Abstract
AbstractThe effects of three organic ligands on the adsorption of copper on Ca-montmorillonite were studied. The results indicate that these effects include three different processes:1)Enhanced uptake of positively charged copper-ligand complexes by ion-exchange.2)Formation of ternary surface complexes involving surface aluminol groups.3)Inhibited uptake due to competition between the surface ligands and the dissolved ligands for dissolved copper.Ethylenediamine promotes copper uptake by ion-exchange at low pH but tends to suppress adsorption at aluminol groups by ligand competition at high pH. The same mechanisms are operative for β-alanine; however, the uptake of Cu(β-ala)+ by ion-exchange is not promoted by the attached ligand. The influence of malonate includes both ligand competition and formation of ternary complexes. A quantitative interpretation based on the surface complexation model using the least-squares programs FITEQL (Westall, 1982) and GRFIT (Ludwig, 1992) is presented. The obtained equilibrium constants are listed in Tables 2b and 3.
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