The search for alternative methods for the production of new materials or fuel from renewable and sustainable biomass feedstocks has gained increasing attention. In this study, Nypa fruticans (nipa palm) fronds from agricultural residues were evaluated to produce pure cellulose by combining prehydrolysis for 1–3 h at 150 °C, sulfur-free soda cooking for 1–1.5 h at 160 °C with 13–25% active alkali (AA), 0.1% soluble anthraquinone (SAQ) catalyst, and three-stage totally chlorine-free (TCF) bleaching, namely oxygen, peroxymonosulfuric acid, and alkaline hydrogen peroxide stages. The optimal conditions were 3 h prehydrolysis and 1.5 h cooking with 20% AA. Soda cooking with SAQ was better than the kraft and soda process without SAQ. The method decreased the kappa number as a residual lignin content index of pulp from 13.4 to 9.9–10.2 and improved the yields by approximately 6%. The TCF bleaching application produced pure cellulose with a brightness of 92.2% ISO, 94.8% α-cellulose, viscosity of 7.9 cP, and 0.2% ash content. These findings show that nipa palm fronds can be used to produce pure cellulose, serving as a dissolving pulp grade for viscose rayon and cellulose derivatives.

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Nypa fruticans Frond Waste for Pure Cellulose Utilizing Sulphur-Free and Totally Chlorine-Free Processes

Lignin has a natural polyphenol structure that is expected to replace chemically synthesized antioxidants as a native antioxidant with biodegradable and convenient source characteristics. However, the improvement of the antioxidant property of lignin and its application as an antioxidant are still somewhat limited due to the lack of understanding of the relationship between specific lignin structures and antioxidant property. Therefore, the study of the relationship between lignin structure and antioxidant property is crucial to realize the high-quality application of lignin. In this experiment, the scavenging ability of free 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radicals was determined for different grades of acetylated tannins, typical lignin model compounds and different structural units of milled wood lignin to investigate the relationship between lignin structure and antioxidant property. Based on the experimental results, some structure-activity relationships were proposed and the mechanism of the antioxidant property of lignin was discussed. The number of phenolic hydroxyl groups was linearly and positively correlated with antioxidant property, and the scavenging of DPPH radicals increased significantly with the increase in the number of methoxy groups in the model compounds. Moreover, aldehyde and carboxyl groups had a negative effect on the antioxidant property of lignin, while methoxy, alkyl and alcohol hydroxyl groups played a positive role. The guaiacyl (G) and syringyl (S) units favored the antioxidant property, so the difference in the content of structural units in lignin under certain conditions of phenolic hydroxyl content also affected the antioxidant property. Therefore, the antioxidant property of aspen milled lignin was higher than that of other milled lignin from different wood species. Finally, the mechanism of DPPH free radical scavenging by lignin was revealed to better understand the relationship between lignin structure and antioxidant property. 

Exploring the relationship between lignin structure and antioxidant property using lignin model compounds

Phenolation of potassium hydroxide lignin and its effect on copolymerization with acrylic acid

Abstract The overproduction of pollutants resulting from the development of industry causes the deposition of large amounts of toxic and carcinogenic substances, including heavy metals, in the aquatic ecosystem and other ecosystems. This is a civilisation problem of the present times, posing a serious threat to the natural environment, including humans. For this reason, it has recently become extremely important to develop effective methods to minimise the concentration of heavy metal ions in the aquatic systems and thus reduce their negative impact on the environment. One such technique is adsorption, which is believed to be an effective method of removing contaminants such as heavy metal ions from aqueous solutions. Looking at the available literature of the last few years, it can be concluded that adsorbents of natural origin are becoming more and more important. These are agricultural waste, all kinds of biomass, and waste from various industries. The study attempts to present and evaluate the sorption capacity of materials of natural origin, including oat bran, chitosan, alginate, tree bark, coconut fibre, and lignin. The use of such biosorbents is more friendly for the environment compared to their synthetic counterparts and perfectly fits the concept of sustainable development and the circular economy.

Removal of Heavy Metals from Aqueous Solutions with the Use of Lignins and Biomass

Abstract Non-wood pulping faces environmental and processing problems due to lack of suitable technology. To overcome the challenges, potassium hydroxide pulping was suggested, which can also be integrated with biorefinery. To make a viable biorefinery, all dissolved components need to be utilized. Therefore, in this paper, the dissolved lignin from the potassium hydroxide pulping of corn stalks and dhaincha was isolated and characterized by UV, FTIR, 1H-NMR, 31P-NMR and 2D-NMR spectroscopy and molecular weight and compared with the corresponding dioxane lignins. 1H-NMR and 2D-NMR indicated that potassium hydroxide pulping cleaved β-O-4 aryl ether linkages, and consequently increased phenolic hydroxyl group and reduced molecular weight. It was found that phenolation is an effective method to improve the reactivity and reduce molecular weight, and thus the lignin from the potassium hydroxide liquor was further phenolated. The penolated lignin showed strong NIR bands at 5970 and 6896 cm−1 for aromatic C-H and phenolic O-H group.

Characteristics of potassium hydroxide lignin from corn stalk and dhaincha

Prehydrolysis prior to pulping shows a beneficial effect in subsequent delignification and bleaching. Prehydrolysis of Acacia auriculiformis produced higher pulp yield in soda and soda-anthraquinone processes at similar kappa number than non-prehydrolyzed kraft process. In D0EpD1 bleaching sequences, delignification (DoEp kappa) and bleachability were better for prehydrolyzed A. auriculiformis pulp in the pulping processes studied. The lignin from prehydrolyzed wood chips was characterized with lower molecular weight and slightly higher phenolic hydroxyl group. This suggested the depolymerization of lignin in prehydrolysis process.

Effect of prehydrolysis on pulping and bleaching of Acacia auriculiformis A. Cunn. ex Benth.

The structural characteristics of the lignin from potassium hydroxide (KOH) liquor of jute stick (Corchorus capsularis) pulping were determined and compared with the isolated dioxane lignin from jute stick. The lignin structure was characterized by elemental, methoxyl group analysis, UV, FTIR, 1H-NMR, 31P-NMR, and 2D-NMR spectroscopy and molecular weight. 2D-NMR of both lignins isolated showed a predominance of β-O-4 aryl ether linkages. KOH pulping cleaved β-O-4 aryl ether linkage and increased phenolic hydroxyl group and reduced molecular weight. KOH lignin can replace 40% phenol in phenol-formaldehyde resin with satisfactory shear strength.

Structural characterization of potassium hydroxide liquor lignin and its application in biorefinery

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Effect of prehydrolysis on pulping and bleaching of Acacia auriculiformis A. Cunn. ex Benth.

Structural characterization of potassium hydroxide liquor lignin and its application in biorefinery