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Zein-sepiolite superparamagnetic bionanocomposite foams

AuthorsAlcântara, Ana C. S. ; González-Alfaro, Y. ; Darder, Margarita ; Aranda, Pilar ; Ruiz-Hitzky, Eduardo
Issue Date2017
CitationXVI International Clay Conference (2017)
AbstractBionanocomposites are a versatile type of materials that may offer both remarkable structural and multifunctional properties [1]. Interestingly, they can be conformed by different types of processing, giving rise for instance to films and foams of interest for a wide variety of applications, such as bioplastics, gas separation membranes, adsorbents, scaffolds for tissue engineering, packaging or building insulation. In this context, bionanocomposites foams can be prepared by diverse strategies including gas foaming, particulate leaching or freeze-drying [2], being this last one the mostly applied method as hydrophilic polysaccharides or proteins are the largest employed biopolymers and water is used as their main solvent [1,2]. The presence of inorganic solids, for instance clay minerals, as fillers in the biopolymer matrix could help the foaming process, affording nucleation sites that may control the cell density and also contributing to enhance mechanical and physical properties [2,3]. Despite this, the high hydrophilicity of most of the commonly used biopolymers limits the bionanocomposite foam stability in aqueous media, hampering their use in certain applications that involve its immersion in aqueous media, e.g., removal of pollutants in water. To overcome this drawback it is possible to stabilize the foam using cross-linking agents or less hydrophilic polymers. For instance, in the case of hydrophobic biopolymers such as zein, the main storage protein of corn, polymeric foams have been prepared using supercritical CO2 or a previously modified zein with hydrophilic compounds [4,5]. Recently, our group has reported a methodology that plays with the different solubility of zein components in presence of ethanol and water to produce zein-montmorillonite nanocomposites [6]. This communication will show how this convenient property of zein can be also applied to produce bionanocomposite foams by assembly of sepiolite to zein following a process that implies the subsequent immersion of mixtures of both components in anhydrous ethanol and water, followed by a final step of freeze-drying. Bionanocomposite foams can be also prepared using a sepiolite that incorporates magnetite nanoparticles (NP) from a ferrofluid, previously prepared by a methodology that have proved to produce very stable superparamagnetic multifunctional materials [7]. As occurs in other biohybrids involving zein assembled to sepiolite and palygorskite fibrous clays [8], the presence of this protein affords hydrophobicity and stability in water to the resulting bionanocomposite foams. Moreover, the existence of strong affinity between zein and the sepiolite-based fillers results in foams that show good mechanical properties and, in certain cases, additional superparamagnetic properties, when they incorporate the magnetite- based filler. The resulting bionanocomposite foams have been tested as adsorbents of 4-chloro-2-methylphenoxyacetic acid (MCPA), here selected as model herbicide, to prove their potential usefulness in environmental remediation. Furthermore, as the zein-sepiolite superparamagnetic bionanocomposite foams could be easily recovered from the aqueous media by applying an external magnetic field (magnet) this type of adsorbent could be easily applied in open water areas.
DescriptionOral presentation given at the XVI International Clay Conference, held in Granada (Spain) on July 17-21, 2017.
Appears in Collections:(ICMM) Comunicaciones congresos
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