Square-wave voltammetry of a cathodic stripping reaction complicated by adsorption of the reacting ligand Original Research Article

A model of the cathodic stripping process of an insoluble mercuric salt precipitated on the mercury electrode surface and complicated by adsorption of the reacting ligand, is developed under conditions of square-wave voltammetry (SWV). The adsorption isotherm of the reacting ligand is supposed to be linear. Theoretical relationships between the properties of the SW response and the parameters of the redox reaction as well as SW excitation signal are analyzed. Both reversible and quasireversible redox reactions are considered. The phenomena such as quasireversible maxima and splitting of the SW peak are discussed. The theoretical model is verified experimentally with the mercury/6-propyl-2-thiouracil system. The kinetic parameters of the redox reaction of mercury in the presence of 6-propyl-2-thiouracil in 1 mol dm−3 KNO3 are estimated as follows: standard rate constant ks=25±5 s−1 and cathodic transfer coefficient α=0.6±0.1. The adsorption constant of 6-propyl-2-thiouracil on the mercury surface in 1 mol dm−3 KNO3 is estimated to be in the range: 0.1≤log(K/cm−1)≤1.2.