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A robust and flexible cellulose nanofiber (CNF)-supported cryogel was prepared by chemical crosslinking method using γ-glycidoxypropyltrimethoxysilane (GPTMS) and branched polyethylenimine (PEI). FT-IR, elemental analysis, EDS and solid state ¹³C NMR analysis revealed that the PEI had been successfully modified on cellulose via reacting with GPTMS....
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The current study is focused on the simple synthesis of two novel biosorbent beads: BASB/STMP and CNFB/STMP, derived respectively from bleached almond shell (BAS) and cellulose nanofiber from almond shell (CNF) by means of chemical crosslinking with sodium trimetaphosphate (STMP). These biosorbents were thoroughly characterized in terms of structur...
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... Current research efforts are focused on increasing the structural stability and strength of cellulose beads by introducing highly efficient crosslinkers into composites. Divalent or trivalent metal ions, such as Al(III), Ca(II), and Fe(III), as well as organic compounds, such as epichlorohydrin (ECH), glutaraldehyde, (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and polyethylenimine (PEI), are effective crosslinking agents that can react with functional groups, including carboxylate anion (-COO¯) and hydroxyl (-OH) groups, to form chemical/physical crosslinking interactions such as covalent, ionic, and hydrogen bonds (Cheng et al. 2017;Kim et al. 2009;Li et al. 2020;Riva et al. 2021;Yang et al. 2021;Zhao et al. 2015). Furthermore, the reactions of metal ions or organic compounds, such as ECH, typically proceed at high temperatures or over long periods (Jung et al. 2022;Li et al. 2020). ...
... Previous studies investigated the effects of crosslinkers on the mechanical performance of cellulose composites (Cheng et al. 2017;Tang et al. 2020;Zhang et al. 2014). Generally, the mechanical performance of composites is evaluated via stress-strain testing, which reflects the relationship between the compressive stress and deformation of the material under an applied stress from top to bottom. ...
... The significant differences were established for p < 0.001 stretching vibrations of C-O and C-O-Si bonds. The C-O-Si bonds were formed via a condensation reaction, in which silicon hydroxyl groups reacted with the hydroxyl groups of CMC chains(Cheng et al. 2017;Zhang et al. 2014). ...
Carboxymethylcellulose (CMC) composite beads formed by physicochemical crosslinking have emerged as functional biomaterials. However, the effects of the crosslinker dosage on the structure and properties of these beads have not been thoroughly examined. In this study, robust CMC composite beads with porous channel structures were synthesized via a dropping method and acetic acid solidification after physicochemical crosslinking with (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and polyethylenimine (PEI). The influence of the PEI dosage on the physicochemical, structural, and physical properties of the produced CMC/GPTMS/PEI beads (CGPBs) was investigated. The physical properties of wet CGPBs were evaluated by conducting rheological tests, such as strain/frequency sweep and creep/recovery tests. With increasing PEI dosage, more PEI species effectively reacted with CMC and GPTMS molecules through multiple physicochemical interactions (covalent/ionic/hydrogen bonds) to increase the channel width, channel wall thickness, nanopore size, and CGPB porosity and improve the mechanical properties of wet CGPBs, such as yield stress, storage modulus, and resistance to deformation. Moreover, CGPBs exhibited pH-induced response behavior, and their swelling/shrinkage and mechanical stability were strongly affected by the solution pH. This study establishes a relationship between the PEI dosage and physicochemical, structural, and mechanical properties of CGPBs, providing theoretical guidance for the design of stable CMC composite beads.
... CNF-alginate composite scaffolds provide an easily crosslinked material with structural stability and shape control. Compared to the previous studies of CNF-only aerogels that lacked a simple crosslinking method and alginate-only aerogels that lacked structural stability, this composite biotemplate approach addresses both concerns [48,49,63]. Cobalt nanoparticles integrated into a CNF-alginate scaffold resulting from chemical reduction, rinsing, and supercritical drying with CO 2 enables a metallized composite material with a tunable metal and metal oxide phase, mechanical strength, magneto-responsiveness, and electrochemical performance via pyrolysis and thermal oxidation. ...
Tunable porous composite materials to control metal and metal oxide functionalization, conductivity, pore structure, electrolyte mass transport, mechanical strength, specific surface area, and magneto-responsiveness are critical for a broad range of energy storage, catalysis, and sensing applications. Biotemplated transition metal composite aerogels present a materials approach to address this need. To demonstrate a solution-based synthesis method to develop cobalt and cobalt oxide aerogels for high surface area multifunctional energy storage electrodes, carboxymethyl cellulose nanofibers (CNF) and alginate biopolymers were mixed to form hydrogels to serve as biotemplates for cobalt nanoparticle formation via the chemical reduction of cobalt salt solutions. The CNF-alginate mixture forms a physically entangled, interpenetrating hydrogel, combining the properties of both biopolymers for monolith shape and pore size control and abundant carboxyl groups that bind metal ions to facilitate biotemplating. The CNF-alginate hydrogels were equilibrated in CaCl 2 and CoCl 2 salt solutions for hydrogel ionic crosslinking and the prepositioning of transition metal ions, respectively. The salt equilibrated hydrogels were chemically reduced with NaBH 4 , rinsed, solvent exchanged in ethanol, and supercritically dried with CO 2 to form aerogels with a specific surface area of 228 m 2 /g. The resulting aerogels were pyrolyzed in N 2 gas and thermally annealed in air to form Co and Co 3 O 4 porous composite electrodes, respectively. The multifunctional composite aero-gel's mechanical, magnetic, and electrochemical functionality was characterized. The coercivity and specific magnetic saturation of the pyrolyzed aerogels were 312 Oe and 114 emu/g Co , respectively. The elastic moduli of the supercritically dried, pyrolyzed, and thermally oxidized aerogels were 0.58, 1.1, and 14.3 MPa, respectively. The electrochemical testing of the pyrolyzed and thermally oxidized aerogels in 1 M KOH resulted in specific capacitances of 650 F/g and 349 F/g, respectively. The rapidly synthesized, low-cost, hydrogel-based synthesis for tunable transition metal multifunctional composite aerogels is envisioned for a wide range of porous metal electrodes to address energy storage, catalysis, and sensing applications.
... The aerogel exhibited excellent compressibility and shape recovery, with a maximum unrecoverable strain of only 6.5% at 70% strain, and the storage modulus was as low as 20 Pa. Cheng et al. [98] crosslinked CNFs with γ-glycidoxypropyltrimethoxysilane (GPTMS) and branched polyethylenimine (PEI) via etherification. The mixture was freeze-dried at −50 • C for 24 h and then heated at 110 • C for 30 min. ...
... Crosslinking mechanisms: (a) the esterification of 1,2,3,4-butanetetracarboxylic (BTCA) and TEMPO-mediated oxidation cellulose nanofibrils (TCNFs)[95]; (b) the etherification of γglycidoxypropyltrimethoxysilane (GPTMS), branched polyethylenimine (PEI), and cellulose nanofibers (CNFs)[98]; (c) grafting 2-hydroxyethyl methacrylate (HEMA) onto CNFs via radical polymerization[97]. ...
... Crosslinking mechanisms: (a) the esterification of 1,2,3,4-butanetetracarboxylic (BTCA) and TEMPO-mediated oxidation cellulose nanofibrils (TCNFs)[95]; (b) the etherification of γ-glycidoxypropyltrimethoxysilane (GPTMS), branched polyethylenimine (PEI), and cellulose nanofibers (CNFs)[98]; (c) grafting 2-hydroxyethyl methacrylate (HEMA) onto CNFs via radical polymerization[97]. ...
Energy problems have become increasingly prominent. The use of thermal insulation materials is an effective measure to save energy. As an efficient energy-saving material, nanocellulose aerogels have broad application prospects. However, nanocellulose aerogels have problems such as poor mechanical properties, high flammability, and they easily absorbs water from the environment. These defects restrict their thermal insulation performance and severely limit their application. This review analyzes the thermal insulation mechanism of nanocellulose aerogels and summarizes the methods of preparing them from biomass raw materials. In addition, aiming at the inherent defects of nanocellulose aerogels, this review focuses on the methods used to improve their mechanical properties, flame retardancy, and hydrophobicity in order to prepare high-performance thermal insulation materials in line with the concept of sustainable development, thereby promoting energy conservation, rational use, and expanding the application of nanocellulose aerogels.
... However, it is necessary to introduce an alkoxysilane coupling agent to enhance the strong connection between nanocellulose and alum. γ-Glycidoxypropyl trimethoxysilane (GPTMS) with good biocompatibility and bioactivity is a promising alkoxysilane coupling agent [22]. GPTMS was hydrolyzed in an aqueous solution to form silicon hydroxyl groups that could react with the hydroxyl groups on the nanocellulose via a condensation reaction [23]. ...
In this work, a novel nanocellulose/alum/chitosan/polyethyleneimine biohybrid aerogel (NACPBA) beads adsorbent was successfully prepared to remove diclofenac sodium (DS) from wastewater. The NACPBA beads adsorbent was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometer, and Brunauer–Emmett–Teller. A possible adsorption mechanism was also discussed. The experimental results showed that the adsorption process was followed by a pseudo-second-order kinetic model and Sips isotherm model with the calculated maximum adsorption capacity of 321.3 mg/g on DS. It was much higher than most of the previously reported works. The adsorption capacity of NACPBA beads on DS was increased rapidly within 120 min, especially in the first 60 min. Furthermore, after five regeneration cycles, NACPBA still retained a good adsorption capacity of 103.7 mg/g with a removal efficiency of 50%. Moreover, 95.4% of DS was removed from river water (simulated 5 mg/L DS-contaminated wastewater). The possible adsorption mechanism was primarily governed by electrostatic attractions and hydrogen bond interactions.
... Compared with pristine CF, a new absorption peak appeared at 1238 cm À1 in the spectrum of the P-HNTs/PA/rGO-6@CF, attributing to the stretching vibration peak of P O in PA. Meanwhile, the absorption peaks at 1579 and 1541 cm À1 assigned to the stretching vibration of N-H bonds in b-PEI, 41 demonstrating the coverage of PA and b-PEI. In addition, from the Raman spectra in Figure 2b, the intensity ratio of D band at 1347 cm À1 to G band at 1591 cm À1 of the P-HNTs/PA/GO-6@CF was about 1.00. ...
Flexible piezoresistive pressure sensors have great application potential in many emerging fields such as electronic skin, artificial intelligence and human healthcare. However, most of the sensors are flammable, which will easily initiate fire hazard in case of short circuit. Herein, a flame‐retardant and conductive cotton fabric (CF) was fabricated for piezoresistive pressure sensor by layer‐by‐layer (LBL) assembly of branched polyethyleneimine (b‐PEI) modified halloysite nanotubes (HNTs), phytic acid (PA) and graphene oxide (GO) and the subsequent thermal reduction of GO. The composite coating layer endowed the obtained CF with excellent flame retardancy. The limiting oxygen index of the CF reached 32.72% and the char length after vertical burning test was only 3.8 cm, attributing to the physical barrier role of the HNTs and graphene nanosheets as well as the phosphorus‐nitrogen synergism between PA and b‐PEI. The CF‐based piezoresistive pressure sensor exhibited fast and accurate response, good signal stability and fatigue resistance (3000 loading‐unloading cycles) and was able to be applied for detecting human motions including pulse beat, pronunciation and various physical activities. The preparation method in this work is simple, and the piezoresistive pressure sensor shows great application prospect in the field of flexible electronics with high safety.
... However, it is necessary to introduce an alkoxysilane coupling agent to enhance the strong connection between nanocellulose and alum. γ-Glycidoxypropyl trimethoxysilane (GPTMS) with good biocompatibility and bioactivity is a promising alkoxysilane coupling agent [22]. GPTMS was hydrolyzed in an aqueous solution to form silicon hydroxyl groups that could react with the hydroxyl groups on the nanocellulose via a condensation reaction [23]. ...
In this work, a novel nanocellulose/chitosan biohybrid aerogel (NCBA) bead adsorbent was successfully prepared from oxidized bamboo nanocellulose and chitosan to remove diclofenac sodium (DS) from wastewater. Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to characterize the preparation of NCBA bead adsorbent. The results demonstrated that the adsorption kinetics were well described by the pseudo-second-order model, and the adsorption isotherms were well fitted by the Sips isotherm model with the maximum adsorption capacity of 321.26 mg/g on DS, which is much higher than most of the previously reported works. The absorption mechanism was governed by electrostatic interaction and hydrogen bond interaction. Moreover, the resulting bead remained a high removal efficiency after 5 regeneration cycles. In summary, it had been proved that the aerogel bead was an efficient bio-sorbent for removing DS from aqueous solutions.
... NFAs can exhibit good compressibility and resilience through cross-linking, which are very important for their practical applications [41][42][43], However, NFAs assembled by flexible nanofibers in general showed obvious hysteresis loops and large plastic deformations after large strain cyclic compressions [39]. However, EVOH NFAs could withstand high compression strain and show a resilience of about 100%, although after 500 compression cycles under strain of 60%, an obvious plastic deformation (24.43%) was observed (Fig. S11b). ...
Developing high-performance, low-cost and large-scale absorbent materials is crucial for the treatment of water pollution caused by pollutants leakage and emission. Herein, superelastic and superhydrophobic thermoplastic polymeric nanofibrous aerogels (NFAs) were created for removal pollutants from water by using a facile and effective method. Poly(vinyl alcohol-co-ethylene) (EVOH) nanofibers fabricated by mass-production techniques were used to construct three-dimensional NFAs through combing freeze-drying process and cross-linking treatment. The optimal parameters for creating EVOH NFAs with good formability and resilience, including composition and ratio of dispersion, dosage of cross-linking agent were obtained through experiments. EVOH nanofibers bonded with each other by glutaraldehyde under acidic conditions to from fibrous network structure in EVOH NFAs. The silane-coated EVOH NFAs were prepared through further modification with vapor-phase methyltrichlorosilane. The deposition of siloxane improved mechanical strength and decreased plastic deformation after 500 cyclic compressions. An asperate fibrous and granular siloxane coating was deposited on the surface of EVOH NFAs. The surface water contact angle increased from 104.4° ± 4.0° to 152.7° ± 1.9°, wettability of NFAs transitioned to being superhydrophobic. Silane-coated EVOH NFAs exhibited superior absorption capacity (40–92 g/g) for a variety of organic pollutants. The organic pollutants would be collected and the sorbents could be reused after distillation or squeezing. A successful scale-up of such materials open up a new insight into design polymeric aerogels in low-cost and large-scale with substantial industrial water purification applications.
... NFAs can exhibit good compressibility and resilience through cross-linking, which are very important for their practical applications [41][42][43], However, NFAs assembled by exible nano bers in general showed obvious hysteresis loops and large plastic deformations after large strain cyclic compressions [39]. However, EVOH NFAs could withstand high compression strain and show a resilience of about 100%, although after 500 compression cycles under strain of 60%, an obvious plastic deformation (24.43%) was observed (Fig. S11b). ...
Developing high-performance, low-cost and large-scale absorbent materials is crucial for the treatment of water pollution caused by pollutants leakage and emission. Herein, superelastic and superhydrophobic thermoplastic polymeric nanofibrous aerogels (NFAs) were created for removal pollutants from water by using a facile and effective method. Poly(vinyl alcohol-co-ethylene) (EVOH) nanofibers fabricated by mass-production techniques were used to construct three-dimensional NFAs through combing freeze-drying process and cross-linking treatment. The optimal parameters for creating EVOH NFAs with good formability and resilience, including composition and ratio of dispersion, dosage of cross-linking agent were obtained through experiments. EVOH nanofibers bonded with each other by glutaraldehyde under acidic conditions to from fibrous network structure in EVOH NFAs. The silane-coated EVOH NFAs were prepared through further modification with vapor-phase methyltrichlorosilane. The deposition of siloxane improved mechanical strength and decreased plastic deformation after 500 cyclic compressions. An asperate fibrous and granular siloxane coating was deposited on the surface of EVOH NFAs. The surface water contact angle increased from 104.4 ± 4.0° to 152.7 ± 1.9°, wettability of NFAs transitioned to being superhydrophobic. Silane-coated EVOH NFAs exhibited superior absorption capacity (40–92 g/g) for a variety of organic pollutants.The organic pollutants would be collected and the sorbents could be reused after distillation or squeezing. A successful scale-up of such materials open up a new insight into design polymeric aerogels in low-cost and large-scale with substantial industrial water purification applications.
... In addition, the modifications significantly increase in the number of functional groups present on the surface and also enhance the material properties such as adsorption capacity [19]. For example, in a study performed by Cheng et al. [23], cellulose nanofiber-supported cryogels were synthesized by a chemical crosslinking method using glycidoxypropyltrimethoxysilane and branched PEI. The adsorption capacities of the obtained materials were investigated to remove Cu 2+ . ...
In this study, modified polyacrylamide (PAAm) cryogels with high dye holding capacity were synthesized with an easily and cheaply process and adsorption of Remazol Black B (RBB) with the synthesized materials was investigated. Firstly, PAAm cryogels were synthesized with free radical cryo-copolymerization method and they were modified with Hofmann reaction to form amine groups in the structure of the cyrogels. Then, to increase the removal efficiency of cryogels, polyethylenimine (PEI) molecules were crosslinked onto the cryogels via NH2 groups present in the PAAm gels modified by the Hofmann reaction. The original and modified cryogels were characterized with fourier transformed infrared spectroscopy, 13C nuclear magnetic resonance spectroscopy, scanning electron microscopy and thermogravimetric analysis. The point of zero charge (pHpzc) of the modified cryogels was found to be 7.13 and RBB removing capabilities of PEI-modified PAAm cryogels were investigated at pH between 2 and 7. In addition, the adsorption treatments were performed at different process time, incubation temperature, initial dye concentration and adsorbent amount to find maximum removal capacity of the adsorbent. The modified cryogels adsorbed maximum amount of RBB at pH 2 and the sorption process reached equilibrium in 6 h. It was observed that the adsorption efficiency did not change much with the increase in temperature. The maximum RBB removal capacity of the modified cyrogels was determined to be 201 mg/g when the initial RBB concentration was 200 mg/L, treatment time was 6 h at pH 2. Moreover, the adsorption of RBB dye with the modified cryogels takes place with a second order kinetic and RBB dye adsorption data showed compliance with the Langmuir isotherm. The findings of the study expose that the obtained PEI-modified PAAm cryogels are a hopeful material for RBB removal in aqueous environment.
... Correspondingly, the aerogel was very light 27 and could stand on flowers because of its lower density (28.29 mg/cm 3 , Figure 2d). Since the nanocellulose inside the aerogel was cross-linked, the aerogel had high compressive strength in the air 28 and could bear about 1200 times its own weight. ...
