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Technical lignins are bulk feedstocks. They are generated as byproducts from pulping or cellulosic ethanol production. As lignin undergoes significant structural changes as a result of chemical and physical treatments, all technical lignins are unique in terms of chemical structure, molecular weight, polydispersity, and impurity profile.
Kraft lign...
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The development of economically viable biorefineries for the transformation of lignocellulose into sustainable biofuels, chemicals and materials requires effective valorization of lignin. The high solubility of lignocelluloses and lignin in ionic liquids has created new probabilities, which renders the essential significance of understanding the ce...
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... Lignin is a complex aromatic biopolymer comprising up to 30 wt% of lignocellulosic biomass, and has significant potential as a renewable feedstock for the production of chemicals, fuels, and functional materials [1,2]. Lignin is also a major byproduct in the pulp and paper and cellulosic ethanol industries, where the bulk raw material is referred to as technical lignin [3,4]. The highly heterogeneous nature of lignin makes its valorization challenging and, as a result, Omar Y. Abdelaziz omar.abdelaziz@chemeng.lth.se an energy-efficient means of lignin conversion, providing targeted functional chemicals, including high-value chemicals such as aromatic aldehydes, aromatic acids, and alkyl carboxylic acids [14,15]. ...
Zirconia-supported vanadium–copper catalysts (VCux:yZr) were used for the oxidative depolymerization of softwood LignoBoost Kraft lignin (LB). Various VCux:yZr catalysts were prepared (x:y = 0:1, 1:4, 1:2, 3:4, 1:1, and 1:0) by incipient wetness impregnation, and reactions were performed in alkaline water at 150 °C under an O2 pressure of 5 bar for 10 min. ¹H–¹³C HSQC NMR spectroscopy was used for product identification and quantification. The most promising catalyst was VCu1:2Zr, giving a total monomer yield of 9 wt% and the highest selectivity for vanillin (59%). This catalyst was characterized before and after use by N2 physisorption, XRD, TGA, SEM-EDS, and XPS. Cleavage of the main interunit linkages in LB, including the β-O-4 bonds and recalcitrant C–C bonds, was also observed. The findings of this study demonstrate the potential of the V–Cu/ZrO2 catalyst system in the production of value-added aromatics from technical lignin under relatively mild conditions. This would contribute to the more sustainable use of an underutilized side-stream in forest-based industries, provided catalyst reuse can be successfully demonstrated.
... Conversely, enzymatic biotransformation of kraft lignin has been documented extensively in the last two decades, enumerating the transformed low molecular weight (LMW) compounds after treatment either through enzyme or LME-producing species under controlled conditions [8,[58][59][60][61][62][63][64]. As a byproduct, an enormous quantity of technical lignin serves as a rich source of aromatic compounds that may be further valorized in the synthesis of value-added compound [65][66][67][68][69]. Much effort has been made to develop novel techniques for extracting and converting lignin into value-added compounds, including lipids, polyhydroxyalkanoates (PHAs), vanillin, and other aromatic monomers with the goal of lowering the total costs of the biorefinery process [10,[70][71][72]. ...
Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.
... Pretreatment objectives are disruption of plant cells, separating hemicellulos and lignin from cellulose, decreasing cellulose crystallinity, and minimizing fermentation inhibitor formation (Li and Takkellapati, 2018). The lignocellulosic biomass delignification was investigated in many studies. ...
... The average molecular weight determined was 5.900 g/ mol according to PS standards, and polydispersion (Mw/Mn) was 2.20. Based on literature data, the molecular weight of lignin is within the range of 4600-8000 g/mol, which is close to the values obtained in the analysis of molar masses of lignin in softwood [20,21]. ...
In response to the trend toward sustainable management of by-products from the pulp and paper industry as well as plant waste, practical and economical methods are being developed to use them in a way that does not pose a threat to the environment. The main aim of the research was to study the possibility of using lignin and plant biomass as biosorbents for the removal of zinc ions from aqueous solutions. The secondary aim was to build an optimal multilayer system made of biosorbents selected during the research in order to obtain the highest sorption efficiency and to determine the best conditions of the sorption process. The effectiveness of zinc ion sorption was assessed using an appropriate combination of sorbents such as lignin, oat bran, rice husk, chitosan, pectin, sodium alginate, pine bark, coconut fiber and activated carbon, selected on the basis of literature data and the preliminary results of tests carried out using FTIR and AAS. The main component of the sorption system was lignin separated from black liquor. Results indicate that the best Zn sorption system was based on coconut fiber, lignin, and pine bark, for which the maximum sorption efficiency was 95%. The research also showed that the increase in the process temperature, the mass of biosorbents used and the alkaline pH are the factors that increase the efficiency of the sorption. It can be concluded that lignin and plant biomass can be used as ecological sorbents of zinc ions from water solutions. They are safe for the environment, produced from renewable sources, and are by-products or waste materials, which is part of the sustainable development and circular economy currently promoted in the EU.
... Owing to its relative inexpensiveness and high efficiency for breaking linkages in lignin (e.g., C-O-C and C-C), catalytic chemical conversion with the assistance of various catalysts is becoming a very competitive method for the generation of bio-energy and valuable chemicals [12]. Fermentation 2023, 9, 386 3 of 21 oxidation, hydroxylation of aromatic rings, ring-opening reactions, and demethylation [15]. Oxidative depolymerization of lignin produces aromatic aldehydes (e.g., vanillin and syringaldehyde) and their acids (e.g., vanillic acid and syringic acid) [14]. ...
... LD by oxidation is decomposed by various oxidizing agents (e.g., oxygen, nitrobenzene, metallic oxide, hydrogen peroxide, etc.) to produce phenolic derivatives [14]. Electron transfer and extraction of hydrogen atoms from lignin usually occur in the reaction, which leads to a series of subsequent reactions, such as phenol oxidation, benzylic oxidation, hydroxylation of aromatic rings, ring-opening reactions, and demethylation [15]. Oxidative depolymerization of lignin produces aromatic aldehydes (e.g., vanillin and syringaldehyde) and their acids (e.g., vanillic acid and syringic acid) [14]. ...
Lignin is a type of natural aromatic material with potential application prospects obtained from lignocellulosic biomass. Recently, the valorization of lignin has received increasing attention from both industry and academia. However, there is still a challenge in the efficient valorization of lignin due to the complexity and stability of the lignin structure. Recent work has been focused on the catalytic depolymerization of lignin to explore a promising and efficient way to valorize lignin into chemicals with high value and biofuels. Considerable research has focused on catalysts, solvents, and reaction parameters during the lignin depolymerization process, which significantly affects product distribution and productivity. Thus, in a catalytic depolymerization process, both catalysts and solvents have a significant influence on the depolymerization effect. This review article assesses the current status of the catalytic hydrogenolysis of lignin, mainly focusing on the solvents and catalysts during the reaction. First, various solvents applied in the lignin depolymerization reactions are extensively overviewed. Second, the recent progress of metal catalysts as well as their supports is summarized. Furthermore, a discussion of the challenges and prospects in this area is included.
... This method is popular for breaking down lignin fractions [24]. The benefits of this method include obtaining lignin with a low molecular weight that is free of sulfur, and its application can be improved through fractionation or chemical modification [25], but organosolv fractionation is laborious work [26]; hence, acid and base deposition methods are more feasible. However, this method depends on the pH of the liquor, residence time, and temperature [22]. ...
Black liquor is obtained as a by-product of the pulping process, which is used to convert biomass into pulp by removing lignin, hemicelluloses and other extractives from wood to free cellulose fibers. Lignin represents a major constituent in black liquor, with quantities varying from 20% to 30%, of which a very low share is used for manufacturing value-added products, while the rest is mainly burned for energy purposes, thus underestimating its great potential as a raw material. Therefore, it is essential to establish new isolation and extraction methods to increase lignin valorization in the development of bio-based chemicals. The aim of this research work was to determine the effect of KOH or ethanol concentration as an isolation agent on lignin yields and the chemical characteristics of lignin isolated from formacell black liquor of oil palm empty fruit bunch (OPEFB). Isolation of lignin was carried out using KOH with various concentrations ranging from 5% to 15% (w/v). Ethanol was also used to precipitate lignin from black liquor at concentrations varying from 5% to 30% (v/v). The results obtained showed that the addition of KOH solution at 12.5% and 15% concentrations resulted in better lignin yield and chemical properties of lignin, i.e., pH values of 3.86 and 4.27, lignin yield of 12.78% and 14.95%, methoxyl content of 11.33% and 10.13%, and lignin equivalent weights of 476.25 and 427.03, respectively. Due to its phenolic structure and rich functional groups that are favorable for modifications, lignin has the potential to be used as a green additive in the development of advanced biocomposite products in various applications to replace current fossil fuel-based material, ranging from fillers, fire retardants, formaldehyde scavengers, carbon fibers, aerogels, and wood adhesives.
... This means they may not be easily precipitated by acidifying the liquor [55]. The average molecular weight of hardwood lignosulfonate is 7-11 kDa, while the molecular weight of softwood lignosulfonate is 35-57 kDa [56]. ...
... The main problems encountered are subsequent removal of amine from the product, the formation of NaCl during re-extraction, foam and emulsion problems, and a time-consuming separation procedure [57]. Consecutive ultrafiltration steps with different molecular weight cutoff (MWCO) membranes are used to separate impurities as well as high molecular weight lignosulfonates [56]. Membrane-based filtration holds great promise for an economical and environmentally sustainable recovery of highly pure lignin [58]. ...
Lignocellulosic biomass is one of the most abundant bioresources on Earth. Over recent decades, various valorisation techniques have been developed to produce value-added products from the cellulosic and hemicellulosic fractions of this biomass. Lignin is the third major component accounting for 10–30% (w/w). However, it currently remains a largely unused fraction due to its recalcitrance and complex structure. The increase in the global demand for lignocellulosic biomass, for energy and chemical production, is increasing the amount of waste lignin available. Approaches to date for valorizing this renewable but heterogeneous chemical resource have mainly focused on production of materials and fine chemicals. Greater value could be gained by developing higher value pharmaceutical applications which would help to improve integrated biorefinery economics. In this review, different lignin extraction methods, such as organosolv and ionic liquid, and the properties and potential of the extracted chemical building blocks are first summarized with respect to pharmaceutical use. The review then discusses the many recent advances made regarding the medical or therapeutic potential of lignin-derived materials such as antimicrobial, antiviral, and antitumor compounds and in controlled drug delivery. The aim is to draw out the link between the source and the processing of the biomass and potential clinical applications. We then highlight four key areas for future research if therapeutic applications of lignin-derived products are to become commercially viable. These relate to the availability and processing of lignocellulosic biomass, technologies for the purification of specific compounds, enhancements in process yield, and progression to human clinical trials.
... To utilize lignin, it needs to be isolated from a biomass by using various processes [8]. Several extraction and delignification processes with acid-or alkali-catalyzed mechanisms are used to obtain so-called technical lignins [9][10][11][12]. Technical lignins can be divided into two groups. ...
The work deals with the application of biopolymer fillers in rubber formulations. Calcium lignosulfonate was incorporated into styrene–butadiene rubber and acrylonitrile–butadiene rubber in a constant amount of 30 phr. Glycerol in a concentration scale ranging from 5 to 20 phr was used as a plasticizer for rubber formulations. For the cross-linking of the compounds, a sulfur-based curing system was used. The study was focused on the investigation of glycerol in the curing process; the viscosity of rubber compounds; and the cross-link density, morphology, physical–mechanical, and dynamic mechanical properties of vulcanizates. The study revealed that the application of glycerol as a plasticizer resulted in a reduction in the rubber compounds’ viscosity and contributed to the better dispersion and distribution of the filler within the rubber matrices. The mutual adhesion and compatibility between the filler and the rubber matrices were improved, which resulted in the significant enhancement of tensile characteristics. The main output of the work is the knowledge that the improvement of the physical–mechanical properties of biopolymer-filled vulcanizates can be easily obtained via the simple addition of a very cheap and environmentally friendly plasticizer into rubber compounds during their processing without additional treatments or procedures. The enhancement of the physical–mechanical properties of rubber compounds filled with biopolymers might contribute to the broadening of their potential applications. Moreover, the price of the final rubber articles could be reduced, and more pronounced ecological aspects could also be emphasized.
... This results in a recalcitrant heterogeneous polymer, the most abundant, one-of-a-kind, potentially renewable source for aromatic compounds [11]. Many different technical lignin types are available, including lignin from pulping streams such as Kraft lignin, soda lignin or lignosulfonates and sugar-based biorefinery lignin such as wood hydrolysis lignin (HL) [5,12]. ...
In the forest biorefinery, hydrolysis lignin (HL) is often dissolved with high concentration NaOH solution, followed by acid precipitation to obtain purified HL. For the first time, this study evaluates the effect of ultrasound (US) on the dissolution of industrially produced HL in aqueous NaOH solutions and the acid precipitation yield of HL. The solubility of HL in mild aqueous NaOH solutions was studied with and without US treatment at 20 kHz concerning the solid-to-liquid ratio, molecular weight of dissolved fractions and structural changes in dissolved HL. Results showed that the solubility of HL at 25 °C was strongly dependent on NaOH concentration. However, the US treatment significantly improved the solubility of HL, reaching a solubility plateau at 0.1 NaOH/HL ratio. US treatment enhanced the solubilization of HL molecules with higher MW compared to conventional mixing. The increase of HL solubility was up to 30% and the recovery yield of purified lignin with acid precipitation was 37% higher in dilute NaOH solution. A significant result was that the Mw of dissolved HL in homogeneous alkali solutions decreased with US treatment. SEC, HSQC and ³¹P NMR analyses of dissolved HL characteristics showed that both, the mechanoacoustic and sonochemical solubilization pathways contribute to the dissolution process. However, US does not cause major changes in the HL structure compared to the native lignin. Indeed, US technology has the potential to advance the dissolution and purification of HL in biorefineries by reducing the amount of chemicals required; thus, more controlled and environmentally friendly conditions can be used in HL valorization.
... Due to cellulose's biocompatibility, hydrophilicity, and reasonably excellent durability, the resultant membranes have a wide range of potential uses. The hydrophilicity of the cellulose membrane makes it a practical choice for a variety of applications, including the purification of wastewater from the paper and pulp industry and biorefinery streams (Li and Takkellapati, 2018). ...
Solid waste mismanagement is a global issue caused by population growth, industrialization, and daily human activity. Currently, the majority of trash produced is either dumped in landfills in affluent countries or open pits in poor nations. In addition to necessitating a great deal of land area, landfilling and open dumping may cause other environmental difficulties. In fact, solid wastes may provide many chances for reusing as raw materials for the creation of useful, high-value goods in response to the need for a circular economy. Due to their cheap prices, possible high removal efficiency for pollutants, renewable and sustainable qualities, solid waste-derived membranes have gained considerable research attention as a waste-to-resource solution for a variety of water treatment applications. The fabrication and applications of economical membranes manufactured from natural resources have been reported. However, comprehensive reviews that discuss the fabrication, properties and potential applications waste-generated membranes are still limited. The features and material recoverable resources for membrane production are emphasized in this study. Based on biopolymers, plastics, and inorganics recycled materials, a summary of membrane manufacturing and performance using recoverable resources for liquid separation applications is provided. There are many prospects in this fascinating field since waste-derived membrane for water filtration is a new technology. For converting solid wastes into useful membrane products for water treatment, this evaluation offers crucial advice.
