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In this study, representative lignin samples differing in hydroxyl content, molecular weight, linkage composition and lignin units ratio were prepared from eucalyptus wood by different isolation means and modification means: milled wood lignin (MWL), kraft lignin classified at different pH (KL), lignocresol (LC), lignoresorcinol (LR), lignopyrogallol (LP) as well as lignocresol secondary functional switched samples (LC 2ndderiv). The structure of various lignins was characterized in detail by Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). In order to eliminate the interference of other factors, bovine serum albumin (BSA) with relatively simple protein structure and different kinds of lignin and their derivatives were selected as the research objects. The adsorption/desorption behavior and mechanism between lignin samples and BSA were studied by quartz crystal microbalance with dissipation monitoring (QCM-D). The results showed that the content of phenolic hydroxyl was the main factor affecting the interaction of lignin and BSA, but in addition, the molecular size, linkages composition and the types of lignin units also had important effects on its adsorption behavior. The research will provide theoretical guidance and all-round reliable basic data for the interaction of lignin on lignocellulose hydrolysis enzymes in industrial application.

Improving the retention and drainage aid performance of high speed papermaking processes is an important and challenging issue. In this study, fiber modification was used to improve the papermaking retention and drainage aid performance. The graft copolymerization of glycidyl methacrylate (GMA) with cellulose fibers was initiated using Fe2+-thiourea dioxide(TDO)-H2O2 in a mild aqueous medium; the synthesized polyglycidyl methacrylate grafted cellulose (CPGMA) was used to replace softwood bleached kraft pulp(SBKP) and hardwood bleached kraft pulp(HBKP), to study their retention and drainage aid behavior in the cationic polyacrylamide (CPAM)/colloidal SiO2/ anionic polyacrylamide (APAM) system. Graft copolymerization significantly enhanced the fiber hydrophobicity. Additionally, the papermaking process drainage aid performance and retention rate of the filler increased significantly with an increase in the CPGMA substitution rate. A small amount of CPGMA (0.5 %) significantly improved the dewatering ability and some improved the retention performance of the wet end of papermaking. SBKP-polyglycidyl methacrylate grafted cellulose (S-CPGMA) exhibited better retention and drainage aid performance than HBKP-polyglycidyl methacrylate grafted cellulose (H-CPGMA). Thus, introducing Fe2+-thiourea dioxide(TDO)-H2O2 initiated graft copolymerized S-CPGMA (in mild aqueous media) into pulp could improve the retention and drainage aid performance of the wet part of paper production.

A green method for lignin quantitation based on the completely dissolved solution of lignocellulosic biomass in LiCl/DMSO and UV spectrophotometry was developed. The method is accurate, sensitive, mild, and does not use hazardous reagents.

The mechanical pulp of mulberry branches was evaluated as a raw material for the production of cellulose II and its subsequent conversion to nanocellulose via high-pressure homogenization, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidation, and sulfuric acid hydrolysis. The morphology, chemical structure, crystallinity, and thermal stability of the nanocellulose samples prepared by each method were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and thermogravimetric analysis. The results showed that nanocellulose prepared by high-pressure homogenization exhibited higher aspect ratio (>100), and the weight loss peak in the DTG chart was 361 °C, with the best thermal stability, whereas that prepared by sulfuric acid hydrolysis featured shorter fiber length (96±31 nm) and a higher crystallinity (78.2 %).The TEMPO oxidized nanocellulose (TOCN) had smaller width (5.5±1.6 nm) and high carboxyl content (1.5 mmol/g). In addition, we have further studied the application of TOCN in the wet end of papermaking, replacing the colloidal SiO2 in CPAM/ colloidal SiO2/APAM retention system with the same amount (3600 ppm) of TOCN. The study found that the strength of the paper obtained by adding TOCN instead of the traditional wet end additives is similar, and the water drainage and retention properties of the pulp are improved.

Poplar alkaline peroxide mechanical pulp (APMP) was used as plant fiber raw material, and it was graded according to the lignin content. The graded raw materials were used to prepare lignin-containing microfibers (LCMFs) by micro-grinding, and then, the lignin-containing microfiber cryogels (LCMF-cryogels) were prepared by vacuum freeze-drying. The particle size distribution, micromorphology and dispersion stability of LCMFs were characterized by laser diffraction particle size analyzer, transmission electron microscopy and Zeta potentiometer. Then, the crystalline structure, pore structure, surface morphology and adsorption properties of LCMF-cryogels were analyzed. In addition, LCMF-cryogels were compared with the microfiber cryogels (MF-cryogels) which use commercial eucalyptus chemical bleaching pulp as raw material. It was proved that using poplar APMP as raw material to prepare cryogels is more advantageous. The results showed that the lower the lignin content in plant materials, the better the oil adsorption ability of cryogels. This is because the binding effect of lignin on the fiber is reduced, which makes the fibrillation of the fiber easier by external mechanical action. The maximum adsorption capacity of LCMF-cryogel for methyl silicone oil is 215 g/g, while that of MF-cryogel prepared from commercial eucalyptus chemical bleaching pulp is 102.5 g/g. The analysis of the properties of raw fiber and the gel pores shows that the change in the fiber morphology caused by different pulping methods has important influence on the development of LCMF-cryogels by mechanical refining. Poplar APMP is more suitable for preparing fiber-based cryogels oil-absorbing materials than commercial eucalyptus chemical bleaching pulp.

Two phenolic compounds (p-cresol and pyrogallol) were introduced into the benzyl position of poplar lignin by a phase separation method to obtain lignin-based derivatives with different structural properties called poplar lignophenols (LPs). The maximum protein adsorption capacity of LPs is 50–70 times greater than that of the industrial lignin under the same conditions. The interaction between poplar LPs and bovine serum albumin (BSA) near its isoelectric point (pH = 4.5) was studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption and desorption of BSA molecules on different LPs were investigated at various pH values of the buffer solution (2.1, 6.4, and 10.0), and the interaction mechanism between LP and BSA species was examined. The obtained results showed that hydrogen bonding was the strongest binding force between LPs and BSA as compared with hydrophobic and electrostatic interactions. The findings of this work can help to establish a relationship between the contents of hydroxyl groups, molecular structures, and molecular sizes of LPs and proteins under different pH conditions.

The graft copolymerization of lignocellulosic fibers with glycidyl methacrylate (GMA) using a Fe2+–thiourea dioxide–H2O2 redox system (Fe2+–TD–H2O2) was studied to overcome the problems of poor compatibility and low surface strength when cellulosic fibers are composited with synthetic polymers. The results show that cellulose–poly(GMA) (CPGMA) was successfully synthesized from GMA and bleached Eucalyptus cellulosic fibers by Fe2+–TD–H2O2 in a mild aqueous solution. CPGMA had high graft rate (244%), high content of epoxy group, and high stability in water. X-ray diffraction patterns and 13C cross-polarization magic angle spinning nuclear magnetic resonance spectra analyses showed that graft copolymerization did not change the crystalline structure of the CPGMA fiber backbone cellulose, but the crystallinity of the CPGMA fiber decreased with an increase in amorphous PGMA grafting. Scanning electron microscopy confirmed that the grafting reaction occurred both inside and outside the fiber. The specific surface area and pore diameter of the grafted fibers were significantly affected by the grafting. The hydrophobicity of the fibers was significantly enhanced by graft copolymerization. PGMA grafting can enhance the compatibility between the modified fiber and synthetic polymer matrix, improving the processing runnability and product properties of composite materials. A high intensity focused ultrasound method was used to analyze the fiber surface strength. It was confirmed that graft copolymerization significantly improved the surface strength of the grafted fibers. Graft copolymerization can significantly improve the dimensional stability of cellulosic fibers.

Objective There is limited information from population‐based cancer registries regarding prognostic features of bilateral primary breast cancer (BPBC). Methods Female patients diagnosed with BPBC between 2004 and 2014 were randomly divided into training (n = 7740) and validation (n = 2579) cohorts from the Surveillance, Epidemiology, and End Results Database. We proposed five various models. Multivariate Cox hazard regression and competing risk analysis were to explore prognosis factors in training cohort. Competing risk nomograms were constructed to combine significant prognostic factors to predict the 3‐year and the 5‐year survival of patients with BPBC. At last, in the validation cohort, the new score performance was evaluated with respect to the area under curve, concordance index, net reclassification index and calibration curve. Results We found out that age, interval time, lymph nodes invasion, tumor size, tumor grade and estrogen receptor status were independent prognostic factors in both multivariate Cox hazard regression analysis and competing risk analysis. Concordance index in the model of the worse characteristics was 0.816 (95% CI: 0.791‐0.840), of the bilateral tumors was 0.819 (95% CI: 0.793‐0.844), of the worse tumor was 0.807 (0.782‐0.832), of the first tumor was 0.744 (0.728‐0.763) and of the second tumor was 0.778 (0.762‐0.794). Net reclassification index of the 3‐year and the 5‐year between them was 2.7% and −1.0%. The calibration curves showed high concordance between the nomogram prediction and actual observation. Conclusion The prognosis of BPBC depended on bilateral tumors. The competing risk nomogram of the model of the worse characteristics may help clinicians predict survival simply and effectively. Metachronous bilateral breast cancer presented poorer survival than synchronous bilateral breast cancer., This study aimed to find out prognostic factors and put forward a new prognostic model in bilateral primary breast cancer from the Surveillance, Epidemiology, and End Results Database. We demonstrated that the new prediction was as effective as the model of bilateral tumors, however, more simply and convenient.

The use of lignin is limited by its heterogeneity and complexity. This study was processed using different methods to obtain spruce milled wood lignin (SMWL), spruce kraft lignin (SKL), and spruce lignocresol (SLC) for comparative analysis of the structure and antioxidant activity. SMWL has a complete softwood lignin side-chains structure and lignin carbohydrate complexes. SKL contains fewer ether bonds, while more conjugate structures and condensed structures contribute to the color. However, the α-position of the lignin side chain eliminates most of the hydroxyl and ether bonds (β-O-4/α-OH, phenylcoumaran, and dibenzodioxocine structure) and effectively grafts p-cresol in the phase separation reaction. It not only inhibits the self-condensation of lignin, but also forms the 1,1-diarylpropane unit while protecting β-O-4 linkages from not breaking. Importantly, SLC has few conjugate structures that result in the lightest color among all lignin isolated. Besides, SLC has a high yield and contains trace carbohydrates, indicating that the phase separation method can achieve great amounts of purity separated lignin. The antioxidant activity of lignin was evaluated, results show that 85% of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals were scavenged at the end of 60 min. Owing to its unique color, structural properties, and continuous antioxidant activity, SLC has the potential to manufacture antioxidant cosmetics.

Supramolecular crosslinked porous lignin-based polyacrylic acid was laboratory-synthesized by copolymerizing lignin-grafted acrylic acid of potassium persulfate as an initiator and N,N-methylene bisacryl amide as a crosslinker. The effects of lignin type on the absorbent properties and the pore structure were studied. The results showed that the addition of lignin affects the swelling behavior and the pore structure of the resin. Lignopyrogallol-grafted-polyacrylic acid resin (LP-g-PAA) exhibited the best absorption properties (2137 g/g) and the highest BET specific surface area. Furthermore, the swelling behavior of the resins complied with the Schott’s swelling kinetics model. The salt tolerance of the LP-g-PAA resin was studied, and the results were as follows: KCl > KNO3 ≈ LiCl > K2SO4 > K2CO3 > CaCl2 > FeCl3.

To graft epoxy and ester functional groups onto cellulose nanofibrils (CNFs) and to overcome their poor hydrophobicity, we studied the modification of CNFs using graft copolymerization wi ...

The separation of lignin from woody biomass and subsequent conversion into useful products requires a solution to the problem of its solubility. The expanded C9 formula of lignin, along with its atomic and functional groups, was determined by elemental analysis and NMRs spectroscopy. Based on the thus-obtained expanded C9 formula, the cohesion parameters of lignin dispersion (10.8–11.1 cal1/2·cm−3/2), polarity (4.15–4.31 cal1/2·cm−3/2), hydrogen bonding (6.30–7.38 cal1/2·cm−3/2), and solubility (13.2–14.0 cal1/2·cm−3/2) were respectively calculated using atomic and functional group contributions method. We established the relationship between lignin structure and lignin solubility parameters. The dissolution characteristics of wheat straw organic acid lignin, industrial eucalyptus kraft lignin, bamboo kraft lignin, and softwood kraft lignin in formic acid–H2O, acetic acid–H2O, and formic acid–acetic acid–H2O solvent systems were analyzed. The results indicate that the dissolution behavior of lignins follows the solubility parameters theory. We have developed a lignin dissolution model according to the lignin structure. This model obeys the solubility parameter theory, overcomes the limitations of the “like dissolves like” principle in organic acid–water systems, and provides a concise method for the selection of lignin solvent systems and the quantitative determination of their solvent composition.

In this study, the depolymerization of naked oat stem cell wall and the dissolution of its chemical compositions during autohydrolysis in subcritical water (150−210 °C, 0.38–1.85 MPa) were investigated, to explore the potential of naked oat stems as raw materials for green biorefinery. Our results showed that the sequence of lignin removal was from parenchyma cells to sclerenchyma fibers in the tissues, and from the middle lamella to the inner side of the cell wall, and finally to the middle layer of the cell wall. The total lignin removal rate reached the highest value (47.7 %) at 190 °C, and by this time, the cell wall was depolymerized and the autohydrolysis residue was in the form of pulp. At 190 °C, the hemicellulose side chain was degraded by 100 %, and the ash was almost completely removed. When the reaction temperature was further increased to 210 °C, the removal rate of xylose was close to 100 %, and degradation of the cellulose crystal zone began. We found that in moderately subcritical water, all the chemical compositions of naked oat stem were expected to be dissolved in a controllable and orderly manner. Our findings will play a substantial role in solving the problem of lignocellulosic biomass composite cell wall resistance to depolymerization in a single green solvent.

The structure of kraft lignin is heterogeneous and the reaction activity is low due to the complicated and somewhat uncertain chemical reactions under the strong alkali and high temperature conditions of kraft pulping chemistry. At present, people still lack understanding of its structure, so it is difficult to be used as high quality industrial raw material for many years despite its huge output. In this paper, the phenolation potential of industrial Spruce Kraft Lignin (SKL) in phase separation system was explored. Compared with previous studies on phase separation reaction, due to the direct use of lignin as feedstock, sulfuric acid would only act as a phenolation catalyst, and is no longer used for swelling cell walls and hydrolyzing carbohydrates, so a modest reduction of acid concentration is feasible. In the phase separation system, the benzyl position of lignin was activated to selectively graft the p-cresol groups. Due to the protection of organic phase on lignin, the breakage of the β linkages and the condensation reaction of lignin were effectively prevented, so the original structure of lignin was well preserved. In order to capture the detailed structural changes of lignin after phenolation in phase separation system, FT-IR, GPC and quantitative NMR techniques (1H-NMR, 31P-NMR and 2D-NMR) were used to analyze the changes of main functional groups, linkages and substructures of industrial lignin samples before and after phenolation. The results showed that the industrial spruce kraft lignin still have many active sites which can be modified by phenolation. And through p-cresol treatment, a kind of high activity industrial lignin with more phenolic hydroxyl groups, more uniform molecular size and higher purity was obtained. Then the molecular structure models of spruce kraft lignin before and after phenolation is proposed respectively based on the molecular weights, quantitative analysis of functional groups, linkages, substructures and introduced p-cresols. This will be helpful to understand the structural changes of industrial spruce kraft lignin during phenolation in phase separation system, and provide guidance for the high value utilization of this high activity industrial lignin in the future.

The synthesis process of the phenolic resin adhesive was developed in the 19th century, and its excellent environmental resistance and high bonding strength make it one of the main wood adhesives. With the development of industry, phenolic resin adhesive is not only used in plywood, wood processing and laminate, but also in automobile, aerospace, composite materials and other fields. Herein we review the main synthetic processes and latest research progress for phenolic resin adhesives, the capacity distribution of major domestic phenolic resin enterprises, analysis of domestic phenolic resin consumption, import and export volume and price, Chinese plywood production, and the main production and export markets. Furthermore, research and discussion on the commercial application of domestic phenolic resin adhesives in plywood were carried out, which provides a reference for development of better phenolic resin adhesives that meet the development needs of the country, along with quality and economic competitiveness.

Corn stalk rind was used for biorefinery using the formic acid–acetic acid–H2O (FA–AA–H2O) system, which is sustainable and can be applied industrially. Fiber, cellulose, lignin, and hemicellulose can be obtained simultaneously from biorefineries in an environment-friendly manner. To provide a theoretical basis for the utilization of organic acid biorefinery lignin (OABL) in developing high-value products, the lignin reaction mechanism, structure and properties were studied in detail. The OABL was investigated using wet chemistry, Fourier-transform infrared spectroscopy, 13C- and 2D-nuclear magnetic resonance spectroscopy, and gel permeation chromatography. OABL was found to be composed of guaiacyl (G), syringyl (S), and p-hydroxyphenyl units with molar contents of 25.3 %, 52.2 %, and 22.5 %, respectively, along with 21.9 % p-coumarate (pCA) and 4.80 % ferulate (FAL). During the biorefinery process, the lignin was highly depolymerized and the β-O-4 bonds decreased from 52.2 % to 5.07 %. Condensation reaction between lignin Cα-C6 to form diphenylmethane structures took place. The ratio of the condensed G and S units (Gcond./G and Scond./S) increased to 68.1 % and 59.5 %, respectively. OABL contains a large number of lignin-carbohydrate complexes (LCC), with phenyl glycoside (PhGlc) LCC of 4.86/100Ar, and benzyl ethers (BE) LCC of 5.22/100Ar. Furthermore, OABL was highly acylated: the acetylation, formylation, and total acylation degree by molar were 33.1 %, 10.3 %, and 43.4 %, respectively. Acylation mainly occurred at Cγ of the side chain and C4 of the aromatic ring. High carbohydrate, high acyl, and high condensed structures in OABL make it have broad application prospects.

Pycnoporus sanguineus (Ps) and Candida tropicalis (Ct) can selectively degrade the lignin and hemicellulose in lignocellulosic cells respectively; Ps-Ct mixed fermentation may improve the multiphase reaction performance of lignin in the cell walls. Alkaline nitrobenzene oxidation, ozonation and infrared spectroscopy, which are the in-situ analytical techniques of lignin in the cells, were used to characterize the delignification kinetics, the reactions of the non-condensed, β-O-4 structures and their stereochemistry of lignin in wheat straw in Ps and Ps-Ct fermentations. Results indicated that the biodelignification processes in Ps and Ps-Ct fermentations of wheat straw, being divided into a fast phase and a following slow phase, had the characteristics of a pseudo-first-order reaction in both the phases. The lignin reaction pathways in Ps and Ps-Ct mainly included the cleavage of ring, Cα-Cβ, β-O-4, and the cleavage and polymerization of 5-5⿲. Compared with Ps fermentation, Ps-Ct fermentation enhanced the biodegradation of condensed, β-O-4 structures and threo β -O-4 structures in the lignin in the fast phase. A proposal scheme of biodelignification by Ps and Ps-Ct is outlined for the first time. These results will be helpful for the understanding and application of lignocellulosic biomass by mixed fermentations.

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

It is important for lignocellulosic bioconversion of wheat straw to be intensified by co-cultivation of Pycnoporus sanguineus with Candida tropicalis. The biodegradation properties, involving the e ...

Nanocellulose is a type of nanomaterial with high strength, high specific surface area and high surface energy. Additionally, it is nontoxic, harmless, biocompatible and environmentally friendly and can be extracted from biomass resources. The surface groups of cellulose show high surface energy and binding activity on the nanoscale and can be modified by using various methods. Because nanocellulose has a high elastic modulus, rigidity and a low thermal expansion coefficient, it is an excellent material for polymer reinforcement. This paper summarizes the reinforcement mechanisms of nanocellulose polymer composites with a focus on the role of theoretical models in elucidating these mechanisms. Furthermore, the influence of various factors on the properties of nanocellulose reinforced polymer composites are discussed in combination with analyses and comparisons of specific research results in related fields. Finally, research focus and development directions for the design of high-performance nanocellulose reinforced polymer composites are proposed.

Cafferic acid-O-methyltransferases (COMT) down-regulated transgenic and wild-type switchgrass were separated into lignocresols (LCs) and sugars by a phase separation method involving 72% sulfuric acid and cresol. The isolated LCs were characterized by FTIR, GPC, 1H NMR and 2D-HSQC to understand potential structural modification caused by transgenic engineering lignin or phase separation treatment. No significant changes were found in terms of molecular weights and the amount of incorporated p-cresols between transgenic and wild-type switchgrass LCs. However, the compositions, ratios of syringyl (S) units to guaiacyl (G) units, were changed significantly leading to decrease in S units and increase in G units for transgenic switchgrass LC. The benzodioxane structures and 5-hydroxyguaiacyl units were observed in the 2D-HSQC implied that 5-hydroxyconiferyl alcohol was incorporated into lignin as a result of COMT-down-regulation in the transgenic process.

The exploration of solvent system to completely dissolve lignocellulosic biomass is of great important for the development of biomass based materials and chemicals. Dimethyl sulfoxide containing certain amount of lithium chloride (LiCl/DMSO) was proved an effective solvent system for the dissolution of ball-milled wood. In this paper, four samples of rice straw, internode (stem without node), stem, leaf (leaf and sheath) and whole straw, with and without 1 h of ball milling treatment, were used to investigate the effects of their dissolution in LiCl/DMSO solvent on the chemical composition of regenerated and enzymatically hydrolyzed materials. Because of the structural difference from wood, samples expose d to 1 h of milling were almost completely dissolved. The chemical nature of the regenerated material and of residual after enzymatic hydrolysis of rice straw was analyzed and the susceptibility of this rice straw to the enzymatic hydrolysis was evaluated.

Ball-milled rice straw was dissolved in a lithium chloride/dimethyl sulfoxide (LiCl/DMSO) solvent system, regenerated, and subjected to enzymatic hydrolysis to obtain regenerated cellulolytic enzyme lignin (RCEL). The structure of the isolated lignin was characterized by elemental analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR). Alkaline nitrobenzene oxidation (NBO) was conducted to analyze the structural characteristics of the in-situ lignin. The results showed that the rice straw RCEL was composed of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) phenylpropane units, with relatively high amounts of H units. The yield of RCEL is about 5% units higher than that of cellulolytic enzyme straw lignin (CEL) on the basis of total lignin in the original rice straw. When compared to the CEL obtained by the traditional method, there were no observed differences versus RCEL in terms of the elemental compositions, NBO product yields, and S/G ratio. The weight-average molecular weight of RCEL was 6835, which was lower than that of CEL, indicating that some rice straw lignin linkages were cleaved during LiCl/DMSO dissolution.

The effects of black liquor replacement cooking (BLRC) on wheat straw soda-anthraquinone (AQ) pulps and their lignin structures were investigated by using different black liquor replacement ratios (BLRR) and alkaline nitrobenzene oxidation and ozonation. The residual AQ, alkali, and dissolved lignin, as well as carbohydrates in the wheat straw black liquor, greatly influence wheat straw soda-AQ cooking. The influence could be controlled by different BLRR. The BLRC with around 60% BLRR resulted in superior delignification selectivity. The residual AQ and dissolved carbohydrates in the black liquor are beneficial to delignification selectivity, while the dissolved and degraded lignin can slow the delignification rate. No obvious differences were found in the lignin condensation and β-O-4 structure degradation by the BLRC at different BLRR compared to control soda-AQ cooking. The BLRC technology has potential application because it reduces chemical charge and chemical recovery load and results in higher yield and quality of pulp.

This paper investigated cell morphology, chemical components, lignin distribution and inorganic elements distribution of corn stover fractions. Corn stover fractions, classified as stalk rind, stalk pith and leaf, had different tissues, cell morphology and chemical compositions. Corn stalk rind had good fiber morphological characteristics for papermaking, while stalk pith, having short fibers and high contents of parenchyma and vessel, was not suitable for papermaking. Stalk rind had the highest lignin and cellulose content but the lowest hemicellulose content among all the fractions. The major ash-forming elements in corn stover fractions were potassium, chlorine, silica, calcium, magnesium and sulfur. Potassium and chlorine took more than 86% of total inorganic elements in stalk rind while silica content was much higher in leaf and stalk pith than that in stalk rind. Perivascular sclerenchyma and subepidermal sclerenchyma of stalk rind were more lignified than the other tissues. The highest lignin concentration existed in cell middle lamella and corner. All corn stover fractions could be good biorefinery feedstock based on their main chemical compositions, though they are obviously heterogeneous in aspects of cell morphology and chemical characteristics.

Thermomechanical pulp (TMP) fibers were separately oxidized using 4-acetamido-2,2,6,6-tetramethylpiperidyl-1-oxyl (4-acetamido TEMPO) and cationized by 2,3-epoxy-propyl-tri-methyl ammonium chloride. The goal was to evaluate the influences of the interaction of oxidized, cationized, and untreated fiber components on paper properties. TEMPO-mediated oxidation can enhance interfiber bonding potential of mechanical long fibers. Cationization can improve the interfiber bonding only when the cationic charge density is lower than 400 mmol/kg; the bonding capacity drops off with increasing cationic charge density. However, as these modified long fibers were mixed with untreated long fibers and short fibers, the interaction between these fibers affected the paper sheet strength. The addition of oxidized fibers improved the sheet density remarkably, but it only had apparent effort on tensile strength when the carboxyl group content was less than 500 mmol/kg; higher carboxyl content did not enhance the sheet properties. The addition of cationized fibers had no positive effort on sheet density, and when they were mixed with other fiber fractions the interaction between positively charged and negatively charged fibers resulted in poor paper structure with rough surface and decreased tensile strength. Both oxidation and cationization had adverse influence on intrinsic fiber strength and tear index; either high carboxyl content or high cationic charge density could lead to remarkable decrease in these two properties. The side reactions, such as β-elimination and alkoxy fragmentation during TEMPO-mediated oxidation and alkaline degradation during cationization, which degraded the cellulose, were responsible for the drastic decrease in zero span tensile strength and tear strength.

This study was committed to the simulation of a roadway excavation in the geologically horizontal strata at great depth based on physical modeling test. A new approach of Physically Finite Elemental Slab Assemblage (PFESA) was employed for construction of the large-scale physical model simulating roadway excavation in stratified rocks. The roadway excavation without support in our test was designed as two phases, i.e. phase 1: full-face excavation and phase 2: staged excavation. The experimental test was carried out under the deep ground stress condition of unbalanced confinement. Rock response to the excavation was monitored and captured in real-time and over the entire field by using infrared (IR) thermography, incorporated with such image processing procedures as data statistics, noise removal and two-dimensional DFT (Discrete Fourier Transformation) for extracting features from the resulting thermographies. IRT, defined as the statistical mean value of the IR image matrix, was used as a measure of rock response, characterizing the full-face excavation, the staged excavation as a linear process and a non-linear process respectively by its time-Marching scheme within the IR radiation domain. The denoised IR images and the two-dimension Fourier spectra provide an enhanced understanding of the excavation response in terms of initiation, propagation and coalescence of rock damage in the spatial and frequency regimes respectively.

Three kinds of wheat straw black liquor were extracted by alkaline solution at 25 °C, 100 °C, and 165 °C, and were precipitated by the stepwise addition of acid to pH 10.5, 9.0, and 2.0, respectively. The corresponding three lignin fractions were isolated. The characteristics of these lignin fractions were investigated, and their impacts on anti-oxidant properties were evaluated. The pH 10.5 fractions with low lignin content, low phenolic hydroxyl content, and high lignin molecular weight showed very poor radical scavenging ability. The pH 9.0 and 2.0 fractions with high phenolic hydroxyl contents exhibited excellent radical scavenging ability. The major portion of the degraded lignin was precipitated in the pH 2.0 fraction, resulting in a lower molecular weight and higher phenolic hydroxyl content as compared to the pH 10.5 and pH 9.0 fractions. The high extraction temperature degraded more lignin and generated more phenolic hydroxyl groups. Therefore, the lignin fractions extracted at 165 °C exhibited the best radical trapping potential as compared to the lignin extracted at 100 °C and 25 °C. The coefficients of DPPH• removal for the lignin fractions were ordered in sequence by phenolic hydroxyl content, methoxyl content, molecular weight, E+T content, and NO yield of lignin. The lignin fraction extracted at higher temperature and precipitated at lower pH had the best radical scavenging ability.

Carboxylic acid groups were introduced onto thermomechanical pulp (TMP) long fiber surfaces by 2,2,6,6,- tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation in the present study. The number of introduced carboxylic groups was closely related to the NaClO dosage, and more flexible fibers with lower curl and kink index were generated. Lignin was dissolved during the TEMPO-mediated oxidation, and its content was 24.2% with a carboxylic content of 1444 mmol/kg, in contrast to the control, which had 33.6%. Meanwhile, significant decreases in uncondensed lignin and β-O-4 lignin were observed during the TEMPO-mediated oxidation. The generation of carboxylic acid groups enhanced both the tensile and burst strengths of oxidized TMP significantly, and the value was 70% higher than the control with a carboxyl content of 1444 mmol/kg. However, side reactions during TEMPO-mediated oxidation led to a decline in intrinsic fiber strength, which may have contributed to the decline in paper tear strength.

In order to improve the properties of thermomechanical pulp (TMP), the influences of the TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxyl radical)-mediated oxidation on recycled TMP properties were investigated, and the impacts of recycling process on TEMPO-mediated oxidized TMP properties were studied as well. The results showed that TEMPO-mediated oxidation is an effective way to enhance the recycled TMP inter-fiber bonding dependent properties due to the introduction of carboxylic acid groups onto pulp, while the oxidation had some negative impacts on the tear index, zero span tensile index, and brightness. The oxidation-recycling (O-R) process had remarkable adverse impacts on TMP compared with the recycling-oxidation (R-O) process. The tensile, burst, tear strengths, as well as the zero-span tensile strength dropped sharply when oxidized TMP was recycled, and the physical strength properties decreased with the increasing recycling times. The opacity was improved after the O-R treatment, although the O-R treatment had an adverse impact on the pulp brightness.

The influences of various factors in 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation on delignification, lignin aromatic ring and side chain structures of thermomechanical pulp (TMP) were investigated. The results indicate neither TEMPO nor NaBr alone can provoke changes in lignin content or lignin structure under weakly alkaline conditions. However, NaClO and NaClO-NaBr were able to remove lignin effectively, causing remarkable changes in lignin structure. Delignification was promoted when TEMPO was used with NaBr and NaClO. In contrast to NaClO alone, an additional 15% lignin was removed when TEMPO-mediated oxidation system was used, but it did not induce further changes on lignin structure. Increased doses of oxidizing agent and reaction time also improved the oxidation of cellulose and delignification, but they did not have a significant impact on lignin aromatic and side chain structures.