Empore™ membrane vs. Chelex 100: Thermodynamic and kinetic studies on metals sorption

The sorption of several metal ions on a solid, iminodiacetic based material, the Empore™ chelating membrane, is considered. Determination of the acid-base properties, kinetic of metal sorption and complexing properties, in solutions with different composition is undertaken. The results are compared with those obtained using the classical iminodiacetic resin Chelex 100 in beads. In particular, Cd(II), Fe(III), Pb(II), and Zn(II) are considered. The Gibbs–Donnan, the usual model we used to explain the protonation and the metal sorption on chelating sorbent, is applied also in the present study. On the other hand, the kinetic models selected to describe our data are the two widely applied for fitting ion-exchange data: the Homogeneous Particle Diffusion Model and the Sharing Core (Shell Progressive) Model. In general no significant differences between membrane and resin are found in the thermodynamic properties, but for some metals the kinetics of the sorption on the membrane is slower.