Modified Fenton Oxidation of Cellulose Fibers for Cellulose Nanofibrils Preparation

Abstract

A novel catalytic oxidation process based on the Fenton reaction (H2O2–FeSO4) was developed to pretreat cellulose fibers for the preparation of cellulose nanofibrils (CNF). In the so-called modified Fenton process, softwood bleached kraft pulp (SWBK) fibers were utilized as individual microreactors to carry out efficient in situ oxidation of cellulose chains, which in turn facilitated nanofibrillation of fibers in subsequent mechanical treatment. Ferrous ions were preloaded into the fiber cell wall by adsorption and diffusion, which initiated the catalytic oxidation of cellulose simultaneously inside the fiber cell wall structure when hydrogen peroxide was introduced. The C2, C3, and C6-hydroxyl groups on the glucosyl of cellulose chains were oxidized to carboxyl groups, which could enhance the separation of micro/nanofibrils by increasing the electrostatic repulsion of the fibrils. The carboxyl group content was found to increase from 39 to 56 mmol/kg after the oxidation pretreatment. The oxidation also caused breakage of the 1,4-β-d-glucoside bonds of cellulose chains and dramatically decreased the degree of polymerization (DP) of the cellulose macromolecules. The oxidized SWBK fibers were well dispersed into cellulose nanofibrils in the subsequent homogenization treatment. The obtained CNF had a uniform distribution of cellulose fibrils with an average diameter of less than 100 nm.

Effect of Pretreatments on the Enzymatic Hydrolysis of High-Yield Bamboo Chemo-Mechanical Pulp by Changing the Surface Lignin Content

“…There were obvious flocculent fine fibers on the surface of the SCMP fibers, indicating that the damage degree of SCMP was higher than that of APMP and CTMP. After Fenton pretreatment, the cracks and the fine fibers of APMP, SCMP, and CTMP increased, compared to the hydrogen peroxide and ethanol pretreatment due to the dehydration and cleavage of cellulose glycosidic bonds after the Fenton oxidation reaction [ 25 ].…”

On the development of chrome-free tanning agents: an advanced Trojan horse strategy using ‘Al–Zr-oligosaccharides’ produced by the depolymerization and oxidation of biomass

“…Finally, once hemicellulose has been degraded into oligosaccharides, these species are further oxidized by H2O2. The C-C bond between C2 and C3 could be cleaved, generating two -COOH groups via this oxidation process 22,23 .…”

A More Efficient Fenton Oxidation Method with High Shear Mixing for the Preparation of Cellulose Nanofibers

“…Similar result had been reported in a previous study. [14] Figure 6a-c shows the SEM photographs of untreated, high shear mixed and Fenton oxidized cellulose samples respectively. As can be seen from the images, the untreated kraft pulp had a smooth surface and a dense structure (Figure 6a).…”

“…[11] Thus, many studies are focusing on developing pretreatment technology to decrease the energy demand, including enzymatic pretreatment, TEMPO-mediated oxidation, periodate oxidation, carboxy-methylation, Fenton oxidation, and so on. [3,[12][13][14][15] DOI: 10.1002/star.201900259…”

“…Therefore, a modified Fenton oxidation method was proposed. [ 14 ] The ferrous ions were preloaded into the fibers to form “ferrous‐fiber” complex catalyst system, which would induce the generation of hydroxyl radicals in situ in the fiber by introducing hydrogen peroxide to this system and prevent unnecessary HO • consumption in the bulk solution. The modified Fenton method could improve the oxidation efficiency and reduce the dosage of hydrogen peroxide significantly.…”