Influence of Multivalent Ions on the Electrosurface Properties of Tungsten(VI) Oxide Particles in Hydrosols

Hydrosols containing tungsten(VI) oxide nanoparticles have been studied by the electrooptical and electrophoretic methods. The influence of multivalent ions (tetravalent thorium and trivalent lanthanum cations) on the zeta-potential and polarizability of tungsten(VI) oxide particles has been determined. The dispersion dependences of the polarizability of tungsten(VI) oxide particles have been studied. A strong dependence of the electrokinetic potential and a weak dependence of the polarizability of the particles on the concentrations of thorium and lanthanum cations in the sols have been found. The polarizability of the particles is low and weakly depends on the frequency of the field polarizing the particles. This is atypical for colloidal particles, for which the thickness of the dense part of the electrical double layer is comparable with the size of molecules, while the polarization of the electrical double layer is determined by its diffuse part. The obtained results have led to a conclusion that, for tungsten(VI) oxide particles in the studied concentration range, the majority of multivalent counterions are located in the dense part of the electrical double layer due to their high adsorption potential.