Specific adsorption of bromide and iodide ions on the (Cd–Ca)/dimethylformamide interface

Abstract

The specific adsorption of bromide and iodide ions from mixed solutions [0.1 m M LiBr + 0.1 (1 – m) M LiBF4] and [0.1 m M LiI + 0.1 (1 – m)M LiBF4] in dimetylformamide (DMF) with the following fractures m of surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 is studied on a renewable liquid (Cd–Ga) electrode by means of an ac bridge. The data on the specific adsorption of Br– and I– anions can be quantitatively described by the Frumkin isotherm, the same as the data on Cl–. It is found that in contrast to Hg/DMF and Bi/DMF interfaces for which the adsorption energy of halide (Hal–) anions (ΔGads) increases with the transition from Cl– to Br– and further to I–, on the (Cd–Ga)/DMF interface, the ΔGads values increase in the inverted sequence I–< Br–< Cl–. It is found that the energy of (Cd–Ga) interaction with Hal– anions (\(\Delta {G_{\left( {{\text{Cd - Ga}}} \right) - Ha{l^ - }}}\)) also increases in the sequence I– < Br– < Cl–. The comparative analysis of the results on the Hal– adsorption on the (Сd–Gа)/DMF and (In–Gа)/DNF interfaces shows that the interaction energies metal–DMF and metal–Hal– correlate with one another. For (Cd–Ga) and (In–Ga) electrodes which have virtually the same energy of metal–DMF interaction, the corresponding values of \(\Delta {G_{\left( {{\text{Cd - Ga}}} \right) - Ha{l^ - }}}\) and \(\Delta {G_{\left( {{\text{In - Ga}}} \right) - Ha{l^ - }}}\) turn out to be close not only for Cl– but also for Br– and I–.