•Sonication had a significant effect on the alkaline extraction of hemicelluloses.•Xylans from hardwood obtained with or without ultrasound had similar structure.•Ultrasonication has potential in ...separating hemicelluloses at an industrial level.
Effect of sonication on the extractability and physico-chemical properties of hemicelluloses from Eucalyptus grandis using 5% KOH solution at 50 °C for 3 h has been comparatively studied. The results showed that the yield of hemicelluloses increased from 2.6 to 19.6% as the ultrasonic time was extended from 5 to 35 min. The highest yield of hemicelluloses (95.2%) was achieved at 30 min ultrasonic time. Xylose was the dominant sugar (82.94–84.96%) of all the hemicellulosic fractions. Furthermore, the hemicelluloses obtained by ultrasound-assisted extractions had slightly lower molecular weights (74,510–66,770 g/mol) and thermal stabilities, but higher contents of xylose (83.95–84.96%). The increased yield of ultrasonically extracted hemicelluloses, which have preserved their main structural properties, confirmed the great potential of ultrasound-assisted extraction to separate hemicelluloses from Eucalyptus grandis at an industrial level.
Display omitted
•The conversion of carbohydrates to monosaccharides is 87.0%.•Adding water to DES promotes the conversion of carbohydrate to monosaccharides.•Xylose yield from hydrated DES ...hydrolyzate is higher than that of DES.•Glucose yield from enzymatic hydrolysis increases by 10.3 times.
In this work, a rapid one-pot hydrated deep eutectic solvent (DES) pretreatment was proposed to facilitate the conversion of carbohydrates from lignocellulosic biomass to monosaccharides. Specifically, the pure and hydrated DES based on benzyl triethylammonium chloride (BTEAC), formic acid (FA) and water was used to pretreat bamboo shoot shells (BSS) by microwave heating. The pretreated solid residues were enzymatically saccharified to produce fermentable sugars, and the hydrolyzed carbohydrates and lignin remained in the hydrolyzate. The results showed that the yield of monosaccharides from the hydrated DES hydrolyzate (193.7–228.4 g/kg) was significantly higher than that (45.9–66.1 g/kg) of pure DES. The 30% hydrated DES pretreatment achieved the best glucose yield (89.03%) and a total monosaccharides yield of 555.4 g/kg, which corresponded to a conversion ratio of carbohydrates to monosaccharides of 87.0%. The proposed process is a robust method for the efficiently convert carbohydrates from BSS into monosaccharides.
Storage is a crucial part during grain production for the massive spoilage caused by stored product insects. Essential oils (EOs) of plant origin have been highly recommended to combating insects ...which are biodegradable and safe mode of action. Hence, to make the fullest use of natural resources, essential oils of different parts from Piper yunnanense (the whole part, PYW; fruits, PYF; leaves, PYL) and Piper boehmeriifolium (leaves, PBL) were extracted by steam distillation method in the present study. Gas chromatography‐mass spectrometry (GC‐MS) characterization revealed bicyclogermacrene (PYW), γ‐muurolene (PYF), δ‐cadinene (PYL) and methyl 4,7,10,13,16,19‐docosahexaenoate (PBL) as the principal compound of each essential oil. Sesquiterpene hydrocarbons were also recognized as the richest class accounting for 56.3 %–94.9 % of the total oil. Three storage pests, Tribolium castaneum, Lasioderma serricorne and Liposceis bostrychophila, were exposed to different concentrations of EOs to determine their insecticidal effects. All tested samples performed modest contact toxicity in contrast to a bioactive ingredient pyrethrin, among which the most substantial effects were observed in PYF EOs against T. castaneum (35.84 μg/adult), PBL EOs against L. serricorne (15.76 μg/adult) and PYW EOs against L. bostrychophila (57.70 μg/cm2). In terms of repellency tests, essential oils of PYF at 78.63 nL/cm2 demonstrated to have a remarkable repellence against T. castaneum at 2h and 4h post‐exposure. The investigations indicate diverse variations in the chemical profiles and insecticidal efficacies of P. yunnanense and P. boehmeriifolium EOs, providing more experimental evidence for the use of the Piper plants.
As one of the potential energy crops, Arundo donax Linn. is a renewable source for the production of biofuels and bioproducts. In the present study, milled wood lignin (MWL) and alkaline lignin (AL) ...from stems and foliage of A. donax were isolated and characterized by FT-IR spectroscopy, UV spectroscopy, GPC, 31P NMR, 2D HSQC NMR, and DFRC. The results indicated that both stem and foliage lignins were HGS type lignins. The semiquantitative HSQC spectra analysis demonstrated a predominance of β-O-4′ aryl ether linkages (71–82%), followed by β-β′, β-5′, β-1′, and α,β-diaryl ethers linkages in the lignins. Compared to stem lignins, foliage lignins had less β-O-4′ alkyl-aryl ethers, lower weight-average molecular weight, less phenolic OH, more H units, and lower S/G ratio. Moreover, tricin was found to incorporate into the foliage lignins (higher content of condensed G units) in significant amounts and might be alkaline-stable.
Elucidating the structural characteristics and changes of lignin during biorefining is considerably important for lignin valorization. To examine the structural transformations of lignin under deep ...eutectic solvent (DES) pretreatments, the double enzymatic lignin (DEL) isolated from Eucalyptus was pretreated with DES (ChCl/lactic acid, 1:10) under the conditions of 60–140 °C for 6 h. The structural transformations of lignin during the DES pretreatment have been investigated by quantitative 13C NMR, two-dimensional-heteronuclear single quantum correlation (2D-HSQC) NMR, 31P NMR, gel permeation chromatography (GPC), and scanning electron microscopy (SEM) techniques and the lignin degradation products recovered after DES pretreatment have been analyzed by gas chromatography–mass spectrometry (GC–MS) technique. NMR results demonstrated that the dissociation of aryl ether linkage (i.e., β–O–4) is dominant during the DES pretreatment, which is in line with the increased content of phenolic hydroxyl in these lignins. In addition, the decreased aliphatic hydroxyl groups suggested that the acylation or dehydration of aliphatic hydroxyl groups occurred as the pretreatment temperature elevated. Based on the results observed, possible pathways for chemical transformations of lignin were proposed. Furthermore, it was found that DES pretreatment also resulted in a homogeneous lignin morphology, facilitating the formation of lignin nanoparticles. In short, unmasking the lignin chemistry during the DES pretreatment will facilitate the optimization of the pretreatment process and production of homogeneous nanosized lignin particles with preferable chemical reactivity from parent lignin in the current biorefinery process.
Lignin, which can be recycled from bioethanol and paper production wastes, is the second largest renewable resource. However, studies and applications on sustainable upgrading of lignin are extremely ...limited and most of them only focus on its combustion to obtain energy. The abundance of reactive groups in lignin makes it a potential feedstock for the production of sustainable low carbon footprint value-added materials. Among them, the preparation of flocculants from lignin has attracted much attention. This paper systematically reviews recent progress of low carbon footprint lignin-based flocculants. The modification methods for the production of lignin-based flocculants, Mannich, sulfonation, carboxylation, crosslinking and graft copolymerization, and the flocculation mechanisms in wastewater treatment are discussed emphatically. Moreover, the factors affecting the flocculation performance of lignin-based flocculants, including internal factors, such as charge density, molecular weight, conformation, and external factors, such as dosage, treatment time, wastewater pH, and temperature are discussed in detail, which are conducive to design, production and application of lignin-based flocculants for lower carbon footprint. Furthermore, we critically point out the current deficiencies of the lignin-based flocculants and the challenges facing commercialization, then we propose the corresponding possible solutions. The production and application of high-efficiency lignin-based flocculants are of great significance for resource conservation, low carbon footprint, and wastewater reuse.
Display omitted
•Lignin show environmental advantages as a sustainable feedstock.•Commonly used chemical modification methods for lignin-based flocculants.•Applications of lignin-based flocculants in treatment of various wastewaters.•Flocculation mechanism and external factors affecting the flocculant mechanism.•The challenges facing the commercialization of lignin-based flocculants.
To improve yields while minimizing the extent of mechanical action (just 2 h of planetary ball-milling), the residual wood meal obtained from extraction of milled wood lignin (MWL) was sequentially ...treated with cellulolytic enzyme and alkali, and the yields of MWL, cellulolytic enzyme lignin (CEL), and alkaline lignin (AL) were 5.4, 23.2, and 16.3%, respectively. The chemical structures of the lignin fractions obtained were characterized by carbohydrate analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, and various advanced NMR spectroscopic techniques. The results showed that the lignin isolated as MWL during the early part of ball milling may originate mainly from the middle lamella. This lignin fraction was less degradable and contained more linear hemicelluloses and more CO in unconjugated groups as well as more phenolic OH groups. Both 1D and 2D NMR spectra analyses confirmed that the lignin in triploid of Populus tomentosa Carr. is GSH-type and partially acylated at the γ-carbon of the side chain. Two-dimensional heteronuclear single-quantum coherence (13C–1H) NMR of MWL, CEL, and AL showed a predominance of β-O-4′ aryl ether linkages (81.1–84.5% of total side chains), followed by β-β′ resinol-type linkages (12.2–16.4%), and lower amounts of β-5′ phenylcoumaran (2.1–2.6%) and β-1′ spirodienone-type (0.4–1.4%) linkages. The syringyl (S)/guaiacyl (G) ratios were estimated to be 1.43, 2.29, and 2.83 for MWL, CEL, and AL, respectively.
Understanding of the fundamental chemistry of lignin macromolecules in lignocellulosic biomass will facilitate the further development of renewable biofuel and biomaterial production. In the present ...study, to thoroughly delineate the detailed structural characteristics of the native lignin in the three major Eucalyptus woods, MWL, CEL, and EHL preparations were sequentially isolated from the diverse Eucalyptus wood. Parallelly, a modified enzyme lignin (DEL) based on double ball-milling and enzymatic hydrolysis was also prepared with superhigh yield (102.5–109.5%) from same Eucalyptus wood. The structural characteristics of all the lignin preparations were elaborately investigated by HPAEC, GPC, and NMR techniques (2D-HSQC and 31P NMR). Results showed that the contents of different substructures (β-O-4, β-β, β-5, and β-1) and S/G ratios of lignin macromolecules varied among these Eucalyptus species. As compared to the β-O-4 content in the extracted lignins (MWLs and CELs, 44.5–60.2/100Ar), the residual lignins (EHLs and DELs) exhibited a higher content of β-O-4 linkages (59.1–64.3/100Ar). DEL preparations can be served as “lignin preparation” to develop a depolymerization strategy of lignin due to the higher content of β-O-4 linkages and abundant syringyl units. Moreover, the sufficient understanding of lignin will facilitate subsequent process of these Eucalyptus species for producing of biochemicals, bioenergy, and biomaterials.
Lithium‒sulfur (Li–S) battery is considered as a promising energy storage system to realize high energy density. Nevertheless, unstable lithium metal anode emerges as the bottleneck toward practical ...applications, especially with limited anode excess required in a working full cell. In this contribution, a mixed diisopropyl ether‐based (mixed‐DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li–S batteries with sulfurized polyacrylonitrile (SPAN) cathodes. The mixed‐DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides, rendering significantly improved cycling stability. Concretely, Li | Cu half‐cells with the mixed‐DIPE electrolyte cycled stably for 120 cycles, which is nearly five times longer than that with routine carbonate‐based electrolyte. Moreover, the mixed‐DIPE electrolyte contributed to a doubled life span of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte. This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high‐energy‐density Li‒S batteries.
A mixed diisopropyl ether‐based (mixed‐DIPE) electrolyte was proposed to forcefully protect the lithium metal anode in working lithium–sulfur batteries with sulfurized polyacrylonitrile (SPAN) cathodes.
•Lignin-phenol-formaldehyde (LPF) resin was a promising wood adhesive.•Organosolv lignins from bamboo were ideal materials for LPF resin synthesis.•The synthesis of LPF resin was disturbed by ...long-chain hydrocarbon derivatives.•The performance of a LPF resin was affected by various factors.
The synthesis and performance of a lignin-phenol-formaldehyde resin are significantly related to the properties of the lignin used. In an effort to provide a fundamental understanding of lignin structure-property relations for lignin-phenol-formaldehyde resin synthesis and application, two distinct technical lignins were examined as-obtained from an acidic (L1) and an alkaline (L2) organosolv pulping of bamboo. These samples were thoroughly characterized and the structural and compositional features of them were charted. The content of β-O-4′ linkages in L1 were 23.83 per 100Ar, followed by some β-β′ linkages (1.27 per 100Ar). However, almost all the side-chain linkages in L2 were cleaved. The purities of the two lignins both exceeded 81.0%, but significantly more extractives were found to be present in L2. Subsequently, two lignin-phenol-formaldehyde resins were successfully synthesized using L1 and purified L2 at a substitution rate of 50% to phenol. The high content of extractives contaminating L2, especially long-chain hydrocarbon derivatives, severely affected the synthesis of lignin-phenol-formaldehyde resin. The successful removal of this fraction was necessary before the material could be put to use.
PDF
