Dry-Phase Photodegradation of Benzene, Toluene and Xylene (BTX) Using Cu-Doped TiO₂ Under LED Light Irradiation

Protection of the environment is severely hampered by aromatic volatile organic compounds in real life. Many expensive technologies such as thermal oxidation, biofiltration and cryogenic condensation have been tried to reduce the levels of benzene, toluene, and xylene (BTX) while not much cost-effective research has been done. The photodegradation of BTX under dry environments using visible LED light, was studied to propose a novel and cost-effective way to remove BTX gases. Here, photocatalytic degradation of specific BTX gases was carried out using Cu-doped TiO₂ photocatalysts, which were prepared using a simple chemical precipitation-reduction technique by varying amounts of Cu precursor to obtain a set of samples like pristine TiO₂ nano powders (P25), 8 wt% Cu-TiO₂, 23 wt% Cu-TiO₂, and 28 wt% Cu-TiO₂. Techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV-Vis), photoelectrochemical analysis (PEC), electrochemical impedance spectroscopy (EIS) and photoluminescence spectroscopy (PL), were used to characterize the pristine P25 and Cu-doped TiO₂ photocatalysts. These methods helped to investigate the crystal structure, morphology, chemical composition, valence state, porosity, and surface reactivity of the photocatalysts. The effectiveness of BTX removal and its byproducts produced by LED irradiation are examined. Currently, the starting BTX gas concentration was set at 50 ppm with a room temperature of 25 ± 3 °C and relative humidity of 35%. Compared to toluene, benzene and xylene showed greater average removal efficiency (RE) during the photodegradation process. After photodegradation, the composition of the off gases was examined, with possible byproducts. To evaluate mineralization, the concentration of carbon dioxide was monitored to verify the completion of photodegradation. Among the photocatalysts, the results showed that 23 wt% Cu-TiO₂ outperformed pure P25 and other Cu-doped TiO₂ samples in terms of photocatalytic degradation activity for xylene, toluene, and benzene, with average removal efficiency rates of 85.2%, 81.0%, and 70.5%, respectively. The corresponding average CO₂ mineralization rate was evaluated to be 49.5% for flowing gaseous benzene under dry conditions. The better degrading performance of 23 wt% Cu-TiO₂ was caused by an increase in the single BTX adsorption capacity, an increase in the efficiency of light harvesting, and an improvement in the electron-hole separation efficiency. Furthermore, 23 wt% Cu-TiO₂ exhibited high photocatalytic activity, which was mostly attributed to active species such as hydroxyl radicals and peroxide radicals. This work offers a simple and cost-effective technique for synthesizing Cu-doped TiO₂ photocatalysts to be applicable in dry-phase BTX photoremoval that emulates the naturally occurring predominance of volatile organic molecules.