Cellulose Aerogels Research Articles

Preparation of lamellar-structured carboxymethyl cellulose aerogels for efficient sound absorption

Preparation of lamellar-structured carboxymethyl cellulose aerogels for efficient sound absorption

Amino-Functionalized Metal–Organic Framework-Mediated Cellulose Aerogels for Efficient Cr(VI) Reduction

Industrialization activities have increased the discharge of wastewater that is polluted with hexavalent chromium (Cr(VI)), posing risks to ecosystems and humans. The photocatalytic reduction of Cr(VI) is viewed as a promising method for the removal of Cr(VI) species. However, developing photocatalysts with the desired catalytic activity, recyclability, and reusability remains a challenge. Herein, a composite aerogel was designed and fabricated with a Ti-based metal–organic framework (MIL-125-NH2) and carboxylated nanocellulose. MIL-125-NH2 presents a strong visible-light response, and the interactions between the amino groups of MIL-125-NH2 and the carboxyl groups of cellulose produce a strong interface affinity in the composites. The as-prepared aerogels exhibited a micro/macroporous structure. At an optimal MIL-125-NH2 loading of 55 wt%, the MC-5 sample showed a specific surface area of 582 m2·g−1. MC-5 achieved a photocatalytic Cr(VI) removal efficiency of 99.8%. Meanwhile, the aerogel-type photocatalysts demonstrated good stability and recycling ability, as MC-5 maintained a removal rate of 82% after 10 cycles. This work sheds light on the preparation of novel photocatalysts with three-dimensional structures for environmental remediation.

Preparation and adsorption properties of polyetherimide graft-reinforced cellulose aerogels

Preparation and adsorption properties of polyetherimide graft-reinforced cellulose aerogels

Enhanced CO2 Capture and Utilization through Chemically and Physically Dual-Modified Amino Cellulose Aerogels Integrated with Microalgae-Immobilized Hydrogels

Enhanced CO₂ Capture and Utilization through Chemically and Physically Dual-Modified Amino Cellulose Aerogels Integrated with Microalgae-Immobilized Hydrogels

Ultralight Poly(vinyl alcohol)/Cattail Fiber Cellulose Aerogels as Green and Recyclable Organic Liquid Captors

Ultralight Poly(vinyl alcohol)/Cattail Fiber Cellulose Aerogels as Green and Recyclable Organic Liquid Captors

Preparation of phosphorus-nitrogen synergistic flame retardant cellulose composite aerogel from waste cotton/phytic acid/acrylamide

Cellulose aerogel is a green and biodegradable material, but the high flammability of cellulose aerogel hinders its development. In order to expand the application range of cellulose aerogel, it is necessary to improve the flame retardancy of cellulose aerogel. In this paper, cellulose hydrogels were prepared by decolorizing waste cotton fabrics (WCF) and dissolving them in 1-butyl-3-methylimidazole chloride salt ([Bmim]Cl)/DMSO. The cellulose hydrogels were impregnated in aqueous phytic acid (PA)/acrylamide (AM) solution for a period of time and then heated and treated. A cellulose composite aerogel with excellent flame retardant properties was successfully prepared by using in situ polymerization. The results show that the cellulose composite aerogel has a porous structure and good thermal stability, and the residual carbon content in the air at 800 °C is >2.86 %. At the same time, it has excellent flame retardancy, the ultimate oxygen index (LOL) is >40, and the vertical combustion carbon length is <3.5 cm. The thermal insulation performance has also been improved, and the composite aerogel with a height of 1 cm has a temperature difference of 40.2 °C between the upper and lower surfaces on the 80 °C heating table.

A capillary effect-inspired sponge-structured carboxymethyl cellulose aerogel layer-modified membrane for efficient separation of dye/salt under ultra-low-pressure

A capillary effect-inspired sponge-structured carboxymethyl cellulose aerogel layer-modified membrane for efficient separation of dye/salt under ultra-low-pressure

Upcycling Industrial Biomass Wastes Into Aerogels Using Zinc Chloride Salt Hydrates

AbstractEnd‐of‐life paper products, including food packages and rejected fibers from the paper industry, are unrecyclable biomass wastes and thus generally landfilled or incinerated. One of the major obstacles to their recycling is the existence of impurities besides cellulose fiber in the biomass wastes. In this study, a fabrication method is investigated to upcycle biomass wastes directly into high‐performance aerogels without separation of impurities. Surprisingly, this study observes that residual impurities participate in cross‐linking reactions for the aerogel formation. In this study, zinc chloride salt hydrate is applied to convert biomass wastes to aerogel via a dissolution‐regeneration process. The fabricated aerogels exhibited high water absorption capacity (15 times its weight), as well as comparable mechanical strength and thermal insulation performance to the reported cellulose aerogels. In addition, the impurities (i.e., calcium‐based inorganic salt) assisted in the cross‐linking of the cellulose network for the aerogel formation. The scanning electron microscopy (SEM) image of the aerogel generated from the rejected fibers showed a honeycomb inner structure. The rejected fiber aerogels also demonstrated a high compressive modulus of 51 MPa and a low thermal conductivity of 0.029 W m−1 K−1. The results for water absorption and thermal insulation suggest excellent potential across various application domains.

Ultralight Cellulose-Derived Carbon Nanofibers from Freeze-Drying Emulsion Towards Superior Microwave Absorption

Carbon nanofibers (CNFs) are usually prepared by the carbonization of cellulose aerogels obtained from freeze-drying. However, cellulose with low concentration (below 1 wt%) is required to maintain the good porosity of the aerogels due to the strong hydrogen bonding between the cellulose molecules. In order to address this problem, here, ultralight cellulose-derived CNFs have been fabricated by freeze-drying cyclohexane (CHE)/cellulose nanofiber emulsions and carbonization. Field emission scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are used to characterize the resulting CNFs. It is found that the CNFs consist of three-dimensional carbon networks, whose microstructure is easily adjusted by changing the CHE ratio (from 0 to 25 vol%) in the emulsions. The CNFs with high porosity are attributed to the fact that CHE as the oil phase can effectively weaken the hydrogen bonding and reduce the aggregation of the cellulose nanofibers. Carbon lattice defects and residual oxygen-containing functional groups are regarded as polarization centers, leading to the enhancement of dielectric loss. The conductive carbon networks also improve the conductive loss. All these factors improve the microwave absorption performance of the CNFs. So, the produced CNFs exhibit a superior electromagnetic wave performance with a minimum reflection loss of −42.18 dB and effective absorption bandwidth up to 4.9 GHz at 2 mm with a filling ratio of 2 wt%. This work provides a simple, low-cost, and sustainable synthesis route for CNFs used for ultralight high-performance microwave absorption materials.

Lightweight, ultrahigh-strength and flame-retardant cellulose aerogel crosslinked with a reactive P/N-rich curdlan derivative

Cellulose aerogel, recognized for its eco-friendliness, bio-sustainability and excellent thermal insulation property, holds immense potential as an insulation material. However, the application of cellulose aerogel has been hindered by its inherent drawbacks, particularly its low strength and flammability. In this study, a reactive P/N-rich curdlan derivative (NT) was synthesized and characterized. Lightweight, ultrahigh-strength and flame-retardant composite aerogels were then prepared by slow freezing, freeze-drying and chemical crosslinking methods. Composite aerogel crosslinked with 30% NT exhibited exceptional thermal insulation property with a low thermal conductivity of 33.9 mW/(m·K), which rivaled the value of petroleum-based thermal insulation materials. It possessed an ultrahigh compressive modulus (0.786 MPa) at low density (21.6 mg/cm3), which supported >12,000 times its weight. It also displayed superior flame-retardant property, with a limiting oxygen index of up to 33.1% and a V-0 rating in the UL-94 test. This study provides a new insight into the high-value utilization of natural polysaccharide and an innovative solution to the problem of low strength and flammability of cellulose aerogel. Cellulose aerogels with ultrahigh strength, superior flame retardancy and thermal insulation property possess a promising application in the fields of construction, aerospace and thermal protective clothing as high-performance thermal insulation materials.

Reusable superhydrophobic fluorinated cellulose-graphene composite aerogels for selective oil absorption

Although some progress had been made in the adsorption of graphene aerogels, more research was needed on their elasticity and recyclability. In this paper, a superhydrophobic fluorinated cellulose and graphene composite aerogel (FCGA) was prepared by a simple two-step impregnation method. Firstly, nano-cellulose was introduced into the graphene aerogel to inhibit the excessive accumulation of graphene lamellae and increase the specific surface area. The surface of the composite aerogel was then impregnated with silanol and fluorinated functional groups by a two-step impregnation method, resulting in a superhydrophobic aerogel with remarkable elasticity. The introduction of cellulose and silane provided the aerogel with excellent elasticity and recovery from cyclic adsorption. The successful grafting of the fluorophobic groups of PFDMS onto the graphene oxide strengthened the framework of the graphene aerogel, making FCGA a good candidate for repeated selective oil absorption. It could be restored to the original height after compression to 50% and 80% strain decompression. FCGA could efficiently absorb oil in water and had a high organic adsorption capacity. And the adsorption capacity of different oils/organic solvents reached 22,480 mg/g∼36,700 mg/g. Its absorption efficiency remained above 98.5% under distillation cycles. Due to its high elasticity, it retained more than 90% of its cyclic adsorption capacity through the squeeze cycle. As a simple, low-cost recovery method, its reusability was already better than most known adsorption elastic materials. The prepared composite aerogel had the advantages of simple preparation, low density (0.014 g/cm3), superhydrophobicity (water contact angle 153.3°), excellent adsorption properties, and recyclability. Therefore, FCGA had a very promising application in circulating selective oil absorption.

Bacterial cellulose/polyethylene glycol composite aerogel with incorporated graphene and metal oxides for VOCs detection

It is important to monitor and detect volatile organic compounds (VOCs) for environmental protection, occupational safety and human health. Portable and compact VOC sensing devices with a fast response are needed for real-time monitoring and simple analysis. Using solvent exchange and freeze-drying techniques, an ultralight 3D bacterial cellulose (BC) aerogel is prepared and modified by polyethylene glycol with the functionalization of graphene and metal oxides to detect VOC gases. Unlike commercially available flat VOC sensors, the 3D structure of our VOC sensor with high permeability of BC composite provides superior sensing characteristics for acetone, formaldehyde and ethanol in a wider range of scenarios. The portable BC composite sensor exhibits remarkable sensitivity and selectivity toward VOCs detection. The BC composite with TiO2 has a response time of about 20 s to 1 ppm acetone and can detect as low as 1.43 ppm at room temperature. In addition, BC composites with ZnO are suitable for detecting formaldehyde in indoor air.

A 3D aerogel evaporator for efficient solar interfacial evaporation: Breaking through the upper limit of steam production rate

Solar desalination is the most effective way to obtain clean and cheap fresh water. However, its lower upper limit of steam production rate limits its development and practical applications. In this paper, a microcrystalline cellulose aerogel composite Mo2C evaporator (MCAM) was prepared by combining Mo2C with microcrystalline cellulose aerogel (MCA). The evaporator consists of MCAM photothermal layer, polyurethane (PU) sponge insulation layer and one-dimensional water channel. Mo2C has high-light absorption efficiency. At the same time, the vertical channel inside the MCA makes the incident light be reflected and absorbed for many times inside. Benefiting from the synergistic effect of the vertical channel of MCA and the light absorption ability of Mo2C, MCAM obtained a high light absorption efficiency of 96.96 %. The interaction between the MCAM evaporator and water can reduce the evaporation enthalpy, thereby breaking the upper limit of the steam generation rate. Therefore, the evaporator achieved a steam production rate of 1.92 kg⋅m−2⋅h−1 and an energy utilization efficiency of 118.2 %. In addition, MCAM shows excellent salt tolerance and self-discharging salt ability, which ensures its stable operation in high-salinity environment. Besides its high efficiency, MCAM has significant purification effect on simulated seawater, heavy metal wastewater, and organic wastewater. This study provides a new strategy for further improving the steam production rate of the solar interface evaporator.

Low cost Non freeze-drying construction strategy of cellulose aerogels for efficient solar desalination

Aerogel-like materials with three-dimensional pore structures show great potential in the field of efficient solar-driven interfacial evaporation by virtue of their fast water transport as well as efficient energy confinement properties. However, the preparation of aerogels is currently limited by high-cost strategies such as freeze drying or supercritical drying. Here, we present a foam template-assisted (FTA) strategy for atmospheric pressure drying of cellulose nanofiber (CNF) aerogels. Building a robust CNF network is the key to resisting surface tension during water evaporation and achieving drying in ambient environments, which is achieved through cleverly designed ionic cross-linking with the help of FTA. Cellulose aerogel (CA) constructed using the FTA strategy exhibit lightweight (9 mg cm−3) and porous properties (porosity: > 99 %). The tannic-coated CA (TCA) was achieved by further polymerizing tannic acid on the CA surface, which has excellent photothermal conversion capability. Meanwhile, TCA achieved an impressive evaporation rate of 3.58 kg m-2h−1 and an energy efficiency of 97.2 % at 1sun radiation by virtue of its excellent energy confinement and water management capabilities. This strategy provides a promising solution for the low-cost construction of aerogels as well as for the realization of efficient solar-driven interfacial evaporators.

Wood derived conductive aerogel with ultrahigh specific surface area and exceptional mechanical flexibility for pressure sensing

Conductive nanocellulose aerogels possess durability and sensitivity by using as piezoresistive sensors. Those aerogels are mostly prepared via a “bottom-up” strategy by using nanocellulose or dissolved and regenerated cellulose as raw materials. However, there is a pressing need to further enhance their sustainability and economic viability. To alleviate these issues, cellulose aerogel can alternatively be made via a “top-down” technique that entails the direct removal of contaminants from naturally porous biomass. Herein, conductive aerogels with exceptional mechanical flexibility and ultrahigh specific surface area were created. Delignified wood was partially dissolved and regenerated to created nanocellulose fibrils with spider web structure inside the pores of wood. After modification with silane coupling agent and Carbon Nanotubes (CNTs), flexible conductive wood aerogel (C-WA) were obtained. The specific surface area of C-WA was as high as 333.82 m2/g, which was 45 times of that of wood. C-WA could maintain its good resilience even after 1000 cycles, showing high compression resilience and excellent fatigue resistance (stress retention rate was 87.22 %, height retention rate was 99.5 %). The utilization of C-WA as a pressure sensor demonstrated remarkable attributes, including ultra-fast response and stability within the designated range. Furthermore, it exhibited exceptional sensing performance even after enduring 2000 stable cycles. The system is capable of real-time, accurate, and efficient detection of human motion signals, showcasing immense potential for future applications in wearable electronic products.

Effect of supercritical CO2 drying variables and gel composition on the textural properties of cellulose aerogels

Cellulose aerogels are interesting platforms for biomedical and drug delivery applications, due to their biocompatibility, biodegradability, water absorption capacity, and good textural properties. Supercritical CO2 drying has been proven as an efficient technology for obtaining aerogels and preserving the porous structure. In this work, the effect of relevant process variables (CO2 density, depressurization rate, and intermediate depressurization mode) and gel composition on the textural properties of cellulose aerogels is studied. Experiments are performed in batch-mode, and aerogel monoliths are characterized in terms of apparent density, porosity, specific surface area, and crystalline morphology. Water uptake in different buffer solutions is also evaluated. The use of thiourea in the gel formation leads to lower porosity. On the other hand, higher porosity and surface area are obtained when depressurization is slow and the system is only partially depressurized between drying cycles. Aerogels showed a good and fast water uptake capacity, regardless of the pH (200–500 %).

Amine-impregnated cellulose aerogels prepared from old corrugated containers: Microstructure characterization and CO2 capture performance

Here, five different amines (MEA, DETA, TEPA, PEI, and PEPA) were immobilized onto a mesoporous cellulose aerogels (CAs) support prepared from old corrugated containers (OCCs) using the impregnation method, and the thermal stabilities, pore structures, and CO2 adsorption capacities of the resulting amine loaded materials were investigated. The results showed that the thermal stabilities and pore textures of the materials decreased relative to the unmodified CAs support. Additionally, the addition of high molecular weight amines improved the thermal stability of the resulting materials, in the order of PEI>PEPA>TEPA>DETA>MEA. The adsorption capacities of the five Amine40@CAs materials tested ranged from 111.76 to 62.48 mg.g−1 and were in the order of DETA>PEI>MEA>TEPA>PEPA. Considering both thermal stability and CO2 adsorption capacity, PEI is the most suitable for physical immobilization in the CAs support. Consequently, the sample loaded with 30 % PEI exhibits a maximum CO2 capture capacity of 136.84 mg.g−1 material. However, a loading above 30 % results in pore blockage due to amine infiltration into the pore structure, leading to a decrease in the specific surface area and hence the CO2 adsorption capacity. This indicates that there is a balance to be struck between amine loading and CO2 uptake in the solid amine adsorbents using the physical impregnation method, and it is necessary to choose an appropriate method for improving the pore structure in order to maximize the amine loading and thus enhance the CO2 capture capacity.

Biomass microcrystalline cellulose based solar evaporator with aligned channels for clean water and electricity co-generation

Solar-driven interfacial evaporation co-generation (SDIE-CG) technology can effectively solve problems such as low latent heat utilization in the evaporation process, which provides a reliable solution to the problem of hydropower shortage in remote areas. Herein, we report a tea residue microcrystalline cellulose (TMCC) aerogel (abbreviated as TCA), in which TMCC is regenerated by dissolution through the co-solvent method, and microcrystalline cellulose is rearranged by the directional slow freezing technique to get a TCA with a directional aligned pore structure, resulting in a good mechanical and salt-resistant property. Due to the internal doping of carbon black particles, the TCA has an average ultra-high absorbance of 97.46 %. The evaporation rate of TCA is up to 3.066 kg m−2h−1 under 3 kW m−2 illuminations. The maximum output voltage of the TCA is 44.801 mV under 2 kW m−2 illuminations through the introduction of a suitable wind-assisted hydropower generation device. In addition, the TCA can effectively purify the wastewater containing traditional Chinese medicine, and the chemical oxygen demand (COD) value in wastewater shows a significant decrease after treatment. It is worth noting that TCA can maintain structural integrity and stable evaporation performance in saltwater under extreme pH conditions (2<pH<11), and has potential application value in water treatment and cogeneration.

In-situ bioprocessing of bacterial cellulose aerogel with covalent organic frameworks for enhanced uranium extraction

Developing efficient and cost-effective uranium adsorbents remain a significant challenge due to the complex composition of seawater. Herein, this study for the first time utilized an in-situ spray gel-assisted biosynthesis strategy to homogeneously incorporate the covalent organic frameworks (COF) into the three-dimensional pores of bacterial cellulose (BC) hydrogel during the culture of K. sucrofermentans. The BCCOF-SO3NH4 aerogel was fabricated through ammoniating modification of BC/COF (BCCOF-SO3H) hydrogel and freeze-drying processes. The BCCOF-SO3NH4 aerogels are characterized by the in-situ entanglement of COF within the three-dimensional network of BC, resulting in enhanced mechanical strength and groups interactions. The experimental maximum adsorption capacity of BCCOF-SO3NH4 aerogel reached 883.44 mg g−1, demonstrating exceptional uranium adsorption capacity compared with most of the reported adsorbents. The adsorption process follows the pseudo-second-order model and Langmuir isotherm. Throughout seven adsorption–desorption cycles, BCCOF-SO3NH4 maintained a stable adsorption capacity and desorption efficiency. The adsorption mechanism is verified by experiments and DFT calculations, which involves not only the ion exchange between uranyl and NH4+, but also the strong coordination interaction between the active groups (sulfonic acid group, hydroxyl group) and uranium. The in-situ biosynthesis strategy of composites shows a great application prospect in the preparation of high adsorption performance materials.

Enhanced buoyancy and propulsion in 3D printed swimming micro-robots based on a hydrophobic nano-fibrillated cellulose aerogel and porous lead-free piezoelectric ceramics

This paper provides the first demonstration of additively manufactured swimming micro-robots which combine a hydrophobic nanofibrillated cellulose aerogel, to provide long-term buoyancy, with a low acoustic impedance porous piezoelectric ceramic for improved propulsion. The hydrophobic nanocellulose aerogel is shown to exhibit a high and stable contact angle that was maintained for extended periods of time, which facilitates long-term and stable buoyancy of the micro-robot. To quantify the benefits of introducing porosity into the active piezoelectric element, a new analysis model was developed to inform material design and maximize the acoustic propulsion force. Detailed characterisation and modelling of the swimming robots demonstrated that a swimming robot based on a lead-free porous Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic exhibited a higher acoustic radiation propulsion force and a faster swimming speed compared to a robot fabricated using a dense ceramic element. These benefits were associated with the lower elastic modulus, density and acoustic impedance of the porous piezoelectric material. The lower dielectric constant, reduced device capacitance, and lower resonant frequency of the porous piezoelectric element also significantly reduced the driving current and power requirements of the robot. This work therefore provides new insights on the impact of hydrophobic and acoustically matched piezoelectric materials on the performance of swimming micro-robots, and successfully demonstrates the use of porosity to improve acoustic impedance matching of resonant piezoelectric devices, such as micro-robots and ultrasonic transducers.