RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

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⁺; *K₁⁸,

2 ≡Si–OH + M^z+ ↔ (≡Si–O)₂M)^(z−2)+ + H⁺; *β₂⁸

A linear correlation was found between log*K₁⁸(*β₁⁸) and log*K₁(*β₁) where *K₁(*β₁) are the stability constants of hydroxo complexes.