Comparative Study of the Adsorption of Aromatic Pollutants onto TiO2 (100) Surface via Molecular Simulation

The adsorption mode of benzoic acid onto the anatase TiO2 (100) surface has been studied through the semi-empirical self-consistent field molecular orbital method MSINDO and is compared with previously determined modes of four aromatic compounds: chlorobenzene, aniline, p-chlorophenol and nitrobenzene. The simulation results reveal that aniline and p-chlorophenol molecules are adsorbed with their aromatic ring positioned parallel to the surface although they are linked to a surface lattice titanium atom via the amino nitrogen and phenolic oxygen respectively. In contrast, chlorobenzene, nitrobenzene and benzoic acid are found in perpendicular configurations and they are attached to the surface via the chlorine and oxygen atoms of the NO2 and COOH groups respectively. The calculated substrate–surface interaction energy is influenced by the degree of basicity of the lone pair of the donating atoms, the number of linkages between the substrate and the surface and, further, the hydrogen bonding between the acidic hydrogen and lattice oxygen atom. The computed vibrational density of states for these adsorbed organic pollutants is in reasonably good agreement with available experimental data and previous theoretical results.