Cellulose Aerogels Research Articles

Enhanced Triboelectric Nanogenerator Based on a Hybrid Cellulose Aerogel for Energy Harvesting and Self-Powered Sensing

Enhanced Triboelectric Nanogenerator Based on a Hybrid Cellulose Aerogel for Energy Harvesting and Self-Powered Sensing

Facile synthesis of porous cellulose aerogel beads with tunable core–shell microstructures and physical properties

Cellulose aerogel beads (CABs) have emerged as advanced biomaterials with numerous engineering applications, including chromatography and drug release. In this study, porous core–shell CABs were synthesized using a dilute ethanol solution-substitution-assisted freeze-drying. The formation mechanism of the CABs and the effect of ethanol concentration on the core–shell microstructures and physical properties were investigated. Cellulose hydrogel beads (CHBs) were formed through the exchange/neutralization of acetic acid with tetraethylammonium hydroxide (TEAOH)/urea. The cellulose chains dissolved in the cellulose–TEAOH/urea droplets regenerated from the edge to the inside of the droplet in an acetic acid bath. Notably, adding ethanol at a concentration of 10% before freeze-drying can result in core–shell CABs with non-obvious structural shrinkage, large particle size, uniform pores, and high porosity. Ethanol molecules induce ice crystal growth to form more uniform ice crystals during the freezing process. Additionally, by altering the TEAOH/urea molar ratios and cellulose concentrations of cellulose solutions, well-shaped and porous CABs were prepared, demonstrating the feasibility and availability of dilute ethanol solution-assisted freeze-drying. Consequently, the as-fabricated CABs had a dense micro-shell (1–9 μm) and loose millimetric-core with anisotropic pores (2–6 μm), exhibiting low density (0.06–0.09 g/cm3), high porosity (87.0–91.5%), and noteworthy thermal stability.

Sustainable and low-cost cellulose aerogel-based absorber for solar steam generation

Solar steam generation is a promising technology for sustainable seawater desalination. However, its practical application is hindered by the low water evaporation rate and the high cost of materials. Carbon aerogels have demonstrated superior properties for clean water production through solar steam generation, but the complex and time-consuming preparation process inhibits their development and applications. In this study, high-performance solar steam absorbers based on cellulose-derived carbon aerogels were prepared from paper and waste paper using a simple green method. The fabricated carbon aerogels have a typical microporous structure (pore diameter: 20–250 µm), super-hydrophilic properties, good mechanical properties and efficient solar light absorption (∼96 %), which make them ideal for application in solar steam generation. Three different configurations based on cellulose and carbon aerogels were fabricated (bulk absorber, double-layer absorbers and ink-based absorber) to achieve the best design with high efficiency for steam generation. The surface temperature of the bulk absorber and dry double-layer absorbercan achieve 100 °C under 1 kWm−2irradiation. Among all configurations, the double-layer absorbers represented the highest efficiencies, 90.4 % for paper and 84.3 % for waste paper, under 1 kWm−2 irradiation, which are higher than most reported results. According to the results, the sustainable cellulose-based double-layer absorbers were promising materials for efficient solar steam generation due to their high hydrophilicity, high sunlight absorption, open porous structure, non-toxicity, biodegradability, availability and low cost.

Highly compressible and hydrophobic nanofibrillated cellulose aerogels for cyclic oil/water separation

Nanofibrillated cellulose (NFC)-based aerogels are ideal oil-sorbent materials, but the poor structural stability and hydrophilicity restrain their practical applications in the fields of oil/water separation. In the present work, we report a facile strategy for constructing a hydrophobic nanofibrillated cellulose aerogel for cyclic oil/water separation. Briefly, an aerogel matrix of C-g-PEI with multiple cross-linked network structures was constructed via the combined use of oxidized-NFC (ONC), polyethyleneimine (PEI), and ethylene glycol diglycidyl ether (EGDE), followed by rapid in situ deposition of poly(methyl trichlorosilane) (PMTS) through a low-temperature gas-solid reaction. The resulting ONC-based aerogel (C-g-PEI-PMTS) exhibits the advantages of ultralight (53.80 mg/cm3), high porosity (95.73 %), hydrophobicity (contact angle of 130.0°) and remarkable elasticity (95.86 %). Meanwhile, the composite aerogel of C-g-PEI-PMTS is extremely suitable for oil sorption-desorption by a simple mechanical squeezing method. After 10 cycles of sorption-desorption, the sorption capacity of the aerogel towards various oils reached almost the same level as in the first cycle. The filtration separation efficiency for the trichloromethane-water mixtures remained at 99 % after 50 cycles, demonstrating encouraging reusability. In summary, an efficient strategy to prepare NFC-based aerogel with highly compressible and hydrophobic properties is developed, which expands the applications of NFC in the fields of oil/water separation.

Tailoring biogenic straw insulation from additive manufacturing

In the pursuit of carbon-storing materials that could help accomplish high levels of building sustainability, wheat straw has emerged as a promising alternative to fossil fuel-based building materials. Straw is 100% biodegradable and abundant agricultural waste used in the construction 400 years ago, and it has been reported to have the lowest embodied carbon when measured against other typical insulating materials. Here we report additive manufacturing of carbon-sequestration insulation panel materials by upcycling cellulose fibrils from wheat straw. Cellulose obtained from alkaline and 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation shows thermal conductivity of 0.036 W m−1 K−1, alongside elastic and flexural modulus of 900 MPa and 502 MPa, respectively. In addition, an in-situ hydrophobic treatment in the cellulose-based insulation panels is achieved with an average water contact angle of 133.7° Furthermore, the extrusion-based additive manufacturing of a 3D-printable ink obtained by mixing the cellulose and silica aerogel precursor is accomplished, with the printed material exhibiting structural integrity, thus showing great potential towards the development of state-of-the-art, sustainable materials for carbon-sequestration building applications.

Covalent Crosslinking Cellulose/Graphene Aerogels with High Elasticity and Adsorbability for Heavy Metal Ions Adsorption.

With the fast development of modern industry, heavy metal contaminant became more severe. How to remove heavy metal ions in water in a green and efficient way is a prominent problem in current environmental protection. The adsorption of cellulose aerogel as a novel heavy metal removal technology has many advantages, including abundant resources, environmental friendly, high specific surface, high porosities and without second pollution, which means it has a wide application prospect. Here, we reported a self-assembly and covalent crosslinking strategy to prepare elastic and porous cellulose aerogels using PVA and graphene and cellulose as precursor. The resulting cellulose aerogel had a low density of 12.31 mg cm-3 and excellent mechanical properties, which can recover to its initial form at 80% compressive strain. Meanwhile, the cellulose aerogel had strong adsorption capacity of Cu2+ (80.12 mg g-1), Cd2+ (102.23 mg g-1), Cr3+ (123.02 mg g-1), Co2+ (62.38 mg g-1), Zn2+ (69.55 mg g-1), and Pb2+ (57.16 mg g-1). In addition, the adsorption mechanism of the cellulose aerogel was investigated using adsorption kinetics and adsorption isotherm, and the conclusion was that the adsorption process was mainly controlled by chemisorption mechanism. Therefore, cellulose aerogel, as a kind of green adsorption material, has a very high application potential in future water treatment applications.

Effects of a Cellulose Aerogel Template on the Preparation and Adsorption Properties of Coal Gangue-Based Multistage Porous ZSM-5.

In this study, a ZSM-5/CLCA molecular sieve was prepared by the hydrothermal method using coal gangue as the raw material and cellulose aerogel (CLCA) as the green templating agent, which not only reduces the cost of traditional molecular preparation but also improves the comprehensive resource utilization rate of coal gangue. Through a series of characterization methods (XRD, SEM, FT-IR, TEM, TG, and BET), the crystal form, morphology, and specific surface area of the prepared sample were tested and analyzed. The performance of the adsorption process of malachite green (MG) solution was analyzed by adsorption kinetics and adsorption isotherm. The results show that the synthesized zeolite molecular sieve and the commercial zeolite molecular sieve are highly consistent. At a crystallization time of 16 h, a crystallization temperature of 180 °C, and an additive amount of cellulose aerogel of 0.6 g, the adsorption capacity of ZSM-5/CLCA for MG was up to 136.5 mg/g, much higher than that of commercially available ZSM-5. This provides an idea for the green preparation of gangue-based zeolite molecular sieves to remove organic pollutants from water. Moreover, the process of adsorbing MG on the multistage porous molecular sieve, which is spontaneous, conforms to the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model.

Facile synthesis of corn stalks-derived carbon aerogels: Characterization, adsorption of ciprofloxacin and energy storage applications

Cellulose aerogels were fabricated from the corn stalks-derived cellulose with poly(vinyl alcohol) (PVA) as a binding agent. The aerogel structure was constructed via the freeze-drying method and then carbon aerogels (CA) were obtained via carbonization under inert gas at 700 °C. The results showed that the CA has an amorphous structure with high porosity (> 96%). Therewithal, the adsorption capacity of the CA materials was evaluated with ciprofloxacin, a persistent antibiotic. As a consequence, it is indicated that CA1 with the precursors' ratio of cellulose:PVA (5:1) performs the highest adsorption efficiency with a maximum capacity of 99.01 mg/g. The process was determined to be chemical adsorption following the Langmuir isotherm model with the investigated initial concentration in the range of 25 − 100 mg/L for ciprofloxacin. Moreover, the electrochemical properties were determined through electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge. Resultantly, the highest capacity reached 326.51 F/g at the scanning rate of 0.005 in the potential region of -0.5 to 0.5 V, corresponding to the CA3 sample with the cellulose:PVA ratio of 15:1. Furthermore, after 1000 continuous scanning cycles, the CA3 shows insignificant changes in the GCD curve, which depicts high stability as a supercapacitor. Besides, the safety of the prepared CA in energy storage application was also confirmed via the insignificant inhibitory performance on two strains of Gram-positive and Gram-negative bacteria. The aforementioned results reveal that the CA from corn stalks is potentially applicable in environmental remediation and suitable material in supercapacitors for energy storage.

Synthesis of cellulose aerogel and its derived activated carbon as an effective adsorbent for dye treatment in water

Synthesis of cellulose aerogel and its derived activated carbon as an effective adsorbent for dye treatment in water

Sustainable fabrication of cellulose aerogel embedded with ZnO@noble metal (Ag, Au, Ag-Au) NPs for sensitive and reusable SERS application

Nanostructured materials with designable microstructure fabricated through a facile and green method are highly desired for practical applications in nanotechnology. Herein, without using any toxic reagents, flexible cellulose aerogel nanocomposites embedded with ZnO@noble metal nanoparticles (NPs) were successfully prepared from a cellulose dope. Morphology, structure, and mechanical properties of the nanocomposite were characterized. Flower-liker ZnO particles were synthesized through cellulose mineralization and it acted as a platform for efficient photocatalytic synthesis of noble metal (Ag, Au, Ag-Au) NPs. The noble metal NPs were well dispersed in the three-dimensional (3D) cellulose skeleton, resulting in abundant “hot spots” for high Surface Enhanced Raman Scattering (SERS) signal enhancement. Using rhodamine 6 G (R6G) molecules as probe molecules, the detection limits and calculated enhancement factors approached to 10−10 M and 4.8 × 107, respectively. Particularly, the photocatalytic capabilities of noble metal-semiconductor heterostructure embedded in porous aerogel made it a self-cleaned SERS substrate. There was little sensitivity loss after recycling use for 3 times. This work presented a sustainable and cost-reduction strategy to construct sensitive SERS substrate.

Electro-injection-enhanced catalytic formaldehyde degradation based on conductive MnOx cellulose aerogels at room temperature

Transition metal oxide MnOx shows great potential in catalytic formaldehyde (HCHO) pollution degradation at room temperature, but it is difficult to effectively overcome the catalyst deactivation caused by the accumulation of intermediates. Hereon, a 3D conductive aerogel catalyst with cellulose nanofibers (CNF) skeleton supported MnOx nanoflowers and carbon black (CB) was prepared by freeze-drying. Based on the aerogel catalyst (MnOx/CB/CNF), an electro-injection-enhanced catalytic oxidation (EICO) strategy was proposed for HCHO degradation by promoting the formation lattice oxygen and reactive oxygen species O* . In the dynamic test (∼15 ppm at the weight hourly space velocity (WHSV) of 600000 mL/gMnOx·h), the HCHO-to-CO2 conversion efficiency of MnOx/CB/CNF by electro-injection can be enhanced to 76.27%, which is 26.4% higher than that without electro-injection, and the corresponding dynamic efficiency did not show a decreasing trend within 72 h. This proposed EICO strategy may realize the efficient and long-term pollutant degradation at room temperature.

A novel cellulose/lignin/montmorillonite ternary hybrid aerogel for efficiently adsorptive removal of antibiotics from water

A novel fully environmental-friendly organic–inorganic ternary hybrid aerogel (LN/MMT@cellulose), composed of lignin (LN), montmorillonite (MMT), and cellulose, was designed and simply fabricated. LN/MMT@cellulose was employed for the adsorptive removal of typical antibiotic ciprofloxacin (CIP) in water. The combined MMT and LN reinforce the mechanical properties of the cellulose aerogel and notably enhance the selective adsorption capacity toward CIP in the presence of various inorganic and organic matters. LN/MMT@cellulose still presents good adsorption ability toward CIP even at the CIP concentration as low as 0.002 mmol/L in various actual water sources. With the combination of the adsorption kinetics, isotherms, and thermodynamic study as well as the various spectroscopic characterizations before and after adsorption, the mechanisms of LN/MMT@cellulose in CIP adsorption were investigated in detail. Various interactions were involved in CIP adsorption by this composite aerogel under different pH levels, causing the evident pH dependence of its adsorption capacity, specifically, the cation exchange and electrostatic attractions associated with the chelation, π-π electron donor–acceptor interaction, and the ordinary hydrogen bondings were dominant at pH < 6.0, but the complexation and negatively charged assisted hydrogen bondings played the key roles under neutral and alkaline conditions. LN/MMT@cellulose had a slight loss in adsorption ability toward CIP and sustained physicochemical structural stabilities, even after seven adsorption–deadsorption cycles. In addition to CIP, LN/MMT@cellulose could be efficiently used for the adsorptive removal of two other popular antibiotics, namely, tetracycline, and trimethoprim. The said vital characteristics of LN/MMT@cellulose confirmed it is a promising material for the adsorptive removal of antibiotics in practical water treatment.

Enhanced heterogeneous Fenton degradation of p-nitrophenol by Fe3O4 nanoparticles decorated cellulose aerogel from banana stem

Fe3O4 nanoparticles decorated on cellulose aerogel (CA) from banana stems (Fe3O4@CA) were synthesized for application in the Fenton degradation of p-nitrophenol (PNP). Cellulose aerogel extracted from raw banana stems was synthesized with kymene as a crosslinking agent and freeze-dried method. The Fe3O4@CA samples were characterized by X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS). The samples with different contents of Fe3O4 on cellulose aerogel were investigated for the degradation yield of PNP in water. The affect of the loaded content of Fe3O4 and H2O2 concentration on the PNP treatment efficiency were also investigated to suggest suitable values including the Fe3O4 catalyst content loaded on CA of 0.40 g/g and the H2O2 concentration of 5.0 g/L. As the results, Fe3O4@CA reached the removal efficiency of 87.92% in 100 mins to obey the pseudo-first kinetic model with a reaction rate constant of 0.0301 min−1. This study’s finding provides a method for creating environmentally friendly catalytic material, which might be used in green chemical engineering.

Application Progress of Cellulose Aerogel Modified by GMA

Cellulosic aerogels have attracted much attention because of their low density, high porosity and low thermal conductivity in many modified composite materials. Glycidyl methacrylate (GMA) is a new type of polymeric monomer with low cost, low toxicity, good biocompatibility, and easy chemical modification that has emerged in recent years, and it was widely used in the modification of rubber, fiber and other polymer materials. Cellulose composite aerogel, which is constructed by using GMA as a bridge to connect other materials, has rich functionality and shows great application potential in biomedicine, catalysis, adsorption and other fields. In this paper, the classification and properties of aerogels and cellulose are briefly described at first, then the synthesis methods of cellulose aerogels are introduced, and the applications of composite aerogels synthesized from cellulose modified by GMA in various fields in recent years are reviewed. This paper reviews the application of GMA-modified cellulose composite aerogels about the heavy metal and dye adsorption, biological tissues, wound dressings, drug carriers, biosensor and catalytic carriers. Finally, the future development prospect and current limitations of GMA modified cellulose aerogel are briefly introduced.

Construction of oxygen vacancy-rich ZnO@carbon nanofiber aerogels as a free-standing anode for superior lithium storage

The development of next-generation high-capacity freestanding materials as electrodes in lithium-ion batteries (LIBs) has significant potential. Here, oxygen vacancy-rich ZnO (Ov-ZnO) deposited on carbonized bacterial cellulose (CBC) aerogels is developed via in-situ uniformly growing ZIF-8-NH2 particles on CBC aerogels, followed by the hydrazine reduction and pyrolysis. The CBC serves as a free-standing skeleton to disperse and support ZIF-8-NH2 derived ZnO while the introduction of oxygen vacancies can effectively promote the internal ion/electron transfer. As a result, the obtained free-standing aerogels (Ov-ZnO@CBC) displays a reversible capacity of 710 mAh g−1 at 1 A g−1 after 1000 cycles, which is superior to ZnO@CBC without hydrazine reduction treatment. Furthermore, the assembled Li free-standing full cell using the Ov-ZnO@CBC composite as the anode and BC@LiFePO4 (BC@LFP) as the cathode exhibits an outstanding cycling performance of 150 mAh g−1 after 100 cycles at 0.1 A g−1, displaying satisfactory lithium-ion storage capability. It is noteworthy that both Ov-ZnO@CBC and BC@LFP are obtained in the form of a free-standing aerogel. This work offers a strategy to prepare high-capacity and long-cycle self-supporting aerogel-based electrodes for flexible LIBs.

Recyclable Mg-MOF-74@cellulose aerogel composites for efficient removal of heavy metals from wastewater

In this study, Mg-MOF-74, an environmentally friendly metal-organic framework material with non-toxic Mg elements as the framework centers, was loaded onto low-cost and green cellulose aerogels via an in-situ growth approach to construct the Mg-MOF-74@CA composite with a three-dimensional porous structure, overcoming the problems that Mg-MOF-74 nanoparticles tend to agglomerate and cannot be easily recovered. The removal performance of the synthesized Mg-MOF-74@CA composite towards Pb(II), Cd(II), and Cu(II) was evaluated by combining batch experiments, model fittings, and characterization analyses (SEM, XRD, FTIR, MIP, TG, and XPS). The results show that the porosity of Mg-MOF-74@CA is 84.447%. The removal of Pb(II), Cd(II), and Cu(II) by Mg-MOF-74@CA reach the equilibriums at about 5 h. And the removal of Pb(II), Cd(II), and Cu(II) by Mg-MOF-74@CA are strongly influenced by solution pH, while almost independent of ionic strength and humic acid (HA). The strong complexation of Pb(II), Cd(II), and Cu(II) with the surface sites of Mg-MOF-74@CA is the main removal mechanism. The maximum adsorption capacities of Mg-MOF-74@CA towards Pb(II), Cd(II), and Cu(II) at 298 K are 223.555, 160.033, and 74.349 mg/g, respectively. Interestingly, the selective binding order of Mg-MOF-74@CA for Pb(II), Cd(II), and Cu(II) is Cu(II)>Pb(II)>Cd(II). In summary, the Mg-MOF-74@CA composite has good application prospects in practical wastewater treatment.

Bacterial cellulose aerogel enriched in nanofibers obtained from Kombucha SCOBY byproduct

Symbiotic Culture of Bacteria and Yeast (SCOBY) pellicle is a by-product of Kombucha tea fermentation that can be a cheap and fast-growing source of cellulose. SCOBY develops a 3D cellulose membrane on the surface of Kombucha tea and since its microstructure can be chemically modified, it has promising applications in the development of biocomposites. This study presents a simple procedure to transform Kombucha SCOBY membranes into cellulose nanofiber aerogels. The protocol consisted in an alkaline purification followed by an acidic hydrolysis and lyophilization. The obtained nanofibers presented thickness than ranged principally between 50 and 110 nm, good crystallinity (90%) and thermal stability (343 ºC). The simplicity of this nanofiber aerogel protocol may contribute to the development of nano-scale materials giving higher value to this by-product that generally is composted. Furthers studies should be addressed to test this nanocellulose fibers combined with other polymers for the development of eco-friendly composites.

Super-Elastic Carbonized Mushroom Aerogel for Management of Uncontrolled Hemorrhage.

Uncontrolled hemorrhage is still the most common cause of potentially preventable death after trauma in prehospital settings. However, there rarely are hemostatic materials that can achieve safely and efficiently rapid hemostasis simultaneously. Here, new carbonized cellulose-based aerogel hemostatic material is developed for the management of noncompressible torso hemorrhage, the most intractable issue of uncontrolled hemorrhage. The carbonized cellulose aerogel is derived from the Agaricus bisporus after a series of processing, including cutting, carbonization, purification, and freeze-drying. In vitro, the carbonized cellulose aerogels with porous structure show improved hydrophilicity, good blood absorption, and coagulation ability, rapid shape recoverable ability under wet conditions. And in vivo, the carbonized aerogels show effective hemostatic ability in both small and big animal serious hemorrhage models. The amount of blood loss and the hemostatic time of carbonized aerogels are all better than the positive control group. Moreover, the mechanism studies reveal that the good hemostatic ability of the carbonized cellulose aerogel is associated with high hemoglobin binding efficiency, red blood cell absorption, and platelets absorption and activation. Together, the carbonized aerogel developed in this study could be promising for the management of uncontrolled hemorrhage.

Highly robust separation for aqueous oils enabled by balsa wood-based cellulose aerogel with intrinsic superior hydrophilicity

Owing to the strong adsorption capacity, cellulose aerogel has emerged as a promising material in the field of oil–water separation. In this study, we have taken advantage of the inherent superior hydrophilicity of balsa wood-based cellulose aerogel for the separation of various aqueous oils. A facile approach to preserve inherent hydrophilic cellulose nanofibers was achieved by removing lignin and hemicellulose fractions from natural wood, resulting in flexible cellulose aerogel with lamellar architecture. As a result, the separation efficiency of cellulose aerogel can achieve 99.97% for immiscible aqueous oils, and 98.45% even for water-in-oil emulsions. Moreover, the as-prepared cellulose aerogel exhibits remarkable mechanical properties, with stress decay of 7% after 60 compression cycles making it recycle feasible. When exposed to several complex environments including acid, alkaline and salt for a long time, the cellulose aerogel remains stable superoleophobicity with underwater oil contact angle of 153.2 ± 1.2°. Given the low operating cost, high separation efficiency and durability and stability of cellulose aerogel, this work provides a promising material for aqueous oils purification.

3D Vascular-structured Flame-retardant Cellulose-based photothermal aerogel for Solar-driven interfacial evaporation and wastewater purification

Solar-driven interfacial evaporation is recognized as a green and sustainable strategy to address the global freshwater problem. Efficient vapor generation relies on the creation of high-performance evaporators, which concentrate on improving solar energy conversion efficiency, water transport capacity and thermal localization. Herein, a functionalized cellulose aerogel with a novel three-dimensional vascular structure was designed by decorating the cellulose nanofiber with ZIF-67 and MXene (CZM3), which can be used as a solar-driven multifunctional evaporator. When exposed to 1 sun, the CZM3 aerogel demonstrated a high evaporation rate of 2.034 Kg·m−2·h−1 and an efficiency of 139.4 %, outperforming many advanced evaporators. What’s more, CZM3 aerogel maintained its stable water evaporation property after multiple test cycles. This was due to the hydrophilic vascular-like channels continuously transport water, while the photothermal materials encapsulated in CNF provide the power for water vaporization. Additionally, through the interfacial evaporation of CZM aerogel, the removal rates of salt ions (Na+, Mg2+, Ca2+ and K+) and heavy metal ions (Cu2+, Zn2+ and Cd2+) reached 98.2 %∼99.5 % and 81.6 %∼98.2 %, showing outstanding water purification ability. Contrary to the flammability of pure CNF, the peak heat release rate and total heat release of CZM3 aerogel were reduced by 75.2 % and 69.9 %, exhibiting superior fire safety. The high-performance evaporator designed in this work becomes a promising candidate material in the field of solar-driven water desalination and wastewater purification.