The comparison of electrochemical and radiochemical methods in adsorption study of thiourea on the polycrystalline silver electrode in neutral solution

Radiometry and impedance spectroscopy have been compared in the study of thiourea (TU) adsorption on polycrystalline silver electrode. Differential capacity of silver electrode in 0.01 M NaClO4 solution containing TU of concentrations from 10(-6) to 5 x 10(-4) M has been measured. The isotherms of TU adsorption, theta vs c determined from the capacitance and radiometric measurements have been compared and the Gibbs energy of adsorption was calculated. The experimental data were described by the Langmuir isotherm. The radiometric method allowed us to determine the surface concentration of TU. It was found that TU adsorption takes place in the entire range of the applied potential. The process of adsorption is reversible with respect to the electrode potential and the bulk concentration of TU, though the desorption process is not completed and small amounts of TU remain on the surface of Ag electrode.