Abstract
In this paper, we investigate the cation-exchange properties of a self-assembled hybrid material towards trivalent ions, lanthanides (La3+,Eu3+, Gd3+,Yb3+) and Fe3+. The bis-zwitter- ionic lamellar material was prepared by sol-gel process from only 3-amino- propyltriethoxysilane (APTES), succin- ic anhydride, and ethylenediamine. In ethanol heated under reflux, the ex- change ethylenediammonium versus Ln3+ proved to be complete by com- plexometry measurements and elemen- tal analyses, one Cl ion per one LnIII remaining as expected for charge bal- ance. In aqueous solution at 20 8C, the material was found to be selective to- wards lanthanide in spite of the similar- ity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lantha- nides reaching up to 20% in some cases. Finally, ion-exchange reaction with FeCl3 was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mçssbauer spectroscopic in- vestigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to de- scribe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material.