Aerogel Beads Research Articles

Circular utilization of Co(II) adsorbed composites for efficient organic pollutants degradation by transforming into Co/N-doped carbonaceous catalyst

Abstract Resource recovery and environmental remediation serve to meet the scientific and technical challenges of cost-effective and sustainable strategy, especially for circular utilization of valuable metal and treatment of various wastewater (toxic metal ions, organics, etc.). Encouragingly, the research on circular utilization of recovered valuable metals in peroxymonosulfate (PMS) activation for pollutants degradation is currently in blank; herein, a multistage utilization process for preparing Co/N-doped carbonaceous catalyst is plausibly proposed for the first time. Namely, by using a cheap and abundant alginate as a self-generating 3D network precursor, the interior/exterior modified aerogel beads (denoted as Ca–Me/SA@0.75PEI) are fabricated via a simple sol-gel assembly for toxic metals removal or valuable metals recovery, following that Co2+ adsorbed composite (denoted as Ca–Me/SA@0.75PEI-Co) are converted into Co/N-doped carbonaceous catalyst (denoted as Ca-NC@0.75PEI-Co-700) by carbonization. Increased surface chelating sites and polarity with abundant functional components (N = 15.68%) bring strong affinity to metal ions via ion-exchange, complexation and electrostatic interactions. Detailed isotherms, kinetics and dynamic studies illuminate the high adsorption capacity (698.62 mg/g), fast adsorption rate and long-term operation stability of Ca–Me/SA@0.75PEI adsorbent toward Co2+, respectively. Of particular interest of is that, the catalyst evolved from Co2+ adsorbed composite exhibits relatively-superior catalytic ability towards utilizing PMS oxidant to degrade organic pollutants. Animatingly, the simulation of real water system makes it potential for the multistage utilization of composites in actual industrial wastewater treatment. The coupling of watermelon-like structure and Co/N co-doping endows the adsorptive catalyst sustainable utilization capacity in heterogeneous catalysis based on the concept of “utilizing waste treating waste” circular economy, avoiding the problem of insufficient stability of ion adsorbed aerogel catalyst in PMS homogeneous catalysis.

Graphene Oxide Aerogel Beads Filled with Phase Change Material for Latent Heat Storage and Release

Phase change composite materials (PCCMs) with large latent heat capacity, a stable structure, and efficient thermal response have high potential for thermal management in various applications. Herein, novel reduced graphene oxide aerogel beads (rGOABs) are synthesized by wet spinning of GO slurry followed by thermal reduction, which are infiltrated with 1-tetradecanol (TD) paraffin as phase change materials (PCMs) to produce rGOAB/TD composites. An exceptionally high mass fraction, 98.8%, of paraffin TD encapsulated in the rGOABs is achieved in this study, which is known to be the highest among studies ever reported. It is demonstrated that the rGOAB/TD composite possesses a high latent heat value of 230.3 J g–1 and maintains 96.6% efficiency after 50 heating–cooling cycles, making the composite PCM suitable for emerging thermal management applications. The thermal responsive tests of various samples indicate better thermal response of rGOAB/TD than GOAB/TD without thermal reduction or the expanded graphi...

Design of Aerogels, Cryogels and Xerogels of Alginate: Effect of Molecular Weight, Gelation Conditions and Drying Method on Particles' Micromeritics.

Processing and shaping of dried gels are of interest in several fields like alginate aerogel beads used as highly porous and nanostructured particles in biomedical applications. The physicochemical properties of the alginate source, the solvent used in the gelation solution and the gel drying method are key parameters influencing the characteristics of the resulting dried gels. In this work, dried gel beads in the form of xerogels, cryogels or aerogels were prepared from alginates of different molecular weights (120 and 180 kDa) and concentrations (1.25, 1.50, 2.0 and 2.25% (w/v)) using different gelation conditions (aqueous and ethanolic CaCl2 solutions) and drying methods (supercritical drying, freeze-drying and oven drying) to obtain particles with a broad range of physicochemical and textural properties. The stability of physicochemical properties of alginate aerogels under storage conditions of 25 °C and 65% relative humidity (ICH-climatic zone II) during 1 and 3 months was studied. Results showed significant effects of the studied processing parameters on the resulting alginate dried gel properties. Stability studies showed small variations in aerogels weight and specific surface area after 3 months of storage, especially, in the case of aerogels produced with medium molecular weight alginate.

Rational fabrication of chitosan/alginate/silica ternary aerogel beads adsorbent with free separation

Novel chitosan/alginate/silica ternary aerogel beads were successfully prepared by the orifice-coagulation bath with the ambient pressure drying method and utilising chitosan, sodium alginate, and tetraethoxysilane as the initial raw materials. The morphologies, porosity characteristics, and dye absorbencies of the ternary aerogel beads were also investigated, respectively. The obtained samples are milky light solid, the size of the spherical aerogel is uniform, its diameter can be controlled ~5 mm, the specific surface area is 169.4 m 2 g -1 , pore size distribution is concentrated in the 2-100 nm, which is a typical nanofilamentous network structure. Meanwhile, the ternary beads were tested for dyestuffs adsorption; the results showed that the obtained samples exhibit excellent adsorption properties, and can keep good sphericity as a class of novel adsorbents.

High-efficacy adsorption of Cr(VI) and anionic dyes onto β-cyclodextrin/chitosan/hexamethylenetetramine aerogel beads with task-specific, integrated components.

To significantly enhance the adsorption efficacy of hexavalent chromium from aqueous medium, a novel and non-toxic chitosan-based composite beads were prepared by integrating task-specific components into one sample, namely β-cyclodextrin/chitosan/hexamethylenetetramine (β-CD-CS@HMTA). The pseudo- second-order kinetic and Langmuir isotherm model was used to describe the adsorption process. The maximum capacity Cr(VI) removal reached 333.8 mg/g which was superior to most of reported CS derivative adsorbents. The sorption mechanism of composite was investigated by employing FT-IR, SEM-EDS and XPS techniques. It showed that the reason for efficient removal of Cr(VI) onto resultant sample including chemisorption and reduction of Cr(VI) to the non-toxic Cr(III), and the two components of β-CD and HMTA with task-specific had played a crucial role during the adsorption process. Most importantly, for fixed-bed column sorption testing, the breakthrough curves were well fitted by Thomas model under different flow rates (1, 2 and 3 mL/min). Moreover, the β-CD-CS@HMTA had also manifested perfect adsorption capability towards anionic dyes in initial concentration 500 mg/L. This research indicated that as-fabricated chitosan-based composite beads are promising adsorbents for Cr(VI) and anionic dyes because of its superiority of low-cost, easy regeneration and environmental friendly.

Novel onion-like graphene aerogel beads for efficient solar vapor generation under non-concentrated illumination

Onion-like shaped graphene aerogel beads have been prepared via a scalable approach for efficient and easy-to-apply water purification and desalination.

Construction of blood compatible chitin/graphene oxide composite aerogel beads for the adsorption of bilirubin

Excess bilirubin in blood can provoke hepatic damage and related malfunctions. Hereby we designed and constructed a novel bilirubin adsorbent, called chitin/graphene oxide (Ch/GO) composite aerogel beads, for efficient, fast and safe removal for bilirubin. The Ch/GO aerogel beads were prepared from chitin and GO in a NaOH/urea aqueous solution, followed dried by supercritical carbon dioxide. The morphology, structure and properties of the Ch/GO composite aerogel beads were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and compressive strength measurement. The results indicated that GO was successfully bound to chitin matrix with enhanced surface area, thermal stability and mechanical strength. The adsorption capacity of Ch/GO composite aerogel beads for bilirubin was examined by UV–vis spectrophotometry. Moreover, batch adsorption results revealed that the Ch/GO composite aerogel beads showed excellent bilirubin adsorption capacity (484.1 ± 16.9 mg/g) and short adsorption equilibrium time (0.5 h) under optimized condition. Furthermore, the Ch/GO aerogel beads exhibited a lower hemolysis property and improved anticoagulant property. Hence, this work provided a new strategy to develop a novel blood compatible bilirubin adsorbent, which presented good application potential for bilirubin adsorption.

Vancomycin-loaded chitosan aerogel particles for chronic wound applications

Chronic wounds are a prevailing cause of decreased quality of life, being microbial burden a factor hindering the normal wound healing process. Aerogels are nanostructured materials with large surface area (>250 m2/g) and high porosity (>96%). In this work, vancomycin-loaded chitosan aerogel beads were tested as a potential formulation to treat and prevent infections at the wound site. Processing of chitosan in the form of aerogels endowed this polysaccharide with enhanced water sorption capacity and air permeability. The morphological and textural properties of the particles were studied by image and N2 adsorption-desorption analysis and scanning electron microscopy. Vancomycin content and release profiles from aerogel carriers showed a fast drug release that permitted to efficiently achieve local therapeutic levels. Cell studies with fibroblasts and antimicrobial tests against S. aureus showed that the vancomycin-loaded aerogel particles were cytocompatible and effective in preventing high bacterial loads at the wound site.

Highly porous zirconium-crosslinked graphene oxide/alginate aerogel beads for enhanced phosphate removal

The decontamination of excessive phosphate by Zr-based nanomaterials has attracted great attention. However, the insufficient phosphate sorption capacities and separation difficulties significantly restrict the potential applications. Herein, the newly designed zirconium-crosslinked graphene oxide/alginate (Zr-GO/Alg) aerogel beads were synthesized through a facile in situ crosslinking method, and their phosphate uptake performance were examined in the aqueous environment under different conditions. Characterization results showed that the incorporation of GO endowed the composite beads with a more porous and reinforced structure. The maximum sorption capacity was 189.06 mg P/g and the isotherm data were well fitted to the Freundlich model. Fixed-bed column experiments showed a large throughput of ∼1050 BV, with phosphate concentration of effluents lower than 0.5 mg/L. Apart from the remarkable phosphate uptake performance, the fast adsorption rate at initial stage as well as easy separation feature of Zr-GO/Alg aerogel beads rendered them to become promising and environmental-friendly adsorbentfor phosphate uptake from polluted water.

Millimeter-Size Spherical Polyurea Aerogel Beads with Narrow Size Distribution.

We report the room temperature synthesis of spherical millimeter-size polyurea (PUA) aerogel beads. Wet-gels of said beads were obtained by dripping a propylene carbonate solution of an aliphatic triisocyanate based on isocyanurate nodes into a mixture of ethylenediamine and heavy mineral oil. Drying the resulting wet spherical gels with supercritical fluid (SCF) CO2 afforded spherical aerogel beads with a mean diameter of 2.7 mm, and a narrow size distribution (full width at half maximum: 0.4 mm). Spherical PUA aerogel beads had low density (0.166 ± 0.001 g cm–3), high porosity (87% v/v) and high surface area (197 m2 g–1). IR, 1H magic angle spinning (MAS) and 13C cross-polarization magic angle spinning (CPMAS) NMR showed the characteristic peaks of urea and the isocyanurate ring. Scanning electron microscopy (SEM) showed the presence of a thin, yet porous skin on the surface of the beads with a different (denser) morphology than their interior. The synthetic method shown here is simple, cost-efficient and suitable for large-scale production of PUA aerogel beads.

An emulsification/internal setting technique for the preparation of coated and uncoated hybrid silica/alginate aerogel beads for controlled drug delivery

Coated and uncoated hybrid silica/alginate aerogel beads have been prepared with a new emulsification/internal setting technique. Hybrid aerogels combine high specific surface area and good mechanical strength of the inorganic component with biodegradability and bioadhesivity of the organic fraction so resulting in promising materials for drug-delivery. The hybrid beads were characterized through laser diffraction, BET and SAXS. Small particles (average diameter = 282 μm) with high specific surface area (more than 900 m2/g) and quite stable structural properties were obtained. Preliminary tests were performed to investigate how different kinds of coatings (alginate/hydroxypropyl methylcellulose, silica/hydroxypropyl methylcellulose or hydrophobic silica coating) affected the loading and release rate of model-drug ketoprofen. Among all results, uncoated hybrid aerogel beads resulted in burst release with 90% of the initial loaded drug delivered after 3 min while release was prolonged up to 60 min when a hydrophobic silica coating was used.

Chlamydomonas angulosa (Green Alga) and Nostoc commune (Blue-Green Alga) Microalgae-Cellulose Composite Aerogel Beads: Manufacture, Physicochemical Characterization, and Cd (II) Adsorption.

This study presents composite aerogel beads prepared by mixing dissolved cellulose with Chlamydomonas angulosa and Nostoc commune cells, respectively, at 0.1, 0.3, and 0.5% (w/w). The manufactured composites (termed regenerated cellulose (RC)), with C. angulosa (RCCA-(1, 3, and 5)), and with N. commune (RCNC-(1, 3, and 5)) were analyzed. Both RCCA-5 and RCNC-5 showed the high specific surface area to be about 261.3 and 332.8 m2·g−1. In the microstructure analysis, network structures were observed in the cross-sections of RC, RCCA-5, and RCNC-5. The pyrolysis temperature of the RCCA-5 and RCNC-5 composite aerogel beads was rapidly increased about 250 °C during the mixing of cellulose with C. angulosa and N. commune. The chemical analysis of RC, RCCA-5, and RCNC-5 showed peaks corresponding to various functional groups, such as amide, carboxyl, and hydroxyl groups from protein, lipid, and carbohydrate. RCNC-5 at pH 6 demonstrated highest Cd2+ removal rate about 90.3%, 82.1%, and 63.1% at 10, 25, and 50 ppm Cd2+, respectively. At pH 6, Cd2+ adsorption rates per unit weight of the RCNC-5 were about 0.9025, 2.0514, and 3.1547 mg/g at 10, 25, and 50 ppm, respectively. The peaks assigned to the amide, carboxyl, and hydroxyl groups in RCCA-5, RCNC-5, and RC were shifted or disappeared immediately after adsorption of Cd2+. The specific surface area, total pore volume, and mean pore diameter of composites was decreased due to adsorption of Cd2+ on the developed materials. As can be seen in the X-ray powder diffraction (XRD) spectrum, significant changes in the molecular structure of the composite aerogel beads were not observed even after adsorption of Cd2+.

Preparation of chitosan/lanthanum hydroxide composite aerogel beads for higher phosphorus adsorption

In this study, chitosan and lanthanum hydroxide composite aerogel beads were prepared for phosphorus adsorption via co precipitation and supercritical carbon dioxide drying technique. The porous structure of composite aerogel beads was investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) measurements. The results showed that the aerogel bead with mass ratio of chitosan to lanthanum chloride 100:50 exhibited a larger surface area of 172.74 m2/g and a pore volume of 1.05 cm3/g, respectively. Also the phosphorus adsorption kinetics of the aerogel bead showed a faster adsorption rate and the larger adsorption capacity (148.33 mg/g) for phosphorus. In addition, adsorption kinetics model analysis showed that the phosphorus adsorption process fitted both pseudo-first order and pseudo-second order kinetic model.

A redox strategy to tailor the release properties of Fe(III)-alginate aerogels for oral drug delivery

Iron(III)-crosslinked alginate aerogel beads (d = 3–5 mm) were prepared and loaded with ibuprofen by using the technique of adsorptive deposition from supercritical CO2. Additional formulations were prepared where the aerogels were co-impregnated by ibuprofen and ascorbic acid. The release of ibuprofen from the Fe(III)-alginate is much faster in pH = 7.4 (PBS) than in pH = 2.0 (HCl), which can be explained by the faster dissolution and higher swelling of the alginate matrix in PBS. By decreasing the size of the beads and using a higher G content alginate the release rate could be slightly increased. A marked acceleration of drug release was achieved in both HCl and PBS by incorporating ascorbic acid into the Fe(III)-alginate aerogel preparations. The explanation is that in aqueous media ascorbic acid in situ reduces the crosslinking Fe(III) to Fe(II). The latter does not interact strongly with alginate, which promotes the hydration of the chains, thus the erosion and dissolution of the carrier matrix.

Rheology of cellulose-[DBNH][CO2Et] solutions and shaping into aerogel beads

Cellulose aerogel beads made with JetCutting technology and dried by supercritical CO2 extraction.

Biomolecules for Removal of Heavy Metal.

Patents reveal that heavy metals are natural constituents of the earth's crust, but some heavy metals like cadmium, lead, mercury, arsenic etc. are injurious to living organisms at higher concentration. Nowadays, anthropogenic activities have altered geochemical cycles and biochemical balance of heavy metals. Biomolecules are used nowadays for removal of heavy metals compared to other synthetic biosorbents due to their environmental friendly nature and cost effectiveness. The goal of this work is to identify the role of biomolecules like polysaccharides, polypeptides, natural compounds containing aromatic acid etc. for heavy metal removal by bio sorption. It has been observed that efficiency of biomolecules can be increased by functionalization e.g. cellulose functionalization with EDTA, chitosan with sulphur groups, alginate with carboxyl/ hydroxyl group etc. It was found that the porous structure of aerogel beads improves both sorption and kinetic properties of the material. Out of polypeptides metallothionein has been widely used for removal of heavy metal up to 88% from seawater after a single centrifugation. These cost effective functionalized biomolecules are significantly used for remediation of heavy metals by immobilizing these biomolecules onto materials.

Ag2O/sodium alginate-reduced graphene oxide aerogel beads for efficient visible light driven photocatalysis

In this work, one facile and green method was developed to resolve the instinct defects of pure Ag2O and increase visible-light photocatalytic activity of Ag2O-based catalyst. In which, Ag2O was immobilized in sodium alginate-reduced graphene oxide (ALG-rGO) aerogel beads. The as-prepared aerogel beads showed a well-defined interconnected three-dimensional porous network and displayed the highest photocatalytic activity with a mass ratio of 40:1 (ALG:rGO). For the degradation of cationic Rhodamine B (RhB) and anionic dye Orange II (OII) dyes, rate constants were 1.95×10−2min−1 and 4.13×10−2min−1, which were 2.4 and 3.1 times higher than those of Ag2O/ALG aerogel beads, respectively. The further studies demonstrated that presence of rGO can effectively decrease the size of Ag2O, extend photoresponding range (UV to near-infrared light spectrum), speed-up separate photogenerated electrons and holes, retard charge recombination, and prolong electron lifetime and effective carrier diffusion length. The potential mechanism for RhB and OII degrading was expounded, and main active species in the degradation reactions of dyes were investigated by a series of trapping experiments. It offered a promising photocatalyst to purify the wastewater, and provided a sophisticated understanding of the pivotal role rGO acting in photocatalysis.

Preparation of PEI/CS aerogel beads with a high density of reactive sites for efficient Cr(vi) sorption: batch and column studies

PEI/CS aerogel beads with a high density of reactive amino groups, with the aim of efficient Cr(vi) removal from aqueous solutions under column conditions, were easily preparedviacombinational yet controllable sol–gel and freeze drying processes.

Polyethylenimine-functionalized cellulose aerogel beads for efficient dynamic removal of chromium(vi) from aqueous solution

Cellulose aerogel beads with high a density of reactive amino groups were facilely prepared via a cross-linking reaction for efficient dynamic removal of Cr(vi) from aqueous solutions.

Structure and thermal properties of millimeter-scale alumina aerogel beads formed by a modified ball dropping method

We report the formation of alumina aerogel beads with a modified ball dropping method, in which alumina alcogel beads are formed by extruding alumina sol containing a small amount of polyvinyl alcohol through nozzles into ammonia water.