Diffusion Control Factors Influenced the Ion Exchange between Sodium Counter Ions of Alginate and some Trivalent Metal Cations in the Sol-Gel Transition Process

摘要

The influence of diffusion controls on the rate of gel growth forming coordination biopolymer ionotropic spherical hydrogels resulting from ion exchange process of Na+ counter ions in alginate macromolecular chains by trivalent metal ions such as lanthanum (III)- and cerium (III) electrolyte solutions have been studied. The experimental observations indicated that the ion exchange processes in such sol-gel transformation were inherently stoichiometric processes. The influence of the nature of metal ion concentration of both alginate sol and metal ion electrolytes and temperature as well as the coordination geometry of the complexes formed have been examined. A mathematical approach of such factors which affect the gelation processes such as the mass, density and the radius of droplets of both alginate sol and formed metal-alginate hydrogels has been suggested. A tentative gelation mechanism consistent with the experimental results has been discussed.