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In the past 70 years, over 8 billion tons of plastics have been produced, the majority of which cannot be fully biodegraded, causing their fragments to be found everywhere in the biosphere, including living organisms. Herein, a group of biodegradable composites were produced by blending poly(butylene adipate-co-terephthalate) (PBAT) with technical lignin through a twin-screw extrusion method. Two strategies were developed to improve the mechanical properties of PBAT/lignin composites: (1) modifying lignin via methylation to reduce hydrogen bonding between −OH groups and (2) enhancing the intermolecular interactions between PBAT and lignin by adding maleic anhydride-graft-PBAT as a compatibilizer. The composites obtained from the two strategies with 60 wt % lignin contents exhibited ideal tensile performance which could meet the requirement of the Chinese National Standard for packaging. The interactions between different composite components were investigated by morphological and thermal analyses. The results showed that when lignin is used as filler in the composites, the molecular mobility of lignin and the size of its agglomerates remarkably impacted the ductility and mechanical strength of the PBAT/lignin films. A simple cost comparison between neat PBAT film and PBAT/lignin composite films indicated that the latter was economically competitive, and the production costs could significantly reduce by 36%.

The present chemical converted graphene sheets are mostly dependent on the exfoliation of graphite with strong oxidants, which suffer from heavy burden of environmental pollution. Here, we report a simple, green and scalable method to synthesize graphene sheets by one-pot activation-synthesis method derived from black liquor, a biomass waste resource in pulping industry. The pulping black liquor consisting of alkali lignin as main components with phenyl skeletons and condensed aromatic segments was successively transferred from heterogeneous chemical states into micron-sized graphene sheets. The proposed conversion mechanism mainly consists of aromatic rebonding, refusion and deoxygenation reaction, in which alkaline species acting as situ-activation agent. The graphene sheets obtained from pulping black liquor (BL-G) show typical hexagonal honeycomb lattice in thickness of 1–3 atomic carbon layers with controllable lateral size ranging from 0.36 to 2.5 μm. After spin-coating single- or few-layer of BL-G sheets onto flexible substrate, it could produce transparent and conductive thin films (TCFs) with sheet resistance as low as 2.1 kΩ sq−1 and 85% transmittance for 550 nm light, suggesting its great potentials using as flexible electrode materials. This green synthesis route may pave a bright way in large-scale production of chemically converted graphene sheets.

To maximize the utilization of Abaca lignin in the current biorefinery, structural characteristics of native lignin from Abaca were firstly comprehensively investigated. Parallelly, effective delignification of Abaca was achieved by alkaline hydrogen peroxide (AHP) process, which facilitated the production of specialty paper in industry. The structural changes of lignin macromolecules during the AHP delignification were illustrated by comparing the structural differences of the released lignin fraction and corresponding native lignin, which were analyzed via the advanced analytical methods, such as 2D-HSQC NMR, 31P NMR, pyrolysis-GC/MS, and GPC techniques. It was found that Abaca lignin is a HGS-type lignin, which is overwhelmingly composed of β-O-4 linkages and abundant hydroxycinnamic acids (mainly p-coumaric acid). In addition, partial cleavage of β-O-4 linkages and p-coumarate in lignin occurred during the AHP delignification process. Meanwhile, AHP process also led to the elevation of H-type lignin units in AHPL. Considering that β-O-4 bond is vulnerable in the catalytic degradation process of lignin, the lignin with abundant β-O-4 linkages is beneficial to the downstream conversion of lignin into aromatic chemicals.

Biodegradable materials are increasingly imperative in modern society owing to their eco-friendly character, but their high cost and limited properties restrict their applications. In this study, lignin-based (30–50 wt%) biodegradable composites with superior performances were successfully prepared by incorporating lignin into the poly(butylene adipate-co-terephthalate) (PBAT) matrix. In order to improve the compatibility, lignin was efficiently modified by a green esterification reaction under microwave-assisted solvent-free conditions. Comprehensive characterization revealed that modified lignin had fewer inter-unit linkages, increased molecular weights, lower Tg and enhanced hydrophobicity. Moreover, the prepared modified lignin/PBAT composites reinforced with maleic anhydride (MAH) exhibited controllable improvements in mechanical properties and exhibited excellent UV-shielding properties, and their elongation at break, even with 40 wt% lignin, increased by 500% compared to that of unmodified counterparts. The ideal dispersion and compatibility of the modified lignin in the matrix facilitated the mechanical properties of composites, as revealed by morphological and thermal analysis. Importantly, molecular dynamics (MD) simulation unprecedentedly confirmed that the modification of lignin distinctly strengthened molecular interaction and compatibility of the matrices, enhancing the mechanical performance of the composites. This work presents a green and feasible route to produce cost-efficient biodegradable materials with controlled mechanical and UV-shielding properties for packaging application.

Making full use of the lignocellulose is of great significance to the current biorefinery enterprises. As a natural macromolecule polymer, lignin has a prominent potential as renewable feedstock to...

Efficient deconstruction of lignocellulose is vitally important for the biorefinery industry because lignin structures play a crucial role in the high value-added conversion of lignin. In this study, an integrated process based on hydrothermal pretreatment (HTP) and Kraft delignification was proposed to deconstruct lignocellulosic biomass. It was found that the HTP not only facilitated the production of xylo-oligosaccharides but also reduced the chemicals dosage of the following delignification. The structural characteristics of lignin obtained from the integrated process were investigated by NMR spectroscopy and gel-permeation chromatography. Additionally, double enzymatic lignins (DELs) isolated from different feedstocks were used as "model lignin" to delineate the structural transformations of lignin during H2 O2 , ClO2 , and O3 bleaching. Significant changes of the lignin structure were observed during the ClO2 bleaching process, including degradation of aromatic rings, enrichment in p-hydroxyphenyl units, and increase of carboxylic groups. A comparison of the structural characteristics of the bleached lignins indicated that HTP benefited the subsequent bleaching process. Enhanced knowledge of lignin chemistry during deconstruction and delignification could provide valuable insight into the current lignocellulose biorefinery.

In this study, the effect of traditional acidification and hydrothermal acid hydrolysis on the separation of lignin and xylose from the pre-hydrolysis liquor (PHL) of kraft pulping process was comparatively evaluated. The PHL was acidified at room temperature or hydrothermally treated under acidic conditions to isolate lignin and xylose. As compared with the lignin removal rate of 26.8–32.7% by traditional acidification method, a much higher lignin removal rate of 57.1% was achieved by hydrothermal acid hydrolysis. Meanwhile, the content of xylose in the PHL increased dramatically from 7.91 to 13.91–34.82 g/L after the hydrothermal acid hydrolysis. The hydrophilicity of the obtained lignin gradually increased as evidenced by the decrease of the corresponding water contact angel. Additionally, the thermal stability of the lignin sample increased steadily with the increment of acid dosage. The hydrothermal acid hydrolysis provides an effective approach to fractionate lignin and xylose from PHL.

In the present study, lignin from eucalyptus was extracted with 80% alkaline dioxane (0.05 M NaOH) from ball-milled wood and subsequently fractionated by gradient acid precipitation from the filtrate. Meanwhile, the residual lignin was prepared by a double enzymatic hydrolysis process. The yield of the lignin extracted by alkaline dioxane (LA-2) was 29.5%. The carbohydrate contents and molecular weights of the gradient acid precipitated lignin fractions gradually decreased from 4.90 to 1.36% and from 7770 to 5510 g/mol, respectively, with the decline of the pH value from 6 to 2. Results from two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (NMR) and 31P NMR spectroscopy showed an evident reduction of β- O-4 ' linkages with the pH value decrease, while the contents of aliphatic -OH, phenolic -OH, and carboxylic groups displayed an increasing trend. Moreover, the residual lignin exhibited the highest molecular weight (11690 g/mol), the most abundant β- O-4 ' linkages (71.1%), and the highest S/G ratio (4.68).

To understand the structural features and transformations of hybrid Pennisetum (HP) lignin, an integrated treatment on the basis of microwave-assisted hydrothermal pretreatment (MHTP) (at 180–200 °...

Pre-hydrolysis liquor (PHL) from the kraft-based dissolving pulp process contains large amounts of hemicelluloses and their degradation products, which makes it a promising candidate for the production of xylose or xylooligosaccharides (XOS). However, it is usually treated as wastewater of the pulp and paper industries. In this study, both acid hydrolysis and enzymatic hydrolysis were applied to prepare xylose and XOS from the PHL, which contained 47.80 g/L of sugars and 14.10 g/L of lignins. Results showed that an optimal xylose yield (30.10 g/L) was obtained at 120 °C for 0.5 h with 4% aqueous sulfuric acid, while the maximum XOS yield (11.63 g/L) was achieved with 0.3% aqueous sulfuric acid at 120 °C for 2.0 h. For the enzymatic hydrolysis, the highest XOS yield of 15.65 g/L was obtained under the optimal condition (60 IU/L PHL, 50 °C, 6 h), and the XOS were mainly composed of xylobiose and xylotriose.

Herein, the mechanochemical process combined diluted acid impregnation and ball-milling treatment was developed to overcome the recalcitrance of lignocellulose. The high-yield fermentable sugars (glucose and xylose) and impregnated enzymatic lignin (IEL) streams have been simultaneously obtained via mechanochemistry and enzymatic hydrolysis process. It was found that the mechanochemical pretreatment significantly facilitated the enzymatic hydrolysis of the treated substrates, releasing high yield (>90%) of fermentable sugars for further utilization. CP/MAS 13C NMR and solution-state 2D NMR techniques showed that the crystallinity index (CrI) and degree of polymerization (DP) of cellulose in the treated substrates were both decreased. In addition, detailed structural characterizations of the obtained IEL fractions were achieved by the state-of-the-art NMR and GPC techniques. Results showed that the IEL fractions presented similar structural features as compared to the corresponding native lignin (DEL). The study provides an efficient and clean pathway for the conversion of energy from lignocelluloses; meanwhile, the residual lignin with unchanged structures could serve as ideal feedstock for the liquid fuel, bio-based materials, and chemicals in the current biorefinery process.

Xylooligosaccharides (XOS) are useful food and pharmaceutical additives, which can be produced from various xylans. However, the XOS prepared from lignocellulosic materials are difficult to purify due to the complexity of the degradation products. Thus, hemicelluloses with a high-purity will be the preferred feedstock for XOS production. In this work, acid hydrolysis and enzymatic hydrolysis were applied to prepare XOS from the residual hemicelluloses of the dissolving pulp. The results showed that the highest XOS yield (45.18%) obtained from the acid hydrolysis was achieved with 1% sulfuric acid at 120 °C for 60 min, and xylohexaose accounted for 47% of the XOS. For enzymatic hydrolysis, under optimal conditions, the highest XOS yield of 42.96% was observed, and xylobiose and xylotriose comprised 90.5% of the XOS. It is suggested that the distribution of the XOS could be controlled significantly according to the enzymatic or acid hydrolysis conditions used.

Hereon, tobacco stalk was deconstructed by lyophilization, ball-milling, ultrasound-assisted alkali extraction, hydrothermal pretreatment (HTP), and alkali presoaking, respectively, followed by dilute alkali cooking to both improve its enzymatic digestibility and isolate the hemicellulosic streams. It was found that a maximum cellulose saccharification rate of 93.5% was achieved from the integrated substrate by ball-milling and dilute alkali cooking, which was 4.4-fold higher than that from the raw material. Interestingly, in this case, 76.9% of hemicelluloses were simultaneously recovered during the integrated treatment. Structural determination indicated that the hemicelluloses released from tobacco stalk by dilute alkali cooking were mixed polysaccharides, and the (1 → 4)-linked β-D-Xylp backbone branched with L-Araf units at O-2/O-3 and 4-O-Me-α-D-GlcpA units at O-2 of the xylose residues was the main structure. In comparison, ultrasound-assisted alkali extraction, ball-milling, and HTP favored the extraction of hemicelluloses with less branched structure and lower molecular weights in the following alkali cooking.

Pre-hydrolysis liquor (PHL) from the kraft-based dissolving pulp process contains large amounts of hemicelluloses, which is usually treated as an effluent and further efforts have to be involved to eliminate the pollution disposal. However, the hemicelluloses-rich PHL is a promising candidate for the production of carbon microspheres via hydrothermal carbonization. The yield of the carbon microspheres directly derived from the hydrothermal carbonization of the hemicelluloses-rich PHL (22.1%) was almost twice than that from xylose (13.1%). Furthermore, sulfuric acid and the lignin in the PHL could significantly improve the yield and change the size of the carbon microspheres obtained from the PHL. Additionally, the activated carbon microspheres functionalized with acrylic acid showed improved adsorption capacities for Pb(II) ion (273.4 mg/g) and methylene blue (701.3 mg/g). The hydrothermal carbonization of the PHL not only utilizes the hemicelluloses in the PHL, but also reduces the pollution load of the PHL significantly.

The high value utilization of lignin is facing sheer challenge, and the use of lignin as a raw material to prepare flocculants is of tremendous significance for wastewater treatment. In this study, lignin-based flocculants (LBFs) with tunable performances were prepared by mild copolymerization of lignosulfonate and [2-(Methacryloyloxy) ethyl] trimethylammonium chloride solution (METAC) under short-wavelength ultraviolet light. The effect of preparation conditions on the product performances was investigated, and two classes of LBFs were obtained in the same system by adjusting the preparation conditions. As compared with the preparation of LBFs suitable for simulated dye wastewater, higher monomer dose and lower pH were required for the preparation of LBFs suitable for kaolin and E. coli suspensions. Among them, LBF-1 could remove more than 95 % dye, and LBF-2 had 99.2 % and 97.5 % turbidity and bacterial removal rates, respectively. Moreover, the effects of external factors such as the LBF-1 dose, initial concentration of dye and wastewater pH on the decolorization efficiency were also explored. In addition, the sterilization function of LBF was studied, and LBF-2 experienced a process of first flocculation followed by sterilization. Furthermore, the flocculation mechanisms of LBFs in treating three kinds of wastewaters were discussed in detail.

Lignin is a renewable source of aromatics, and the conversion of lignin to chemicals, fuels and materials is very attractive. Herein, a novel lignin-based cation exchange resin (LBR) was easily synthesized through an economical one-pot method. Results demonstrated that the sulfonic acid groups were successfully introduced into the skeleton of the resins, and the S contents and swelling capacity of the prepared LBRs gradually increased with the increment of the sulfonation reagents dosage. A maximum ion-exchange capacity of 2.26 mmol/g was achieved for the LBR obtained at 120 °C for 4 h with a molar ratio of phenol to formaldehyde (P:F) of 1:5 (SSPL-0.50), which was comparable to the commercial phenol type cation exchange resin. Furthermore, the SSPL-0.50 exhibited a high adsorption capacity (167.2 mg/g) for Pb (II) removal. The LBR can be considered as a promising substitute for the petroleum-based ion exchange resin in the purification of wastewater.

Valuable exploration of lignin is one of the feasible strategies for the development of agricultural wastes in bio-refinery. In this study, five integrated treatments combining freeze-drying/alkali pre-impregnation/ultrasound-assisted alkali pretreatment/ball-milling/hydrothermal pretreatment (HTP) with dilute alkali post-treatment were employed to deconstruct tobacco stalk for lignin release. Meanwhile, double enzymatic lignin (DEL) with ultrahigh yield was successfully prepared as “natural lignin” to reveal the structural evolution of alkali lignins (ALs) during the different integrated treatments. Results showed that guaiacyl (G) was the predominant unit in tobacco stalk lignin and no p-coumaric and ferulic acids were found in all lignin preparations. As compared to DEL, ALs with a lower yield and higher purity had smaller molecule fragments, less β-O-4 linkages, and more COOH groups as well as a higher thermal stability. In addition, it was observed that HTP was superior to other four pretreatments to release lignin in subsequent delignification. Accordingly, significant de-polymerization of the lignin mainly manifested as the decrease of molecular weight, cleavage of β-O-4 linkages, and enrichment of S/G ratio occurred as a result of HTP. The structural knowledge of tobacco stalk lignin explored in this study could provide a good theoretical basis for conversion of agricultural wastes to lignin-based green products.