Polycarboxylate superplasticizer instead of ultrasonic treatment for dispersing cellulose nanofibers to strengthen cemented rockfill

Comparison of unique effects of two contrasting types of cellulose nanomaterials on setting time, rheology, and compressive strength of cement paste

Magnetorheological fluids (MRFs) are smart fluids made of magnetic particles in a viscous carrier fluid, and their rheological properties are controllable by an external magnetic field. However, MRFs suffer from serious sedimentation and redispersibility problems, which limit their effectiveness and feasibility in a wide variety of applications. Herein, we present a novel strategy to improve magnetorheological property and stability of MRFs using cellulose nanofibers (CNFs), rapidly prepared from energy cane bagasse using microwave-assisted alkali-H2O2 and ultrasonic treatment. High delignification rate of 94.3% was achieved by the microwave treatment for 15 min. Chemical structure analysis revealed that the removal of lignin and carboxylation of cellulose occurred simultaneously. The obtained CNFs exhibited a highly entangled network structure, and their suspension showed the gel-like viscoelastic behavior. In CNF-MRF, the magnetic particles were entrapped and suspended by the entangled network of CNFs, which is due to the physical entanglement and the electrostatic repulsion force between Fe3O4 and CNFs. CNFs helped suspend magnetic particles in CNF-MRFs, leading to improved stability and magnetorheological properties (i.e., viscosity stability after cycling, reversible rate of 95.57% after 100 cycles). This work demonstrates a new path for the production of CNFs from energy cane bagasse wastes and their value-added utilization in MRFs.

Cellulose nanofibers (CNFs) with an average diameter of 22 nm were prepared from sugar beet pulp (SBP) via an environmentally-friendly method. Steam-explosion pretreated SBP was treated with hydrogen peroxide (H2O2) bleaching, high-speed blending, and ultrasonic treatment. Thermogravimetric analysis showed that hemicellulose was partially hydrolyzed in the steam-cooking stage, pectin was removed in the explosion stage, and lignin was removed by H2O2 bleaching. The removal of non-cellulosic components was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. Morphological analysis showed that steam-explosion pretreatment largely extracted the binder materials of hemicellulose and pectin. This exposed the microfibrillated cellulosic fibers, which promoted subsequent nanofibrillation. X-ray diffraction showed that the CNFs had a crystallinity index of 62.3%. The CNFs had good thermal stability, and thus have potential for use as fillers in polymer matrices. The only chemical reagent used in this green method was H2O2. Combining H2O2 bleaching with steam explosion, high-speed blending, and ultrasonic treatment reduced the overall energy consumption and increased the efficiency of the CNFs extraction. The method, therefore, has potential application in industrial processes.

Alpha cellulose was extracted from Bambusa rigida fibers by carrying out Soxhlet extraction and bleaching and alkali treatments with acidified sodium chlorite solution and sodium hydrate solution. Then, cellulose nanofibers were isolated from α-cellulose with the combination of (33 wt%) sulfuric acid and ultrasonic treatment. The nano-sized fibers were successfully isolated, and the average diameters were about 10 to 30 nm. FTIR showed that a majority of the hemicelluloses and lignin were removed from the raw fiber and that the chemical constituents of α-cellulose and cellulose nanofibers were similar. XRD showed that the obtained nano-fibers presented a cellulose I structure, and thus the crystallinity of cellulose nanofibers was significantly increased. TGA showed that the thermal stability of the cellulose nanofibers was significantly improved. The relative crystallinity and thermal degradation temperature of the cellulose nanofibers reached 61.21% and 315.2 °C, respectively.

In this study, a green, highly efficient and low energy consumption preparation method of cellulose nanofiber (CNF) was developed by using agricultural and forestry waste durian rinds as raw materials. The power of ultrasonic treatment was successfully reduced to only 360 W with low molecular weight liquid DMSO. The obtained durian rind-based CNF had a diameter of 8–20 nm and a length of several micrometers. It had good dispersion and stability in water, and could spontaneously cross-link to form hydrogel at room temperature when the concentration was more than 0.5%. The microscopic morphology and compressive properties of CNF aerogels and composite cellulose aerogels prepared from durian rind-based CNF were evaluated. It was found that CNF could effectively prevent the volume shrinkage of aerogel, and the concentration of CNF had a significant effect on the microstructure and mechanical properties of aerogel. The CNF aerogel with 1% CNF exhibited a sheet structure braced by fibers, which had the strongest compression performance. The porosity of CNF aerogels was high to 99%. The compressive strength of the composite cellulose aerogel with durian rind-based CNF was effectively enhanced.

Cellulose nanofibers (CNFs) with an average diameter 8 nm were isolated from corncobs using a stepwise method that included steam-explosion pretreatment, alkaline treatment, sodium hypochlorite bleaching, high-speed blending, and ultrasonic treatment. This mechanochemical method used only two chemical reagents in low concentrations to remove non-cellulosic components. The removal of non-cellulosic components was confirmed by Fourier-transform infrared spectroscopy. X-ray diffraction revealed an increase in crystallinity during steam explosion and subsequent mechanochemical treatments. Pretreatment by steam explosion caused the partial hydrolysis of hemicellulose and loosened the structure of raw materials, which facilitated the subsequent chemical processes. The thermal stability and morphology of samples at different stages were also investigated. Steam explosion increased the thermal stability of hemicellulose and cellulose components, as it removed a fraction of hemicellulose. High-speed blending reduced the entanglement of cellulosic fibers and created uniform size. Ultrasonic treatment was used in the final step of nanoscale fibrillation. The method used in this study is environmentally friendly and has the potential to be applied at industrial scale.

Pretreatment approaches are highly desirable to improve the commercial viability of nanocellulose production. In this study, we propose a new approach to mass produce nanocellulose using a hydrated choline chloride/oxalic acid dihydrate deep eutectic solvent (DES) combined with an ultrasonic process. The hydrogen bond acidity, polarizability, and solvation effect reflected by the Kamlet–Taft solvatochromic parameters did not decrease even after the addition of large amounts of water. Instead, the water facilitated the ionization of H+ and delocalization of Cl– ions, forming new Cl–H2O ionic hydrogen and oxalate–H2O hydrogen bonds, which are critical for improving the solvent characteristics. One pass of kraft pulp through the hydrated DESs (80 °C, 1 h) was sufficient to dissociate the kraft pulp into cellulose nanofibers or cellulose nanocrystals using an 800 W ultrasonic treatment. The present study represents an alternative route for the kraft pulp pretreatment and the large-scale production of nanocellulose.

Cellulose nanofibers (CNF) have been extracted from agave cantala fibers by using chemical-ultrasonic treatment. The raw fibers have been subjected to alkali and bleaching treatments followed by acid-hydrolysis. The characteristics of cantala fibers such as their morphology through scaning electron microscope (SEM), Transmission electron micrsoscop (TEM), fourier transform analysis (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) have been analyzed. The CNF extracted from cantala fiber had uniform diameters of 45-50 nm with 800-2000 nm in lengths. Change in the FTIR spectra of CNF indicated that hemicellulose and lignin were significantly removed during chemical treatment. The crystallinity index of CNF increased when chemical treatment followed by optimum-time ultrasonic treatment was applied. The TGA discovered that CNF was stable until 271 oC. Based on the properties, the CNF would be suitable for reinforcement of nanocomposites.

In recent years, due to increased awareness and push toward more environmentally sustainable technology, nanocomposite materials obtained from natural and renewable resources have received significant interest. Nanofibrous composite thin film consisting of polyvinyl alcohol (PVA), chitosan, and cellulose nanofiber (CNF) from sugarcane bagasse were prepared by solution casting method and ultrasonic processing. The dispersion of nanofiller in a solution is obtained by energetic agitation using the method of sonication, which resulted in improved mechanical properties. The results showed that an appropriate sonication time (30 min) with 40 wt% of bagasse cellulose nanofibers improved the film performance significantly as compared to other weight percentages of nanocellulose. The performance of the films containing different weight percentages of bagasse nanocellulose was comprehensively investigated in terms of mechanical properties, thermal stability, biodegradability, and antimicrobial properties. The highest mechanical strength of 80.47 MPa is recorded with treated CNF as compared to 70.13 MPa for untreated CNF. Thermal degradation of antibacterial PVA/CNF film was evaluated by thermogravimetric (TG%) values. The weight loss occurred at three temperature ranges, that is, 80–130, 250–350, and 380–430°C. The three spectrums reveal loss in water content, thermal deprivation of polymer chain, and detachment of bonds into molecules. Moreover, the homogeneous dispersion resulted due to the sonication process which was studied using scanning electron micrographs. Furthermore, the developed film exhibited strong antibacterial properties against Staphylococcus aureus and Escherichia coli bacteria and can be used in various applications in the field of agriculture and food packaging.

Bio-based polymer composites find increasing research and industrial interest in different areas of our life. In this study, cellulose nanofibers (CNFs) isolated from sugar beet pulp and nanoemulsion prepared from sugar beet pectin and pomegranate extract (PGE) were used for making films and used as coating with antioxidant and antimicrobial activities for paper. For Pectin/PGE nanoemulsion preparation, different ratios of PGE were mixed with pectin using ultrasonic treatment; the antibacterial properties were evaluated to choose the formula with the adequate antibacterial activity. The antioxidant activity of the nanoemulsion with the highest antimicrobial activity was also evaluated. The nanoemulsion with the optimum antibacterial activity was mixed with different ratios of CNFs. Mechanical, greaseproof, antioxidant activity, and antibacterial properties of the CNFs/Pectin/PGE films were evaluated. Finally, the CNFs/Pectin/PGE formulation with the highest antibacterial activity was tested as a coating material for paper. Mechanical, greaseproof, and air porosity properties, as well as water vapor permeability and migration of the coated layer from paper sheets in different media were evaluated. The results showed promising applicability of the CNFs/Pectin/PGE as films and coating material with antibacterial and antioxidant activities, as well as good stability for packaging aqueous, fatty, and acidic food products.

Inspired by the principles of the circular economy, using vineyard pruning residues as a source of raw materials for producing nanocellulose is a promising approach to transforming vineyard resources into value-added products. This study aimed to obtain and characterize cellulose and cellulose nanofibers from such sources. The cellulose collected from different fractions of micronized stems (500, 300, 150 μm, and retain) of vines was submitted to autohydrolysis and finally bleached. Soon, it underwent treatment via (2,2,6,6-tetrametil-piperidi-1-nil)oxil (TEMPO) oxidation and ultrasonic to obtain nanocellulose fibers. The cellulose films were obtained at a microscale thickness of 0.05 ± 0.00; 0.37 ± 0.03; 0.06 ± 0.01 e 0.030 ± 0.01 mm, with the following particle size: 500 µm, 300 µm, 150 µm, and retain (<150 µm). The bleaching efficiency of the cellulose fibers of each particle size fraction was evaluated for color through a colorimeter. In addition, the extraction of cellulose fibers was assessed by infrared with Fourier transform, and size and shape were assessed by microscopy. Differential scanning calorimetry and X-ray diffraction were performed to confirm the thermal and crystalline properties. Combining autohydrolysis with a bleaching step proved to be a promising and ecological alternative to obtain white fractions rich in cellulose. It was possible to perform the extraction of cellulose to obtain nanocellulose fibers from vine pruning residues for the development of coatings for the conservation of heritage buildings from environmental conditions through an environmentally friendly process.

Triodia pungens is one of the 69 species of an Australian native arid grass spinifex which covers approximately 27 % (2.1 million km2) of the Australian landmass. The use of fibrous and resinous components of spinifex has been well documented in traditional indigenous Australian culture for thousands of years. In this thesis the utility of both the cellulosic and resinous components of this abundant biomass for modern applications, and a potential economy for our Aboriginal collaborators, were explored. One part of this study was focused on the optimisation of a resin extraction process using solvent, and the subsequent evaluation, via a field trial, of the potential use and efficacy of the resin as a termiticide. Termiticidal performance was evaluated by re-dissolving the extracted resin in acetone and coating on pine timber blocks. The resin-coated and control blocks (uncoated timber) were then exposed to a colony of Mastotermes darwiniensis termites, which are the most primitive active and destructive species in subterranean areas, at a trial site in northeast Australia, for six months. The results clearly showed that spinifex resin effectively protected the timber from termite attack, while the uncoated control samples were extensively damaged. By demonstrating an enhanced termite resistance, it is shown that plant resins that are produced by arid/semi-arid grasses could be potentially used as treatments to prevent termite attack.In the other part of this study it has been demonstrated that very small diameter and unprecedentedly high aspect ratio cellulose nanofibrils (NFC) can be readily isolated from spinifex biomass using unrivalled mild pulping coupled with minimal mechanical energy by any of three methods; high pressure homogenizer, ultrasonication, and milling. After washing, delignification and bleaching steps, the mechanical defibrillation of fibres was optimized by varying the specific processing conditions of each of these three mechanical treatment methods. Cellulose nanofibres with an extremely low average diameter (below 10 nm) and high aspect ratio (~500) were produced, even after applying very low energy processing. Similarly, acid hydrolysis at lower temperatures and acid concentrations with respect to the published contemporary protocols yielded high aspect ratio cellulose nanocrystals (CNC), for which the average lengths were found to be unaffected by further ultrasonic treatments. We hypothesize that the chemical and morphological origins for this surprisingly low energy input requirement for isolating high aspect ratio nanofibers from Triodia pungens is directly related to the plant’s unique morphology and composition, which contains unusually high amounts of hemicellulose. It is also hypothesised that these unique traits are a result of this species’ evolution, which has been heavily influenced by an extreme semi-arid climate.Polyurethane and spinifex CNC nanocomposites were also prepared via twin-screw reactive extrusion and solvent casting. Twin-screw reactive extrusion offered better CNC dispersion and resulted in superior mechanical properties with respect to the solvent casting method.

Effect of the dispersion state of minerals on the properties of cellulose nanofiber-based composite films

Cellulose nanofibers isolated from renewable lignocellulosic biomass are considered highly promising fillers in preparing sustainable composite materials. Although previous technologies on the production of cellulose nanofibers were encouraging, drawbacks such as chemical reagent, high energy consumption, time-consumption, and equipment degradation have limited these techniques for practical applications. In this work, bamboo particles were subjected to microwave liquefaction process and the liquefied bamboo residues were characterized to have a better understanding of the liquefaction behaviors of bamboo. Then, the microwave liquefaction process was optimized for the production of cellulose raw materials and the isolation of cellulose nanofibers. The lignin fraction fractionated from the microwave liquefaction process was also characterized for use in bio-based materials. The overall results revealed that high conversion yield of bamboo to liquid could be archived in mild microwave liquefaction reaction conditions. Lignin and hemicellulose in bamboo could easily undergo decomposition during liquefaction, while cellulose was the main resistance to the liquefaction process. The chemical and morphology analysis results revealed that the liquefied bamboo residues retained fiber structure and cellulose. Bleaching and acid hydrolysis were proved to be effective in purifying the residues for pure white cellulose fibers by removing carboxyl groups and lignin fragments. Long nanofibrils were generated by subjecting the pure cellulose fibers to high-intensity ultrasonic treatment. Good quality fibers with high holocellulose content were successfully produced by removing lignin and extractives from bamboo when the microwave liquefaction temperature was below 120oC. The relative lignin and extractives contents of the liquefied residues from the reaction at 120 oC, 9min were as low as 0.65 and 0.49 %, respectively. Cellulose nanofibers with diameters in the range of 2-30 nm were successfully extracted from the cellulose materials with a subsequent chemical treatment as a purification process and ultrasonication as a nanofibrillation process. The main functionality of the microwave liquefaction process on the nanofiber preparation process was efficiently converting bamboo bundles into micro-sized fibers by almost completely removing lignins and extractives. The isolated cellulose nanofibers have potential application for the fabrication of thermally stable composites because of their high thermal stability. Lignins recovered from the microwave liquefaction system showed high purity and retained their natural structures. The lignin samples were completely soluble in ethanol/water, DMSO, THF, 1, 4-dioxane, and 1mol/L NaOH solution. Polylactic acid (PLA)-lignin composites were successfully fabricated, and the lignin component in the PLA-lignin blends significantly improved the UV light barrier properties of the composites. The utilization

Well-designed structure of sandwich-like composite films based on hollow polyaniline and MXene with enhanced electromagnetic wave absorption