Adsorption of Acid Orange 7 on the surface of titanium dioxide.

The adsorption of a model textile azo-dye, Acid Orange 7 (AO7), on the surface of titanium dioxide was extensively investigated in aqueous TiO(2) suspensions over wide ranges of AO7 concentrations (1 x 10(-4)-3 x 10(-3) M) and pH values (2-10). Results obtained with the use of a variety of techniques, including potentiometric titrations, adsorption isotherms, adsorption edges, and microelectrophoresis, were used for the description of the "AO7 solution/TiO(2) surface" interface. This has been achieved by taking into account the effects of pH on the speciation of the dye in solution and on the nature and population of the surface groups of TiO(2).