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Crystallization of Calcium Carbonate in Alginate and Xanthan Hydrogels

Kosanović, Cleo; Fermani, Simona; Falini, Giuseppe; Kralj, Damir (2017) Crystallization of Calcium Carbonate in Alginate and Xanthan Hydrogels. Crystals, 7 (12). ISSN 2073-4352

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Calcium carbonate polymorphs were crystallized in alginate and xanthan hydrogels in which a degree of entanglement was altered by the polysaccharide concentration. Both hydrogels contain functional groups (COOH and OH) attached at diverse proportions on saccharide units. In all systems, the precipitation process was initiated simultaneously with gelation, by fast mixing of the calcium and carbonate solutions, which contain the polysaccharide molecules at respective concentrations. The initial supersaturation was adjusted to be relatively high in order to ensure the conditions suitable for nucleation of all CaCO3 polymorphs and amorphous phase(s). In the model systems (no polysaccharide), a mixture of calcite, vaterite and amorphous calcium carbonate initially precipitated, but after short time only calcite remained. In the presence of xanthan hydrogels, precipitation of either, calcite single crystals, porous polyhedral aggregates, or calcite/vaterite mixtures have been observed after 5 days of ageing, because of different degree of gel entanglement. At the highest xanthan concentrations applied, vaterite content was significantly higher. In the alginate hydrogels, calcite microcrystalline aggregates, rosette-like and/or stuck-like monocrystals and vaterite/calcite mixtures precipitated as well. Time resolved crystallization experiments performed in alginate hydrogels indicated the initial formation of a mixture of calcite, vaterite and amorphous calcium carbonate, which transformed to calcite after 24 h of ageing.

Item Type: Article
Uncontrolled Keywords: calcium carbonate ; crystallization ; hydrogels ; alginate ; xanthan
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Division of Materials Chemistry
Project titleProject leaderProject codeProject type
Bioinspirirani materijali - mehanizmi nastajanja i interakcija-Bio-Mat-FormDamir KraljIP-2013-11-5055HRZZ
Depositing User: Damir Kralj
Date Deposited: 12 Jun 2019 11:32
DOI: 10.3390/cryst7120355

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