Wheat straw lignin extraction with bio-based solvents using enabling technologies

Abstract

Two bio-based solvents, natural deep eutectic solvents (NaDESs) and g-valerolactone (GVL), have been used under microwave (MW), and ultrasound (US) irradiation to design an efficient and sustainable process for wheat straw delignification and have been compared with the traditional alkali procedure. Best delignification (45%) was achieved with a three-component NaDES (lactic acid/glycerol/choline chloride) under MW irradiation (at 120 C in 30 min), with solid/liquid ratio of 1:50. A GVL/water mixture (8:2) also gave an efficient delignification (27%) under US irradiation (40 kHz, 200 W) at 50 C for 60 min. Analytical pyrolysis (Py) coupled with GC/MS/FID, provides valuable information on the extracts' chemical profile. DPPH and FolineCiocalteu tests highlighted the efficiency of MW-and US-assisted extraction as well as the extracts quality. The highest antioxidant activity for the NaDES extracts was obtained under US irradiation.

Green Deep Eutectic Solvents for Microwave-Assisted Biomass Delignification and Valorisation

“…Despite the biomass delignification is a time-consuming process [ 17 ], MW can dramatically reduce the operation time. For this reason, different extraction times were compared (30 and 120 min) [ 18 ].…”

“…Thirdly, lignin was precipitated from alkaline solutions by acidification. In detail concentrated H 2 SO 4 was added to reach pH 2, according a previously presented protocol [ 17 ].…”

“…Solvents derived from biomass (especially hemicellulose and lignin) including γ-valerolactone (GVL) [ 11 , 12 ], 2-methyltetrahydrofuran [ 13 ], tetrahydrofuran (THF) [ 14 ], ionic liquids (ILs) [ 15 ] and deep eutectic solvents (DESs) [ 16 , 17 ] have been successfully applied in biomass pretreatment and conversion.…”

“…Moreover, when combining NADESs with enabling technologies (i.e., ultrasound irradiation) [ 17 , 44 ] an efficient wheat straw (WS) delignification can be achieved. This effect is due to the reduction of solvent viscosity and the consequent improved mass transfer resulting by the generation of high-energy microenvironments.…”

Nano-Structured Lignin as Green Antioxidant and UV Shielding Ingredient for Sunscreen Applications

“…In this context, lignin, the most abundant polyphenol in nature, is increasingly becoming one of the main protagonists since it is recovered in large amounts as a low-cost waste from pulp and paper industry and biorefinery [ 48 ]. The low environmental impact of lignin extraction and purification technologies has been reported and discussed, focusing on the expected benefits of lignin as a high added value material [ 49 , 50 , 51 ]. Current and potential application of lignin has been reviewed [ 52 , 53 , 54 , 55 , 56 ], focusing on power fuel and syngas production (Fischer–Tropsch synthetic fuels), material science and fine-chemicals, specialties, and commodities preparation [ 57 , 58 ].…”