Using Sulfobutylated and Sulfomethylated Lignin as Dispersant for Kaolin Suspension

Ionic Lignin Polymers for Controlled CO2 Capture, Release, and Conversion into High-Value Chemicals

In this study, an innovative and cost-effective ionic polymer for CO2 capture and utilization for the first time, using abundant and nonfood-based biomass lignin is reported. The modified ionic polymer synthesizes through the reaction of glycidyltrimethylammonium chloride with lignin under alkaline conditions to yield quaternary ammonium ionic functionality. Subsequently, the hydroxide-based pure ionic lignin polymer is employed for CO2 capture from both direct air and concentrated CO2 sources at room temperature and atmospheric pressure. Structural characterization of the polymers is accomplished through 1H, 13C, and 2D-heteronuclear single quantum coherence (HSQC) NMR, and FT-IR spectroscopy. The CO2 capture process is established through the formation of bicarbonate ions alongside the presence of CO2. The captured CO2 is precisely quantified by using inverse-gated proton decoupled 13C NMR with an internal standard (trioxane). Remarkably, the captured-CO2 amounts of ionic lignin polymer are 1.06 mmol g-1 (47 mg g-1) from concentrated-CO2 source and 0.60 mmol g-1 (26 mg g-1) from direct-air. The captured-CO2 in ionic lignin polymer is released in controlled manner and utilized in the synthesis of cyclic carbonate, showcasing the productive application of the captured carbon. Moreover, the fully controlled recovering of ionic lignin polymer achieves via repeated CO2 release ↔ CO2 capture.

Exploring chemical reactions to enhance thermal and dispersion stability of kraft and organosolv lignin

Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T50% values, suggesting a better stability towards degradation.

Assessment of the effect of different pulping by-products on enhancing the reuse of rubber waste in producing of cement-mortar

This work deals with avoiding the pollution risks from paper pulping liquors and rubber wastes that result from routine disposal tools; moreover, finding an approach to minimize the drawback of incorporating the rubber waste in weakening the strength of building materials. In this respect, pulping black liquors (BLs) is assessed as a treating agent for rubber waste and substituting the water in cement mortar formulation. The assessment was achieved by testing the mechanical properties, water resistance (reduction in water absorption and dimensional change against water), and morphology. The results showed that all BLs from different pulping agents, used in mixtures with water, provided improvements in both strength and water resistance properties. Kraft black liquor is most effective in providing improvements in compressive strength and flexural strength, as well as resistance to water absorption and change in dimension after exposure to water for 24 h, where the improvements were 688.2 %, 494.3 %, 27 %, and 65.3 %, respectively. It is interesting to note that this investigated route provided improvements in the impact resistance property of mortar. This last property is essential for minimizing accidents on the highway.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Facile construction of lignin-based network composite hydrogel for efficient adsorption of methylene blue from wastewater

Adsorption method is an effective approach to treat wastewater containing methylene blue. Herein, a cost-effective and eco-friendly lignin-based network composite hydrogel adsorbent (PAA@SML) was constructed by using polyacrylic acid (PAA) to crosslink with sulfomethylated lignin (SML) via free radical polymerization for adsorption of methylene blue (MB) from wastewater. The constructed PAA@SML-0.2 exhibited remarkable adsorption performance towards removal of MB, with a maximum theoretical adsorption capacity of 777.1 mg·g-1. The improved efficiency can be attributed to the well-established network structure and abundant hydrophilic functional groups present in the adsorbent, promoting the interaction between methylene blue (MB) molecules and the adsorption sites of the adsorbent. The adsorption process of the adsorbent for MB followed the pseudo-second-order kinetic and the Langmuir isotherm models, which illustrated the adsorption process attributed to monolayer chemisorption. Mechanism investigation confirmed that the adsorption of MB by PAA@SML-0.2 primarily relied on hydrogen bonding and electrostatic interactions. Moreover, the recyclability test demonstrated excellent regeneration usability and stability of PAA@SML-0.2, and the adsorption capacity maintained above 74.0 % after five cycles. This constructed lignin-based network composite hydrogel is considered to have great potential in the treatment of organic dye in wastewater.

Polymeric Materials Obtained by Extrusion and Injection Molding from Lignocellulosic Agroindustrial Biomass

This review presents the advances in polymeric materials achieved by extrusion and injection molding from lignocellulosic agroindustrial biomass. Biomass, which is derived from agricultural and industrial waste, is a renewable and abundant feedstock that contains mainly cellulose, hemicellulose, and lignin. To improve the properties and functions of polymeric materials, cellulose is subjected to a variety of modifications. The most common modifications are surface modification, grafting, chemical procedures, and molecule chemical grafting. Injection molding and extrusion technologies are crucial in shaping and manufacturing polymer composites, with precise control over the process and material selection. Furthermore, injection molding involves four phases: plasticization, injection, cooling, and ejection, with a focus on energy efficiency. Fundamental aspects of an injection molding machine, such as the motor, hopper, heating units, nozzle, and clamping unit, are discussed. Extrusion technology, commonly used as a preliminary step to injection molding, presents challenges regarding fiber reinforcement and stress accumulation, while lignin-based polymeric materials are challenging due to their hydrophobicity. The diverse applications of these biodegradable materials include automotive industries, construction, food packaging, and various consumer goods. Polymeric materials are positioned to offer even bigger contributions to sustainable and eco-friendly solutions in the future, as research and development continues.

One-pot synthesis of magnetic cellulose nanocrystal and its post-functionalization for doxycycline adsorption

The composite of magnetite (Fe₃O₄) and cellulose nanocrystal (CNC) is considered a potential adsorbent for water treatment and environmental remediation. In the current study, a one-pot hydrothermal procedure was utilized for magnetic cellulose nanocrystal (MCNC) development from microcrystalline cellulose (MCC) in the presence of ferric chloride, ferrous chloride, urea, and hydrochloric acid. The x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy analysis confirmed the presence of CNC and Fe₃O₄, while transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis verified their respective sizes (< 400 nm and ≤ 20 nm) in the generated composite. To have an efficient adsorption activity for doxycycline hyclate (DOX), the produced MCNC was post-treated using chloroacetic acid (CAA), chlorosulfonic acid (CSA), or iodobenzene (IB). The introduction of carboxylate, sulfonate, and phenyl groups in the post-treatment was confirmed by FTIR and XPS analysis. Such post treatments decreased the crystallinity index and thermal stability of the samples but improved their DOX adsorption capacity. The adsorption analysis at different pHs revealed the increase in the adsorption capacity by reducing the basicity of the medium due to decreasing electrostatic repulsions and inducing strong attractions.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Lignin-based composites for high-performance supercapacitor electrode materials

With the rapid development of the global economy, the depletion of fossil fuels and the intensification of environmental pollution, there is an increasingly urgent need for new and green electrochemical energy storage technologies in society. In this thesis, ligninsulfonate/polyaniline nanocomposites were synthesized by in situ chemical oxidation using aniline as the monomer, lignin as the template and dopant, and ammonium persulfate as the oxidant. The results showed that the average diameter of the ligninsulfonate/polyaniline nanocomposite was 85 nm, and the composite electrode exhibited good electron conduction ability and excellent capacitive performance by ligninsulfonate doping. The electrode material showed the best electrochemical performance when the ligninsulfonate addition was 0.1 g. The specific capacitance can reach 553.7 F g-1 under the current density of charge/discharge 1 A g-1, which is higher than that of the pure PANI electrode. The composite electrode material has good multiplicative performance and cycling stability, and the capacitance retention rate can be maintained at 68.01% after 5000 cycles at a charge/discharge current density of 10 A g-1 (three-electrode system), and the capacitance retention rate can be maintained at 54.84% after 5000 cycles at a charge/discharge current density of 5 A g-1 (two-electrode system).

Xylo-oligosaccharides and lignin production from Camellia oleifera shell by malic acid hydrolysis at mild conditions

Camellia oleifera shell (COS), a by-product of processing woody vegetable oil, is rich in hemicellulose and lignin. In this study, we investigated the effects of acid concentration, pretreatment temperature and reaction time on the concentration and yield of xylo-oligosaccharides (XOS) and the degree of polymerization (DP) distribution of XOS when pretreating COS with malic acid (MA). Under moderate condition (2 M MA, 120 ℃, 30 min), the maximum yield of XOS with DP 2-4 was 48.78% (based on the initial xylan) with low xylose, 5-hydroxymethylfurfural (HMF) and furfural, in which xylobiose (X₂), xylotriose (X₃) and xylotraose (X₄) concentrations were 5.22 g/L, 2.75 g/L and 2.91 g/L, respectively. In addition, acid-insoluble lignin (AIL) in the residue after MA pretreatment and milling wood lignin (MWL) were mainly composed of guaiacyl and syringyl. AIL has higher thermal stability than MWL, which can be the stabilizer for producing flame-resistant materials.

Cationic Lignin Polymers as Flocculant for Municipal Wastewater

The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3–3.3 meq/g), increased water solubility (89–96% in neutral pH), and increased molecular weight (70,000–210,000 g/mol) of lignin. The lignin–METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin–METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin–METAC led to the chemical oxygen demand (COD) reduction of 17–23% and total organic carbon (TOC) drop of 51–60%. The lignin–METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin–METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin–METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin–METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin–METAC in a dual coagulation–flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin–METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin–METAC flocculant slightly increased the ammonia–nitrogen content in both singular flocculation and dual coagulation–flocculation systems due to the residual ammonia content of lignin–METAC. The coagulation–flocculation system determined that the use of lignin–METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater.