Bio-based Aerogels Research Articles

A novel bio-aerogel based on agroforestry waste chestnut shell for enhanced oil-water separation performance

Bio-based aerogels have attracted much attention due to their biodegradability and excellent oil-water separation properties. However, the preparation of inexpensive green aerogels with high separation efficiency is still a great challenge. In this paper, low-density, high-adsorption capacity and superhydrophobic chestnut shell-based bio-aerogels were prepared by chemical cross-linking and chemical vapor deposition using agricultural and forestry waste chestnut shells as the precursor of aerogels to achieve high efficiency of oil-water separation and to achieve the goal of “treating waste with waste”. The covalent cross-linking of chestnut shell cellulose and cross-linking agent to form silicone-containing functional groups improved the pore structure, hydrophobicity and mechanical properties of chestnut shell cellulose, and under the action of capillary force, the oil was retained in the pores of the bio-aerogels, which achieved the selective adsorption of oil and organic solvents in the oil-water mixture, with a separation efficiency of more than 98%. After 10 cycles, the bio-aerogel still has good reusability. This eco-friendly and low-cost aerogel provides a practical method for resource conversion and recycling, as well as a green and innovative way for the treatment of oily wastewater.

Reversible-gel-assisted, ambient-pressure-dried, multifunctional, flame-retardant biomass aerogels with smart high-strength-elasticity transformation.

Bio-based aerogels, which are poised as compelling thermal insulators, demand intricate synthesis procedures and have limited durability under harsh conditions. The integration of smart stimuli-response transitions in biomass aerogels holds promise as a solution, yet remains a challenge. Here, we introduce a pioneering strategy that employs reversible-gel-assisted ambient-pressure drying without organic solvents to craft multifunctional bio-based aerogels. By exploiting the thermally reversible gelling propensity of select biomasses, we anchor emulsified bubbles within cross-linked hydrogels, circumventing surface tension issues during mild drying. The resultant aerogels feature a robust porous matrix that is imbued with stable bubbles, yielding low thermal conductivity, high flame retardancy and robust resistance to diverse rigors. This innovative approach facilitates a paradigm shift in intelligent fire protection in which aerogels transition from robust to flexible in response to water stimuli, effectively shielding against thermal hazards and external forces. This work opens up a facile, eco-friendly and mild way to fabricate advanced biomass aerogels with stimuli-responsive transformation.

Fire-resistant and thermal-insulating alginate aerogel with intelligent bionic armor for exceptional mechanical and fire early-warning performance

Intelligent bio-based aerogels have attracted increasing attention in several key areas due to their unique porous structure and sustainability, but they suffer from poor fire safety, strength, and durability under harsh conditions. Here, we prepared sodium alginate/hydroxyapatite/graphene oxide (SA@HAP@GO) aerogel by in-situ growth and directional assembly technology, and an intelligent “bionic armor” was put on the surface of SA aerogel. It not only endows aerogel with high strength (2.3 MPa) and long-time water resistance (30 days) but also maintains the lightweight (0.039 g cm−3) and thermal insulation properties (0.03537 W m-1K−1) of original aerogel. Under fire conditions, the compact physical barrier makes aerogel obtain the excellent fire-resistant stability and fire-safety performance. Besides, the directional assembly of GO and the chelating effect of Ca2+ on aerogel surface promote the formation of a three-dimensional electron transport network during reduction process, thus achieving a fast and long-lasting fire early-warning response (1.95 s). The corresponding mechanism was demonstrated by molecular theoretical calculation and experiments. This multifunctional aerogel provides a new way for sustainable and high-performance thermal-insulation materials and shows a wide application in energy security.

Radially and Axially Oriented Ammonium Alginate Aerogels Modified with Clay/Tannic Acid and Crosslinked with Glutaraldehyde.

Lightweight materials that combine high mechanical strength, insulation, and fire resistance are of great interest to many industries. This work explores the properties of environmentally friendly alginate aerogel composites as potential sustainable alternatives to petroleum-based materials. This study analyzes the effects of two additives (tannic acid and montmorillonite clay), the orientation that results during casting, and the crosslinking of the biopolymer with glutaraldehyde on the properties of the aerogel composites. The prepared aerogels exhibited high porosities between 90% and 97% and densities in the range of 0.059-0.191 g/cm3. Crosslinking increased the density and resulted in excellent performance under loading conditions. In combination with axial orientation, Young's modulus and yield strength reached values as high as 305 MPa·cm3/g and 7 MPa·cm3/g, respectively. Moreover, the alginate-based aerogels exhibited very low thermal conductivities, ranging from 0.038 W/m·K to 0.053 W/m·K. Compared to pristine alginate, the aerogel composites' thermal degradation rate decreased substantially, enhancing thermal stability. Although glutaraldehyde promoted combustion, the non-crosslinked aerogel composites demonstrated high fire resistance. No flame was observed in these samples under cone calorimeter radiation, and a minuscule peak of heat release of 21 kW/m2 was emitted as a result of their highly efficient graphitization and fire suppression. The combination of properties of these bio-based aerogels demonstrates their potential as substituents for their fossil-based counterparts.

Aerogels based on Bacterial Nanocellulose and their Applications.

Microbial cellulose stands out for its exceptional characteristics in the form of biofilms formed by highly interlocked fibrils, namely, bacterial nanocellulose (BNC). Concurrently, bio-based aerogels are finding uses in innovative materials owing to their lightweight, high surface area, physical, mechanical, and thermal properties. In particular, bio-based aerogels based on BNC offer significant opportunities as alternatives to synthetic or mineral counterparts. BNC aerogels are proposed for diverse applications, ranging from sensors to medical devices, as well as thermal and electroactive systems. Due to the fibrous nanostructure of BNC and the micro-porosity of BNC aerogels, these materials enable the creation of tailored and specialized designs. Herein, a comprehensive review of BNC-based aerogels, their attributes, hierarchical, and multiscale features are provided. Their potential across various disciplines is highlighted, emphasizing their biocompatibility and suitability for physical and chemical modification. BNC aerogels are shown as feasible options to advance material science and foster sustainable solutions through biotechnology.

Ultralight, elastic, hydrophobic Willow moss-derived aerogels for efficient oil-water separation

Aerogels with exceptional absorption capacity and remarkable selectivity, have generated significant interest in the scientific community as absorbents. But the utilization of aerogels has been restricted due to the expensive raw materials and the complexity of the fabrication process. Efforts to create green and cost-effective absorbents are in high demand to effectively remove oil from wastewater. Herein, the fabrication of porous lightweight bio-aerogels using Willow moss and sodium alginate (SA) is considered as an effective approach. Furthermore, following the silylation treatment, the hydrophobic aerogel maintained good mechanical stability, excellent absorption capacity, and good thermal insulation performance. These aerogels exhibited excellent mechanical properties and could effectively contribute to the control of environmental pollution caused by oil and harmful organic solvents. With its low-cost and environmentally friendly preparation process, as well as its remarkable performance, this method demonstrated significant potential in the preparation of porous bio-based aerogels.

Bio-Based Aerogels in Energy Storage Systems.

Bio-aerogels have emerged as promising materials for energy storage, providing a sustainable alternative to conventional aerogels. This review addresses their syntheses, properties, and characterization challenges for use in energy storage devices such as rechargeable batteries, supercapacitors, and fuel cells. Derived from renewable sources (such as cellulose, lignin, and chitosan), bio-based aerogels exhibit mesoporosity, high specific surface area, biocompatibility, and biodegradability, making them advantageous for environmental sustainability. Bio-based aerogels serve as electrodes and separators in energy storage systems, offering desirable properties such as high specific surface area, porosity, and good electrical conductivity, enhancing the energy density, power density, and cycle life of devices. Recent advancements highlight their potential as anode materials for lithium-ion batteries, replacing non-renewable carbon materials. Studies have shown excellent cycling stability and rate performance for bio-aerogels in supercapacitors and fuel cells. The yield properties of these materials, primarily porosity and transport phenomena, demand advanced characterization methods, and their synthesis and processing methods significantly influence their production, e.g., sol-gel and advanced drying. Bio-aerogels represent a sustainable solution for advancing energy storage technologies, despite challenges such as scalability, standardization, and cost-effectiveness. Future research aims to improve synthesis methods and explore novel applications. Bio-aerogels, in general, provide a healthier path to technological progress.

Hydrophobic Aerogels from Vinyl Polymers Derived from Radical Polymerization: Proof-of-Concept.

Hydrophilicity is one important drawback of bio-based aerogels. To overcome this issue, a novel approach for the preparation of mesoporous, water repellent aerogels is introduced, which combines synthesis of cross-linked bio-based copolymers from methacrylate copolymerizations, followed by solvent exchange and supercritical drying steps. The influence of monomers with different nonpolar ester groups (methyl, vanillin, tetrahydrofurfuryl) on textural properties and water contact angles of the dry products is assessed. Final aerogels show generally high overall porosities (≈96%), low densities (0.07-0.11gcm-3) as well as fine, mainly mesoporous networks, and specific surface areas in the range of 120-240m2g-1. Hereby, choice of the methacrylate ester groups results in differences of the resulting pore-size distributions. Water repellency tests show stable static water contact angles in the hydrophobic range (≈100°) achieved for the substrate containing the vanillin ester group. On the contrary the other substrates absorb water quickly, which indicates a decisive role of the ester group. The presented approach opens up a new pathway to bio-based aerogels with intrinsic hydrophobicity. It is suggested that the properties are tailored by the choice of the monomer structure, hence enabling further adaption and optimization of the products.

Multifunctional aerogels with thermal insulation, elasticity, and hydrophobicity derived from hemp stems

Aerogels are commonly used in the fields of thermal insulation, sound insulation, adsorption, optical devices, and electrode materials. However, traditional aerogels suffer from poor structural stability and mechanical performance. Herein, we proposed a method in extracting fibers from hemp stems to prepare hydrophobic, thermal insulating and superelastic aerogels. The suspension of bleached hemp fibers (BHF), chitosan, and methyltrimethoxysilane (MTMS) is assembled into the network structure of aerogel by freeze-drying method. Because of the cross-linking between BHF, chitosan and MTMS, the material exhibited excellent properties. The aerogel demonstrated excellent compression performance, quickly recovering even when applied with 80 % compressive strain and maintaining 80 % of its original shape after 100 compression cycles. Furthermore, the aerogels demonstrated outstanding thermal insulation property; the thermal conductivity is only 0.01873 ± 0.0004 W/m·K. In addition, the aerogel exhibited excellent hydrophobic properties, with a water contact angle of approximately 130°. The superior properties of aerogel enable it to withstand complex external environments. In this study, we aim to provide new ideas and methods for resource reuse and the preparation of bio-based aerogels.

Bio-Based Aerogels for the Removal of Heavy Metal Ions and Oils from Water: Novel Solutions for Environmental Remediation.

Contamination of the aqueous environment caused by the presence of heavy metal ions and oils is a growing concern that must be addressed to reduce their detrimental impact on living organisms and safeguard the environment. Recent efficient and environmentally friendly remediation methods for the treatment of water are based on third-generation bioaerogels as emerging applications for the removal of heavy metal ions and oils from aqueous systems. The peculiarities of these materials are various, considering their high specific surface area and low density, together with a highly porous three-dimensional structure and tunable surface chemistry. This review illustrates the recent progress in aerogels developed from cellulose and chitosan as emerging materials in water treatment. The potential of aerogel-based adsorbents for wastewater treatment is reported in terms of adsorption efficacy and reusability. Despite various gaps affecting the manufacturing and production costs of aerogels that actually limit their successful implementation in the market, the research progress suggests that bio-based aerogels are ready to be used in water-treatment applications in the near future.

Hybrid Materials of Bio-Based Aerogels for Sustainable Packaging Solutions.

This review explores the field of hybrid materials in the context of bio-based aerogels for the development of sustainable packaging solutions. Increasing global concern over environmental degradation and the growing demand for environmentally friendly alternatives to conventional packaging materials have led to a growing interest in the synthesis and application of bio-based aerogels. These aerogels, which are derived from renewable resources such as biopolymers and biomass, have unique properties such as a lightweight structure, excellent thermal insulation, and biodegradability. The manuscript addresses the innovative integration of bio-based aerogels with various other materials such as nanoparticles, polymers, and additives to improve their mechanical, barrier, and functional properties for packaging applications. It critically analyzes recent advances in hybridization strategies and highlights their impact on the overall performance and sustainability of packaging materials. In addition, the article identifies the key challenges and future prospects associated with the development and commercialization of hybrid bio-based aerogel packaging materials. The synthesis of this knowledge is intended to contribute to ongoing efforts to create environmentally friendly alternatives that address the current problems associated with conventional packaging while promoting a deeper understanding of the potential of hybrid materials for sustainable packaging solutions.

Facile construction strategy for intrinsically fire-safe and thermal-insulating bio-based chitosan aerogel

Bio-based aerogels have become a research hotspot in the emerging fields because of their remarkable biocompatibility, degradability and light weight, but their low strength and flammability limits their further application. In this study, chitosan (CS) containing flame retardant element was selected as the matrix, and a lightweight, flame retardant and thermal insulating CS aerogel was successfully prepared by the ion exchange between methylphosphonic acid (MPA) and acetic acid (HAc), and directional freeze-drying technology. The compressive strength and elastic modulus of CS@MPA aerogel were 15.2% and 8.5% higher than that of CS@HAc aerogel due to the 3D cross-linking structure between MPA and CS. Compared with CS@HAc aerogel, CA@MPA1.1 aerogel demonstrated excellent thermal insulating properties, and its thermal conductivity (25.46 mW/mK) was significantly lower than that of air (26.7 mW/mK). The introduction of MPA promoted the degradation and charring of CA@MPA aerogel, and the formation of high quality char layer efficiently exerted the barrier effect. Meanwhile, the phosphorus oxygen radicals and inert gases from the decomposition of CS@MPA aerogels effectively decreased the combustion intensity in gas phase. Therefore, the PHRR and THR of CS@MPA1.1 aerogels were decreased by 91.7% and 69.5% compared to CS@HAc aerogels. In summary, CS@MPA aerogel not only conforms to the current concept of sustainable development, but also possessed excellent thermal insulation, mechanical, and fire safety properties. It is expected to replace the traditional petrochemical-based materials, and shows broad application prospects in the fields of building insulation and energy storage.

Surfactant-Mediated Highly Conductive Cellulosic Inks for High-Resolution 3D Printing of Robust and Structured Electromagnetic Interference Shielding Aerogels.

Technological fusion of emerging three-dimensional (3D) printing of aerogels with gel processing enables the fabrication of lightweight and functional materials for diverse applications. However, 3D-printed constructs via direct ink writing for fabricating electrically conductive structured biobased aerogels suffer several limitations, including poor electrical conductivity, inferior mechanical strength, and low printing resolution. This work addresses these limitations via molecular engineering of conductive hydrogels. The hydrogel inks, namely, CNC/PEDOT-DBSA, featured a unique formulation containing well-dispersed cellulose nanocrystal decorated by a poly(3,4-ethylene dioxythiophene) (PEDOT) domain combined with dodecylbenzene sulfonic acid (DBSA). The rheological properties were precisely engineered by manipulating the solid content and the intermolecular interactions among the constituents, resulting in 3D-printed structures with excellent resolution. More importantly, the resultant aerogels following freeze-drying exhibited a high electrical conductivity (110 ± 12 S m-1), outstanding mechanical properties (Young's modulus of 6.98 MPa), and fire-resistance properties. These robust aerogels were employed to address pressing global concerns about electromagnetic pollution with a specific shielding effectiveness of 4983.4 dB cm2 g-1. Importantly, it was shown that the shielding mechanism of the 3D printed aerogels could be manipulated by their geometrical features, unraveling the undeniable role of additive manufacturing in materials design.

Bio-based aerogels for targeted enrichment of phytochemicals: Nano-cellulose molecularly imprinted aerogels for Baccatin III separation

Efficient and green targeted enrichment of phytochemicals is crucial for healthy food and medicine products. In this paper, nano-cellulose aerogels with rich network pore structure and high comparative area were combined with molecular imprinting polymer technology to innovatively prepare nano-cellulose molecularly imprinted aerogels (NCAG-MIP) for targeted enrichment of phytochemicals, NCAG-MIP could be designable by changing the different template molecules. Herein, NCAG-BacMIP was prepared for the taxanes compound baccatin III as a template molecule. Through a series of characterization and adsorption experiments, the adsorption mechanism of NCAG-BacMIP on baccatin III was analyzed, which was consistent with the adsorption pseudo-second model and the Langmuir adsorption model. The adsorption capacity of NCAG-BacMIP for targeted baccatin III reached 66.54 mg g−1 at an adsorption temperature of 30 °C and pH of 5. The selectivity coefficients were 6.66, 6.19, and 7.19 for the structural analogs paclitaxel, 10 deacetylbaccatin III, and 7-xylose-10-deacetyl-paclitaxel, respectively. In the application of baccatin III enrichment from Taxus × media Rehde extracts, the content of baccatin III increased 11.6-fold after NCAG-BacMIP treatment. The novel NCAG-BacMIP blotting different template molecules would have good potential in the selective separation of phytochemicals from plant extracts.

Effect of peptide aerogel composite on silver nanoparticles as a catalyst for electrochemical CO2 reduction

Electrochemical reduction of carbon dioxide (CO2RR) product distribution has been found to be dependent on several key factors, such as catalyst surface morphology, stability, and porosity. Metal-modified carbon-based materials have received a lot of attention in CO2RR. However, designing a highly active metal carbon catalyst for CO2RR utilizing low-cost chemical precursors remains a challenge. Here, a series of myristic acid-Phe-Phe peptide (MA-FF) aerogel materials containing graphene oxide (Gox) and Ag nanoparticles have been prepared for electrochemical CO2RR. The morphologies of the composites were studied by scanning electron microscopy (SEM), and their surface compositions were determined using X-ray photoelectron spectroscopy (XPS). While the peptide aerogel alone showed no catalytic activity for CO2 electroreduction, the addition of Ag nanoparticles results in a Faradaic efficiency (FE) of 46% for electroreduction of CO2 to CO at an overpotential of − 0.8 V vs. RHE. Incorporation of Gox in the aerogel increases the FE to 88% and allows CO2 reduction at a lower overpotential of − 0.7 V vs. RHE. Using highly porous peptide aerogels-Gox in addition to the metal active center provides an enhanced and new method for CO2 conversion using low environmental impact bio-based aerogels.

Full Bio-Based Aerogel Incorporating Lignin for Excellent Flame Retardancy, Mechanical Resistance, and Thermal Insulation

Aerogels have drawn a lot of interest as prospective insulation materials in the construction industry due to their low thermal conductivity. However, the combination of excellent mechanical properties and flame retardancy is a fundamental issue with the majority of bio-based aerogels. By utilizing the ability of the alginate solution to gel in mildly acidic environments, sodium alginate (SA)/sodium lignosulfonate (LS)/phytic acid (PA) aerogels were fabricated in a quick and facile method. To solve the issue of inorganic additives being incompatible with the bio-based substrate, we introduced lignin to it as a structural reinforcer and char-forming agent, significantly improving the mechanical strengths of the aerogels, which has increased their compressive modulus by nearly 30 times. The inclusion of lignin dramatically boosted the ability of aerogels to suppress smoke while simultaneously reducing its fire index and then providing outstanding fire resistance. A superhydrophobic flame-retardant aerogel with a water contact angle of 150° was then obtained by chemical vapor deposition of methyltrichlorosilane (MTCS), further broadening its application potential. This work offers a fresh idea for the high-value utilization of lignin, and the obtained aerogels have enormous application potential in the fields of construction and transportation.

Ultralight and shape recovery bio-based aerogel for oil-water separation

Elastic superhydrophobic aerogels have attracted significant attention to treat increasingly serious oil pollution because of their recycling performance. Using chitosan (CS) and cellulose nanofibrillated fiber (CNF) as raw materials, ultralight and elastic aerogels with the highly-oriented wavy structures were prepared by bidirectional freezing, chemical crosslinking, and chemical vapor deposition (CVD) for oil-water separation. Both the chemical crosslinking and CVD made the aerogels possess good mechanical strength at low density. The aerogel exhibited excellent shape recovery, maintaining more than 88% of its original compressive strength after 50 cycles of compression-release testing, with a high recovery rate of 96.6%. The shape memory property of the bio-based aerogels was improved with a decrease in density. The adsorption capacities of various organic solvents are more than 100 g/g, especially that of chloroform up to 232 g/g. After 10 simple and convenient adsorption-extrusion cycles, the adsorption retention rate of the aerogel can still reach 87.5%. This type of bio-based aerogel with excellent recycling performance has broad application prospects in the field of oil-water separation.

Eco-friendly synthesis of durable aerogel composites from chitosan and pineapple leaf-based cellulose for Cr(VI) removal

Chromium (VI) oxyanion is one of the most toxic contaminants in water which causes cancer and genetic mutations in humans. In this work, the bio-based aerogels are successfully synthesized from pineapple leaves (PLs) and chitosan (CS) by an effective and eco-friendly method (including homogenizing, mixing, and freeze-drying) that is feasible for mass production to manage Cr(VI) pollution. The influences of different freezing approaches (refrigerator, isotropic and anisotropic freezing), solid concentrations, and weight ratios of cellulose to chitosan on the morphology, physical parameters, and Cr(VI) adsorption of the aerogels are comprehensively investigated. The fabricated aerogels are ultra-lightweight (20–30 mg/cm3), highly porous (above 97.5%), durable (Young’s modulus of 1.8–11.7 kPa), and strongly acid resistant (below 12% of weight loss at pH 3). The difference in pore size among freezing techniques is clarified by scanning electron microscopy, suggesting that anisotropic freezing is ineffective for non-nanoprecursors. The findings show the strong influence of chitosan content and pH of the medium on Cr(VI) adsorption of the PL/CS aerogels due to the electrostatic attraction between Cr(VI) oxyanions and protonated amine groups. The theoretical Langmuir maximum Cr(VI) uptake is up to 210.6–211.4 mg/g, which is generally comparable to carbon-based and costly metal-organic framework materials. The adsorption isotherm and kinetics of the samples are appropriate to the Langmuir model and the pseudo-second-order model, respectively. Furthermore, the Cr-absorption capacity retention rates of prepared aerogel are above 75% after 6 absorbing cycles by NaOH solution. Based on the results, the product cellulose/chitosan aerogel can be considered a potential adsorbent for Cr(VI) removal.

Biomedical Applications of Polysaccharide-Based Aerogels: A Review

Abstract:Aerogels, in recent times, have become materials of extensive research due to their fascinating capabilities in different fields. High porosity, large surface area, low thermal conductivity and low density make them significant in fields such as medicine, environmental engineering, food packaging, and so on. Biodegradability, low toxicity and biocompatibility, in addition to the aforementioned properties, offered by bio-based aerogels, especially polysaccharide based aerogels, give them a huge advantage over conventional inorganic ones. Polysaccharide based aerogels synthesised from starch, cellulose, pectin, alginate, chitosan, carrageenan and agarose precursors enable sustainable developments in the biomedical, cosmetic, electronic, construction and food industries. This review focuses on the biomedical applications of polysaccharide based aerogels, with special emphasis on its implications in drug delivery, tissue engineering, medical implantable devices, wound dressing, biosensors and bio-imaging. The future perspectives of these smart materials have also been subjected to discussion.

Nanostructurally Controllable Strong Wood Aerogel toward Efficient Thermal Insulation.

Eco-friendly materials with superior thermal insulation and mechanical properties are desirable for improved energy- and space-efficiency in buildings. Cellulose aerogels with structural anisotropy could fulfill these requirements, but complex processing and high energy demand are challenges for scaling up. Here we propose a scalable, nonadditive, top-down fabrication of strong anisotropic aerogels directly from wood with excellent, near isotropic thermal insulation functions. The aerogel was obtained through cell wall dissolution and controlled precipitation in lumen, using an ionic liquid (IL) mixture comprising DMSO and a guanidinium phosphorus-based IL [MTBD][MMP]. The wood aerogel shows a unique structure with lumen filled with nanofibrils network. In situ formation of a cellulosic nanofibril network in the lumen results in specific surface areas up to 280 m2/g and high yield strengths >1.2 MPa. The highly mesoporous structure (average pore diameter ∼20 nm) of freeze-dried wood aerogels leads to low thermal conductivities in both the radial (0.037 W/mK) and axial (0.057 W/mK) directions, showing great potential as scalable thermal insulators. This synthesis route is energy efficient with high nanostructural controllability. The unique nanostructure and rare combination of strength and thermal properties set the material apart from comparable bottom-up aerogels. This nonadditive synthesis approach is believed to contribute significantly toward large-scale design and structure control of biobased aerogels.