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Highlights • Hydrolysis lignin was oxidized via periodate treatment. • The mechanism of oxidation reaction was comprehensively examined. • The oxidization altered the molecular weight and carboxylate group of lignin. • Performance of oxidized lignin as a coagulant for a suspension system was evaluated. Abstract Lignin is an under-utilized biopolymer, but it can be modified to broaden its application in industry. In this work, a lignin-based coagulant was prepared by periodate oxidation of hydrolysis lignin that contained carbohydrates. The results showed that water-soluble oxidized hydrolysis lignin (OHL) with an anionic charge density of 0.9 mmol/g, carboxyl group content of 1.7 mmol/g and molecular weight of 6200 g/mol was obtained under the reaction conditions of 1/1 M ratio of sodium periodate/lignin, pH 5, 50 °C and 2 h. The mechanism of periodate oxidation of hydrolysis lignin involved the formation of quinoid intermediate, the increase in carboxylate group in final oxidized lignin, and the release of sugars from the decomposition of lignin-carbohydrate linkage. The adsorption analysis revealed that OHL adsorbed on the surface of aluminum oxide particles via charge neutralization and hydrogen bonding following Langmuir adsorption model. When 12 mg/g OHL was added to the aluminum oxide suspension, the mean chord length of particles increased from 17 μm to 39 μm, while their total counts decreased by 40%. Vertical scanning analysis was also used to evaluate the coagulation/settling performance of OHL in aluminum oxide suspensions. The settling rate of particles accelerated from 22 mL/h to 600 mL/h in the presence of OHL, increasing the transparency of suspension from 15% to 78% and the compactness of sediment from 20 g/L to 84 g/L. [ABSTRACT FROM AUTHOR]

• 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]

• Kraft lignin and methyl methacrylate were polymerized, and the reaction was optimized. • The characteristics of polymer were studied by NMR, SEM, GPC, tensiometer and TGA. • The performance of polymer in UV absorption and humic acid adsorption was assessed. • Results confirmed the production of hydrophobic multifunctional lignin based material. In this work, the modification of lignin (KL) with methyl methacrylate (MMA) is presented via free-radical polymerization in the presence of potassium persulfate as an initiator. One-step purification of the reaction products was also attested for generating KL-MMA with 95 wt% yield and 85 wt% MMA conversion. The characteristics of KL-MMA were studied comprehensively employing 1H NMR, 31P-NMR, 13C-NMR, SEM, FTIR, and GPC. KL-MMA demonstrated significantly higher thermal stability and UV absorption compared with unmodified KL and PMMA homopolymer. The hydrophobicity of lignin derivatives was substantially improved via reacting with acrylate monomer (a contact angle change from 25° for KL to 88° for KL-MMA). The performance of KL-MMA as an adsorbent for humic acid (HA) was also evaluated in detail by means of a Quartz crystal microbalance with dissipation (QCM-D). The results confirmed the superior adsorption performance of KL-MMA to that of KL and PMMA for HA. The modified lignin polymer possessed a multitude of excellent features including remarkable hydrophobic properties and adsorption capacity. The product offers a wide range of applications possibly in food packaging and water purification systems. [ABSTRACT FROM AUTHOR]

Highlights • Kraft lignin was reacted with 3-chloro-2-hydroxypropansulfonic acid sodium. • The sulfonation reaction occurred both on phenolic and aliphatic groups. • Modified lignin had the charge density of −3.3 meq/g and Mw of 45,500 g/mol. • The performance of modified lignin was compared with lignosulfonate in dye removal. Abstract In this paper, kraft lignin was reacted with 3-chloro-2-hydroxypropansulfonic acid sodium (CHPS) to produce hydroxypropyl sulfonated lignin (SL). The effects of reaction conditions, e.g., the molar ratio of CHPS to lignin, the concentration of NaOH and the reaction temperature and time, on the charge density of resultant SL were investigated. The optimized conditions were found to be 80 °C, 4 h reaction time, 0.05 M NaOH concentration and 5/1 mol/mol of CHPS/lignin, which generated SL with the charge density and molecular weight of −3.33 meq/g and 45,536 g/mol, respectively. The solubility of KL was 9.6 g/L while that of SL was 100 g/L at the neutral pH. The reaction mechanism between kraft lignin and CHPS was fundamentally discussed. The SL was also characterized by elemental analysis and proton nuclear magnetic resonance (1H NMR). The thermal stability and surface activity of the SL were also evaluated and compared with those of commercially produced lignosulfonate (LSS). The efficiency of SL as a coagulant for dye (basic blue 41 and ethyl violet) removal from simulated wastewater was compared with that of LSS. The zeta potential and particle size analyses were conducted to determine the interaction mechanism of dye and lignin derivatives, and the kinetic studies confirmed their fast complexation. [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]

Condensed lignin formed during eucalyptus woodchip pre-hydrolysis adversely affects subsequent enzymatic saccharification, and phenolic additives are popular lignin condensation inhibitors. The goal of this project was to reveal the mechanisms of lignin modification by phenolic additives during woodchip pre-hydrolysis and its effects on subsequent enzymatic saccharification. The HSQC and 31P NMR analyses confirmed that resorcinol with three electrophilic substitution of active sites could act as a cross-linking agent to promote the formation of condensed lignin, whereas 2-naphthol and sodium 2-naphthol-7-sulfonate could block benzyl carbocations and reduce the formation of condensed lignin. Interestingly, the introduction of sulfonic acid groups increased the electrostatic repulsion between enzyme and lignin as well as increased the hydrophilicity of lignin, thereby greatly reducing non-productive adsorption and physical obstacle effects. Sodium 2-naphthol-7-sulfonate as an efficient benzyl carbocations scavenger reduced the non-productive adsorption and physical obstacle effects of lignin by 82.4% and 13.3%, respectively. [Display omitted] • Sodium 2-naphthol-7sulfonate is an efficient benzyl carbocation scavenger. • Carbocation scavengers can only have one active reactive site. • Breaking α-aryl ether bonds in acidic conditions forms carbocations. • Lignin-enzyme interactions include non-adsorption and physical obstacle effects. [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]

• Hydrolysis lignin was polymerized with acrylic acid to valorize it. • Soluble hydrolysis lignin-acrylic acid was an efficient coagulant for cationic dye. • Insoluble hydrolysis lignin-acrylic acid was an effective adsorbent for the dye. • Performance of products was analyzed at different temperatures and ionic strength. • Results show routes to utilize hydrolysis lignin for removing dyes from effluents. Hydrolysis lignin is a major product of the enzymatic fractionation of lignocellulosic biomass and its functionalization plays a crucial role in valorizing this material. In this work, functional hydrolysis lignin-derived polymer (hydrolysis lignin-acrylic acid polymer, AA-HL) was generated to act as an adsorbent and coagulant for eliminating ethyl violet (EV) dye from solutions. AA-HL was partially soluble in water. The soluble fraction of the lignin polymer in the coagulation studies led to the complete dye removal from the solutions at a 6 mg/g dosage following the charge neutralization mechanism. The performance of insoluble AA-HL as an adsorbent was also investigated using a Quartz crystal microbalance with dissipation (QCM-D), and the results indicated the great adsorption of the dye to the insoluble AA-HL. The high stability of AA-HL adsorbent was also confirmed in the dye adsorption process at 40 ᵒC. Furthermore, the dye adsorption on AA-HL was promoted by increasing the ionic strength of the solution to 500 mM NaCl, suggesting the existence of the strong hydrophobic interaction between the dye moiety and AA-HL. The results suggested that soluble and insoluble super functional lignin derivatives can be produced from hydrolysis lignin with a strong affinity toward dyes. [ABSTRACT FROM AUTHOR]

In this study, a novel cationic tall oil lignin (TOL)-starch copolymer was successfully prepared by the polymerization reaction of TOL, starch and a cationic monomer of (3-acrylamidopropyl) trimethyl ammonium chloride (APTAC) through the free radical chain extension. 1H NMR and 1H–1H COSY studies demonstrated that the TOL and starch were covalently linked by the APTAC to produce the cationic copolymers. The copolymerization reaction reduced the phenolic content of TOL, yielding an increment in the solubility, molecular weight (M w), and charge density of the cationic copolymer. Moreover, the thermochemical analysis indicated that the obtained copolymer, CR5-pH11, with the largest M w possessed the highest glass transition temperature (T g) of 184 °C due to the insertion of a long APTAC chain and the presence of starch and TOL. Owing to its highest charge density (3.6 meq/g) and largest M w (56,100 kg/mol), CR5-pH11 exhibited the most efficient flocculation behavior in the kaolin suspension under altered agitation and gravitational forces as confirmed by focused beam reflectance measurement and sedimentation techniques. This study provided a new strategy to developing sustainable cationic lignin-starch flocculant for clay suspension systems. • Cationic lignin starch polymer was produced via free radical polymerization. • The NMR analysis confirmed the chemical structure of the produced polymer. • Higher molecular weight and charge density product (CR5-pH11) was more thermally stable. • CR5-pH11 product had better flocculation under varied agitation and gravitational forces. [ABSTRACT FROM AUTHOR]

This paper proposed a novel xylanase-assisted activated carbon process to produce a high-purity sugar stream from pre-hydrolysis liquid (PHL) of the kraft-based dissolving pulp production process. The results showed that the enzymatic hydrolysis could effectively improve the lignin removal and sugar purity at pH 5 and 50 °C. It was observed that the cleavage of lignin-carbohydrate complex (LCC) by enzyme led to more sugar and soluble lignin production in PHL. The main mechanisms involved are the reduced pore clog due to the lignin converted from colloidal to dissolved state at higher pH, lower sugar loss obtained by the reduction of polymerization degree of poly-sugars in PHL and also the removal of the lignin disconnected from the LCC. FTIR NMR, particle size, BET, and SEM analyses confirmed that the induced soluble lignin could be adsorbed by activated carbon effectively without blocking its pores, which improved the selectivity and productivity of activated carbon for removing lignin and generating higher purity sugar stream (97.5 wt. %). Based on the promising results and simplicity of the proposed operations, the introduced process may be attractive to the industry for generating high-purity sugars at an industrial scale. [Display omitted] • A novel process of producing high purity sugar solution from PHL was proposed. • Conversion of colloidal lignin to dissolved lignin reduced pore clog at higher pH. • Enzymolysis treatment improved the adsorption selectivity of activated carbon. • The cleavage of LCC bond helped reduce the lignin particle size and its removal. [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]

Rice straw (RS) is an abundant agricultural residue with plentiful hydroxyl groups. In this study, a low-cost and effective RS-based phosphate adsorbent (RS-PA) was prepared through a three-step reaction process, successively with epichlorohydrin (ECH), ethylenediamine (EDA), and triethylamine (TEA). The elimination process of phosphate was optimized by considering altered adsorption conditions. The successful production of RS-PA was confirmed by FTIR, organic element, and zeta potential analyses. The key factors influencing the phosphate adsorption were the temperature in the second reaction step and EDA dosage. Langmuir isotherm and pseudo-second-order kinetic models predicted the phosphate adsorption on the RS-PA very well. A complete phosphate removal was achieved at 50 mg/L phosphate concentration, 10 g/L adsorbent dosage and 25 ℃ in 10 min. The exothermic nature of phosphate adsorption on RS-PA was confirmed since the temperature rise reduced the adsorption of phosphate on the adsorbent. These results demonstrate that full component rice straw-based phosphate adsorbent was successfully prepared for the removal of phosphorus compounds from waste water. [Display omitted] • Amine functionalized low-cost rice straw-based phosphate adsorbent was developed. • The impact of process conditions on generating adsorbent was studied. • The kinetic adsorption models of phosphate on the generated adsorbent were studied. • The isotherm adsorption models of phosphate on the generated adsorbent were studied. [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]

Schematic of lignin content on the compatibility of LCNF and PLA. [Display omitted] • PLA/LCNF composites with both high strength and great ductility were prepared. • Lignin particles improved the interfacial interaction and compatibility between LCNF and PLA. • UV-shielding, water vapor barrier performance, and good thermal stability were integrated in the PLA composites film. • A fully biodegraded composites using the green LCNF and biodegradable PLA were produced. Currently, it is challenging to produce biodegradable polylactic acid (PLA) composite with both high strength and great ductility. In this work, lignin-containing cellulose nanofibrils (LCNF) derived from old newspaper were amalgamated with a biodegradable PLA matrix to prepare multifunctional composites with integrated strength and ductility. Owing to the lignin content of LCNF, the interfacial interaction and compatibility between LCNF and PLA matrix were improved by hydrogen bonding and van der Waals interactions, thereby the mechanical properties of PLA/LCNF composite films were successfully enhanced. After blending LCNF with PLA, the prepared PLA/LCNF composite films exhibited excellent UV-shielding, water vapor barrier performance, and good thermal stability. This study reveals a feasible strategy to design full biodegradable multifunctional composite using the green LCNF and biodegradable PLA. [ABSTRACT FROM AUTHOR]