Heterogeneous photocatalytic degradation of chlorophenols over Ag-TiO ₂ nano particles in an aqueous suspension

In the present work, TiO₂ and Ag-TiO₂ catalysts were prepared by an ultrasonic assisted sol-gel method. The physico-chemical characteristics studies of the newly synthesized catalysts were carried out by XRD, TEM, EDX, XPS, UV-Visible absorption spectra and an optical ellipsometry. In order to find out the optical absorption properties of the catalysts, theoretical simulations have been carried out by using the Tauc-Lorentz oscillator model. Photodegradation and mineralisation of the chlorophenols were confirmed by the HPLC and TOC measurements. The rate of a mineralisation trend was observed in the order of P < 2-CP < 2,4-DCP < 2,6-DCP < 4-CP < 2,4,6-TCP by using the Ag-TiO₂ catalyst. The concentration of the main aromatic intermediate products was considerably lower for the Ag-TiO₂ photocatalysts than for pure TiO₂. This experiment demonstrated that the presence of Ag on TiO₂ catalysts could enhance the photocatalytic oxidation of chlorophenols in an aqueous suspension. It was found that the degradation of the chlorphenols by these catalysts followed the pseudo- first order kinetic model.