Lignocellulose's Effectiveness in Green Solvents

 In a new research, scientists from China and Pakistan investigate the use of regenerated lignocellulosic nanofibrils for green solvents. The work revealed a novel two-step scalable process for the synthesis of emulsions from these materials, as well as an analysis of the effects of treatments. The findings were published in the journal Polymers.

Fibers of Sisal

Biomass has been thoroughly investigated as a raw resource for a variety of technologies in a variety of industries. Materials such as lignin, cellulose, and hemicellulose can be found in biomass sources such as sugarcane bagasse, rice husk, wheat straw, pineapple peel, and maize straw.

Sisal fibres have comparatively high cellulose and hemicellulose content and low lignin concentration when compared to other biomass sources studied in recent decades. In addition, this organic material is plentiful, accounting for 2% of all cultivated plant matter.

Sisal fibres are made from the Agave sisalana plant. This plant has a ten-year lifespan, during which it will have produced between 200 and 250 leaves, with each dried leaf containing 4 percent fibre by mass. Low density, mechanical strength, biocompatibility, and biodegradability are all desirable qualities.

Sisal fibres have been employed in the creation of textiles, composites, surgical sutures, cellulose nanowhiskers, and Pickering emulsions due to their characteristics and abundance.

Regenerated Lignocellulosic Nanofibrils and Nanocellulose

Nanocellulose has been studied for usage in a variety of applications in recent years. Bacterial nanocellulose, cellulose nanocrystals, and cellulose nanofibrils are the three forms of nanocellulose. However, severe extraction processes such as alkaline treatment and bleaching to recover nanocellulose from wood biomass are impeding industrial applications.

For the usage of nanocellulose materials, severe extraction procedures and reagents offer economic and environmental issues. Furthermore, the hydrophilicity of this material, which is related to the presence of numerous hydroxyl groups, limits its suitability for applications such as Pickering emulsion stabilisers and hydrophobic films.

Another concern is the strong intermolecular pressures in nanocellulose materials' polymer networks. Strong interactions between cellulose, lignin, and hemicellulose cause this. It's tough to dissolve in conventional solvents. To address this problem, scientists are working on developing regenerated lignocellulose nanofibrils.

The extraction of regenerated lignocellulose nanofibrils is relatively simple, and they are widely available. The residual lignin in these nanofibrils has been shown to improve qualities such as hydrophobicity, thermal stability, antioxidant capabilities, and mechanical stability, according to research.

Several methods for extracting lignocellulosic nanofibrils have been published thus far. Chemical processes like inorganic acid hydrolysis, pulping, and TEMP oxidation, as well as physical methods like grinding and ultrasonication, are among them. Methods that combine chemical and physical techniques have also been developed.

The use of recovered lignocellulose nanofibrils as stabilisers and other components in Pickering emulsions provides a path to green solvent production. When compared to other types of natural emulsifiers, studies have shown that these materials are more suitable for emulsification. However, research on utilising sisal fibres to make recovered lignocellulose nanofibrils is lacking.

The Research

A new two-step scalable procedure for recovering lignocellulose nanofibrils from sisal fibres was demonstrated in a research published in Polymers. The oil-in-water emulsion was made via fibre dissolution and ultrasonication. Small fibre fragments were chopped and soaked in water, then agitated and heated to dissolve the fibre fragments in phosphoric acid.

The authors tweaked the fibre, water, and phosphoric acid ratios as well as the dissolving conditions. The solution was then poured with water to regenerate the nanofibrils until a neutral pH was achieved. Once the nanofibrils had settled, the excess water was removed to form concentrated solutions. Centrifugation was used to create a highly concentrated solution.

The resultant concentrated solution was characterised using FTIR, XRD, TEM, and optical microscopy. Finally, the authors created a green Pickering emulsion with the nanofibrils they had recovered. The size of emulsion particles was measured using optical microscopy.

Findings of the Research

The dissolving of sisal fibres in phosphoric acid, a green solvent, was established in this work. It's a safe, cost-effective, environmentally friendly, and non-volatile method. The dissolution is a fast and effective procedure that is non-derivative and can generate great results, according to the authors.

Pickering emulsion stabilisers made from recovered lignocellulosic nanofibrils are extremely suited and generate stable emulsifiers with mild settlement rates. Due to the formation of viscous aqueous solutions and suspensions, emulsions made with these nanofibrils have the advantages of limited oil droplet mobility and stability.

Pickering emulsions prepared this way can be used in technical emulsions and applications like tack coating and fog sealing. Food, medical science, and cosmetics are only a few of the potential industrial applications for these emulsions in the future. In conclusion, employing recovered lignocellulose nanofibrils from sisal fibres, an abundant and renewable natural resource, this study has proven a novel and powerful emulsion synthesis technique.

Written by:

HASHIR BIN SHAHID