Determination of binding constants of labile ligands in metal–ligand complexes containing carboxylic groups bound polymer by using breakthrough technique

This study was conducted to confirm the possibilities of determining the binding constants of ligands in metal–ligand complexes containing carboxylic groups bound polymer by using breakthrough technique. Aniline and o-anisidine were selected as model ligands. A mini column apparatus was used to study sorption of ligands onto ligand exchange resin. The experiments were conducted in a constant temperature at 25 °C. The equilibrium sorptions of aniline and o-anisidine were measured in order to determine the part of the sorption on Co(II)-CDAE-sporopollenin resin. The sorption of aniline is seen to be higher than that sorption of o-anisidine. The characteristics of the sorption process were investigated using Scatchard plot analysis (q/C vs. q). In the sorption of o-anisidine, deviation from linearity in the plot of q/C versus q was observed, indicating the presence of multi-model interaction and non-Langmuirean behavior. Furthermore, in high concentration of aniline deviation from linearity in the plot of q/C versus q was appeared. Particularly for o-anisidine, divergence from the Scatchard plot was evident, consistent with the participation of secondary equilibrium effects in the adsorption process. However, Scatchard plot analysis of the equilibrium binding data for aniline onto ligand exchanger gave rise to a linear plot. The ligand binding constants of aniline and o-anisidine were determined as 0.071 and 0.156 mol mol−1 Co2+, respectively. [Copyright &y& Elsevier]