Issue 15, 2024

Subcritical water digestion of woody biomass: extraction of cellulose nanomaterials under acid-lean condition

Abstract

Subcritical water extraction (SWE) is an emerging green and efficient hydrothermal technology, that offers superior performance in active material extraction, scalability, and reduction of harsh process chemicals, in biomass conversion. Regarding biomaterials, traditional isolation methods for cellulose nanocrystals (CNCs) are reliant on harsh chemicals (i.e., strong acid), which are expensive with little to no recyclability. This paper explores SWE as a nanotechnology platform to produce CNCs under the principle of “less is more” — by using low content (1 wt%) of phosphoric acid under subcritical conditions. Acid-catalyzed digestion of woody biomass afforded CNCs desirable physico-chemical features that are dependent on the process parameters (temperature, pressure, and time). Process temperature had a major impact on the reduction of fiber sizes (macroscale to nanoscale), fiber degradation, and fiber coloration (white to black). Electron microscopy revealed rod-like structures, with varying particle size distribution (100–500 nm), dominated by process time. However, colloidal stability was low (versus acid-hydrolyzed CNCs) due to the low charges on the surface of CNCs. Interestingly, vibrational spectroscopy reveals the effect of process pressure on biomass conversion to CNCs (with cellulose I structure) evidenced by Raman spectroscopy and solid-state fluorometry. The produced (bio)nanomaterials possessed a degree of crystallinity (∼70%) comparable to those produced via acid hydrolysis, with higher thermal stability, enhancing their applicability over a wide range of heat-intensive processes required for nanocomposite applications in biomedical and automotive industries, among others.

Graphical abstract: Subcritical water digestion of woody biomass: extraction of cellulose nanomaterials under acid-lean condition

Supplementary files

Article information

Article type
Paper
Submitted
02 Feb 2024
Accepted
13 Jun 2024
First published
13 Jun 2024
This article is Open Access
Creative Commons BY-NC license

Nanoscale Adv., 2024,6, 3923-3933

Subcritical water digestion of woody biomass: extraction of cellulose nanomaterials under acid-lean condition

R. Osei-Bonsu, M. Hoque, P. S. McMichael and E. J. Foster, Nanoscale Adv., 2024, 6, 3923 DOI: 10.1039/D4NA00108G

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