INDUCED REACTANT ADSORPTION IN METAL-POLYELECTROLYTE SYSTEMS - PULSE POLAROGRAPHIC STUDY

A theoretical model is developed for describing the reduction, by normal-pulse polarography, of a metal ion in the presence of a macromolecular ligand, including both the ligand adsorption and the induced adsorption of the metal ion. The following basic assumptions are made: reversible charge transfer at a stationary planar electrode (static mercury drop electrode); labile complex; large excess of ligand compared with the total metal concentration; Langmuirian adsorption for both the ligand and complex species; and diffusion coefficients for ligand and complex species very different from that of the free metal. The mathematical approach is based on transforming the system of differential equations with their boundary conditions into an integral equation which has been solved numerically. A simple procedure to obtain stability constants and adsorption parameters simultaneously from the experimental data is described. This model has been used to reproduce some experimental data from the Cd(II)-polymethacrylate system.