Superhydrophobic Aerogel Research Articles

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.

Jute-reinforced hybrid biocomposite incorporated with low thermal conductive silica aerogel for improved resistance to conductive and radiative heat

This study aims to develop jute-reinforced polypropylene composites by incorporating low-heat conductive silica aerogel for enhanced thermal performance, envisioning their utilization as heat-insulating panels in buildings. The fabrication of hybrid composites using a heat press molding technique showed a significant improvement in thermal properties due to incorporating aerogel into the material. The lowest obtained thermal conductivity of hybrid composite was 0.0986 W/m·K, which was almost halved (0.1704 W/m·K) to the material without aerogel. The radiative heat resistance of hybrid composites was also improved with the aerogel in the material. Additionally, composites with higher amounts of aerogel showed superior flame resistance and thermal stability at high temperatures. The hybrid composites, however, demonstrated a decrease in tensile strength due to the presence of aerogel particles at the interface of composites. The composite without aerogel displayed the highest tensile strength of 64.67 MPa, which was the lowest (47.87 MPa) for the material with the maximum amount of aerogel. The fractographic investigation also revealed the existence of aerogel particles and their random distribution at the interface of the material. The low water absorption owing to reduced interfacial vacuities and the existence of super-hydrophobic aerogel in the interior of composites indicated their durability in humid conditions without deteriorating the dimensional stability. The outcomes of the study revealed a considerable effect of aerogel on the thermal performance of composites and ascertained their excellence as a prospective heat-insulating material for conserving thermal energy by minimizing heat transfer from inside to outside of the building and vice versa.

Superhydrophobic Cellulose Nanofiber Aerogels for Efficient Hemostasis with Minimal Blood Loss.

Reducing unnecessary blood loss in hemostasis is a major challenge for traditional hemostatic materials due to uncontrolled blood absorption. Tuning the hydrophilic and hydrophobic properties of hemostatic materials provides a road to reduce blood loss. Here, we developed a superhydrophobic aerogel that enabled remarkably reduced blood loss. The aerogel was fabricated with polydopamine-coated and fluoroalkyl chain-modified bacterial cellulose via a directional freeze-drying method. Primarily, the hydrophobic feature prevented blood from uncontrolled absorption by the material and overflowing laterally. Additionally, the aerogel had a dense network of channels that allowed it to absorb water from blood due to the capillary effect, and fluoroalkyl chains trapped the blood cells entering the channels to form a compact barrier via hydrophobic interaction at the bottom of the aerogel, causing quick fibrin generation and blood coagulation. The animal experiments reveal that the aerogel reduced the hemostatic time by 68% and blood loss by 87 wt % compared with QuikClot combat gauze. The study demonstrates the superiority of superhydrophobic aerogels for hemostasis and provides new insights into the development of hemostatic materials.

Preparation of Halloysite-Based Superhydrophobic Aerogels for Oil–Water Separation

Preparation of Halloysite-Based Superhydrophobic Aerogels for Oil–Water Separation

Superhydrophobic cellulose-nanofiber aerogels from waste cotton stalks for superior oil–water and emulsion separation

Cellulose aerogel, a sustainable material characterized by low density and high porosity, demonstrates promising potential for addressing oil spill incidents. In this study, waste cotton stalk biomass was processed using formic acid and hydrogen peroxide to extract cellulose, resulting in the successful creation of a cost-effective aerogel. This material exhibits notable attributes: low density (21.1 mg cm−3), high porosity (91.5%), significant hydrophobicity (water contact angle of 147°), exceptional adsorption capacity (47.61 g g−1), and robust cycling performance (maintaining 94% adsorption capacity after 15 cycles). Moreover, the CNF/CS biomass aerogel boasts high mechanical strength and exceptional oil–water and emulsion separation properties. These characteristics position this aerogel as a promising solution for mitigating various sudden oil spill incidents, indicating its potential for widespread application.

Lightweight, Elastic, and Superhydrophobic Multifunctional Organic-Inorganic Fibrous Aerogels for Efficient Oily Wastewater Purification and Electromagnetic Microwave Absorption.

Lightweight and robust aerogels with multifunctionality are highly desirable to meet the technological demands of current society. Herein, we designed lightweight, elastic, and superhydrophobic multifunctional organic-inorganic fibrous hybrid aerogels which were assembled with organic aramid nanofibers and inorganic hierarchical porous carbon fibers. Thanks to the organic-inorganic fiber hybridization strategy, the optimal aerogels possessed remarkable compressibility and elasticity. Benefiting from the microscopic hierarchical porous structure of carbon fibers and the macroscopic macroporous lamellar structure of aerogels, the optimal aerogels exhibited superb lightweight property, conspicuous electromagnetic microwave absorption ability, and outstanding oily wastewater purification capacity. As for electromagnetic microwave absorption, it achieved a strong reflection loss of -41.8 dB, and the effective absorption bandwidth reached 6.86 GHz. Besides, the oil adsorption capacity for trichloromethane reached as high as 93.167 g g-1 with a capacity retention of 95.6% after 5 cycles. Meanwhile, it could act as a gravity-driven separation membrane to continuously separate trichloromethane from a trichloromethane-water mixture with a high flux of 7867.37 L·m-2·h-1, even for surfactant-stabilized water-in-n-heptane emulsions of 3794.94 L·m-2·h-1. Such a strategy might shed some light on the construction of multifunctional aerogels toward broader applications.

Superhydrophobic stereocomplex-type polylactide/ultra-fine glass fibers aerogel for passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) technology offers a green and sustainable strategy for cooling, eliminating the need for external energy sources through its exceptional efficiency in heat radiation and sunlight reflection. Despite its benefits, the widespread usage of non-biodegradable PDRC materials has unfortunately caused environmental pollution and resource wastage. Furthermore, the effectiveness of outdoor PDRC materials can be significantly diminished by rainfall. In this work, a superhydrophobic composite aerogel composed of stereocomplex-type polylactide and ultra-fine glass fiber has been successfully developed through simple physical blending and freeze-drying, which exhibits low thermal conductivity (36.26 mW m−1 K−1) and superhydrophobicity (water contact angle up to 150°). Additionally, its high solar reflectance (91.68 %) and strong infrared emissivity (93.95 %) enable it to effectively lower surface temperatures during daytime, resulting in a cooling effect of approximately 3.8 °C below the ambient temperature during the midday heat of summer, with a cooling power of 68 W/m2. This aerogel offers an environmentally friendly and sustainable approach for the utilization of radiative refrigeration materials, paving the way for environmental protection and sustainable development.

Fabrication of superhydrophobic all-biomass aerogels with ultralight, elasticity and degradability for efficient oily wastewater treatment

Oily wastewater has seriously threatened the water ecology and human health. Superhydrophobic biomass-based aerogels are ideal candidates to remedy the oily wastewater, but facing challenges for the usage of toxic small molecules crosslinker and the rational construction of elasticity. Herein, we employed the natural non-toxic citral as crosslinker, and then constructed a superhydrophobic chitosan/bamboo cellular fibers aerogel (S-CS/BCF-A) with ultra-light, high elasticity and degradation performances. Wherein the hydrolysis of methyltrichlorosilane produced silicon hydride and hydrogen chloride, enhanced the hydrophobicity of the aerogel surface and partially reduced rigidity of the pore walls, respectively. The S-CS/BCF-A displayed outstanding fatigue durability, which benefited for its lamellar-fiber interweaved structure. In addition, this aerogel could undergo tape-peeling, UV radiation, and organic solvents immersion without superhydrophobic variation, even in seriously abrasing that the surface still maintained high hydrophobicity. The as-made aerogel possessed high oil adsorption capacity (17.95–44.57 g/g), combined with pump-supported device for effectively recovering large-area oil spills (66,348 L·m−2·h−1). Furthermore, the resultant aerogel could efficiently separate the immiscible oil-water mixture and emulsifying wastewater (types of Oil-in-Water and Water-in-Oil emulsions). This work provides a rational design method for constructing the elastic, durable and biodegradable aerogels, used for speedy and economical separation of oil-water mixtures.

Superelastic, ultralight aramid fibre/tannic acid/graphene nanohybrid aerogel constructed using a cross–scale strengthening strategy for rapid and high–flux oil–water separation

Graphene-based aerogels are efficient oil–water separation materials with enormous potential, but their poor mechanical strength and cycling stability limit their applications. A cross-scale strengthening strategy was used to construct aramid fibre (A)/tannic acid (T)/graphene (G) (ATG) aerogel using an in situ electrostatic self-assembly and freeze-drying process. At 95 % of the ultimate compressive strain, the ATG aerogel could withstand a stress of up to 147 kPa and can rebound quickly. The mechanism for the high mechanical strength of the ATG aerogel was explored by structure characterisation and density functional theory (DFT) calculation. A superhydrophobic aerogel (named H-ATG) was prepared by a hydrophobic modification of ATG using a vapor deposition reaction method. The H-ATG aerogel exhibited excellent superoleophilicity/superhydrophobicity with the oil and water contact angles of 0° and 152.48°, respectively. The hydrophobicity of the H-ATG aerogel was stable over the pH range of 1–13 and the temperature range of -80–600 °C. In addition, the aerogel had an ultra-fast absorption speed and excellent absorption capability, rapidly absorbing various oil-based organic solvents up to 101 times its own weight within 5 s. After the absorption of oil or solvents, it could be easily recovered by combustion, distillation or extrusion, and the performance remained relatively unchanged after 10 cycles. When H-ATG was used as a filter to achieve fast and efficient oil–water separation with a high flux of 20,371.83 L·h−1·g−1. Therefore, the H-ATG aerogel has excellent potential for applications in the oil–water separation and the purification of oily wastewater.

Preparation of superhydrophobic cellulose aerogel sponge from waste paper and its application in oil-water separation

Preparation of superhydrophobic cellulose aerogel sponge from waste paper and its application in oil-water separation

Versatile superhydrophobic magnetic biomass aerogel for oil/water separation and removal of multi-class emerging pollutants

Water resources contamination by both oil and microplastics (MPs) stands as a pressing environmental concern. To tackle this challenge, we have devised a superhydrophobic magnetic biomass aerogel, synthesized from PDMS-modified carbonized ZIF-67/chitosan (PDMS@CZIF-67/CS). This aerogel exhibits remarkable capabilities in oil/water separation and adsorption of a wide range of emerging pollutants due to its inherent superhydrophobicity, stability, and self-cleaning capabilities. Furthermore, the aerogel demonstrates efficient absorption of viscous oils and facilitates self-driven oil absorption through the synergistic photothermal conversion and magnetic properties of CZIF-67, respectively. After ten consecutive separation cycles, the aerogel consistently maintains its efficiency in oil/water separation, regardless of the employed method, whether gravity-driven or facilitated by a peristaltic pump. Notably, the PDMS@CZIF-67/CS aerogel manifests a high adsorption capacity for various emerging pollutants, specifically MPs, achieving an almost complete adsorption efficiency. This paper introduces an innovative, eco-friendly approach aimed at mitigating oil-contaminated wastewater and emerging pollutants, highlighting its potential for widespread application.

Preparation of highly elastic superhydrophobic CNF/Fe3O4 based materials modified in aqueous phase for oil-water separation

Magnetic superhydrophobic materials have broad application prospect in oil-water separation. In this study, a magnetic and superhydrophobic aerogel with lamellar structure was successfully prepared using cellulose nanofibrils (CNF) as the skeleton, Fe3O4 as the magnetic ion, 1H, 1H, 2H, 2H trialkylfluorooctane triethoxysilane (FS) and 3-(2-aminoethyl amino)-propyl trimethoxysilane (AS) as the combined modifier. The prepared aerogel shows lower density (38.63 mg/cm3), excellent magnetic (15.13 emu/g), high elasticity and good oil sorption properties (21 g/g). In addition, FS/AS also exhibits excellent mechanical properties and superhydrophobic ability (water contact angle (WCA) of 151.9 ± 1.4°), as it provides sufficient toughness and low surface energy for the layer-branch structure. It should be noted that the entire preparation process is carried out in the aqueous phase, without the use of any organic solvents, providing a green oil-water separation strategy.

Conversion of chitosan and biomass fiber into recyclable superhydrophobic aerogel for efficient oil/water separation through a facile and green approach

Developing high performance and recyclable sorbent through a facile, low-cost, and eco-friendly way is quite important for oily wastewater treatment. Among the various fabrication approaches developed so far, the one using biomass waste as starting materials is particularly attractive in view of the cost and environmental benignity. Herein, a magnetic chitosan/typha orientalis fibers aerogel (MCS/TOFs) with excellent elasticity and superhydrophobicity was facilely prepared through freeze-drying and subsequent low-temperature annealing of biomass fibers (typha orientalis fibers, TOFs), chitosan (CS), and Fe3O4 nanoparticles. Benefiting from the 3D interconnected porous structure, superhydrophobic-lipophilic surface, and capillary effect of TOFs, the MCS/TOFs aerogel exhibited excellent sorption performance including fast sorption speed (few second to achieve saturation), high sorption capacity (up to 88.4 g/g), large flux (2.2 × 104 L m−2 h−1), and high separation efficiency (98.4%). Additionally, the MCS/TOFs aerogel can be facilely separated from the solution phase by a magnet at the end of the sorption process. After removal of the adsorbate by extrusion, the recovered MCS/TOFs can be used for next separation cycle, delivering high sorption capacity retention (> 91% of the initial capacity) after ten sorption-extrusion cycles. This work provides a facile biomass-based approach to high-performance and recyclable sorbent for oily wastewater treatment, exhibiting great potential in practical applications.

High efficiency and flux separation of water-in-oil emulsions of superhydrophobic microporous carbon aerogels

High efficiency and flux separation of water-in-oil emulsions of superhydrophobic microporous carbon aerogels

Construction of superhydrophobic silicone aerogel and its application in emulsion separation and clean water production

Human industrial activities have led to increasing pollution to the oceans and seas, resulting in significant changes in local marine environments. In this paper, an interface evaporation system based on superhydrophobic silicone aerogel and polypyrrole-fixed carbon nanotubes was developed. The water contact angle (WCA) of the superhydrophobic layer reached 160.5°, which showed good water-repellent property. Importantly, the floating layer had the effects of oil/water mixture and emulsion separation. In addition, to balance the efficient steam production flux and stability, the strategy of polypyrrole-fixed carbon nanotubes was proposed, generating the steam speed of 1.49 kg•m−2•h−1. In general, the novel evaporator enables clean steam production in the presence of salt, floating solvents and soluble dyes, achieving environmental remediation.

Highly efficient oil–water separation using superhydrophobic cellulose aerogels derived from corn straw

Highly efficient oil–water separation using superhydrophobic cellulose aerogels derived from corn straw

Bioinspired superhydrophobic polylactic acid aerogel with a tree branch structure for the removal of viscous oil spills assisted by solar energy

Inspired by the tree's distinctive structure, the G-PLA aerogel has an aligned channel. This structure has excellent photothermal conversion and vertical heat transfer capacity and can increase the oil absorption rate by 30%.

Surface modification of miscanthus fiber with hydrophobic silica aerogel for high performance bio-lightweight concrete

Bio-fiber reinforced cementitious material is now attracted widespread attention thanks to its low carbon footprint and its advantages in energy conservation in buildings. However, the main concerns of using large volume of bio-fibers in concrete is its high water absorption and the leaching of organic matter that is incompatible with cement. This study investigates a surface modification method of a bio-fiber (miscanthus) by using hydrophobic silica aerogel and further evaluates its mechanical and insulating performance in lightweight concrete and increase its compatibility with cement. X-ray diffraction, thermal gravimetry and calorimeter test were carried out to investigate the effect of hydrophobic miscanthus fibers on the microstructure of cement matrix. The results show silica aerogel modified miscanthus fiber enhances both the compressive and flexural strength, meanwhile significantly improving the insulating performance of concrete. The use of superhydrophobic aerogel particles reduces the sugar leached from miscanthus and the hydration heat peak is only slightly delayed with the incorporation of aerogel coated miscanthus fibers. The results of this study shed light on surface modifications of bio-fibers for applications in high performance construction materials.

Ultralight, superhydrophobic and fire-resistant nitrogen-doped graphene aerogel for oil/water separation

The simultaneous achievement of graphene aerogels with low density, high adsorption capacity and selectivity, as well as high mechanical strength, holds great significance but remains a challenging task. By adjusting the concentration and ratio of graphene oxide, dopamine and L-ascorbic acid, the hydrogel without obvious volume shrinkage and stability was synthesized by hydrothermal reaction at low temperature, after freeze-drying and calcination, nitrogen doped graphene aerogel (NGA) with ultralight, superhydrophobic, superoleophilic, fire-resistant, and compressible/recoverable were obtained. The density of NGA is only about 1.9 mg/cm3, and the water and oil contact angles in air are 153.3° and 0°, respectively. Given the aforementioned beneficial features, NGA can efficiently select and adsorb multifarious of oils and organic solvents in oil/water mixtures so as to achieve oil/water separation. Remarkably, NGA exhibits an impressive adsorption capacity of up to 150–305 times its own weight, and it also possesses excellent adsorption recyclability. Therefore, NGA has great potential in the treatment of oil pollution in the water environment.

Anisotropic Free-Standing Aerogels Based on Graphene/Silk for Pressure Sensing and Efficient Adsorption.

Compressible, conductive, ultralight, and superhydrophobic graphene aerogels (GAs) are promising for wearable electronics and adsorption applications. However, the unsatisfactory sensing performances and lack of multiscale structural regulation still impede the development of multifunctional GAs. Herein, a multifunctional aerogel based on graphene/silk is reported─a highly ordered three-dimensional (3D) reduced graphene oxide (rGO) conductive network is established by an alkali-induced hydrothermal self-assembly strategy, while silk fibroin (SF) bound to graphene oxide (GO) by electrostatic interactions is uniformly distributed throughout the network. The ultralight rGO/SF aerogel (GSA) has the property that its resistance varies with compression, so it can be used for flexible pressure sensors. A GSA-based sensor can detect compressive stresses down to 0.35 kPa and has a response time of 0.55 s and a recovery time of 0.58 s. It has a good linear response from 0.5 to 30 kPa with sensitivities of 0.54 kPa-1 (0.5-4 kPa) and 0.21 kPa-1 (4-30 kPa), respectively. The GSA-based sensor also has excellent durability, remaining stable after 12,000 cycles. As proof of concept, its applications for health monitoring, speech recognition, and motion capture are shown. Furthermore, the carbonized rGO/SF aerogels (C-GSAs) with superhydrophobicity can adsorb various organic substances (146.7-278.8 g/g) and achieve oil-water separation.