Synthesis of TiO ₂ catalysts doped with Cu, Fe, and Fe/Cu supported on clinoptilolite zeolite by an electrochemical-thermal method for the degradation of diclofenac by heterogeneous photocatalysis

Aqueous solutions of diclofenac (DCF) were treated by heterogeneous photocatalysis using TiO ₂ catalysts doped with Cu, Fe, and Cu/Fe supported on the zeolite clinoptilolite, which were prepared by a photo/electrochemical method combined with thermal treatment. The parameters evaluated in the preparation of doped TiO ₂ catalysts were the treatment time (30 and 60 min), current intensity (0.5 and 1 A), and presence/absence of UV light. The doped materials were characterized by X-ray diffraction, scanning electron microscopy in conjunction with energy dispersive spectroscopy, absorption atomic and infrared spectroscopy, as well as point of zero charge measurements. The concentration of metal in the modified materials was 2.3 g Fe/g for TiFeZ-7, 2.3 g Cu/g TiCuZ-2, and 3.3 g Fe/g and 1.4 g Cu/g for TiFeCuZ-7. The photocatalysis process was carried out at different pH values (4, 5, 7, and 9) and aqueous DCF concentrations (20, 40, 60, 80, and 100 mg/L). The results indicated that the optimal pH for the oxidation of DCF was 4 with efficiencies over 97%. The degradation kinetics at 10 mg/L indicated the mineralization of DCF during the treatment, where the materials doped with copper afforded superior removal of organic matter with efficiencies of 89.5%, 82.2%, and 84.3% for the TOC, COD, and DCF concentration, respectively, as determined by HPLC, revealing the interesting catalytic effect of this metal in such a photocatalysis process.