Lignin Precursors Research Articles

Engineering of the Crystalline Lattice of Hard Carbon Anodes Toward Practical Potassium‐Ion Batteries

AbstractHard carbons have attracted increased interest as an alternative of graphite for the anodes of potassium‐ion batteries (PIBs). However, the practical applications of hard carbon anodes are hampered by their low capacities, high potential platforms, and large potential hysteresis. Hard carbons coupled with graphitic nanodomains can achieve stable potassium‐ion storage behaviors with low potential platforms and low potential hysteresis. Herein, the crystalline lattice in hard carbon anodes is tuned by incorporating graphene oxide in renewable lignin precursors. The modified hard carbon (i.e., QLGC) anodes show graphitized nanodomains in the carbon matrix with an expanded interlayer spacing (0.42 nm) in the amorphous regions, which results in a stable potassium‐ion (de)intercalation behavior. Thus, the QLGC anodes exhibit a high capacity of 164 mAh g−1 with low potential hysteresis in the low potential platform region. Moreover, the QLGC anode delivered a highly stabilized capacity of 283 mAh g−1 at 50 mA g−1, a high‐rate capability, and stable cycling performance. Furthermore, the charge storage mechanisms of QLGC anode are elucidated by electro‐kinetic analysis and ex/in situ physicochemical characterizations. This study opens a new avenue for designing hard carbon anodes with engineered crystalline lattices toward practical PIBs.

Ferulic acid is a putative surrender signal to stimulate programmed cell death in grapevines after infection with Neofusicoccum parvum.

An apoplectic breakdown from grapevinetrunk diseases (GTDs) has become a serious challenge to viticulture as a consequence of drought stress. We hypothesize that fungal aggressiveness is controlled by a chemical communication between the host and colonizing fungus. We introduce the new concept of a 'plant surrender signal'accumulating in host plants under stress and facilitating the aggressive behaviour of the strain Neofusicoccum parvum (Bt-67) causing Botryosphaeriaceae-related dieback in grapevines. Using a cell-based experimental system (Vitis cells) and bioactivity-guided fractionation, we identify trans-ferulic acid, a monolignol precursor, as a 'surrender signal'. We show that this signal specifically activates the secretion of the fungal phytotoxin fusicoccin A aglycone. We show further that this phytotoxin, mediated by 14-3-3 proteins, activates programmed cell death in Vitis cells. We arrive at a model showing a chemical communication facilitating fusicoccin A secretion that drives necrotrophic behaviour during Botryosphaeriaceae-Vitis interaction through trans-ferulic acid. We thus hypothesize that channelling the phenylpropanoid pathway from this lignin precursor to the trans-resveratrol phytoalexin could be a target for future therapy.

Exploration of the chemical linkages between lignin and cellulose in poplar wood with 13C and Deuterium dual isotope tracer

Stable isotopes were used to label lignin and cellulose to accurately explain the chemical association between them in poplar wood. Both the 13C-labeled lignin precursors (coniferin-[Cα-13C] or coniferin-[Cγ-13C]) and the Deuterium-labeled cellulose precursor (UDP-glucose-[6,6-D2]) were added to a growing poplar plant. After 20 d cultivation, hemicellulose and lignin-carbohydrate complexes (LCC) were extracted from the newly-formed xylem by Björkman method, then the abundance of 13C and D were detected. It revealed that both lignin precursors and cellulose precursor could be efficiently deposited in the newly-formed xylem, while cellulose precursor was detected mainly deposited on cellulose. Then the LCC was degraded using cellulase and hemicellulase to obtain enzymatically degraded lignin-carbohydrate complexes (EDLCC). The 13C NMR，1H NMR and 2D NMR analyses of EDLCC clearly showed that lignin subunits in poplar wood were mainly connected through β-O-4, β-5, β-β structures, while cellulose was mainly connected to lignin by ether bonds, acetal bonds and ester bonds. The ether bonds and acetal bonds were between cellulose C6 and lignin Cα, while the ester bonds were between cellulose C6 and lignin Cγ. The study provides new evidence for the structural information between cellulose and lignin in poplar.

Smart lignin-based polyurethane conjugated with corrosion inhibitor as bio-based anticorrosive sublayer coating

Incorporating corrosion inhibitors in the formulation of coatings can yield active coatings which are able to provide a sustained release of the corrosion inhibitor in the case of emergence of microcrack in the structure of the coating. Herein, we developed bio-based polyurethane sublayer coatings with strong anticorrosion performances. First, lignin-corrosion inhibitor (LCI) conjugate was obtained through conjugation of nicotinic acid to lignin through hydrolytically cleavable ester linkage to afford the steady release of low concentrations of corrosion inhibitor in case of the emergence of microcracks. Subsequently, solution polyaddition of LCI with diisocyanates and polypropylene glycol and coating on the stainless steel surface afford the polyurethane coatings. Coating with a thickness of 16 µm increased the E corr from − 481 mV (for bare steel) to + 187 mV and reduced both I corr and corrosion rate more than 6700 times. As an added benefit, after creating artificial cracks on the surface of the coating, the release of corrosion inhibitors gradually increased the impedance value, indicating a thin barrier layer has formed within the cracks. • -Lignin-corrosion inhibitor conjugate was prepared as anticorrosive polyol precursor. • -Anticorrosive polyurethane coatings were fabricated based on lignin precursor. • -Thickness of 16 µm of this coating reduce the corrosion rate over 6700 times. • -The corrosion inhibitor released by the coating inhibits corrosion in microcracks.

Sustainable lignin precursors for tailored porous carbon-based supercapacitor electrodes

Sustainable materials are attracting a lot of attention since they will be critical in the creation of the next generation of products and devices. In this study, hydrogels were effectively synthesized utilizing lignin, a non-valorised biopolymer from the paper industry. This study proposes a method based on utilizing lignin to create highly swollen hydrogels using poly(ethylene) glycol diglycidyl ether (PEGDGE) as a crosslinking agent. The influence of different crosslinker ratios on the structural and chemical properties of the resultant hydrogels was investigated. Pore size was observed to be lowered when the amount of crosslinker was increased. The inclusion of additional hydrophilic groups in the hydrogel network decreased the swelling capacity of the hydrogels as the crosslinking density increases. These precursor materials were carbonised and electrochemically tested for application as electrodes for supercapacitors with capacitance characterized as a function of crosslinker ratio.

Populus alba cationic cell-wall-bound peroxidase (CWPO-C) regulates the plant growth and affects auxin concentration in Arabidopsis thaliana

The poplar cationic cell-wall-bound peroxidase (CWPO-C) mediates the oxidative polymerization of lignin precursors, especially sinapyl alcohols, and high molecular weight compounds that cannot be oxidized by other plant peroxidases, including horseradish peroxidase C. Therefore, CWPO-C is believed to be a lignification-specific peroxidase, but direct evidence of its function is lacking. Thus, the CWPO-C expression pattern in Arabidopsis thaliana (Arabidopsis) was determined using the β-glucuronidase gene as a reporter. Our data indicated that CWPO-C was expressed in young organs, including the meristem, leaf, root, flower, and young xylem in the upper part of the stem. Compared with the wild-type control, transgenic Arabidopsis plants overexpressing CWPO-C had shorter stems. Approximately 60% of the plants in the transgenic line with the highest CWPO-C content had curled stems. These results indicate that CWPO-C plays a role in cell elongation. When plants were placed horizontally, induced CWPO-C expression was detected in the curved part of the stem during the gravitropic response. The stem curvature associated with gravitropism is controlled by auxin localization. The time needed for Arabidopsis plants overexpressing CWPO-C placed horizontally to bend by 90° was almost double the time required for the similarly treated wild-type controls. Moreover, the auxin content was significantly lower in the CWPO-C-overexpressing plants than in the wild-type plants. These results strongly suggest that CWPO-C has pleiotropic effects on plant growth and indole-3-acetic acid (IAA) accumulation. These effects may be mediated by altered IAA concentration due to oxidation.

Sodium silicate promotes wound healing by inducing the deposition of suberin polyphenolic and lignin in potato tubers.

Wound healing is a postharvest characteristic of potato tubers through accumulating suberin and lignin, which could reduce decay and water loss during storage. This study aimed to explore the impact and mechanisms of sodium silicate on wound healing of potatoes. After being wounded, “Atlantic” potato tubers were treated with water or 50 mM sodium silicate. The results showed that sodium silicate treatment accelerated the formation of wound healing structures and significantly reduced the weight loss and disease index of tubers. Furthermore, sodium silicate induced the genes expression and enzyme activity of phenylalanine ammonia lyase (PAL), 4-coumarate: coenzyme A ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD) involved in the phenylpropane metabolism, enhancing the synthesis of the main precursors of suberin polyphenolic (SPP) and lignin, such as coniferyl alcohol, sinapyl alcohol, and cinnamyl alcohol. Meanwhile, the gene expression of StPOD and StNOX was activated, and the production of O2− and H2O2 was promoted, which could be used for injury signal transmission and oxidative crosslinking of SPP monomers and lignin precursors. Besides, antimicrobial compounds, total phenolics, and flavonoids were also induced. We suggest that sodium silicate could promote wound healing by inducing the deposition of SPP, lignin, and antimicrobial compounds in potato tubers.

Acclimation and Compensating Metabolite Responses to UV-B Radiation in Natural and Transgenic Populus spp. Defective in Lignin Biosynthesis.

Plants have evolved to protect leaf mesophyll tissue from damage caused by UV-B radiation by producing an array of UV-absorbing secondary metabolites. Flavonoids (phenolic glycosides) and sinapate esters (hydroxycinnamates) have been implicated as UV-B protective compounds because of the accumulation in the leaf epidermis and the strong absorption in the wavelengths corresponding to UV. Environmental adaptations by plants also generate a suite of responses for protection against damage caused by UV-B radiation, with plants from high elevations or low latitudes generally displaying greater adaptation or tolerance to UV-B radiation. In an effort to explore the relationships between plant lignin levels and composition, the origin of growth elevation, and the hierarchical synthesis of UV-screening compounds, a collection of natural variants as well as transgenic Populus spp. were examined for sensitivity or acclimation to UV-B radiation under greenhouse and laboratory conditions. Noninvasive, ecophysiological measurements using epidermal transmittance and chlorophyll fluorescence as well as metabolite measurements using UPLC-MS generally revealed that the synthesis of anthocyanins, flavonoids, and lignin precursors are increased in Populus upon moderate to high UV-B treatment. However, poplar plants with genetic modifications that affect lignin biosynthesis, or natural variants with altered lignin levels and compositions, displayed complex changes in phenylpropanoid metabolites. A balance between elevated metabolic precursors to protective phenylpropanoids and increased biosynthesis of these anthocyanins, flavonoids, and lignin is proposed to play a role in the acclimation of Populus to UV-B radiation and may provide a useful tool in engineering plants as improved bioenergy feedstocks.

Comparative Transcriptome and Metabolome Analysis of Resistant and Susceptible Piper Species Upon Infection by the Oomycete Phytophthora Capsici.

Phytophthora capsici is a destructive oomycete pathogen that causes devastating disease in black pepper, resulting in a significant decline in yield and economic losses. Piper nigrum (black pepper) is documented as susceptible to P. capsici, whereas its close relative Piper flaviflorum is known to be resistant. However, the molecular mechanism underlying the resistance of P. flaviflorum remains obscure. In this study, we conducted a comparative transcriptome and metabolome analysis between P. flaviflorum and P. nigrum upon P. capsici infection and found substantial differences in their gene expression profiles, with altered genes being significantly enriched in terms relating to plant-pathogen interaction, phytohormone signal transduction, and secondary metabolic pathways, including phenylpropanoid biosynthesis. Further metabolome analysis revealed the resistant P. flaviflorum to have a high background endogenous ABA reservoir and time-course-dependent accumulation of ABA and SA upon P. capsici inoculation, while the susceptible P. nigrum had a high background endogenous IAA reservoir and time-course-dependent accumulation of JA-Ile, the active form of JA. Investigation of the phenylpropanoid biosynthesis metabolome further indicated the resistant P. flaviflorum to have more accumulation of lignin precursors than the susceptible P. nigrum, resulting in a higher accumulation after inoculation. This study provides an overall characterization of biologically important pathways underlying the resistance of P. flaviflorum, which theoretically explains the advantage of using this species as rootstock for the management of oomycete pathogen in black pepper production.

Flexible and digestible wood caused by viral-induced alteration of cell wall composition

Woody plant material represents a vast renewable resource that has the potential to produce biofuels and other bio-based products with favorable net CO2 emissions.1,2 Its potential has been demonstrated in a recent study that generated novel structural materials from flexible moldable wood.3 Apple rubbery wood (ARW) disease is the result of a viral infection that causes woody stems to exhibit increased flexibility.4 Although ARW disease is associated with the presence of an RNA virus5 known as apple rubbery wood virus (ARWV), how the unique symptoms develop is unknown. We demonstrate that the symptoms of ARWV infections arise from reduced lignification within the secondary cell wall of xylem fibers and result in increased wood digestibility. In contrast, the mid-lamellae region and xylem ray cells are largely unaffected by the infection. Gene expression and proteomic data from symptomatic xylem clearly show the downregulation of phenylalanine ammonia lyase (PAL), the enzyme catalyzing the first committed step in the phenylpropanoid pathway leading to lignin biosynthesis. A large increase in soluble phenolics in symptomatic xylem, including the lignin precursor phenylalanine, is also consistent with PAL downregulation. ARWV infection results in the accumulation of many host-derived virus-activated small interfering RNAs (vasiRNAs). PAL-derived vasiRNAs are among the most abundant vasiRNAs in symptomatic xylem and are likely the cause of reduced PAL activity. Apparently, the mechanism used by the virus to alter lignin exhibits similarities to the RNAi strategy used to alter lignin in genetically modified trees to generate comparable improvements in wood properties.6-8.

Brassinosteroid Accelerates Wound Healing of Potato Tubers by Activation of Reactive Oxygen Metabolism and Phenylpropanoid Metabolism

Wound healing could effectively reduce the decay rate of potato tubers after harvest, but it took a long time to form typical and complete healing structures. Brassinosteroid (BR), as a sterol hormone, is important for enhancing plant resistance to abiotic and biotic stresses. However, it has not been reported that if BR affects wound healing of potato tubers. In the present study, we observed that BR played a positive role in the accumulation of lignin and suberin polyphenolic (SPP) at the wounds, and effectively reduced the weight loss and disease index of potato tubers (cv. Atlantic) during healing. At the end of healing, the weight loss and disease index of BR group was 30.8% and 23.1% lower than the control, respectively. Furthermore, BR activated the expression of StPAL, St4CL, StCAD genes and related enzyme activities in phenylpropanoid metabolism, and promoted the synthesis of lignin precursors and phenolic acids at the wound site, mainly by inducing the synthesis of caffeic acid, sinapic acid and cinnamyl alcohol. Meanwhile, the expression of StNOX was induced and the production of O2− and H2O2 was promoted, which mediated oxidative crosslinking of above phenolic acids and lignin precursors to form SPP and lignin. In addition, the expression level of StPOD was partially increased. In contrast, the inhibitor brassinazole inhibited phenylpropanoid metabolism and reactive oxygen metabolism, and demonstrated the function of BR hormone in healing in reverse. Taken together, the activation of reactive oxygen metabolism and phenylpropanoid metabolism by BR could accelerate the wound healing of potato tubers.

Performance and Economic Analysis of Organosolv Softwood and Herbaceous Lignins to Activated Carbons as Electrode Materials in Supercapacitors

In this work, yellow pine (YP, softwood) and switchgrass (SG, grass) lignins were extracted as a coproduct of an organosolv γ-valerolactone (GVL) biorefinery that also produces biofuels and furfural. The extracted lignins were converted to carbon precursors for synthesizing porous activated carbon electrodes for high energy-density supercapacitors. This research details the impact of lignin composition on the derived porous structures and electrochemical properties of activated carbons. Lignin precursors with various syringyl (S) to guaiacyl (G) contents were characterized using31P nuclear magnetic resonance (NMR) and two-dimensional1H‒13C NMR. A two-step activation process, using steam and carbon dioxide as the activating agents, enabled the formation of porous carbons structures with high surface area. The capacitive behavior of supercapacitors was systematically characterized by cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy. The specific capacitance of YP and SG capacitors reached 367 and 221 F g−1, respectively. Both types of capacitors demonstrated remarkably stable capacitance (capacitance retention >90%) along with excellent Coulombic efficiency (>99%) over 10,000 cycles. Compared to SG electrode, the better electrochemical performance achieved with YP electrodes was mainly due to shorter diffusion path, improved ionic mobility, and increased active surface area. The inexpensive lignin-based porous electrodes synthesized in this work can be used for various electrochemical devices for improved performance, decreased cost, and enhanced durability. This work also demonstrates that the selection of feedstock and appropriate processing conditions can tailor the structure of carbon composites for targeted applications. Techno-economic analysis indicates that YP and SG activated carbons can be produced at a minimum selling price of $8,493 and $6,670 per ton, respectively, which is competitive with the commercially available supercapacitor-grade activated carbons.

Synthesis and Antibacterial Properties of Oligomeric Dehydrogenation Polymer from Lignin Precursors.

The lignin precursors of coniferin and syringin were synthesised, and guaiacyl-type and guaiacyl-syringyl-type oligomeric lignin dehydrogenation polymers (DHP and DHP-GS) were prepared with the bulk method. The carbon-13 nuclear magnetic resonance spectroscopy showed that both DHP-G and DHP-GS contained β-O-4, β-5, β-β, β-1, and 5-5 substructures. Extraction with petroleum ether, ether, ethanol, and acetone resulted in four fractions for each of DHP-G (C11–C14) and DHP-GS (C21–C24). The antibacterial experiments showed that the fractions with lower molecular weight had relatively strong antibacterial activity. The ether-soluble fractions (C12 of DHP-G and C22 of DHP-GS) had strong antibacterial activities against E. coli and S. aureus. The C12 and C22 fractions were further separated by preparative chromatography, and 10 bioactive compounds (G1–G5 and GS1–GS5) were obtained. The overall antibacterial activities of these 10 compounds was stronger against E. coli than S. aureus. Compounds G1, G2, G3, and GS1, which had the most significant antibacterial activities, contained β-5 substructures. Of these, G1 had the best antibacterial activity. Its inhibition zone diameter was 19.81 ± 0.82 mm, and the minimum inhibition concentration was 56.3 ± 6.20 μg/mL. Atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) showed that the antibacterial activity of G1 was attributable to a phenylcoumarin dimer, while the introduction of syringyl units reduced antibacterial activity.

Diversification of Chemical Structures of Methoxylated Flavonoids and Genes Encoding Flavonoid-O-Methyltransferases.

The O-methylation of specialized metabolites in plants is a unique decoration that provides structural and functional diversity of the metabolites with changes in chemical properties and intracellular localizations. The O-methylation of flavonoids, which is a class of plant specialized metabolites, promotes their antimicrobial activities and liposolubility. Flavonoid O-methyltransferases (FOMTs), which are responsible for the O-methylation process of the flavonoid aglycone, generally accept a broad range of substrates across flavones, flavonols and lignin precursors, with different substrate preferences. Therefore, the characterization of FOMTs with the physiology roles of methoxylated flavonoids is useful for crop improvement and metabolic engineering. In this review, we summarized the chemodiversity and physiology roles of methoxylated flavonoids, which were already reported, and we performed a cross-species comparison to illustrate an overview of diversification and conserved catalytic sites of the flavonoid O-methyltransferases.

Lignin Synthesis, Affected by Sucrose in Lotus (Nelumbo nucifera) Seedlings, Was Involved in Regulation of Root Formation in the Arabidopsis thanliana.

Adventitious roots (ARs) have an unmatched status in plant growth and metabolism due to the degeneration of primary roots in lotuses. In the present study, we sought to assess the effect of sucrose on ARs formation and observed that lignin synthesis was involved in ARs development. We found that the lignification degree of the ARs primordium was weaker in plants treated with 20 g/L sucrose than in 50 g/L sucrose treatment and control plants. The contents of lignin were lower in plants treated with 20 g/L sucrose and higher in plants treated with 50 g/L sucrose. The precursors of monomer lignin, including p-coumaric acid, caffeate, sinapinal aldehyde, and ferulic acid, were lower in the GL50 library than in the GL20 library. Further analysis revealed that the gene expression of these four metabolites had no novel difference in the GL50/GL20 libraries. However, a laccase17 gene (NnLAC17), involved in polymer lignin synthesis, had a higher expression in the GL50 library than in the GL20 library. Therefore, NnLAC17 was cloned and the overexpression of NnLAC17 was found to directly result in a decrease in the root number in transgenic Arabidopsis plants. These findings suggest that lignin synthesis is probably involved in ARs formation in lotus seedlings.

Monolignol export by diffusion down a polymerization-induced concentration gradient.

Lignin, the second most abundant biopolymer, is a promising renewable energy source and chemical feedstock. A key element of lignin biosynthesis is unknown: how do lignin precursors (monolignols) get from inside the cell out to the cell wall where they are polymerized? Modeling indicates that monolignols can passively diffuse through lipid bilayers, but this has not been tested experimentally. We demonstrate significant monolignol diffusion occurs when laccases, which consume monolignols, are present on one side of the membrane. We hypothesize that lignin polymerization could deplete monomers in the wall, creating a concentration gradient driving monolignol diffusion. We developed a two-photon microscopy approach to visualize lignifying Arabidopsis thaliana root cells. Laccase mutants with reduced ability to form lignin polymer in the wall accumulated monolignols inside cells. In contrast, active transport inhibitors did not decrease lignin in the wall and scant intracellular phenolics were observed. Synthetic liposomes were engineered to encapsulate laccases, and monolignols crossed these pure lipid bilayers to form polymer within. A sink-driven diffusion mechanism explains why it has been difficult to identify genes encoding monolignol transporters and why the export of varied phenylpropanoids occurs without specificity. It also highlights an important role for cell wall oxidative enzymes in monolignol export.

Optimization of high‐quality carbon fiber production from electrospun aligned lignin fibers

AbstractIn recent years, investigating lignin as an alternative carbon fiber precursor has received immense research attention as a way to reduce the cost and replace the unsustainable conventional petroleum‐based precursors for carbon fiber production. The predominant challenge for lignin‐based carbon fibers is its low mechanical performance compared to conventional ones. In this work, mechanical properties of electrospun lignin carbon fiber mats were shown to be considerably enhanced via alignment of the submicron fibers. Over 60% of the fibers were aligned via a rotating drum collector utilized during fiber production. The main electrospinning parameters, namely electric field, rotating speed, and flow rate were optimized with the Box–Behnken method to enhance mechanical properties with reduced fiber diameter and improved fiber alignment. The optimal electrospinning process parameter was achieved at 2000 rpm collection speed, 80 kV/m electric field, and 440 nl/s flow rate. The lignin carbon fibers produced under the optimized condition exhibited elastic modulus of 3145.47 ± 917.75 MPa, tensile strength of 18.78 ± 6.11 MPa, and average fiber diameter of 697.07 ± 96.41 nm. The analysis on the interactions between electrospinning parameters has laid a solid foundation for the production of high‐quality carbon fibers from lignin precursor.

Chemically Accelerated Stabilization of a Cellulose-Lignin Precursor as a Route to High Yield Carbon Fiber Production.

The production of carbon fiber from bio-based or renewable resources has gained considerable attention in recent years with much of the focus upon cellulose, lignin, and cellulose-lignin composite precursor fibers. A critical step in optimizing the manufacture of carbon fiber is the stabilization process, through which the chemical and physical structure of the precursor fiber is transformed, allowing it to withstand very high temperatures. In this work, thermogravimetric analysis (TGA) is used to explore and optimize stabilization by simulating different stabilization profiles. Using this approach, we explore the influence of atmosphere (nitrogen or air), cellulose-lignin composition, and alternative catalysts on the carbon yield, efficiency, and rate of stabilization. Carbon dioxide and water vapor released during stabilization are analyzed by Fourier transform infrared (FTIR) spectroscopy, providing further information about the stabilization mechanism and the accelerating effect of oxygen and increased char yield (carbon content), especially for lignin. A range of different catalysts are evaluated for their ability to enhance the char yield, and a phosphorus-based flame retardant (H3PO4) proved to be the most effective; in fact, a doubling of the char yield was observed.

Equilibrium, kinetics and breakthrough curves of acetaminophen adsorption onto activated carbons from microwave-assisted FeCl3-activation of lignin

• Activated carbons are synthesized by chemical activation with FeCl 3 using microwave heating. • The carbons show a microporous structure and total surface areas higher than 1150 m 2 ·g −1. • Acetaminophen adsorption capacity is close to 300 mg·g −1. • Experimental and modelling equilibrium, kinetics and breakthrough adsorption tests are performed. • Complete recovery of adsorption capacity after easy regeneration step is achieved. Activated carbons have been prepared by chemical activation of lignin with FeCl 3 using microwave (MW) heating. The use of MW significantly reduced the activation time compared to conventional heating. Microwave power, impregnation ratio (R: mass ratio of FeCl 3 to lignin precursor) and MW holding time have been studied as variables affecting the development of porous texture. The optimum conditions were found at 800 W, R = 5 and 30 min MW heating time. Under those conditions an essentially microporous activated carbon was obtained, with BET surface area higher than 1150 m 2 ·g −1 and acidic surface, whose pH at the point of zero charge was 4.2. This activated carbon was tested for the adsorption of acetaminophen, as model emerging contaminant, from aqueous phase. The adsorption isotherms, obtained at 20, 40 and 60 °C, fitted well to Redlich–Peterson model. The maximum acetaminophen adsorption reached about 300 mg·g −1 at 60 °C. Values of 35.5 kJ·mol −1 and 238.3 J·mol −1 ·K −1 were obtained for the enthalpy and entropy of adsorption, respectively. Those positive values are indicative of an endothermic process and increased randomness at the solid/solution interface upon adsorption. The adsorption kinetics was better described by pseudo-second order driving force model. Breakthrough curves were also obtained at different adsorption temperatures, flow rates and acetaminophen inlet concentrations. They fitted well to a logistic-type equation representative of the Bohart-Adams, Thomas and Yoon-Nelson models. Adsorbent regeneration with hot water (80 °C) revealed easy and complete desorption thus providing a promising view of the potential application of this activated carbon.

Flexible and self-standing polyimide/lignin-derived carbon nanofibers for high-performance supercapacitor electrode material applications

For attaining flexible and self-standing electrode materials for advanced energy storage devices, we herein report the fabrication and electrochemical properties of carbon nanofibers (CNFs) derived from polyimide (PI) and lignin precursors with different mass ratios (10/0, 9/1, 8/2, and 7/3) via electrospinning and carbonization at 1000 °C. The electron microscopic and photographic images exhibit that the average diameter and flexibility of PI/lignin-derived CNFs decreases and increases, respectively, with increasing the lignin mass ratio in the precursors. The EDS, XRD and Raman analyses confirm that PI/lignin-derived CNFs possess a partially ordered graphitic structure with oxygen self-doping. The electrical conductivity of the CNFs increases from 1.5 S/cm to 2.8 S/cm with the increment of the lignin mass ratio in the precursors. Accordingly, PI/lignin (7/3)-derived CNF is found to have the most excellent electrochemical properties from the analyses using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) test, and electrochemical impedance spectroscopy (EIS). For a symmetric two-electrode supercapacitor based on PI/lignin (7/3)-derived CNFs, high specific capacitance of 83.6 F/g at 1 A/g, power density of 5000 W/kg, energy density of 13.3 Wh/kg, and capacitance retention of ∼100% after 1000 GCD cycle are attained.