Lignin Extraction Research Articles

Mild isolation and characterization of surface lignin from hydrothermally pretreated lignocellulosic forestry and agro-industrial waste biomass

Within the biorefining concept, the lignocellulosic biomass wastes can serve as feedstock to produce value-added chemicals and fuels. The sustainable valorization of biomass is based on integrated processes that aim to the utilization of “whole biomass”. To this end, the first step of the efficient biomass pretreatment towards selective isolation of cellulose, hemicellulose and lignin, is of paramount importance. Hydrothermal pretreatment of biomass in neat water is a green and well-established process that enhances hemicellulose removal and recovery in the liquid fraction, affording a cellulose and lignin enriched solid which can be enzymatically hydrolyzed to glucose. A simple and efficient method to facilitate the hydrolysis is the prior extraction of the formed “surface” lignin which hinders the action of enzymes. Within this context, in this work, forestry (beechwood sawdust) and agro-industrial (vine prunings, apricot kernel shells) wastes were hydrothermally pretreated in neat water (at 220 °C, 15 min) and the formed surface lignin was extracted via soxhlet or reflux methods under mild conditions, with the use of green solvents (ethanol, acetone). The delignification degree of the pretreated biomass was in the range of 35–67 wt%, depending on the solvent and biomass feedstock. The recovered surface lignins were of high purity and exhibited similar physicochemical and structural characteristics with the organosolv lignin. The fast pyrolysis of surface lignins afforded bio-oils enriched in alkoxy-phenols and oxy-aromatics. The biomass solids recovered after lignin extraction are enriched in cellulose (70%) and exhibit high relative crystallinity and improved textural properties, thus increasing their potential valorization.

Exploring the Potential of Vine Shoots as a Source of Valuable Extracts and Stable Lignin Nanoparticles for Multiple Applications.

Large amounts of vine shoots are generated every year during vine pruning. This residue still presents many of the compounds found in the original plant, including low molecular weight phenolic compounds and structural compounds such as cellulose, hemicellulose, and lignin. For wine-producing regions, the challenge is to develop alternatives that will increase the value of this residue. This work proposes the full valorization of vine shoots, focusing on the extraction of lignin by mild acidolysis for the preparation of nanoparticles. The effect of the pretreatment solvents (ethanol/toluene, E/T, and water/ethanol, W/E), on the chemical and structural features of lignin, was evaluated. The chemical analysis suggests similar composition and structure regardless of the pretreatment solvent, although lignin isolated after pretreatment of biomass with E/T showed a higher content of proanthocyanidins (11%) compared with W/E (5%). Lignin nanoparticles (LNPs) presented an average size ranging from 130-200 nm and showed good stability for 30 days. Lignin and LNPs showed excellent antioxidant properties (half maximal inhibitory concentration, IC50 0.016-0.031 mg/mL) when compared to commercial antioxidants. In addition, extracts resulting from biomass pretreatment showed antioxidant activity, with W/E presenting a lower IC50 (0.170 mg/mL) than E/T (0.270 mg/mL), correlated with the higher polyphenol content of W/E, with (+)-catechin and (-)-epicatechin being the main compounds detected. Overall, this work shows that the pre-treatment of vine shoots with green solvents can yield (i) the production of high-purity lignin samples with antioxidant properties and (ii) phenolic-rich extracts, promoting the integral reuse of this byproduct and contributing to sustainability.

Broadening the product portfolio with cellulose and lignin nanoparticles in an elephant grass biorefinery

AbstractCellulose and lignin nanoparticles are high‐value‐added products obtained from lignocellulosic biomasses through several steps of cellulose purification and lignin extraction. These steps drastically reduce the potential feedstock revenue when carried out as stand‐alone methodologies. To increase biomass yields, we describe here a strategy to design a biorefinery focused on producing cellulose and lignin nanoparticles as main products, but also aim to recover and benefit from other biomass components using only water‐based processes. Sequential pressurized liquid extractions and diluted acid and alkaline treatments were carried out to fractionate elephant grass biomass, yielding (for every 100 g of biomass): 30 g of cellulose pulp (converted to 9 g of cellulose nanocrystals and 9 g of cellulose nanofibers); 10 g of lignin (used to produce 8.5 g of stable colloidal lignin nanoparticles by probe‐sonication in water); 7.5 g of extractives (e.g. sterols and phenolics) and 23 g of xylose (converted to 4.1 g of furfural). Alternatively, to allow for the flexible use of the cellulose fraction in the proposed biorefinery, 22 g of glucose could be produced by enzymatic hydrolysis. The results demonstrate that water‐based processes are suitable for a holistic use of biomass, providing a comprehensive set of high‐value‐added co‐products that are renewable and cost‐effective chemical, cosmetic, food, polymer and pharmaceutical solutions.

Treatment of Pulp Black Liquor with an Ionic Liquid: Optimisation by Using Response Surface Methodology.

: In this study, selective extraction towards ionic liquid trihexyltetradecylphosphonium chloride ([P66614]Cl) of lignin residues, polysaccharides and organic acids present in black liquor (BL), the main principal wastewater of pulping industry was studied. With the objective of finding optimized conditions allowing to extract lignin resideus while polysaccharides and organic acids remain in aqueous solution, a design of experiments approach based on a response surface methodology was used. Three continuous factors, namely initial pH varying from 9 to 13.5, dilution of BL varying from 5 to 20 and volumetric ratio of black liquor vs. ionic liquid RV., varying from 1 to 19, were investigated. Concentration of ligni residues, polysaccharides and organic acids were measured using Folin-Ciocalteu method, the anthrone method and HPLC, respectively. Results showed that a multi-response optimization led to the extraction of 84.8 % of lignin residues, 66.0 % of polysaccharides, and no extraction of OA under optimised conditions.

Role of extractable lignin in enzymatic hydrolysis of hydrothermally pretreated hardwood

Role of extractable lignin in enzymatic hydrolysis of hydrothermally pretreated hardwood

Fascinating polyphenol lignin extracted from sawdust via a green and recyclable solvent route

Due to the complexity, heterogeneity and recalcitrant structure of lignin, the extraction of multifunctional lignin directly from lignocellulose is still a challenge. Here, a green and recyclable route was proposed to separate high-quality lignin and tailor its functionalities. Through tuning the components of deep eutectic solvent (DES) and separation procedures, DES extracted lignin (DESL) exhibited high purity of 99.6 %, yield of 83.2 % and phenolic hydroxyl content of 8.33 wt%. The results of FTIR and 13C NMR demonstrated that DESL possessed more oxygen-containing reactive groups compared with commercial lignin (CL), enabling DESL with more superior functional activities. DESL exhibited higher antioxidant activity with the DPPH capture rate of 73.2 %. Meanwhile, DESL showed strong bactericidal effects against E. coli (100 %) and S. aureus (100 %) due to higher phenolic hydroxyl content, which could destroy bacterial cell membranes and inhibit bacterial metabolism by interacting with phospholipid layer and protein. Additionally, DESL displayed strong UV absorption and could be blended with polyurethane to enhance UV shielding property of polyurethane composite film with >50 of UPF value. In summary, DES treatment is a suitable strategy for high-quality lignin separation, which opens a broad spectrum of possibilities for lignin valorization.

Technical kraft lignin from coffee parchment

Abstract The biomass deconstructed by kraft process and the lignin dissolved in the black liquor are burned to generate energy in a pulp mill. This study used the black liquor from coffee parchment cooking, a residue from the coffee industry, to isolate kraft technical lignin. The parchment was subjected to the kraft pulping process to obtain pulps of kappa number 60 and 25, and the resulting black liquors were used for lignin extraction. Chemical characterization, elemental analysis and heating value of liquors and lignins were performed, as well as FTIR and Py-CG-MS analysis of lignins. The cooking provided liquors with similar characteristics, with lignin content of 31.67 and 32.63% for kappa 60 and 25 liquors, respectively. The extractions resulted in high purity lignin (92.35% for K#60 lignin and 93.96% for K#25 lignin). The higher heating values were 23.8 and 25.4 MJ/kg for K#25 and K#60 lignins, respectively. FTIR analysis showed characteristic peaks of lignin. Through Py-GC-MS, it was possible to observe the slight predominance of guaiacyl-type lignin, which can be an advantage depending on the application. It is possible to extract lignin from the black liquor obtained from the coffee parchment pulping to generate products with high-added value.

High-purity alkaline lignin extraction from Saccharum ravannae and optimization of lignin recovery through response surface methodology

Saccharum ravannae, known as “Ekra” in the Northeast region of India, is an elephant grass species that abundantly grows in the natural habitat of Assam. This study aims to utilize this wild grass species and extract alkaline lignin of high purity through KOH-mediated alkaline hydrothermal pretreatment using the Oil bath process. Lignin recovery was optimized using RSM (response surface methodology) combined with a central composite model. Three process parameters, namely KOH concentration (1–3 %), reaction time (50–200 min), and solid loading (5–15 %), varied to optimize the combined effect of these parameters. RSM predicted a maximum lignin recovery of 15.38 g/100 g of raw biomass at optimum conditions (2.4 % KOH, 6.41 % solid loading, 176.57 min). Three experimental runs were performed at optimum conditions, and 15.81 ± 0.32 g/100 g lignin recovery was obtained, thus verifying the predicted result. Maximum 93.7 % purity of extracted lignin was achieved in a different operating condition (3 % KOH, 10 % solid loading, 125 min). The commercial and extracted alkaline lignin with maximum purity was characterized by Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The extracted lignin shows higher phenolic content and more functional groups than commercial lignin and can be used for future applications.

Optimization of low carbon steel coating with corrosion inhibitor method based on siwalan (Borassus flabellifer) fiber extract

Siwalan fiber waste (SFW) has the potential as a source of lignin (7-25%) which is used as a green inhibitor to inhibit the corrosion rate of low carbon steel (LCS). The aims of this study were: (1) determine the optimum conditions (types of HCl and H2SO4, Cinhibitor and Cmedia, inhibition temperature, and coating time) for LCS coating process using the inhibitory method using lignin extract from SFW, and (2) knowing the resistance of LCS coated with inhibitor at optimum conditions. Empirical research through laboratory experiments explains the relation between variables by analyzing numerical data. 185g of SFW produced 52.289g (28.26%) fine brown powder. IR spectrum analysis on extract showed the wavelength was almost the same as the standard. IR spectrum analysis was also carried out on the extracted compounds that were adsorbed, and the absorption peaks confirmed the presence of lignin in the adsorbed compounds. Based on the results of the analysis of the weighing data of the specimen before and after inhibition, the inhibitor concentration of 0.2–0.3 g/L in H2SO4 at 313K is the optimum condition to suppress the corrosion rate on the surface of LCS by 76.2%.

Recovery of lignins with antioxidant activity from Brewer’s spent grain and olive tree pruning using deep eutectic solvents

Agro-food industry generates lignocellulosic residues that can be highly valuable. Nonetheless, lignin is still an underrated biopolymer although it has several potential applications. Lignin can be extracted from biomasses using several pretreatments, being Deep Eutectic Solvents (DES) an environmental-friendly method. Thus, this work proposes to recover lignin from two different agro-food residues – Brewer’s spent grain (BSG) and Olive tree pruning (OTP) – using DES. Experimental designs were carried out for each residue to determine the best lignin extraction conditions based on yield and antioxidant activity. The optimum conditions (120 °C and 5 h) allowed lignin yields of 54.4% and 37.8% for BSG and OTP, respectively, with relatively high purities (>75%). Structurally, both OTP and BSG lignins have similar molecular weights, and FTIR analysis showed that OTP has more aromatic related bands. The OTP lignin showed higher antioxidant activity than BSG. This study demonstrates, for the first time, that DES is a promising solvent for successfully extracting lignins from OTP and BSG biomasses with high purities and valuable properties.

Development of the lignin extraction method from para rubber wood sawdust with choline chloride-lactic acid deep eutectic solvent

This work investigated the extraction of lignin from para rubber wood sawdust by deep eutectic solvent extraction (DES) using choline chloride-lactic acid (ChCl-LA). The DES extraction was operated using ChCl/LA with molar ratio of 1:10, and the lignin was extracted with good yields. To determine the optimal conditions for lignin extraction by this technique, various factors were studied, including extraction temperature (90-150 °C), extraction time (6-24 h), the amount of water required for lignin precipitation (150-300 mL), and precipitation time (24-48 h). The optimized conditions were achieved at 150 °C, 24 h, 300 mL of DI water and 48 h of precipitation time, and the highest extracted lignin content was 17.54%. Moreover, excessive water in the extracted solution can be recovered with evaporation, and it was discovered that similar extracted lignin content could be obtained (16.85%) by only using 150 mL of DI water during lignin precipitation but extending the precipitation time to 48 h. This study provides a simple, inexpensive, and environmentally friendly lignin extraction technique.

Biomass pretreatment using biomass-derived organic solvents facilitates the extraction of lignin and enzymatic hydrolysis of glucan

Biomass pretreatment using biomass-derived organic solvents facilitates the extraction of lignin and enzymatic hydrolysis of glucan

Anisotropic Wooden Electromechanical Transduction Devices Enhanced by TEMPO Oxidization and PDMS.

In order to increase the number and contact probability of electric dipole on cellulose, acid and alkali treatment was employed to extract hemicellulose and lignin from original wood to gain a highly oriented cellulose frame. The combined means with 2,2,6,6-tetramethylpiperidine-1-oxyl-NaBr-NaClO oxidation and impregnation of PDMS with compression was subsequently used to enhance its mechanical performance and electromechanical conversion. The assembled wooden electromechanical device (10 mm × 10 mm × 1 mm) exhibits the maximum open-circuit voltage (V OC) of 11.75 V and short-circuit current (I SC) of 211.01 nA as stepped by foot. It can be sliced to fabricate a flexible sensor with high sensitivity displaying V OC of 2.88 V and I SC of 210.09 nA under the tapped state. Its highly oriented wood fiber makes it display significant anisotropy in terms of mechanical and electromechanical performance for multidirectional sense. This strategy will exactly provide reference for developing other high-performance piezoelectric devices.

Producing Lignin and Ethyl Levulinate from Wheat Stalk Using 1-(3-Sulfobutyl) Triethylammonium Hydrogen Sulfate and USY Zeolite

The facile, green, and efficient strategy for the separation of lignin from straw and subsequent production of value-added chemicals is crucial to the current utilization of straw. Herein, up to 23.72% of lignin was isolated from wheat stalk over cheap and green 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO4) in aqueous ethanol (Vethanol: Vwater = 4:1). The acquired lignin was verified as a p-hydroxyphenyl-guaiacyl-syringyl type, which had a narrower molecular weight distribution, better thermal stability, and higher purity compared with those of the lignin obtained using 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogen sulfate and 1-(3-sulfobutyl) pyridinium hydrogen sulfate. Moreover, a carbohydrate-rich liquid containing [BSTEA]HSO4 was obtained by water removal from the waste liquid after lignin separation and further converted to ethyl levulinate (EL) by a one-pot process in the presence of inexpensive and stable USY zeolite. The yield of EL reached 30.23% at 200 °C for 60 min over the presence of 40% [BSTEA]HSO4 and 60% USY zeolite. Under optimal conditions, the yields of lignin and EL can respectively reach 83.89 and 72.28% of those catalyzed by a fresh catalyst after five cycles. In short, the above-mentioned methods present a green, economic, and efficient route for the extraction of lignin and further treatment of the liquid waste generated during the extraction process.

Advanced Fractionation of Kraft Lignin by Aqueous Hydrotropic Solutions

Lignin is an underutilized high-potential biopolymer that has been extensively studied over the past few decades. However, lignin still has drawbacks when compared with well-known petroleum-based equivalents, and the production of tailored lignin fractions is highly in demand. In this work, a new method for the fractionation of Lignoboost Kraft Lignin (LKL) is proposed by using two different hydrotropes: sodium xylenesulfonate (SXS) and sodium cumenesulfonate (SCS). The different fractions are obtained by sequentially decreasing the hydrotropic concentration with the addition of water. Four and three different fractions were retrieved from the use of SXS and SCS, respectively. The LKL and respective fractions were analysed, and compared by GPC, FTIR-ATR, 1H-NMR, 13C-NMR, 31P NMR, 2D HSQC and SEM. The fractions showed different molecular weights, polydispersity, and amount of functional groups. Our water-based lignin fractionation platform can potentially be combined with different lignin extraction and processing technologies, with the advantage of hydrotrope recycling.

Light-colored lignin extraction by ultrafiltration membrane fractionation for lignin nanoparticles preparation as UV-blocking sunscreen

A wide range of applications are available for kraft lignin (KL). However, the dark color and wide size distribution of KL make it challenging to use in cosmetics and nanoparticle preparation. In this study, we fractionated KL from a paper-making enterprise using ultrafiltration membrane fractionation, and obtained four kinds of lignin with different molecular weights, namely ultrafiltration lignin (UL). Following that, lignin nanoparticles (ULNPs) were formed by self-assembly from four types of UL. Analyzing the UL and ULNP properties, the low molecular weight lignin, such as ULA, exhibited good antioxidant properties (89.47 %, 5 mg/mL), high brightness (ISO% = 7.55), high L⁎ value (L⁎ = 72.3) and low polydispersity index (PDI = 1.41). The ULNP showed a narrow size distribution (0.8–1.4 m) and high dispersibility in sunscreen. When ULNP was added to sunscreen with 5 % load, its sun protection factor (SPF) value increased from 14.93 to 63.74. Therefore, this study offered an effective way for the comprehensive utilization of pulping waste KL.

Effective fractionation of lignocellulose components and lignin valorization by combination of deep eutectic solvent with ethanol.

Introduction: A combination of deep eutectic solvent with ethanol was developed for pretreatment of Broussonetia papyrifera to effectively extract lignin and promote the subsequent enzymatic hydrolysis. Methods: In order to further explore the optimal conditions for enzymatic hydrolysis, a central composite design method was applied. Results and Discussion: The correlation between each factor and glucose yield was obtained, and the optimal conditions was 160°C, 60min, the ratio of DES to E was 1/1 (mol/mol). The results showed that compared with control, the glucose yield increased by 130.67% under the optimal pretreatment conditions. Furthermore, the specific surface area of biomass was increased by 66.95%, and the content of xylan and lignin was decreased by 86.71% and 85.83%. The correlation between xylan/lignin removal and enzymatic hydrolysis showed that the removal of lignin facilitated the glucose yield more significantly than that of xylan. To further explore the lignin valorization, the structural and antioxidant analysis of recovered lignin revealed that high temperature was favorable for lignin with good antioxidant performance. This pretreatment is a promising method for separating lignin with high antioxidant activity and improving cellulose digestibility.

Facile and sustainable preparation of hierarchical porous carbon material from lignin/DES mixture after pretreatment

Deep eutectic solvent (DES) pretreatment of lignocellulose is an appealing and green approach for efficient lignin extraction. However, the process of lignin regeneration and DES recovery was time-consuming and labor-intensive. Herein, without any separation and purification after the DES pretreatment of Eucalyptus, the lignin/DES mixture was firstly used to fabricate hierarchical porous carbon materials through DES-thermal carbonization (DTC) and activation. Results revealed that the DTC processing involved degradation, condensation, aromatization, and aggregation, which significantly improved the carbonization degree and thermostability of carbon materials. X-ray photoelectron spectroscopic results confirmed the introduction of nitrogen atom from the choline chloride/lactic acid DES into the fabricated carbon materials during the DTC processing. This phenomenon can generate extra pseudocapacitance and thus increase the specific capacitance of supercapacitors. The capacitance retention of the resultant porous carbon materials (AC-200–12) reached above 95% after 10,000 charge-discharge cycles, which was much superior to commercial activated carbon. This facile and sustainable methodology overcomes traditional complex and expensive methods for preparing carbon materials from hardwood, which show promising potential to be used as electrode materials in a supercapacitor.

High value-added lignin extracts from sugarcane by-products

This study evaluates the production of lignin bioactive extracts from sugarcane bagasse (SCB) and straw (SCS) alkaline black liquors using greener precipitating agents (methane sulfonic acid (MSA), formic acid (FA) and lactic acid (LA)) as replacers of sulfuric acid (SA), the most common one used in industry. Results showed that the highest precipitation yield was achieved by LA when applied to SCB (14.5 g extract/100 g SCB). Lignin SCB extracts were similar in composition in terms of total carbohydrates (61–70 %), lignin (22–30 %) and inorganics (1.6–2.6 %). Regarding the SCS extracts, similar yields were obtained among all extracts, however, differences in composition were observed between SA and greener precipitating agents, particularly in terms of sugar content. All extracts exhibited radical scavenging activity; overall the extracts were more effective in the scavenging of ABTS radical. FA was the most promising alternative to SA to recover lignin bioactive extracts. This work suggests organic acids as good candidates for obtaining valuable extracts from alkaline pulping of SCB and SCS instead of the conventional sulfuric acid.

Lignin extraction from lignocellulosic biomass (sugarcane bagasse) and its potential application as a feedstock for fuel production

Biomass can be categorised based on three macromolecular substances: hemicellulose, cellulose, and lignin. Lignin is the next abundant and vital organic substance in the plant's creation, and it is biodegradable. The present paper deals with the extraction of lignin from bagasse, a biomass waste, and its subsequent conversion to biofuel utilising a low-temperature transesterification technique. Lignin was successfully extracted from sugarcane bagasse and characterised by means of Nuclear magnetic resonance (NMR) technique. Using Response Surface Methodology, transesterification process three process variables were optimized: methanol (8–20 vol/vol), time (60–180 min), and catalyst (0–2 wt./wt.%). Extraction of lignin is confirmed by nuclear magnetic resonance (NMR) spectra, which exhibit peaks attributable to the carboxylic group, saturate aliphatic, and phenolic hydroxyl. A fuel yield of 84.65 % was attained with a 20:1 methanol to oil ratio, 1 % catalyst concentration, and 180-minute reaction time. The amount of methanol, reaction time, and catalyst concentration all had a substantial impact on fuel production. A model has been prepared to show the relationship of fuel yield with reaction time, catalyst concentration, and methanol.