Biomass Aerogels Research Articles

Preparation of Bio-Based Aerogel and Its Adsorption Properties for Organic Dyes.

The effective utilization of biomass and the purification of dye wastewater are urgent problems. In this study, a biomass aerogel (CaCO3@starch/polyacrylamide/TEMPO-oxidized nanocellulose, CaCO3@STA/PAM/TOCN) was prepared by combining nanocellulose with starch and introducing calcium carbonate nanoparticles, which exhibited a rich three-dimensional layered porous structure with a very light mass. Starch and nanocellulose can be grafted onto the molecular chain of acrylamide, while calcium carbonate nanopores can make the gel pore size uniform and have excellent swelling properties. Here, various factors affecting the adsorption behavior of this aerogel, such as pH, contact time, ambient temperature, and initial concentration, are investigated. From the kinetic data, it can be obtained that the adsorption process fits well with the pseudo-second-order. The Langmuir isotherm model can fit the equilibrium data well. The thermodynamic data also demonstrated the spontaneous and heat-absorbing properties of anionic and cationic dyes on CaCO3@STA/PAM/TOCN aerogels. The adsorption capacity of Congo red (CR) and methylene blue (MB) by CaCO3@STA/PAM/TOCN was 277.76 mg/g and 101.01 mg/g, respectively. Therefore, cellulose and starch-based aerogels can be considered promising adsorbents for the treatment of dye wastewater.

Preparation and characterization of flame-retardant and thermal insulating bio-based composite aerogels

Biomass aerogels have gotten a lot of attention because of their remarkable characteristics such as high porosity, low thermal conductivity, environmental friendliness, and sustainability. However, the general flammability of biomass raw materials reduces their fire safety. In this study, flame-retardant bio-based composite aerogels are proposed for building energy saving. Alginate is chosen as the basic skeleton. Noncombustible nano calcium carbonate enhances the flame retardancy of the aerogels by serving as a nano-filler. It is also a source of calcium ions to further promote the char formation of the cross-linked alginate network during thermal degradation. Moreover, boric acid is introduced into the cross-linked network to improve thermal stability and char yield. Therefore, the limiting oxygen index of the alginate–calcium carbonate (Alg-CaCO3) composite aerogels reaches up to 39.5 %. The results of thermogravimetric analysis, thermogravimetry-infrared spectrometry, and in-situ diffuse reflectance infrared Fourier transform spectroscopy demonstrate that the Alg-CaCO3 composite aerogels have a significant tendency to form char during thermal degradation. In addition, the Alg-CaCO3 composite aerogels also show high porosity (up to 92.40 %), excellent mechanical properties (compression modulus up to 0.936 MPa), and outstanding heat insulation (thermal conductivity as low as 0.031 W m−1 K−1). Furthermore, natural shells, pearls, and eggshells are adopted to substitute nano-CaCO3 for preparing fully bio-based composite aerogels, which also reflect the promotion effect of fire resistance. Such ultralight flame-retardant thermal insulation material derived from biomass has the potential to be a significant green building material.

Ambient Pressure Drying to Construct Cellulose Acetate/Benzoxazine Hybrid Aerogels with Flame Retardancy, Excellent Thermal Stability, and Superior Mechanical Strength Resistance to Cryogenic Temperature.

Cellulose aerogels are highly attractive candidates in various applications, such as thermal insulation, adsorption separation, biomedical field, and as carriers, due to their intrinsic merits of low density, high porosity, biodegradability, and renewability. However, the expensive cost of the supercritical drying process and poor mechanical properties limit their practical applications. Herein, a new method was presented to fabricate cellulose acetate/benzoxazine hybrid aerogels (CBAs) with low cost, low drying shrinkage, excellent mechanical properties under cryogenic condition (-196 °C), outstanding thermal insulation, flame retardancy, and good thermal stability by ambient pressure drying. In more detail, the weighted drying shrinkage rate of CBAs-T2 can be controlled to 6.8% (the average value along the radial and axial directions), mainly due to the enhanced skeleton, by introducing polybenzoxazine networking chains. The resultant CBAs-T2 exhibit outstanding mechanical properties at room temperature because of the presence of the polybenzoxazine hybrid in the cellulose networking system. CBAs-T2 still have good mechanical properties even after subjecting them to liquid nitrogen treatment. In addition, the optimal value of thermal conductivity (0.033 W m-1 K-1) is gained easily because of the uniform cross-linking networking structure and small pore size. A superior flame retardance of CBAs-T2 is endowed to achieve self-extinguishment after ignition, which is attributed to the presence of the aromatic ring in the backbone structure. Moreover, the good thermal stability of CBAs-T2 is attributed to the fact that polybenzoxazine components could resist the decomposition of cellulose acetate and inhibit heat release during the combustion process. Our study would provide a novel method for obtaining biomass aerogels including the cellulose-based materials system with low drying shrinkage and superior mechanical properties despite bearing a cryogenic environment by the low-cost ambient pressure drying approach.

Ternary ZIF-67/MXene/CNF aerogels for enhanced photocatalytic TBBPA degradation via peroxymonosulfate activation

The novel photocatalytic advanced oxidation catalyst, ZIF-67@MXene-TA-CNF (ZIF-67@MTC) aerogels, was prepared via introducing tannic acid-coated cellulose nanofibril (TA-CNF), two-dimensional layered MXene, and ZIF-67 into a composite aerogel network. Specially, TA assisted the crosslinking of CNF through hydrogen bonds to construct the flexible aerogel skeleton, accompanied by assembly of MXene and ZIF-67. MXene not only provided sufficient attachment sites for the anchoring of ZIF-67, but also can be used as a repository for electron transfer to facilitate the separation of photogenerated electrons and holes. In the peroxymonosulfate (PMS)/aerogels/visible light system, the SO4-, OH and 1O2 were generated, and 1O2 was the main reactive species. As a result, 99.9 % of Tetrabromobisphenol A (TBBPA) can be degraded and the total organic carbon (TOC) removal efficiency reached 81.8 % within 40 min in this system. The results might provide a new concept for the design of biomass aerogels for applications in organic pollutant removal.

Flexible curdlan-based aerogels enhanced by wood fibers with ultralow thermal conductivity

Developing flexible and lightweight materials with elevated thermal insulation performance from renewable biomass is significant for green and sustainable energy. In this work, a multifunctional biomass aerogel using wood waste as a raw material is proposed. The composite aerogel consists of curdlan as a structural framework, wood fibers and nano-hydroxyapatite as reinforcing phases. By employing thermogravimetry (TG), infrared thermal imager and thermal conductivity tester, the thermal stability and thermal insulation performance of the aerogel were evaluated. The consequent thermal conductivity reaches 30.1 × 10−3 W/(m·K). As the strength and toughness of the aerogel is improved by introducing cellulose into the matrix, it shows a maximum compressive modulus of 1.65 MPa. The hydrophobicity of the aerogel is achieved by an alkylation method and the contact angle is over 120°. This nontoxic aerogel composite with high thermal and mechanical performance indicates a potential utilization in the thermal management of food and electronic industry.

Selective adsorption and efficient degradation of oil pollution by microorganisms immobilized natural biomass aerogels with aligned channels

Efficient elimination of organic pollution from wastewater is of great importance for sustainable human development. In this paper, natural biomass of lotus root (LR) and sorghum straw (SS), which showed aligned structure after treatment, was used to prepare efficient, low-cost, selective adsorption and self-floating microbial immobilization materials by hydrophobic modification assembly for the efficient degradation of diesel. By immobilizing microorganisms in aligned structured lotus flower (ALR) and sorghum straw (ASS) aerogels, hydrophobically modifying the aerogel surfaces with SiO2/PDMS, and assembling them with polyurethane foam to form hydrophobically immobilized microbial bilayer structured self-floating composites (SA6-ALR4@SiO2/PDMS and SA6-ASS4@SiO2/PDMS), diesel in water can be selectively adsorbed for biodegradation. The kinetic and thermodynamic parameters of diesel degradation process were investigated by treating oily wastewater and the effect of different carriers on microbial tolerance under different factors (temperature, pH, degradation substrate concentration, salinity) was examined. The results showed that the different carriers were effective in the degradation of diesel. However, the rich vertical aligned channels and excellent self-floating characteristics of SA6-ALR4@SiO2/PDMS accelerated the mass transfer rate between microorganisms and pollutants, achieving a high degradation rate of 96.25% for diesel in 276 h, which was better than that of 33.06% for free microorganisms under the same conditions. The degradation of oily wastewater by immobilized microorganisms follows first order kinetics. Moreover, this degradation process is spontaneous and the ΔG value is less than 0 at different temperatures. Compared with the existing methods using natural biomass to treat oily wastewater or applying only free microorganisms for biodegradation to remove oily wastewater, these methods have the disadvantages of poor selective adsorption, easy settling and low efficiency. It has greater advantages and application potential in on-site oil spill accident treatment, and opens up an effective green channel for the purification of oily wastewater.

Covalent Cross‐Links Enable the Formation of Ambient‐Dried Biomass Aerogels through the Activation of a Triazine Derivative for Energy Storage and Generation

AbstractAerogels hold promises as lightweight replacements in various applications but are plagued by their fabrication equipment, such as supercritical dryers or lyophilizers that need to work under extreme conditions. This study presents a covalent chemistry approach to strengthen cellulose nanofibers (CNF) with carboxymethylated chitosan (CMCs) to produce aerogels by ambient drying. The cross‐linking and gelation of the CNF and CMCs solutions are triggered by a triazine derivative, 4‐(4,6‐Dimethoxy[1.3.5]triazin‐2‐yl)‐4‐methylmorpholinium chloride hydrate, to form an amide bond. This approach leads to robust hydrogels that can resist capillary force during the ambient volatilization process and are turned into aerogels by freezing, solvent thawing and exchange, and ambient drying. The lightweight aerogels exhibit desirable qualities, including superior mechanical performance, a low density of 12.0 mg cm−3, and low shrinkage of 10.1%. The presented CMCs/CNF aerogels can also serve as a helpful carrier for conductive polymer, poly (3,4‐ethylene dioxythiophene):tosylate, through in situ polymerization to demonstrate their applications. These conductive aerogels are used for high‐performance supercapacitors and moisture‐enabled electrical generators. This study provides inspiration and a reliable approach for the elaborately structural design of aerogels at ambient conditions and endows application prospects in energy storage and generation opportunities.

Konjac glucomannan/cellulose nanofibers composite aerogel supported HKUST-1 for CO2 adsorption

Biomass aerogels are attractive in various applications owing to their inherent advantages of renewability, biodegradability and eco-friendly. Herein, a novel composite aerogel of konjac glucomannan (KGM)/TEMPO-oxidized cellulose nanofibers (TOCNF)@HKUST-1 (KTA@HKUST-1) is prepared through a facile vacuum impregnation method combined with the directional freeze-drying process, which using KGM and TOCNF as raw materials. The structural analyses disclose that the KTA@HKUST-1 has a hierarchical porosity, in which HKUST-1 can provide micropores for adsorption, while the meso-/macropores from KTA act as high-speed channels to improve diffusion and mass transfer rate to transport CO2 components into the micropores of HKUST-1. The experiment results of KTA@HKUST-1-10 (KTA@H10) show that the CO2 adsorption capacity can reach 3.50 mmol·g−1 at 1 bar and 298 K, and the adsorption capacity retention rate as high as 91.43% after 7 cycles. In addition, the CO2/N2 adsorption selectivity of KTA@H10 can reach 18.42, which has an excellent potential for selective CO2 adsorption.

Shapeable amino-functionalized sodium alginate aerogel for high-performance adsorption of Cr(VI) and Cd(II): Experimental and theoretical investigations

Herein, an elastic polyethyleneimine/sodium alginate aerogel was designed by a one-step freeze-drying method. The 3D honeycomb-like structure endowed it excellent compressibility and plentiful exposed adsorption sites to accelerate Cr(VI) and Cd(II) adsorption. The adsorption processes matched the pseudo-second-order and Langmuir models, and the saturated adsorption capacity for Cr(VI) and Cd(II) was 678.67 and 464.23 mg/g, respectively. The obtained aerogel still expressed superior removal performance for Cr(VI) and Cd(II) even in the coexistent of multiple interfering factors and maintained stable adsorption capacity at least after 5 cycles. Importantly, the elastic cylindrical aerogel (∼0.59 g) could achieve dynamic filtration of industrial wastewater containing Cr(VI) and Cd(II) in fix-bed column system with corresponding effective treatment volume of 4.47 and 3.25 L, respectively. The reasonable mechanisms for the adsorption behaviors of heavy metals on the as-prepared aerogel was investigated via FTIR, XPS and Density functional theory (DFT), which could be attributed to the surface electrostatic adsorption, chelation and reduction effects. Eventually, the ecological assessment verified that eco-friendly SA/PEI aerogel had a powerful auxiliary effect on the anti-fouling growth of rice. Overall, such novel biomass aerogel adsorbent possessed great application potential and theoretical guiding significance for the purification of heavy metal wastewater.

Multifunctional biomass composite aerogel co-modified by MXene and Ag nanowires for health monitoring and synergistic antibacterial applications

Single function of biomass aerogel restricts its further development, multifunctional biomass aerogel is becoming an urgent need. In this work, multifunctional biomass composite aerogel was prepared by co-modifying MXene and Ag nanowires (AgNWs) on bacterial cellulose/chitosan (BC/CH) composite aerogel through a facile method combining physical mixture, lyophilization and electrostatic adsorption. The as-prepared BC/CH/MXene/AgNWs composite aerogel could be applied as health monitoring sensor and photo-thermal antibacterial material. As a sensor, it showed high sensitivity, short response time, and satisfactory cycling stability for health monitoring. Moreover, the composite aerogel was successfully employed to monitor various human body motions including foot movements, elbow movements, wrist movement, respiration, and throat vibration pronunciation. In addition, the composite aerogel displayed excellent photothermal conversion performance, which could be quickly heated to more than 60 °C in 60 s under NIR laser irradiation (808 nm, 0.6 W/cm2). The BC/CH/MXene/AgNWs composite aerogel showed nearly 100% sterilizing effect due to the synergistic antibacterial effect from common antibacterial role of CH/AgNWs and photo-thermal antibacterial role of MXene. The novel aerogel possesses more response characteristics and better antibacterial property than existing biomass aerogels, which may develop potential application prospect in wearable and implantable bioelectronic material for health monitoring.

Efficient flame-retardant biomass aerogel endowed with graphene oxide interconnected networks for ultrasensitive fire warning

Flame-retardant thermal insulation materials (TIMs) with a function of fire warning will play a critical role in the fields of sustainable energy saving and fire safety. Herein, we fabricated a fire-alarm aerogel based on biomass sodium alginate and hydroxyapatite, introduced with graphene oxide. This aerogel exhibits good thermal insulating properties due to its porous network. The composite aerogel displays good flame-retardant performance and can provide early fire warning detection. At room temperature, the aerogel is electrically insulating, but it switches to an electrical state when exposed to flame. The aerogel connected with an alarm light can give ultrafast response time (within 1.5 s) and sustained warning time (over 60 s) under sudden fire attacks. This modified aerogel provides a promising strategy for the functional application of TIMs.

Mechanically robust sodium alginate/cellulose nanofibers/polyethyleneimine composite aerogel for effective removal of hexavalent chromium and anionic dyes

AbstractTo improve the mechanical properties and adsorption capacity of sodium alginate aerogel (SA), cellulose nanofibers were used as reinforcing fillers, and polyethyleneimine (PEI) was used as a crosslinker to reinforce the SA aerogel. Moreover, PEI provided functional groups to adsorb Cr(VI) and anionic dyes (Congo red [CR] and Methyl orange [MO]) through electrostatic and coordination action. The biomass aerogel adsorption materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive spectroscopy, x‐ray photoelectron spectroscopy, and so on. The results showed that the maximum adsorption capacity of the composite aerogel adsorbent for Cr(VI), CR, and MO under the optimal pH value was 726.59, 2007.48, and 2253.38 mg/g, respectively. Langmuir model and quasi‐second‐order kinetics can be employed to reasonably describe the adsorption process of Cr(VI) and anionic dyes. Compared with other reported adsorption materials, this biomass composite aerogel has notable advantages such as simple preparation, economical application, high adsorption capacity, convenient recycling, and environmental.

Synthesis of GO/PAAM/iminodiacetic acid functionalized alginate aerogels with enhanced catalytic activity in oxygen reaction

Biomass aerogels have been widely studied in the catalytic field due to their advantages of environmental protection and large specific surface area. However, the amount of catalytic center of biomass aerogel is not satisfied and most biomass aerogels are fragile. Herein, the novel composite double network aerogel was prepared by polyacrylamide and iminodiacetic acid functionalized alginate.In addition, graphene oxide was introduced to enhance the mechanical and catalytic performance of the aerogels. Compared with the parental alginate aerogel, the metal cross-linked content and particle compressive strength of aerogel have been improved by 2 times and 30 times, respectively.

Fabrication of New Porous Degradable Materials and Study on Purification Effect of Sewage

In order to improve the effect of biomass aerogels on water purification, this study which based on microcapsule and biomass aerogels explores new porous ecological filler. The research finding is that this porous ecological filler have significant removal efficiency on the concentration of TP, NH3-N, and COD. The removal effect on NH3-N is especially ideal. During the ten- days water purification effect test, we find that the maximum removal rate of TP, NH3-N, and COD reached 45 percent, 59 percent and 20 percent, providing scientific theoretical support on the preparation of biomass aerogels and the application of water purification.

Ultralight Biomass Aerogels with Multifunctionality and Superelasticity Under Extreme Conditions.

Biomass aerogels are highly attractive candidates in various applications due to their intrinsic merits of high strength, high porosity, biodegradability, and renewability. However, under low-temperature harsh conditions, biomass aerogels suffer from weakened mechanical properties, become extremely brittle, and lose functionality. Herein, we report a multifunctional biomass aerogel with lamella nanostructures (∼1 μm) fabricated from cellulose nanofibers (∼200 nm) and gelatin, showing outstanding elasticity from room temperature to ultralow temperatures (repeatedly bent, twisted, or compressed in liquid nitrogen). The resultant aerogel exhibits excellent organic solvent absorption, thermal infrared stealth, and thermal insulation performance in both normal and extreme environments. Even at dry ice temperature (-78 °C), the aerogel can selectively and repeatedly absorb organic solvents in the same way as room temperature with high capacities (90-177 g/g). Excellent heat insulation and infrared stealth performances are achieved in a wide temperature range of -196 to 80 °C. Further, this aerogel combines with the advantages of ultralow density (∼6 mg/cm3), biodegradability, flame retardancy, and performance stability, making it a perfect candidate for multifunctional applications under harsh conditions. This work greatly broadens application temperature windows of biomass aerogels and sheds light on the development of mechanically robust biomass aerogels for various applications under extreme conditions.

Constructing Cellulose Diacetate Aerogels with Pearl-Necklace-like Skeleton Networking Structure.

Cellulose and its derivative aerogels have attracted much attention due to their renewable and biodegradable properties. However, the significant shrinkage in the supercritical drying process causes the relatively high thermal conductivity and low mechanical property of cellulose and its derivatives aerogels. Considering the pearl-necklace-like skeleton network of silica aerogels, which can improve thermal insulation property and mechanical property. Herein, we propose a new strategy for fabricating cellulose diacetate aerogels (CDAAs) with pearl-necklace-like skeletons by using tert-butanol (TBA) as exchange solvent after experiencing the freezing-drying course. CDAAs obtained have the low density of 0.09 g cm−3, the nanopore size in the range of 10–40 nm, the low thermal conductivity of 0.024 W m−1 K−1 at ambient conditions, and the excellent mechanical properties (0.18 MPa at 3% strain, 0.38 MPa at 5% strain). Ultimately, CDAAs with moderate mechanical property paralleled to cellulose-derived aerogels obtained from supercritical drying process are produced, only simultaneously owning the radial shrinkage of 6.2%. The facile method for fabricating CDAAs could provide a new reference for constructing cellulose/cellulose-derived aerogels and other biomass aerogels.

Fully biomass-based aerogels with ultrahigh mechanical modulus, enhanced flame retardancy, and great thermal insulation applications

Biomass-derived aerogels have received extensive attention as potential thermal management materials for energy-efficient buildings. However, it remains a huge challenge to fabricate a fully bio-based aerogel with excellent mechanical property, flame retardancy, and low thermal conductivity. Herein, we demonstrate a novel and facile strategy to manufacture a fully biomass-based aerogel from naturally abundant ammonium alginate (AL) and phytic acid (PA), in which PA acting as both flame retardant and cross-linking components constructs a strong network with AL matrix. Consequently, the resultant biomass aerogel with a low density of 0.052 g/cm 3 exhibits ultrahigh mechanical modulus (25.1 ± 3.1 MPa) and specific modulus (440.4 ± 54.4 MPa cm 3 ·g −1 ), much superior to those of biomass aerogels ever reported. Due to the existence of the uniform three-dimensional porous network, the biomass aerogels exhibit low thermal conductivity (34–38 mW/m·K) and excellent thermal insulation performances. Further, the introduction of PA endows the aerogel with high flame retardancy (limiting oxygen index value of 57%, UL-94 V-0 rating, and extremely low heat release), while the biodegradability of the materials keeps at a high level with a biodegradation rate of 91.43%. Combining with the advantages of mechanically strong property, high flame retardancy, excellent thermal insulation, and biodegradation, the aerogel of this work provides a new strategy to fabricate thermal insulation materials with high environmental safety.

Surface modification of core–shell structured ZIF-67@Cobalt coordination compound to improve the fire safety of biomass aerogel insulation materials

Biomass materials are considered to be excellent candidates to replace petroleum-based materials, but inherent flammability limits their applications. In this work, biomass aerogel (BA) was prepared by freeze-drying method from sodium alginate (SA) and polyvinyl alcohol (PVA). To improve fire safety of BAs, a core–shell structured ZIF-67@Cobalt coordination compound was successfully synthesized, which was surface functionalized by 3,5-diamino-1,2,4-triazole and 9,10-dihydro-9-oxo-10-phospho-diphenyl-10-oxide (DOPO), named as DOPO-NH2-ZIF-67. The addition of DOPO-NH2-ZIF-67 (2 wt%) outstandingly improved fire safety of BA, in contrast to neat BA, peak heat release rate, peak smoke production rate, and total smoke production were reduced by 66.6%, 85.10%, and 72.76%, respectively. Furthermore, the incorporation of ZIF-67 and its derivatives has no adverse effect on the thermal insulation performance of BA composites and significantly improved their compressive strength from 0.27 MPa to 1.76 MPa. Preparation of core–shell structured ZIFs rich in active groups furnishes a conceivable way to synthesize an effective flame retardant, and a prospective method for the fabrication of aerogel insulation materials with green and economical additive-free technology is proposed.

Microporous Fe–N4 cataysts derived from biomass aerogel for a high-performance Zn–air battery

Developing inexpensive catalysts with plentiful active sites and high surface area to accelerate the oxygen reduction reaction (ORR) is of great significance for metal–air batteries. Nevertheless, it is still a challenge to balance the content of active sites and the high surface area of catalysts, especially in a versatile and economical way. Herein, a single-atom Fe catalyst was prepared by pyrolyzing biomass aerogels that anchor iron ions through coordination reactions. With the synergistic effect of a large surface area and a high Fe content, the optimized catalyst FeNC-900-8 shows excellent ORR activity and stability. The Zn–air battery with catalyst FeNC-900-8 as the cathode delivers a high peak power density and discharge voltage. This work offers a facile strategy to develop single-atom catalysts with a high surface area and a moderate metal content for high-performance ORRs.

Acidic and alkaline gas sensitive and self-healing chitosan aerogel based on electrostatic interaction

Gas pollution is a serious problem. More attention has been paid to the detection and monitoring of toxic and harmful gases, and it is urgently needed for a sensor that could simultaneously identify and distinguish between acid and base gases. Based on the electrostatic interaction resulting from amidogen of chitosan (CS) and carboxylic groups of itaconic acid (IA), we successfully prepared a series of biomass aerogels (CS-IA aerogels) that could respond to acidic and alkaline gases with different concentrations. The acidic and alkaline gases could be easily detected and distinguished by changing the content of IA in CS-IA aerogels. Moreover, the electrostatic interactions could also endowed CS-IA aerogels with self-healing ability in the breaks at room temperature. After self-healing, CS-IA aerogels still sensitively answered to acidic and alkaline gases. CS-IA aerogels with sensitivity to acid-base gas and self-healing performance has been suggested to be promising candidates as application of multi-functional aerogels.