Adsorption parameters in the Alekseev-Popov-Kolotyrkin model complemented by the Frumkin isotherm

The method of a nonlinear regressive analysis of nonequilibrium differentia l capacitance curves in terms of the Alekseev-Popov-Kolotyrkin (APK) model complemented by the Frumkin isotherm is used to determine adsorption parame ters of an organic cation of tetrabutylammonium, an inorganic nitrate anion , and a butanol molecule at an interface with a mercury electrode. The adso rption behavior of the nitrate anion is quantitatively described by the APK model, whereas the Frumkin model is preferable in the case of butanol. Wit h the [C4H9](4)N+ cation adsorbed on a mercury electrode, the EDL structure is probably strongly affected by the formation of ionic pairs.