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• The properties of technical lignin produced commercially were compared. • The challenges, opportunities, and future directions of lignin valorization were discussed. • Currently, products derived from technical lignin include adhesives, resins, and plasticizers. • The purity, molecular weight, and solubility affect the valorization strategies of technical lignin. Currently, the majority of chemicals are derived from petroleum-based feedstocks. In recent years, the valorization of lignin as feedstock for the production of alternative chemicals has attracted tremendous attention. Despite the renewed interest in the development of valorized lignin, few lignin-based chemicals have been produced at industrial scales and still, most of the lignin is used as an energy source. This review paper intends to discuss the technical obstacles and challenges in converting lignin moieties into value-added products effectively. Alternative modification routes have been discussed to produce lignin-based materials, while these routes strongly rely on the chemical structure of lignin. The propose of this review is to provide insight into the crucial role of the commercial lignin extraction processes on the properties of generated technical lignin and ultimately on its potential in reacting with other chemicals for inducing valorized lignin-derived materials for altered applications. Existing strategies for the functionalization of technical lignin are also summarized. The challenges, opportunities, and future direction regarding the biorefining of technical lignin are reviewed. [ABSTRACT FROM AUTHOR]

Fabricating bio-based materials with various functionalities is crucial in sustainable material production. In the current study, we produced microgels that comprised carboxyalkylated lignin with altered alkyl spacers and studied how these alkyl spacers on the carboxylated lignin impacted the physicochemical properties of lignin-based microgels. The 1H NMR results indicated that the microgels containing lignin derivatives had similar crosslinking degrees (10.7% for CPr-C vs. 11.1% for CPe-C). Also, the rheological studies suggested that the storage modulus was greater for CPe-C microgel than CPr-C microgel, which might be due to its greater density and compactness. For both samples, the loss modulus was less significant than the storage modulus indicating that the microgels had more remarkable elasticity than viscosity, confirming their solid-like gel structures. With higher hydrophilicity and swelling, CPr-C adsorbed more heavy metals than CPe-C. The adsorption sequence of heavy metals for both lignin-based microgels was Ni+2>Zn+2>Cd+2, which could be associated with the smaller radius of Ni+2 than Zn+2 and Cd+2 ions. [Display omitted] • Microgels were produced via polymerization of carboxyalkylated lignin derivatives. • The physicochemical properties of microgels were analyzed comprehensively. • The rheological properties and adsorption of heavy metals on microgels were studied. • Microgel containing carboxypropylated lignin performed better than that containing carboxypenthylated lignin. [ABSTRACT FROM AUTHOR]

• Correlations were created between physical and chemical properties of hydrolyzed lignin. • The response of hydrolyzed lignin (HL) to sulfoalkylation was studied. • The dispersion performance and properties of the HL derivatives were related. • The more effective sulfoalkylation and the desired properties of HL were identified. This study focuses on the physicochemical characterization of lignin produced via enzymatic hydrolysis of hardwood chips. Enzymatically produced lignin (HL) was water-insoluble particles that contained carbohydrates that were chemically bound to lignin. The X-ray photoelectron spectroscopy (XPS), 1H-NMR, 13C-NMR, 31P NMR and two-dimensional 1H-13C HSQC, 1H-13C HSQC-TOCSY, 1H-13C HMBC NMR analyses confirmed that the HL samples with the lower internal ether linkages had fewer β-O-4 aryl ether and lignin-carbohydrate (LCC) bonds but more phenolic hydroxyl and carboxylate groups. Moreover, the samples with the lower sugar content were smaller and more porous. The chemical reactivity analysis of HL samples in various sulfo-functionalization reactions (sulfonation S, sulfomethylation SM, and sulfoethylation SE) revealed a direct correlation between the degree of substitution (DS) and phenolic guaiacyl (G) and the condensed hydroxyl group of HL. Also, the carbohydrate content and particle size of HL were inversely related to the degree of substitution of sulfo-functionalization of HL. The SM- and S- modified HL samples with adequate water solubility (9−10 g/L), charge density (≥1.9 mmol/g), and small particle size (5 μm) were shown to be effective stabilizers for clay suspensions via reducing the instability index (TSI∼10) and settling velocity (−4 %/h) of clay particles in the suspension. The results obtained in this study shed light on the significant role of residual carbohydrates and internal ether linkages of HL on the physicochemical properties and sulfo-functionalization of HL. [ABSTRACT FROM AUTHOR]

Lignin composites with anticorrosion behavior were prepared from lignin and acrylic acid, acrylamide via copolymerization. [Display omitted] • New carbohydrate polymer synthesized and characterized as corrosion inhibitor for mild steel. • Lignin copolymer was prepared from Kraft lignin, acrylate monomers (AA, AM) via facile copolymerization. • Lignin composites exhibited excellent anticorrosion at low concentration. In this work, the corrosion inhibition effectiveness of semi natural lignin polymers, lignin-acrylamide and lignin-acrylic acid, in HCl solution was investigated by means of weight loss, polarization, electrochemical impedance, atomic force microscope (AFM) and scanning electron microscope (SEM) analyses. The results showed that the inhibition effectiveness of lignin-acyclic acid (AA) was better than that of lignin–acrylamide (AM), because the corrosion inhibition efficiency and adsorption capacity of lignin-AA on carbon steel surface were more significant than those of lignin-AM. AFM and SEM analyses showed that the surface of carbon steel was insignificantly affected in HCl solution containing lignin-AA. The mechanism of inhibition effectiveness of lignin-AA and lignin-AM in HCl solution was also verified by molecular dynamics (MD) simulations. [ABSTRACT FROM AUTHOR]

As we all know, although petroleum-based plastic products greatly facilitated our life, they also caused great negative impacts on the environment and human health. In recent decades, cellulose nanofibers (CNFs) exhibit good degradability, renewability, and excellent mechanical properties, which is expected as a potential substitute for traditional petroleum-based plastic. Herein, we reported a facile preparation strategy of CNF dry powder based on TEMPO-oxidation process as well as the construction method of CNF-lignin bulk material which exhibited higher mechanical strength than most plastics. Among them, CNF-lignin bulk material containing 5% lignin performed excellent flexural strength (~198 MPa), which is much higher than that of most commercial plastics. Other important properties of this material such as super lightweight (~1.35 g/cm3), good toughness (~8.5 kJ/cm2), and high thermal stability (~295 °C) are also capable of meeting the requirements of replacing plastics. The mechanism investigation of lignin adding for improving the mechanical properties of CNF-lignin composite testified that the lignin in CNF-lignin composite filled the voids among CNFs and no chemical reactions happened between lignin and CNFs. Overall, this work offers a strategy to fabricate an environmentally friendly CNF-lignin bulk material, which is a promising alternative to petroleum-based plastics. [Display omitted] • Dispersible CNF dry powder can be prepared from CNF suspension by solvent replacement and rotary evaporation. • CNF-lignin bulk material is prepared by mixing and drying CNF dry powder, lignin and water. • Lignin can improve the properties of CNF bulk materials which expected to be a substitute for petroleum-based plastics. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) has a wide application in the chemical, electronic and textile industries due to its high ductility, toughness, and good thermal stability. However, the generation of strong and multifunctional PU film is challenging. Herein, lignin nanoparticle (LNP), which was produced from black liquor (i.e. , a waste stream from the wheat straw pulping process) using biomass based γ- valerolactone via nanoprecipitation, was used as a nano-filler for enhancing the strength of the PU film. The well distributed LNP had nano-sized particles and abundant phenolic hydroxyl groups, which could act as lubricating agents when incorporated into the PU matrix, thus leading to energy dissipation. By developing additional hydrogen bonds, LNP enhanced the tensile strength and elongation of the PU film. The maximum tensile strength and elongation at break of 50.7 MPa and 755.8% were achieved, while pure PU film had 18.4 MPa and 223.2% tensile strength and elongation, respectively. In addition, the natural inherent properties of lignin endowed the PU film with multifunctional properties, such as hydrophobicity, anti-ultraviolet, and better hydrothermal stability. Based on these interesting results, the LNP incorporation into the PU film could further broaden the practical utilization of the PU film. [Display omitted] • Biomass based solvent was used to produce well distributed lignin nanoparticle. • High strength film was fabricated through a facile blending and casting process. • Natural inherent properties of lignin endowed film with multifunctional properties. [ABSTRACT FROM AUTHOR]