EFFECT OF COMPLEXING LIGANDS ON THE ADSORPTION OF CU(II) ONTO THE SILICA-GEL SURFACE .2. ADSORPTION OF CU(II)-LIGAND COMPLEXES

Abstract

The effect of complexing ligands on the adsorption of Cu(II) onto silica gel was investigated in aqueous solution, The adsorption was conspicuously enhanced by 2,2',6',2''-terpyridine, 2-pyridine methanol, and 2-aminomethyl pyridine, as compared to noncomplexed Cu2+ ions, This enhancement was attributed to both hydrophobic interaction in the tow pH region and the formation of ternary surface complexes in the high pH region, It was attenuated by picolinic acid, salicylic acid, and 5-sulfosalicylic acid due to the competition of dissolved ligands and silanol groups with Cu2+ ions. In the presence of pyridine or 3,4-lutidine, the adsorption was slightly increased, as compared to non-complexed Cu2+ ions, In both cases, the adsorption at low pH was interpreted in terms of the type B ternary surface complex formation. For 2-pyridine methanol, the formation of cyclic ternary surface complexes was proposed, The Stern model was adopted for the treatment of the adsorption data in the present study. (C) 1995 Academic Press, Inc.