Photocatalytic degradation of direct blue 14 using synthesized CeO ₂ nanoparticles: comparative efficiency with TiO ₂ under variable water matrices

Abstract This study investigates the photocatalytic performance of synthesized cerium oxide (CeO 2 ) nanoparticles for the degradation of Direct Blue 14 (DB14), a model organic pollutant, in comparison with titanium dioxide (TiO 2 ). CeO 2 nanoparticles were synthesized via the chemical precipitation method and characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman spectroscopy. The presence of Ce–O and O–Ce–O stretching vibrations in the FTIR spectra confirmed the successful formation of CeO 2 nanoparticles. XRD and Raman analyses revealed that the nanoparticles possess a crystalline structure, with an average crystallite size of approximately 10 nm and a face-centered cubic (FCC) lattice. Photocatalytic tests demonstrated that both CeO 2 and TiO 2 exhibited significant activity in degrading DB14 under UV irradiation, with enhanced performance observed in acidic media at ambient temperature. CeO 2 nanoparticles achieved optimal degradation efficiency at a dosage of 6 mg, compared to 30 mg required for the TiO 2 /UV system. Overall, CeO 2 nanoparticles exhibit greater activity than TiO 2 representing five-fold higher mass-specific activity. Thermodynamic analysis indicated that the photodegradation process of DB14 is endothermic and non-spontaneous at low temperatures. Additionally, the composition of water matrices significantly influenced photocatalytic efficiency. The presence of ions such as Na + , Cl − , SO 4 2− , K + , Mg 2+ , Ca 2+ , Br − , and HCO 3 − was found to inhibit chemical oxygen demand (COD) removal, thereby reducing the effectiveness of both CeO 2 /UV and TiO 2 /UV systems. Similarly, the use of tap water and seawater led to a decrease in photocatalytic efficiency in both systems.