Search

Having the advantages of a higher yield, lower cost and less environmental impact, lignin-containing cellulose nanofibrils (LCNFs) obtained by mechanically fibrillating unbleached pulps have been demonstrated to be a promising alternative to high-purity nanocellulose. In this study, the structural changes after four drying methods containing freeze-drying (FD), oven-drying (OD), centrifugal followed by vacuum-drying (CVD), and evaporation followed by vacuum-drying (EVD), and efficient reuse of LCNFs were extensively explored. It was found that the structural characteristics of LCNFs after drying were maintained by freeze drying with high lignin contents where the aggregation of fibrils was alleviated by lignin. The freeze-dried LCNFs were further redispersed by homogenizer in water, which exhibited excellent dispersion characteristics. In addition, the redispersed LCNFs were further assembled into PVA films to fabricate high-strength composites. The results showed that when the addition of redispersed LCNFs was up to 16.9%, the tensile strength and elongation at break of the as-prepared composite film increased by 325.2% and 335.2%, respectively. This study demonstrated a more sustainable approach to utilize LCNFs to produce biomass-based composite films than those of CNF-based composite films. [ABSTRACT FROM AUTHOR]

The microstructure and properties of lignocellulosic fibers usually change during the drying process due to the hornification of fibers. The water retention ability of fibers is an effective way to reflect the degree of fiber hornification. In this study, the effects of lignin content on the microstructural properties of dried-redispersed LCNFs (DLCNFs) were extensively explored. The results showed that the high content of lignin could maintain the microstructural integrity of DLCNFs. The water retention value and hornification degree of high lignin content DLCNFs (22.1%, w/w) were 289.8% and 6.9%, which were much lower than those of low lignin content (6.2%, w/w) DLCNFs. This was probably because that the crosslinking between lignin and carbohydrate effectively prevented the hydrogen bonding formation in the interior-fibers and exterior-fibers, and reduced the irreversible hornicficatoin of LCNFs. This study will be beneficial for the development of the LCNF drying mechanism. [ABSTRACT FROM AUTHOR]

Lignin-containing cellulose nanopapers are emerging multifunctional materials in the fields of coatings, films, and packaging. However, the forming mechanism and properties of nanopapers with various lignin content have not been thoroughly studied. In this work, a mechanically strong nanopaper was fabricated based on lignin-containing cellulose micro- and nano-hybrid fibrils (LCNFs). The influence of lignin content and fibrils morphology on the formation process of nanopapers was investigated to understand the strengthening mechanism of nanopapers. LCNFs with high lignin content provided nanopapers with intertwined micro- and nano-hybrid fibrils layers with small layer spacing, while LCNFs with low lignin content offered nanopapers interlaced nanofibrils layers with large layer spacing. Although lignin was expected to interfere with hydrogen bonds between fibrils, the uniformly distributed lignin contributed to the stress transfer between fibrils. Due to the good coordination between microfibrils, nanofibrils and lignin (as network skeleton, filler and natural binder, respectively), the well-designed LCNFs nanopapers with lignin content of 14.5 % showed excellent mechanical properties, including tensile strength (183.8 MPa), Young's modulus (5.6 GPa) and elongation (9.2 %). This work deeply reveals the relationship between lignin content, morphology and strengthening mechanism of nanopapers, and providing theoretical guidance for employing LCNFs as structural and reinforcing materials to design robust composites. • The forming mechanisms of nanopapers with different lignin content were revealed. • The strengthening mechanism of LCNFs nanopapers was systematically investigated. • Lignin can preserve the mechanical properties of nanopapers by aiding stress transfer. • The influence of different molding methods on nanopapers strength was revealed. [ABSTRACT FROM AUTHOR]

• Cellulose nanofibers containing various content lignin were obtained. • Lignin content of pulp had two-sides on the mechanical fibrillation and rheology. • High content lignin interfered in gel strength and yield stress of LCNF suspensions. • LCNF suspensions with residual lignin show excellent recovery capacity and strong network. This study aims to investigate the relationship between lignin content, morphology, and rheology of lignin containing cellulose nanofibers (LCNFs). The morphology and rheology of LCNFs were dominated by lignin content. Lignin content had two-sides on mechanical fibrillation. At high lignin content (23.79 %), reduced efficiency of defibrillation resulted in large LCNFs connecting with lignin patches. LCNF suspensions exhibited low viscosity, weak gel behavior due to infirm fibril network. Small yield stress of 1.14 Pa suggested that fibril network was easily disrupted. At residual lignin of 6.52 %, fibril bundles were sensitive to defibrillation, producing long and flexible LCNFs with high capacity of entanglement. The entangled fibril network had high viscosity and strong gel like behavior. Creep compliance of 0.09 Pa−1 and large yield stress of 4.25 Pa indicated excellent resistance to deformation. The desired rheology can be tailored by lignin content, providing practical guidance on novel rheology-dependent LCNF based materials. [ABSTRACT FROM AUTHOR]

The rapid development of the industry has led to the destruction of the earth's ozone layer, resulting in an increasingly serious problem of excessive ultraviolet radiation. Exploring effective measures to address these problems has become a hot topic. Lignin shows promise in the design and preparation of anti-ultraviolet products due to its inherent properties. However, it is important to investigate way to enhance the reactivity of lignin and determine its application form in related products. In this study, phenolic reactions with tea polyphenols were conducted through acid-catalyzed conversion, utilizing organic solvent lignin as the primary material. The phenolic hydroxyl content of the original lignin increased significantly by 218.8 %, resulting in notable improvements in UV resistance and oxidation resistance for phenolic lignin. Additionally, micro-nanocapsule emulsions were formed using phenolic lignin particles as surfactants through ultrasonic cavitation with small-molecule sunscreens. A bio-based sunscreen was prepared with phenolated lignin micro-nanocapsules as the active ingredient, achieving an SPF 100.2 and demonstrating excellent stability. The sunscreen also exhibited strong antioxidant properties and impermeability, ensuring user safety. This research offers a current solution for improving the application of lignin in sunscreens while also broadening the potential uses of plant-based materials in advanced functional products. [Display omitted] • A green method for preparing phenolic lignin by tea polyphenol. • A stable Pickering emulsion was prepared by tea polyphenols phenolated lignin. • Small molecule sunscreen and phenolic lignin exhibits a synergistic effect. • Bio-based sunscreen with excellent anti-UV, antioxidant and anti-permeability [ABSTRACT FROM AUTHOR]

• Lignin-polypyrrole interpenetrating networks were developed for supercapacitor (SCs). • LCNFs was used as both flexible substrates and active materials for SCs. • The capacitive strengthening mechanism of lignin was systematically investigated. • The mechanical strengthening mechanism of composite membrane was studied. Lignin-containing cellulose nanofibrils (LCNFs) are emerging and promising multifunctional nanomaterials for economical and eco-friendly flexible supercapacitors (SCs). However, the strengthening mechanism of lignin on the capacitive and mechanical performance of LCNF-based nanocomposite electrodes has not been deeply studied. Herein, a mechanically strong nanocomposite electrode with excellent capacitive performance was fabricated by decorating a sodium lignosulphonate/polypyrrole (LS/PPy) interpenetrating network onto LCNFs, the relationship between lignin content, LCNFs morphology and electrodes performance was systematically investigated. Results showed that lignin could effectively strengthen the capacitive and mechanical performance of the electrodes via providing pseudocapacitance generated by the reversible conversion of quinone/hydroquinone and controlling the fibrillation degree of LCNFs. With decreasing the lignin content, LCNFs gradually transformed from nanofibril bundles to uniform nanofibrils, forming an electrode with hierarchical porous structure, highly interconnected conductive network, high active site exposure rate and excellent capacitive and mechanical performance. However, insufficient lignin could weaken the capacitive and mechanical performance of the electrodes via reducing quinone/hydroquinone content, electrodes porosity and LCNFs strength. Therefore, electrodes with lignin content of 11.4% displayed excellent tensile strength (20.46 MPa) and areal specific capacitance (2567 mF cm−2, 1 mA cm−2). The assembled all-solid-state supercapacitor (ASSC) delivered high coulombic efficiency (∼98%) and energy density, 88.6 μWh cm−2 (499.9 μW cm−2) and 1.74 mWh cm−3 (9.8 mW cm−3) for areal and volumetric energy (power) density, respectively. This work systematically reveals the strengthening mechanism of lignin on the capacitive and mechanical performance of the electrodes and provides theoretical guidance for constructing high-performance LCNF-based nanocomposite electrodes. [ABSTRACT FROM AUTHOR]

Camellia oleifera fruit shell (COFS) and Camellia oleifera seed shell (COSS) are agricultural residues in the tea-oil processing, and rich in lignin. Analyzing the characteristics of the milling wood lignin from COFS (COFS-MWL) and COSS (COSS-MWL) was a fundamental step in achieving efficient application of the shells. The analysis showed that COFS-MWL was a kind of G/S type lignin, while COSS-MWL contained catechyl lignin (C-lignin) coexisting with G/S type lignin. This means that COSS was expected to become an important source of C- lignin. In addition, activation energies of COFS-MWL and COSS-MWL pyrolysis reaction were calculated based on Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose model. The mean values obtained from two methods were similar about 174 kJ/mol and 268 kJ/mol, respectively. The main thermal degradation products of COSS-MWL were catechols at the pyrolytic temperature of 700 °C. The result confirmed again that COSS-MWL had rich unique C-lignin structure. In general, this study will be of great significance for the production of catechol compounds from biomass and the high value-added development of agricultural residues. [Display omitted] • 2D HSQC NMR analysis showed MWL-COFS was a kind of G/S type lignin. • MWL-COSS contained catechyl lignin (C-lignin) coexisting with G/S type lignin. • Activation energy of MWL-COSS was higher than MWL-COFS calculated by FWO and KAS models. • The MWL-COSS had higher thermal stability than MWL-COFS. • Main pyrolysis products of MWL-COSS were catechols at the pyrolytic temperature of 700 °C. [ABSTRACT FROM AUTHOR]

• The lignin-based solid acid catalyst possessed 0.60 mmol/g of sulfonic densities and 4.62 mmol/g of total acid densities. • Five times recycling and reuse of lignin-based solid acid can be achieved. • More than 80 % yield of short rod-like cellulose nanofibers can be obtained after microfluidization. • The large crystallinity index and low aspect ratio of short rod-like cellulose nanofibers reach to 82 % and 10–28, respectively. Robust environmental regulations are driving the chemical industries to develop low-cost, eco-friendly, and efficient solid acid catalysts for catalytic transformation of cellulose into high-value products. In our work, lignin separated from enzymatic hydrolyzed residues was used as the carbon source to synthesize lignin-based solid acid (LC-SO 3 H) via facile carbonization-sulfonation process. Cellulose nanofibers (CNFs) and platform chemicals (mainly glucose and formic acid) were efficiently transformed from cellulose through LC-SO 3 H catalytic hydrolysis pretreatment combined with microfluidization. Short rod-like CNFs were obtained with large crystallinity index of 82 % and small aspect ratio of 10-28. Furthermore, LC-SO 3 H can be recycled and reused. After five successive cycles, the yield of CNFs, glucose, and formic acid reached up to 90.8 %, 3.9 %, and 2.1 %, respectively. This work provides a novel, low-cost, and environmental benign approach to prepare CNFs and platform chemicals, and it holds great potential for green and sustainable production of high value-added biomass products. [ABSTRACT FROM AUTHOR]