efficiencies of 95.12 ± 1.8% (RhB), 93.60 ± 2.0% (CV), 96.02 ± 1.9% (CB), and 90.80 ± 2.2% (MO). The CuO–CNCH achieved remarkable turnover numbers (TON) up to 30.54 and rate constants (k) ranging from 0.0865 to 0.1808 min⁻¹, with the catalyst maintaining its activity over six consecutive cycles, demonstrating excellent stability and recyclability. LC–MS and TOC analyses confirmed complete mineralization and reduced ecotoxicity of dyes, demonstrating that the CuO–CNCH derived from invasive plant biomass is a thermally stable, eco-friendly, and highly effective catalyst for sustainable industrial wastewater remediation.

Graphical abstract

We report on the rheological and mechanical properties of bio-sourced composites composed of dispersed cellulose nanofibers (CNFs) in polylactic acid (PLA). The composites were generated using a liquid CO₂ (L-CO₂) solvent exchange/supercritical CO₂ (SC-CO₂) venting procedure. This SC-CO₂ dewatering process maintained the nano-dimensional architecture of the CNFs and led to a homogeneous distribution of CNFs within the PLA matrix. Rheological data obtained for the SC-CO₂ dewatered composite at 2, 5, 10, and 20 wt% CNFs showed network formation of the CNF within the PLA matrix. At 10 wt% SC-CO₂ CNF concentration, we obtained a 23% increase in tensile modulus and a 6% increase in tensile strength relative to neat PLA. These results are comparable to the literature values of 30% and 9% increases in tensile modulus and strength obtained using the solvent casting method with chloroform. In contrast, PLA composites containing spray dried CNFs (SDCNFs) showed no difference in tensile modulus or strength compared to neat PLA.

Fibrillated cellulose, such as micro- and nanofibrillated cellulose (MNFC) and fines, plays a significant role in papermaking. However, characterizing its complex morphology across multiple scales remains challenging due to the limitations of conventional microscopy. Optical microscopy lacks the resolution to detect nanoscale fibrils, and electron and atomic force microscopy are limited by the trade-off between resolution and field of view. To overcome these limitations, we employed large-area transmission electron microscopic (TEM) imaging. The automatic stitching of thousands of images generated a single image as large as 523 × 886 µm², enabling the visualization of both fibril length and width across multiple scales, from micrometers to nanometers. Moreover, large-area TEM imaging revealed distinct morphological differences between two samples that have previously been considered comparable by a standard optical method: one, slender and fibrillar, prepared by the aqueous counter collision method; the other, sheet-like with a broader size distribution, prepared by a grinder.

In this work, we propose an X-ray diffraction characterization of the flax ultrastructure to improve our understanding of its role in expressing the complex mechanical behaviour of flax fibres. Initially, X-ray diffraction measurements were performed on both undeformed and deformed samples consisting in fibre bundles and using for the first time, the combined “structure/microstructure/texture” analysis method implemented in the Maud software and based on a Rietveld algorithm. For all the fibre bundles, the microstructural analysis showed that these microfibrils, having a cellulose Iβ structure, exhibit an ellipsoidal crystallite shape elongated along their c-axis. The results also suggest the existence of a paracrystalline cellulose phase in the flax ultrastructure, with a degree of order intermediate between amorphous and crystalline Iβ cellulose. The corresponding quantitative texture analysis allowed to access the microfibril angle distribution in the flax secondary wall, with cellulose microfibrils inclined with respect to fibre axes with angles in the 0–20° range and a maximum of the distribution around 5°–10°. The combination of tensile tests and in-situ X-ray diffraction measurements put in evidence a substantial rearrangement of the microfibril angle distribution confirming the reorientation of cellulose microfibrils along the fibre axis. However, this evolution is non-linear and appears significant for deformations below 0.6%, becoming relatively weak or attenuated for higher deformations. This X-ray combined analysis provides new insights into the organization of cellulose in flax fibres, and by extension, plant fibres in general.