Cellulose Aerogels Research Articles

A Cellulose/Polyethylene Oxide Gel Polymer Electrolyte with Enhanced Mechanical Strength and High Ionic Conductivity for Lithium‐Ion Batteries

AbstractPolyethylene oxide (PEO) gel polymer electrolyte (GPE) is a promising electrolyte for rechargeable lithium‐ion batteries (LIBs). However, they still suffer from weak mechanical properties and low ionic conductivity. Herein, a novel hybrid GPE with enhanced mechanical properties and superior ionic conductivity is developed by introducing regenerated cellulose (RC) into PEO. Benefiting from the 3D porous interconnected network structure of cellulose aerogels, the obtained PEO‐RC GPEs exhibit improved mechanical strength (up to 40 MPa), increased electrolyte absorption ability, excellent ionic conductivity (4.34 × 10−3 S cm−1), and remarkable Li‐ion transfer number (0.60). As a result, a rechargeable LIB assembled with LiFePO4/GPEs/Li demonstrates a high initial discharge capacity of 149.3 mAh g−1 at 0.2 C and an impressive capacity of 141.3 mAh g−1 (94.6% capacity retention) after 100 cycles. This work provides a new route to the design and synthesis of novel GPEs toward next‐generation safe rechargeable LIBs.

Development of a facile aerogel‐based ion‐selective electrode using cellulose and carbon nanotubes as transducer materials for potentiometric application

AbstractFacile, lightweight, and sustainable aerogels have been a growing interest in their applications as support matrixes in the current environmental and energy challenges. In this study, a cellulose aerogel (CA) is fabricated using a homogeneous dispersion of cellulose fibers in an alkali‐urea aqueous solution and a carbon nanotube ink (CNT‐ink) to increase its electrical and conductive behavior in a potentiometric analysis. The physicochemical and morphological properties of the resultant composite aerogels (CA, CA1, and CA2) are investigated by thermal, water resistance, mechanical, FTIR, and SEM analysis. The prepared material exhibits a structured solid network that is visualized through SEM in which fibers are functionalized with CNTs. The results from compressive tests reveal that CA2 has excellent mechanical properties. A saturated CA with CNT‐ink can turn on a white LED and potentiometric measurements by preparing an aerogel‐based ion‐selective electrode (CA2 ‐ ISE) with a potassium ion‐selective membrane (K+ − ISM) reveal good sensitivity at room temperature for the detection in a specific electrolyte solution.

Highly transparent silanized cellulose aerogels for boosting energy efficiency of glazing in buildings

To maintain comfortable indoor conditions, buildings consume ~40% of the energy generated globally. In terms of passively isolating building interiors from cold or hot outdoors, windows and skylights are the least-efficient parts of the building envelope because achieving simultaneously high transparency and thermal insulation of glazing remains a challenge. Here we describe highly transparent aerogels fabricated from cellulose, an Earth-abundant biopolymer, by utilizing approaches such as colloidal self assembly and procedures compatible with roll-to-roll processing. The aerogels have visible-range light transmission of 97–99% (better than glass), haze of ~1% and thermal conductivity lower than that of still air. These lightweight materials can be used as panes inside multi-pane insulating glass units and to retrofit existing windows. We demonstrate how aerogels boost energy efficiency and may enable advanced technical solutions for insulating glass units, skylights, daylighting and facade glazing, potentially increasing the role of glazing in building envelopes.

Influence of the cellulose purification process on the properties of aerogels obtained from rice straw

Cellulose aerogels were obtained from purified rice straw cellulose fibres (CF) by applying different extraction methods: the conventional alkaline treatment (ALK) and alternative aqueous extraction based on the ultrasound combined with reflux heating (USHT) and subcritical water extraction (SWE) (160 and 180 °C). The composition and properties of the CFs were significantly affected by the purification process. The USHT treatment was as efficient as the ALK at eliminating the silica content, but the fibres maintained a notable ratio of hemicellulose (∼16 %). The SWE treatments were not so effective at removing silica (15 %) but greatly promoted the selective extraction of hemicellulose, especially at 180 °C (3 %). The CF compositional differences affected their hydrogel formation capacity and the properties of aerogels. A higher hemicellulose content in the CF led to better-structured hydrogels with better water-holding capacity, while the aerogels exhibited a more cohesive structure with thicker walls, higher porosity (99 %) and water vapour sorption capacity, but lower liquid water retention capacity (0.2 g/g). The residual silica content also interfered with the hydrogel and aerogel formation, giving rise to less structured hydrogels and more fibrous aerogels, with lower porosity (97–98 %).

Enhanced Mechanical Stability and Hydrophobicity of Cellulose Aerogels via Quantitative Doping of Nano-Lignin.

As a porous biomass sustainable material, cellulose aerogel has attracted significant attention due to its unique properties in various applications. However, its mechanical stability and hydrophobicity are huge obstacles hindering practical applications. In this work, nano-lignin quantitative doping cellulose nanofiber aerogel was successfully fabricated via liquid nitrogen freeze drying combing vacuum oven drying. The impact of various parameters (lignin content, temperature, and matrix concentration) on the property of the as-prepared materials was systematically explored, revealing the optimum conditions. The morphology, mechanical properties, internal structure, and thermal degradation of the as-prepared aerogels were characterized by various methods (compression test, contact angle, SEM, BET, DSC, and TGA). Compared with pure cellulose aerogel, the addition of nano-lignin did not significantly change the pore size and specific surface area of the material but could improve its thermal stability. In particular, the enhanced mechanical stable and hydrophobic properties of cellulose aerogel via the quantitative doping of nano-lignin was confirmed. The mechanical compressive strength of 160-13.5 C/L-aerogel is as high as 0.913 MPa, while the contact angle was nearly reaching 90°. Significantly, this study provides a new strategy for constructing a novel cellulose nanofiber aerogel with mechanical stability and hydrophobicity.

Interactions of cellulose cryogels and aerogels with water and oil: Structure-function relationships

Food-grade porous materials, aerogels and so-called cryogels, were prepared from cellulose hydrogels obtained from solutions at increasing cellulose concentration (3, 4, 5%, w/w) by supercritical-CO2-drying (SCD) and freeze-drying (FD), respectively. The structure depended on the applied drying technique, with aerogels showing a denser network with pores <200 nm in diameter, a specific surface area of 370–380 m2g-1, and a porosity of 92–94%. Cryogels presented larger pores (2–5 μm diameter), much lower specific surface area (around 30 m2g-1), and higher porosity (95–96%). Water vapor adsorption by aerogels and cryogels was higher than that of neat microcrystalline cellulose. The absorption of water and oil was investigated as a function of time and at equilibrium. While water was almost immediately absorbed by both aerogels and cryogels, a much longer time was needed to reach oil absorption equilibrium. Moreover, aerogels required a longer absorption time than cryogels. Material morphology governed the kinetics of absorption; the absorption at equilibrium was directly dependent on material pore volume rather than on its morphology or material-fluid affinity. As a result, due to their lower pore volume, aerogels absorbed a lower amount of water or oil (4–8 gfluid/gdry matter) than cryogels (8–12 gfluid/gdry matter). All samples showed high fluid holding capacity (>96%). Water absorption caused a firmness decrease, but the firmness of oil-filled materials was the same as that of the unloaded ones. This study demonstrates that food-grade cellulose aerogels and cryogels can be structurally designed by varying cellulose concentration and drying techniques to obtain controlled food fluid loading.

A polydiacetylene-based smart cellulose aerogel functionalized by ZnO/MoS2 heterojunction for simultaneous visual detection and photocatalytic degradation of gaseous VOCs

The integration of visual detection and degradation of volatile organic compounds (VOCs) is greatly desired for addressing ever-growing environmental problems. Herein, a chemically cross-linked cellulose aerogel is explored as substrate material, combing with ZIF-8/MoS2 derived 2D ZnO/MoS2 heterojunction. Then polydiacetylene (PDA) was self-assembled on the aerogel via topochemical polymerization to obtain a smart gas sensing and eliminating hybrid aerogel (PZMCA) with high porosity (>96%). The intrinsic stimulate responsiveness and the flower-like hierarchical structure of PDA contributed to a sensitive and fast color response to gaseous toluene with 10 s. Moreover, by regulating the mass ratio of ZnO and MoS2, the PZMCA presented enhanced photocatalytic ability for toluene (97% of degradation efficiency with 180 min) under solar light irradiation. GC-MS reveals the possible mechanism and pathway of the photocatalytic degradation of toluene. The robust, uniform, versatile and functional aerogels could hopefully provide practical applications in VOCs detection and photocatalytic degradation.

Controlled fabrication of the biomass cellulose aerogel@ZIF-8 nanocomposite as efficient and recyclable adsorbents for methylene blue removal

Design and fabrication of outstanding adsorbents for treating organic pollutants in wastewater following green chemistry principles remain huge challenging. In this paper, a biomass cellulose [email protected] ([email protected]) based on bamboo leaves cellulose aerogel (CA) was controllable synthesized and used for the removal of methylene blue (MB) from aqueous solution. CA was prepared from bamboo leaves by NaOH/ urea low temperature dissolution method and freeze-drying method, and then ZIF-8 was grown in situ on its surface, successfully preparing [email protected] composite with three-dimensional porous structure. The tests of X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structures of materials, and the related results showed that arsenic was successfully adsorbed by the prepared [email protected] The influences of pH (2−12), contact time (5–180 min), temperature (298 K, 308 K, 318 K) and other factors on MB adsorption quantity were studied in the adsorption experiments, and the maximum adsorption capacity was about 90.18 mg/g at 298 K. The adsorption thermodynamics showed that the adsorption process of [email protected] to MB was spontaneous and decreased with the increase of temperature. The possible adsorption mechanism was also suggested. The [email protected] exhibited good reusability that the removal of MB remained above 77.25 % after 5 cycles. The above results show that [email protected] is a economically and proficient suitable material for removing MB from wastewater.

Filtration Capacity and Radiation Cooling of Cellulose Aerogel Derived from Natural Regenerated Cellulose Fibers

ABSTRACT Natural cellulosic materials are attractive biopolymers for their naturally abundant source, mechanical toughness, bioactivity, etc. However, porosity and flexibility remain challenges for the preparation of aerogels from natural cellulose. To maintain the characteristics of cellulose aerogels possessing the toughness of fibers and high porosity of aerogels, cellulose aerogels with three-dimensional void structures and high compressive resilience were prepared by mixing cellulose fiber suspension and polyvinyl alcohol (PVA). The PM 2.5 removal rate and thermal conductivity of cellulose aerogel reached 92.4% and 0.028 W/mK, respectively, when a PVA content of 0.7% was added, and the radiation cooling temperature was about 10.0°C lower than that of PE foam. The three-dimensional void structure and surface morphology of the cellulose aerogels were investigated by scanning electron microscopy (SEM). The cellulose aerogel porosity and pore size distribution were evaluated by a mercury intrusion meter. The crystal structure of cellulose was analyzed by X-ray diffraction (XRD). UV-Vis-NIR spectroscopy was used to investigate the infrared reflectance of cellulose aerogels. Then the air purification efficiency and radiation cooling effect of porous cellulose aerogels were evaluated in a homemade device, respectively.

A nano-structured bilayer asymmetric wettability textile for efficient personal thermal and moisture management in high-temperature environments

In recent years, climate change has led to extremely hot weather conditions in many parts of the world, which not only causes large amount of energy consumption for building space cooling, but also poses a great threat to the health and safety of people outdoors. A wearable textile that could simultaneously maximizing thermal insulation, facilitating evaporative cooling, and enhancing radiative cooling would play an important role for outdoor personal thermal and moisture management in high-temperature environments. However, developing such a textile with a relatively simple structure remains a huge challenge. Herein, a bilayer asymmetric wettability cooling membrane (BAWCM) textile composed of banana trees cellulose aerogel membrane (BTCAM) and thermoplastic polyurethane nanofibers doped with zinc oxide nanoparticles (ZnO-NPs/TPU) is prepared by freeze-drying and subsequent electrospinning. The BAWCM textile has good thermal insulation performance, thereby reducing heat input when the ambient temperature is higher than the human body temperature. Meanwhile, the textile possesses a high reflectance of 91.3 % in the 0.37–2.5 μm wavelength range and an infrared emissivity of 90.2 % in the 8–13 μm wavelength range. In outdoor test, it is demonstrated that the BAWCM textile can be as large as 9.3 °C cooler than cotton under direct sunlight. More importantly, the textile can effectively achieve directional perspiration to accelerate evaporative cooling, preventing sticky and hot sensation. Through the integration of excellent thermal insulation, enhanced radiative cooling, and continuous sweat wicking-drying capability, this novel textile exhibits significantly improved personal thermal and moisture management performances in high-temperature environments.

Highly efficient construction of sustainable bacterial cellulose aerogels with boosting PM filter efficiency by tuning functional group

Air pollution has become a major public health concern, attracting considerable attention from researchers working on environmentally friendly and sustainable materials. In this work, bacterial cellulose (BC) derived aerogels were fabricated by the directional ice-templated method and used as filters to remove PM particles. We modified the surface functional groups of BC aerogel with reactive silane precursors, and investigated the interfacial and structural properties of those aerogels. The results show that BC-derived aerogels have excellent compressive elasticity, and their directional growth orientation inside the structure significantly reduced pressure drop. Moreover, the BC-derived filters exhibit an exceptional quantitative removal effect on fine particulate matter, which, in the presence of high concentrations of fine particulate matter, they can achieve a high-efficiency removal standard of 95 %. Meanwhile, the BC-derived aerogels showed superior biodegradation performance in the soil burial test. These results paved the way for BC-derived aerogels development as a great sustainable alternative to treat air pollution.

Facile Preparation of Cellulose Aerogels with Controllable Pore Structure.

Cellulose aerogels are the latest generation of aerogels and have also received extensive attention due to their renewable and biocompatible properties. Herein, cellulose aerogel was facilely prepared by using NaOH/urea solution as solvent, raising the temperature to control gelation and drying wet gel sequentially. With NaOH/urea solution as solvent, the cellulose concentration has an important impact on the micromorphology of cellulose aerogels, while the aging time rarely affects the micromorphology. The appropriate solvent and drying method allow the formation of different cellulose crystalline structures. Different from the Cellulose Ⅰ crystalline structure of raw cellulose powder, the cellulose phase of as-prepared cellulose aerogels belongs to the Cellulose Ⅱ crystalline structure, and to some extent the pyrolysis temperature is also lower than that of raw cellulose powder. The resultant cellulose aerogel prepared by using NaOH/urea solution as solvent and freeze-drying has a uniform macroporous structure with a macropore size of 1~3 µm.

In situ growth of UiO-66-NH2 in wood-derived cellulose for iodine adsorption.

The capture of radioactive iodine is an inevitable requirement in nuclear industry for environmental protection. Metal-organic frameworks (MOFs) are a new generation of sorbents that have wide applications for iodine adsorption and recovery. Although the loading of MOFs on wood can avoid the drawbacks of the powder form of MOFs in implementation, the dense structure of wood results in the lower loading, even after delignification, which limits the adsorption capacity. Herein, a hierarchically porous UiO-66-NH2 @WCA composite was fabricated by in-situ synthesis of UiO-66-NH2 in wood-derived cellulose aerogel (WCA) that was further removed hemicellulose from delignified wood. UiO-66-NH2 @WCA exhibited a high loading (36wt%) of UiO-66-NH2 crystals and a high adsorption capacity of 704mg/g for iodine vapor and 248mg/g for iodine aqueous solution. The adsorption behavior in iodine aqueous solution was well predicted by the Freundlich isotherm and pseudo-second-order kinetic model. The adsorption capacity of UiO-66-NH2 @WCA was highest in solution when the pH was 6, while the ionic strength had little effect. The hydroxyl groups on the WCA matrix had a charge transfer effect with iodine, providing additional sites for iodine capture. Furthermore, a packed column system was applied to demonstrate the excellent recyclability and potential for practical application.

Effect of multi-wall carbon nanotubes/strontium ferrite nanoparticles on the microstructure, phase, magnetic and electromagnetic behavior of carbon aerogel composites

This research examined the electromagnetic behavior of a carbon aerogel composite containing multi-wall carbon nanotubes and strontium ferrite nanoparticles within the X band range (8.12–2.4 GHz). For this purpose, 10 wt% of carbon nanotubes and 5 wt%, 10 wt%, and 15 wt% of strontium ferrite nanoparticles were applied in the pyrolyzed cellulose aerogel composite. For structural and magnetic characterization of the samples, different techniques such as X-ray diffraction test, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, vector network analyzer, and vibrational magnetometer (VSM) were used. The VSM results indicated that the presence of 10 wt% strontium ferrite nanoparticles in the carbon aerogel substrate caused saturation magnetization of 2.31 emu/g. However, upon adding 10 wt% carbon nanotubes, the saturation magnetization value reached 6.82 emu/g. Based on the results, the greatest shielding efficiency (within the X-band = 110 ± 0.8 dB) occurred in the sample containing 10 wt% carbon nanotube alongside 5 wt% strontium ferrite at thicknesses of 4 mm. Furthermore, the reflection loss value of this sample was −48.59 ± 0.5 dB at a thickness of 3 cm and a frequency of 10.92 GHz.

Functional cellulose aerogel nanocomposites with enhanced adsorption capability and excellent photocatalytic performance

A novel functional cellulose carbon aerogel@Na2Ti3O7@Cu2O (CA@Na2Ti3O7@Cu2O) nanocomposite was prepared by in situ growth technique and impregnation method, and its photocatalytic and adsorption properties were explored. The cationic intercalation structure of Na2Ti3O7 nanosheets gives CA@Na2Ti3O7@Cu2O nanocomposites excellent adsorption capacity of heavy metal ions (31.0–118.7 mg/g). The Cu2O nanoparticles in CA@Na2Ti3O7@Cu2O nanocomposite showed excellent photocatalytic activity, and the removal rate of methylene blue (MB) was up to 99 %. Furthermore, the CA@Na2Ti3O7@Cu2O nanocomposites could be easily regenerated and reused, providing a new way to effectively solve the problem of wastewater treatment containing heavy metal ions and organic dyes.

Hydrophobic and magnetic fabrication of hydroxyethyl cellulose-lignin aerogel through ultrasound enhancement for efficient oil/water separation

Oil leakage has caused great damage to the marine aquatic environment. Cellulose aerogels can be used to separate oil/water mixture, but the low strength and recyclability have restricted its application. In order to improve the performance of cellulose-based aerogels, hydrophobic and magnetic modification with ultrasound enhancement was carried out. Firstly, hydroxyethyl cellulose-lignin aerogel (CL-aerogel) was synthesized by combining hydroxyethyl cellulose with lignin through sol–gel method with freeze-drying. The incorporation of lignin endowed the aerogel with a 3D porous network and enhanced mechanical properties. Then CL-aerogel was modified with n-dodecyl mercaptan (NDM) and Fe3O4 NPs through ultrasound enhancement to obtain HMCL-aerogel. The results disclosed that with the increase in NDM usage and ultrasound time, the hydrophobicity and magnetic responsiveness of aerogel was enhanced. Furthermore, HMCL-aerogel had good oil absorption capacity with high selectivity. The HMCL-aerogel could be easily recycled by an external magnetic field and could be reused through a simple extrusion treatment. Meanwhile, the aerogel exhibited effective separation of oil/water mixture with a flux as high as 2986 L‧m−2‧h−1 even in corrosive conditions and maintained over 99 % separation efficiency after 10 separation cycles. Therefore, the hydrophobic and magnetic hydroxyethyl cellulose-lignin aerogel could potentially serve as an intriguing candidate for practical oil-polluted wastewater remediation.

Preparation of high elastic bacterial cellulose aerogel through thermochemical vapor deposition catalyzed by solid acid for oil-water separation

Oil pollution has caused more and more serious damages to the environment, especially to water. Oil and water separation technologies based on high-performance absorbing materials have attracted extensive attentions. Herein, elasticity-enhanced bacterial cellulose (BC) aerogel is synthesized for oil/water separation through thermochemical vapor deposition (CVD) catalyzed by 1, 2, 3, 4-butanetetracarboxylic acid (BTCA). BTCA has two functions, namely, esterification with BC and catalyzing CVD. The prepared aerogel could be recovered soon after being compressed and the elastic recovery was >90 % at set maximum deformation of 80 %. And, it also exhibits vigorous fatigue resistance with an elastic deformation of >80 % after 50 cycles. The high elastic and hydrophobic aerogel is very suitable for absorbing and desorbing oils by simple mechanical squeezing. The adsorption capacity for n-hexane and dichloroethane maintain 87 % and 81 % after 50 cycles, respectively, which implies robust reusability. Importantly, the CVD could also be catalyzed by other solid acids such as citric acid and vitamin C. This design and fabrication method offers a novel avenue for the preparation of hydrophobic bacterial cellulose aerogel with high elasticity.

Encapsulating covalent organic frameworks (COFs) in cellulose aerogels for efficient iodine uptake

Efficient capture and storage of radioiodine are of great importance for developing nuclear energy and tackling nuclear waste, which however remain challenging due to the scarcity of powerful materials. In this work, we rationally design and fabricate a hybrid material by encapsulating covalent organic frameworks (COFs) into ultralight cellulose aerogels for efficient iodine (I2) capture. Two kinds of functionalized cellulose precursors that can be covalently cross-linked are synthesized. Solvothermally synthesized COF particles with a uniform diameter of ∼ 500 nm are then introduced into the precursors followed by freeze drying to produce hybrid aerogels. With the presence of rich and ordered micropores afforded by COFs, these highly porous aerogels exhibit excellent organic solvent absorption performances and high uptake capacities toward solvent-dissolved and vaporized I2. More importantly, in view of the processable and robust structure, we realize the shaping of hybrid aerogels into aerogel columns to effectively capture I2 vapor and I2 solute in continuous operations. Therefore, this work not only provides a new way to shape COF materials but also could inspire the design of viable platforms for high-performance I2 capture.

An ultralight aerogel-type urea absorbent for the development of a wearable artificial kidney

Cellulose aerogel is used for urea adsorption for the first time, and displays a fast adsorption rate and high adsorption capacity.

Treatment of Water Containing Dyes Using Cellulose Aerogels

Abstract In recent years, there has been an interest in the study of new methods for the removal of dyes from water due to its large-scale use in different industries, for example, for paper printing, textile, leather, pharmaceutical, food or technological applications. It is estimated that more than 700 thousand tons of about 10 000 different types of dyes are produced annually. Most of them are synthetic origin and can generate adverse effects, for example, teratogenic, mutagenic and carcinogenic action. Dyes are mainly applied in the textile industry, and they are usually classified into anionic (acid dyes), cationic (basic dyes) and non-ionic (disperse dyes) dyes. The direct discharge of dyes into the environment can cause various damages to plants and animals: dyes can block the penetration of sunlight, reduce the photosynthetic efficiency of aquatic plants and ultimately destroy the ecological balance of the aquatic ecosystem. This study determined the adsorption efficiency of congo red, methylene blue, rhodamine B and naphthol green B dyes used in textile industry by using the aerogel – an adsorbent synthesized from paper waste. Total carbon was selected as indicator of dye concentration in solution. An increase in fibre content from 3 % to 5 % contributes to the improvement of adsorption properties. The decrease in congo red concentration after an adsorption process was 31.0 % and 38.0 % respectively; the decrease in methylene blue was 2.49 % and 8.15 %; the decrease in naphthol green B was 28.04 % and 34.14 % and the decrease in rhodamine B was 1.28 % and 4.13 %.