Cellulose最新文献

This study investigated the dissolution of hemp yarns in the ionic liquid 1-ethyl-3-methylimidazolium acetate. The yarns were submerged in the ionic liquid at various temperatures and times, then coagulated in water. This resulted in the formation of a composite yarn where two optical microscopy methods were employed to track the growth of the coagulated matrix. In the first, the submerged yarns within water were measured from a side view. In the second, the yarns were dried then analysed by encapsulating in epoxy resin. In both methods, the growth of the swollen ring thickness and the coagulated fraction was tracked as a function of time and temperature. It was found to obey time-temperature superposition, giving a dissolution activation energy of (78pm 2 text{k};text{J}/text{m}text{o}text{l}). In water the yarn is swollen; the swelling ratios of the different regions were calculated to be (4.4pm 0.2 ; text{a}text{n}text{d} ; 1.4pm 0.1) for the outer dissolved ring and the undissolved core, respectively. A novel finding in this study was that the growth of the coagulated region follows a diffusion process, increasing with the square root of time, and so could be modelled to give a diffusion coefficient for the ionic liquid of (6.74times {10}^{-13};{text{ m}}^{2}/{text{s}}). This compared well with previously published NMR data for a saturated cellulose solution (23.5%). This strongly suggests that the diffusion of the ions through a saturated layer of cellulose solution controls the dissolution of the yarn. This finding has significant implications for cellulose-based composite production and thus the recycling of cellulose textiles.

In this study, we perform a comprehensive examination of the ultrasonic dewatering of cellulose nanofibril (CNF) suspensions, with particular emphasis on the role of fines content. The production of CNFs involves mechanical fibrillation which leads to the presence of different percentages of fines (fibrils under 200 μm) in the final product. Although fines have demonstrated mechanical advantages in composite materials, they also increase water retention by the fibrils, leading to increased dewatering time and energy. We selected two distinct CNF samples with 60% and 90% fines, respectively, and subjected them to ultrasonic drying until 100 wt% CNFs is reached. We found that the 90% fines samples displayed 20% longer drying times, indicating a higher water retention capacity than the 60% fines samples due to increased hydrogen bonding sites. Both fines types exhibit a biphasic pattern in water removal, with the second phase, commencing upon the elimination of half the water, displaying similar rates regardless of the fines content. As dewatering and drying processes often induce agglomeration in CNFs, we systematically dewatered both the suspensions until concentrations of 15, 25, and 35% were achieved and then redispersed to 0.01 wt% CNF. To evaluate the stability of redispersed samples, we monitored their settling behavior and conducted UV–vis transmittance analyses. Results showed that while 60% fines samples could be redispersed in 1 min, the 90% fines samples required up to 5 min to reach a similar level of stability to their original suspensions. Notably, UV–vis transmittance values remained consistent across both the 60% and 90% fines samples and their initial suspensions, indicating a lack of significant agglomeration following redispersion. These findings provide critical insights regarding the impact of fines percentages in CNFs on dewatering duration and suspension stability during ultrasonic dewatering, contributing to improved processing strategies in industrial cellulose applications.

Enzymatic deconstruction of cellulose was dramatically changed by the discovery of Lytic Polysaccharide Monooxygenases (LPMOs). These revolutionizing enzymes are copper-dependent, and through an oxidative process, break the cellulose chain, facilitating deconstruction by cellulases. The LPMO catalytic copper can be reduced by an assortment of molecules, including lignin degradation products and other enzymes. Here we show that Thermothelomyces thermophilus LPMO9H (TtLPMO9H) had activity towards cellulosic substrate, when both an aryl-alcohol oxidase, TtAAOx, and its substrate, veratryl alcohol are present. We found that veratryl alcohol by itself could not drive the LPMO activity, but when combined with TtAAOx, the LPMO was fueled. Formation and release of oxidized oligosaccharides by TtLPMO9H required the presence of methoxylated benzyl alcohols and either TtAAOx for in situ production, or an exogenous supply of H₂O₂. Additionally, we showed that this in situ production of H₂O₂ resulted in slower LPMO reactions as compared to standard LPMO catalysis driven by ascorbic acid but circumvented early inactivation of the LPMO. These results suggest that many oxidoreductases, including oxidases associated with lignin degradation, can serve in LPMO reactions as in situ H₂O₂ generators.

Metal–organic frameworks (MOFs) have received widespread attention in recent years. However, the powder form of MOFs limits their large-scale applications. To facilitate the application of MOFs, mass production and shaped manufacturing of MOFs is significantly effective. Herein, a generic method based on a simple polymerization technique is proposed to prepare highly porous MOF–cellulose composite beads and the application of these composite beads in dye removal and recovery is displayed. Non-toxic solvent water and biodegradable sodium carboxymethylcellulose (CMC) were used as raw materials in the synthesis method. In addition to maintaining the crystallinity and porosity of the MOFs embedded in the cellulose matrix, the unique three-dimensional lamellar interconnected structure provides good mechanical properties for the composite beads. To demonstrate the practicality of these composite beads, a recycling processing system was built as a proof-of-concept device. MIL-100/CMC-HD can effectively degrade more than 95% of the dye and can be recycled multiple times. The superiority of the MOF–cellulose composite beads is highlighted by their ease of recycling and storage compared to MOF powder.

Graphical abstract

MOF/carboxymethylcellulose porous composite beads are synthesized in a simple one-step process. The lamellar interconnected structure not only facilitates the diffusion of contaminants in water but also provides good mechanical properties.

A flame retardant hexachlorocyclotriphosphazene (HCCP) diethylenetriamine ammonium phosphoric acid and phosphoric acid ester (HPDPP) with –N=P–(N)₃–, –P(=O)(OCH₃)₂, and reactive –P(=O)(O⁻NH₄⁺)₂ groups was synthesized for cotton fabrics. The results showed that the cotton fabrics treated with HPDPP had high flame retardance and durability. The vertical flammability test (VFT), thermogravimetric (TG) analysis, thermogravimetric-Fourier infrared spectrometer (TG-FTIR) and cone calorimetry tests showed that cotton fabrics treated with HPDPP had high flame resistance, displaying condensed phase flame retardance mechanism. The Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) implied that HPDPP molecular could enter the inner amorphous space and graft on cotton fibers. The mechanical properties of cotton fabrics treated with HPDPP were well sustained. Moreover, the limiting oxygen index (LOI) of cotton fabrics treated with 40% HPDPP reached 41.3%, and after 50 laundering cycles (LCs), it reached 29.7% according to the AATCC 61-2013 3A washing standard (vigorous washing), which suggested the flame retardance and durability of treated cotton fabrics were improved significantly. And the EDS of washed cotton fabrics showed that the cotton fabrics treated with HPDPP combined the lowest metal ions compared with cotton fabrics treated with flame retardants with only reactive ammonium phosphoric acid group, because of the fact that besides the necessary reactive ammonium phosphoric groups, the phosphoric acid ester groups can not combine Ca²⁺ and Mg²⁺ etc. Thus, introducing –N=P–(N)₃– groups and phosphoric acid ester groups is an efficient method to significantly increase the durability of the treated fabrics.

Graphical abstract

Metal-organic frameworks (MOFs) are among the most appealing porous materials with a wide range of surface chemistry, high pore structure, high specific surface area and various functionalities. They have found extensive use in a variety of industries. The handling and processing of their properties, however, continue to be quite difficult, which limits the use of MOFs. The most plentiful and environmentally friendly biopolymer in the world is cellulose, and by combining cellulose with MOFs, it is possible to create engineered materials with a variety of hitherto unachievable qualities. This is an excellent way to increase the usage of MOFs in functional materials. This review describes the synthesis of cellulose MOFs composites, mainly MOFs and cellulose compounded in aqueous solution, with two synthetic strategies: in-situ and ex-situ synthesis. By completing further post-processing procedures, the aqueous mixture of MOFs and cellulose can be further processed into four different types of composites, including powders, films, aerogels and hydrogels. We also highlight the use of MOF cellulose composites for antibacterial and drug delivery in nanomedicine. The primary present restrictions on MOF cellulose composites are also reviewed, as well as possible future research directions.

Three-dimensional (3D) microstructured biomaterials are favorable in tissue engineering due to their superior guidance to cellular activities. Herein, we developed a 3D microstructured bacterial cellulose (BC) with arranged fibers by controlling Acetobacter xylinum through an electric field (EF) application. The real-time video analysis showed that EF directed the migration of A. xylinum and increased its migration speed with the increased EF. The bacteria quickly changed direction with high motility in response to the switch on/off of the EF. In the long-term electrical stimulation (ES), the growth of A. xylinum was influenced. Likewise, bacterial cells were oriented along the direction of EF while bacteria simultaneously produced nanocellulose, resulting in 3D networks with aligned fibers. The prepared 5 mA-BC hydrogels presented the ordered 3D microstructure with higher fiber alignment, diameter and flexibility than that of NO EF-BC hydrogels. The in vitro biological evaluation demonstrated that the 5 mA-BC hydrogels were biocompatible whereon NIH3T3 cells proliferated along the direction of fiber alignment. These findings demonstrate that ES provides a promising strategy for the natural fabrication of aligned 3D microstructured BC to guide cellular activities for tissue regeneration.

Cellulose aerogels (CA) were widely used in the adsorption field due to high porosity, ultra-light quality, high-proportioned surface area. This article used a 3D La-CA-based adsorbent to improve wastewater eutrophication. Filter paper as cellulose source was applied and lanthanum was doped. Batch adsorption experiments showed that the maximum phosphate adsorption capacity could reach 54.377 mg g⁻¹ (pH = 3.0). At the same time, the leaching of the lanthanum of the adsorbent was negligible, which proves good stability. In particular, the 3D La-CA presented an overall cylindrical monolith and would be easily separated from water compared with the powdery adsorbent. The adsorption performance of La-CA was not significantly affected by the competitive ions (F⁻, SO₄²⁻, Cl⁻, NO₃⁻) and could still maintain 84.8% after 5 cycles. And mechanism analysis suggested that the 3D La-CA had a specific affinity with phosphates, through electrostatic attraction and inner-sphere complexation. In general, these 3D La-doped cellulose aerogels would provide new possibilities for the practical application of adsorbents in phosphate adsorption.

Cellulose cryogels are promising 3D structures for thermal insulation due to their low thermal conductivity and high porosity. However, there is only a few theoretical studies on their heat transfer mechanisms. In this study, we developed a three-dimensional model to investigate the heat transfer mechanism of microfibrillated cellulose cryogels (MFCCs). The accuracy of our model was validated by the high consistency between the experimental and simulation results, with a maximum difference of only 7.8% in thermal conductivity. Based on the numerical simulation method, the temperature distribution, solid phase and gas phase heat transfer inside the MFCCs were calculated. Our findings indicated that the heat flux transferred through the skeleton gradually improved as the MFC concentration increased, while the heat flux transferred through the air almost remained at a constant value. A detailed numerical parametric study was further conducted to explore the influence of porosity and thickness on heat transfer through MFCCs. Our results demonstrated that the heat flux and thermal conductivity of the cryogels had a negative linear correlation with the porosity. In addition, the heat flux through the MFCCs was found to initially decrease significantly with increasing thickness, after which the decreasing trend of the heat flux slowed down.

Recently, great effort has been made towards the preparation of seepage-free composite phase change materials for advanced thermal energy storage (TES) systems. Within this context, in this study, shape stabilized microcrystalline cellulose (MCC)/methyl stearate (MtS)/graphene nanoplatelet (GnP) composites as novel heat storage materials were produced by facile vacuum impregnation method. The effect of GnP on the MtS loading ratio in the composite structure as well as its effect on other properties such as chemical, latent heat, thermal stability, crystalline, morphological and heat storage–release performance were extensively studied. A high MtS loading rate of 65 wt% was achieved in the shape stabilized composite, in which the MCC–GnP hybrid structure was used as the supporting framework. This composite also offered the highest heat storage–release performance with a thermal conductivity value of 0.51 W/mK. The improved thermal conductivity was also confirmed by reductions in melting–freezing times and infrared thermal image capture analysis. DSC results showed that this composite melts at 35.32 °C with a melting enthalpy of 147.97 J/g. The proposed MC/MtS/GnP composite offered high thermal stability as well as excellent cycling stability after 1000 melt–freeze cycles. All test results suggest that the prepared MCC/MtS/GnP composites offer considerable potential for various low-temperature TES applications.