Shrinking kinetics of calcium alginate beads in alcoholic soda

Calcium alginate beads prepared with a dropping device were cross-linked with epichlorohydrin in order to obtain selective ion exchangers from cross-linked natural polymers. The alginate was first activated with alcoholic soda to convert OH groups into alcoholates. This treatment also leads to considerable dehydration, and the consequent shrinkage of particle size was employed to evaluate the action of NaOH. This paper reports the shrinking kinetics as a function of temperature (2-38°C), initial bead diameter, and reagent concentration. A small number of particles were photographed during reaction in stagnant fluid. Their diameters were then measured and suitably classified. It was found that the shrinkage is dependent on mass transfer, and that its rate is directly proportional to the water concentration gradient on the surface of the particles, and inversely proportional to their initial diameter, if this is not more than 3 mm.