Interaction of Metal Ions with Hydrous Oxide Surfaces

In this paper, the results on the adsorption of cation on hydrous Si02, Ah03 and \u27Mn02 surfaces are presented. Robust (kinetically inert) complexes, e. g. [Co(NH3) 6]3+, contrary to metal ions, e. g. Pb · aq2+, are not able to displace the alkalimetric titration curves of hydrous oxides. In the case of robust complexes the pH-dependence of adsorption is only the function of the 1surface charge (and its pH-dependence). The interpretation of metal ion adsorption in terms of different models is also .given. In solution of monomeric ·metal species, hydrolysis need not be invoked to account for the pH-dependence of adsorpti,on to hydrous oxide surfaces; this dependence can be explained with the basicity of the Meo- gfoup and the affinity of this group to the metal ion. Polymeric or colloidal metal species are usually adsorbed strongly to surfaces; in this case the surface substrate, as long as the surface charge is opposite to the charge of the adsorbing species, has little influence upoP.. the adsoription