title: Ion exchange kinetics of magnetic alginate ferrogel beads produced by external gelation.
abstract: This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Fick's second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network.
authors.affiliation: Laboratory of Food Technology, Agricultural Science and Technology Center, Northern Rio de Janeiro State University (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
authors.forename: Vânea Ferreira Torres
authors.initials: VF
authors.lastname: Teixeira
authors.affiliation: Laboratory of Food Technology, Agricultural Science and Technology Center, Northern Rio de Janeiro State University (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil. Electronic address: nadiar@uenf.br.
authors.forename: Nádia Rosa
authors.initials: NR
authors.lastname: Pereira
authors.affiliation: Department of Physics, Chemistry and Mathematics, Federal University of São Carlos (UFSCar), Sorocaba, São Paulo, Brazil.
authors.forename: Walter Ruggeri
authors.initials: WR
authors.lastname: Waldman
authors.affiliation: Laboratory of Food Technology, Agricultural Science and Technology Center, Northern Rio de Janeiro State University (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
authors.forename: Ana Luiza Cassiano Dias
authors.initials: AL
authors.lastname: Ávila
authors.affiliation: Laboratory of Food Technology, Agricultural Science and Technology Center, Northern Rio de Janeiro State University (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
authors.forename: Victor Haber
authors.initials: VH
authors.lastname: Pérez
authors.affiliation: Laboratory of Advanced Materials, Science and Technology Center, Northern Rio de Janeiro State University (UENF), Campos dos Goytacazes, Rio de Janeiro, Brazil.
authors.forename: Rubén Jesus Sánchez
authors.initials: RJ
authors.lastname: Rodríguez
mesh_terms: D000464:Alginates / Q000737:chemistry* / Q000493:pharmacokinetics; D002118:Calcium / Q000737:chemistry; D020723:Glucuronic Acid / Q000737:chemistry / Q000493:pharmacokinetics; D006603:Hexuronic Acids / Q000737:chemistry / Q000493:pharmacokinetics; D007474:Ion Exchange; D007501:Iron / Q000737:chemistry; D060328:Magnetic Phenomena; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013818:Thermogravimetry / Q000379:methods
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D011108:Polymers; D020723:Glucuronic Acid; D012964:Sodium; D007501:Iron; D002118:Calcium
keywords: Biocatalyst support material; Biopolymer; Diffusion; Encapsulation; Thermal degradation