Abstract--The interaction of H § and Cu2+-ions with Ca-montmorillonite was investigated in 0.1 tool/ dm 3 solutions of Ca(CIO4)z at 298.2 K by potentiometric titrations using both glass electrodes (for H + ) and ion specific electrodes (for Cu z + ). The experimental data were interpreted on the basis of the surface complexation model. The calculations were performed with the least-squares program FITEQL (Westall, 1982) In addition, the ion exchange equilibria Ca 2+ -Cu 2+ and Ca 2+ -H + had to be taken into account. Arguments are presented to identify the groups -= SOH and -= TOH as surface aluminol groups ---AI(OH)(HzO) and surface silanol groups ---Si-OH, respectively.

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Abstract--The effect of three organic ligands on the adsorption of Cu on Ca-montmorillonite was studied. The results indicate that these effects include three different processes: l) Enhanced uptake of positively charged Cu-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 Cu 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 ~-alanine; however, the uptake ofCu(fl-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-square 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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