Extraction of Cellulose Nanofibers via Eco-friendly Supercritical Carbon Dioxide Treatment Followed by Mild Acid Hydrolysis and the Fabrication of Cellulose Nanopapers

Abstract

The conventional isolation of cellulose nanofibers (CNFs) process involves high energy input which leads to compromising the pulp fiber’s physical and chemical properties, in addition to the issue of elemental chlorine-based bleaching, which is associated with serious environmental issues. This study investigates the characteristic functional properties of CNFs extracted via total chlorine-free (TCF) bleached kenaf fiber followed by an eco-friendly supercritical carbon dioxide (SC-CO2) treatment process. The Fourier transmission infra-red FTIR spectra result gave remarkable effective delignification of the kenaf fiber as the treatment progressed. TEM images showed that the extracted CNFs have a diameter in the range of 10–15 nm and length of up to several micrometers, and thereby proved that the supercritical carbon dioxide pretreatment followed by mild acid hydrolysis is an efficient technique to extract CNFs from the plant biomass. XRD analysis revealed that crystallinity of the fiber was enhanced after each treatment and the obtained crystallinity index of the raw fiber, alkali treated fiber, bleached fiber, and cellulose nanofiber were 33.2%, 54.6%, 88.4%, and 92.8% respectively. SEM images showed that amorphous portions like hemicellulose and lignin were removed completely after the alkali and bleaching treatment, respectively. Moreover, we fabricated a series of cellulose nanopapers using the extracted CNFs suspension via a simple vacuum filtration technique. The fabricated cellulose nanopaper exhibited a good tensile strength of 75.7 MPa at 2.45% strain.

Isolation and characterization of micro cellulose obtained from waste mango

“…These results are consistent with the ones presented in this study. This is consistent with the report of Atiqah et al [44] that amorphous portions like hemicellulose and lignin were removed after applying alkali and bleaching treatment on raw kenaf fibre. Figure 3 shows the native and micro cellulose fibre spectra obtained by chemical treatment.…”

Functional Properties and Molecular Degradation of Schizostachyum Brachycladum Bamboo Cellulose Nanofibre in PLA-Chitosan Bionanocomposites

“…These functional group bonds represent cellulose nanofibre, as reported in previous studies [ 28 , 34 ]. The functional group analysis confirmed the successful isolation of CNF using combined supercritical carbon dioxide and high-pressure homogenisation [ 33 ].…”

“…These confirmed that the CNF isolated could not be reversed back to its raw material or change its properties. Even at high voltage [ 33 ]. This means that the isolation process produced a stable cellulose nanofibre.…”

“…The isolation of cellulose from Schizostachyum brachycladum bamboo was done using a modified method of Atiqah et al, [ 33 ]. Raw Schizostachyum brachycladum bamboo culm was cut into small sizes (5–10 mm) and was digested with sodium hydroxide (NaOH) in a high-pressure digester for 4 h. The digested fibres were washed with water to remove excess NaOH and bleached with hydrogen peroxide (H 2 O 2 ) and ozone (O 3 ).…”

Improved Hydrophobicity of Macroalgae Biopolymer Film Incorporated with Kenaf Derived CNF Using Silane Coupling Agent

“…However, the modified biofilms in Figure 2g-f exhibited dense structure with tightly packed stratified cross-sections as the fibre loading increased compared with unmodified biofilms. As the percent loading increased, the biofilm's porosity decreased, suggesting the significance of homogenous and well dispersed CNFs in the macroalgae matrix, which was fused due to the interaction and intermolecular hydrogen bonding [27]. The reduction of the biopolymer film's porous surface could be attributed to the increase in CNFs in the macroalgae matrix, indicating an increase in mechanical strength.…”