Rate of metal cation sorption by wool fiber.

Abstract

The equilibrium metal cation uptake and the rate of metal cation uptake by wool fiber were examined for Cu(II), Zn(II) and Ni(II) ions, and the results were discussed in terms of the adsorption rate and the diffusion of metal cations into the fiber.It has been found that the metal cation uptake increases with an increase of temperature and the order of the initial adsorption rate is Cu(II)>Ni(II)≥Zn(II). This adsorption behavior seems due to the coordination to metal cation of the carboxyl residues in wool keratin.The apparent activation energies of the initial adsorption were obtained as 5 kcal/mol for all the metal cations examined, regardless of their initial adsorption rates. The apparent diffusion coefficients of Zn(II) and Ni(II) ions which calculated by applying Hill's equation of diffusion increased with increasing the metal cation concentration in solutions. The effect of the concentration in the solutions on the apparent diffusion coefficient was smaller for Cu(II) ion than for Zn(II) and Ni(II) ions.