ADSORPTIVE RATE OF METAL CATIONS ON SILK FIBROIN FIBER

Abstract

The initial adsorption behaviors of Cu(II), Ni (II), Co (II) and Mn (II) on silk fibroin fiber were investigated in terms of the adsorption rate and the diffusion of metal cations into the fiber. The following results were obtained:1) Two adsorption stages were recognized as the initial fast and the later slow one. The initial fast adsorption continued until the adsorbed amounts of metal cations became about 60% of the equilibrium adsorption for Cu (II) and about 75_??_80% for the other metal cations. The initial adsorption rates were 4-27 times higher than those of the later step at pH 5.0, 25°C.2) The apparent activation energies of the initial adsorption were obtained as 5.6_??_13.9 kcal/mol, and the order was Mn (II)_??_Co (II)>Ni (II)>Cu(II).3) On the assumption that the silk fibroin fiber is a cylinder, the apparent diffusion coefficients of Ni (II), Co (II) and Mn (II) which calculated by applying Hill's equation of diffusion were increased with increasing the metal cation concentration in solution. But the effect of the concentration in solution on the apparent diffusion coefficient was smaller for Cu (II) than for the other metal cations.