Modified model of electrical double layer for mixed solutions of constant ionic strength

A model is suggested, which generalized the Alekseev-Popov-Kolotyrkin model for the case of mixed solutions of constant ionic strength of the type mc KA_*⁻ + (1 − m)c KA, where A_*⁻ is the surface-active anion that lowers the electrical double layer capacitance as compared with that observed in the presence of surface-inactive anion A⁻. Calculations made for a real system mc NaNO₃ + (1 − m)c NaF showed that at 0.2 ≤ m ≤ 1 a transition occurred from quadratic to linear dependence of adsorption energy on the electrode potential (or charge). The conclusions are in agreement with experimental data obtained for the studied system.