Lignin Extraction Research Articles

Optimizing conditions for using deep eutectic solvents to extract lignin from black liquor

Optimizing conditions for using deep eutectic solvents to extract lignin from black liquor

Optimization of Lignin Extraction and Isolation of Substituted Hydroxycinnamic Acids from Sugarcane (Saccharum officinarum) Bagasse Lignin Hydrolysate

Optimization of Lignin Extraction and Isolation of Substituted Hydroxycinnamic Acids from Sugarcane (Saccharum officinarum) Bagasse Lignin Hydrolysate

Investigation of the chemical profiles of seven wood species for their potential applications

ABSTRACT Determination of the chemical composition of biomaterial is important for their valued utilization in biorefinery. In this study, the chemical composition of seven wood species, i.e. lambu (Khaya anthotheca), raj-koroi (Albizia richardiana), jhau (Casuarina equisetifolia), sil-koroi (Albizia procera), katbadam (Terminalia catappa), jolpai (Elaeocarpus robustus), and arjun (Terminalia arjuna) were examined. The chemical characterization of these wood species can expedite a further study on the extraction of cellulose, lignin, and extractive. α-cellulose content was in the range of 37.0% to 42.1% and lignin content was 20.4% to 34.1%. The solubility in 1% caustic soda was 16.1% to 24.3%. The α-cellulose and lignin content were similar to other wood species. Therefore, these species can be a potential source of raw material for biorefinery.

Treatment of Water Hyacinth Fibers to Improve Mechanical and Microstructural Properties of Green Composite Materials

In this study, the water hyacinth was used as a reinforcement of green composites. The chemicals for treatment of water hyacinth were solutions of alkaline, soap and water to determine water absorption. The chemical treated process of the water hyacinth fibers had important influences to the chemical structures and mechanical properties of the green composites. Micrographs analyses of scanning electron microscope (SEM) showed obviously roughness of fiber surface after the chemical treatment as well as arrangement of structures among the water hyacinth fibers. Similarly, the results of analysis by Fourier transform infrared spectroscopy (FT-IR) showed that most of the intensity of the absorbed peaks was decreased markedly at the wavenumbers of 1375 cm-1and 1542 cm-1. These are related to lignin extraction with alkaline solution, effectively. In particular, the compressive strength of the water hyacinth/roving composite has high value approximately to that of fiberglass composites (unfriendly composites). The water hyacinth/roving composites have significantly improvements in flexural and compressive strengths and this proves that the environmentally friendly composite responded to high requirements for various applications.

A hydrotrope pretreatment for stabilized lignin extraction and high titer ethanol production

The biomass pretreatment strategies using organic acids facilitate lignin removal and enhance the enzymatic digestion of cellulose. However, lignin always suffers a severe and irreversible condensation. The newly generated C–C bonds dramatically affect its further upgrading. In this study, we used a recyclable hydrotrope (p-Toluenessulfonic acid, p-TsOH) to dissolve lignin under mild condition and stabilized lignin with a quenching agent (formaldehyde, FA) during extraction, achieving both value-added lignin extraction and efficient enzymatic saccharification of cellulose. Approximately 63.7% of lignin was dissolved by 80% (wt. %) p-TsOH with 1.5% FA addition at 80 °C, 30 min. The obtained lignin was characterized by FTIR spectroscopy, TGA, 2D HSQC NMR spectroscopy, and GPC. The results indicated that the extracted lignin exhibited excellent properties, such as light color, a low molecular weight (Mw, 5371 g/mol), and a narrow polydispersity (Mw/Mn, 1.63). The pretreated substrate was converted to ethanol via a quasi-simultaneous saccharification and fermentation process (Q-SSF). After fermentation of 60 h, the ethanol concentration reached 38.7 ± 3.3 g/L which was equivalent to a theoretical ethanol yield of 82.9 ± 2.2% based on the glucan content, while the residual glucose concentration was only 4.69 ± 1.4 g/L. In short, this pretreatment strategy protected lignin to form new C–C linkages and improved the enzymatic saccharification of glucan for high-titer ethanol production.Graphical

Lignin extraction from black liquor using acetate based ionic liquids: Extraction kinetics and product characterization

One ionic liquid, 1-ethyl-3-methylimidazolium acetate [Emim][Ac] and four acetate-protic ionic liquids (PILs), ethanolammonium acetate [Eth][Ac], diethylenammonium acetate [DiEt][Ac], propylammonium acetate [Prop][Ac], and pyrrolidinium acetate [Pyrr][Ac], were employed to extract lignin from Kraft black liquor (BL). Under atmospheric pressure and at 368 K, the total lignin extracted was 75.3 ± 3.4% (wt%) when using [Eth][Ac] in a 20:1 (w/w) [Eth][Ac]:BL ratio and a reaction time of 270 min. Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (1H NMR) were employed to characterize the extracted lignin. Gel permeation chromatography revealed that molecular weights of 2283±67 g mol−1 and 1892±122 g mol−1 were measured for the lignin extracted using [Eth][Ac] and [Prop][Ac], respectively. The kinetics of lignin extraction were examined for a 270 min. reaction time period at three different temperatures. The lowest activation energy (Ea = 6.5 kJ·mol−1) was affiliated with [Prop][Ac]. The PIL with the maximum total lignin extracted, [Eth][Ac], was regenerated using vacuum distillation, and the lignin extraction ability of the regenerated solvent was found to be equivalent to the fresh solvent.

Analysis of Polymeric Composites of Phormium Tenax

Phormium tenax is a vegetal fiber with a mechanical strength of 711 ± 61.1 MPa, which is higher than the range of sisal (468-640MPa) and similar to the well-known curauá fiber (913 MPa). In this study, Phormium tenax composites coated with maleated polypropylene in a polypropylene matrix were prepared with 20%, 30%, and 35wt% of fibers, with and without aluminum sheets made from beverage cans. Some samples were made by extrusion and compression molding process, and others only through compression molding. In addition, density tests indicated lightness in composites of Phormium tenax. Samples were submitted to thermal analyzes, X-ray diffraction, Fourier Transform with Infrared Region, and scanning electron microscopy. Their fibers content of cellulose, hemicellulose, lignin, ashes,and total extractives are respectively 44.27%, 13.20%, 15.02%, 23.4%, and 4.11%. Some based-PP composites reinforced with Phormium tenax showed improvement in the flexural strength, such as based-PP reinforced with long and continuous fibers, with a flexural strength of 64.94 MPa, and 52,30 MPa, respectively. It was concluded that tensile strength in PP-based composites reinforced with Phormium tenax could be enhanced with some adjustments in the material processing.

Investigation of the potentiality of five bamboo species in biorefinery through analysis of chemical profiles

Determination of the chemical composition of biomaterial is important for their valued utilization in biorefinery. In this study, the chemical composition of five bamboo species, i.e., mitinga (Bambusa tulda), borak (Bambusa balcooa), rengoon (Thyrsostachys oliveri), orah (Dendrocalamus longispathus), and bajja (Bambusa vulgaris) were determined. The chemical characterization of these bamboo species can expedite a further study on the extraction of cellulose and lignin. α-cellulose content was in the range of 42.7–45.7% and Klason lignin content was 22.4–28.2%. The ash content was 1.8–4.3% for the studied five bamboo species. The α-cellulose and lignin content were similar to other non-timber spices. The ash content was lower than other non-timber species. Therefore, these species can be a potential source of raw material for biorefinery.

Fractionation of Lignin Streams Using Tangential Flow Filtration

Lignin fractionation helps its valorization process and yields high-quality and -value products. In this study, cascading tangential flow filtration (TFF) was employed for the fractionation of lignin molecules. The lignin-rich stream was obtained from the pretreatment process of corn stover using alkali (NaOH) and cholinium lysinate ([Ch][Lys]) as the catalyst. The effect of TFF (microfiltration, ultrafiltration, and nanofiltration) on lignin molecular weight, sugar distribution, viscosity, and lignin functional groups was investigated. In general, the study concluded that the average molecular weight (MW) and polydispersity of the permeate stream decreased with the reduction of the membrane pore size. TFF was effective in separating the low-MW lignin (200–350 Da) from the aqueous stream. Approximately 2% of monomeric lignin and 10–20% of low-molecular-weight lignin were recovered from NaOH- and [Ch][Lys]-extracted streams. Techno-economic analysis (TEA) results show that a high percentage of the low-MW lignin extraction can be achieved via a cascade TFF membrane operating at high transmembrane pressures (TMPs) and cross membrane velocities. Additionally, a high initial concentration of lignin in the liquid stream plays a critical role in the lignin product yield and recovery cost.

Efficient separation of bagasse lignin by freeze–thaw-assisted p-toluenesulfonic acid pretreatment

Lignin separation is an important procedure that benefits multiple industries and in particular biomass transformation efforts. In this study, bagasse lignin was separated by freeze–thaw-assisted p-toluenesulfonic acid (p-TsOH) pretreatment. The optimal conditions were freezing temperature −60 °C, freezing time 8.0 h, thawing temperature 15 °C, p-TsOH concentration 60%, pretreatment temperature 70 °C, and time 20 min. Lower acid concentrations and temperatures were used compared with traditional p-TsOH pretreatment. The efficiency and selectivity of lignin separation were improved. It was attributed to freeze-thawing, which provided a more efficient physical channel for the effective penetration of p-TsOH. The separation, extraction and purity of lignin were improved to 89.76%, 78.22% and 77.89%, respectively. High separation, high extraction, high purity and large molecular weight lignin samples were obtained. In addition, the recovery and reuse of p-TsOH was enhanced. This provided a new method for the efficient and clean separation of lignin.

Mass Transport Limitations and Kinetic Consequences of Corn Stover Deacetylation

Alkaline pretreatment of herbaceous feedstocks such as corn stover prior to mechanical refining and enzymatic saccharification improves downstream sugar yields by removing acetyl moieties from hemicellulose. However, the relationship between transport phenomena and deacetylation kinetics is virtually unknown for such feedstocks and this pretreatment process. Here, we report the development of an experimentally validated reaction–diffusion model for the deacetylation of corn stover. A tissue-specific transport model is used to estimate transport-independent kinetic rate constants for the reactive extraction of acetate, hemicellulose and lignin from corn stover under representative alkaline conditions (5–7 g L−1NaOH, 10 wt% solids loadings) and at low to mild temperatures (4–70°C) selected to attenuate individual component extraction rates under differential kinetic regimes. The underlying transport model is based on microstructural characteristics of corn stover derived from statistically meaningful geometric particle and pore measurements. These physical descriptors are incorporated into distinct particle models of the three major anatomical fractions (cobs, husks and stalks) alongside an unsorted, aggregate corn stover particle, capturing average Feret lengths of 917–1239 μm and length-to-width aspect ratios of 1.8–2.9 for this highly heterogeneous feedstock. Individual reaction–diffusion models and their resulting particle model ensembles are used to validate and predict anatomically-specific and bulk feedstock performance under kinetic-controlled vs. diffusion-controlled regimes. In general, deacetylation kinetics and mass transfer processes are predicted to compete on similar time and length scales, emphasizing the significance of intraparticle transport phenomena. Critically, we predict that typical corn stover particles as small as ∼2.3 mm in length are entirely diffusion-limited for acetate extraction, with experimental effectiveness factors calculated to be 0.50 for such processes. Debilitatingly low effectiveness factors of 0.021–0.054 are uncovered for cobs—implying that intraparticle mass transfer resistances may impair observable kinetic measurements of this anatomical fraction by up to 98%. These first-reported quantitative maps of reaction vs. diffusion control link fundamental insights into corn stover anatomy, biopolymer composition, practical size reduction thresholds and their kinetic consequences. These results offer a guidepost for industrial deacetylation reactor design, scale-up and feedstock selection, further establishing deacetylation as a viable biorefinery pretreatment for the conversion of lignocellulosics into value-added fuels and chemicals.

EXTRACTION AND CHARACTERIZATION OF LIGNIN FROM MOROCCAN THUYA. ITS APPLICATION AS ADSORBENT OF METHYLENE BLUE FROM AQUEOUS SOLUTION

"The present investigation includes the extraction of lignin from waste sawdust of the wood industry (Tetraclinis articulata) using sulfuric acid treatment, its characterization and further use for the removal of methylene blue (MB) cationic dye from aqueous media. The extracted lignin was characterized by FT-IR and XRD, its thermal properties were studied using TGA and DSC analyses, and its surface morphology was observed by SEM and EDX. The FT-IR spectra showed homogeneity in the chemical structure of the lignin sample. In the adsorption study, the effects of temperature, contact time, and adsorption concentration of MB were determined. The kinetic study showed that the second-order model gives a better description of the kinetics of the adsorption reaction than the first-order model. The analysis of adsorption isotherms using different classical models showed that adsorption may be governed by the Langmuir isotherm. The thermodynamic parameters were determined from the values of the maximum adsorption capacity and equilibrium constants."

Deep eutectic solvent pretreatment of biomass: Influence of hydrogen bond donor and temperature on lignin extraction with high β-O-4 content

Recovering lignin with high β-O-4 content is of prime interest for further high yield depolymerization in low molecular weight phenolic compounds. Pretreatment of lignocellulosic biomass with deep eutectic solvents (DES) was studied to extract this type of tailored lignin from softwood and brewer’s spent grains. In this work, choline chloride (ChCl) based DES with two different hydrogen bond donors (HBD) (lactic acid (LA) and Glycerol (Gly)), were investigated at mild temperatures (60 and 80 °C). The influence of DES pretreatment on extracted lignin molecular weight and structural characteristics was analysed. The acidity and density of DES were proved to affect lignin extraction yield and its features. The lignin characteristics (type of interunits, accessibility) were shown to impact their ability to be recovered. Acidic-DES ChCl:LA at 80 °C with woody biomass gave promising results with 78% of lignin extracted exclusively composed of G units with 61% of β-O-4 linkages with narrow molecular weights distribution.

Evaluation of biomass-derived solvents and protic ionic liquids as lignin-selective pretreatment agents for poplar fractionation

In this study, mixtures of protic ionic liquids (PILs) and biomass derived solvents; gamma-valerolactone (GVL), levulinic acid (LA) and H2O at different weight percentages were used to pretreat poplar. GVL addition up to 60% enhanced delignification in biomass that is subjected to MEAHSO4-GVL-H2O; cellulose content of the biomass increased from 42% to 74% with 67% lignin removal. Aqueous solution of LA used for the first time to pretreat a biomass performed better than TEAHSO4-H2O. LA-H2O at 80%-20% resulted in 70% lignin extraction and preserved 89% of the cellulose in the structure which were also verified with SEM, FTIR and XRD analysis displaying clear cellulose macrofibers, lignin signals with lower intensities and higher biomass crystallinity, respectively. Accordingly, enzymatic conversion of LA pretreated poplar released 43 g/L glucose at 10% substrate loading. Findings showed the potentials of biomass derived solvents, GVL and LA and PILs and their aqueous mixtures to selectively deconstruct poplar.

Deep eutectic solvent with bifunctional Brønsted-Lewis acids for highly efficient lignocellulose fractionation

Green and low cost deep eutectic solvents (DESs) are promising to replace the solid acids and ionic liquids in biomass fractionation process. To enhance the lignocellulose pretreatment efficiency, an acidic DES that composed of Brønsted acid (ZnCl2) as hydrogen bond acceptor and Lewis acid (lactic acid) as hydrogen bond donator was designed. This bifunctional DES was used for the extraction of lignin from poplar sawdust. Under the optimal pretreatment condition, the ZnCl2-lactic acid DES could recover 95.2 wt% of lignin with a purity of 92.1%. The recovered lignin demonstrated a low polydispersity of 1.67 and small amount of β-aryl-ethers. Moreover, the acidic DES had a good recyclability and reusability. Such performance was attributed to the presence of bifunctional acid sites, which help selectively cleave lignin-carbohydrate complex linkages. The acidity and polarity of Brønsted acid can be modulated by the Lewis acid, thus synergistically promote the lignin extraction and production.

Green mechano-chemical processing of lignocellulosic biomass for lignin recovery

Lignin extraction from biomass is heavily dependent on chemical processes that are harmful to the environment and the quality of the recovered lignin. Ionic liquid solvents are some of the latest solutions in green processing; however, their implementation for lignin recovery is limited by their high cost, typically high loadings requirements, and long processing times. To overcome these issues, in this study, high loadings of mixed hardwood flour (MHF) were processed with 1-butyl-3-methylimidazolium chloride (BmimCl) in a batch mixer. The rheological behaviour of the biomass and ionic liquid mixture was studied. The mixture had a high complex viscosity (approx. 107 Pa s) at low shear rates and displayed pronounced shear thinning behavior at 50 wt% MHF loading. A 22 factorial design was also implemented to study the effects of MHF solid loading amount and residence time on lignin extraction yield. A maximum yield of 36.6% was obtained at the maximum solid loading amount and residence time (50 wt% and 45 min, respectively). The extracted lignin samples were also characterized in comparison with commercial Kraft lignin and lignosulfonate. The novelty of this study is the successful lignin extraction at high solid loadings and shorter residence times compared to previous biomass pre-treatments with ionic liquids that employs low solid loading and long processing times.

Cellulose Membranes in the Treatment of Spent Deep Eutectic Solvent Used in the Recovery of Lignin from Lignocellulosic Biomass.

Ultrafiltration was employed in the purification of spent Deep Eutectic Solvent (DES, a mixture of choline chloride and lactic acid, 1:10, respectively) used in the extraction of lignin from lignocellulosic biomass. The aim of this was to recover different lignin fractions and to purify spent solvent. The results revealed that the commercial regenerated cellulose membranes—RC70PP and Ultracel 5 kDa UF membranes—could be used in the treatment of the spent DES. The addition of cosolvent (ethanol) to the spent DES decreased solvent’s viscosity, which enabled filtration. With two-pass ultrafiltration process with 10 kDa and 5 kDa membranes about 95% of the dissolved polymeric compounds (lignin and hemicelluloses) were removed from the spent DES. The utilized membranes also showed the capability to fractionate polymeric compounds into two fractions—above and under 10,000 Da. Moreover, the 10 kDa cellulose-based membrane showed good stability during a continuous period of three weeks exposure to the solution of DES and ethanol. Its pure water permeability decreased only by 3%. The results presented here demonstrate the possibility to utilize cellulose membranes in the treatment of spent DES to purify the solvent and recover the interesting compounds.

Synthesis of Green Deep Eutectic Solvents for Pretreatment Wheat Straw: Enhance the Solubility of Typical Lignocellulose

Deep eutectic solvents (DESs), a novel and environmentally-friendly solvent, have high potential for biomass pretreatment due to its advantages of low cost, low toxicity, strong solubility, excellent selectivity and biocompatibility. Two types of DES (binary and ternary) were synthesized and characterized, and optimized ternary DES was selected to pretreat wheat straw for enhancement of the solubility of lignocellulose. Moreover, enzymatic hydrolysis was tested to verify the performance of pretreatment. In addition, the changes in surface morphology, structure and crystallinity of wheat straw pretreated by DES were analyzed to reveal the pretreatment mechanism. Experimental results indicated that viscosity exhibited little difference in different types of DESs, and a declining trend as the temperature increases in same DES. The ternary DES pretreatment efficiently enhanced the solubility of typical lignocellulose, with the optimal removal rate of lignin at approximately 69.46%. Furthermore, the total sugar concentration of the residue was about 5.1 times more than that of untreated wheat straw after the pretreated samples were hydrolyzed by the cellulase for 24 h, indicating that DES has the unique ability to selectively extract lignin and hemicellulose from wheat straw while retaining cellulose, and thus enhanced the solubility of lignocellulose. The scanning electron microscope (SEM) observation and X-ray diffraction (XRD) determination showed that the surface of wheat straw suffered from serious erosion and the crystallinity index of wheat straw increased after DES5 pretreatment. Therefore, DES cleaves the covalent bond between lignin and cellulose and hemicellulose, and reduces the intractability of lignin resulting in the lignin dissolution. It suggests that DES can be used as a promising and biocompatible pretreatment way for the cost-effective conversion of lignocellulose biomass into biofuels.

Delignification of hemp stalk using a low transition temperature mixture composed of choline chloride and lactic acid

This work used a literature search to select the most suitable system for the delignification process of annual plants. This process was evaluated in terms of lignin removal from plant biomass. Based on previous experiments, a low transition temperature mixture (LTTM) was used, which was a mixture of choline chloride and lactic acid in a molar ratio of 1:2. Samples of hemp fibers were examined. The delignification of biomass was monitored by changing the content of the main components. After application of the solvent at a temperature of 100, 120, or 140 °C and a delignification time of 2 or 4 h, the lignin content expressed by Kappa number decreased to the level of 22 to 13.7. Yields of hemp fibers sown after LTTM application ranged from 72.5 to 90.6%. The results confirmed that the use of LTTM (choline chloride/lactic acid) is a suitable system for the extraction of lignin from biomass. The findings showed that LTTM was an effective delignifying agent for hemp, as a relatively low Kappa number of 13.7 and a yield of 75.9% were achieved after only 2 h and at 140 °C.

Extraction of Lignin from Sugar Cane Bagasse by Prominent Methods and its Structural Characterization

Extraction of Lignin from Sugar Cane Bagasse by Prominent Methods and its Structural Characterization