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Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The high content of lignin is the major disadvantage for kenaf fiber separation. In order to remove lignin effectively as well as to improve the dispersion of kenaf fibers, a novel degumming process with steam explosion followed by Fenton treatment was applied in the present study. Fibers prepared by traditional chemical degumming process and raw kenaf samples were employed as control. The fiber microstructure, chemical composition, and physical and mechanical properties were characterized and analyzed in this paper. The results revealed that steam explosion coupled with Fenton treatment could effectively remove the gum materials from kenaf bast, which performed noticeably effectively in lignin removal. The refined dry fibers showed a clean and smooth surface. The average fineness of the refined dry fibers degummed by the novel process was measured to be higher than 70 dtex, which is much better than fibers prepared by the traditional chemical degumming process. It can be concluded that the novel degumming process of combined steam explosion and Fenton treatment is feasible and effective for kenaf degumming. [ABSTRACT FROM AUTHOR]

Degumming is the dominant method to isolate cellulosic fibers in the textile industry. High content of lignin is the principle obstacle in bast-fibers degumming. In order to remove lignin efficiently, the treatment using steam explosion coupled with Fenton oxidation was conducted on kenaf bast in this study. The influence and mechanism of the combined treatment of steam explosion and Fenton oxidation were studied. Fiber microstructure, composition proportion and distribution, cellulose Segal crystallinity and polymerization as well as residual lignin structure were analyzed. The results showed that the pretreatment of steam explosion could sufficiently extract most of the hemicellulose from kenaf bast. Also, the Fenton oxidation followed by alkaline boiling could effectively remove the lignin from the fiber, especially from the fiber surface. The refined dry fibers produced only remained 8.82% of hemicellulose and 9.36% of lignin. And the whole treatment process didn’t change the cellulose crystalline structure but could gradually degrade hemicellulose, lignin and other amorphous gummy matter as well as disordered areas in cellulose, leading to the increase of fiber Segal crystallinity from 62.02 to 70.12%. Part of cellulose was damaged with the increase of degumming intensity, resulting in the decrease of the polymerization degree of cellulose. Meanwhile, the structure of residual lignin changed during the degumming stages of steam explosion, Fenton oxidation and alkaline boiling. All the results revealed that the treatment of combined steam explosion and Fenton oxidation is significantly effectual for isolating bast-fibers. [ABSTRACT FROM AUTHOR]

To enhance the degumming effect of steam explosion on kenaf fiber, different chemical reagents including hydrogen peroxide (H2O2), sulfuric acid (H2SO4), and sodium hydroxide (NaOH) presoak combined with steam explosion were used and compared in this article. Distilled water coupled with steam explosion treatment and kenaf raw samples were used as control. The fiber morphology, chemical composition, crystalline structure, degree of fineness, and breaking tenacity of kenaf fibers after treatment were studied. The results showed that hydrogen peroxide (H2O2) performs better on removing lignin. It not only splits fibers, but also keeps the fiber's tenacity during steam explosion treatment. Dilute sulfuric acid (H2SO4) performs better on hemicellulose removal, but it damages the fiber cellulose during steam explosion treatment and cause the fiber strength decrease a lot. Sodium hydroxide (NaOH) performs the best on removing hemicellulose and lignin, and splits fiber well. However, the breaking tenacity of the fiber is lower than the fiber pretreated by H2O2. Besides, NaOH is a pollutant to the environment. In conclusion, H2O2 could be considered as the most promising reagent to be used in combined presoak-steam explosion system. [ABSTRACT FROM AUTHOR]

The study of the main chemical composition degradation, especially cellulose degradation at high temperatures and within high moisture environments, provides important information that can guide biomass processing using steam explosion (STEX) and other similar treatments. In this paper, kenaf bast was treated using STEX at pressures of 0.5, 1.0, and 1.5 MPa. The chemical composition change and the infrared spectra were investigated. The crystalline index and degree of polymerization of kenaf cellulose were also quantified. It was found that pectin and hemicellulose could be easily degraded with the STEX treatment, while lignin only exhibited slight decomposition; cellulose degraded at 1.5 MPa STEX treatment on the kenaf. Research also indicates that cellulose with a low molecular weight can be removed with a low-pressure STEX treatment. By coupling STEX with chemical degumming process, the high-quality kenaf fiber with 7.12% residue gum content and 134.5 Nm fineness can be obtained. [ABSTRACT FROM AUTHOR]

Phloem biomass has gradually attracted attention for its conversion and utilization due to its fast growth rate and suitability for textile use. Currently, clean methods for separating the chemical components of biomass have attracted attention. In this study, the choline chloride-lactic acid (CLA) and choline chloride-glycolic acid (CGA) pretreatment were developed for kenaf chemical components separation, and the solid residue and regenerated lignin were characterized. The results demonstrated that two acidic deep eutectic solvents (DESs) pretreatment had good removal capacities for lignin and hemicellulose even when the kenaf was not crushed. Under optimal treatment conditions, the retention rates of cellulose were 82.4% and 81.1%, respectively. The cellulose content in the recovery solids residues reached 91.5% and 91.3%, which also resulted in good enzymatic hydrolysis conversion efficiency (85.4% and 84.9%). The regenerated lignin exhibited high purity (91.9% and 90.1%), and low molecular weight (1209 and 1086 g/mol), which was attributed to the amount of ether bonds cleavage in lignin. Meanwhile, the DES exhibited a good ability to recycle and reuse. Overall, acidic DES pretreatment holds promise for efficient fractionation and component utilization of kenaf phloem biomass. • Two acidic DESs could directly and effectively isolate kenaf lignin and retent the high purity cellulose component. • The removal of lignin by DES pretreatment improved the enzymatic hydrolysis efficiency of solid residues. • The different pretreatment effects of lactic acid DES and glycolic acid DES were investigated. • The acidic DES regenerated lignin exhibited high purity (91.9% and 90.1%), and low molecular weight (1209 and 1086 g/mol). [ABSTRACT FROM AUTHOR]

The traditional textile degumming process produces abundant wastewater, which contains a lot of monosaccharides and oligosaccharides. It is of great economic and environmental significance to utilize these carbohydrates in high value. In this study, high performance liquid chromatography (HPLC) was used to analyze the carbohydrate components in kenaf degumming wastewater, and then the production of C-dots using the wastewater was explored. The results showed that the types and content in the degumming wastewater were monosaccharides (glucose, xylose and arabinose) and oligosaccharides (dextran, xylan and araban). The carbohydrate (mainly glucan and xylan) content in wastewater accounted for 91.16 % of the total carbohydrates weight loss in kenaf degumming process. By using hydrolysis and hydrothermal reaction on kenaf degumming wastewater, blue-green carbon dots (C-dots) with good performance were prepared and successfully applied to anti-counterfeiting printing. In particular, the as-prepared C-dots prepared from kenaf degumming wastewater with urea added (WUC-dots) showed an excitation-dependent photoluminescence (PL) spectrum and quantum yield (QY) of 2.4 % in aqueous solution. The fluorescent code exhibited a clear outline, excitation-tunable color and good stability, showing a great potential for anti-counterfeiting system. [ABSTRACT FROM AUTHOR]

Traditional degumming methods of bast fibers are largely limited due to long procedures, high energy consumption, serious environmental pollution, or low efficiency. In this study, deep eutectic solvents (DESs) synthesized with hydrogen bond acceptor (HBA) and three representative hydrogen bond donors (HBDs) were applied to kenaf bast degumming. The morphologies, chemical compositions, crystallinities, polymerization degrees and physical properties of the kenaf fibers were determined. The effects and mechanisms of different DESs on dispersing kenaf bast were discussed. The results showed that alkalinity amide DES (ChCl-urea, CU) showed the best degumming effect. The optimal processing temperature is 160 °C and the processing time is 2 h. Due to competition from chloride ions, DES first weakens the hydrogen bond interaction in kenaf fibers. Then, the alkalinity amide DES removed lignin by deprotonation of phenolic hydroxyl groups and breakage of β-O-4 bonds for different lignin units. Finally, the solvent can be reused at least 3 times. The results showed that CU degumming treatment could effectively remove the gummy components in kenaf bast and had the potential to prepare refined dry kenaf fibers. This study provided a simple and green degumming method for kenaf bast. [Display omitted] • A facile and greener DES degumming method for preparation of kenaf fibers. • Recycable and reusable DES degumming waste. • The mechanisms of kenaf bast degumming by three kind of DESs. [ABSTRACT FROM AUTHOR]

• A method for splitting kenaf using microwave combined with lactic acid was proposed. • Fibers have excellent dispersion and suffer minor damage. • The extracted lignin is less damaged and keeps its structural integrity. • Potential for biomass clean production due to low chemicals and time consumption. According to diverse application purposes, different scales of lignocellulosic fibers were obtained from biomass through various preparation conditions. However, the pollution in the fiber separation process restricted the development of the related industry. This research proposed clean fiber separation technology of kenaf bast that combined microwave and lactic acid treatment. The traditional sulfate method was also carried out for comparison. The raw kenaf bast and produced fibers were characterized with wet chemistry analyses, SEM, FTIR, GPC and NMR. The results showed that compared with the traditional method (lignin removal rate 88.3 %, cellulose Mw = 607 kg/mol), the new method had higher lignin removal capacity (94.68 %) and less damage to cellulose (Mw = 1174 kg/mol). TG and NMR analysis showed that the separated crude lignin had a high pyrolysis temperature (350℃), minor structural changes and better uniformity, which was close to natural lignin. In addition, it was calculated that the processing time of the new method was reduced by 82.3 %, which reduced energy loss and waste liquid pollution. This study proved that microwave-assisted lactic acid treatment could separate kenaf fibers efficiently with less damage and pollution. [ABSTRACT FROM AUTHOR]