Combination Of Lignin Research Articles

Influence of char‐forming lignin in combination with aluminium phosphinate on thermal stability and combustion properties of polyamide 11 blends

AbstractPolyamide 11 (PA) blends based on char‐forming industrial lignin and aluminum phosphinate (AlP) were prepared to improve flame retardant (FR) properties using a green and eco‐friendly approach. This study investigates the thermal degradation and combustion behavior of PA blends prepared by using AlP in combination with two different types of industrial lignins (i.e., kraft lignin (DL) and lignosulphonate lignin (LL). Thermogravimetric (TG) analysis showed that ternary blends containing LL and AlP developed higher char residue up to 10.7 wt% upon decomposition in inert atmospheres. The combination of lignin and AlP increases the thermal stability by shifting the initial decomposition temperature (T5%) and temperature at maximum decomposition (Tmax) to a higher temperature range, attributed to the stabilization of decomposition products. Furthermore, combustion behavior studied by cone calorimeter (forced combustion) and pyrolysis combustion flow calorimeter (PCFC) tests presented a significant reduction in the peak of heat release rate (PHRR) and total heat release (THR). It was found that LL and AlP‐containing blends more effectively decreased fire parameters like PHRR and THR than that of DL and AlP‐containing blends. The best interaction with reduced fire‐retardant properties was obtained when 10 wt% loading of lignin (DL/LL) and AlP was used. The reduction in heat release parameters was mainly ascribed to the condensed phase mechanism by forming an efficient protective char layer, which acts as a barrier against heat and mass transfer between the condensed and the gas phases. Raman spectroscopy analysis also confirmed the formation of the protective graphitic layer in the condensed phase.

Polylactic Acid/Lignin Composites: A Review

With the gradual depletion of petroleum resources and the increasing global awareness of environmental protection, biodegradable plastics are receiving more and more attention as a green substitute for traditional petroleum-based plastics. Poly (lactic acid) is considered to be the most promising biodegradable material because of its excellent biodegradability, biocompatibility, and good processability. However, the brittleness and high cost limit its application in more fields. Lignin, as the second largest renewable biopolymer in nature after cellulose, is not only rich in reserves and low in cost, but it also has an excellent UV barrier, antioxidant activity, and rigidity. The molecular structure of lignin contains a large number of functional groups, which are easy to endow with new functions by chemical modification. Currently, lignin is mostly treated as waste in industry, and the value-added utilization is insufficient. The combination of lignin and poly (lactic acid) can on the one hand solve the problems of the high cost of PLA and less efficient utilization of lignin; on the other hand, the utilization of lignocellulosic biomass in compounding with biodegradable synthetic polymers is expected to afford high-performance wholly green polymer composites. This mini-review summarizes the latest research achievements of poly (lactic acid)/lignin composites. Emphasis was put on the influence of lignin on the mechanical properties of its composite with poly (lactic acid), as well as the compatibility of the two components. Future research on these green composites is also prospected.

Practical approach of As(V) adsorption by fabricating biochar with low basicity from FeCl3 and lignin

One of the main challenges of biochar application for environmental cleanup is rise of pH in water or soil due to high ash and alkali metal contents in the biochar. While this intrinsic property of biochar is advantageous in alleviating soil and water acidity, it severely impairs the affinity of biochar toward anionic contaminants such as arsenic. This study explored a technical approach that can reduce the basicity of lignin-based biochar by utilizing FeCl3 during production of biochar. Three types of biochar were produced by co-pyrolyzing feedstock composed of different combinations of lignin, red mud (RM), and FeCl3, and the produced biochar samples were applied to adsorption of As(V). The biochar samples commonly possessed porous carbon structure embedded with magnetite (Fe3O4) particles. The addition of FeCl3 in the pyrolysis feedstock had a notable effect on reducing basicity of the biochar to yield significantly lower solution pH values than the biochar produced without FeCl3 addition. The extent of As(V) removal was also closely related to the final solution pH and the greatest As(V) removal (>77.6%) was observed for the biochar produced from co-pyrolysis of lignin, RM, and FeCl3. The results of adsorption kinetics and isotherm experiments, along with x-ray spectroscopy (XPS), strongly suggested adsorption of As(V) occurred via specific chemical reaction (chemisorption) between As(V) and Fe–O functional groups on magnetite. Thus, the overall results suggest the use of FeCl3 is a feasible practical approach to control the intrinsic pH of biochar and impart additional functionality that enables effective treatment of As(V).

Wood-based 3D printing: potential and limitation to 3D print building elements with cellulose & lignin

Under urgent sustainability targets, the building industry craves for renewable and recyclable biomaterials as cellulose is a fiber; Lignin is a plant-derived low-cost polymer with remarkable properties, yet its valorization is in its infancy. Recent studies have shown potentials to combine cellulose and lignin into a renewable bio-based material for the built environment, with the use of additive manufacturing to allow geometric customization and local control of material. However, previous studies also highlighted crucial issues to be solved. One main challenge is the lack of knowledge on combinations of lignin and cellulose with different binders to achieve a paste suitable for 3D printing, leading to a material applicable in the built environment. To contribute overcoming the challenge, this research aimed to explore various combinations of cellulose, lignin, and binders and to study the extrudability of the resulting paste using a clay extruder installed on a robotic arm. Several combinations were explored, evaluated, and compared. The four recipes with the highest scores were used to produce samples for tensile and three-point bending tests, water absorption and retention tests, and microscope analysis. The overall outcome has shown similarities between the mechanical properties of the mixture developed using methylcellulose as the binding agent and rigid polymer foams, such as the ones commonly used as insulation panels. Moreover, the material mix with the highest score in the preliminary assessment was further applied to fabricate samples with varied geometries to assess its potential and limitations combined with the fabrication process. Finally, two demonstrators were produced to explore the printing process for different geometric configurations: conceptual window frame and structural node were designed, and 3D printed as proof of concept.

Selective Photocatalytic Transformation of Lignin to Aromatic Chemicals by Crystalline Carbon Nitride in Water–Acetonitrile Solutions

The photocatalytic conversion of lignin to aromatic compounds in aqueous solutions is a promising approach. We herein report a crystalline carbon nitride prepared by high-temperature thermal polymerization and alkali-metal molten salt treatment, which was then applied in the selective conversion of lignin to aromatic compounds. The results showed that the tri-s-tri-C3N4 presented a relatively high activity and selectivity for the conversion of lignin in aqueous solutions. In a 95% water-acetonitrile solution, it achieved a relatively high conversation rate of lignin, reaching 62.00%, and the selectivity of the C-C bond cleavage was high, at 86.8%. The characterization results obtained by TEM, UV-vis/DRS, PL, and transient photocurrent response showed that the ultra-high activity of tri-s-tri-C3N4 was mainly due to the improvements in crystallinity and light absorption. Mechanism studies showed that the dispersion of the catalyst and the combination of lignin and catalyst in aqueous solvents with different acetonitrile ratios were the main factors affecting lignin conversion. As the water content in the solutions increased, the primary active sites were converted from h+ to ·O2-. This study revealed the interactions between lignin, photocatalysts, and reaction solutions, providing a theoretical basis for the photocatalytic conversion of lignin in aqueous solutions.

Comparative study on the synergistic reinforcement of lignin between carbon black/lignin and silica/lignin hybrid filled natural rubber composites

When the content of carbon black (CB)/silica is constant, the combination of lignin and CB/silica offers obvious advantages over previously reported partial replacement of carbon black/silica by lignin. Considering the distinction between CB/lignin and silica/lignin interactions, the effects of lignin concentration on the vulcanization behavior, crosslink density, filler dispersion, and physical and mechanical properties of the NR composites were investigated. The results showed that the incorporated lignin extended the scorch time (ts1) and optimum vulcanization time (tc90) of the sulfur-cured NR/CB/lignin compounds. The addition of lignin was beneficial for reducing the networking of CB. Although the moduli at 100% and 300% elongation decreased, the NR/CB/lignin composites still exhibited good tensile strength and elongation at break, especially with the addition of lignin at less than 30 phr. For the silica-filled NR composites, the extent of vulcanization of the NR/silica/lignin compounds slightly increased, and the vulcanization rate showed little change. The introduction of lignin plays a significant role in the reinforcement effect of silica-filled NR composites. The strengthened interaction between silica/lignin and NR and the improved filler dispersion significantly contributed to improved reinforcement. However, severe filler networking was observed when the lignin concentration was too high (up to 50 phr), resulting in decreased tensile strength. It is worth mentioning that due to significant reinforcement and the little changes in the hardness of the silica-filled NR vulcanizates by the addition of lignin, the combination of lignin and silica becomes more practical and potential for the formulation optimization of industrial rubber products.

Methane production of banana plant: Yield, kinetics and prediction models influenced by morphological parts, cultivars and ripening stages

Banana trees and fruits with three ripening stages, including green, ripe, and overripe, of two cultivars, namely Nam wa and Hom were separated into different morphological parts for biogas yield determination. Specific methane yields (SMY) were significant different among banana parts (p ≤ 0.05). High non-structural carbohydrates and high non-lignocellulosic residual in substrates promoted high SMY. Pseudostem showed the highest share of energy yields among farm wastes which Nam wa cultivar provided higher energy potential than Hom. Peel presented the major energy source from fruit wastes which ripening stages did not have a significant effect on its SMY. Modified Gompertz model presented the best fit for methane production of most substrates. The SMY prediction models based on chemical constituents were developed to obtain conveniently used methane estimating tool which showed that a combination of lignin, hemicellulose, non-lignocellulosic residual, and crude fiber contents presented the highest performance for banana substrates.

Improved Fire Retardancy of Cellulose Fibres via Deposition of Nitrogen-Modified Biopolyphenols.

Driven by concerns over the health and environmental impacts of currently used fire retardants (FRs), recent years have seen strong demand for alternative safer and sustainable bio-based FRs. In this paper, we evaluated the potential of nitrogen-modified biopolyphenols as FRs for cellulosic natural fibres that could be used in low-density cellulose insulations. We describe the preparation and characterisation of nitrogen-modified lignin and tannin containing over 10% nitrogen as well as the treatment of cellulose pulp fibres with combinations of lignin or tannin and adsorption-enhancing retention aids. Combining lignin or tannin with a mixture of commercial bio-based flocculant (cationised tannin) and anionic retention chemical allowed for a nearly fourfold increase in lignin adsorption onto cellulosic pulp. The nitrogen-modified biopolyphenols showed significant improvement in heat release parameters in micro-scale combustion calorimetry (MCC) testing compared with their unmodified counterparts. Moreover, the adsorption of nitrogen-modified lignin or tannin onto cellulose fibres decreased the maximum heat release rate and total heat release compared with cellulose reference by 15–23%. A further positive finding was that the temperature at the peak heat release rate did not change. These results show the potential of nitrogen-modified biopolyphenols to improve fire-retarding properties of cellulosic products.

Three-component polypropylene/lignin/flax composites with high natural additive content for structural applications

Hybrid composites were prepared from a polypropylene reactor blend (rPP), lignin and flax fibers. Interfacial adhesion was improved using a functionalized PP (maleated PP, MAPP) coupling agent. Composition changed in a wide range; flax content varied between 0 and 30, while lignin content between 0 and 50 vol% in 10 vol% steps. The components were homogenized in a twin-screw compounder, and injection molded specimens were prepared from the compounds for further testing. The processability of the composites was characterized by the measurement of melt flow rate, while mechanical properties by tensile and impact testing. The combination of lignin and flax fibers yields materials with an advantageous property profile, considerably decreased carbon footprint and acceptable price. The application of flax compensates for the deteriorating effect of lignin on deformability and especially on impact resistance. Significant improvement was achieved in stiffness and strength. In order to obtain this property combination, the application of a coupling agent is necessary because of the poor interaction between PP and natural reinforcements. The compounds developed may successfully compete with materials offered on the market.

Pyrolysis Kinetics of a Lignin-Modified Cellulose Composite Film.

Cellulose is the most abundant natural biopolymer material, which has been widely used in film making and food packaging in recent years. However, lignin, a natural bioaromatic material, is always applied as a waste resource due to its low utilization efficiency. In this study, a ZnCl2/CaCl2/cellulose mixed system was used to prepare film materials via a regeneration method. The chemical structure and corresponding properties were characterized. The thermal decomposition process of film materials showed that with an increase of the heating rate, the maximum weight loss temperature gradually shifted to the higher-temperature region. Additionally, the combination of lignin with cellulose as composite films can effectively improve thermal stability. Furthermore, kinetics methods such as Kissing–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman were used to calculate the average activation energy (E). This study proposed a facile method for preparing biobased multifunctional composite films using two kinds of naturally renewable materials.

Development of ultra-high build self-healing coatings using amino silanized lignin nanocapsules

Self-healing coatings were prepared for corrosion inhibition of mild steel by amino Silanization of lignin nano capsules. In-situ polymerization techniques through sonochemical approach was used for preparation of lignin nano capsules. Coatings have been developed using natural healing materials such as combination of lignin and safflower oil and coupling agents i.e APTES in water borne epoxy curing agent. Successful encapsulation of lignin and safflower oil was carried out via in-situ polymerization with the aid of urea–formaldehyde pre-polymer solution in presence of surfactant polyvinyl alcohol (PVA). Further Functionalization of lignin nanocapsules was done by amino Silanization. TEM and FE-SEM images confirm the encapsulation of nano particles and its histogram gives the average particle size distribution of the lignin nano particle and Capsuleas 106 and 146 nm. Total phenolic content of lignin extract were found to be 936 mg GAE/g. Potentio dynamic polarization studies revealed that the current density decreases to minimum of 3.703E-8A/cm2 with increase in weight percentage of lignin in nanocapsules (1.5 wt%) . Electrochemical Impedance spectroscopy showed a maximum impedance value as 6.44E6 for 1.5 wt% LNC coatings. Immersion studies give better corrosion rate for 1.5 wt% LNC coatings when compared to bare and standard coatings.

Making Agriculture More Sustainable: An Environmentally Friendly Approach to the Synthesis of Lignin@Cu Pesticides

Despite its high chemical value, most of lignin is nowadays burnt as low value fuel. It is therefore important to find innovative applications for its use. Copper compounds are used as plant protection products for more than 50 different diseases in viticulture, arable crops, hops, and horticulture, and they have been used for more than 100 years. Minimization of copper in agriculture has become a fundamental issue due to its negative environmental impact. Here we present a series of hybrid organic–inorganic materials (lignin@Cu), deriving from the combination of lignin with brochantite, Cu4(OH)6SO4. Optimization of the synthetic procedures has allowed us to isolate lignin-based materials containing different percentages of copper, where the brochantite crystals are featured by different morphologies and dimensions. A more environmentally safe synthesis of lignin@Cu materials by mechanochemistry is also investigated, which reduces the amount of water used and makes easier and faster the isolation of the final materials. Tests on strawberry and tomato plants in a greenhouse have highlighted a significative efficacy of the lignin@Cu materials against different pathogens at a copper content much lower than the one of copper-based commercial pesticides. A crystal morphology–activity correlation is also traced out. The synergic activity of lignin and copper ions can be used to reduce the copper content for efficient pathogen control. Moreover, the mechanochemical approach ensures a greener synthetic approach, in a perspective of a more sustainable agriculture.

Assessment of lignin as a carbon source in intumescent coatings containing polyaniline

Lignin, a vegetable compound, is the second most abundant biorenewable and biodegradable polymer in nature. In this study, the addition of this compound to paints containing ammonium polyphosphate (APP) and expandable graphite as pigments was investigated to improve the fire protection performance of intumescent coatings. The combination of lignin with polyaniline (PANI) in the formulations was also evaluated, as previous studies have shown that PANI-based paints show promising results in intumescent coatings. For this purpose, the thermal protection of mild steel samples coated with these organic coatings was evaluated during a fire resistance test, with the sample exposed to a Bunsen torch. During the test, temperature data and thermography images for the steel surface were collected. The coatings were also evaluated by thermogravimetric analysis and microscale combustion calorimetry. It was found that all coatings formulated provided good fire protection to the steel substrate and the lignin could be a good option to replace nonrenewable sources in intumescent paints, since the sample coated with the paint containing 10 wt% lignin reached 230°C after 30 min of assay. In addition, when this compound was used in combination with PANI, the flame protection was even better. The best performance was observed for the paint formulated with combination of 10 wt% lignin and 10 wt% PANI-ES, whose metal substrate temperature was 170°C after 30 min of assay.

Lignin-Inorganic Interfaces: Chemistry and Applications from Adsorbents to Catalysts and Energy Storage Materials.

Lignin is one the most fascinating natural polymers due to its complex aromatic‐aliphatic structure. Phenolic hydroxyl and carboxyl groups along with other functional groups provide technical lignins with reactivity and amphiphilic character. Many different lignins have been used as functional agents to facilitate the synthesis and stabilization of inorganic materials. Herein, the use of lignin in the synthesis and chemistry of inorganic materials in selected applications with relevance to sustainable energy and environmental fields is reviewed. In essence, the combination of lignin and inorganic materials creates an interface between soft and hard materials. In many cases it is either this interface or the external lignin surface that provides functionality to the hybrid and composite materials. This Minireview closes with an overview on future directions for this research field that bridges inorganic and lignin materials for a more sustainable future.

Label-free visualization of lignin deposition in loquats using complementary stimulated and spontaneous Raman microscopy

The lignification triggered by biotic or abiotic stresses hardens fruits and vegetables and eventually influences their consumer appeal. Extensive prior efforts have been made to unveil the underlying mechanism of flesh lignification, primarily focused on its physicochemical and molecular biological properties. Nevertheless, most of these studies used destroyed and homogenized bulk tissues as analytes; as a result, potentially valuable spatial information was lost. In this study, the deposition of lignin in loquat flesh during lignification was visualized from the tissue level to the single-cell level by combining the advantages of stimulated Raman scattering (SRS) and spontaneous Raman microscopy using label-free in situ molecular imaging. SRS has the advantages of being fast and providing large-area chemical imaging to reveal the spatial heterogeneity of lignin and cell wall polysaccharide distribution in loquat flesh. After 2 days of storage at 0 °C, increased lignins were observed by large-area SRS imaging. In addition, microscopic SRS images of the flesh cells indicated that the increased lignins were trapped in the cell corner (CC) and middle lamella (ML). Furthermore, the compositional and structural features of lignified cells (LCs), CC and ML of loquat flesh were investigated by spontaneous Raman microscopy, and the results showed that the LCs were a combination of lignin, cellulose, and hemicellulose, whereas CC and ML showed only deposited lignin and pectin without cross-linked cellulose and hemicellulose. This result further suggests that the lignins in the CC and ML regions of loquats were later synthesized alone during postharvest storage. This innovative combination of SRS and spontaneous Raman microscopy allows the label-free macroscale and fine chemical imaging of plant cell walls and will enhance our fundamental understanding of the structures and functions of the plant cell wall.

Synergistic flame-retardant effect between lignin and magnesium hydroxide in poly(ethylene-co-vinyl acetate)

AbstractIn this study, we evaluated the interest of combining magnesium hydroxide (MDH) and lignin for developing complementary flame retardant actions in poly(ethylene-co-vinyl acetate) (EVA). Lignin was selected owing to its char forming ability thatwas supposed to reinforce the endothermic effect provided by MDH. The effect of lignin chemical modification by ammonium phosphate functions also evaluated as a way for enhancing its charring effect. Fire properties and thermal behavior of EVA composites were characterized using cone calorimeter, Pyrolysis Combustion Flow Calorimeter (PCFC) and thermogravimetric analysis (TGA). The effect of the incorporation of lignin alone on EVAcomposite thermal and fire behavior first evaluated. Results evidenced that the incorporation of lignin, whatever its nature, induced important reduction of composite thermal stability during TGA analysis as well as significant reduction of the time to ignition (TTI) in cone calorimeter test. However, a significant reduction of peak of heat release rate (pHRR), higher than that obtained with MDH was observed. The combination of lignin and MDH was led to further reduction of pHRR. Furthermore, it was concluded that the chemical modification of lignin is not required prior obtaining improved flame-retardant properties.

Impact of the combined use of layered double hydroxides, lignin and phosphorous polyol on the fire behavior of flexible polyurethane foams

Flexible polyurethane foams with densities of 40 ± 2 kg m−3 were prepared by combining different eco-friendly fillers such as layered double hydroxides (LDH) and kraft lignin (a byproduct of the pulp and paper industry) with a phosphorous polyol (E560) in order to study their effect on the mechanical performance and fire behavior of the foams. Two series of foams were prepared, some containing lignin or LDH separately, and some with a combination of both: one of the series was prepared without E560 (0E foam series) and the other with 5 parts per hundred of E560 polyol (5E series). The use of fillers resulted in increased viscosity of the reactive mixture, requiring higher blowing agent content in order to hold the density of the foams constant. It was observed that urea phase segregation was favored in the series of 0E foams due to their lower viscosity than the 5E series. This had consequent effects on the resilience, compression force deflection and compression set of these foams. In terms of fire behavior it was observed that while the limiting oxygen index decreased, cone calorimeter results showed that the combination of lignin, LDH and E560 decreased the heat release of the foams. In addition, the combination of fillers and E560 contributed to increase the viscosity of the pyrolysis products, preventing the dripping of the molten polymer, which is a key factor in flame propagation towards adjacent objects in fire scenarios.

Alternative to antibiotic-associated complications from the digestive tract after treatment of urological diseases (Review)

The use of a modern enterosorbent with a prebiotic component (a combination of lignin, lactulose and microcrystalline cellulose) in urological practice helps prevent the development of complications of antibiotic therapy in the treatment of urogenital infections.

Spectroscopic study of copper adsorption by chitosan and lignin composites containing layered double hydroxides

Lignin and chitosan are two widely available biomaterials which provide the base for designing biosorbents that remove heavy metals from water. On the other hand, layered double hydroxides (LDH) are well-known synthetic clays with the ability to remove pollutants from water.The goal of this work was to examine the relationship between these three sorbents and Cu(II) cations removed from water based on data obtained from infrared, electron paramagnetic resonance and X-ray photoelectron spectroscopies. Copper was selected as a model since this heavy metal concerns environmental chemists. Composite materials prepared by combinations of lignin with LDH and chitosan with LDH were also studied. Results indicate that LDH retains Cu(II) by coordinating with hydroxyl groups forming Cu(II) complexes with axial symmetry; lignin retains Cu(II) through hydroxyl and hydroxyphenol groups; when lignin is mixed with LDH to prepare the composite, concentrated domains of copper are formed. In chitosan, C–O is the main coordinating group (94%), forming spread coordination centers for Cu(II) with rhombic symmetry; the chitosan LDH composite enriches the type of ligands retaining copper, probably a reduction of amino groups that were consumed to interact with LDH particles. Cu(II) cations in this composite form square planar or tetragonal distorted octahedral coordination sites.

One-Step Fabrication of Dual Responsive Lignin Coated Fe3O4 Nanoparticles for Efficient Removal of Cationic and Anionic Dyes

A new, simple one-step approach has been developed to synthesize lignin and lignin amine coated Fe3O4 nanoparticles. These nanoparticles (lignin magnetic nanoparticles (LMNPs) and lignin amine magnetic nanoparticles (LAMNPs)) are found to possess not only magnetic response but also pH-dependent adsorption behavior. Results show that the combination of lignin with nanoparticles increased the adsorption capacities 2–5 times higher than other traditional single lignin based adsorbents (211.42 mg/g for methylene blue (MB) by LMNPs and 176.49 mg/g for acid scarlet GR (AS-GR) by LAMNPs). Meanwhile, by simply adjusting the pH, the dye-loaded adsorbents can be regenerated to recycle both adsorbents and dyes with a desorption efficiency up to 90%. Mechanistic study shows that dye structure and surface charges of adsorbents play the most important part in adsorption where dyes interact with the adsorbent surface via π–π stacking and electrostatic attraction interactions. The efficient fabrication method, eco-friendly reactant, quick magnetic separation, high adsorption and desorption efficiency suggest this novel type of nano-adsorbents to be promising materials for efficient dye pollutant removal and recovery.