Valorization of bagasse alkali lignin to water-soluble derivatives through chemical modification

Abstract

Black liquor is the by-product of the pulping process where the lignin, hemicellulose, and extractive materials are separated from wood to produce paper pulp. As one of the primary lignin sources, black liquor is considered an important energy source from biomass to produce biofuels and value-added chemicals. However, soda alkaline lignin has limited industrial applications due to its insolubility in water and lack of reactivity. Therefore, chemical modification is essential to enhance its industrial applications. In this study, alkali lignin from bagasse was modified through sulfonation, sulfomethylation, and amination processes using different reaction conditions. The structural analysis of obtained products was investigated by FTIR and 1 H-NMR. The molecular weight distribution and thermal stability of the watersoluble products were analyzed using gel permeation chromatography (GPC) and thermogravimetric analysis (TGA), respectively. The elemental analysis was used to measure the elements (CHNSO) of the obtained water-soluble derivatives. The chemical structure analysis of the samples with FTIR and 1 HNMR confirmed the modification processes. The results indicate that modification led to increased water solubility and a decrease in the precipitation pH of lignin samples, due to the introduction of sulfonate and amin functunal groups on lignin. In addition, the molecular weight and thermal stability of modified lignins were increased due to the presence of sulfonate and amine groups compared to unmodified lignin.

Antimicrobial Peptide-Inspired Design of Amino-Modified Lignin with Improved Antimicrobial Activities

“…The results of TGA studies revealed that aminated lignin had lower thermal stablitiy than kraft lignin . On the other hand, the introduction of funtional groups, like sulfonates that enhanced intermolecular interactions of lignin molecules, should improve the thermal stability of lignin . Jiao et al compared the thermal stability of aminated lignin with different functional groups.…”

“…29 On the other hand, the introduction of funtional groups, like sulfonates that enhanced intermolecular interactions of lignin molecules, should improve the thermal stability of lignin. 30 Jiao et al 31 compared the thermal stability of aminated lignin with different functional groups. The results revealed that the fuctional groups with branch structure resulted in modified lignin with lower thermal stability.…”

Interfacial Adsorption of Oil-Soluble Kraft Lignin and Stabilization of Water-in-Oil Emulsions

“…In surfactant chemistry, the modulation of physicochemical properties is often the goal, whereas other approaches may seek to enable or improve the use in polymeric materials. , Concerning the latter, increasing the reactivity of lignin is frequently the goal, which can be achieved by alkylation (epoxy resins), allylation or alkynylation, , phenolation (phenolic resins), or carboxylation (polyesters) . Water-solubility for the use as surfactants is usually facilitated by adding ionizable moieties, e.g., by sulfonation, sulfomethylation, or carboxylation . The opposite effect, i.e., hydrophobization and lipophilization, can be achieved by silylation or esterification with fatty acids. , Such treatments have also been demonstrated to improve compatibility with olefin thermoplastics, e.g., polyethylene or polypropylene. ,, It has also been demonstrated that Kraft lignin esterified with fatty acids was soluble in nonpolar solvents .…”

Water‐soluble Lignosulfonates: Structure, Preparation, and Application

“…For example, researchers prepared sulfomethylated lignin by inserting metabisulfite into the sulfonation process with the help of nitric acid and formaldehyde, increasing the sulfonation levels to 2.05 meq g −1 [18] . From the viewpoint of molecular weight and degree of sulfonation, Hui [19] evaluated different sulfonation methods, including high‐temperature sulfonation, sulfomethylation, butane sulfonolactone sulfonation, and sodium borohydride treatment of butane sulfonolactone sulfonation products [20] . A sulfonate group was added, and it was found that not only did it lighten the color of lignin for more industrial uses, but it also kept its molecular weight and even increased it in some ways, making the original lignin more stable at high temperatures [21] …”

“…[18] From the viewpoint of molecular weight and degree of sulfonation, Hui [19] evaluated different sulfonation methods, including high-temperature sulfonation, sulfomethylation, butane sulfonolactone sulfonation, and sodium borohydride treatment of butane sulfonolactone sulfonation products. [20] A sulfonate group was added, and it was found that not only did it lighten the color of lignin for more industrial uses, but it also kept its molecular weight and even increased it in some ways, making the original lignin more stable at high temperatures. [21] As lignosulfonates are dissolved in water, the hydrophobic skeleton of C 3 -C 6 forms a spherical structure.…”