ATR-FTIR study of the stability trends of carboxylate complexes formed on the surface of titanium dioxide particles immersed in water

The use of titanium dioxide slurries or powders to enact the photocatalytic destruction of contaminants in water depends on its properties as a wide g ap semiconductor. The charge transfer events at the water/semiconductor int erface are strongly modified by the interaction of the titanium dioxide sur face with solutes present in water, In this paper, we discuss the stability trend of the surface complexes formed by a series of organic anions (chemi sorbed on TiO2). The surface interaction was studied by ATR-FTIR, and the s pectra obtained at different complexant concentrations and pH values were u sed to derive Langmuir-type stability constants. It is shown that surface c omplexation can be described as the dissociative chemisorption of the neutr al acid, with the creation of a zwitterionic surface species. There is a li near Gibbs energy relationship (LGER) between the stability of the surface complexes and the first acidity constant of the ligand, with slope of 1.8. (C) 2001 Elsevier Science B.V. All rights reserved.