Preparation of Cellulose Nanofibers from Corn Stalks by Fenton Reaction: A New Insight into the Mechanism by an Experimental and Theoretical Study

Abstract

Agricultural biomass wastes are an abundant feedstock for biorefineries. However, most of these wastes are not treated in the right way. Here, corn stalks (CSs) were assigned as the raw material to produce cellulose nanofibers (CNFs) via in situ Fenton oxidation treatment. In order to probe the formation mechanism of an in situ Fenton reactor, the bonding interaction of hydrated Fe 2+ ions and fiber has been systemically studied based on adsorption experiments, IR spectroscopy, density functional theory (DFT) calculations, and Raman spectroscopy. The results indicate that the coordination of the hydrated Fe 2+ ion to the fiber generates a quasi-octahedral-coordinated sphere around the Fe center. The Jahn−Teller distortion effect of the Fe center promotes the Fe−O 2 H 2 bonding interaction via reduction of the energy gap of the d z 2 orbital of the Fe center and π 2py /π 2pz orbitals of the H 2 O 2 molecule. The oxidation treatment of the pretreated CS by the in situ Fenton process shows the formation of a new carboxyl group on the fiber surface. The scanning electron microscopy image shows that the Fenton-treated fiber was scattered into the nanosized CNFs with a diameter of up to 50 nm. Both experimental and theoretical studies show that the pseudo-first-order kinetic reaction could describe the in situ Fenton kinetics well. Moreover, the proposed catalytic cycle shows that the large thermodynamic barrier is the cleavage of the O−O bond of H 2 O 2 to generate the • OH radical, and the whole catalytic cycle is found to be spontaneous at room temperature.

Regulation of Tetramethylpyrazine Formation by the Phenolics-Fenton Coupled Redox Cycling System

“…As shown in Figure 1C, the concentrations of FeSO 4 and H 2 O 2 greatly influence the effect. Since there are many factors affecting the Fenton reaction, 23 Fe 2+ can excite the hydroxyl radical ( • OH), and increasing the dosage of Fe 2+ can increase the number of • OH in the reaction system. At the same time, H 2 O 2 contributes to the generation of • OH and the reduction of Fe 3+ ; when the concentration of FeSO 4 increases, the proportion of H 2 O 2 is also increased.…”

Modified corn stalk carboxymethyl cellulose, acrylic acid and SBA‐15 based composite hydrogel used for agricultural water retention

“…Corn stalks contains 30% to 40% of cellulose, hemicellulose and lignin-like natural long-chain polymeric substances. [3][4][5] Compared with carbon fiber, glass fiber, stalk has a wide range of sources, low price, renewable, low density, natural environmental protection and other advantages, can solve the high cost of composite materials, serious pollution and other problems, with people pay attention to environmental protection, the preparation of good performance of stalk functional materials has become a research hot spot. 6,7 Natural cellulose is the most widely distributed and abundant polysaccharide in nature, and the source is very rich.…”

“…Corn stalks are burned as agricultural waste, which not only pollutes the environment, but also causes waste of biological resources. Corn stalks contains 30% to 40% of cellulose, hemicellulose and lignin‐like natural long‐chain polymeric substances 3–5 . Compared with carbon fiber, glass fiber, stalk has a wide range of sources, low price, renewable, low density, natural environmental protection and other advantages, can solve the high cost of composite materials, serious pollution and other problems, with people pay attention to environmental protection, the preparation of good performance of stalk functional materials has become a research hot spot 6,7 …”