P. Nikitas, ADSORPTION FROM DILUTE-SOLUTIONS AT UNCHARGED INTERFACES - A SEMI-THERMODYNAMIC TREATMENT, Russian journal of electrochemistry, 31(8), 1995, pp. 747-758
When an adsorbed film is formed at an uncharged interface, then an ele
ctric field is established across this film created by the dipoles of
the adsorbed species. Similarly, an electric field may be established
parallel to the adsorbing surface from the in-plane dipoles of the ads
orbed species. These electric fields affect the dipole-dipole interact
ions and therefore they influence the surface activities of the adsorb
ed species. Their effect on the surface activities was taken into acco
unt by means of the electrostatic theory of dielectrics and the Gauss
theorem which was used to correlate the potential drop across and para
llel to the adsorbed layer with its composition. Then based exclusivel
y on the properties of the various thermodynamic functions of the surf
ace solution the chemical/electrochemical potentials of the constituen
ts of this layer were derived without additional modelistic assumption
s. In this approach the molecular information, which is fitted to ther
modynamic arguments, is more general and therefore more reliable than
that obtained from a certain model. The new adsorption isotherms, whic
h arise from the chemical/electrochemical potentials, can take into ac
count changes in the surface layer dielectric constant and the orienta
tion of the adsorbed species during the adsorption process. The isothe
rms were compared with a variety of experimental data and a good agree
ment was found in all cases.