In this study, the photocatalytic treatment of an organic wastewater with/without phenolic compounds by means of ultraviolet irradiation, titanium dioxide and hydrogen peroxide was examined in an annular photoreactor. Specifically, the effect of initial total carbon concentration, catalyst loading and H 2 O 2 amount on the removal of total carbon was first examined in the case of a synthetic organic wastewater. The influence of partial carbon substitution by phenol, 2-chlorophenol, 2,4-discholophenol, trichlorophenol, and 4-nitrophenol on total carbon removal and target compounds’ conversion was studied keeping constant the initial organic carbon load. It was shown that the process applied was effective in treating the wastewater for initial total carbon 32 mg L -1 , 0.5 g L -1 TiO 2 , and 66.6 mg L -1 H 2 O 2 . Applying UV/TiO 2 and UV/H 2 O 2 , 58% and 53% total carbon removals were achieved, respectively, but combining TiO 2 and H 2 O 2 did not result in a better performance in the case of the synthetic wastewater without any phenolic compounds. In contrast, when a phenolic compound was added, the addition of H 2 O 2 was beneficial, eliminating the differences observed from one phenolic compound to another. The total carbon removals observed were lower than the corresponding final conversions of the target phenolic compounds. Finally, the electric energy per order values were calculated and found to range in 52–248 kWh/m 3 /order, being dependent from the process applied and the phenolic compound present in the wastewater.

In the present work, the photocatalytic degradation and mineralization of 4-tert-butylphenol in water was studied using Fe-doped TiO2 nanoparticles under UV light irradiation. Fe-doped TiO2 catalysts (0.5, 1, 2 and 4 wt.%) were prepared using wet impregnation and characterized via SEM/EDS, XRD, XRF and TEM, while their photocatalytic activity and stability was attended via total organic carbon, 4-tert-butyl phenol, acetic acid, formic acid and leached iron concentrations measurements. The effect of H2O2 addition was also examined. The 4% Fe/TiO2 demonstrated the highest photocatalytic efficiency in terms of total organic carbon removal (86%). The application of UV/H2O2 resulted in 31% total organic carbon removal and 100% 4-t-butylphenol conversion, however combining Fe/TiO2 catalysts with H2O2 under UV irradiation did not improve the photocatalytic performance. Increasing the content of iron on the catalyst from 0.5 to 4% considerably decreased the intermediates formed and increased the production of carbon dioxide. The photocatalytic degradation of 4-tert-butylphenol followed pseudo-second order kinetics. Leaching of iron was observed mainly in the case of 4% Fe/TiO2, but it was considered negligible taking into account the iron load on catalysts. The electric energy per order was found in the range of 28–147 kWh/m3/order and increased with increasing the iron content of the catalyst.

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In this work, TiO2/Ti2O3 composite catalysts were prepared by simple one-step thermal treatment method at various temperatures. The morphology and structure of as-prepared samples have been examined by XRD, TGA and SEM. The XRD characterization results revealed three-phase mixture in sample treated at 550°C, while at 650°C phase transformation from TiO2 anatase to TiO2 rutile and particle size growth was observed. Moreover, the effect of treatment temperature on the photocatalytic degradation of caffeine was evaluated under UV light irradiation. Results indicated that TiO2/Ti2O3-550 exhibited higher catalytic activity than others achieving complete caffeine removal in 60 min.