"Waste to Wealth": Lignin as a Renewable Building Block for Energy Harvesting/Storage and Environmental Remediation

Lignin-Based Photothermal Materials: Bridging Sustainability and High-Efficiency Energy Conversion

Photothermal materials can effectively absorb light and convert it into heat, providing sustainable solutions to mitigate environmental pollution and energy shortages. Compared to traditional photothermal materials, lignin has garnered significant attention due to its wide availability, low cost, biocompatibility, renewability, and sustainability. Consequently, lignin-based materials are considered ideal candidates for the development of eco-friendly photothermal systems, aligning well with the increasing demand for sustainable energy solutions. This review discusses the potential of lignin-based photothermal materials, highlighting their unique molecular structure and the photothermal properties imparted by their aromatic rings, which facilitate effective energy conversion through non-radiative vibrational relaxation. Discussed the latest advances in the applications of lignin photothermal materials in photothermal drive, solar desalination, and biomedicine. Despite the significant potential of lignin, challenges such as structural variability, long-term stability, and scalability remain critical. This paper integrates recent progress and proposes strategies to optimize the photothermal performance of lignin-based materials, while emphasizing important directions for sustainable development, thereby providing a roadmap to fully realize the potential of lignin in next-generation green technologies.

Extracting Lignin with Superior Photothermal Performance from Wood in Molten Salt Hydrate for Preparation of a Solar-Driven Gradient Evaporator

Developing sustainable solar-driven evaporators requires efficient photothermal materials and rational structural design. This study presents a green strategy for extracting lignin with enhanced photothermal performance from wood using molten salt hydrate (MSH) and citric acid under mild conditions. Systematic investigations reveal that elevated reaction temperatures (170 °C) promoted lignin depolymerization (Mw = 1206) and increased phenolic hydroxyl content (3.5 mmol g-1), enhancing π-π stacking interactions to achieve a photothermal conversion efficiency of 36.31%. Structural analyses through 2D-HSQC NMR confirm βO4 bond cleavage and demethylation, while fluorescence quenching validates reduced radiative losses. Leveraging this lignin, a gradient evaporator is fabricated by integrating polyvinyl alcohol (PVA)-modified melamine foam (MF) with a hydrophobic lignin-polyvinylidene fluoride (PVDF) photothermal layer. The evaporator exhibits hierarchical wettability, enabling gravity-guided water transport. It demonstrates robust performance in hypersaline water (1.85 kg m-2 h-1 for 10.5 wt.% brine) and dye removal (>99.98% rejection) under 0.1 W cm-2 sun irradiation and environmental heat harvesting. Additionally, lignin-coated thermoelectric devices generate stable power (27.69 W m-2) by solar-thermal conversion. This work provides an eco-friendly pathway for lignin valorization and scalable solar evaporation systems, addressing energy-water challenges through biomass resource utilization.

Ultra-strong and solvent-resistant lignin-based non-isocyanate polyurethane adhesives: One-pot strategy toward versatile bonding

Isocyanate-free polyurethane adhesives have attracted considerable attention as a promising environmentally friendly alternative. However, their progress has been hindered by insufficient bonding performance and weak solvent resistance, as well as the laborious synthesis processes involved. Herein, we successfully synthesized a high-performance lignin-based non-isocyanate adhesives (LNIPUs-G) through a one-pot strategy that combines the polycondensation of carbonate groups with polyether amines and aldehyde-amine chemistry. The former aspect circumvents the limitations associated with cyclic carbonate polyaddition while providing a molecular composition containing both rigid and flexible segments along with a high-density polar groups. Concurrently, the rapid hyperbranching process in the latter aspect significantly contributes to achieving a robust crosslinked network. As a result, the LNIPUs-G demonstrates exceptional resistance to boiling water with bond strengths of up to 1.32 MPa when applied to plywood, surpassing previously reported bio-based adhesives. Moreover, the adhesive exhibits remarkable versatility across a wide range of substrates including steel, iron, copper, carbon fiber reinforced composites, ceramics, aluminum, wood, and glass. Additionally, the adhesive has excellent resistance to an extensive range of organic solvents. Life cycle assessment (LCA) results demonstrate that the high-performance and cost-effective LNIPUs-G is expected to disrupt the dominance of bulk formaldehyde- and isocyanate-based adhesives industry.

Recent progresses in bentonite/lignin or polysaccharide composites for sustainable water treatment

Today, with the growth of the human population, industrial activities have also increased. Different industries such as painting, cosmetics, leather, etc. have broadly developed, and as a result, they also produce a lot of pollutants. These pollutants can enter the environment and pollute water, air, and soil. Organic dyes, nitro compounds, drug residues, pesticides and herbicides are pollutants that should be removed from the environment. Natural polymers or biopolymers are important types of organic materials that are broadly applied for different applications. Among them, polysaccharides and lignin, which are two types of biopolymers, have attracted much consideration owing to their advantages such as biocompatibility, environmental friendly, safety, availability, etc. Polysaccharides include cellulose, gum, starch, alginate (Alg), chitin, and chitosan (CS). On the other hand, bentonite is one of the types of clays, which owing to their properties like large specific surface area, adsorption performance, naturally available, etc., have drawn the interest of many researchers. As a result, the synthesis of a composite including polysaccharide/lignin and bentonite can be very efficient for different applications, especially environmental ones. In this review, we instigated the preparation of these composites as well as the removal performance of them. In fact, we reported recent advancements in the synthesis of lignin- and polysaccharide-bentonite composites for the removal of diverse kinds of contaminants like organic dyes, nitro compounds, and hazardous materials.

Advanced Triboelectric Applications of Biomass-Derived Materials: A Comprehensive Review

The utilization of triboelectric materials has gained considerable attention in recent years, offering a sustainable approach to energy harvesting and sensing technologies. Biomass-derived materials, owing to their abundance, renewability, and biocompatibility, offer promising avenues for enhancing the performance and versatility of triboelectric devices. This paper explores the synthesis and characterization of biomass-derived materials, their integration into triboelectric nanogenerators (TENGs), and their applications in energy harvesting, self-powered sensors, and environmental monitoring. This review presents an overview of the emerging field of advanced triboelectric applications that utilize the unique properties of biomass-derived materials. Additionally, it addresses the challenges and opportunities in employing biomass-derived materials for triboelectric applications, emphasizing the potential for sustainable and eco-friendly energy solutions.

Revealing the structural changes of lignin in Chinese quince (Chaenomeles sinensis) fruit as it matures

Chinese quince fruits (Chaenomeles sinensis) contain substantial amounts of lignin; however, the exact structure of lignin remains to be investigated. In this study, milled wood lignins (Milled wood lignin (MWL)-1, MWL-2, MWL-3, MWL-4, MWL-5, and MWL-6) were extracted from fruits harvested once a month from May to October 2019 to investigate their structural evolution during fruit growth. The samples were characterized via High-performance anion exchange chromatography (HPAEC), Fourier transform-infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermogravimetric (TGA), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and NMR (2D-heteronuclear single quantum coherence (HSQC) and 31P). The MWL samples in all fruit growth stages were GS-type lignin and lignin core undergoing minimal alterations during fruit development. The predominant linkage in the lignin structure was β-O-4', followed by β-β' and β-5'. Galactose and glucose were the main monosaccharides associated with MWL. In MWL-6, the lignin exhibited the highest homogeneity and thermal stability. As the fruit matured, a gradual increase in the β-O-4' proportion and the ratio of S/G was observed. The results provide comprehensive characterization of the cell wall lignin of quince fruit as it matures. This study could inspire innovative applications of quince fruit lignin and provide the optimal harvest time for lignin utilization.

Shrimp Waste Upcycling: Unveiling the Potential of Polysaccharides, Proteins, Carotenoids, and Fatty Acids with Emphasis on Extraction Techniques and Bioactive Properties

Shrimp processing generates substantial waste, which is rich in valuable components such as polysaccharides, proteins, carotenoids, and fatty acids. This review provides a comprehensive overview of the valorization of shrimp waste, mainly shrimp shells, focusing on extraction methods, bioactivities, and potential applications of these bioactive compounds. Various extraction techniques, including chemical extraction, microbial fermentation, enzyme-assisted extraction, microwave-assisted extraction, ultrasound-assisted extraction, and pressurized techniques are discussed, highlighting their efficacy in isolating polysaccharides, proteins, carotenoids, and fatty acids from shrimp waste. Additionally, the bioactivities associated with these compounds, such as antioxidant, antimicrobial, anti-inflammatory, and antitumor properties, among others, are elucidated, underscoring their potential in pharmaceutical, nutraceutical, and cosmeceutical applications. Furthermore, the review explores current and potential utilization avenues for these bioactive compounds, emphasizing the importance of sustainable resource management and circular economy principles in maximizing the value of shrimp waste. Overall, this review paper aims to provide insights into the multifaceted aspects of shrimp waste valorization, offering valuable information for researchers, industries, and policymakers interested in sustainable resource utilization and waste-management strategies.

Green and sustainable production of high-purity lignin microparticles with well-preserved substructure and enhanced anti-UV/oxidant activity using peroxide-promoted alkaline deep eutectic solvent

Deep eutectic solvents (DESs) have emerged as promising and eco-friendly solvents for the efficient extraction of lignin from biomass due to their low cost and environmental benefits. Nevertheless, the prevalent use of acidic DESs in lignin extraction often results in excessive depolymerization and recondensation of lignin, thereby impeding its downstream applications. In this study, we developed a range of alkaline DESs (ADESs), both pure and peroxide-containing, for the extraction of high-quality lignin from bamboo. Moreover, carbon dioxide (CO2) was employed for the precipitation and regeneration of the extracted lignin. The obtained lignin fractions were comprehensively characterized in terms of yield, purity, morphology, solubility, structural features, and anti-UV/oxidant activity. The results showed that the monoethanolamine-based ADES demonstrated superior performance among the pure ADESs. Structural analysis confirmed the well-preserved substructures of lignin fractions obtained using ADESs, with β-O-4 bond retention ranging from 49.8 % to 68.4 %. The incorporation of a suitable amount of peroxide improved lignin yield, morphology, solubility, and anti-UV/oxidant activity. Additionally, the anti-UV/oxidant activity of lignin exhibited a positive correlation with its phenolic hydroxyl content. This study provides a valuable reference for the green and sustainable production and valorization of lignin within the existing biorefinery framework.

Sustainable Synthesis of Metal-Doped Lignin-Derived Electrospun Carbon Fibers for the Development of ORR Electrocatalysts

The aim of this work is to establish the Oxygen Reduction Reaction (ORR) activity of self-standing electrospun carbon fiber catalysts obtained from different metallic salt/lignin solutions. Through a single-step electrospinning technique, freestanding carbon fiber (CF) electrodes embedded with various metal nanoparticles (Co, Fe, Pt, and Pd), with 8-16 wt% loadings, were prepared using organosolv lignin as the initial material. These fibers were formed from a solution of lignin and ethanol, into which the metallic salt precursors were introduced, without additives or the use of toxic reagents. The resulting non-woven cloths were thermostabilized in air and then carbonized at 900 °C. The presence of metals led to varying degrees of porosity development during carbonization, improving the accessibility of the electrolyte to active sites. The obtained Pt and Pd metal-loaded carbon fibers showed high nanoparticle dispersion. The performance of the electrocatalyst for the oxygen reduction reaction was assessed in alkaline and acidic electrolytes and compared to establish which metals were the most suitable for producing carbon fibers with the highest electrocatalytic activity. In accordance with their superior dispersion and balanced pore size distribution, the carbon fibers loaded with 8 wt% palladium showed the best ORR activity, with onset potentials of 0.97 and 0.95 V in alkaline and acid media, respectively. In addition, this electrocatalyst exhibits good stability and selectivity for the four-electron energy pathway while using lower metal loadings compared to commercial catalysts.

Fabrication of Graphitized Carbon Fibers from Fusible Lignin and Their Application in Supercapacitors

Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation at a relatively low temperature of 1200 °C but also avoids additional treatments used in conventional carbon fiber production. The LCFs were then used as electrode materials in a supercapacitor assembly. Electrochemical measurements confirmed that LCF-0.4, a sample with a relatively low specific surface area of 89.9 m2 g-1, exhibited the best electrochemical properties. The supercapacitor with LCF-0.4 had a specific capacitance of 10.7 F g-1 at 0.5 A g-1, a power density of 869.5 W kg-1, an energy density of 15.7 Wh kg-1, and a capacitance retention of 100% after 1500 cycles, even without activation.

Structure regulated 3D flower-like lignin-based anode material for lithium-ion batteries and its storage kinetics

As a green sustainable material, lignin-derived porous carbon (LPC) exhibits great application potential when used as the anode material in lithium-ion batteries (LIBs), but the applications are limited by the heterogeneity of the lignin precursor. Therefore, it is crucial to reveal the relationship among lignin properties, porous carbon structure and the kinetics of lithium-ion storage. Herein, LPCs from fractionated lignin have been prepared by an eco-friendly and recyclable activator. The structure of the LPCs was regulated by adjusting the molecular weight, linkage abundance and glass transition temperature (T_g) of lignin macromolecules. As the anode material of LIBs, the prepared 3D flower-like LPC_E70 could achieve a reversible capacity of 528 mAh g^-1 at a current density of 0.2 A g^-1 after 200 cycles, 63 % higher than that of commercial graphite. Furthermore, kinetic calculations of lithium-ion storage behavior of LPCs were firstly used to confirm the contribution ratio of diffusion-controlled behavior and capacitive effect. Lignin with a high linkage abundance could yield LPC_E70 with the largest interlayer spacing and specific surface area to maximize lithium-ion storage from both diffusion-controlled and capacitive contributions of specific capacities. This work provides a green, facile and effective pathway for value-added utilization of lignin in LIBs.

High lignin, light-driven shape memory polymers with excellent mechanical performance

With the gradual global standardization of carbon emission policies, the development of renewable resources to replace traditional fossil resources is assuming increasing importance. Lignin is the most abundant natural source of aromatic compounds and has the potential to replace petroleum-based aromatic hydrocarbons. In this work, the rigid benzene ring structure and excellent photothermal properties of lignin were exploited to produce light-driven lignin-based shape memory polymers (ELEPs) that contain high proportions of lignin and have good mechanical properties. Enzymatically hydrolyzed lignin (EL), epoxy soybean oil (ESO) and polyethylene glycol (PEG 400) were copolymerized and cured to form ELEPs, which have a disordered three-dimensional network. An increase in the proportion of EL from 40 to 60 wt% enhanced the mechanical properties, as reflected by an increase in tensile strength from 11.3 to 30.8 MPa and in the glass transition temperature (T_g) from 93 to 115.7 °C. Under simulated solar irradiation (2000 W m^-2), ELEP50, which contains 50 wt% lignin and has a T_g of 105 °C, reached a surface temperature as high as 105 °C and achieved shape memory within 20 s. The shape fixation ratio (R_f) and shape recovery ratio (R_r) were stably >98 % and >97 %, respectively, over eight cycles in a bending-recovery experiment. The unique light-driven shape memory properties of ELEPs provide a method for high value utilization of EL, and the design strategy offers new ideas for producing novel intelligent materials.

Functionalized Alkaline Lignin for Removal of Lead in Aqueous Solution

Lignin, the second most abundant natural polymeric globally, is considered the source of the renewable aromatic compound. It serves as an alternative feedstock for the elaboration of chemicals and polymers. However, even until now, it is still primarily used as a low-value fuel for boilers. In the current research, alkaline lignin was modified and used as an adsorbent for removing lead (Pb) in an aqueous solution. The functionalized alkaline lignin (FAL) was prepared by a Mannich reaction with formaldehyde and dimethylamine, followed by esterification of carbon disulfide. The FAL was characterized using CHN elemental analysis, X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FT-IR) to observe the changes in composition, morphology, and chemical structure. The analysis revealed that alkaline lignin was successfully modified using amine and carbon disulfide. The adsorption study shows that the lead concentration reduced to 93.7% after 2 hours in contact with FAL. The FAL adsorption capacity could obtain 0.44 mmol/g of lead.

Unbiased Photoelectrode Interfaces for Solar Coupling of Lignin Oxidation with Biocatalytic C═C Bond Hydrogenation

The pulp and paper manufacturers generate approximately 50 million metric tons of lignin per annum, most of which has been abandoned or incinerated because of lignin's recalcitrant nature. Here, we report bias-free photoelectrochemical (PEC) oxidation of lignin coupled with asymmetric hydrogenation of C═C bonds. The PEC platform consists of a hematite (α-Fe₂O₃) photoanode and a silicon photovoltaic-wired mesoporous indium tin oxide (Si/mesoITO) photocathode. We substantiate a new function of photoelectroactivated α-Fe₂O₃ to extract electrons from lignin. The extracted electrons are transferred to the Si/mesoITO photocathode for regenerating synthetic nicotinamide cofactor analogues (mNADHs). We demonstrate that the reduction kinetics of mNAD⁺s depend on their reduction peak potentials. The regenerated mNADHs activate ene-reductases from the old yellow enzyme (OYE) family, which catalyze enantioselective reduction of α,β-unsaturated hydrocarbons. This lignin-fueled biocatalytic PEC system exhibits an excellent OYE's turnover frequency and total turnover number for photobiocatalytic trans-hydrogenation through cofactor regeneration. This work presents the first example of PEC regeneration of mNADHs and opens up a sustainable route for bias-free chemical synthesis using renewable lignin waste as an electron feedstock.

Lignin-Induced CaCO3 Vaterite Structure for Biocatalytic Artificial Photosynthesis

The vaterite phase of CaCO₃ exhibits unique characteristics, such as high porosity, surface area, dispersivity, and low specific gravity, but it is the most unstable polymorph. Here, we report lignin-induced stable vaterite as a support matrix for integrated artificial photosynthesis through the encapsulation of key active components such as the photosensitizer (eosin y, EY) and redox enzyme (l-glutamate dehydrogenase, GDH). The lignin-vaterite/EY/GDH photobiocatalytic platform enabled the regeneration of the reduced nicotinamide cofactor under visible light and facilitated the rapid conversion of α-ketoglutarate into l-glutamate (initial conversion rate, 0.41 mM h^-1; turnover frequency, 1060 h^-1; and turnover number, 39,750). The lignin-induced vaterite structure allowed for long-term protection and recycling of the active components while facilitating the photosynthesis reaction due to the redox-active lignin. Succession of stability tests demonstrated a significant improvement of GDH's robustness in the lignin-vaterite structure against harsh environments. This work provides a simple approach for solar-to-chemical conversion using a sustainable, integrated light-harvesting system.

Lignin Derived Porous Carbons: Synthesis Methods and Supercapacitor Applications

Lignin, one of the renewable constituents in natural plant biomasses, holds great potential as a sustainable source of functional carbon materials. Tremendous research efforts have been made on lignin-derived carbon electrodes for rechargeable batteries. However, lignin is considered as one of the most promising carbon precursors for the development of high-performance, low-cost porous carbon electrode materials for supercapacitor applications. Yet, these efforts have not been reviewed in detail in the current literature. This review, therefore, offers a basis for the utilization of lignin as a pivotal precursor for the synthesis of porous carbons for use in supercapacitor electrode applications. Lignin chemistry, the synthesis process of lignin-derived porous carbons, and future directions for developing better porous carbon electrode materials from lignin are systematically reviewed. Technological hurdles and approaches that should be prioritized in future research are presented.

Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Au_f NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Au_f NPs. The optimized L-Au_f (1-5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Au_f (1-5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb²⁺ ions within a short time interval among the various metal ions (Pb²⁺, Fe³⁺, Cu²⁺, Cr⁶⁺, Co²⁺, Ag²⁺, Ca²⁺, Cd²⁺, Ba²⁺, and Hg²⁺). The prominent color change of L-Au_f NPs from red wine to purple indicates the detection of Pb²⁺ ions. This robust characteristic nature of L-Au_f (1-5) NPs can also detect very low concentrations of 1.8 μM in the linear range of 0.1-1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Au_f (1-5) NPs can also be used as effective sensors for the rapid and selective detection of Pb²⁺ ions via the colorimetric analysis using the real environmental samples.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

Lignin biopolymer: the material of choice for advanced lithium-based batteries

Lignin, an aromatic polymer, offers interesting electroactive redox properties and abundant active functional groups. Due to its quinone functionality, it fulfils the requirement of erratic electrical energy storage by only providing adequate charge density. Research on the use of lignin as a renewable material in energy storage applications has been published in the form of reviews and scientific articles. Lignin has been used as a binder, polymer electrolyte and an electrode material, i.e. organic composite electrodes/hybrid lignin-polymer combination in different battery systems depending on the principal charge of quinone and hydroquinone. Furthermore, lignin-derived carbons have gained much popularity. The aim of this review is to depict the meticulous follow-ups of the vital challenges and progress linked to lignin usage in different lithium-based conventional and next-generation batteries as a valuable, ecological and low-cost material. The key factor of this new finding is to open a new path towards sustainable and renewable future lithium-based batteries for practical/industrial applications.

Synthetic lignin-like and degradable nanocarriers

Bio-based lignin-like building blocks were synthesized and transformed into polyurethane nanocarriers by interfacial polymerization in a miniemulsion. The nanocarriers were degradable by fungal enzymes and might be used for agrochemical delivery.

Plant celluloses, hemicelluloses, lignins, and volatile oils for the synthesis of nanoparticles and nanostructured materials

A huge variety of plants are harvested worldwide and their different constituents can be converted into a broad range of bionanomaterials. In parallel, much research effort in materials science and engineering is focused on the formation of nanoparticles and nanostructured materials originating from agricultural residues. Cellulose (40-50%), hemicellulose (20-40%), and lignin (20-30%) represent major plant ingredients and many techniques have been described that separate the main plant components for the synthesis of nanocelluloses, nano-hemicelluloses, and nanolignins with divergent and controllable properties. The minor components, such as essential oils, could also be used to produce non-toxic metal and metal oxide nanoparticles with high bioavailability, biocompatibility, and/or bioactivity. This review describes the chemical structure, the physical and chemical properties of plant cell constituents, different techniques for the synthesis of nanocelluloses, nanohemicelluloses, and nanolignins from various lignocellulose sources and agricultural residues, and the extraction of volatile oils from plants as well as their use in metal and metal oxide nanoparticle production and emulsion preparation. Furthermore, details about the formation of activated carbon nanomaterials by thermal treatment of lignocellulose materials, a few examples of mineral extraction from agriculture waste for nanoparticle fabrication, and the emerging applications of plant-based nanomaterials in different fields, such as biotechnology and medicine, environment protection, environmental remediation, or energy production and storage, are also included. This review also briefly discusses the recent developments and challenges of obtaining nanomaterials from plant residues, and the issues surrounding toxicity and regulation.

Fractionation of lignin using organic solvents: A combined experimental and theoretical study

Refining of industrial lignin to produce homogeneous fractions is essential for high-value applications. However, the understanding of key interactions between a variety of solvents with lignin polymer is still uncertain. In this work, single-step fractionation of industrial hardwood kraft lignin (HKL) using organic solvents of different polarities - ethanol, acetone, diethyl ether and hexane - was investigated by combining an experimental and theoretical approach. Experimental results revealed that higher polarity solvents (ethanol and acetone) exhibited higher solubility yield compared to moderate and low polarity solvents. The chemical differences between lignin fractions were proven by pyrolysis gas chromatography mass spectrometry and near infrared spectroscopy. Density functional theory (DFT) results indicated that ethanol presented higher interaction energy followed by acetone, diethyl ether and hexane, which was consistent with experimental findings. Hydrogen bond and non-covalent interaction results from DFT demonstrated that the predominant interaction was found for high polarity of ethanol over other solvents and γ-OH in the lignin model is the key site.

Biomass Fractionation and Lignin Fractionation towards Lignin Valorization

Lignin, as the most abundant aromatic biopolymer in nature, has attracted great attention due to the complexity and richness of its functional groups for value-added applications. The yield of production of lignin and the reactivity of prepared lignin are very important to guarantee the study and development of lignin-based chemicals and materials. Various fractionation techniques have been developed to obtain high yield and relatively high-purity lignin as well as carbohydrates (hemicelluloses and celluloses) and to reduce the condensed and degraded nature of conventional biorefinery lignin. Herein, novel and efficient biomass fractionation and lignin fractionation towards lignin valorization are summarized and discussed.