Alkali Lignin Research Articles

Lignin-based Nanofiltration Membrane with High Permeability, Acid-alkali and Chlorine Resistances toward the Removal of Multivalent Salts and Dyes

Abstract A lignin-based nanofiltration membrane was fabricated using aminated lignin and trimesoyl chloride as raw materials by an interfacial polymerization approach. The obtained membrane possesses excellent pure water permeability (31.2 L m−2 h−1 bar−1), high retention rates (>95%) to multivalent salts (EDTA and sodium citrate) and organic dyes (brilliant blue R and congo red), satisfactory acid-alkali and chlorine resistances, and separation-performance stability. It also shows better retention capability and alkaline stability than those of a membrane fabricated with pristine alkali lignin due to the high crosslinking degree.

Fabrication of alkali lignin-based emulsion electrospun nanofibers for the nanoencapsulation of beta-carotene and the enhanced antioxidant property

For the greater utilization of β-carotene in antioxidant material, β-carotene-loaded emulsion stabilized by alkali lignin (AL) was successfully electrospinning with poly (vinyl alcohol) (PVA) (PVA/AL/β-carotene nanofiber). Transmission electron microscopy demonstrated the core-shell structure of nanofiber with the average diameter being 356.31 nm, and 85.7 % of β-carotene was effectively encapsulated into the core section. Fourier transform infrared spectra and differential scanning calorimetry revealed the good compatibility and decreased crystallinity of β-carotene, favoring its stability and solubility, respectively. As expected, the PVA/AL/β-carotene nanofiber exhibited higher antioxidant activity than free β-carotene due to the protection of AL matrix and the special structure of nanofiber, as the DPPH free radical scavenging rate being 90.7 % at 7th day. The sustained release behavior of β-carotene and AL from fiber followed Fickian diffusion model, contributing to the greater protection for fish oil than that of emulsion. Thus, this study provides an approach to develop hydrophobic compounds-loaded emulsion electrospun antioxidant material with controlled release property and enhanced activity.

Hydrogenation of lignin-derived feedstocks and bio-oil using active and stable ruthenium catalyst

Value addition of lignin-derived phenols into high-value chemicals and fuels is highly desirable and beneficial for bio-refineries owing to their broad applications in chemical and polymer industries. Here we present selective hydrogenation of various lignin-derived phenols into cyclohexanol and its derivatives using SiO2-Al2O3 supported stable and reusable Ru nanoparticles (Ru-NC/SiO2-Al2O3) in a green and sustainable manner. The Ru-NC/SiO2-Al2O3 nanocatalyst is prepared by simple impregnation followed by the pyrolysis method. The Ru-NC/SiO2-Al2O3 nanocatalyst shows excellent activity for the hydrogenation of lignin-derived functional phenols, including o, p, m-cresols, catechol, 4-n-propylphenol, diphenyl ether, guaiacol, eugenol, and others. In addition, hemicelluloses-derived furfural and furfuryl alcohol were also transformed into their hydrogenated products. Further, this transformation is also used for the hydrogenation of alkali lignin bio-oil, which is selectively transformed into corresponding cyclohexanol derivatives. HR-TEM, XPS, powder-XRD, N2 adsorption-desorption, and NH3-TPD analyses were used to examine the physicochemical properties of both fresh and spent Ru-NC/SiO2-Al2O3 nanocatalysts. Furthermore, the Ru-NC/SiO2-Al2O3 nanocatalyst is recycled and reused four times with no loss of any catalytic activity.

Functionalized Lignin for Fabrication of FeCoNi Nanoparticles‐Enriched 3D Carbon Hybrid: From Waste to a High‐Performance Oxygen Evolution Reaction Catalyst

AbstractThe application of lignin‐derived carbon materials in energy conversion is hindered by the complex molecular structure and few metal coordination sites of lignin. In this work, a simple oxidation–coordination method was developed for scalable synthesis of a FeCoNi nanoparticles‐modified nitrogen‐doped carbon hybrid (designated as O−FeCo40Ni10−C) with lignin as carbon precursor for oxygen evolution reaction (OER). Specifically, a Fenton reaction‐driven pre‐oxidation process changed the molecular structure of alkali lignin and increased functional groups, which contributes to the efficient incorporation of metal active sites into lignin‐derived carbon materials. Benefiting from abundant active sites, the synergistic effect of CoFe/NiFe compositions and interconnected porous structure, the obtained O−FeCo40Ni10−C exhibited a high OER activity. It only required an overpotential of 280 mV to drive current densities of 10 mA cm−2 in 1 M KOH solution. Moreover, the turnover frequency of O−FeCo40Ni10−C was 0.030 and 0.185 s−1 at the overpotential of 300 and 400 mV, respectively. This work provided an environmentally‐friendly strategy to synthesize lignin‐derived catalyst for OER and expanded the application of lignin in energy conversion filed.

Cooperative catalytic effects between aqueous acidic ionic liquid solutions and polyoxometalate-ionic liquid in the oxidative depolymerization of alkali lignin

The oxidative depolymerization of alkali lignin can be achieved by using Keggin structure polyoxometalate-ionic liquid (POM-IL) as catalyst under aerobic conditions. The effects of catalysts such as [HC4im]3PMo12O40, [HC4im]5PV2Mo10O40, [HC2im]5PV2Mo10O40, and [HC4im]4SiMo12O40 (abbreviated as POM-IL1, POM-IL2, POM-IL3, and POM-IL4, respectively), the acidity of aqueous IL solutions on lignin conversion, and aromatic product distribution were investigated. Under optimized conditions, phenolic products (mainly m (p)-cresol, veratrole, vanillin) had the highest yield and the selectivity was as high as 75.0% using POM-IL1 as the catalyst. POM-IL2 and POM-IL3 were used as the catalysts, the highest conversion of 76.0% of lignin was achieved, and the overall yield of ketone products were higher on lignin samples, in which the main products include acetovanillone, 3-methoxyphenol, and 4-methylcatechol, and the highest selectivity of ketone products was 76.8%. The results show that the lignin fragments could be successfully oxidized into platform compounds in aqueous acidic ILs (AILs) solutions catalyzed by Keggin structure POM-IL. In addition, the role of AILs and POM-ILs in the oxidative depolymerization of alkaline lignin was analyzed, and the possible reaction mechanism between AIL-water/POM-IL/lignin system was speculated.

Genomics analysis and degradation characteristics of lignin by Streptomyces thermocarboxydus strain DF3-3

BackgroundLignocellulose is an important raw material for biomass-to-energy conversion, and it exhibits a complex but inefficient degradation mechanism. Microbial degradation is promising due to its environmental adaptability and biochemical versatility, but the pathways used by microbes for lignin degradation have not been fully studied. Degradation intermediates and complex metabolic pathways require more study.ResultsA novel actinomycete DF3-3, with the potential for lignin degradation, was screened and isolated. After morphological and molecular identification, DF3-3 was determined to be Streptomyces thermocarboxydus. The degradation of alkali lignin reached 31% within 15 days. Manganese peroxidase and laccase demonstrated their greatest activity levels, 1821.66 UL−1 and 1265.58 UL−1, respectively, on the sixth day. The highest lignin peroxidase activity was 480.33 UL−1 on the fourth day. A total of 19 lignin degradation intermediates were identified by gas chromatography–mass spectrometry (GC–MS), including 9 aromatic compounds. Genome sequencing and annotation identified 107 lignin-degrading enzyme-coding genes containing three core enzymatic systems for lignin depolymerization: laccases, peroxidases and manganese peroxidase. In total, 7 lignin metabolic pathways were predicted.ConclusionsStreptomyces thermocarboxydus strain DF3-3 has good lignin degradation ability. Degradation products and genomics analyses of DF3-3 show that it has a relatively complete lignin degradation pathway, including the β-ketoadipate pathway and peripheral reactions, gentisate pathway, anthranilate pathway, homogentisic pathway, and catabolic pathway for resorcinol. Two other pathways, the phenylacetate–CoA pathway and the 2,3-dihydroxyphenylpropionic acid pathway, are predicted based on genome data alone. This study provides the basis for future characterization of potential biotransformation enzyme systems for biomass energy conversion.

Dual-Modified Lignin-Assembled Multilayer Microsphere with Excellent Pb2+ Capture.

With the continuous research on lignin-based sorbents, there are still limitations in the research of spherical sorbents with a high adsorption capacity for Pb2+. In order to solve the problem of low adsorption effect, alkali lignin (AL) was modified and assembled to increase the adsorption active sites. In this work, we used dual-modified lignin (DML) as a raw material to assemble a singular lignin-based multilayer microsphere (LMM) with sodium alginate (SA) and dopamine. The prepared adsorbent had various active functional groups and spherical structures; the specific surface area was 2.14 m2/g and the average pore size was 8.32 nm. The adsorption process followed the Freundlich isotherm and the second-order kinetic model. Therefore, the LMM adsorbed Pb2+ ascribed by the electrostatic attraction and surface complexation; the adsorption capacity was 250 mg/g. The LMM showed a selective adsorption performance for Pb2+ and the adsorption capacity followed the order Pb2+ (187.4 mg/g) > Cu2+(168.0 mg/g) > Mn2+(166.5 mg/g). After three cycles, the removal efficiency of Pb2+ by the LMM was 69.34%, indicating the reproducibility of LMM.

Facile Synthesis of Multi-Emission Nitrogen/Boron Co-Doped Carbon Dots from Lignin for Anti-Counterfeiting Printing.

The transformation of lignin with natural aromatic structure into value-added carbon dots (CDs) achieves a win-win situation for low-cost production of novel nanomaterials and reasonable disposal of biomass waste. However, it remains challenging to produce multi-emission CDs from biomass for advanced applications. Herein, a green and facile approach to preparing multi-emission CDs from alkali lignin via N and B co-doping is developed. The obtained N and B co-doped CDs (NB-CDs) show multi-emission fluorescence centers at 346, 428 and 514 nm under different excitations. As the doping amount of N and B increases, the fluorescence emission band gradually shifts to 428 and 514 nm, while that at 346 nm decreases. The fluorescence mechanism is explored through the research of the structure, composition and optical performance of NB-CDs in combination with density functional theory (DFT) calculations. It demonstrates that the effect of doping with B-containing functional groups on the fluorescence emission behavior is multivariate, which may be the crucial contribution to the unique multi-emission fluorescence of CDs. The multi-emission NB-CDs with prominent stability are applied for multilevel anti-counterfeiting printing. It provides a promising direction for the sustainable and advanced application of biomass-derived CDs, and the theoretical results highlight a new insight into the deep understanding of the multi-emission fluorescence mechanism.

Facile preparation of nitrogen-doped hierarchical porous carbon derived from lignin with KCl for supercapacitors

In this work, a nitrogen-doped lignin-derived hierarchical porous carbon material (LDMCN-700–2) was synthesized by a facile and green strategy using alkali lignin as carbon source, melamine as nitrogen source, and KCl as salt template. The as-prepared LDMCN-700–2 possessed unique structural properties such as a large surface area of 1012.5 m2·g−1, high nitrogen content of 4.5 at%, and hierarchical porous structure with micropores, mesopores and macropores, which endow it with superior electrochemical performance. The electrochemical measurements demonstrated that LDMCN-700 as an electrode material exhibited a high specific capacitance of 245 F·g−1 at 0.5 A·g−1, as well as excellent cycling stability with 95.7 % capacitance retention after 5000th cyclic voltammetry cycles, indicating its great potential for supercapacitors.

Femtosecond Laser One‐Step Direct Writing Electrodes with Ag NPs‐Graphite Carbon Composites for Electrochemical Sensing

AbstractThe next generation of green electronic products will be flexible, eco‐friendly, have arbitrary patterning, and be produced using simple methods. Here, a silver nanoparticles (Ag NPs)–graphite carbon composite‐based electrochemical sensor is patterned on a flexible substrate by one‐step in situ femtosecond (fs) laser fabrication. Alkali lignin is used as a precursor and nontoxic natural reducing agent to reduce aqueous silver nitrate to produce Ag NPs. The fs laser carbonization process converts lignin into graphite carbon electrodes with diverse three‐dimensional (3D) micro/nano morphologies, causing less thermal damage to the Ag NPs and thin substrate. The 3D micro/nano morphologies combined with Ag NPs effectively increase the active surface area, conductivity, and catalytic activity of the electrode, which is further applied as an electrochemical sensor. This sensor has a wide linear detection range of nitrite from 1–4000 × 10−6 m, a detection limit of 0.117 × 10−6 m (S/N = 3), and long lifetime of 30 days. The sensor also has the potential to detect dopamine (DA). A detection limit of 0.098 × 10−6 m (S/N = 3) is obtained, with a linear detection range of 1–45 × 10−6 m. The sensor demonstrates a wide range of applications in food safety and human health‐related detection.

Valorization of bagasse alkali lignin to water-soluble derivatives through chemical modification

Valorization of bagasse alkali lignin to water-soluble derivatives through chemical modification

Fractionation of light-colored lignin via lignin-first strategy and enhancement of cellulose saccharification towards biomass valorization

Highly efficient breaking lignocellulose cell wall recalcitrance towards biomass valorization still remains a great challenge. In this work, we developed a very effective lignin-first strategy using diols for direct fractionation of light-color lignin, and resulting in enhancement of enzymatic saccharification of cellulose-rich residues. The isolated lignin fraction possessed relatively higher content of β-O-4 linkages (26.6%), purity (>99%) and yield (>50%) and its brightness reached 22.0%ISO, which was 15.3, 13.5 and 1.9 folds higher than Kraft lignin, lignosulfonate and alkali lignin, respectively. In addition, the obtained nearly white-color lignin could be efficiently and directionally depolymerized into syringyl type phenols with high yields (82.0% of total phenols). Enzymatic hydrolysis efficiency of cellulose-rich residues was significantly enhanced up to 84.95% due to the more effective adsorption of cellulase under this diols strategy. Overall, the developed lignin-first strategy showed noteworthy preponderance on overcoming cell wall recalcitrance to achieve the whole lignocellulosic components valorization.

Efficient Protection of Silver Nanowire Transparent Electrodes by All-Biorenewable Layer-by-Layer Assembled Thin Films.

An efficient protection strategy for silver nanowire-based transparent electrodes (AgNW TEs) is developed to enhance their poor adhesion force on substrates and thermal, optical, chemical, and electrical stabilities. Chitin nanofibers (CNFs) and alkali lignin (AL), which possess high mechanical property, a gas/moisture barrier, and UV absorption properties, are successively assembled on AgNW TEs through layer-by-layer (LBL) assembly based on their oppositely charged surfaces. The formation of LBL-assembled CNFs and AL (CNF/AL)10 bilayers, where 10 is the optimized number of bilayers, on the aldehyde-modified AgNW (Al-AgNW) TEs does not deteriorate their electrical conductivity (17.3 ± 2.1 Ω/□) and transmittance (90.1 ± 0.3% at 550 nm), and the (CNF/AL)10 bilayer-coated Al-AgNW [(CNF/AL)10@Al-AgNW] TEs present considerable enhancement in their adhesion force and thermal, optical, chemical, and electrical durability. In detail, their optoelectrical properties are stable over 200 cycles of the scotch peel-off test, for 10 h sonication, up to 350 °C, under UV/O3 treatment for 100 min, in 10% HCl and 28% NH3 for 6 and 12 h, and at an electrical potential up to 14 V, respectively. These features make (CNF/AL)10@Al-AgNW TEs suitable as a durable high-performance transparent heater.

Enhanced oxidative depolymerization of lignin in cooperative imidazolium-based ionic liquid binary mixtures

The aerobic oxidation of lignin model 2-phenoxyacetophenone (2-PAP) in cooperative ionic liquid mixtures (CoILs) with 1-ethyl-3-methylimidazolium acetate ([C2C1im]OAc) and 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BZC1im]NTf2) was investigated. Complete degradation of 2-PAP was achieved with [C2C1im]OAc/[BZC1im]NTf2 molar ratio (RIL) of 1/1 and 1/2 at 100 °C for 2 h. The conversion and product yields from CoILs were higher than those in pure ILs, indicating the cooperative effects of [C2C1im]OAc/[BZC1im]NTf2 on cleaving aryl–ether bonds. [C2C1im]OAc promoted the catalytic cleavage of aryl–ether bonds and solvation, and [BZC1im]NTf2 induced the formation of alkyl radicals and enhanced the product selectivity. Accordingly, the highest conversion of alkali lignin (79.8%) was obtained with RIL of 5/1 at 100 °C for 2 h, and phenol monomers (306 mg/g) were selectively produced. The CoILs exhibited good catalytic capacities for oxidative depolymerization of lignin, which strongly depends on the changes in intermolecular interactions and structural organization with varying RIL.

Lignin nanoparticles-intercalated reduced graphene oxide/glass fiber composite membranes for highly efficient oil-in-water emulsions separation in harsh environment

The low water permeability of reduced graphene oxide (RGO) membranes limit their wide applications in water treatment. Herein, a new route to fabricate a lignin nanoparticles-intercalated RGO composite membrane with high flux is reported. The addition of alkali lignin (AL) not only contributed to the reduction of graphene oxide (GO) in the hydrothermal reduction process, but also intercalated between RGO nanosheets. The AL/RGO nanosheets were further cross-linked with polydopamine (PDA) to stabilize the interlayer structure and finally assembled onto a glass fiber (GF) membrane by a vacuum filtration process. The AL/RGO@PDA membrane shows a large pure water flux up to 2410.3 L/m2 h, which increased by 297.3% than that of the RGO composite membrane (810.7 L/m2 h) without nanoparticles intercalated. Even after 10 cycles, the AL/RGO@PDA membrane remained high separation efficiency (above 99.10%) for n-hexadecane emulsion. In addition, such a membrane maintained the original performance at high temperature (98 °C) and in highly corrosive environments (pH=1, pH=14). Overall, this study provides a facile and eco-friendly method to fabricate high flux RGO composite membrane, showing promising application for water purification and separation.

Transparent, Self‐Adhesive, Conductive Organohydrogels with Fast Gelation from Lignin‐Based Self‐Catalytic System for Extreme Environment‐Resistant Triboelectric Nanogenerators

AbstractConductive hydrogels have shown great promise in the field of sustainable power sources due to their unique features of sufficient flexibility, durability, and functional diversification. However, time‐ and energy‐consuming polymerization process and poor adaptability in extreme environments severely impede their practical application in such an emerging field. Herein, a facile and universal self‐catalytic system (AL‐Cu2+) based on alkali lignin (AL) macromolecule has been designed to rapidly fabricate conductive and transparent organohydrogels in alkaline water–ethylene glycol (EG) binary solvent, which displays extreme environment applicability (‒40 to 60 °C), eligible stretchability (≈800% elongation), and robust self‐adhesion (≈31.4 kPa). Interestingly, the introduced EG accelerates the polymerization, endows extreme freezing/drying resistance, and improves self‐adhesion for the organohydrogels. The organohydrogel (water/EG = 2/3) that combines the above merits inspires the construction of triboelectric nanogenerator (O‐TENG) for mechanical energy harvesting and converting regardless of low‐ or high‐temperature environments. The generated electricity by the O‐TENG can be used directly or stored to drive commercial electronics and installed on human joints for movement monitoring. This work sheds light on designing environment‐resistant flexible TENGs based on multifunctional soft materials with fast gelation strategy, provoking more attention to sustainable high‐value utilization of lignin for advanced applications.

Efficient demethylation of lignin for polyphenol production enabled by low-cost bifunctional protic ionic liquid under mild and halogen-free conditions

The utilization of lignin is of high interest since it represents the most abundant polyphenol that has found multiple applications especially in functional material preparation. Demethylation is a promising way to produce polyphenol from lignin but is still challenging owing to the inactive/poorly soluble nature of lignin, and the majority of processing solvents remaining halogenated and high-cost, which stand as critical issues for commercialization. Herein, low-cost bifunctional protic ionic liquids (PILs) were successfully applied for dissolving and demethylating real representative lignin (e.g. enzymatic lignin, alkali lignin, and sodium ligninsulfonate) under mild and halogen-free conditions for the first time. As a probe, acetate anion countered with ethanolamine cation exhibited effectively synergistic activity for enzymatic lignin demethylation with a rate as high as 73%, which is better than most recently reported methods. Systematical characterizations including 2D HSQC NMR provided a comprehensive insight into the structural changes of lignin after treatment in PILs. In the case of ethanolamine acetate, both a significant increase in the Ph-OH group content and significant reductions in the β-O-4 bond and S/G values in the treated lignin were achieved, leading to an increase in the number of activation sites in the lignin macromolecule. In addition, ethanolamine acetate could be easily recovered at least three times with an average recovery rate around 97%, and maintain high lignin recovery and lignin conversion in all the cycles. Overall, this study presents a new, simple, and halogen-free method for lignin demethylation, which opens up a strategy for improving the valorization of lignin.

Catalytic hydrothermal liquefaction of alkali lignin at low temperature: Effect of acid and base catalysts on phenolic monomers production

Catalytic hydrothermal liquefaction of alkali lignin at low temperature: Effect of acid and base catalysts on phenolic monomers production

Preparation of lignin/polyethylene glycol film-forming agent and its application in chlorantraniliprole 5% flowable concentrate for seed coating (FS)

Five Lignin/Polyethylene Glycol (L-PEG) film-forming agents with different lignin contents were prepared using industrial Alkali Lignin (AL) and Polyethylene Glycol (PEG) as the main raw materials. FI-IR and 1H NMR analysis demonstrated the introduction of large amounts of polyethylene chains in lignin molecules. The prepared L-PEGs could be dispersed in water to form a stable nanoemulsion with a particle size of 131–232 nm and a zeta potential of − 27.22~− 38.64 mV. After L-PEGs drying into film, the obtained films can swell rapidly in water, with a swelling rate of 183.3–257.6%. The swollen wet film dissolved slowly in water with a dissolution rate of 42.3–57.1% in 14 days. The 5% flowable concentrate for seed coating (FS) of chlorantraniliprole was prepared by using L-PEG as a film-forming agent. The storage stability at elevated temperature experiment showed that the FS had good storage stability. The coating experiment showed that the FS had good coating performance, with film forming time less than 4 min, coating uniformity higher than 93.3%, and shedding rate lower than 7.67%. The pot experiment showed that the germination percentage of coated maize (Zea mays L.) seeds increased from 86.67% to over 93.33%, which could promote the growth of seedlings.

Biocompatible rapid few-layers-graphene synthesis in aqueous lignin solutions

• Alkali lignin is an effective stabilizer for rapid exfoliation of graphene • Raman data mapping provides insight on the effect of process parameters on graphene • 3-5 layers graphene with low-defectivity is obtained within 3 hours of sonication Ultrasonic-Assisted Liquid Phase Exfoliation (UALPE) is considered one of the most promising approaches for the scale-up of graphene production. The process is based on the isolation and stabilization of layers of 2D materials, such as graphene: the selection of a proper stabilizing/exfoliating agent is crucial to achieve a stable Few-Layers-Graphene (FLG) dispersion. In the present work we propose the use of alkali lignin (AL) as a polymeric stabilizing agent for the rapid (≤ 3 hours) synthesis of FLG. Sonication time and graphite-to-lignin (Gr/AL) ratios were investigated as the primary operational parameters to identify the optimal working conditions. Spectroscopical characterization of the samples were employed to assess the quality of the synthesized material: the analysis of the Raman and XPS spectra provided insight on the number of layers and the nature of the limited defects introduced with the exfoliation procedure. Low-defectivity FLG was obtained at Gr/AL = 8 and a sonication time of 3 hours. Furthermore, Scanning Electron Microscopy and Dynamic Light Scattering were performed to investigate the size of the exfoliated flakes (∼ 400 nm). The procedure proposed represents a rapid route for the synthesis of FLG, which will be further explored for composites in chemiresistive devices.