Lignin In Liquor Research Articles

Highly conductive copper-doped nano biochar derived from black liquor lignin for rubber-based strain and liquid sensors

Highly conductive copper-doped nano biochar derived from black liquor lignin for rubber-based strain and liquid sensors

Hierarchical porous sulfur self-doped lignin carbon derived from full component utilization of black liquor for high-performance supercapacitors

Black liquor, primarily consisting of lignin, polysaccharides, and inorganic substances, is a potential precursor of porous carbon materials for high-performance supercapacitors. However, the laborious purification of black liquor lignin and the introduction of exogenous heteroatoms have hindered their practical applications. Herein, the full components of black liquor were utilized to synthesize hierarchical porous sulfur self-doped lignin carbons (S-LCs) through a self-activation process aimed at improving the performance of supercapacitors. Benefiting from the intensified reactivity and crosslinking degree of the polysaccharide component and the sulfur self-doping and self-activation effect of inorganic substances, the resulting S-LCs exhibit a high specific surface area (SSA), abundant porous structure, and enhanced defect activity, all contributing toward increasing the energy storage capacity of supercapacitors. The as-obtained S-LC-G250/700 features a high SSA of 892.94 m2 g−1 and a sulfur content of 3.3 at.%. The S-LC-G250/700 demonstrates excellent specific capacitance (e.g., 405.06 F g−1 at 0.5 A g−1), remarkable stability (103 % capacity retention after 10,000 cycles), and high energy density of 30.4 Wh kg−1. Density functional theory calculations verified the advantages of the high-content sulfur self-doping of black liquor, suggesting that self-doped sulfur contributes to charge adsorption on porous carbon surfaces and promotes electron transfer in the electrolyte.

Revisiting alkali pretreatment to transform lignocellulose fermentation with integration of bioprocessible lignin

This study emphasized the synergistic production of bioprocessible lignin and carbohydrates during a sequential liquid hot water and alkali pretreatment of lignocellulose, facilitating their subsequent individual fermentation. Increasing the dose of alkaline lignin from 0 to 8 g/L inhibited cell growth in anaerobic digestion, with varying levels of inhibition observed in the following order: hydrolytic bacteria < acidogens < acetogens. Alkali pretreatment was adapted to maximize yields of bioprocessible lignin liquor without compromising utilization of the carbohydrates. Increasing the NaOH dose from 50 to 200 mg/g-feedstock monotonically improved lignin yields, but further increases in alkali loading led to a decline in lignin recovery. Volatile fatty acids production from anaerobic digestion of the carbohydrate moiety consistently increased with higher NaOH doses. The optimal conditions for maximizing lignin yields were determined to be 105 °C for 30 min, with NaOH loading in the range of 150–200 mg/g-feedstock, resulting in approximately 80 % lignin recovery, of which 35 % was biologically utilizable. Liquid hot water treatment prior to alkali pretreatment was confirmed as necessary to preserve carbohydrates of 0.1 g/g-feedstock at a low temperature of 70 °C. These findings are crucial for economically producing bioprocessible lignin without carbohydrate loss, a key step towards achieving full lignocellulose valorization.

Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics

Uncovering the structure of lignin from biorefinery has an important effect on lignin catalytic depolymerization and the production of bioenergy. In this study, two biorefinery lignins were isolated from tobacco stalks via alkaline and deep eutectic solvent (DES) catalyzed delignification processes, and the lignin heterogeneity structural characteristics were elucidated by gel permeation chromatography, 2D-HSQC, FT-IR, etc., to understand the relationship between the structure and the thermal characteristics of lignin. It was found that the lignins presented various structural characteristics and components, in which the predominant interunit linkages of black liquor lignin are β-O-4 and β-β linkages, and the β-O-4 linkages disappeared by DES treatment. DES lignins exhibited lower molecular weights and yields than black liquor lignin. Thermogravimetric analysis and fixed-bed pyrolysis were also performed to investigate the lignin thermal behavior. The results show that the DES approach can improve the bio-oil production from lignin and highlight the potential of DES lignin as a promising feedstock in the lignin pyrolysis process. This work provides a valuable example of the conversion of biorefinery lignin into pyrolysis products.

Flame-retardant performance of a novel lignin-based rigid polyurethane foam prepared from pulping black liquor

To improve the flame retardancy of rigid polyurethane foam (RPUF), black liquor lignin-based rigid polyurethane foam (LRPUF) was prepared in this work through a one-step foaming method using lignin and inorganic salt in black liquor lignin as the structural modifier and the additive flame retardant, respectively. Effect of the addition of carbon dioxide treated black liquor lignin (CBL) on the structure and flame retardancy of LRPUF, as well as the flame flame-retardant mechanism of LRPUF, were investigated. The limiting oxygen index (LOI) test and cone calorimetric tests showed that compared to the RPUF, the LOI of LRPUF with 40 wt% CBL increased from 18.9 % to 21.3 %, and the peak heat release rate, total heat release, and total smoke production decreased by 19.5 %, 25.3 %, and 20.5 %, respectively, indicating that the addition of CBL improved the flame retardancy of LRPUF. The flame-retardant mechanism was investigated by analyzing the structure and components of the char residue. We found that a dense protective layer, consisted of char residue and a considerable amount of sodium sesquicarbonate on the surface of the char residue, was formed after combustion. This study provided a novel strategy for the resource utilization of black liquor lignin.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Bi-functional and bi-metallic catalytic solvo-hydrothermal liquefaction for upgrading hydrocarbon of phenol-rich oil from kraft black liquor lignin

This study primarily aimed to enhance the hydrocarbon of a solvo-hydrothermal liquefaction (S-HTL) process initially extracting phenolic-rich oil. To catalyze the current process, HZSM-5 zeolite with its modifications were applied to S-HTL. Ni2P was first introduced to zeolite forming bifunctional catalyst and further coating it with either Co, Mo, or Zn to create bimetallic catalyst. The analysis showed that the zeolite structure did not change after the modifications. The acid sites on the catalyst were found to be principally responsible for the hydrodeoxygenation upgrading the oil yield, biomass conversion, and hydrocarbon generation. Catalytic HTL also produced compounds not detected in non-catalytic S-HTL which appeared to be largely promoted by the catalyst with Ni2P. Additionally, oil output, biomass conversion, and hydrocarbon yield were all substantially increased by catalyst (supplemented by Mo) about 20 %, 5 %, and 15 %, respectively. Moreover, Mo-supplemented catalyst with pre-treatment could be used for 5 more cycles with insignificant oil conversion reduction. Overall, the study synthesized bi-functional and bi-metallic catalysts and applied it to S-HTL improving the yield of generated oil and increasing hydrocarbon production.

Green recyclable biocomposite prepared from lignin and bamboo

Pursuing green and recyclable biocomposites is crucial to promoting sustainable development and carbon balance in the wood-based panel industry. In this study, bamboo and lignin were used as raw materials to create a high-performance biocomposite with better mechanical properties. The biocomposite demonstrates an impressive flexural strength of 97.20 MPa and a tensile strength of 41.43 MPa. These values represent a remarkable increase of 121% and 133%, respectively, compared to traditional fibreboard. This could be due to the lignin in the black liquor undergoing a glassy state transformation during hot pressing and acting as an adhesive to bind bamboo fibres tightly. As a result, the fibres are interconnected by hydrogen bonds and strong chemical bonds. During the recycling experiment, the Hot-pressed B&B20 underwent crushing and partial mixing with bamboo powder in a 1:3 ratio. Despite undergoing this process three times, its strength remained relatively unchanged, with tensile strength ranging from 89.53 to 98.32 MPa and static bending strength ranging from 38.79 to 40.52 MPa. Furthermore, the Hot-pressed B&B20 exhibits excellent machinability, hydrophobicity, heat resistance, and environmental friendliness, which makes it a highly competitive product.

Preparation of activated carbon from paper black liquor lignin as high-performance electrode material

Preparation of activated carbon from paper black liquor lignin as high-performance electrode material

Preparation and characterization of lignin-based epoxy resin via one-step grafting of lignin with E-44 epoxy resin

Aiming for high-value utilization of lignin in pulping black liquor, lignin-based epoxy resin (RLEP) was synthesized by one-step grafting of refined lignin (RL) with E-44 epoxy resin, and then the lignin-based epoxy resin film (RLEPF) was prepared by using phenolic amine as the curing agent. The results showed that the lignin ethers were synthesized by copolymerizing the hydroxyl groups of lignin and the epoxy groups of E-44. Upon increasing the lignin dosage, the epoxy value of RLEP decreased, and the fracture surface of RLEPF changed from a clear-layered structure to an uneven rough surface. Furthermore, the increased lignin dosage resulted in enhancing the elongation at break of RLEPF while the tensile strength and thermal stability were decreased. Compared with the pure E-44 epoxy resin film, the elongation at break of the RLEPF-25 sample significantly improved from 10.61% to 136.51%. Therefore, the lignin-based epoxy resin film prepared by grafting refined lignin with E-44 exhibited excellent toughness. This novel study thus highlights pathways for the resource utilization of the pulping black liquor lignin.

Preparation and characterization of black liquor lignin-based epoxy composite film

To fully utilize black liquor from pulping and decrease its contribution to pollution, lignin-based epoxy resin composite films were prepared from black liquor lignin. Fourier transform infrared spectroscopy indicated the successful synthesis of lignin-based phenolic amine (LPAA). Using LPAA as a curing agent, the prepared epoxy resin films (LPAAF) presented good dispersion of the inorganic chemicals of black liquor and exhibited higher tensile strength of 30 MPa and thermal stability than that using the phenolic amine as a curing agent. Therefore, LPAAF prepared from black liquor lignin presents a novel utilization of black liquor.

Preparation of lignin–MgAl layered double hydroxide composites by hydrothermal method using lignin as carrier and intercalation modifier agent

To improve the dispersion and crystallization of layered double hydroxides (LDHs), black liquor lignin was used as both the carrier and the intercalation modifier agent to prepare lignin–MgAl layered double hydroxide (Lignin-LDH) composites by a hydrothermal method. Fourier-transform infrared spectroscopy showed that the amount of NO3− inserted into the LDH interlayers decreased significantly with the increase of the lignin content. X-ray diffraction revealed that the crystallization of LDH in the Lignin-LDH composites was enhanced by the hydrothermal treatment, and the crystal structure of the LDH was more disordered with the increase of the lignin content. Thermogravimetric analysis showed that hydrothermal treatment and the addition of lignin were beneficial for enhancing the thermal stability of the Lignin-LDH composites. The basal spacing of the LDH was unchanged based on Bragg equation calculations. Based on the infrared and thermogravimetric analysis results, it can be inferred that the molecules of dissolved hydroxyl compounds were inserted into the LDH interlayers. Scanning electron microscopy showed that the hydrothermal treatment promoted the growth of LDH crystals, and the increase of the lignin amount resulted in the dispersion of LDH in lignin and a decrease of the LDH thickness.

Preparation of porous carbon materials from black liquor lignin and its utilization as CO2 adsorbents

Lignin-based porous carbon materials are estimated as promising CO2 capture adsorbents with thanks to their charateristics as abundant distribution, low-cost preparation and high stability. In this work, a series of porous carbon materials were synthesized from the pulping waste (black liquor lignin) through chemical activation and template method. The morphological structure, porosity and surface chemical properties of the obtained porous carbon materials identified by SEM, XRD, Raman, BET and XPS were highly influenced by the synthesis methods. The porous carbon material prepared by KOH activation (C-BLL-KOH) possessed the most disorder carbon structure, along with the largest BET surface area up to 1336.5 m2/g and the highest microporosity accounting for 93.2% of the total pore volume, which is beneficial for capturing CO2. The sulfur-contained functional groups in chemically-activated carbon materials were dominated by oxidized sulfur species and oxygen element was mainly in the form of hydroxyl groups. CO2 adsorption performance of these lignin-based porous carbon materials was carried out at different temperatures (0 °C, 25 °C and 50 °C) to investigate the effect of synthesis method. The most remarkable CO2 capture capacity was achieved for C-BLL-KOH, which was up to 5.20 mmol/g at 0 °C, 3.60 mmol/g at 25 °C and 2.23 mmol/g at 50 °C at a CO2 partial pressure of 100 kPa. This result suggested the KOH activation was an effective route to convert black liquor lignin to porous carbon materials as potential absorbents for CO2 capture.

A green dual-phase carbon-silica nanohybrid derived from black liquor lignin for reinforcing styrene-butadiene rubber

In rubber industry, lignin has been investigated as a potential alternative of fossil-derived carbon black (CB) for several decades. However, due to poor dispersity, big particle size and incompatibility with rubber, lignin cannot achieve the same reinforcing effect as CB by direct dry mixing. Here, a new and green dual-phase carbon-silica nanohybrid (LDPCS) was successfully prepared from black liquor lignin (BLL) and sodium silicate through a simple co-gelation/self-assembly and carbonization process. The preparation mechanism and process as well as the morphology and properties of LDPCS were investigated and discussed in detail. The results indicated that the hydroxymethylation and silane modification of BLL could improve its affinity with SiO2 sols, thus facilitating the co-gelation of BLL and SiO2 sols to inhibit the growth of SiO2 particles. During subsequent acid precipitation, silane modified hydroxymethylated BLL (SiHM-BLL) was self-assembled around SiO2 particles to form nanosized SiHM-BLL-SiO2 hybrids. After carbonization, SiHM-BLL-SiO2 nanohybrids were converted into LDPCS with small primary particle size of 60–90 nm, high specific surface area of 82.19 m2/g, relatively loose secondary aggregation structure and graphitic microcrystals in the carbon framework. With incorporating LDPCS into styrene-butadiene rubber (SBR) by direct dry mixing, LDPCS showed a superior reinforcing capability for SBR as compared with CB, which was ascribed to the nanoscale dispersion of LDPCS, robust C/SiO2 interfaces and high affinity with SBR matrix. This work provided a new insight into the fabrication of novel hybrid nanofiller from lignin and broadened the potential applications of lignin in rubber compounds and beyond.

High-value utilization of bamboo pulp black liquor lignin: Preparation of silicon-carbide derived materials and its application

The black liquor of bamboo pulp contains a large amount of silicon, which makes it difficult to separate industrial lignin, thus hindering its high-value utilization. Herein, this paper dedicates to exploring the high-value use of silica-containing lignin. Tetraethyl silicate (TEOS) was added to the above silicon-containing lignin for crosslinking with the lignin to prevent disintegration during carbonization and provide an additional source of silica. The carbonization is carried out at 600 °C (LT-6), 900 °C (LT-9) and 1200 °C (LT-12), and the structural evolution of SiOxCy is innovatively analyzed. The results show that LT-9 is dominated by the SiO3C structure and has a specific surface area of 269 m2 g−1. The specific capacitance of LT-9 and LT-12 as supercapacitors electrodes is 78.6 F g−1 and 74.8 F g−1 at a current density of 1 A g−1, and remains 95 % and 91.7 % after 10,000 cycles. Moreover, LT-9 has a high yield of 54 %. In this work, silicon-containing lignin is exploratively prepared as a silicon-carbide-derived material. Furthermore, the potential relationship between different SiOxCy molecular structures and electrochemical performance is evaluated, which is instructive for the high-value utilization of black liquor in bamboo pulp.

Morphology of lignin structures on fiber surfaces after organosolv pretreatment.

The redeposition of lignin to the fiber surface after organosolv pretreatment was studied using two different reactor types. Results from the conventional autoclave reactor suggest that redeposition occurs during the cooling down stage. Redeposited particles appeared to be spherical in shape. The size and population density of the particles depends on the concentration of organosolv lignin in the cooking liquor, which is consistent with the hypothesis that reprecipitation of lignin occurs when the system is cooled down. The use of a displacement reactor showed that displacing the spent cooking liquor with fresh cooking liquor helps in reducing the redeposition and the inclusion of a washing stage with fresh cooking liquor reduced the reprecipitation of lignin, particularly on the outer fiber surfaces. Redeposition of lignin was still observed on regions that were less accessible to washing liquid, such as fiber lumens, suggesting that complete prevention of redeposition was not achieved.

Synthesis of magnetic activated carbons from black liquor lignin and Fenton sludge in a one-step pyrolysis for methylene blue adsorption

Black liquor lignin and Fenton sludge were used to prepare magnetic activated carbons (MACs) by one-step pyrolysis using KOH as an effective activator. Brunauer-Emmett-Teller (BET) analysis showed that the addition of Fenton sludge increased the mesopore volume of MACs compared with the control AC, and the addition of KOH not only improved the porosity but also enhanced the formation of high ferromagnetic particles (α-Fe). X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analysis revealed that the iron-based materials in the MACs were Fe3O4 and α-Fe nanoparticles, indicating good magnetic properties. The textural properties and the magnetic properties of the MACs can be modified by controlling the Fenton sludge/lignin ratio. The adsorption process of MAC0.5–2 (mFenton sludge: mlignin: mKOH=0.5:1:2) and MAC1–2 (mFenton sludge: mlignin: mKOH=1:1:2) were investigated. The two MACs exhibited good adsorption capacity (qMAC0.5−2= 307.2 mg g−1 and qMAC1−2= 184.1 mg g−1) for methylene blue (MB) dye. The adsorption kinetics of MB dye onto two MACs followed the pseudo-second order model and the equilibrium data was fitted best with the Sips isotherm model. The thermodynamic study revealed that the adsorption process was endothermic and spontaneous in nature. The recovery efficiency of MAC0.5–2 and MAC1–2 remained 84.0% and 92.1% respectively after five-cycle adsorption-desorption. The synthesized MACs with high magnetic separation efficiency, good recovery ability, and high adsorption efficiency can be promising and effective adsorbents for MB dye or other dyes.

Evaluation of bacterial hosts for conversion of lignin-derived p-coumaric acid to 4-vinylphenol

Hydroxycinnamic acids such as p-coumaric acid (CA) are chemically linked to lignin in grassy biomass with fairly labile ester bonds and therefore represent a straightforward opportunity to extract and valorize lignin components. In this work, we investigated the enzymatic conversion of CA extracted from lignocellulose to 4-vinylphenol (4VP) by expressing a microbial phenolic acid decarboxylase in Corynebacterium glutamicum, Escherichia coli, and Bacillus subtilis. The performance of the recombinant strains was evaluated in response to the substrate concentration in rich medium or a lignin liquor and the addition of an organic overlay to perform a continuous product extraction in batch cultures. We found that using undecanol as an overlay enhanced the 4VP titers under high substrate concentrations, while extracting > 97% of the product from the aqueous phase. C. glutamicum showed the highest tolerance to CA and resulted in the accumulation of up to 187 g/L of 4VP from pure CA in the overlay with a 90% yield when using rich media, or 17 g/L of 4VP with a 73% yield from CA extracted from lignin. These results indicate that C. glutamicum is a suitable host for the high-level production of 4VP and that further bioprocess engineering strategies should be explored to optimize the production, extraction, and purification of 4VP from lignin with this organism.

Industrial lignins: the potential for efficient removal of Cr(VI) from wastewater.

Cr(VI), a serious threat to human health, widely exists in the effluents of various industrial processes. In this paper, the potential of industrial lignin for efficient removal of Cr(VI) from wastewater was systematically investigated, including pulping black liquor lignin (BLN), enzymolysis lignin (ELN), and SPORL pretreatment spent liquor (FS). The structure characterizations of three lignins were investigated by thermogravimetry (TG), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurement, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). Among these three lignins, BLN showed the highest adsorption amount of Cr(VI) and good selectivity in wastewater simulation. According to the Langmuir model, the calculated maximum adsorption amount of Cr(VI) on ELN, BLN, and FS was 801.57, 864.30, and 642.26 mg g-1, respectively. The adsorption of Cr(VI) by industrial lignins was a chemisorption process, during which Cr(VI) was reduced to low-toxic Cr(III). This paper provided a promising application for the effective utilization of industrial lignins.

Magnetic composite Ca(OH)2/Fe3O4 for highly efficient flocculation in papermaking black liquor without pH neutralization

Industrially, lignin in pulp liquor not only obstructed the realization of value-added products, but also threatened the aquatic ecosystem. A magnetic composite Ca(OH)2/Fe3O4, combining the eco-friendliness of Ca-based flocculants with the convenience of magnetic flocculation, was simply compounded to efficiently flocculate lignin from papermaking black liquor. Morphologic and structural features of the flocculant before and after flocculation were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The flocculant Ca(OH)2/Fe3O4 presented mesoporous and core-shell structure, which acted directly in the sodium lignin aqueous solution without pH neutralization, maintaining high lignin removal between 91% and 95%. Ca(OH)2/Fe3O4 showed a wider salts (0–1 mol/L NaCl) and pH (9–12.5) tolerance. In actual pulp black liquor, Ca(OH)2/Fe3O4 exhibited high removal of 90.16% and 85.93% for lignin and chemical oxygen demand (COD), respectively. The flocculation performance of Ca(OH)2/Fe3O4 outdistanced that of the traditional flocculant polyacrylamide (PAM). It displayed magnetically separable with a good reusability. The removal of lignin could attain 90.54% even after 6 cycles. Charge neutralization, micro-bridging, destabilization and sedimentation were involved in the process of lignin flocculation. Consequently, Ca(OH)2/Fe3O4 presented huge potential in papermaking black liquor treatment.