Isolation of High-Purity Cellulose Nanofibers from Wheat Straw through the Combined Environmentally Friendly Methods of Steam Explosion, Microwave-Assisted Hydrolysis, and Microfluidization

Abstract

High-purity cellulose nanofibers were isolated from wheat straw through an environmentally friendly, multistep treatment process that combined steam explosion, microwave-assisted hydrolysis, and microfluidization. The cellulose content of the processed nanofibers increased from 44.81% to 94.23%, whereas the hemicellulose and lignin contents significantly decreased. Scanning electron microscopy revealed the effects of the isolation treatments on fiber morphology and width. Atomic force microscopy was used to observe the changes in the components, surface roughness, and crystallinity of the fibers. Transmission electron microscopy showed long, loose nanofiber bundles that were 10–40 nm wide with an average individual diameter of 5.42 nm. Fourier transform infrared spectroscopy showed that noncellulosic components were effectively removed. X-ray diffraction analysis revealed the improved crystallinity of the processed fibers, as well as the partial crystalline transformation of cellulose I to cellulose II. Thermogravimetric analysis and derivative thermogravimetric results showed the enhanced thermal properties of the nanofibers. The removal of hemicellulose and lignin increased the crystallinity of the fibers, thus enhancing the thermal properties of the processed fibers. Results indicated that the efficient, environmentally friendly, multistep treatment process yields nanofibers with potential advanced applications.

Alkaline Fractionation and Subsequent Production of Nano-Structured Silica and Cellulose Nano-Fibrils for the Comprehensive Utilization of Rice Husk

“…On the other hand, the crystallinity of the CNF obtained after proceeding to the second-stage bleaching was measured to be 57.1%, which was slightly lowered. This result is in good agreement with the results of Liu et al, which suggested that the crystallinity of CNF increased as the proportion of cellulose increases due to the removal of amorphous components such as lignin or hemicellulose during chemical bleaching step [52]. Figure 6b shows the FT-IR spectra of raw RH and RH fibers obtained by chemical bleaching for each stage.…”

From unavoidable food waste to advanced biomaterials: microfibrilated lignocellulose production by microwave-assisted hydrothermal treatment of cassava peel and almond hull

“…This connects well with the ATR-IR absorbance (* 1700 cm -1 ) band observed the in darker samples, which may be attributed to condensed tannins and humins and/or migration of lignin from the cell walls to the exterior surface. Thus, the absorbance band at approximately 1700 cm -1 may correspond to carbonyl stretching vibrations associated with ferulic and para-coumaric acid (Zhao et al 2011;Chandra et al 2016;Liu et al 2017). A similar effect of microwave processing temperature with respect to changes in functional groups for AH, either untreated (AH) or pretreated (AHET, AHHP), was noted.…”

Interest of Pickering Emulsions for Sustainable Micro/Nanocellulose in Food and Cosmetic Applications

“…Microwaves have also been often combined with other treatments to produce nanocellulose. For instance, CNFs were extracted by steam explosion, microwave-assisted alkali treatment, and microfluidization, from wheat straw [ 72 ], or by microwave, high-shear homogenization and HPH, to valorize lime ( Citrus aurantifolia ) residues [ 73 ]. Likewise, sonication has also been associated with other processes.…”