Fabricating lignin-containing cellulose nanofibrils with unique properties from agricultural residues with assistance of deep eutectic solvents

Multifunctional composite film of curcumin Pickering emulsion stabilized by lignocellulose nanofibrils isolated from bamboo shoot shells for monitoring shrimp freshness

Concerns about food safety and environmental impact from chemical surfactants have prompted interest in natural lignocellulosic materials as alternatives. In this study, we combined hydrated deep eutectic solvent (DES) pretreatment with ultrasound treatment to prepare lignocellulosic nanofibrils (LCNF) from bamboo shoot shells with appropriate surface properties for stabilizing Pickering emulsions. The pretreatment intensity effectively modulated the surface characteristics of LCNF, achieving desirable wettability through lignin retention and in-situ esterification. The resulting LCNF/curcumin Pickering emulsion (CPE) demonstrated curcumin protection and pH-responsive color changes, while the ensuing CPE/PVA composite film exhibited ultraviolet shielding, mechanical strength, oxygen barrier, and antioxidant properties. Furthermore, the CPE/PVA film showed promise as a real-time indicator for monitoring shrimp freshness, maintaining sensitivity to spoilage even after six months of storage. These findings advance the advancement of green LCNF technologies, providing eco-friendly solutions for valorizing bamboo shoot shells and enhancing the application of LCNF in Pickering emulsions.

Recent advance on lignin-containing nanocelluloses: The key role of lignin

Nanocelluloses (NCs) isolated from lignocellulosic resources usually require harsh chemical pretreatments to remove lignin, which face constraints such as high energy consumption and inefficient resource utilization. An alternative strategy involving the partial retention of lignin can be adopted to endow NCs with better versatility and functionality. The resulting lignin-containing nanocelluloses (LNCs) generally possess better mechanical property, thermal stability, barrier property, antioxidant activity, and surface hydrophobicity than lignin-free NCs, which have attracted extensive interest as a promising green nanomaterial for numerous applications. This review provides a comprehensive overview of the recent advances in the preparation, properties, and food application of LNCs. The effect of residual lignin on the preparation and properties of LNCs is discussed. Furthermore, the key roles of lignin in the properties of LNCs, including particle size, crystalline structure, dispersibility, thermal, mechanical, antibacterial, rheological and adhesion properties, are summarized comprehensively. Furthermore, capitalizing on their dietary fiber and nanostructure properties, the food applications of LNCs in the forms of films, gels and emulsions are also discussed. Finally, the challenges and opportunities regarding the development of LNCs are provided.

Lignocellulosic biomass-derived functional nanocellulose for food-related applications: A review

In recent years, nanocellulose (NC) has gained significant attention due to its remarkable properties, such as adjustable surface chemistry, extraordinary biological properties, low toxicity and low density. This review summarizes the preparation of NC derived from lignocellulosic biomass (LCB), including cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), and lignin-containing cellulose nanofibrils (LCNF). It focuses on examining the impact of non-cellulosic components such as lignin and hemicellulose on the functionality of NC. Additionally, various surface modification strategies of NC were discussed, including esterification, etherification and silylation. The review also emphasizes the progress of NC application in areas such as Pickering emulsions, food packaging materials, food additives, and hydrogels. Finally, the prospects for producing NC from LCB and its application in food-related fields are examined. This work aims to demonstrate the effective benefits of preparing NC from lignocellulosic biomass and its potential application in the food industry.

Pickering emulsions stabilized by cellulose nanofibers with tunable surface properties for thermal energy storage

Cellulose nanofibers (CNFs) have been widely used as a renewable emulsifier to stabilize two immiscible liquids due to their intrinsic amphiphilicity and excellent emulsifying ability. However, it remains challenging to fully understand the effects of carboxylate group content and surface charge density on the emulsifying ability of CNFs and the stability of Pickering emulsion. Herein, carboxymethylated CNFs were extracted from bleached kraft pulp using etherification reaction and high-pressure homogenization, allowing for easy surface charge density and size adjustment by changing sodium chloroacetate content and homogenization cycles. The optimizing CNFs possessed a high Zeta potential (-71.2 mV) and a suitable carboxylate group content (1.81 mmol/g), which enabled CNFs to irreversibly adsorb at the hydrophobic paraffin wax (PW) droplet surface and form interfacial steric barriers, providing large electrostatic repulsion between the PW droplets against coalescence. Thus, the CNF-stabilized PW emulsions could be stored for more than 6 months. Moreover, the phase change enthalpy of the freeze-dried emulsion is as high as 193.7 J/g, which provides the emulsion to reversibly store and release heat. This work provides a comprehensive insight into the interfacial stability mechanism of CNFs as stabilizers and facilitates the potential application in thermal energy storage.

Fabrication of lignocellulose/liquid metal-based conductive eutectic hydrogel composite for strain sensors

High conductive and freeze-resistant hydrogels with adhesion function are ideal candidates for soft electronic devices. However, it remains a challenge to design appropriate conductive nanofillers to endow hydrogels with all these characteristics. Liquid metal (LM) exhibits exceptional electrical conductivity and convenient processability, rendering it a highly promising contender. Cellulose nanofibrils (CNFs) were employed as the interfacial stabilizer in synthesizing stable CNFs encapsulated LM solutions. Then the lignin was further coated on the surface of CNFs-LM (LCL) to prepare lignin-coated hybrid hydrogels. The obtained LCL displayed outstanding water-dispersible stability and were promising conductive nanofillers for hydrogels. During the fabrication of poly N-(hydroxymethyl) acrylamide (PHA) hydrogels, the LM was dispersed into LM particles with smaller sizes, leading to highly conductive LCL-PHA hydrogels (0.38 S·m-1). The prepared LCL-PHA hydrogels exhibited exceptional mechanical properties, including a strain at a break of 134.6 %, stress at a break of 22.7 Kpa, and a toughness of 16.3 KJ·m-3. Additionally, the LCL-PHA hydrogels demonstrated favorable electrical conductivity and adhesion. Notably, even after being subjected to freezing at -20 °C for 24 h, they remained suitable for effective real-time monitoring of all types of human activities, demonstrating superior environmental stability.

Equilibrium Moisture Mediated Esterification Reaction to Achieve Over 100% Lignocellulosic Nanofibrils Yield

Lignocellulosic nanofibrils (LCNFs) isolation is recognized as an efficient strategy for maximizing biomass utilization. Nevertheless, achieving a 100% yield presents a formidable challenge. Here, an esterification strategy mediated by the equilibrium moisture in biomass is proposed for LCNFs preparation without the use of catalysts, resulting in a yield exceeding 100%. Different from anhydrous chemical thermomechanical pulp (CTMP0%), the presence of moisture (moisture content of 7 wt%, denoted as CTMP7%) introduces a notably distinct process for the pretreatment of CTMP, comprising the initial disintegration and the post-esterification steps. The maleic acid, generated through maleic anhydride (MA) hydrolysis, degrades the recalcitrant lignin-carbohydrate complex (LCC) structures, resulting in esterified CTMP7% (E-CTMP7%). The highly grafted esters compensate for the mass loss resulting from the partial removal of hydrolyzed lignin and hemicellulose, ensuring a high yield. Following microfluidization, favorable LCNF7% with a high yield (114.4 ± 3.0%) and a high charge content (1.74 ± 0.09 mmol g-1) can be easily produced, surpassing most previous records for LCNFs. Additionally, LCNF7% presented highly processability for filaments, films, and 3D honeycomb structures preparation. These findings provide valuable insights and guidance for achieving a high yield in the isolation of LCNFs from biomass through the mediation of equilibrium moisture.

Green and efficient synthesis of cellulose nanocrystals from Hamelia patens leftover via hydrolysis of microwave assisted-ionic liquid (MWAIL) pretreated microcrystalline cellulose

The efficient bioconversion of the lignocellulosic agro-waste has immense importance in biorefinery processing in extracting the cellulose and saccharide fractions. To achieve this, a series of chemical pretreatments is employed, thus concerning environmental threats limit its use. Therefore, an ionic liquid is employed for pretreatment before sustainable extractions owing to its safe manipulation, recycling, and reusability. Specifically, microwave-assisted ionic liquid (MWAIL) pretreatment has significant importance in extracting high cellulose yield at less thermal power consumption. In this study, the leftover stalks of Hamelia patens were subjected to MWAIL pretreatment at 60, 70, 80, and 90 °C to extract microcrystalline cellulose (MCC). Subsequently, the MCC was fabricated into cellulose nanocrystals (CNC) through hydrolytic treatment using acidic and ionic liquids and denoted as CNC-AH and CNC-ILH. Thus obtained CNC was characterized by FTIR, FESEM, XRD, and TGA to investigate the influence of solvent on its morphology, crystallinity, and thermal stability of CNC. The results support that the CNC-ILH has comparatively more thermal and dispersal stability with a reduced crystallinity index than CNC-AH. The surprising results of CNC-ILH signify its utilization in diverse applications in the food and industrial sectors.

Extraction of lignin-containing nanocellulose fibrils from date palm waste using a green solvent

Lignin-containing nanocellulose (LNC) is a compelling alternative to traditional nanocellulose (NC), it offers enhanced yields and a reduction in the demand for toxic chemicals. This research involves the isolation of LNC from date palm waste using a green hydrolysis process and its subsequent characterization. The potential of using ionic liquids (ILs) as green solvents to isolate LNC has not yet been explored. Our findings suggest that 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) can hydrolyze partially delignified and unbleached lignocellulose, achieving LNC synthesis. The obtained LNC showed a higher yield than its NC counterpart and exhibited rod-shaped fibers with nanoscale diameters and micrometer lengths, indicating a high aspect ratio. Dynamic Light Scattering (DLS) results indicate average particle sizes of 143.20 nm for NC and 282.30 nm for LNC, with a narrow particle size distribution conforming their monodisperse behavior. Thermogravimetric analysis and differential scanning calorimetry revealed high thermal stability (initial degradation temperature = 222.50 °C and glass transition temperature = 84.45°C) of LNC. Moreover, the obtained LNC fibers were crystalline (crystallinity index = 52.76 %). Their activation energy (124.95 kJ/mol) was determined using the Coats-Redfern method by employing eight solid-state diffusion models. Overall, this study motivates the use of ILs as green solvents to produce lignocellulose derivatives that are suitable for various applications.

Carboxyl-modified nanocellulose (cNC) enhances the stability of cNC/pullulan bio-nanocomposite hard capsule against moisture variation

The quality of polysaccharide-based films and hard capsules is often affected by changes in relative humidity, manifesting as unstable water content, and changes in mechanical strength that make them brittle or soft. Herein, carboxyl-modified nanocellulose (cNC) was prepared and used as a new component to successfully improve the moisture resistance of cNC/pullulan/high-acyl gellan bio-nanocomposite hard capsules (NCPGs). Homogenously dispersed cNC in the pullulan/high-acyl gellan matrix could render the formation of more hydrogen bonds that provided additional water-binding sites and limited the free movement of pullulan and high-acyl gellan molecular chains within NCPGs. This contributed to a decreased amount of pooling adsorption water and an increased amount of Langmuir adsorption water in NCPGs, as compared to pullulan/high-acyl gellan hard capsules (PGs) without cNC. Therefore, the equilibrium moisture content (EMC) values of NCPGs decreased at 83 % relative humidity and increased at 23 % relative humidity compared to those of PGs. Together with enhanced mechanical and barrier properties, NCPGs effectively protected encapsulated amoxicillin and probiotic powder from changes in the outside humidity. Additionally, NCPGs exhibited faster drug release. This study presents a new mechanism and strategy for fabricating films and hard capsules with enhanced stability against moisture variation.

Microwave-assisted DES fabrication of lignin-containing cellulose nanofibrils and its derived composite conductive hydrogel

Deep eutectic solvents (DES) have been regarded as green solvents in the biorefinery of lignocellulosic biomass, but long duration time has severely limited efficiency. The microwave-assisted DES pretreatment along with enzymatic hydrolysis and high-pressure homogenization process was proposed to produce lignin-containing cellulose nanofibrils (LCNF) from corncob. Benefiting from microwave-assisted DES pretreatment, the duration time was greatly shortened; meanwhile the effects of different kinds of DES on the resultant LCNF were investigated. The results showed that, the microwave-assisted DES fabricated LCNF (M-LCNF) was successfully obtained, exhibiting good nano size, thermal stability, colloidal stability, and fluorescence. M-LCNF was further introduced into phytic acid (PA) enhanced poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) network and constructed composite conductive hydrogels (PLP). The obtained hydrogels exhibited good mechanical strength, UV blocking ability, fluorescence, and conductivity. A simple battery assembled with the resultant PLP as electrolyte had an out voltage of 2.41 V. The composite conductive hydrogel showed good sensing performance towards different stimuli (e.g., stretching and compression) and human motions in real time. It is expected that this research would provide an alternative way for green fabrication of LCNF and potential application of LCNF in flexible sensors.

Cellulose nanofibers produced from spaghetti squash peel by deep eutectic solvents and ultrasonication

In this study, the cellulose nanofibers (CNFs) derived from spaghetti squash peel (SSP) were prepared using a novel approach involving deep eutectic solvent (DES) pretreatment coupled with ultrasonication. Molecular dynamics (MD) simulations revealed that the number of hydrogen bonds influences the viscosity and density of DES systems, and experimental viscosity (ηexp) confirmed consistency with the computed viscosity (ηMD) trends. After DES pretreatment and ultrasonication, the cellulose content of ChCl/oxalic acid (ChCl/OA) CNF (35.63%) and ChCl/formic acid (ChCl/FA) (32.46%) is higher than ChCl/Urea CNF (28.27%). The widths of ChCl/OA CNF, ChCl/FA CNF, and ChCl/Urea CNF were 19.83, 11.34, and 18.27 nm, respectively, showing a network-like fiber distribution. Compared with SSP (29.76%) and non-ultrasonic samples, the crystallinity index of ChCl/OA CNF, ChCl/FA CNF, and ChCl/Urea CNF was improved by ultrasonication. The thermal decomposition residue of ChCl/OA CNF (25.54%), ChCl/FA CNF (18.54%), and ChCl/Urea CNF (23.62%) was lower than that of SSP (29.57%). These results demonstrate that CNFs can be prepared from SSP via DES pretreatment combined with ultrasonication. The lowest viscosity observed in the formic acid DES group (ηexp of 18 mPa·s), the ChCl/FA CNF exhibits excellent stability (Zeta potential of -37.6 mV), which can provide a promising prospect for utilization in biomass by-products and applications in the materials field.

Versatile Mesoporous All-Wood Sponge Enabled by In Situ Fibrillation toward Indoor-Outdoor Energy Management and Conversion

The on-demand regulation of cell wall microstructures is crucial for developing wood as a functional building material for energy management and conversion. Here, a novel strategy based on reactive deep eutectic solvent is developed to one-step in situ fibrillate wood via disrupting the hydrogen bonding networks in cell walls and simultaneously carboxylating wood components, without significantly altering the native hierarchical structures of wood. Benefiting from its distinctive cell wall structure composed of individualized yet well-organized lignocellulose nanofibrils, in situ fibrillated wood exhibits a prominent mesoporous structure with a specific surface area of 81 m2/g. It represents a robust sponge material (5 MPa at 80% strain) with excellent durability. Due to the enhanced compressibility and charge polarization capacity, the in situ fibrillated wood (10 × 11 × 12 mm3) can generate a piezoelectric output voltage of up to 2 V under 221 kPa stress. The favorable microstructural characteristics render in situ fibrillated wood with highly thermal-insulating properties, high solar reflectivity, and mid-infrared emissivity, favoring outdoor passive cooling effects with a subambient temperature drop of 6 °C. Combining its controllable, durable, and eco-friendly attributes, our developed wood sponge represents a versatile structural material suitable for indoor/outdoor energy-saving applications.

Upgrading lignin macromolecular by green and recyclable ternary deep eutectic solvents

Lignin is the most abundant natural aromatic macromolecule in the nature, but its high value-added utilization has been seriously hindered by the highly random and branched structures and the high difficulty in separation and purification. A microwave-assisted ternary deep eutectic solvent (DES) composed by formic acid, lactic acid and choline chloride was developed for lignin pretreatment. The effects of three types of DES on main characteristics of lignin were investigated, and the corresponding dissolution mechanism was proposed. The results showed that, the microwave-assisted ternary DES pretreatment showed an obvious improvement on main characteristics of regenerated lignin, e.g., a higher purity, lower molecular weight with reduced dispersity, improved thermal stability, higher phenolic hydroxyl content, and increased antioxidative activity in comparison with control. It is expected that the lignin macromolecular can be facile regulated and upgraded by the proposed ternary DES.

Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction of cellulose from Urtica dioica: A benign to green approach

The extraction of cellulose using eco-friendly solvents has been gaining significant attention for a couple of decades. This study investigated the impact of benign and green solvents on the extraction, thermal stability, mechanical properties, and crystallinity of cellulose extracted from Urtica dioica (Stinging nettle) using a Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction technique. In this regard, the stalks were undergone through pre chemical treatment before starting bleaching them with hydrogen peroxide (HPO) and 1-butyl-3-methylimidazolium acetate (BMIM-Ac) having different mole ratios (5, 7.5, and 10) to expose cellulose. The Urtica dioica cellulose (UDC) was characterized using FTIR, tensile testing, FESEM, XRD, and TGA. The fibrillation and lumen can be seen in SEM images that confirm the extraction of cellulose. The results showed that the BMIM-Ac-10 gives the maximum cellulose yield (88 %) than other compositions. Moreover, the cellulose extracted using BMIM-Ac-10 has high mechanical strength which makes it a potential constituent for various applications in the field of materials science. These results have significant implications for the development of sustainable and efficient processes for the extraction of cellulose.

Valorizing spent mushroom substrate into syngas by the thermo-chemical process

This study investigated the conversion of agricultural biomass waste (specifically, spent mushroom substrate) into syngas via pyrolysis. Carbon dioxide was used to provide a green/sustainable feature in the pyrolysis process. All the experimental data highlight the mechanistic role of carbon dioxide (CO2) in the process, demonstrated by the enhanced carbon monoxide (CO) yield from pyrolysis under CO2. Carbon dioxide was indeed reactive at ≥ 500 ˚C. Carbon dioxide was reduced and subsequently oxidized volatiles stemming from the thermolysis of spent mushroom substrate via the gas-phase reaction, thereby resulting in the enhanced formation of CO. Carbon dioxide radically diverted the carbon distribution patterns of the pyrogenic products, as more carbon in the oil was allocated to syngas by the gas-phase reaction of volatiles and CO2. To enhance the mechanistic role of CO2, a Ni-based catalyst was added to the pyrolysis process, which greatly accelerated the gas-phase reaction of volatiles and CO2.

Fabrication of versatile lignocellulose nanofibril/polymerizable deep eutectic solvent hydrogels with anti-swelling, adhesive and low-temperature resistant properties via a one-pot strategy

Lignocellulosic nanofibril (LCNF) is indispensable in numerous potential applications because of its unsurpassed quintessential characteristics. While it still remains a challenge to assemble LCNF in a facile and environmental economy-first manner. In this work, a simple and green one-step synthetic approach was reported to prepare a series of LCNF-containing versatile hydrogels using deep eutectic solvent (DES). In particular, the LCNF5% hydrogel (namely LCNF5%-gel) in this work perfectly integrated superior stretchability (∼643 %), and displayed a dramatically improved anti-swelling ability (25 %) compared to the control sample (neat DES hydrogel, 2252 %). Simultaneously, the LCNF5% hydrogel presented underwater adhesiveness and outstanding long-term low-temperature resistance (stable at -25 °C for a month). This novel multifunctional hydrogel, prepared by a facile and eco-friendly strategy, is potentially useful in wet adhesion or underwater applications.

High-Lignin-Containing Cellulose Nanofibrils from Date Palm Waste Produced by Hydrothermal Treatment in the Presence of Maleic Acid

Lignin-containing cellulose nanofibrils (LCNFs) have attracted great attention because the presence of lignin brought additional merits to cellulose nanofibrils including hydrophobicity, ultraviolet (UV)-shielding capacity, and reduced water sensitivity. In the present work, LCNFs with lignin content up to 21 wt % were prepared with a high yield exceeding 70 wt %, from neat date palm waste, by a hydrothermal treatment (HTT) at 120-150 °C in the presence of 20-30 wt % maleic acid, followed by high-pressure homogenization. The chemical composition, degree of polymerization, morphology, and colloidal and rheological properties of the LCNFs were investigated to understand how the HTT in the presence of MA affected the properties of the resulting LCNFs. Nanopapers prepared from the LCNF suspensions exhibited mechanical properties lower than those from lignin-free CNF-based nanopapers, yet with decreased hydrophilicity. A mechanism explaining how the HTT in the presence of MA facilitated the disintegration of the biomass into nanoscale material was proposed. Overall, the present work demonstrated a feasible and scalable approach for the sustainable production of LCNF suspensions from neat agricultural residues, with a high yield and a high lignin content, without any need to perform a preliminary partial delignification.

Theoretical study of lactic acid-based deep eutectic solvents dissociation of hemicellulose with different hydrogen bonding acceptors

This paper explored the mechanism of dissociation of hemicellulose using lactic acid (LA)-based deep eutectic solvents (DESs) synthesized with different hydrogen bond acceptors (HBAs) via simulations. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations revealed that DESs synthesized with guanidine hydrochloride (GuHCl) as hydrogen bond acceptor (HBA) demonstrated better hemicellulose solubilization compared to the conventional DESs synthesized using choline chloride (ChCl) as HBA. The best interaction with hemicellulose was achieved at GuHCl:LA = 1:1. The results showed that CL^- played a dominant role in the dissolution of hemicellulose by DESs. Unlike ChCl, the guanidine group in GuHCl had the delocalized π bond, which made CL^- have stronger coordination ability and promoted dissolution of hemicellulose by DESs. Moreover, multivariable analysis was employed to establish the correlation between the effects of different DESs on hemicellulose and the molecular simulation results. Additionally, the influence of different HBAs functional groups and carbon chain length on the solubilization of hemicellulose by DESs were analyzed.

Production of nanocellulose using acidic deep eutectic solvents based on choline chloride and carboxylic acids: A review

Nowadays, nanocellulose production processes with numerous merits of green, eco-friendly, and cost-effective are in urgent need. Acidic deep eutectic solvent (ADES), as an emerging green solvent, has been widely applied in the preparation of nanocellulose over the past few years, owing to its unique advantages, including non-toxicity, low cost, easy synthesis, recyclability, and biodegradability. At present, several studies have explored the effectiveness of ADESs in nanocellulose production, particularly those based on choline chloride (ChCl) and carboxylic acids. Various acidic deep eutectic solvents have been employed, with representative ones such as ChCl-oxalic/lactic/formic/acetic/citric/maleic/levulinic/tartaric acid. Herein, we comprehensively reviewed the latest progress of these ADESs, focusing on the treatment procedures and key superiorities. In addition, the challenges and outlooks of ChCl/carboxylic acids-based DESs implementation in the fabrication of nanocellulose were discussed. Finally, some suggestions were proposed to advance the industrialization of nanocellulose, which would help for the roadmap of sustainable and large-scale production of nanocellulose.

Supramolecular structure of microwave treated bamboo for production of lignin-containing nanocellulose by oxalic acid dihydrate

Supramolecular structure of cellulosic materials from microwave treatment were throughly investigated for production of lignin-containing nanocellulose. The results revealed that both the intermolecular and intramolecular hydrogen bonds were altered by microwave irradiation. Cellulose I_β was the main component in microwave treated bamboo (MTB) with smaller interplanar spacing, and the cellulose molecules were loosely connected resulting in a loose structure. Thereafter, MTB was used to produce lignin-containing nanocellulose by using oxalic acid dihydrate (OAD) to test the feasibility on its efficiency. The chemical consumed for the preparation of lignin-containing nanocellulose (LCN) with a comparable yield (68.08-82.33 %) from MTB was merely 1/10 that from conventional cellulosic materials, indicating the supramolecular structural changes of bamboo cellulose induced by microwave treatment provided suitable conditions for the subsequent hydrolysis of OAD to prepare LCN. The LCN was further added into the polyvinyl alcohol (PVA) matrix endowed excellent UV shielding property and thermal stability for the PVA/LCN films. This study was aimed to provide an environmentally friendly method on the production and application of LCN from bamboo by employing microwave treatment from the perspective of supramolecular level.

Ultra-Thin Wood-Based Acoustic Diaphragms Fabricated via an Environmentally Friendly Strategy

An acoustic diaphragm is a crucial component that regulates sound quality in earphones and loudspeakers. Natural wood with inherent good acoustic resonance and vibration spectrum is widely used in sound devices. However, using natural wood to produce an acoustic diaphragm is still a big challenge because making ultra-thin wood is hard and it warps easily. Therefore, this study introduces a new method for preparing ultra-thin wood acoustic diaphragms less than 10 μm in thickness, relying on delignification, sulfonation, and densifying techniques. The innovative sulfonation process increased the intermolecular hydrogen bond force, which significantly improved the tensile strength and Young's modulus of the wood diaphragm, up to 195 MPa and 27.1 GPa, respectively. Compared with the commonly used diaphragms in the market, this wood diaphragm exhibits an excellent specific dynamic elastic modulus up to 95.1 GPa/g cm³, indicating better acoustic properties. Also, the resonance frequency was up to 1240 Hz, 4.5 times higher than the titanium diaphragm among high-end products. Besides, the drying shrinkage rate of the ultra-thin wood diaphragm is only 1.2%, indicating excellent dimensional stability. This high-quality wood acoustic diaphragm has a very high application prospect and outstanding attributes for promoting the development of acoustic devices. Moreover, the reaction reagent can be recycled after preparation, and the selected reagents are green and environmentally friendly.

Deep eutectic solvents as promising pretreatment agents for sustainable lignocellulosic biorefineries: A review

Increasing reliance on non-renewable fuels has shifted research attention to environmentally friendly and sustainable energy sources.The inherently recalcitrant nature of lignocellulosic biomass (LCB) makes downstream processing of the bioprocess challenging. Deep eutectic solvents (DESs) are popular and inexpensive green liquids found effective for LCB valorisation. DESs have negligible vapor-pressure and are non-flammable, recyclable, cost-economic, and thermochemically stable. This review provides a detailed overview on the DESs types, properties and their role in effective delignification and enzymatic digestibility of polysaccharides for cost-effective conversion of LCB into biofuels and bioproducts. The conglomeration of DESs with assistive pretreatment techniques can augment the process of biomass deconstruction. The current challenges in upscaling the DESs-based pretreatment technology up to commercial scale is summarized, with possible solutions and future directions. These insights would fill the knowledge-gaps to towards development of lignocellulosic biorefineries and to address the global energy crisis and environment issues.

Efficient removal of residual lignin from eucalyptus pulp via high-concentration chlorine dioxide treatment and its effect on the properties of residual solids

In fact, effectively removing lignin from pulp fibers facilitates the conversion and utilization of cellulose. In this study, the residual lignin in eucalyptus pulp was separated using a high concentration of chlorine dioxide. The effects of chlorine dioxide dosage, temperature, and time on lignin removal were investigated. The optimal conditions are chlorine dioxide dosage 5.0%, reaction temperature 40 °C, and reaction time 30 min. The lignin removal yield is 88.21%. The removal yields of cellulose and hemicellulose are 2.28 and 17.00%, respectively. The treated eucalyptus pulp has higher fiber crystallinity and thermal stability. The carbon content on the fiber surface is significantly reduced. The results show that lignin is removed by efficient oxidation, and the degradation of carbohydrates is inhibited using high concentrations of chlorine dioxide at low temperatures and short reaction times. This provides theoretical support for high value conversion of cellulose.

The role of deep eutectic solvents in the production of cellulose nanomaterials from biomass

In recent years, the demand for environment-friendly products has been on an increasing trend among researchers and industry for sustainable development. Deep eutectic solvents are green solvents which, due to their properties (biodegradability, recyclability, low cost, availability, easy preparation, low toxicity, chemical and thermal stability), can be used in various fields such as polymer chemistry, which includes nanocellulose isolation and polysaccharides processing. Several studies have illustrated the effectiveness of using deep eutectic solvents instead of the conventional reaction system to produce and disperse nanomaterials. This work summarizes the use of deep eutectic solvents in the isolation of cellulosic nanomaterials from different types of biomass. Deep eutectic solvents demonstrate high effectiveness in swelling lignocellulosic biomass and producing cellulose nanomaterials. Overall, deep eutectics solvents represent an innovative and effective pretreatment process for the fractionation of raw cellulose-containing fibres to promote subsequent isolation of nanomaterials made from cellulose.