Ligand properties of surface silanol groups. I. surface complex formation with Fe3+, Cu2+, Cd2+, and Pb2+

Abstract The adsorption of Fe(III), Cu(II), Cd(II), and Pb(II) from aqueous solutions of constant ionic strength at silica-water interfaces was investigated by potentiometric titrations at 25°. The experimental results are explained in terms of surface complex formation involving deprotonated surface silanol groups as ligands:  Si-OH+M Z+ ⇌( Si-O)M ) (Z− 1)+ + H + ; ∗K 1 8 , 2 Si-OH+M Z+ ⇌( Si-O) 2 M ) (Z− 2)+ + 2H + ; ∗β 2 8 , A linear correlation was found between log ∗ K 1 8 ( ∗ β 2 8 ) and log ∗ K 1 ( ∗ β 2 ) where ∗ K 1 ( ∗ β 2 ) are the stability constants of hydroxo complexes.

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