Enhanced photocatalytic activity of azo dyes degradation by urea assisted Mo-doped TiO2 under UV-A light and sunlight irradiation

The widespread use of synthetic dyes, especially in the textile sector, leads to significant environmental pollution, with contaminants that are challenging to eliminate through traditional wastewater treatments. These dyes have complex aromatic structures that contribute to their stability and resistance, posing threats to aquatic ecosystems and human health due to the release of toxic, often carcinogenic compounds. Advanced photocatalysis has shown promise for degrading such pollutants, with urea-assisted molybdenum (Mo)-doped titanium dioxide (TiO₂) standing out for its efficiency. Mo doping enhances TiO₂ photocatalytic activity by extending its light absorption into the visible spectrum and improving charge separation, thus enabling efficient dye degradation under solar irradiation. This approach not only reduces dye pollution but also utilizes sustainable solar energy for water purification. The structural incorporation of Mo within TiO₂ was validated through X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), Photoluminescence (PL) spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses. These characterization methods provided key insights into the Mo-induced modifications that enhance TiO₂ photocatalytic properties, including band gap narrowing, improved visible light absorption, and reduced electron-hole recombination. Elemental mapping by EDS and stable chemical states observed in XPS further underscore the potential of Mo-U-TiO₂ photocatalysts for environmental remediation applications. An optimized Mo-doped U-TiO₂ catalyst was prepared by varying catalyst loading and pH, resulting in substantial photocatalytic efficiency. Under UV light, U-TiO₂ exhibited a 73.7 % degradation efficiency, while 0.2 wt% Mo-U-TiO₂ achieved 99.2 % within 120 min for Acid Black 1 (AB 1) azo dye. Sunlight-driven experiments on Acid Black 1 and Reactive Red 120 (RR 120) azo dyes achieved degradation efficiencies of 91 % and 89.2 %, respectively, at 180 min. These results underscore that Mo-U-TiO₂ has the potential for effective pollutant degradation under various light sources. Reusability and stability studies demonstrated the catalyst's performance over extended periods, confirming its potential for sustained application. Gas chromatography-mass spectrometry (GC-MS) analysis was conducted to elucidate the degradation pathway and trapping experiments were performed to identify the active species involved in the degradation process. Additionally, the catalysts antibacterial activity was evaluated against two Gram-positive ( Staphylococcus aureus, Bacillus subtilis ) and two Gram-negative ( Pseudomonas aeruginosa, Escherichia coli ) bacterial species, highlighting its potential for both pollutant degradation and antimicrobial applications. • Mo doped U-TiO 2 photocatalysts were synthesized successfully. • The XPS spectra confirmed the successful incorporation of Mo 4+ . • The Mo-U-TiO₂ photocatalyst demonstrated exceptional photocatalytic efficiency. • The Mo-doped U-TiO₂ catalyst exhibited notable antibacterial activity.