Production Of Cellulose Nanofibers Research Articles

Production of cellulose nano/microfibers through simultaneous milling and enzymatic hydrolysis with an optimized cocktail of cellulase/xylanase/LPMO

Cellulose nanofibers (CNF) and microfibrillated cellulose (MFC) are biodegradable micro and nanomaterials derived from plant cellulose. The properties of CNF, influenced by fibril length, impact the strength of cellulose-based nanomaterials. This study uses enzymatic milling to explore pretreatments, enzymatic optimization, and CNF/MFC production. The study found that hammer milling and lamination are effective pretreatments for preserving fibers. The optimal enzymatic mixture contained 75 % cellulase and 25 % xylanase, yielding 68.7 % and 2.86 %/h productivity, respectively. The addition of the LPMO enzyme increased the yield by 10–13 %, depending on its concentration. Enzymatic milling was introduced as an innovative approach to CNF production, reducing hydrolysis time and creating milder processing conditions. The combined process of ball milling and enzymatic hydrolysis on pre-ground pulp in the hammer mill achieved a maximum CNF yield of 45.83 % and productivity of 13.10 %/h. X-ray diffraction showed that the lamination-pre-treated pulp had a high crystallinity index of 84.34 %. Scanning electron microscopy revealed fibers with diameters ranging from 52 nm to 296 nm. These findings support the search for sustainable and eco-friendly alternatives to non-renewable resources, enabling sustainable CNF production at room temperature with reduced processing time.

Engineered Living Structures with Shape-Morphing Capability Enabled by 4D Printing with Functional Bacteria.

Engineered living structures with the incorporation of functional bacteria have been explored extensively in recent years and have shown promising potential applications in biosensing, environmental remediation, and biomedicine. However, it is still rare and challenging to achieve multifunctional capabilities such as material production, shape transformation, and sensing in a single-engineered living structure. In this study, we demonstrate bifunctional living structures by synergistically integrating cellulose-generating bacteria with pH-responsive hydrogels, and the entire structures can be precisely fabricated by three-dimensional (3D) printing. Such 3D-printed bifunctional living structures produce cellulose nanofibers in ambient conditions and have reversible and controlled shape-morphing properties (usually referred to as four-dimensional printing). Those functionalities make them biomimetic versions of silkworms in the sense that both can generate nanofibers and have body motion. We systematically investigate the processing-structure-property relationship of the bifunctional living structures. The on-demand separation of 3D cellulose structures from the hydrogel template and the living nature of the bacteria after processing and shape transformation are also demonstrated.

Modulating digestibility and stability of Pickering emulsions based on cellulose nanofibers

Cellulose nanofibers (CNF) have been widely studied for their biodegradability and for their unique advantages as a stabilizer in Pickering-type emulsions. However, it is challenging to produce cellulose nanofibers from agroindustry waste with good techno-functional properties, without the use of harsh process conditions. Green alternatives (eco-friendly) have been studied to obtain nanofibers, such as enzymatic hydrolysis and/or application of mechanical processes. In this work, we used acid hydrolysis (as a control and example of an efficient method), enzymatic hydrolysis and a mechanical process (ultrasound) to obtain cellulose nanofibers. We also evaluated the effect of the presence of ethyl groups in the cellulosic matrix (ethylcellulose) on the stabilizing mechanism of emulsions. All cellulose nanofibers were able to produce Pickering emulsions at concentrations of 0.01–0.05% (w/w), although showing differences in emulsion stability and digestibility. Morphology of the different cellulose nanofibers affected the viscosity of the aqueous suspensions used as continuous phase. Emulsions with nanofibers obtained from cassava peel (without the presence of ethyl groups) were stabilized only by the Pickering-type mechanism, while ethylcellulose nanofibers also showed surface activity that contributed to the stability of the emulsion. Furthermore, these latter emulsions showed greater release of free fatty acids in in vitro digestion compared to emulsions stabilized by cellulose nanofibers. Despite these differences, in vitro digestion showed the potential of applying cellulose-stabilized emulsions to control the rate of lipid digestion, due to the low amount of free fatty acids released (<20%).

Extraction of Cellulose Nanocrystals and Nanofibers from Rubber Leaves and Their Impacts on Natural Rubber Properties

This study aimed to chemically isolate two distinct types of nanocellulose derived from rubber leaves and investigate their use in natural rubber (NR). The cellulose nanocrystals (CNCs) were obtained through acid hydrolysis, while oxidation with 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) was used to produce cellulose nanofibers (CNFs). The CNCs exhibited rigid and rod-like structures due to the removal of amorphous regions through acid hydrolysis, whereas the CNFs retained flexible, fiber-like morphologies and high aspect ratios. Incorporating CNCs or CNFs into NR improved its tensile properties, with the rigid CNCs enhancing the mechanical properties more than the flexible CNFs. CNC addition resulted in a 40% increase in tensile strength and a 38% increase in Young's modulus of NR. However, elongation at break decreased with filler content. On the other hand, CNF addition improved the elongation at the break without compromising the tensile properties. NR with CNF addition exhibited a 25% increase in tensile strength, a 30% increase in Young's modulus, and a 20% increase in elongation at break. Additionally, the biodegradability of NR nanocomposite films containing CNCs or CNFs surpassed that of unfilled NR film. Notably, a 6-month soil burial test revealed weight losses of 35% and 40% for NR nanocomposite films with CNCs and CNFs respectively, compared to a weight loss of 25% for the unfilled NR film.

Enzyme-assisted production of cellulose nanofibers from bleached and bleached/sulfonated sugarcane bagasse: impact of sulfonation on nanocellulose properties and yields

Enzyme-assisted production of cellulose nanofibers from bleached and bleached/sulfonated sugarcane bagasse: impact of sulfonation on nanocellulose properties and yields

Assessment of cellulose nanofibers from bolaina blanca wood obtained at three shaft heights

This study evaluated cellulose nanofibers from bolaina blanca wood (Guazuma crinita) obtained at different heights of the longitudinal axis of the shaft of trees from a three-and-a-half-year-old plantation. The wood was subjected to pulping, bleaching and subsequent mechanical milling using a Changsha Samy XYQM-2L planetary ball mill to obtain cellulose nanofibers. The product was characterised using analytical techniques: scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy. Additionally, the degree of polymerisation was determined. The effect of longitudinal position on cellulose nanofibers characteristics was evaluated by comparing means using ANOVA and Kruskal–Wallis statistical tests. The yield of cellulose nanofibers production from the high, middle and basal sections was 32,1 %, 33,6 % and 31 %, respectively. The obtained cellulose nanofibers exhibited a significantly larger diameter for the high zone (84 nm) compared with the middle (75 nm) and basal (69 nm) zones; the length remained above the micrometre range. With respect to degree of polymerisation, a decrease was evidenced with respect to the increase in shaft height; the basal zone exhibited a degree of polymerisation of 300, a significantly higher value than the middle and high zones, which exhibited degree of polymerisation of 249 and 211, respectively. The product showed typical cellulose type I polymorphism and crystallinity indexes of 76 %, 93 % and 96 % for the high, middle and basal sections, respectively. Regarding the thermostability of cellulose nanofibers, the maximum degradation rate of cellulose nanofibers occurred between 335 °C and 341 °C, with cellulose nanofibers from the basal area being the most stable. The adsorption of the methylene blue dye on cellulose nanofibers was evaluated; an efficiency &gt; 60 % was found.

Enzymatic pretreatment for cellulose nanofiber production: Understanding morphological changes and predicting reducing sugar concentration

Enzymatic pretreatment plays a crucial role in producing cellulose nanofibers (CNFs) before fibrillation. While previous studies have explored how treatment severity affects CNF characteristics, there remains a lack of suitable parameters to monitor real-time enzymatic processes and fully comprehend the link between enzymatic action, fibrillation, and CNF properties. This study focuses on evaluating the impact of enzyme charge (using a monocomponent endoglucanase) and treatment time on cellulose fiber morphology and reducing sugar generation. For the first time, a random forest (RF) model is developed to predict reducing sugar concentration based on easily measurable process conditions (e.g., stirrer power consumption) and fiber/suspension characteristics like fines content and apparent viscosity. Polarized light optical microscopy was found to be a suitable technique to evaluate the morphological changes that fibers experience during enzymatic pretreatment. The research also revealed that endoglucanases initially induce surface fibrillation, releasing fine fibers into the suspension, followed by fiber swelling and shortening. Furthermore, the effect of enzymatic pretreatment on resulting CNF characteristics was studied at two fibrillation intensities, indicating that a high enzyme charge and short treatment times (e.g., 90 min) are sufficient to produce CNFs with a nanofibrillation yield of 19–23 % and a cationic demand ranging from 220 to 275 μeq/g. This work introduces a well-modeled enzymatic pretreatment process, unlocking its potential and reducing uncertainties for future upscaling endeavors.

Rice husk nanocellulose: Extraction by high-pressure homogenization, chemical treatments and characterization

Rice husk is a substantial agricultural by-product of rice milling and has potential as a rich source of cellulose. This cellulose can be synthesized into nanocellulose materials. In this study, rice husk nanocellulose materials were synthesized by high-pressure homogenization (HPH) or acid hydrolysis (AH) combined with HPH (AH+HPH) treatments with different HPH cycles (6, 9 and 12 cycles at 120 MPa). Various physicochemical techniques were employed to investigate the nanocelluloses. It was found that the number of HPH cycles directly affected the particle size, crystallinity index and thermal stability of nanocellulose samples. The mean diameter and length of the nanocellulose were 10.15–12.42 nm and 602.13–620.08 nm for HPH samples and 11.94–12.34 nm and 436.22–440.04 nm for AH+HPH treatment. The crystallinity index of the nanocellulose ranged from 62% to 72%. Morphological characterization of nanocellulose treated with HPH and AH+HPH revealed the successful production of cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs). EDX analysis confirmed that the nanocellulose comprised 40.06–42.34% carbon and 50.07–54.56% oxygen as the main mineral elements. Therefore, this research offers an alternative strategy to enhance the value of rice husks and facilitate the utilization in the food system for future research.

Facile production of cellulose nanofibers from raw elephant grass by an aluminum chloride-enhanced acidic deep eutectic solvent

To develop a greener and more efficient method for producing cellulose nanofibers (CNFs) from raw plants, an AlCl3-enhanced ternary deep eutectic solvent, DES2 (consisting of choline chloride, citric acid, and AlCl3·6H2O in a molar ratio of 1:0.4:0.08), was synthesized. Raw elephant grass (EG) was pretreated with DES2, followed by sodium chlorite (NaClO2) bleaching and ultrasonic disruption to extract high-performance CNFs. The DES2 and NaClO2 treatments effectively removed hemicellulose and lignin, achieving removal rates of 99.23 % and 99.62 %, respectively, while maintaining a cellulose content of 78.3 %. DES2 demonstrated easy recyclability and maintained excellent biomass pretreatment performance even after multiple cycles. Following a brief 30-min intermittent ultrasound treatment, the resulting CNFs demonstrated superior crystallinity, increased carboxyl content, and a narrower width distribution compared to CNFs obtained from AlCl3-free DES1. Optimized conditions at 110 °C yielded CNFs with 85.3 % crystallinity, 0.64 mmol/g carboxyl content, 5.15 nm width distribution, and excellent dispersion in water for at least six months. Additionally, CNFs enhanced the tensile strength of chia seed mucilage (CM) composite films, showing a significant improvement to 26.6 MPa, representing a 231.3 % increase over the control film. This study offers a promising approach for efficiently producing CNFs from raw plants.

Preparation, characterization, and performance evaluation of composite films of polyvinyl alcohol/ cellulose nanofiber extracted from Imperata cylindrica

In recent years, production of cellulose nanofiber (CNF) from waste materials has achieved great interest owing to their renewable nature, biodegradability, high mechanical properties, economic value, and low density. Because Polyvinyl alcohol (PVA) is a synthetic biopolymer with good water solubility and biocompatibility, the composite material formed of CNF and PVA, is a sustainable way of monetizing to address environmental and economic issues. In this work pure PVA, PVA/CNF0.5, PVA/CNF1.0, PVA/CNF1.5, and PVA/CNF2.0 nanocomposite films were produced using the solvent casting approach with the addition of 0, 0.5, 1.0, 1.5, and 2.0 wt% of CNF concentrations respectively. The strongest water absorption behaviour was found as 25.82% for pure PVA membrane, followed by PVA/CNF0.5 (20.71%), PVA/CNF1.0 (10.26%), PVA/CNF1.5 (9.63%), and PVA/CNF2.0 (4.35%). The water contact angle of 53.1°, 47.8°, 43.4°, 37.7°, and 32.3° was formed between water droplet and the solid-liquid interface of pure PVA, PVA/CNF0.5, PVA/CNF1.0, PVA/CNF1.5, PVA/CNF2.0 composite films respectively. The SEM image clearly shows that a network structure like a tree form at the PVA/CNF0.5 composite film, where the sizes and number of pores are apparent. XRD analysis suggested that unique peaks found at 2θ = 17.5°, 28.1°, 33.4°, and 38° for nanocomposites indicating new crystal plane generated upon cross-linking in presence of malic acid. The maximum loss rate temperature (Td,max) for PVA/CNF0.5, PVA/CNF1.0, PVA/CNF1.5 was determined by TG analysis to be around 273.4 °C. FTIR studies suggested that PVA/CNF0.5 composite film showed the highest peak at 1428 cm−1 as compared to other PVA/CNF composite films representing the presence of higher crystalline band in the composite film matrix. PVA/CNF0.5 composite film was found to have a surface porosity and mean pore size of 27.35% and 0.19 μm respectively, classifying it in the MF membrane category. The maximum tensile strength (TS) of 5.27 MPa was found for PVA/CNF0.5, followed by PVA/CNF1.0, PVA/CNF1.5, pure PVA, and PVA/CNF2.0. The maximum young's modulus (111 MPa) was found for PVA/CNF1.0, followed by PVA/CNF0.5, PVA/CNF2.0, PVA/CNF1.5, and pure PVA, which could be attributed to the cyclization of the molecular structures by cross-linking. PVA/CNF0.5 exhibits greater elongation at break (21.7) than the other polymers, indicating a material's ability to undergo significant deformation before failure. Performance evaluation of the PVA/CNF0.5 composite film showed that 46.3% and 92.8% yield were found in the retentate for 200 mg/L of BSA, and 5 × 107 CFU/mL respectively. However, more than 90% E. coli was retained by PVA/CNF0.5 composite film, therefore absolute rating of this membrane is 0.22 μm. The size of this composite film may be therefore considered in the range of MF.

Biphasic lignocellulose fractionation for staged production of cellulose nanofibers and reactive lignin nanospheres: A comparative study on their microstructures and effects as chitosan film reinforcing

The effective fractionation of lignocellulose and the enhancement of its components require formidable efforts. This study explored synergistic biorefinery routes for the holistic conversion of lignocellulose biomass to green nanomaterials through one-pot fractionation using recyclable p-toluenesulfonic acid (p-TsOH)/pentanol reagents. The potential of p-TsOH/pentanol pretreatment of aspen biomass under various temperatures (80–180 °C) for co-production of cellulose nanofibers (CNFs) and lignin nanospheres (LNSs) was investigated. The optimal pretreatment temperature, which minimizes cellulosic degradation and promotes the holistic conversion of biomass, was 120 °C. In addition to its highly digestible nature, the cellulose-rich residue produced high-quality CNFs with a diameter <100 nm, good crystallization, and thermostability, making it suitable for various applications. Lignin characterization, molecular dynamics simulation, and density functional theory analyses of the recovered lignin revealed well-protected β-O-4 bonds (47.3/100 Ar), uniform molecular weights (Mw, 2815 g/mol; Mn, 1704 g/mol; PDI, 1.65), < 1% sugar content, fewer condensed structures, and nanosize shapes (100–300 nm) due to the molecular interactions of p-TsOH and pentanol with lignin units. Moreover, 0.4% LNSs additions reduced the chitosan film thickness by 53% and enhanced its tensile strain and strength by 33 and 59%, respectively, as compared to the pure chitosan film. This study provides a sustainable platform for the co-production of biobased CNFs and LNSs using cutting-edge fractionation of LCB, which is a breakthrough toward industrial biorefineries.

Nanocellulose and its polymer composites: preparation, characterization, and applications

Natural and synthetic polymeric materials are in high demand that continues to increase year after year, making them essential part of human life. By employing cellulose and cellulose derivatives as fillers for either synthetic or natural polymers, the environmental impact of non-biodegradable materials can be reduced. Nanocellulose (NC) materials have recently gained a lot of interest as potential fillers for reinforcing polymeric materials. The article highlights the different sources of NC, including plant sources, marine algae, bacteria and sea animals. The use of dewaxing solvents, alkali, bleaching agents, enzymes, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), ammonium persulfate (APS), ionic liquids, deep eutectic solvents and steam explosion for pretreatment of lignocellulosic materials was explained. In addition, this review considers the extraction methods, including mechanical fibrillation for the production of cellulose nanofibers (CNF) and acid hydrolysis for the production of cellulose nanocrystals (CNC). Furthermore, the article discusses recent advances in the fabrication of NC polymer composites, such as the melt mixing process, solution casting, 3D printing, electrospinning and pickering emulsions methods. The different characterization techniques of NC polymer composites were discussed in this article. Many promising applications of NC polymer composites, such as sensors, electronics, fuel cells, construction, paper and board, biomedical, food packaging, water purification, aerogels, and hydrogels are considered. &lt;br&gt; The bibliography includes 299 references.

Production of salad dressings via the use of economically prepared cellulose nanofiber from lime residue as a functional ingredient.

Production of cellulose nanofiber (CNF) via the use of a more economical and less energy-intensive means is desirable. Once formed, it is necessary to determine whether or not the prepared CNF would be capable of forming a Pickering emulsion as in the case of traditionally prepared nanofiber. In the present study, oil-in-water emulsions, namely, salad dressings, with CNF as a functional ingredient, were prepared. Lime residue powder as the source of dietary fiber was subject to high-shear homogenization to form CNF suspension, which was then mixed with other ingredients. Different contents of fat (20%-40%), egg yolk (0%-4%), and lime residue powder (0%-4%) were tested. The formed CNF successfully acted as a Pickering emulsifier and allowed the production of salad dressings with desirable characteristics at 30%-40% fat, 2% egg yolk, and 2% lime residue powder. The dressings exhibited adequate physicochemical properties and remained stable throughout the storage period of 28 days. PRACTICAL APPLICATION: The presently proposed means would allow the industry to produce cellulose nanofiber (CNF) in a more economical and less energy-intensive manner. The so-produced CNF exhibits comparable properties as traditionally prepared nanofiber and can be used as a stabilizer in food emulsions.

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

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 Fe2+ 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 Fe2+ 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-O2H2 bonding interaction via reduction of the energy gap of the dz2 orbital of the Fe center and π2py/π2pz orbitals of the H2O2 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 H2O2 to generate the •OH radical, and the whole catalytic cycle is found to be spontaneous at room temperature.

Microalgae on distillery wastewater treatment for improved biodiesel production and cellulose nanofiber synthesis: A sustainable biorefinery approach

Sugarcane spent wash generates waste at a large scale that impacts the environment, hence the classic waste reuse technology needs to be implemented. An integrated approach of spent wash and microalgae cultivation to produce biodiesel has gained momentum in recent times. However, the microalgae technology lacks the functional utilization of de-oiled microalgae biomass (DOB). This study proposed the development of a microalgae-based advanced process for distillery spent wash treatment, biomass recovery for biodiesel and utilizing algal residue as a step towards waste management. A novel microalga Coelastrella sp KJ-04 grown in distillery spent wash represented with high biomass (4.61g/L) and lipid production (3.6 g/L). The significant reduction in Chemical Oxygen Demand (COD, 49.3%), Total Nitrogen (TN, 49.7%), Total Phosphorous (TP, 21.8%), Total Organic Carbon (TOC, 40.2%), Total Sulphur (S, 37.2%) and Potassium (K, 42.5%) were achieved in spent wash. The extracted lipids of Coelastrella sp KJ-04 were converted to Fatty acid methyl ester (FAME) and examined by Gas chromatography -mass spectrometry (GC-MS) to observe the suitability for biodiesel prospect. The de-oiled biomass (DOB) was utilized for the synthesis of Cellulose nanofibers (CNF), purified and estimated with a diameter ranging between 20 and 27 nm. The crystalline structure and functional group of CNF were analyzed by X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR). The unprecedented work demonstrated the microalgae biorefinery approach for spent wash remediation, biodiesel synthesis and simultaneous production of biodegradable CNF from algal residue to support waste-free technology. In future, CNF can be reinforced into material for concrete as it could be the smart alternative to replace synthetic cement plastics.

Kinetic study and real-time monitoring strategy for TEMPO-mediated oxidation of bleached eucalyptus fibers

The present work aims at glimpsing the rate-determinant process parameters of TEMPO-mediated oxidation of bleached kraft cellulose for developing kinetic models and real-time monitoring tools. This may contribute to the scaling up of this reaction, frequently used as precursor of the production of cellulose nanofibers. For this, the effect of temperature, TEMPO and NaBr contents, and surface area of the fibers was assessed by means of a total experimental batch of 18 combinations, monitoring the carboxyl content (CC) of the samples and the NaOH consumption during oxidation. The obtained data was used to calculate the kinetic constant as a function of the conditions, as well as correlating the CC with the NaOH consumption, obtaining a strong linear correlation between these parameters. It was found that similar correlations could be used regardless process conditions, except for the case of TEMPO, which was found to protect the fibers from depolymerization and, thus, having different behavior at increasing TEMPO contents. Overall, the obtained results in the present study reveal the suitability of upscaling TEMPO-mediated oxidation, as well as having a deeper understanding on how the key parameters involved in the reaction affect the reaction path and, thus, contributing to the industrial deployment of oxidized cellulose and nanofibers.

Nanocellulose from Spanish Harvesting Residues to Improve the Sustainability and Functionality of Linerboard Recycling Processes.

The hornification processes undergone by the fibers in the paper industry recycling processes lead to the loss of properties of the final products, which exhibit poor mechanical properties. Among the most promising solutions is the reinforcement of secondary fibers with cellulose nanofibers. The present work addresses two important issues: the efficient production of cellulose nanofibers from scarcely exploited agricultural wastes such as horticultural residues and vine shoots, and their application as a reinforcement agent in recycled linerboard recycling processes. The effect of the chemical composition and the pretreatment used on the nanofibrillation efficiency of the fibers was analyzed. Chemical pretreatment allowed a significantly higher nanofibrillated fraction (45-63%) than that produced by mechanical (18-38%), as well as higher specific surface areas (&gt;430 m2/g). The application of the nanofibers as a reinforcing agent in the recycled linerboard considerably improved the mechanical properties (improvements of 15% for breaking length, 220-240% for Young's modulus and 27% for tear index), counteracting the loss of mechanical properties suffered during recycling when using chemically pretreated cellulose nanofibers from horticultural residues and vine shoots. It was concluded that this technology surpasses the mechanical reinforcement produced by conventional mechanical refining used in the industry and extends the number of recycling cycles of the products due to the non-physical modification of the fibers.

Comparative study of the production of cellulose nanofibers from agro-industrial waste streams of Salicornia ramosissima by acid and enzymatic treatment

The study of the suitability of two isolation processes to produce cellulose nanofibers (CNFs) from Salicornia ramosissima waste, with potential applicability as a reinforcing agent of polymeric composites was carried out. To separate the cellulose fibrils from the cell wall and obtain CNFs an alkaline treatment was applied followed by a bleaching treatment and, the insoluble residue was next hydrolyzed by either an acid treatment (AT) or an enzyme treatment (ET). SEM and TEM images indicated fiber exposure caused by both treatments. The diameter, length, aspect ratio, and polydispersity index, were measured for both CNFs. CNF (ET) showed high zeta potential values suggesting that ET produces more electrically stable and thinner nanofibers. The FTIR spectra revealed that both treatments effectively removed the amorphous components allowing the CNFs isolation, and XRD patterns evidenced the increase in the degree of crystallinity of both CNFs. Nonetheless, CNF(AT) presented a lower mechanical resistance due to its smaller particle size, compared to the CNF(ET). In summary, the (ET) could successfully isolate CNFs from the Salicornia waste, encouraging the use of this treatment, once when compared to (AT), it does not generate toxic residues, presents mild thermal conditions, and produces CNFs with higher-value applications.

High temperatures and pressures during cooking hinder the nanofibrillation of purified pulp

Kraft pulp is an abundant raw material for producing cellulose nanofibers. However, our previous study demonstrated that kraft cooking hinders the nanofibrillation of never-dried pulp. Therefore, this study aims to elucidate the specific factors of kraft cooking hindering nanofibrillation, particularly the effects of high temperature and pressure. Undried purified pulp, produced using the Wise method, was subjected to high temperature and pressure conditions, with and without subsequent alkali treatment. After fibrillating the pulps for different durations, the degree of nanofibrillation was evaluated by sedimentation tests. Undried Wise-based pulp, with excellent nanofibrillation ability, becomes less capable of nanofibrillation after cooking at high temperature and pressure. Thus, even in the undried state, harsh cooking is considered to have caused irreversible aggregation of microfibrils or hornification in the pulp cell wall. Moreover, high temperatures and pressure should be avoided when removing the matrix, e.g., lignin and hemicellulose, for producing pulp for cellulose nanofibers.

Isolation and Characterization of Cellulose Nanofibers from Wheat Straw and Their Application for the Supercapacitor

As a by-product of wheat planting, wheat straw is an abundant agricultural residue with the highest cellulose content of all agricultural fibers. Its resourceful utilization contributes to alleviating the environmental problems it caused. In this study, cellulose from wheat straw (WS) is used as a dispersing agent to prepare a novel multi-walled carbon nanotube-modified nickel foam (NF) electrode. The new electrode is investigated for electrochemical properties relevant to supercapacitors. The 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation is chosen to produce cellulose nanofibers (CNF) from wheat straw. The prepared CNF is used to facilitate the uniform dispersion of multi-walled carbon nanotubes (MWCNT) and favor the formation of a stable CNF-CNTs membrane on the nickel foam skeleton. The influence of dispersing materials and content of CNF on the electrochemical performance of electrodes is investigated. It is revealed that the incorporation of CNF can improve the electrochemical stability of electrodes. Moreover, it also exhibits optimum capabilities (70.2% capacitance retention from 1 to 40 mA cm−2) when CNF:MWCNT = 1:0.7. The areal capacity of the CNF-MWCNT/NF electrode for a scanning rate of 5 mV s−1 is twice that of the MWCNT/NF electrode and 30 times that of the NF electrode, indicating it is a promising candidate to ensure the synchronization of a green environment and energy development.