Activation of persulfate ions by QDs-sized Z-scheme TiO2−x/Cu3Mo2O9 photocatalysts in visible-light detoxification of organic contaminants

As known, colored TiO _2−x is a promising material in the photocatalytic detoxification of water pollutants. Herein, brown TiO _2−x was combined with Cu ₃Mo ₂O ₉ nanoparticles to fabricate quantum dot-sized photocatalysts through hydrothermal method preceded calcination at 350 °C. The optical, electrochemical, textural, structural, and morphological features of the prepared photocatalysts were explored via various techniques. The photocatalytic ability of the materials was studied in the presence of persulfate ions (PS) upon visible light to remove different pollutants. After adding PS, the TiO _2−x/Cu ₃Mo ₂O ₉ (1%)/PS system represented an efficient performance for the degradation of tetracycline (TC), cephalexin (CFX), fuchsine (FS), and methyl orange (MO). The rate constants of TC oxidation in the TiO _2−x/Cu ₃Mo ₂O ₉ (1%)/PS system were respectively 333, 245, 198, 190, 95.2, 92.9, 77.9, and 2.03 times higher than the TiO ₂, PS, TiO ₂/PS, Cu ₃Mo ₂O ₉, Cu ₃Mo ₂O ₉/PS, TiO _2−x, TiO _2−x/PS, and TiO _2−x/Cu ₃Mo ₂O ₉ (1%) systems. So, the synergistic effect of PS and heterogeneous photocatalysis was confirmed by the TiO _2−x/Cu ₃Mo ₂O ₉ (1%) material in the removal reactions. The quenching tests demonstrated that the ^•O ₂ ⁻, h ⁺, ^•OH, and ^•SO ₄ ⁻ are key reactive species. Finally, a Z-scheme mechanism was suggested for the degradation reactions by TiO _2−x/Cu ₃Mo ₂O ₉ /PS system.