Carboxylated Cellulose Nanocrystals Research Articles

Probing the stability and quality of the cellulose-based Pickering emulsion containing sesamolin-enriched sesame oil by chemometrics-assisted ATR-FTIR spectroscopy

This study presents the employment of Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection and principal component analysis (PCA) to analyze the stability of a Pickering emulsion stabilized by carboxylated-cellulose nanocrystal (cCNC) comprising sesame oil phases with or without sesamolin. FTIR measurements identified an intermolecular hydrogen bond between the ester group of the triglyceride and the carboxyl group of the cCNC to create the emulsion droplet. The spectral bands from the hydroxyl group vibration (3700–3050 cm−1), carbonyl (1744 cm−1), CO groups of the ester triglyceride and cCNC (1160–998 cm−1) markedly discriminated between stabilized and destabilized emulsions. The PCA of FTIR spectra detected the change of molecular interaction during storage according to creaming, aggregation, and coalescence and changes in physicochemical parameters such as droplet size, refractive index, and zeta potential. Hence, PCA enabled the observation of the destabilization of emulsion in real-time.

Synthesis of hydrogel of polyvinylimide modified carboxylated nanocellulose combined with acidified montmorillonite for pH-controlled release of thiamethoxam

Controlled release of pesticides in response to environmental stimuli using hydrogels as carriers is a feasible approach to improve the effective utilization rates of pesticides. In this regard, modified carboxylated cellulose nanocrystal (CCNC)--based hydrogels with appropriate biocompatibilities and high specific surface areas have broad prospects. Accordingly, in this study, a pH-responsive hydrogel loaded with the pesticide thiamethoxam (TXM) (PEI-CCNC@A-MMT/TXM) was constructed by synergistically introducing CCNC modified with polyethyleneimine (PEI) into cost-effective acidified montmorillonite (A-MMT) via electrostatic self-assembly followed by combination with sodium alginate (SA) by emulsion–gel method via ionic crosslinking. PEI-CCNC@A-MMT efficiently improved the mechanical properties of the SA hydrogel and ensured the stability and TXM loading efficiency of this hydrogel; however, the hydrogel stress increased from 9.48 to 41.44 kPa under 20 % compressive strain when the mass ratio of A-MMT to PEI-modified CCNC (PEI-CCNC) was increased from 0 to 0.8. PEI-CCNC@A-MMT/TXM exhibited significant controlled-release characteristics with the change in pH; specifically, with an increase in pH from 5.0 to 9.0, the cumulative release ratio of TXM increased from 53.62 to 94.86 wt % within 48 h of the addition of PEI-CCNC@A-MMT/TXM to the phosphate buffered saline solution. Fitting the six models to the release curves proved that swelling, dissolution, and diffusion acted together during TXM release, and release mechanisms for TXM under different pH conditions were proposed. The release behaviors of PEI-CCNC@A-MMT/TXM in soil indicated that this hydrogel effectively prolonged the release of TXM, and only 91.53 wt % TXM was released within 240 h after the hydrogel entered the soil. The bacterial activity revealed that the hydrogel did not destroy the microbial environment of the soil and demonstrated high biocompatibility. This study provides a promising strategy for regulating the pesticide release behavior, improving pesticide utilization, and reducing environmental pollution of pesticides via introducing low-cost A-MMT and green CCNC into the SA hydrogel and applying this hydrogel as a pesticide carrier.

Effect of carboxylated cellulose nanocrystals on konjac glucomannan/κ-carrageenan composite hydrogels

Konjac glucomannan/κ-carrageenan (KGM/KC) composite hydrogels often fail to meet industrial requirements due to their weak mechanical properties, while nanofillers are potential materials to address this challenge by taking advantage of their nano-size and filling effects. Herein, carboxylated cellulose nanocrystals (C–CNCs) were chosen as nanofillers to regulate the properties of KGM/KC composite hydrogels, with focus on the effect of C–CNCs concentration on the morphological and physicochemical properties. Meanwhile, an in-depth exploration of the possible mechanisms was also underlying. C–CNCs were well dispersed within the KGM/KC composite matrix, which positively enhanced the mechanical strength, as well as increased the apparent viscosity and modulus of the composite hydrogel greatly when the C–CNCs concentration was 10 % (w/w). This is mainly ascribed to the enhancement of hydrogen bond interaction among the KGM, KC, and C–CNCs, which were verified by Fourier transform infrared spectroscopy. Additionally, the results of low-field nuclear magnetic resonance confirmed the presence of C–CNCs in the hydrogel matrix reduced the water mobility of the hydrogel, which improved the freeze-thaw stability of the composite hydrogel. The fitting of the Power law model (R2 > 0.98) showed that the swelling mechanism of KGM/KC composite hydrogels belonged to Fickian diffusion, and the swelling behavior could be regulated by adjusting the C–CNCs concentration. However, the excessive C–CNCs might weakened the interaction of composite hydrogels, which partially explains the reversal of the reinforcement effects seen at the lower additions of C–CNCs inclusion. These results provide a basis for the development and design of KGM/KC-based products with desirable attributes.

Synthesis of carboxylated cellulose nanocrystal/ZnO nanohybrids using Oxytenanthera abyssinica cellulose and zinc nitrate hexahydrate for radical scavenging, photocatalytic, and antibacterial activities

The extremely low antioxidant, photocatalytic, and antibacterial properties of cellulose limit its application in the biomedical and environmental sectors. To improve these properties, nanohybrides were prepared by mixing carboxylated cellulose nanocrystals (CCNCs) and zinc nitrate hexahydrate. Data from FTIR, XRD, DLS, and SEM spectra showed that, ZnO nanoparticles, with a size ranging from 94 to 351 nm and the smallest nanoparticle size of 164.18 nm, were loaded onto CCNCs. CCNCs/ZnO1 nanohybrids demonstrated superior antibacterial, photocatalytic, and antioxidant performance. More considerable antibacterial activity was shown with a zone of inhibition ranging from 26.00 ± 1.00 to 40.33 ± 2.08 mm and from 31.66 ± 3.51 to 41.33 ± 1.15 mm against Gram-positive and Gram-negative bacteria, respectively. Regarding photodegradation properties, the maximum value (∼91.52 %) of photocatalytic methylene blue degradation was observed after 75 min exposure to a UV lamp. At a concentration of 125.00 μm/ml of the CCNC/ZnO1 nanohybrids sample, 53.15 ± 1.03 % DPPH scavenging activity was obtained with an IC50 value of 117.66 μm/ml. A facile, cost-effective, one-step synthesis technique was applied to fabricate CCNCs/ZnO nanohybrids at mild temperature using Oxytenanthera abyssinica carboxylated cellulose nanocrystals as biotemplate. The result showed that CCNCs/ZnO nanohybrids possess potential applications in developing advanced functional materials for dye removal and antibacterial and antioxidant applications.

Mechanical, morphological and comparative properties of microbeads assembled from carboxylated cellulose nanocrystals

Elastic modulus of cCNC nanorod microspheres tuned by aerosol phase citric acid CA ester crosslinking.

Fabrication of a tough, long-lasting adhesive hydrogel patch via the synergy of interfacial entanglement and adhesion group densification.

Adhesive hydrogels (AHs) are considered ideal materials for flexible sensors. However, the lack of effective energy dissipation networks and sparse surface polar groups in AHs lead to poor mechanical properties and interfacial adhesion, which limit their practical application. Herein, a tough, long-lasting adhesive and highly conductive nanocomposite hydrogel (PACPH) was fabricated via the synergy of interfacial entanglement and adhesion group densification. PACPH was obtained by the in situ polymerization of highly carboxylated cellulose nanocrystals (SCNCPA, surface pre-grafted polyacrylic acid chains, C-COOH = 11.5 mmol g-1) with the acrylic acid precursor. The unique tacticity of SCNCPA provides strong interface entanglement and multiple hydrogen bonds with the PACPH network, which further increases the energy dissipated during SCNCPA displacements, and enhances the mechanical properties of PACPH (tensile strength = 1.45 MPa, modulus = 332 kPa, and fracture toughness = 13.2 MJ m-3). Meanwhile, SCNCPA increases the density of surface polar groups in PAPCH and also acts as an anchor point to improve the adhesion strength (>2-3 times) of PACPH on various substrates. The combination of excellent mechanical, adhesive, and conductive properties of the PAPCH-integrated patches enables long-term monitoring of human daily activities and electrocardiogram (ECG) signals, verifying that PAPCH is a promising material platform for the further development of flexible sensors and other health management devices.

Improved pressure‐sensitive adhesive performance using carboxylated cellulose nanocrystals via blending

AbstractCarboxylated cellulose nanocrystals (cCNCs) were blended with high‐quality commercial latex to enhance key pressure‐sensitive adhesive (PSA) properties: tack, peel strength, and shear adhesion. Initially, a 25–1 fractional factorial design was used to evaluate the effect of five factors: cCNC type (never‐dried vs. dried re‐dispersed), the use of sonication to disperse the cCNC, cCNC loading, blend temperature, and mixing speed. The regression analysis identified optimal blend conditions and the three most significant factors. It was found that increasing mixing speed had the strongest positive impact on all three PSA properties. A subsequent design of experiments looked at using a different mixing system—a homogenizer—and the data were viewed relative to the mixing power. Further increase in mixing beyond the original design framework led to increase in shear adhesion but decreased tack and peel strength. Nevertheless, in all cases, the PSA properties of the blended latexes exceeded that of the base‐case latex without cCNCs. The second factor of importance was the cCNC loading. The blending of cCNCs at levels beginning at 0.5 phm (parts per hundred parts monomer) led to the simultaneous improvement in all three PSA properties compared to the base‐case latex. The 1 phm level appeared to provide the best impact on the PSA properties. Finally, the need to sonicate the cCNCs dispersions before blending was significant. The results were further supported by rheological measurements, which demonstrated significant increase in viscosity with cCNC addition. This study clearly demonstrates the effectiveness of cCNC blending to improve all PSA properties simultaneously and provides practical insights for industrial‐scale application.

Carboxylated cellulose nanocrystal cryogel monoliths: a multi-tool study of morphology and porosity of pure and magnetite nanoparticle-decorated CNC scaffolds

Tissue scaffolds are known to benefit from incorporation of nanoscale bio-additives like cellulose nanocrystals (CNC), which can affect porosity as an important tunable design parameter for bio-based scaffolds. In this paper, we probe how freeze-casting of carboxylated cellulose nanocrystals and CNC derivatized with magnetite nanoparticles yields macroscale cryogel scaffold monoliths. Cryogel topographical features and macropore morphologies depend on the conditions under which ice formation takes place, and on exposure to static magnetic fields. We examine porosity over several length scales with scanning electron microscopy (SEM) coupled with Local Thickness Euclidean distance image processing, small angle X-ray scattering (SAXS), and dynamic vapor sorption (DVS). SAXS data fitted with a mass fractal model and power law suggest that CNC particles aggregate to form well-defined compact walls in the range of 96.7–27.3 nm for all samples, while inclusion of Fe3O4 nanoparticles disrupts this compactness in the range of 27.3–4.8 nm. Analysis of DVS reveals that nanoparticles directly impact water uptake by the cryogel scaffolds and can reduce water sorption in mesopores with a radius of 5–6 nm.

Bio‐inspired metal ion coordination cross‐linking synergistic strategy to enhance the interfacial properties of carbon fiber composites

AbstractThe application of carbon fiber (CF) in carbon fiber composites has faced limitations due to its surface chemical inertness. To overcome this challenge, this study draws inspiration from metal ion‐enhancing exquisite hierarchical and multiphase structures observed in biological materials. The research proposes a novel approach to enhance the interfacial bonding of CF/Epoxy (E‐51) composites by utilizing tannic acid (TA), carboxylated cellulose nanocrystals (CNCs), Fe3+ ions, and polyvinyl alcohol (PVA). This approach aims to create hydrogen bonding and metal synergistic networks on the surface of CFs through metal ion (Mn+) coordination cross‐linking synergistic (MCCS) interactions. Implementing MCCS strategy resulted in significant improvements in the mechanical properties of the hybrid reinforcements compared to untreated CF composites. The flexural strength, flexural modulus, interlaminar shear strength, and interfacial shear strength experienced respective increase of 50.9%, 72.8% 59.4%, and 61.9%. Moreover, the damping properties of the composites exhibited significant improvements. These positive outcomes can be attributed to the formation of chelation and dense hydrogen bonding networks between TA, Fe3+, CNC, and PVA. Furthermore, CNC and PVA formed cross‐linked nanolayers that effectively deflected cracks and facilitated high energy consumption at the interface. This proposed approach provides a sustainable, environmentally friendly, and efficient method for surface modification in the preparation of high‐performance fiber composites.Highlights Metal ion (Mn+) coordination cross‐linking synergistic strategy is proposed. Tannins/Fe3+/CNCs/PVA form multiphase nanolayers. Metal ion coordination cross‐linking enhances delicate multiphase structures. The prepared carbon fiber composites exhibit excellent properties. The as‐prepared carbon fiber composite has promising applications.

Regulating water flux of loose nanofiltration membrane by dopamine and cellulose nanocrystals for enhanced dye/salt separation

Nanofiltration (NF) membranes are widely used for dye and salt separation, however, a dense NF membrane is generally formed during interfacial polymerization, inducing low permeability of the membrane. Herein, a loose structure of the NF was prepared and regulated by additional other components, such as dopamine (DA) and carboxylated cellulose nanocrystal (C-CNC) through changing the interactions between water and oil phases. The results show that C-CNC not only improves hydrophilicity of the separation layer, but also controls the layer smooth and loose. The obtained membrane with suitable loose structure exhibits high water permeance (37.5 L m−2 h−1 bar−1) and rejection (above 99 %) for dyes including methyl blue (MB), congo red (CR) and direct red 80 (DR80). Additionally, it exhibits low rejection towards NaCl (∼10 %) and Na2SO4 (∼14 %), but good dye/salt separation factor of 451. The as-fabricated membrane is proved to have long-term stability, chlorine resistance and tolerance towards complex conditions (such as wide pH range, high temperature and composite separation system). The membrane shows good antifouling performance as well. Over all, the prepared membrane is promising for practical applications in textile effluent treatment, resources recycle and molecular separation.

Preparation and characterization of cinnamon essential oil Pickering emulsion stabilized by zein/carboxylated cellulose nanocrystals composite nanoparticles

The composite nanoparticles labeled as ZCP/C–CNC were synthesized by the combination of zein colloidal nanoparticles (ZCP) and carboxylated cellulose nanocrystals (C–CNC). The effects of the mass ratio of ZCP to C–CNC on the particle size, polydispersity index, ζ-potential, surface wettability and microstructure of ZCP/C–CNC were studied. The ZCP/C–CNC were used to stabilize cinnamon essential oil (CEO). The effects of ZCP/C–CNC on the properties of Pickering emulsions were investigated, including the interfacial tension, stability, encapsulation efficiency (EE), interfacial structure and antibacterial activity. With increasing of ZCP, the average particle size of ZCP/C–CNC firstly decreased and then increased, which was the smallest (196 nm) when the mass ratio of ZCP to C–CNC was 1. Scanning electron microscopy (SEM) showed that the structure of composite nanoparticles was featured that C–CNC layers wrapped ZCP. Confocal laser scanning microscope (CLSM) showed that CEO was effectively encapsulated by ZCP/C–CNC. When the mass ratio of ZCP to C–CNC was 1, the three-phase contact angle of the nanoparticle was 89.65°, showing the best surface wettability. And the CEO Pickering emulsion stabilized by this nanoparticle exhibited the smallest average particle size. It also showed the best stability and the best antibacterial activity against E. coli, S. aureus and S. putrefaciens. The EE of composite nanoparticles for CEO was significantly higher than that of pure ZCP or C–CNC particles, which all exceeded 91%. The Pickering emulsions stabilized by ZCP/C–CNC provided a promising alternative for the delivery of antimicrobial essential oils in the food, active packaging material and other related industries.

Smart antibacterial nanocellulose packaging film based on pH-stimulate responsive microcapsules synthesized by Pickering emulsion template

Spoilage results in food waste and endangers consumer health, and the smart antibacterial packaging can effectively inhibit bacterial growth and reduce food spoilage. In this study, the smart antibacterial nanocellulose packaging films were developed by adding the pH-stimulated responsive microcapsules into cellulose nanofibril (CNF) film-forming. The microcapsules were synthesized by interfacial polymerization of Pickering emulsion. Carboxylated cellulose nanocrystals as solid particles stabilized the composited oil phase to prepare the oil-in-water Pickering emulsion. The emulsion with the particle concentration of 1.25 wt% and the oil phase mass fraction of 7.5 % processes excellent stability and uniform particle size, was chosen to synthesize microcapsules. The cinnamaldehyde in the film with the addition amount of microcapsules 0.6 g burst released in the first 1 h and then slowly, and the cumulative release at pH 2.0, 4.0, 5.5 and 7.2 was 28.43 μg/cm2, 18.84 μg/cm2, 16.52 μg/cm2 and 12.89 μg/cm2, respectively. The inhibitory rate of film against both E. coli and L. monocytogenes reached 99 % at pH 4.0. The shelf life of pork packed by the film prolonged to nearly 9 d at room temperature. The developed films have the potential to be used in food packaging.

Colloidal Stability Window for Carboxylated Cellulose Nanocrystals: Considerations for Handling, Characterization, and Formulation.

The scale of production of cellulose nanocrystals (CNCs) has increased dramatically to meet the growing demand for sustainably sourced materials. This work defines the colloidal stability window for commercially produced carboxylated CNCs (DextraCel) compared to the more traditional sulfated CNCs. Phase diagrams showing the stable, reversibly agglomerated, irreversibly aggregated/sedimented, and colloidal glass "zones" as a function of suspension pH, ionic strength, CNC surface charge content, counterion, and concentration are presented. The pKa of carboxylated CNCs was measured to be 5.1, and suspensions of carboxylated CNCs (0.5-1.5 wt %) were visually stable from pH 3 to 11 (without salt). Carboxylated CNCs were highly sensitive to ionic strength, demonstrating some agglomeration with as little as 5 mM NaCl, supporting that weak acid surface groups and lower charge contents make CNCs more sensitive to solution conditions. Surface charge content had the greatest influence on colloidal stability followed by the counterion; carboxylated CNCs were more stable in the "as-received" sodium form, whereas sulfated CNCs had improved stability in acid form after ion exchange. The stability of carboxylated CNCs with industrially relevant additives (ionic and nonionic surfactants and initiators) was also investigated. Less concentrated suspensions were more colloidally stable, emphasizing that characterization and processing of CNCs favor dilute conditions. If carboxylated CNCs are subjected to conditions outside of their colloidal stability window, simple dilution or pH adjustment does not return them to colloidally stable discrete nanoparticles; however, ultrasonication can redisperse agglomerates. This study offers guidelines for handling carboxylated CNCs to broaden the range of products that can be improved by their incorporation.

Development of a multifunctional food packaging for meat products by incorporating carboxylated cellulose nanocrystal and beetroot extract into sodium alginate films.

Consumers' pursuit for safe meat products is challenging to develop smart food packaging with proper mechanical properties and multifunctional properties. Therefore, this work attempted to introduce carboxylated cellulose nanocrystal (C-CNC) and beetroot extract (BTE) into sodium alginate (SA) matrix films to enhance their mechanical properties and endow them with antioxidant properties and pH-responsive capacity. The rheological results showed the C-CNC and BTE were consistently dispersed in the SA matrix. The incorporation of C-CNC made the surface and cross-section of the films rough but still dense, thus significantly improving the mechanical properties of the films. The integration of BTE provided antioxidant properties and pH responsiveness without significantly changing the thermal stability of the film. The highest tensile strength (55.74±4.52MPa) and strongest antioxidant capacities were achieved for the SA-based film with BTE and 10wt% C-CNC. Additionally, the films possessed higher UV-light barrier properties after incorporating BTE and C-CNC. More notably, the pH-responsive films discolored when TVB-N value exceeded 18.0mg/100g during storage of pork at 4°C and 20°C, respectively. Therefore, the SA-based film with enhanced mechanical and functional properties has a high potential for quality detection in smart food packaging applications.

Fabricating a visibly colorimetric film via self-releasing of anthocyanins from distributed mulberry pomace particles in hydrophilic sodium carboxymethyl starch-based matrix to monitor meat freshness

A highly distinguishable indicator film was developed based on sodium carboxymethyl starch, κ-carrageenan, carboxylated cellulose nanocrystals and mulberry pomace particles (MPPs). As the content of MPPs increased from 0 % to 6 %, the tensile strength decreased from 11.71 MPa to 5.20 MPa, the elongation at break increased from 26.84 % to 43.76 %, respectively, and the haze increased from 34.12 % to 52.10 %. The films accurately exhibit a color change from purple to blue-green under alkaline conditions. The enhanced haze improved the visible resolution of the films during the color-changing process. The films with the size of 7.50 mm × 7.50 mm and 10.0 mm × 10.0 mm exhibited obvious color changes when the total volatile basic nitrogen reached 14.60 mg/100 g and 19.04 mg/100 g, respectively, which accurately indicated the quality of pork and fish. This study will offer a simplified path to improve both accurate sensitivity and distinguishability for smart films.

Chiral Self-Assembly Behavior of Carboxylated Cellulose Nanocrystals Isolated by Recyclable Oxalic Acid from Degreasing Cotton

Carboxylated cellulose nanocrystals (OA-CNCs) isolated by aqueous recyclable oxalic acid hydrolysis from degreasing cotton were used to observe its self-assembly behavior and chiral nematic properties. The oxalic acid here served as the sole catalyst to esterify and hydrolyze the degreasing cotton. The results indicated that the obtained OA-CNC suspensions were spontaneously phase-separated into a chiral nematic mesophase above a critical concentration, and the occurrence of chiral self-assembly is highly dependent on the aspect ratio and the surface charge of the OA-CNC suspension. Scanning electron microscopy images of the cross section of OA-CNC solid films revealed a periodic ordered multilayer structure. The residual OA was easily recovered through simple re-crystallization method after reactions with a high recovery rate of at least 90%. The recycled OA (ROA) had excellent performance in terms of ROA-CNC yield even after reusing for five cycles. Moreover, the resultant ROA-CNCs from recycled OA could also form chiral nematic ordered phases with little change in the critical concentration and pitch, suggesting excellent suitability for sustainable OA-CNC production for photonics and other specialty applications.

Enhanced mechanical property and freeze-thaw stability of alkali-induced heat-set konjac glucomannan hydrogel through anchoring interface effects of carboxylated cellulose nanocrystals

The alkali-induced heat-set konjac glucomannan (KGM) hydrogels have drawn increasing attention due to their high absorbency and thermal irreversibility ability, but pure KGM hydrogels generally have defects of low strength and high syneresis rate. Cellulose nanocrystals and their derivatives, which have a very high specific surface area, good biocompatibility, biodegradability, and low toxicity, are promising candidates to solve this challenge. In this work, we propose the use of carboxylated cellulose nanocrystals (C–CNCs) as nanofillers for the strengthening of KGM hydrogels. The effects of the C–CNCs content on the microstructure and physical properties of the KGM hydrogels and their possible mechanism were investigated. The compressive test results indicate great improvement in the mechanical properties upon the addition of the C–CNCs for the KGM hydrogel and reached a maximum value at 20% loading. The microstructure analyses of the KGM hydrogel revealed that the well-distributed C–CNCs can act as a physical cross-linker to connect the neighboring KGM chains to strengthen the resultant hydrogel, based on their strong interactions, including hydrogen bonding and chain entanglements. Moreover, adding 20% C–CNCs can significantly decrease the syneresis after five repeated freeze-thaw cycles of the KGM hydrogels. Compared to pure KGM hydrogels, KGM/C–CNCs nanocomposite hydrogels demonstrated higher water-binding capability based on Low-field nuclear magnetic resonance. These findings indicate that C–CNCs are considered anchors for KGM chains as well as reinforcement fillers in the polymer matrix, which contributes significantly to the mechanical property of the nanocomposite. Therefore, C–CNCs were a promising material to be applied for modulating the mechanical and freeze-thaw stability properties of the polysaccharide-based hydrogel in food and biomedical applications.

Large-Scale Preparation of Carboxylated Cellulose Nanocrystals and Their Application for Stabilizing Pickering Emulsions.

Cellulose nanocrystals (CNCs) with varied unique properties have been widely used in emulsions, nanocomposites, and membranes. However, conventional CNCs for industrial use were usually prepared through acid hydrolysis or heat-controlled methods with sulfuric acid. This most commonly used acid method generally suffers from low yields, poor thermal stability, and potential environmental pollution. Herein, we developed a high-efficiency and large-scale preparation strategy to produce carboxylated cellulose nanocrystals (Car-CNCs) via carboxymethylation-enhanced ammonium persulfate (APS) oxidation. After carboxymethylation, the wood fibers could form unique "balloon-like" structures with abundant exposed hydroxy groups, which facilitated exfoliating fibril bundles into individual nanocrystals during the APS oxidation process. The production process under controlled temperature, time period, and APS concentrations was optimized and the resultant Car-CNCs exhibited a typical structure with narrow diameter distributions. In particular, the final Car-CNCs exhibited excellent thermal stability (≈346.6 °C) and reached a maximum yield of 60.6%, superior to that of sulfated cellulose nanocrystals (Sul-CNCs) prepared by conventional acid hydrolysis. More importantly, compared to the common APS oxidation, our two-step collaborative process shortened the oxidation time from more than 16 h to only 30 min. Therefore, our high-efficiency method may pave the way for the up-scaled production of carboxylated nanocrystals. More importantly, Car-CNCs show potential for stabilizing Pickering emulsions that can withstand changeable environments, including heating, storage, and centrifugation, which is better than the conventional Sul-CNC-based emulsions.

Bio-inspired fabrication of adsorptive ultrafiltration membrane for water purification: Simultaneous removal of natural organic matters, lead ion and organic dyes

Conventional ultrafiltration membrane is difficult to achieve the multi-component removal of water contaminants including macromolecules and small ions. Meanwhile, a large number of petrochemical-based polymers as membrane material is raising concerns about environmental risk. In this study, we present a feasible way for the manufacture of multifunctional cellulose-based nanocomposite membranes via bio-fabrication by Acetobacter xylinus for water purification. The harvested bacterial cellulose (BC) pellicle was coated by polydopamine (PDA) as a functional layer and molecular linker to immobilize carboxylated cellulose nanocrystals (C-CNCs) to prepare BC/PDA14h/CNCs membrane (BCM/PDA14h/CNCs). The composited PDA and C-CNCs on the BC nanofibers endowed the membrane with a maximum adsorption capacity of up to 167.80 mg g−1 for Pb2+, and 251.58 mg g−1 for methylene blue (MB). Multiple contaminants (heavy metals, organic dyes, and natural organic matter (NOM)) can also be treated by BCM/PDA14h/CNCs simultaneously during the dynamic filtration process. The removal efficiency of BCM/PDA14h/CNCs against the mixture of metal ions is inversely proportional to the radius of hydrated ions. The selective separation studies on binary dye mixtures showed that the separation efficiency of the membrane is mainly related to the electronegativity of dyes. The BCM/PDA14h/CNCs exhibited preferential adsorption for cationic dyes, with a separation efficiency was up to 98%. Dynamic fouling experiments confirmed that the BCM/PDA14h/CNCs presented excellent antifouling performance and showed a high flux recovery ratio. The multifunctional characteristic, high removal efficiency, excellent reusability and stability as well as environmentally friendly feature of the prepared membrane in the present study provide a sustainable approach for membrane fabrication and promising application in water purification.

Fabrication of untreated and silane-treated carboxylated cellulose nanocrystals and their reinforcement in natural rubber biocomposites

In this study, cellulose nanocrystal (CNC) was extracted from Napier grass stems and subsequently functionalized to carboxylated cellulose nanocrystal (XCNC) by using an environmentally friendly method, namely, the KMnO4/oxalic acid redox reaction. The XCNC was subsequently modified with triethoxyvinylsilane (TEVS), called VCNC, by using ultrasound irradiation. The characterization of the prepared XCNC and VCNC was performed. The needle-like shape of XCNC was observed with an average diameter and length of 11.5 and 156 nm, respectively. XCNC had a carboxyl content of about 1.21 mmol g−1. The silane treatment showed no significant effects on the diameter and length of XCNC. When incorporated into natural rubber (NR), both XCNC and VCNC showed very high reinforcement, as evidenced by the substantial increases in modulus and hardness of the biocomposites, even at very low filler loadings. However, due to the high polarity of XCNC, tensile strength was not significantly improved with increasing XCNC loading up to 2 phr, above which it decreased rapidly due to the filler agglomeration. For VCNC, the silane treatment reduced hydrophilicity and improved compatibility with NR. The highly reactive vinyl group on the VCNC’s surface also takes part in sulfur vulcanization, leading to the strong covalent linkages between rubber and VCNC. Consequently, VCNC showed better reinforcement than XCNC, as evidenced by the markedly higher tensile strength and modulus, when compared at an equal filler loading. This study demonstrates the achievement in the preparation of a highly reinforcing bio-filler (VCNC) for NR from Napier grass using an environmentally friendly method and followed by a quick and simple sonochemical method.