Gelling Process of Alginate Gel Spheres Having Various Counterions and Their Equilibrium Swellings

Abstract

Alginate gel spheres were prepared by pouring an aqueous solution of sodium salt of alginate (NaAlg) into CaC1₂, SrCl₂, and BaC1₂ solutions. The changes of weight and volume of the gel during the gelling process were measured. A rapid dehydration occured initially (1-2h), and slow one was followed (3-4 d). The ratios of equilibrium weights of the gels to those of the original NaAlg drops wg, e/ws, depended on the kinds of electrolytes and showed the minimum (0.4'0.5) about at the concentration of electrolytes C_M=-0.05 mol/dm3. The order of wg.e/ws.o were C a->Sr-=BaAalgn dw erer eversoe f thes electivitioefst hec ounterions and the magnitudes of the elastic moduli. The equilibrium CaAlg gels were analyzed by Flory's theory of swollen network, and interaction parameter x, was found to decrease with increasing the concentration of CaCl₂.