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Thehighly efficient utilization of lignin is of great importance for the development of the biorefinery industry. Herein, a novel "core-shell" lignin nanoparticle (LNP) with a diameter of around 135 nm was prepared, after the lignin was isolated from the effluent of formic acid fractionation via dialysis. In an attempt to endow composite materials with vital functionalities, the LNP was added to the starch film and the starch/polyvinyl alcohol (PVA) or starch/polyethylene oxide (PEO) composite film. The results showed that the hydrophobicity performance of the synthesized films was enhanced significantly. Specifically, the dynamic water contact angle value of the starch/PVA composite film with 1% (wt) addition of LNPs could be maintained as high as 122° for 180 s; the starch/PEO composite film also achieved an excellent water contact angle above 120°. The addition of LNPs promoted the formation of some rough structures on the film surface, as shown by the scanning electron microscopy images, which could repel the water molecules efficiently and are closely related to the enhanced hydrophobicity of the starch film. What is more, the as-prepared LNP conferred strengthened thermal stability and ultraviolet blocking properties on the starch composite film. The structural combination of the polymer film with LNPs holds the promise for providing advanced functionalities to the composite material with wide applications.

Biografting is a promising and ecofriendly approach to meet various application requirements of products. Herein, a popular green enzyme, laccase, was adopted to graft a hydrophobic phenolic compound (lauryl gallate, LG) onto chitosan (CTS). The resultant chitosan derivate (Lac/LG-CTS) was systematically analyzed by Fourier transform infrared (FTIR), grafting efficiency, scanning probe microscopy (SPM), and X-ray diffraction (XRD). This grafting technique produced a multifunctional chitosan copolymer with remarkably enhanced antioxidant property, hydrophobicity, and moisture barrier property. Furthermore, the swelling capacity and acid solubility of the copolymer film decreased significantly, although the tensile strength and elongation were slightly weakened as compared to those of native chitosan. These results suggest that the Lac/LG-CTS holds great potential as a food-packaging material, preservative agent, or edible coating material.

Solar desalination devices utilizing sustainable solar energy and the abundant resource of seawater has great potential as a response to global freshwater scarcity. Herein, a bilayered solar evaporator was designed and fabricated utilizing a facile paper sheet forming technology, which was composed of cellulose fibers decorated with Fe3O4 nanoparticles as the top absorbent layer and the original cellulose fibers as the bottom supporting substrate. The characterization of the cellulose fibers decorated with Fe3O4 nanoparticles revealed that the in situ formed Fe3O4 nanoparticles were successfully loaded on the fiber surface and presented a unique rough surface, endowing the absorber layer with highly efficient light absorption and photothermal conversion. Moreover, due to its superhydrophilic property, the cellulose fiber-based bottom substrate conferred ultra-speed water transport capability, which could enable an adequate water supply to combat the water loss caused by continuous evaporation on the top layer. With the advantages mentioned above, our designed bilayered paper-based evaporator achieved an evaporation rate ~1.22 kg m−2 h−1 within 10 min under 1 sun irradiation, which was much higher than that of original cellulose cardboard. Based on the simple and scalable manufacture process, the bilayered paper-based evaporator may have great potential as a highly efficient photothermal conversion material for real-world desalination applications.

Herein, a great potential approach initiated by laccase is applied to graft the biopolymers (chitosan and phenols) onto the unbleached Kraft pulp fibers to enhance the hydrophobicity and strength. The results showed that the chitosan and laccase/phenols exhibited a synergistic action on the significant improvement of the hydrophobicity of the KP pulp fibers. Compared with the base paper, a high sizing degree value (227.08 s) was achieved when the fibers were treated by the laccase/4-hexyloxyphenol/chitosan (Lac/HP/CTS) system. The water retention value of the corresponding KP fibers reduced from 176.8 to 171.3%, and the Kappa number of treated fibers increased from 26.8 to 29.3, confirming the successful graft of HP onto the fibers. The effect of the reaction parameters, including the temperature, pH, HP and chitosan dosage, reaction time and pulp suspension consistency on the strength and hydrophobicity was investigated. pH value was found as the most remarkable factor influencing the sizing degree and gave a highest sizing value (506.2 s) at pH 5.5. The strength performance presented an opposite trend against the hydrophobicity, since the number of formed hydrogen bonds is the least when the hydrophobicity is the best. This work is extremely significant for providing valuable reference on improving the hydrophobicity and strength performance of papers through a green and biological way.

In this work, we prepared novel cellulosic paper by incorporating tannin into the kraft pulp for potential application in active food packaging. The kraft pulp fibers were firstly periodate oxidized to obtain the dialdehyde cellulosic fibers, and then reacted with varied dosages of tannin to incorporate them into the fibers by covalent bondings between aldehyde groups on cellulose and active hydrogen on tannin. Handsheets were prepared using the tannin incorporated fibers through papermaking process and the properties were characterized. The percentage of tannin in the paper increased with the increase of the tannin dosage. FT-IR spectra confirmed the successful incorporation of tannin into the cellulosic fibers. It was found that paper after incorporation of tannin turned to be surface hydrophobic with contact angles higher than 90°, which may probably due to the covalent bonds between tannin and cellulose. The handsheets show high antioxidative and UV-shielding properties, which both increased with the increase of the tannin percentage in the paper. Water vapor transmission rate (WVTR) decreased after the incorporation of tannin, and this could facilitate its application in food packaging. The breaking length of tannin incorporated paper decreased insignificantly, less than 10% with the tannin percentage as high as 45%.

The removal of lignin is important to the recovery of saccharides from the pre-hydrolysis liquor (PHL) in kraft-based dissolved pulp production. A one-step process for lignin removal from PHL via treatment with horseradish peroxidase (HRP) in the presence of Ca2+ was proposed, and its principle was studied. The results demonstrated synergy between HRP and Ca2+ in lignin removal from PHL, whereas NH4+ had little effect on lignin removal. HRP treatment in the presence of 60 mmol/L of Ca2+ resulted in a lignin removal of 64.8% accompanied by a saccharide loss of 14.2%. HRP catalyzed both the polymerization and depolymerization of the lignin in the PHL. The HRP-catalyzed lignin polymerization rendered some lignin insoluble enabling it to be directly removed. The HRP-catalyzed depolymerization of lignin decreased its molecular weight with an evident increase in its carboxyl content. The insoluble complexes formed between the lignin with carboxyl and the Ca2+ facilitated the removal of the depolymerized lignin.

An efficient separation technology for hydrolysates towards a full valorization of bamboo is still a tough challenge, especially regarding the lignin and lignin-carbohydrate complexes (LCCs). The present study aimed to develop a facile approach using organic solvent extraction for efficiently fractionating the main components of bamboo hydrolysates. The high-purity lignin with only a trace of carbohydrates was first obtained by precipitation of the bamboo hydrolysate. The water-soluble lignin (WSL) fraction was extracted in organic solvent through a three-stage organic solvent extraction process, and the hemicellulosic sugars with increased purity were also collected. Furthermore, a thorough characterization including various NMR techniques (31P, 13C, and 2D-HSQC), GPC, and GC-MS was conducted to the obtained lignin-rich-fractions. It was found that the WSL fraction contained abundant functional groups and tremendous amount of LCC structures. As compared to native LCC of bamboo, the WSL fraction exhibited more typical LCC linkages, i.e. phenyl glycoside linkage, which is the main type of chemical linkage between lignin and carbohydrate in both LCC samples. The results demonstrate that organic phase extraction is a highly efficient protocol for the fractionation of hydrolysate and the isolation of LCC-rich streams possessing great potential applications.

Artificial antioxidants are synthesized from fossil sources and are now widely used in the polymer, food, and cosmetics industries. The gradual depletion of fossil resources makes it practically significant and necessary to produce green antioxidants from renewable lignocellulosic resources. Herein, short-time hydrothermal (STH) treatment was developed for production of lignin-derived polyphenol antioxidants (LPAs) from poplar wood under conditions of high temperature and high pressure. LPA yields from 21.5 to 37.6 % on the basis of lignin in untreated wood were obtained by STH treatments as result of lignin depolymerization at 190-200 °C and 10 MPa in 5-8 min. Depolymerization reactions were confirmed by the much lower molecular weight of LPA (1076 g mol-1 ) than that of native lignin (4094 g mol-1 ). NMR spectroscopy revealed the structural features of lignin in the isolated LPA, namely syringyl and guaiacyl units with well-preserved interunit linkages. A Folin-Ciocalteu assay indicated that each LPA molecule contained 5.4 phenolic hydroxyl groups on average, much more than other technical lignins. The remarkable antioxidant ability of LPA was verified by the radical-scavenging index of 53.5-67.3, much higher than 0.2-11.1 of the commercial antioxidants butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). STH treatment only requires water and heat for production of high-value antioxidant, which provides a green and sustainable method for the utilization of lignocelluloses.

Biomass pretreatment is an essential strategy to overcome biomass recalcitrance and promote lignocellulosic bioconversion. Here, a reusable organic solvent system (formic acid-methanesulfonic acid) was explored to pretreat poplar under a mild temperature (below 100 °C). The results showed that the co-solvent system could extract basically complete hemicelluloses and part of lignin with original cellulose retained in the pretreated substrates. Meanwhile, sulfonic acid groups were introduced into lignin structure remained in the substrates. The glucose conversion yield of the substrates with a higher concentration of sulfonic acid groups (13.2 mmol/kg) reached 45.9 % by reducing the hydrophobic interaction between lignin and cellulase, showing 89.3 % improvement compared with that of the substrates treated with single formic acid. This progressive study aimed to develop a new strategy to realize sulfonation and promote enzymatic hydrolysis of substrates by using mild organic solvent pretreatment.

Chiral nematic papers (CNPs) with mesopores structure based on cellulose nanocrystals (CNCs) were fabricated successfully via a swelling and freeze-drying method. The order of the original chiral nematic cellulose nanocrystals film was preserved in CNPs, which was proved by scanning electron microscopy (SEM), polarized optical microscopy (POM) measurements and circular dichroism (CD) spectra. The CNPs exhibited excellent optical responsive properties to different solvents. Inspired by this feature, a colorable ink containing amounts of gel particles was prepared by pulverizing CNPs/water mixture into a suspension. Patterns written in suspension ink with various colors can be formed when soaked with different solvents. Moreover, CNPs displayed an irreversible color response to compression. Additionally, the hydrophilicity of CNPs was tuned by polyethyleneimine. Modified CNPs exhibited different colors under the identical solvent environment when compared to the original one. Aqueous PEI can be used as an ink to depict responsive photonic patterns on CNPs.

A biorefinery process characterized with all components valorization based on flow-through fractionation using recyclable aqueous formic acid as solvent is proposed. Within 20 min, wheat straw was efficiently fractionated into cellulose-rich material, hemicellulosic sugars and lignin. Delignification achieved 86%, and the dissolved lignin was further fractionated into water insoluble lignin (WIL) and water soluble lignin (WSL) by dilution using water. WIL accounted for 33–81% of total dissolved lignin depending on treatment severity. GPC and 2D NMR analysis of WIL from 62% formic acid at 130 °C revealed non-condensed structure, 81% retention of ether bond, and molar weight of 3016 g/mol. The well retained structure of lignin is crucial for catalytic conversion into aromatic monomers. Characterization of WSL by GPC and Folin-Ciocalteu assay revealed a structure of oligomeric phenols containing 2.8 phenolic hydroxyl groups and five phenylpropane units in each molecule with molar weight of 1123 g/mol on average.

Whole valorization of carbohydrate and lignin from biomass was achieved by rapid flow-through fractionation (RFF) within 15 min. Wheat straw was effectively deconstructed into its principle components without degradation by using easily recyclable aqueous formic acid (72 wt %) at 130 °C. The obtained cellulose-rich solid showed a nearly complete glucan recovery and 73.8 % glucose conversion after enzymatic hydrolysis. Xylan also reached full recovery with negligible furfural formation with a sum of 80 % of oligo/mono xylose in spent liquor and 20 % of xylan remaining in the solid. Up to 75.4 % lignin was dissolved in the spent liquor and further fractionated into water-insoluble (WIL) and water-soluble lignin (WSL) by dilution with water. WIL showed a non-condensed and well-preserved structure with 84.5 % β-O-4 remaining, which is believed to be beneficial for catalytic conversion into low-molecular-weight chemicals and fuels. The concentration of employed formic acid was below the formic acid/water azeotrope, and therefore the reaction medium could be restored through simple distillation. Together with the joint valorization of lignin and carbohydrates, the presented RFF is a promising process for sustainable biorefinery.

Wood flour (WF) of poplar, acid hydrolysis residue (AHR) of corn cob from xylose production, and cellulose fibers (CF) from bleached eucalyptus pulp were compared as functional fillers of lignocellulosic-plastic composites (LPC) in terms of tensile strength and thermal stability. WF showed a negative effect on tensile strength of LPC. AHR-filled LPC at 10% of filling level exhibited an improvement by 8.9%, whereas higher filling level led to a decrease of tensile strength due to poor interfacial compatibility, as revealed by SEM analysis. Remarkably, tensile strength achieved a maximum of 25.8 MPa for CF-filled LPC at 2.5% of filling level, which was an approximately 76.7% improvement compared to the control. Dependence of LPC thermal stability on chemical compositions of fillers was revealed. WF-filled LPC showed a lower onset decomposition temperature compared to the control due to the presence of xylan, while thermal stability of AHR-filled LPC was enhanced due to the presence of cross-linked phenolic polymer lignin.

Lignin is the second largest component of vascular plants and is the most abundant renewable aromatic polymer on our planet. The attractiveness of lignin valorization lies in its conversion into high value aromatic chemicals and biofuels through fractionation and upgrading. The literature has demonstrated that the presence of aryl ether bonds in native lignin was a key factor for the conversion, while the conventional technical lignins from carbohydrate-first processes, e.g. pulp and cellulose ethanol production, are intensively condensed and lack these linkages due to the intense delignification conditions. Here, by using the β-O-4 lignin model dimer GG, we reveal the dramatic degradation of GG and the synchronous formation of relatively stable intermediate β-O-4 dimers, C6C3 enol ether and the formylated enol ether, within the first 5 min under the conditions of 72 wt% aqueous formic acid and 130 °C, conditions suitable for biomass fractionation. Based on these findings, we propose a simple but effective strategy of rapid flow-through fractionation (RFF), which separates the dissolved lignin from the reactor in time and space, thereby preserving these labile aryl ether bonds in native lignin. The application of RFF of poplar wood with a short residence time of 2.6 min attained 75% delignification with an equivalent of the β-O-4 motif in native lignin. Structure-preserved lignins (β-O-4 retention, 75.0%–85.4%) were also harvested from wheat straw with good lignin yields (61.7%–78.5%). Contrarily, batch fractionation acted as a protracted war and resulted in extensive cleavage of aryl ether bonds as suggested by 92%–100% loss of the β-O-4 motif under the same conditions. Because of the well-preserved structure, RFF lignin can be used as a good feedstock to boost its downstream valorization, especially for hydrogenolysis into monophenolic chemicals and fuels. It is noteworthy that the carbohydrate fraction from RFF retained structural integrity and almost reached theoretical yields for glucan and xylan.

Integrated fractionation process based on autohydrolysis (H) and subsequent formic acid delignification (FAD) has been considered as an effective strategy to separate the main lignocellulosic components in view of the biorefinery. For the better understanding of the structural changes of the lignin during the integrated process, the fractionated aspen lignins were thoroughly characterized by Fourier transform infrared (FT IR), 13C, two-dimensional heteronuclear single quantum coherence (2D-HSQC) and 31P nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Compared to the milled wood lignin (MWL), the fractionated lignins had higher amounts of phenolic OH groups as due to the cleavage of β-O-4 linkages and less alcoholic OH groups mainly due to the esterification of the aliphatic OH groups by formic acid. Demethylation action of the lignin was not significant during the FAD process. More syringyl-propane (S) units were extracted during the H-FAD process than guaiacyl-propane (G) units resulting in a higher S/G ratio and more OCH3 in the fractionated lignins. Furthermore, autohydrolysis of aspen at higher temperature led to more condensation of the fractionated lignins which exhibited higher molecular weight and more β-5 and β-β linkages. The fractionated lignins exhibited high purities due to the breakage of the lignin-carbohydrate bonds.

The removal of lignin is important to the recovery of saccharides from the pre-hydrolysis liquor (PHL) in kraft-based dissolved pulp production. A one-step process for lignin removal from PHL via treatment with horseradish peroxidase (HRP) in the presence of Ca

Cellulose nanocrystal (CNC)-based materials have gained increasing attention because of their great potential applications in optical devices, anticounterfeiting and structural coatings. However, due to the inherent brittleness of CNC, fabricating highly strong and solvent-resistant CNC derived materials is still an important and challenging task. Here, a straightforward, matrix swelling and in-situ insertion method is developed to fabricate chiral nematic composite films by intercalating poly(ethylene imine) (PEI) into the as-prepared swollen matrix of CNC films. The resulting composite CNC films exhibit a great increase in ultimate strain and toughness and especially have an extremely high folding endurance. Notably, the intercalation of PEI into CNC films also leads to a fluorescence enhancement effect, which endows the films circularly polarized luminescence (CPL) properties. The CPL handedness and dissymmetry factors (glum) of the composite films can be controlled. Furthermore, the CNC composite films display optical responsiveness (structure color, fluorescence intensity) to various stimuli, including ethanol and formaldehyde environments. We expect the current in-situ intercalation technique to be promising in manufacturing foldable encryption materials.

Removal of colloidal particle and lignin from pre-hydrolysis liquor (PHL) is important for the subsequent processing and utilization of the saccharides in the PHL. Cationic polymers treatment is a common method for the purpose, and pectinase pre-treatment of PHL can improve the efficiency of the treatment with cationic polymers. To investigate the mechanism of pectinase pre-treatment for improvement of the cationic polymer efficiency, polygalacturonic acid (PGA) was added in the colloidal lignin and dissolved lignin model substances systems, respectively, and the effects of polygalacturonic acid (PGA) and its pectinase pre-treatment on the removal of colloidal and dissolved lignin in the following cationic polymer treatment process were studied. The results showed that the presence of PGA caused the increase of negative charge density of the colloidal lignin and dissolved lignin systems, which lowered the efficiency of the cationic polymers and negatively affected the removal of both the colloidal lignin and the dissolved lignin. After pectinase treatment, the PGA present in the colloidal and dissolved lignin system was degraded and the negative effects on the cationic polymers were eliminated, and the efficiency of the cationic polymers was improved. Compared to the colloidal lignin and dissolved lignin systems with PGA, less cationic polymers were needed for the same systems with pectinase treatment to obtain the similar lignin removal level.

The removal of colloidal particle and lignin from a pre-hydrolysis liquor (PHL) of biomass is essential for its processing as well as for the value-added utilization of saccharides in the PHL. In this paper, pectinase was used to treat an aspen PHL obtained by pre-hydrolysis at 160 °C, and a novel process in which pectinase treatment was followed by cationic polymer flocculation to enhance colloidal particle and lignin removal was investigated. The results showed that pectinase treatment caused an approximately 50% decrease in the cationic demand of the aspen PHL. For the controlled PHL, approximately 68 mg/L poly-dimethyl diallyl ammonium chloride (pDADMAC) was needed to remove nearly all of the colloidal particles with 40.3% maximum lignin removal; for the enzyme-treated PHL, only approximately 34 mg/L pDADMAC was needed to remove nearly all of the colloidal particles with 43.3% lignin removal. In addition, the enzyme treatment decreased the loss of saccharides during subsequent pDADMAC treatment at the concentration necessary for maximum lignin removal.

Bamboo chips were efficiently fractionated using an integrated process of autohydrolysis and formic acid to induce rapid delignification. Autohydrolysis pretreatment facilitated oligosaccharide production, while the subsequent rapid-delignification using formic acid at a low liquid/solid ratio with a relatively short reaction time allowed obtaining cellulose fibers and lignin. The major inter-unit linkages of side-chain in lignin were cleaved during the combined fractionation process. The lignin fraction exhibited higher purity, more phenolic OH groups, less condensed phenolic OH groups, and higher syringyl/guaiacyl ratio (S/G) as compared to MWL and formic acid lignin from the direct formic acid delignification. These results indicate that the combined fractionation process presents a promising approach to the commercial utilization in the biorefinery industry.

To promote the efficient utilization of lignocellulosic materials, one-step fractionation by formic acid-based organosolv process under pressure has been studied for converting lignocellulose in its main components. Lignin and hemicelluloses were selectively dissolved, while cellulose was not obviously degraded. Under optimized conditions (85% formic acid, a liquor-to-solid ratio of 7:1, and a temperature of 145°C for 45 min), this process provided a high efficient way to separate the main components of bamboo, obtaining 42.2% cellulose pulp, 31.5% lignin, 8.5% hemicellulose-rich fraction, 3.56% furfural and 3.80% acetic acid. Cellulose pulp with satisfying viscosity could easily be bleached to a high brightness of over 87% ISO with a short bleaching sequence, and had an acceptable paper strength properties. The recovered lignin fraction contained a small amount of carbohydrates and a considerable part of proteins and p-hydroxycinnamates. Additionally, the organic substances in hemicellulose-rich fraction...

Fabrication of nanostructures with multiple functions templated by cellulose nanocrystals (CNCs) has become very attractive, and chiral structures fabricated via evaporation-induced self-assembly (EISA) have become particularly important for building photonic films. However, films obtained so far suffer from low mechanical strength, which significantly hinders their applications. Here, we report a facile way to obtain highly flexible latex films with tunable structural colors via CNC templating. First, composite films (CFs) containing silicone-modified acrylic latexes (SALs) and CNCs were prepared via EISA. At mixing ratios of SALs to CNCs of 0.2–0.4, homogenous films were obtained, where the latexes cohere together to form a network. After alkali treatment followed by rinsing with water or alcohol, CNCs could be removed, leading to the formation of free-standing latex films. The chiral nematic (N*) structure originating from the organization of CNCs via EISA was retained in the latex film, leading to the preservation of the structural color. Due to a reduced helical pitch caused by the deformation of the porous latex network during the removal of CNCs and the subsequent drying process, the reflection of the film could be blue shifted, and the extent was closely related to the type of solvent used during rinsing. Interestingly, the structural color of the latex film could be reversibly tuned by water adsorption and dehydration, which could be ascribed to the expansion/shrinking of the porous latex network. The flexibility of the pores in expansion/shrinking also effectively released the internal stress of the film when it was stretched and/or deformed. This feature, combined with the intrinsic flexibility of the backbones formed by the crosslinking of SALs, imparts the film impressive mechanical strength. The maximum elongation at break reached 34.5%, ∼8 times larger than that of the best film reported so far.

Bamboo was fractionated using formic acid based on a one-step organosolv process under high pressure (at 145 °C for 45 min, 0.3 MPa) and at atmospheric pressure (at 101 °C for 120 min), respectively. High-pressure formic acid lignin, atmospheric formic acid lignin and milled wood lignin of bamboo were subjected to comprehensive structural characterization using gel permeation chromatography (GPC), Fourier transform infrared (FTIR) and solution-state NMR techniques ( 1 H, 13 C, 2D-HSQC, and 31 P-NMR spectroscopies). The results indicated that the formic acid fractionation under high pressure presents a quick and efficient delignification method by enhancing the cleavage of interunitary bonds in lignin (β-O-4′, β-β and β-5′), and dissolved lignin also occurred condensation reaction. As compared to atmospheric formic acid lignin, high-pressure formic acid lignin obtained showed higher purity and yield, and had relatively higher contents of phenolic and carboxylic groups.

Autohydrolysis of wood chips prior to separating lignin and cellulose is an effective method to pre-extract hemicelluloses, where the change of the structure and chemical composition in the hydrolyzed wood chips inevitably impact the subsequent separation efficiency of the remaining components. In this work, autohydrolysis of poplar wood chips under different intensity was carried out, and the relationships between the chemical/physical changes in the hydrolyzed wood chips and the accessibility of remaining components was evaluated. The results indicated that the removal of most hemicelluloses and minor lignin increased the porosity, specific surface area, and internal hydrophilicity of the wood chips, enhancing the accessibility of wood components to alkali solution as well as the diffusion of the alkali-soluble substance outward. The hydrophobic lignin or lignin-like substance accumulated on the surface of the wood chips could rapidly dissolve into the alkali solution, thus, having no adverse effect on the permeation of alkali solution into the wood chips, although they might create a barrier blocking the passage of water penetration.

The lignin in PHL could be modified and recovered from pre-hydrolysis liquor (PHL) by horseradish peroxidase (HRP) treatment. The enzyme-modified lignin (EML) separated from PHL was used to adsorb and remove methylene blue (MB) from a model dye effluent; the adsorption performance of EML was studied. The results indicated the carboxyl content of the lignin in PHL increased by HRP treatment, and the EML removed from PHL had a carboxyl content of 0.69 mmol/g and a BET surface area of 25.6 m2/g. With the increase of pH, the adsorption capacity of EML obviously increased. The maximum MB adsorption capacity of EML was 210.2 mg/g and 241.1 mg/g at 298 K and 308 K, respectively. The fitting results revealed that the equilibrium adsorption isotherms and adsorption kinetics followed the Langmuir model and pseudo-second-order model, respectively.

In this study, the pre-hydrolysis liquor (PHL) was recycled during aspen chip water pre-hydrolysis, and the effects of PHL recycling on the extraction and accumulation of the hemicellulosic saccharides especially that with high molecular weight in the PHL were studied. The results showed that the concentration of hemicellulose saccharides in PHL depended on the pre-hydrolysis temperature and PHL recycling times. Compared to the unrecycled PHL, the concentration of hemicellulosic saccharides in PHL increased significantly when recycling PHL once or twice at 170°C. Furthermore, the amount of high-molecular-weight hemicelluloses (HMHs) in PHL recycled once at 170°C increased from 2.58g/L (unrecycled) to 6.18g/L, but the corresponding average molecular weight of HMHs decreased from 9.2kDa to 7.6kDa. The concentration of hemicellulosic saccharides in PHL decreased with PHL recycling time at 180°C, accompanied by the formation of a significant amount of furfural.

Composite films with oxidized carbon nanotubes (o-CNTs) incorporated in the chiral nematic liquid crystals (CNLCs) formed by cellulose nanocrystals (CNCs) were fabricated for the first time. Induced by solvent evaporation, the isotropic aqueous dispersion containing o-CNTs and CNCs gradually forms lyotropic CNLCs, and the framework of the CNLCs can be retained in the final solid films, confirmed by polarized optical microscopy observations and scanning electron microscopy observations. During this evaporation-induced self-assembly process, the predispersed o-CNTs were spontaneously integrated in the liquid crystal matrix. It is found that the incorporation of a trace amount of o-CNTs (∼1.5 wt %) can induce obvious structural changes of the films. The reflection spectrum shifts to higher wavelengths with increasing content of o-CNTs, resulting in a continuous increase of the helical pitch of the CNLC phase. Confined in the liquid crystal matrix, the randomly oriented o-CNTs in the aqueous dispersion are fo...

Herein, the chitosan-based (CS) composite film was fabricated via a simple and efficient blending approach by adding poplar hot water extract (HWE), bentonite (BT) and chitosan. The addition of HWE largely improved the UV blocking ability and antioxidant properties of the resultant composite film, and simultaneously a tortuous path was constructed within the chitosan matrix to enhance the water vapor and oxygen barriers after the addition of BT. Specially, the content of HWE at 10 wt % gave a greatly decreased UV light transmittance at 280 nm to the CS-BT-HWE composite film that was 99.36% lower than that of CS-BT film, and the oxidation resistance was 9.65 times higher than that of CS-BT. The mechanical properties and surface morphological observation evaluated by scanning electron microscopy (SEM) and scanning probe microscope (SPM) confirmed the film had a denser structure. The internal chemical structure analyzed using solid state NMR, FTIR and X-ray spectra exhibited the resultant Maillard structure and strong hydrogen bonding that contributed to the improved mechanical properties. Overall, the as-prepared composite film has great potential as food packaging materials, and also provides a high-efficient utilization pathway for HWE.

A type of cellulose solvent, i.e., aqueous N-methylmorpholine- N-O xide (NMMO) solutions, was used to modify cellulose nanocrystal (CNC) photonic films. CNC films can be swollen by NMMO, resulting in red-shifted reflected colors. The swelling effect is supposed to come from NMMO permeation into the crystalline regions of individual CNCs and intercalating in between CNC particles. When NMMO was removed, the reflected colors of CNC films blue shifted because of the reduced helical pitches. NMMO-treated CNC films display reversible responsive colors to humidity changes in several minutes. Increasing NMMO content allows CNC films to enlarge the responsive color range. Aqueous NMMO can be used as an ink to depict responsive photonic patterns on CNC films. This post-treatment approach to producing responsive colors and photonic patterns in CNC films may be applied to the areas of sensor, anti-counterfeiting, and decoration.

An enzymatic method for functionalization of chitosan (CTS) with a hydrophobic monophenol compound (4-hexyloxyphenol, HP) using laccase was presented, yielding a chitosan derivative (Lac/HP-CTS) as a coating on the Kraft paper sheet. The dissolve oxygen, UV/vis, FT-IR and 1H NMR spectra were used to characterize the chemical structure of the resulting copolymer. The results showed that HP was oxidized into the semi-quinone structure, and then was bonded onto the chitosan via Schiff-base reaction and electrostatic interaction. The hydrophobicity and strength of paper were evaluated after coated by the pure chitosan or chitosan derivative. Compared with paper coated by pure chitosan, the hydrophobicity and wet strength of the coated paper via the chitosan derivative were improved significantly at the coating concentration of 0.6 g/100 mL with the coat weight of 1.53 g/m2. Meanwhile, the different enhancement behaviors in the strength (dry or wet) performance were observed, due to the greatly influenced interaction of the hydrogen bonding between the copolymer coating and the cellulose fibers by the grafted HP. Further, the hydrophobicity and strength were observed to be enhanced even at a diluted concentration of 0.1 g/100 mL and a relatively low coating weight of 0.26 g/m2 for the chitosan derivative. Taken together, this study is significant for broadening the coating application of the biomodified chitosan on the packaging papers.

Micellar hydrogel (MHG) films exhibit polarized-light interference colors upon being stretched. Based on the results of small-angle X-ray diffraction (XRD), we proposed a new possible structural model of MHGs, where polymer chains are cross-linked by multilamellar micelles. The mechano-optical response of MHG films is attributed to the oriented multilamellar micelles induced by shear and tensile stress during stretching process. UV–vis spectra demonstrated that each visible color under polarizers results from the blending of multiple interference colors. Scanning electron microscopy (SEM) observations and birefringence measurements were used to investigate the relationship between micellar morphologies and birefringence of MHG films. It showed that the structures and morphologies of micelles determine the birefringent intensity that further influences the response sensitivity of MHG films. Rich responses can be achieved by stacking and stretching of MHG films, and desired patterns can simply be depicted into MHG films, leading to their promising applications in a variety of fields, such as digital coding and information encryption areas.

Prehydrolysis of lignocellulose produces abundant hemicellulose-derived saccharides (HDS). To obtain pure HDS for application in food or pharmaceutical industries, the prehydrolysis liquor (PHL) must be refined to remove non-saccharide compounds (NSC) derived from lignin depolymerization and carbohydrate degradation. In this work, activated carbon (AC) adsorption was employed to purify HDS from NSC with emphasis on adsorption selectivity. The adsorption isotherms showed the priority of NSC to be absorbed over HDS at low AC level. However, increase of AC over 90% of NSC removal made adsorption non-selective due to competitive adsorption between NSC and HDS. Size exclusion chromatography showed that the adsorption of oligomeric HDS was dominant while monomeric HDS was inappreciable. The limited selectivity suggested that AC adsorption is infeasibility for HDS purification, but applicable as a pretreatment method.

Thermal acetic acid/sodium acetate hydrolysis (ASH) on poplar wood chips were carried out to obtain functional xylooligosaccharide, then the hydrolyzed wood chips were subjected to kraft pulping (KP) to fractionate cellulose and lignin. The separated three fractions were extensively characterized for further utilization in view of the integral biorefinery concept. The extraction efficiency of hemicelluloses by ASH strongly depends on the buffer ratio of the acetic acid/sodium acetate buffer solution. The ASH facilitated producing a high ratio of xylooligosaccharides with high molecular weight, while prevented further degradation of the saccharides, and simultaneously inhibited the condensation of lignin facilitating the subsequent kraft delignification. The obtained cellulose pulps had higher intrinsic viscosities as compared with the traditional autohydrolysis-KP process. Moreover, the ASH-KP process delivered a high purity of lignin with relatively high molecular weight. Therefore, the proposed integrated fractionation strategy is conducive to convert the lignocellulosic components into bio-based functional materials.

Poplar wood chips were extracted in an acetic acid/sodium acetate (SA/AA) buffer solution at 180 oC for 60 minutes, with a solid-to-liquid ratio of 1: 6, to investigate the effect of pH on the extraction performance in terms of chemical compositions of the extract. The pH was controlled by varying the concentrations of sodium acetate and acetic acid in the buffer system. Results showed that the SA/AA system could promote the dissolution of hemicellulose, obtaining more oligosaccharides and monosaccharides, and could also inhibit the excessive decomposition of monosaccharides. When extracting poplar wood chips in a SA/AA system of pH=3.7, the yield of oligosaccharides was the highest, while the contents of furfural and hydroxymethyl furfural decreased by 25% and 30%, respectively, compared to conventional water extraction systems. Moreover, the amount of lignin extracted in the S/AA process was also higher than that in a conventional hot water extraction process.

Oligosaccharides (OS) production using wood prehydrolysis liquor (PHL) is a crucial subject with significant economic and environmental benefits for wood biorefinery. However, this is a challenging task due to the presence of a diverse palette of lignin-derived contaminants. In this work, lignin contaminants were classified into macro-lignin particles (MLPs), amphiphiliclignin derivatives (ALDs) and small lignin fragments (SLFs) based on their colloidal and molecular behaviors. Accordingly, a process was developed to destabilize ALDs and MPLs synergistically by applying polycations at an elevated pH, which achieved 57.8% lignin removal. The remaining SLFs were adsorbed by macroporous resin with pore size of 20 nm at least, leading to 95.2% of final lignin removal and 66.6% of OS recovery. This study has both scientific and practical significance for wood biorefinery because of the low cost of chemicals employed and the regeneration ability of macroporous resin.

Pre-pulping extraction of hemicellulose from wood produces a prehydrolysis liquor (PHL) rich in monosaccharides and oligosaccharides (OS). However, PHL also contains non-saccharide compounds (NSC), mainly lignin-derived byproducts. A promising usage of PHL is to separate OS from NSC as value-added products. In this work, NSC selectivity was defined as the ratio of NSC removal over the sum of NSC and saccharide removal, and applied to evaluate the performance of several separation techniques. Ultrafiltration (UF) of PHL with a molecular weight cut-off (MWCO) from 50 kDa to 1 kDa showed no selectivity toward NSC because of the equal retention of saccharides and NSC. Polymer flocculation using polyaluminium chloride (PAC) was infeasible due to the conflict between NSC selectivity and NSC removal. Lime treatment showed remarkable selectivity up to 90% due to the specific removal of phenolic lignin derivatives. Adsorption by a macroporous resin attained nearly complete removal of NSC with 78.9% saccharide recovery, but at the expense of massive resin consumption. The comparison of NSC selectivity suggested the combination of lime treatment and resin adsorption as an economic and practical process for saccharide separation from PHL.

Formic acid/water binary solvent extraction with formic acid fraction lower than 77.5% (w/w) of azeotrope was used to extract hemicellulose-derived saccharides from poplar wood at various levels of severity. The highest xylose yield of 77.8% and arabinose yield of 93.5% were obtained at 120 °C and 1 h. To reduce cellulose hydrolysis and facilitate downstream xylose crystallization, mild conditions at 90 °C and 4 h was chosen as optimum severity, which led to the highest xylose fraction of 81.7% in all saccharides extracted, with a remarkable xylose yield of 73.1%. Mass balance analysis showed that 5.84% of xylan was degraded, but only 0.25% of xylan ended up as furfural at optimum severity. The proposed extraction process has high feasibility for industrial application since the low formic acid fraction in solvent allows simple recovery and concentration of used solvent.

Hydrothermal pretreatment of poplar wood chips was performed in an acetic acid/sodium acetate buffer medium. To characterize the structural changes of lignin in the pretreatment process, milled wood lignin (MWL) was isolated from both the un-treated and treated poplar wood chips, and analyzed by 1 H-NMR, 13 C-NMR, 31 P-NMR, FT-IR, and GPC-MALLS. Results showed that the lignin in the pretreated wood chips had more phenolic OH groups, less aliphatic OH groups, higher molecular weight, and narrower polydispersity, in comparison with the lignin in the un-treated wood. The acetic acid-sodium acetate buffer pretreatment facilitated the removal of -OCH 3 groups and the cleavage of the inter-unit linkages of β-O-4 bond in the lignin. Furthermore, the re-polymerization of lignin in the acetic acid-sodium acetate buffer pretreatment was found to be less than that in autohydrolysis.

Antioxidant function and solubility in water are highly desirable in many applications of chitosan. In this paper, a xylan/chitosan composite was prepared in an ionic liquid system using glutaraldehyde as a crosslinking agent. The antioxidant activity, reducing capacity and metal ion chelating ability of the resulting composite were determined. The chemical structure and thermal stability were analyzed by FT-IR, XRD and TGA. The results showed that chitosan was successfully cross-linked with xylan by glutaraldehyde in the ionic liquid system. Compared to pure chitosan, the ABTS·+ scavenging activity of the xylan/chitosan composite increased from 10.56% to 97.59%. After cross-linking with xylan by glutaraldehyde, the reducing power of xylan/chitosan composite increased from 0.054 to 2.109. The capacity of chelating metal ion of the composite also increased from 42.35% to 86.71% compared to that of pure chitosan. An underlying mechanism was proposed to account for the improvement of the chemical properties of the chitosan in the composite.

A series of dimethine cyanine dyes, used as fluorescent probes, were synthesized under microwave irradiation, and identified by 1 H NMR, IR, elemental analysis and HRMS. The investigation of their spectral properties in phosphate-buffer saline (PBS) showed that the absorption and emission maxima of the dyes were in the region 370–480 nm and 471–569 nm, respectively. The properties of the dyes as fluorescent probes for living cells imaging and flow cytometry were investigated. The results showed that dyes 1 , 2 , 8 or 9 could penetrate an intact cell membrane, stained the cell nuclear and exhibited bright fluorescence. Little background interference, low cell cytotoxicity and little photobleaching were showed during the imaging tests. The dyes 1 , 8 and 9 could be applied in flow cytometry and dye 1 /PI, dye 8 /PI or dye 9 /PI couple could be proposed as double staining agents to measure sperm cell viability. Thus the dyes represented the cell-permeant fluorescent probes.

Hot water extraction is an important strategy of wood fractionation, by which the hemicelluloses can be separated for value-added products, while the residual solid can still be processed into traditional wood products. In this study, a combined process consisting of specific lignin precipitation and dialysis was proposed to recover hemicellulosic oligosaccharides (OS) from hot water extract (HWE). The results showed that polyaluminium chloride (PAC) precipitation was highly specific to large molecular lignin, leading to 25.1% lignin removal with negligible OS loss through charge neutralization mechanism. The separation was further enhanced by dialysis, reaching 37.6% OS recovery from HWE with remarkable purity of 94.1%. By the proposed process, 56.36 g OS, mainly xylooligosaccharides with two fractions of 5.2 and 0.51 kDa was recovered from one kg dried wood. This process can be envisaged as a great contribution to wood biorefinery.

In this work, a competitive process consisting of polyelectrolyte flocculation, active carbon absorption, and ion exchange was developed for hemicelluloses-derived saccharides (HDSs) purification from prehydrolysis liquor (PHL) of lignocellulose. Results showed that colloidal lignin counted for 20% of non-saccharide compounds (NSCs) and could be eliminated by flocculation at 500mg/L polyaluminium chloride and 50mg/L anionic polyacrylamide. Active carbon was very effective for decoloration of flocculation-treated PHL, but showed limited absorption selectivity toward NSCs. Lignin, the dominant component of NSCs, is characterized with phenolic hydrogen groups. Phenolic lignin could be easily captured by anion exchange resin with 80% removal. The proposed process showed great industrial potential because of the high value saccharides, but also low molecular phenolic lignin.

Homogeneous functionalization of cellulose with chloroacetyl chloride (CAC), 2-bromoisobutyryl bromide (BrBiB), and 2-chloro-2-phenylacetyl chloride (CPAC) was performed in ionic liquid to evaluate the effect of the molecular structure of the reagents on the reactivity of the cellulosic hydroxyl groups. The results showed that the reaction was very selective for the less hindered C6-OH group, but the substitution of the secondary OH group still occurred, which indicated that the acylation of cellulose was only partly regioselective. The reaction extent and regioselectivity of the cellulosic hydroxyl groups partly depended on the molecular structure of the acylating agents. The reaction rate of the CAC was much faster than the relatively bulky BrBiB and CPAC, but the bulky acylating agents showed a higher C6-OH selectivity. Moreover, the BrBiB was less reactive than the CPAC, although they showed the same regioselectivity for the three hydroxyl groups. The acylation decreased the thermal stability of the cellulose, which decreased further as the bulk of the substituted groups increased.