Sustainable Synthesis of Cellulose Nanofibers from Industrial Agar Seaweed Waste Biomass Using Hydrated Deep Eutectic Solvents

This work evaluated the profiles of Industrial agar seaweed waste biomass (ISWB) and pretreated ISWB by using deep eutectic solvent (DESs) and NaOH. The profiles of nanocellulose obtained from pretreated ISWB (with various types of hydrogen bond donors of choline chloride (ChCl)-based hydrated DES) were also evaluated.

ISWB underwent pre-treatment with either 100% wt. DES (1:1 molar ratio of ethylene glycol: citric acid) or 10% wt. NaOH at 80 °C to 90 °C. Subsequent treatment involved 10% wt. DES or ChCl-based hydrated DES with various HBDs (oxalic acid, citric acid, and urea) in a 1:2 molar ratio to produce nanocellulose.

Cellulose nanofibers isolated by the CE-DES approach exhibited a substantially higher yield compared with those obtained via the CE-NaOH method. CE-DES method induced swelling of ISWB and facilitate production of cellulose nanofibers. SEM images of samples indicates the presence of fibrous nanostructures across the majority of the specimens. Fourier-transform infrared (FTIR) spectroscopy demonstrated uniformity among all samples; they exhibited a consistent fingerprint pattern. X-ray diffraction (XRD) spectra indicated the presence of cellulose Type I in cellulose nanofibers produced by CE–DES, but not definitively in nanocellulose produced by the CE–NaOH method.

Cellulose nanofibers can be isolated from ISWB by using various DES and exhibits substantial characteristics of cellulose nanofibers from different ISWB pretreatment protocols.