Production of lignocellulose nanofibrils by conventional and microwave-assisted deep-eutectic-solvent pretreatments: mechanical, antioxidant, and UV-blocking properties

Abstract

Herein for the rst time, lignocellulose nano brils (LCNF) were prepared from pine-wood powder using microwave (MW)-assisted deep eutectic solvent (DES) pretreatment coupled with high-pressure homogenization. A DES based on choline chloride and lactic acid was employed, and LCNFs prepared by conventional DES pretreatment at 110°C (LCNF-110) and 130°C (LCNF-130) were used for comparison.Although MW treatment offered a high removal of lignin (70%) and hemicellulose (90%) within a short time (110 s), the morphological observations by scanning and transmission electron microscopies revealed excellent de brillation of the conventionally heat-treated samples. Likewise, LCNF-110 and LCNF-130 exhibited high tensile strengths of 154.6 ± 5.0 and 136.8 ± 1.2 MPa, respectively, whereas that of LCNF-MW was only 75.6 ± 1.4 MPa. Interestingly, LCNF-MW with a lignin content between that of LCNF-110 and LCNF-130 exhibited high thermal stability (T max 309.6°C) and potent antioxidant properties.However, the lignin contents of the LCNFs determined their UV-radiation blocking e ciency, where LCNF-110 > LCNF-MW > LCNF-130. Furthermore, all LCNF lms exhibited good visible-light transparency, exibility, and water contact angles (> 87°), indicating their promising potential for packaging applications.

Lignin-containing biodegradable UV-blocking films: a review

“…7b). 68 From these examples, it can be concluded that when the particle size of lignin is reduced, especially to the nanoscale, it can exhibit better compatibility with the matrix of the membrane material. This can result in uniform dispersion, ultimately leading to a lightening of the membrane's color.…”

“…One is directly made of the LCNF (lignocellulosic nanofibril) containing lignin and cellulose naturally, and the other is the composite material that combines the separated lignin and cellulose artificially. 68–72…”

“…Deep eutectic solvents (DES) are widely used in the production of LCNF, and the LCNF prepared in this way performed extraordinarily well in the subsequent fabricated membrane material properties. 68 In addition, a novel method for dissolving lignocellulose at room temperature has been proposed, involving a combination of DES pretreatment and subsequent dissolution in an AlCl 3 /ZnCl 2 aqueous system. The resulting regenerated lignocellulose film exhibited exceptional UV-blocking, hydrophobic, mechanical strength, and natural degradation properties.…”

High-Lignin-Containing Cellulose Nanofibrils from Date Palm Waste Produced by Hydrothermal Treatment in the Presence of Maleic Acid

“…Over the past decade, lignin-containing cellulose nanofibrils (LCNFs) have garnered significant interest as a new class of nanosized lignocellulosic material that could expand the domains of application of nanocelluloses. The presence of lignin in LCNFs likely imparts specific properties, including ultraviolet (UV)-absorption, antioxidant activity, hydrophobicity, barrier properties, and emulsification improvement in Pickering emulsions, among others. , Numerous studies have demonstrated the beneficial effects of the presence of residual lignin on the reduction of hydrophilicity, water uptake, and water permeability of nanopapers, particularly when the lignin content exceeded 15 wt %. , For example, thin films of high-lignin content CNFs (23 wt %) were reported to be suitable for producing low oxygen permeability films with an oxygen transmission rate (OTR) comparable to commercially available polymers like poly­(ethylene terephthalate) (PET) . Other applications encompass the use of LCNFs as an emulsifying agent for oil-in-water (O/W) Pickering emulsions, being an attractive alternative to synthetic surfactants .…”

“…The presence of lignin in LCNFs likely imparts specific properties, including ultraviolet (UV)-absorption, antioxidant activity, hydrophobicity, barrier properties, and emulsification improvement in Pickering emulsions, among others. 1 , 2 Numerous studies have demonstrated the beneficial effects of the presence of residual lignin on the reduction of hydrophilicity, water uptake, and water permeability of nanopapers, particularly when the lignin content exceeded 15 wt %. 3 , 4 For example, thin films of high-lignin content CNFs (23 wt %) were reported to be suitable for producing low oxygen permeability films with an oxygen transmission rate (OTR) comparable to commercially available polymers like poly(ethylene terephthalate) (PET).…”