Extraction and isolation of lignin from ash tree (Fraxinus exselsior) with protic ionic liquids (PILs)

Dissolution behavior of ionic liquids for different ratios of lignin and cellulose in the preparation of nanocellulose/lignin blends

Lignin is regarded as a potential solution for boosting the strength of cellulose-based products. However, the mechanism of co-solubilization for lignin and cellulose has not been investigated. In this study, the effect of lignin content on the interaction between lignin and nanocellulose during lignin/cellulose co-dissolution was examined. The results revealed that lignin binds to nanocellulose throughout the dissolution process to limit the degradation of cellulose and to prepare nanocellulose/lignin composites. Moreover, the S units in lignin were more likely to interact with cellulose during the dissolution process, whereas the G units were more likely to condense. However, when the lignin content exceeded 30 wt%, the excess lignin created a severe condensation reaction, which led to a decrease in the lignin content bound to cellulose, resulting in an unequal dissolution of cellulose. Thus, a small amount of lignin attached to cellulose during the co-dissolution of lignin and cellulose inhibits cellulose degradation and can be utilized to create nanocellulose/lignin to extend the potential applications of nanocellulosic materials.

Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction of cellulose from Urtica dioica: A benign to green approach

The extraction of cellulose using eco-friendly solvents has been gaining significant attention for a couple of decades. This study investigated the impact of benign and green solvents on the extraction, thermal stability, mechanical properties, and crystallinity of cellulose extracted from Urtica dioica (Stinging nettle) using a Sono-Microwave Assisted Chlorine free and Ionic Liquid (SMACIL) extraction technique. In this regard, the stalks were undergone through pre chemical treatment before starting bleaching them with hydrogen peroxide (HPO) and 1-butyl-3-methylimidazolium acetate (BMIM-Ac) having different mole ratios (5, 7.5, and 10) to expose cellulose. The Urtica dioica cellulose (UDC) was characterized using FTIR, tensile testing, FESEM, XRD, and TGA. The fibrillation and lumen can be seen in SEM images that confirm the extraction of cellulose. The results showed that the BMIM-Ac-10 gives the maximum cellulose yield (88 %) than other compositions. Moreover, the cellulose extracted using BMIM-Ac-10 has high mechanical strength which makes it a potential constituent for various applications in the field of materials science. These results have significant implications for the development of sustainable and efficient processes for the extraction of cellulose.

Impact of Extraction Method on the Structure of Lignin from Ball-Milled Hardwood

Understanding the structure of hardwoods can permit better valorization of lignin by enabling the optimization of green, high-yield extraction protocols that preserve the structure of wood biopolymers. To that end, a mild protocol was applied for the extraction of lignin from ball-milled birch. This made it possible to understand the differences in the extractability of lignin in each extraction step. The fractions were extensively characterized using 1D and 2D nuclear magnetic resonance spectroscopy, size exclusion chromatography, and pyrolysis-gas chromatography-mass spectrometry. This comprehensive characterization highlighted that lignin populations extracted by warm water, alkali, and ionic liquid/ethanol diverged in structural features including subunit composition, interunit linkage content, and the abundance of oxidized moieties. Moreover, ether- and ester-type lignin-carbohydrate complexes were identified in the different extracts. Irrespective of whether natively present in the wood or artificially formed during extraction, these complexes play an important role in the extractability of lignin from ball-milled hardwood. Our results contribute to the further improvement of lignin extraction strategies, for both understanding lignin as present in the lignocellulosic matrix and for dedicated lignin valorization efforts.

Application of 2D NMR Spectroscopy in Combination with Chemometric Tools for Classification of Natural Lignins

Lignin is considered a promising renewable source of valuable chemical compounds and a feedstock for the production of various materials. Its suitability for certain directions of processing is determined by the chemical structure of its macromolecules. Its formation depends on botanical origin, isolation procedure and other factors. Due to the complexity of the chemical composition, revealing the structural differences between lignins of various origins is a challenging task and requires the use of the most informative methods for obtaining and processing data. In the present study, a combination of two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy and multivariate analysis of heteronuclear single quantum coherence (HSQC) spectra is proposed. Principal component analysis and hierarchical cluster analysis techniques demonstrated the possibility to effectively classify lignins at the level of belonging to classes and families of plants, and in some cases individual species, with an error rate for data classification of 2.3%. The reverse transformation of loading plots into the corresponding HSQC loading spectra allowed for structural information to be obtained about the latent components of lignins and their structural fragments (biomarkers) responsible for certain differences. As a result of the analysis of 34 coniferous, deciduous, and herbaceous lignins, 10 groups of key substructures were established. In addition to syringyl, guaiacyl, and p-hydroxyphenyl monomeric units, they include various terminal substructures: dihydroconiferyl alcohol, balanopholin, cinnamic acids, and tricin. It was shown that, in some cases, the substructures formed during the partial destruction of biopolymer macromolecules also have a significant effect on the classification of lignins of various origins.

Encapsulation of AgNPs in a Lignin Isocyanate Film: Characterization and Antimicrobial Properties

Lignin isolated from agricultural residues is a promising alternative for petroleum-based polymers as feedstocks in development of antimicrobial materials. A polymer blend based on silver nanoparticles and lignin-toluene diisocyanate film (AgNPs-Lg-TDIs) was generated from organosolv lignin and silver nanoparticles (AgNPs). Lignin was isolated from Parthenium hysterophorus using acidified methanol and used to synthesize lignin capped silver nanoparticles. Lignin-toluene diisocyanate film (Lg-TDI) was prepared by treating lignin (Lg) with toluene diisocyanate (TDI) followed by solvent casting to form films. Functional groups present and thermal properties of the films were evaluated using Fourier-transform infrared spectrophotometry (FT-IR), thermal gravimetry (TGA), and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM), UV-visible spectrophotometry (UV-Vis), and Powder X-ray diffractometry (XRD) were used to assess the morphology, optical properties, and crystallinity of the films. Embedding AgNPs in the Lg-TDI films increased the thermal stability and the residual ash during thermal analysis, and the presence of powder diffraction peaks at 2θ = 20, 38, 44, 55, and 58⁰ in the films correspond to lignin and silver crystal planes (111). SEM micrographs of the films revealed the presence of AgNPs in the TDI matrix with variable sizes of between 50 to 250 nm. The doped films had a UV radiation cut-off at 400 nm as compared to that of undoped films, but they did not exhibit significant antimicrobial activity against selected microorganisms.

More effective application of biochar-based immobilization technology in the environment: Understanding the role of biochar

In recent years, biochar-based immobilization technology (BIT) has been widely used to treat different environmental issues because of its cost-effectiveness and high removal performance. However, the complexity of the real environment is always ignored, which hinders the transfer of the BIT from lab-scale to commercial applications. Therefore, in this review, the analysis is performed separately on the internal side of the BIT (microbial fixation and growth) and on the external side of the BIT (function) to achieve effective BIT performance. Importantly, the internal two stages of BIT have been discussed concisely. Further, the usage of BIT in different areas is summarized precisely. Notably, the key impacts were systemically analyzed during BIT applications including environmental conditions and biochar types. Finally, the suggestions and perspectives are elucidated to solve current issues regarding BIT.

Evaluating the Impact of Cellulose Extraction via Traditional and Ionosolv Pretreatments from Domestic Matchstick Waste on the Properties of Carboxymethyl Cellulose

Carboxymethyl cellulose (CMC) is a hydrophilic derivative of cellulose whose large volumes have been used in textile processing, protective coatings, detergents, papers, and drilling fluids, while cellulose gum, which is the purified form of CMC, has extensive applications in food, cosmetic, and pharmaceutical industries. Therefore, this work reflects the production of CMC by extracting cellulose with traditional and ionosolv methods from domestic matchstick waste, providing an in-depth view of the overall process where two different kinds of cellulose were obtained from two different pretreatments, and the influence of cellulose on the profile of CMC was checked. All of the procedures have been performed under optimized conditions to reduce the cost and maximize the productiveness. The results depict that cellulose extracted by the ionosolv method using a protic ionic liquid, tetramethylguanidinium hydrogen sulfate (TMG-HSO₄), is more degraded than that extracted by the traditional sulfide method using sodium sulfide (Na₂S) and sodium hydroxide (NaOH). Thus, the produced CMC-2 via ionic liquid-extracted cellulose has more yield, DS (2.3), purity (98.5%), and solubility with less salt and moisture contents than CMC-1 produced by the conventional method due to an effective substitution of the hydroxyl group by the carboxymethyl group. Further, instrumental analyses like FTIR, XRD, ¹H NMR, ¹³C NMR, and SEM emphasize the results that CMC-2 has more reduction of the hydroxyl peak in FTIR, a more amorphous structure in XRD, intense peaks in NMR, and the roughness of the surface in SEM.

Journey of lignin from a roadblock to bridge for lignocellulose biorefineries: A comprehensive review

The grave concerns arisen as a result of environmental pollution and diminishing fossil fuel reserves in the 21st century have shifted the focus on the use of sustainable and environment friendly alternative resources. Lignocellulosic biomass constituted by cellulose, hemicellulose and lignin is an abundantly available natural bioresource. Lignin, a natural biopolymer has over the years gained much importance as a high value material with commercial importance. The present review provides an in-depth knowledge on the journey of lignin from being considered a roadblock to a bridge connecting diverse industries with widescale applications. The successful valorization of lignin for the production of bio-based platform chemicals and fuels has been the subject of intensive investigation. A deeper understanding of lignin characteristics and factors governing the biomass conversion into valuable products can support improved biomass consumption. The components of lignocellulosic biomass might be totally transformed into a variety of value-added products with the improvements in bioprocess techniques that valorize lignin. In this review, the recent advances in the lignin extraction and depolymerization methods that may help in achieving the cost-economics of the bioprocess are summarized and compared. The industrial potential of lignin-derived products such as aromatics, biopolymers, biofuels and agrochemicals are also outlined. Additionally, assessment of the recent research trends in lignin valorization into value-added chemicals has been done and present scenario of technological-industrial applications of lignin with economic perspectives is highlighted.

Relationship between Structure and Properties of Nonstoichiometric Protic Ionic Liquids: n-Butylammonium Butyrate System

Nonstoichiometric protic ionic liquids have drawn much attention in applications, including fuel cells, batteries, and reaction media. An understanding of the relationship between their structure and properties is instructive for further applications. However, there are only a few studies on nonstoichiometric protic ionic liquids. Herein, the density, viscosity, and conductivity of nonstoichiometric n-butylammonium butyrate protic ionic liquids were measured, and we used small/wide-angle scattering (S/WAXS), electron paramagnetic resonance (EPR), and molecular dynamics (MD) simulation to explore the effect of mesostructure on their properties. It is found that the hydrogen bonds drive excess N-butyric acid (PrCOOH) molecules to wrap around ion clusters, resulting in the higher density and viscosity of PrCOOH-rich PILs. The microenvironments around various radicals differ significantly in BuNH₂-rich and PrCOOH-rich PILs because of the distinct molecular arrangements. This research provided a link between the physicochemical properties and structures of nonstoichiometric PILs, which is essential for their applications in electrolytes and organic reactions.

Applications of Ionic Liquids in Carboxylic Acids Separation

Ionic liquids (ILs) are considered a green viable organic solvent substitute for use in the extraction and purification of biosynthetic products (derived from biomass-solid/liquid extraction, or obtained through fermentation-liquid/liquid extraction). In this review, we analyzed the ionic liquids (greener alternative for volatile organic media in chemical separation processes) as solvents for extraction (physical and reactive) and pertraction (extraction and transport through liquid membranes) in the downstream part of organic acids production, focusing on current advances and future trends of ILs in the fields of promoting environmentally friendly products separation.

Spatio-Temporal Modification of Lignin Biosynthesis in Plants: A Promising Strategy for Lignocellulose Improvement and Lignin Valorization

Lignin is essential for plant growth, structural integrity, biotic/abiotic stress resistance, and water transport. Besides, lignin constitutes 10–30% of lignocellulosic biomass and is difficult to utilize for biofuel production. Over the past few decades, extensive research has uncovered numerous metabolic pathways and genes involved in lignin biosynthesis, several of which have been highlighted as the primary targets for genetic manipulation. However, direct manipulation of lignin biosynthesis is often associated with unexpected abnormalities in plant growth and development for unknown causes, thus limiting the usefulness of genetic engineering for biomass production and utilization. Recent advances in understanding the complex regulatory mechanisms of lignin biosynthesis have revealed new avenues for spatial and temporal modification of lignin in lignocellulosic plants that avoid growth abnormalities. This review explores recent work on utilizing specific transcriptional regulators to modify lignin biosynthesis at both tissue and cellular levels, focusing on using specific promoters paired with functional or regulatory genes to precisely control lignin synthesis and achieve biomass production with desired properties. Further advances in designing more appropriate promoters and other regulators will increase our capacity to modulate lignin content and structure in plants, thus setting the stage for high-value utilization of lignin in the future.