Sequential extraction of carbohydrates and lignin from agricultural waste and their structural characterization

Abstract

This work reports on the extraction and characterization of carbohydrates such as cellulose, cellulose nanofibres, hemicellulose, and lignin from agricultural waste, i.e. maize stalks and sugarcane bagasse. The chemical compounds were extracted by hot water extraction (HWE) followed by alkaline extraction with 10 wt.% of sodium hydroxide (NaOH). Cellulose nanofibres (CNF) were isolated by mechanical grinding the cellulose fraction using a supermass colloider. The characteristics of the different fractionated components were investigated using nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD). The removal of the hemicellulose, lignin and extractives were confirmed quantitatively by TAPPI standard methods. It was observed that the cellulose content and its crystallinity increased after treating maize stalks and sugarcane bagasse with hot water extraction and alkali treatment. The thermal stability of cellulose also improved after treatments. Transmission Electron Microscopy (TEM) results confirmed that web-shaped CNF were successfully extracted from the cellulose obtained from sugarcane bagasse and maize stalks. The dimensions of the CNF ranged from 5 to 30 nm in width and a few microns in length. In future studies, the fractionated hemicellulose, lignin and (micro and nano) cellulose will be used as reinforcements in the development of biocomposite materials.

Fabrication of a Polybutylene Succinate (PBS)/Polybutylene Adipate-Co-Terephthalate (PBAT)-Based Hybrid System Reinforced with Lignin and Zinc Nanoparticles for Potential Biomedical Applications

“…The strong absorption band at 3388 cm −1 assigned to OH stretching and the absorption band at wavenumbers of 2974 cm −1 corresponds to the methyl and methylene groups of lignin. The strong absorption band at 1571 cm −1 and 1417 cm −1 corresponds to the aromatic structure of lignin [ 35 , 36 ]. The absorption bands at 1185 cm −1 and 1117 cm −1 belong to the ester bonds of p-hydroxyphenyl propane units and ether– O for the syringyl structures, respectively, while the band at 1020 cm −1 corresponds to the –CH=CH– group out of plane deformation [ 36 , 37 ].…”

“…The strong absorption band at 1571 cm −1 and 1417 cm −1 corresponds to the aromatic structure of lignin [ 35 , 36 ]. The absorption bands at 1185 cm −1 and 1117 cm −1 belong to the ester bonds of p-hydroxyphenyl propane units and ether– O for the syringyl structures, respectively, while the band at 1020 cm −1 corresponds to the –CH=CH– group out of plane deformation [ 36 , 37 ]. The bands between 600 cm −1 and 700 cm −1 represent the sulphonic groups [ 35 ].…”

“…The thermal degradation of lignin occurred in three steps. The lignin thermogram showed a small weight loss in the region of 50–120 °C, which is due to the evaporation of moisture and the low molecular weight materials [ 36 ]. During the heating of lignin in the temperature range between 120 °C to 900 °C, a huge mass loss was observed at 265.7 °C and 729.1 °C, which was attributed to the release of volatiles such as carbon dioxide and methane, in addition to SO 2 and mercaptans from the lignin [ 35 ].…”

“…This indicates that lignin is thermally less stable when compared with the aforementioned materials. The char residue in the case of lignin was attributed to the complex aromatic nature of the lignin [ 36 ]. In the case of the blend and hybrid composites, the degradation occurred in a single major weight loss step.…”

Antioxidant Activities, Anticancer Activity, Physico-Chemistry Characteristics, and Acute Toxicity of Alginate/Lignin Polymer

“…The solvent of D 2 O and 01% CD 3 COOD with an internal standard of DSS and water reduction measurement technique was used for the 13 C NMR spectroscopy of sodium alginate [10] (Figure S2). The 1 H NMR analysis of maize stalks lignin was conducted with C 2 D 6 OS solvent and tetramethylsilane as a standard for calibrating the peaks shift [44]. According to Mtibe et al, the shift from 1.5 to 2.4 ppm shows the presence of the group of aromatics [44] (Figure S3).…”