Comparative Study of the Adsorption Mechanism and Photochemical Oxidation of Chlorophenols on a TiO2 Nanocatalyst

The anatase structure of titanium dioxide (TiO2) nanoparticles was prepared via sol-gel technique and investigated by X-ray diffraction (XRD). The activity of TiO2 was evaluated by photocatalytic degradation of chlorophenolic compounds namely 2-chlorophenol (CP), 2,4-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP) under solar radiation. A computational technique based on semiempirical and density functional theory (DFT) was used to study the effects of chlorophenolic compounds adsorption on the anatase TiO2 (100) surface. Then, E-HOMO, E-LUMO and Delta E were evaluated by three methods, each of which uses density functional theory (DFT) with semiempirical methods. A molecular dynamics (MD) simulation was employed to obtained a great understanding of the adsorption behavior of chlorophenolic compounds on the anatase TiO2 (100) surface. The results of the CP and DCP molecules revealed a perpendicular adsorption via chloride with the surface lattice titanium ion, while this behavior was changed to planar for TCP. To make a comparison between experimental and theoretical calculations, the adsorption energies of chlorophenolic molecules were found to be increased in the order TCP < DCP < CP, as confirmed with the photocatalytic degradation efficiency from the experimental data.