Acacia Wood Fractionation Using Deep Eutectic Solvents: Extraction, Recovery, and Characterization of the Different Fractions

Abstract

The selective extraction and recovery of different lignocellulosic molecules of interest from forestry residues is increasing every day not only to satisfy the needs of driving a society toward more sustainable approaches and materials (rethinking waste as a valuable resource) but also because lignocellulosic molecules have several applications. For this purpose, the development of new sustainable and ecologically benign extraction approaches has grown significantly. Deep eutectic solvents (DESs) appear as a promising alternative for the processing and manipulation of biomass. In the present study, a DES formed using choline chloride and levulinic acid (ChCl:LA) was studied to fractionate lignocellulosic residues of acacia wood ( Acacia dealbata Link), an invasive species in Portugal. Different parameters, such as temperature and extraction time, were optimized to enhance the yield and purity of recovered cellulose and lignin fractions. DESs containing LA were found to be promising solvent systems, as the hydrogen bond donor was considered relevant in relation to lignin extraction and cellulose concentration. On the other hand, the increase in temperature and extraction time increases the amount of extracted material from biomass but affects the purity of lignin. The most promising DES system, ChCl:LA in a ratio of 1:3, was found to not significantly depolymerize the extracted lignin, which presented a similar molecular weight to a kraft lignin. Additionally, the 31 P NMR results revealed that the extracted lignin has a high content of phenolic OH groups, which favor its reactivity. A mixture of ChCl:LA may be considered a fully renewable solvent, and the formed DES presents good potential to fractionate wood residues.

Extraction and characterisation of kudzu root residue lignin based on deep eutectic solvents

“…31 P NMR spectroscopy has been widely used to quantify the lignin extracted. On the basis of previous literature, 32,54 the quantitative figure is presented in Figure 10.…”

“…NMR spectroscopy has been widely used to quantify the lignin extracted. On the basis of previous literature,32,54 the quantitative figure is presented in Figure10.The order of OH group contents of PLL isolated from kudzu root residue was: phenolic OH (136-144 ppm) > aliphatic OH (145-152 ppm) > carboxylic OH (133-136 ppm). The higher total amounts of phenolic hydroxyl groups in the 136-144 ppm region were attributed to the β-O-4 ether bonds in the lignin extraction process 47.…”

“…30,31 Magalhães et al assessed ChCl-based DESs regarding their performance in the fractionation of lignocellulosic residues of acacia wood. 32 The results indicated that the DES containing levulinic acid (LA) exhibited significant lignin selectivity, leading to high extraction yields and purity of the separation material, which is helpful for the conversion of lignocellulose biomass to new varied chemicals and biomaterials. 33,34 On the other hand, Varilla-Mazaba et al used DES (ChCl-Gly and ChCl-Urea) for delignification, and its removal rate could reach 81.1% and 82.0%.…”

Eco-Friendly Methods for Extraction and Modification of Cellulose: An Overview

“…90% purity and a yield of nearly 60% ( w / w ) of the total lignin present in different sources, such as corn straw [ 68 ]. Systems composed of choline chloride (ChCl) and lactic acid [ 69 ], ChCl and monoetanolamine [ 67 ], and ChCl and levulinic acid [ 70 ] are particularly efficient in biomass pretreatment. These DES are claimed to promote proton-catalyzed cleavage of various chemical linkages (e.g., ether and ester bonds) in the lignin-carbohydrate complex and in lignin molecules.…”

Ultrasound-Assisted Extraction of Polyphenols from Maritime Pine Residues with Deep Eutectic Solvents

“…Six variables were selected to be optimized: solid-to-solvent ratio (0.50–2.50 g/10 mL of solvent), water percentage (0–60%), temperature of extraction (30–60 °C), time of extraction (1–2 h), amplitude (20–80%), and catalyst concentration (0–2 M H 2 SO 4 ). These variables and the studied range were based on the previous experience of the research group [ 17 , 27 , 32 , 33 ]. It is important to remark that although DESs mixtures usually present high boiling points due to their inherent physicochemical characteristics, many authors have proved the degradation of polyphenols at temperatures higher than 60 °C [ 34 ].…”