Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying

Guastaferro, Mariangela; Baldino, Lucia; Reverchon, Ernesto; Cardea, Stefano

doi:10.3390/gels7040198

Cited by 31 publications

(16 citation statements)

References 57 publications

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“…In the first stage (30–250 °C), degradation resulted from the volatilization loss of physically weak materials on the surface and evaporation-based loss of water vapor from the pores. The main degradation of SCABs occurred in the second stage from 250 to 620 °C, originating from the combustion of the agarose skeleton in the SCABs [ 36 , 37 ]. Moreover, the SCABs underwent hydrophobic treatment.…”

Section: Resultsmentioning

confidence: 99%

Robust SiO2–Al2O3/Agarose Composite Aerogel Beads with Outstanding Thermal Insulation Based on Coal Gangue

et al. 2022

Gels

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Advanced SiO2–Al2O3 aerogel materials have outstanding potential in the field of thermal insulation. Nevertheless, the creation of a mechanically robust and low-cost SiO2–Al2O3 aerogel material remains a considerable challenge. In this study, SiO2–Al2O3 aerogel based on coal gangue, which is a type of zero-cost inorganic waste, was constructed in porous agarose aerogel beads, followed by simple chemical vapor deposition of trimethylchlorosilane to fabricate SiO2–Al2O3/agarose composite aerogel beads (SCABs). The resulting SCABs exhibited a unique nanoscale interpenetrating network structure, which is lightweight and has high specific surface area (538.3 m2/g), hydrophobicity (approximately 128°), and excellent thermal stability and thermal insulation performance. Moreover, the compressive strength of the SCABs was dramatically increased by approximately a factor of ten compared to that of native SiO2–Al2O3 aerogel beads. The prepared SCABs not only pave the way for the design of a novel aerogel material for use in thermal insulation without requiring expensive raw materials, but also provide an effective way to comprehensively use coal gangue.

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Section: Resultsmentioning

confidence: 99%

Robust SiO2–Al2O3/Agarose Composite Aerogel Beads with Outstanding Thermal Insulation Based on Coal Gangue

et al. 2022

Gels

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“…Ice crystals are considered highly auspicious porogen material candidates and are thus prominently used in cryo-polymerization methods. − Generally, cryogel exhibits numerous advantageous properties, such as biodegradability (i.e., in natural polymers), , sponge-like mechanical durability, shape-memory deformation, and super macroporous structure . Cryogels are typically obtained when the polymer precursors are polymerized at temperatures below the freezing point of the solvent.…”

Section: Introductionmentioning

confidence: 99%

Micro Sponge Balls: Preparation and Characterization of Sponge-like Cryogel Particles of Poly(2-hydroxyethyl methacrylate) via the Inverse Leidenfrost Effect

Takase

Shiomori

Okamoto

et al. 2022

ACS Appl. Polym. Mater.

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Here, we report a method to prepare cryogel particles with sponge-like mechanical properties, including high porosity and high elasticity. The preparation process of the cryogel particles of poly(2-hydroxythyl methacrylate) can be summarized in the two following steps: preparation of frozen droplets using the inverse Leidenfrost effect, followed by cryo-gelation by frozen polymerization. First, a polymer precursor was dropwise added into bulk liquid nitrogen (−196 °C). Then, frozen droplets were created by the inverse Leidenfrost effect, which were subsequently polymerized in liquid paraffine (−15 °C). After thawing and drying, the cryogel particles were obtained. The monolithic super-macroporous structure was observed by scanning electron microscopy (SEM). The mechanical properties of the cryogel particles were studied via compression−swelling tests. At maximum compression, the particles achieved 94.3% degree of deformation; remarkably, they returned to their original shape under the swelling state. The strategy proposed herein, which combines the inverse Leidenfrost effect with a cryopolymerization technique, could be applied to prepare various polymer particles without employing surfactants.

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“…In both cases, surface tension and capillary stress are avoided during drying. Materials commonly called aerogels or cryogels are obtained by using either supercritical or freeze drying, respectively [ 24 , 25 , 26 ]. The main disadvantages of the prepared 3D-structures are their extreme fragility and relatively poor mechanical properties, together with low structural stability when immersed in polar solvents, since they are obtained by non-covalent self-assembly [ 27 ].…”

Section: Introductionmentioning

confidence: 99%

“…This work is part of an on-going study [ 24 ] analyzing the sorption of Hg(II) traces from very diluted water solutions (0.05 mg L −1 ) to reach values close to the limits of drinking water (e.g., 1 μg L −1 in Europe [ 43 ] and 2 μg L −1 according to the U.S. Environmental Protection Agency [ 44 ]). The synthetized rGO aerogels, either pristine or involving grafted PEI, were intensively characterized regarding their structure and composition.…”

Section: Introductionmentioning

confidence: 99%

Graphene Oxide/Polyethylenimine Aerogels for the Removal of Hg(II) from Water

Borrás

Henriques

Gonçalves

et al. 2022

Gels

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This article reports the synthesis of an aerogel involving reduced graphene oxide (rGO) and polyethylenimine (PEI), and describes its potential application as an effective sorbent to treat Hg(II) contaminated water. The rGO/PEI sorbent was synthetized using a supercritical CO2 method. N2 physisorption, electron microscopy, and elemental mapping were applied to visualize the meso/macroporous morphology formed by the supercritical drying. The advantages of the synthetized materials are highlighted with respect to the larger exposed GO surface for the PEI grafting of aerogels vs. cryogels, homogeneous distribution of the nitrogenated amino groups in the former and, finally, high Hg(II) sorption capacities. Sorption tests were performed starting from water solutions involving traces of Hg(II). Even though, the designed sorbent was able to eliminate almost all of the metal from the water phase, attaining in very short periods of time residual Hg(II) values as low as 3.5 µg L−1, which is close to the legal limits of drinking water of 1–2 µg L−1. rGO/PEI exhibited a remarkably high value for the maximum sorption capacity of Hg(II), in the order of 219 mg g−1. All of these factors indicate that the designed rGO/PEI aerogel can be considered as a promising candidate to treat Hg(II) contaminated wastewater.

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Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying

Cited by 31 publications

References 57 publications

Robust SiO2–Al2O3/Agarose Composite Aerogel Beads with Outstanding Thermal Insulation Based on Coal Gangue

Robust SiO2–Al2O3/Agarose Composite Aerogel Beads with Outstanding Thermal Insulation Based on Coal Gangue

Micro Sponge Balls: Preparation and Characterization of Sponge-like Cryogel Particles of Poly(2-hydroxyethyl methacrylate) via the Inverse Leidenfrost Effect

Graphene Oxide/Polyethylenimine Aerogels for the Removal of Hg(II) from Water

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