Aerogel Beads Research Articles

Preparation of novel PVA-SA/CS-SH aerogel beads and their efficient adsorption of U(VI)

Preparation of novel PVA-SA/CS-SH aerogel beads and their efficient adsorption of U(VI)

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II).

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

Preparation and characterization of polyethylene glycol/sodium alginate aerogel beads loaded with biogenic zinc oxide nanoparticles: potential therapeutic option for treating multidrug-resistant bacteria and cytotoxic activity

Preparation and characterization of polyethylene glycol/sodium alginate aerogel beads loaded with biogenic zinc oxide nanoparticles: potential therapeutic option for treating multidrug-resistant bacteria and cytotoxic activity

Truffle mediated preparation of bacterial culture medium and mycosynthesis of titanium oxide nanoparticles loaded with polyvinyl alcohol/sodium alginate aerogel beads for antibacterial activity

Truffle mediated preparation of bacterial culture medium and mycosynthesis of titanium oxide nanoparticles loaded with polyvinyl alcohol/sodium alginate aerogel beads for antibacterial activity

Chitosan-amidated lignin aerogel beads efficiently loaded with lanthanum hydroxide for phosphate removal from aqueous solutions

Developing phosphorus removal adsorbents with high adsorption performance and excellent structural stability remains a challenge. Herein, a chitosan (CS) - amidated lignin (AL) gel-bead adsorbent with high efficiency in immobilizing lanthanum hydroxide (La(OH)3) was fabricated via an in situ precipitation and freeze-drying strategy (abbreviated as La@ALCSx). The abundant hydroxyl and amino groups in CS promoted excellent loading of La(OH)3 on the surface and inside of the adsorbent. The introduction of lignin enhanced the structural stability of the beads along with the mass transfer efficiency. Owing to the porous structure and high La utilization, the adsorption capacity of La@ALCS2 reached 130.52 mg P g−1. Intra-sphere complexation of La(OH)3 with phosphate resulted in high adsorption selectivity of La@ALCS2. Moreover, the millimeter-sized of La@ALCS2 has favourable recoverability and maintains high adsorption performance after five adsorption-desorption cycles. Characterization analysis indicated that electrostatic attraction and ligand exchange were the main adsorption mechanisms. The excellent phosphorus removal efficiency, separation efficiency and recyclability of La@ALCSx provide a viable solution for the remediation of phosphate contaminated waters.

Impact of Weak Organic Acids as Coagulants on Tailoring the Properties of Cellulose Aerogel Beads.

Tailoring the properties of cellulose aerogel beads was investigated in the present study by using weak organic acids as coagulants. Three different weak acids were specifically chosen, acetic acid, lactic acid and citric acid. For comparative studies, a strong acid, hydrochloric acid was examined. The production of aerogel beads by conventional dropping technique was controlled and optimized for weak acids. Aerogels were characterized by density analyses, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. In common, all the aerogel beads showed interconnected nanofibrillar network, high specific surface area, high pore volume, high porosity and meso- and macroporous structure. In particular, when the weakest acid (acetic acid) was used as coagulant in the regeneration bath, the lowest shrinkage was observed. As a result, the cellulose aerogel beads produced from acetic acid showed the highest values of specific surface area (423 m2 g-1) and pore volume (3.6 cm3 g-1). The porous structure can be tuned by the choice of regeneration bath, which has either strong acid or a high concentration of weak acid. The aerogel beads were pure and showed cellulose II crystallinity. Hence this study paves an alternative path way to tailor the properties of cellulose aerogel beads.

Investigation of regeneratable biopolymer-based aerogels for heavy metal decontamination from water: Quantum chemical analysis and experimental investigation

Heavy metals pose a significant threat to human health and ecological security due to their high toxicity, mobility, and persistence in the environment. Herein, the synthesis of a novel cellulose nanofiber-based aerogel using non-toxic biopolymers such as sodium alginate and polyglutamic acid to eradicate lead, zinc, and copper from water is described. The physical characterisation and the adsorption performance of the aerogels were evaluated in both monolithic and bead configurations. The study revealed superior adsorption performance for the aerogel beads compared to the monolithic configuration. The aerogel beads achieved a maximum adsorption capacity of 171.7 mg/g, 100.0 mg/g, and 142.0 mg/g for lead, zinc, and copper respectively. The aerogel beads exhibited a higher specific surface area compared to the monolithic aerogels. The presence of functional groups including carboxyl, amino, and hydroxyl groups on the aerogels likely facilitated the adsorption through coordinate bond formation and electrostatic interactions. Density Functional Theory calculations supported the role of oxygen and nitrogen containing groups on the aerogel in capturing heavy metal ions. The aerogels displayed a remarkable regeneration ability and were reused 20 times, without any significant reduction in the adsorption performance indicating its potential as a sustainable adsorbent for heavy metals removal from water.

Cellulose aerogel beads and monoliths from CO2-based reversible ionic liquid solution

The CO2-based reversible ionic liquid solution of 1,1,3,3-tetramethylguanidine (TMG) and ethylene glycol (EG) in dimethyl sulfoxide (DMSO) after capturing CO2, (2[TMGH]+[O2COCH2CH2OCO2]2−/DMSO (χRILs = 0.1), provides a sustainable and effective platform for cellulose dissolution and homogeneous utilization. Highly porous cellulose aerogel beads and monoliths were successfully prepared via a sol-gel process by extruding cellulose solution into different coagulation baths (NaOH aqueous solution or alcohols) and exposing the cellulose solution in open environment, respectively, and followed by different drying techniques, including supercritical CO2-drying, freeze-drying and air-drying. The effect of the coagulation baths and drying protocols on the multi-scale structure of the as-prepared cellulose aerogel beads and monoliths were studied in detail, and the sol-gel transition mechanism was also studied by the solvatochromic parameters determination. High specific surface area of 252 and 207 m2/g for aerogel beads and monoliths were achieved, respectively. The potential of cellulose aerogels in dye adsorption was demonstrated.

Bioinspired 1T-MoS2-based aerogel beads for efficient freshwater harvesting in harsh environments

Freshwater scarcity is one of the most critical issues worldwide, particularly in arid regions, stemming from population growth and climate change. Inspired by the hydrophilic bump structures of desert beetles, 1T-MoS2-based aerogel beads with porous structures and CaCl2-crystal loading (termed as MoAB-m@CaCl2-n) were prepared for freshwater harvesting. Metallic-phase MoS2 nanospheres exhibit excellent photothermal conversion abilities, facilitating solar-driven water desorption and evaporation. Owing to the synergistic effect of its localized surface features, hydrophilic groups, and dispersive CaCl2 particles, MoAB-2@CaCl2-2 efficiently harvests water from atmosphere with a superior moisture adsorption capacity (0.18–0.82 g g−1) at a wide range of relative humidity (10 %-70 %). Under one-sun illumination, MoAB-2@CaCl2-2 demonstrates an outstanding solar-driven water evaporation rate of 2.25 kg m-2h−1. The water evaporation rate from soil (water content = 20 %) is 1.19 kg m-2h−1, which is sufficient for sustainable freshwater generation from the soil in arid regions. More importantly, the multifunctional MoAB-2@CaCl2-2-based homemade freshwater generation prototype delivers a certain amount of water harvesting (0.99 g g−1 day−1) on a rainy day and provides an impressive daily freshwater yield (53.7 kg m−2) under natural sunlight. The integrated device exhibits excellent efficiency and practicality and offers a feasible method for freshwater harvesting in harsh environments.

Cd-contaminated soil remediation using MgFe2O4/chitosan carbon aerogel beads

The immobilization of cadmium in soil to reduce its bioavailability is a common approach in soil remediation. However, fluctuations in soil pH, redox potential, and microbial activity can still lead to cadmium release. To address this challenge, MgFe2O4/chitosan carbon aerogel beads (MCSCA) were synthesized for in-situ remediation to remove Cd from the soil. A two-week remediation period was conducted to assess the effectiveness of MCSCA in Cd-contaminated soil. Different proportions (1%, 2%, and 3% by soil weight) of MCSCA were incorporated into the soil for remediation, followed by MCSCA separation through water flotation. The results demonstrated that after three remediation cycles, 55.46%, 72.27%, and 75.70% of the total cadmium were removed by 1%, 2%, and 3% MCSCA additions, respectively, corresponding to the removal of 76.51%, 87.39%, and 90.28% of bioavailable cadmium. Regeneration of MCSCA was accomplished using 0.1 M HCl, achieving cadmium desorption rates of 97.14%, 96.43%, and 90.48% for 1%, 2%, and 3% MCSCA additions, respectively. The regenerated MCSCA maintained higher remediation efficiency, removing 62.72%, 75.20%, and 80.96% of bioavailable cadmium even after three cycles, with MCSCA recovery rates of 94.40%, 92.30%, and 91.40%, respectively. In a pot experiment, pakchoi plants grown in soil post three rounds of remediation with different ratios (1%, 2%, and 3%) of MCSCA xhibited reductions in total cadmium content by 44.75%, 59.38%, and 69.88%, respectively, compared to plants grown in Cd-contaminated soil. In summary, this study underscores the effectiveness of MCSCA in remediating Cd-contaminated soils, offering a promising approach for soil remediation.

Efficient adsorption performance of uranium in wastewater by novel MXene material TiVCT x and its aerogel composites.

This work focuses on the application potential of novel MXene materials in the field of uranium-containing wastewater adsorption, particularly addressing gaps in existing research. Ultra-thin layered TiVCT x was selected as the core adsorbent to thoroughly investigate its adsorption performance of uranium(U(vi))-containing wastewater. By compounding with sodium alginate, we successfully prepared easily recoverable aerogel beads and evaluated their adsorption capacity for ultra-low concentrations of U(vi) in seawater. The findings of this study reveal that TiVCT x exhibits optimal adsorption capacity for U(vi) in a weakly acidic environment with a pH of 5.59, and its maximum adsorption capacity for U(vi) reaches up to 336 mg g-1, demonstrating superior performance when it comes to other MXene materials. Further research reveals that the adsorption mechanism involves the synergistic effect of electrostatic adsorption and reduction adsorption, exhibiting monolayer adsorption characteristics, and the adsorption process is a spontaneous endothermic reaction. Notably, in simulated complex seawater environments, even when the U(vi) concentration is as low as, for instance, 3.3 μg L-1, 50 mg of aerogel beads can still achieve an adsorption capacity of 3.89 mg g-1 for 60 L of seawater. These findings underscore the outstanding performance of TiVCT x as a novel MXene material in U(vi) adsorption and its broad potential for practical applications.

Functional porous protein nanofibrils/polysaccharides aerogel beads for efficient dyes removal from water

The multiple transport paths provided by the linked pore channels in CPCs aerogel facilitate the effective separation and elimination of dye molecules. Furthermore, these channels' functional groups improve their performance when they interact with particular substances.

Upcycling cellulose waste textile into aerogel beads via prilling technique

Upcycling cellulose waste textile into aerogel beads via prilling technique

Synthesis and fabrication of segregative and durable MnO2@chitosan composite aerogel beads for uranium(VI) removal from wastewater

To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO2@chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO2 nanospheres but also significantly enhances the porous structure and surface area of MnO2@CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO2@CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO2@CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO2-based adsorbents. The chemisorption process of U(VI) on MnO2@CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO2@CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater.

Polydopamine modified cerium-based MOFs/ chitosan aerogel beads for the efficient phosphate removal

The metal organic frameworks (MOFs) are considered as the effective adsorbents for phosphate removal, while their ultrafine powders limit their practical application. In this study, we fabricate two chitosan (CS) gel beads added with different cerium-based MOFs and coated with PDA for phosphate adsorption. The MOFs doped in beads are CM1 and CM2, in which the Ce(III)/Ce(IV) ratio is 0.36 and 1.46, indicating CM2 is Ce(III) dominated and more suitable for phosphate removal. However, during the process of preparing gel beads, the mixture of chitosan and CM1/CM2 are added drop-by-drop to NaOH solution, leading to the decrease of Ce(III) contents in both of the two beads on account of oxidization. On this basis, in order to improve the phosphate uptake performance and enhance the mechanical strength, polydopamine (PDA) is applied to be coated on the outside. The adsorption capacities of CS-CM1 and CS-CM2 are no more than 20 mg/g higher than that of pure CS, which is also quite equal with the phosphate uptake of CS@PDA (63 mg/g). Due to the reduction of PDA, the content of Ce(III) increasing evidently in the two adsorbents. The maximum phosphate adsorption capacities are 146.8 mg/g and 114.8 mg/g for CS-CM1@PDA and CS-CM2@PDA, respectively. CS-CM2@PDA exhibits the largest treatment volume of ∼1166 BV in the fix-bed column study, much higher than that of CS-CM1@PDA (976 BV). The main reason is that Ce(III) could form binding with phosphate through ligand exchange and precipitation. Those inner-sphere interactions are much stronger than the electrostatic attraction between Ce(IV) and phosphate. Thus, due to this strong affinity, CS-CM2@PDA possessing a higher content of Ce(III) can capture phosphate more easier at low concentration. In summary, owing to reduction of PDA, the Cerium-based MOFs are successfully introduced in CS to realize excellent phosphate removal and exhibit a great prospect in application.

Shapeable sodium alginate aerogel beads incorporated with L-cysteine-modified defective UiO-67 for heavy metal ions removal

Threats caused by heavy metal ions have prompted people to develop porous and functionalized materials to remove them. Metal–organic frameworks (MOFs) show potential for heavy metal ions removal due to the high specific surface area, tunable pore size, flexible designability and favorable stability. However, the intrinsic microporous structure and powder form limit their applications. Herein, we designed a shapeable aerogel bead incorporated with L-cysteine-modified defective UiO-67 for Pb(II), Cd(II) and Cu(II) adsorption. The pristine UiO-67 powders were firstly modified by introducing the modulator (octanoic acid) and an extra ligand (2,2′-bipyridine-5,5′-dicarboxylic acid) to construct defects, both of them competed with the original ligand to coordinate to Zr clusters, resulting in an increased BET surface area (from 337.66 to 1,037.14 m2/g) and mesoporous ratio (from 34 % to 74 %) of the pristine UiO-67. Then, the graft of L-cysteine containing –COOH and –SH introduced more active adsorption sites. Moreover, the powder material was incorporated into sodium alginate aerogel beads which enhanced the recyclability and further improved the adsorption capacity for Pb(II), Cd(II) and Cu(II). These appealing advantages endow the adsorbent with quicker adsorption equilibrium (240 min), and outstanding removal capacities for Pb(II) of 661.2 mg/g, Cd(II) of 296.2 mg/g and Cu(II) of 326.4 mg/g. The chelation and ions exchange between the numerous functional groups including –COOH, –OH and –SH and the heavy metal ions are the main mechanisms for effective adsorption. This work provided a novel approach for the application of MOFs in environmental remediation.

Novel efficient capture of hexavalent chromium by polyethyleneimine/amyloid fibrils/polyvinyl alcohol aerogel beads: Functional design, applicability, and mechanisms

The harmful effects of hexavalent chromium (Cr(VI)) on the environment and human health have aroused wide public concern. In this study, bulk spherical aerogel beads (PAP) were synthesized from polyethyleneimine (PEI), protein amyloid fibrils (AFL), and polyvinyl alcohol (PVA) through green technology and its removal of Cr(VI) from wastewater was comprehensively studied. The results showed that although the bulk PAP beads (∼ 5 mm) only had an average pore size of 16.88 nm and a BET surface area of 12 m2/g, its maximum adsorption capacity for Cr(VI) reached 121.44 mg/g (at 298 K). Cr(VI) adsorption onto PAP conformed to pseudo-second-order adsorption kinetics and was endothermic. The adsorption of Cr(VI) decreased stepwise with the increase of solution alkalinity (pH = 2: 91.97%; pH = 10: 0.04%). Importantly, PAP showed high selectivity towards Cr(VI) in mixed heavy metal solutions (Cr(VI) > Pb(II) > Ni(II) > Cu(II) > Cd(II)) and good reusability (removal efficiency > 88% after 5 cycles). PAP had excellent anti-interference ability against FA and HCO3- with the overall removal rate exceeding 87% in the presence of 5 – 25 mg/L of these ions. Cations such as Na+, Mg2+, and other heavy metal ions at high concentrations could promote the removal efficiency of Cr(VI). The removal rates of Cr(VI) and Cr(III) by PAP in a tannery wastewater were 34.4% and 59.3%, respectively. Meanwhile, the removal rates of Cr(VI) in a electroplating wastewater and a contaminated soil leachate reached 84.4∼89.7%, showing high practicability. Mechanism studies revealed that electrostatic attraction, hydrogen bonding, reduction, and complexation were the main reactions for Cr(VI) removal by PAP. In general, the study of PAP provides a new insight into using bulk monolith materials for treating Cr(VI) contaminated wastewater.

Facile synthesis of porous cellulose aerogel beads with tunable core–shell microstructures and physical properties

Cellulose aerogel beads (CABs) have emerged as advanced biomaterials with numerous engineering applications, including chromatography and drug release. In this study, porous core–shell CABs were synthesized using a dilute ethanol solution-substitution-assisted freeze-drying. The formation mechanism of the CABs and the effect of ethanol concentration on the core–shell microstructures and physical properties were investigated. Cellulose hydrogel beads (CHBs) were formed through the exchange/neutralization of acetic acid with tetraethylammonium hydroxide (TEAOH)/urea. The cellulose chains dissolved in the cellulose–TEAOH/urea droplets regenerated from the edge to the inside of the droplet in an acetic acid bath. Notably, adding ethanol at a concentration of 10% before freeze-drying can result in core–shell CABs with non-obvious structural shrinkage, large particle size, uniform pores, and high porosity. Ethanol molecules induce ice crystal growth to form more uniform ice crystals during the freezing process. Additionally, by altering the TEAOH/urea molar ratios and cellulose concentrations of cellulose solutions, well-shaped and porous CABs were prepared, demonstrating the feasibility and availability of dilute ethanol solution-assisted freeze-drying. Consequently, the as-fabricated CABs had a dense micro-shell (1–9 μm) and loose millimetric-core with anisotropic pores (2–6 μm), exhibiting low density (0.06–0.09 g/cm3), high porosity (87.0–91.5%), and noteworthy thermal stability.

Comparative Evaluation of Alginate-Gelatin Hydrogel, Cryogel, and Aerogel Beads as a Tissue Scaffold

Hydrogels are frequently used in tissue engineering and regenerative medicine, drug delivery, and environmental remediation. Alginate and gelatin, which are frequently used natural polymers to form hydrogels, were chosen in this study to form a core-shell structured hydrogel. Cryogels and aerogels were obtained by drying hydrogels with different methods, freeze-drying, and the continuous flow of supercritical CO2, respectively. The potential use of hydrogels, aerogels, and cryogels as a tissue scaffold was evaluated comparatively. Characterizations of materials were determined morphologically by scanning electron microscope and computed-micro tomography, chemically by energy dispersive spectroscopy, and mechanically by the dynamic mechanical analyzer. In addition, the cytotoxic effect of all structures was analyzed by the WST-1 method and the localization of the cells in these structures was determined by microscopic methods. All scaffolds show non-cytotoxic effects. Cryogels have the highest porosity (85.21 %) and mean pore size values (62.3±26.8 µm). Additionally, cryogels show high water retention capacity (782±53.5%) than aerogels (389±2.5%) for 24 h. The elastic modulus values were

Synergistic effect in simultaneous adsorption of cationic and anionic emerging contaminants by chitosan aerogels containing nanocellulose-modified tannic acid

Emerging contaminants (ECs) are present in the environment and can affect aquatic fauna and flora. Due to the difficulty in removing ECs from water, new technologies must be developed. Most studies report the adsorption of ECs in single systems and few works have investigated the uptake in multicomponent systems, which limits the applicability of adsorbents for real samples which usually contain different ECs. In this work, chitosan aerogel beads containing crystalline nanocellulose and modified tannic acid were synthesized and employed in the adsorption, in multicomponent systems, of the emerging contaminants VBB dye, CPC surfactant, and SC drug. The maximum removal potential in single systems was 1407, 698, and 934 mg·g−1 for VBB, CPC, and SC, respectively. The aerogels demonstrated high efficiency in the elimination of contaminants in real samples (>99 %). The CS@NC–mTA beads were able to remove the RR250 and RO122 anionic dyes in multicomponent systems, which were not adsorbed in single system, and achieved elevated removal capacities of 298 and 311 mg·g−1, respectively. In multicomponent assays with cationic contaminants, a synergistic effect was also observed, and the uptake of SC and CPC increased in 209.6 % and 40.9 % in the presence of the VBB dye. For the first time, a synergistic effect on the adsorption of cationic contaminants is reported. XPS analyses and adsorption data suggest that electrostatic, π-π, cation-exchange and H-bonds play important role in the process. These results indicate the great potential of the CS@NC–mTA beads in the water treatment for real samples.