Photocatalytical removal of fluorouracil using TiO₂-P25 and N/S doped TiO₂ catalysts: A kinetic and mechanistic study

In the present study, the photocatalytic activity of TiO₂-based photocatalysts toward degradation and mineralization of the anti-cancer drug 5-fluorouracil (5-FU) in aqueous phase was investigated under simulated solar and visible irradiation. Commercial TiO₂ (P25) and N/S-doped TiO₂ catalysts synthesized by a simple sol–gel method were used as photocatalysts. TiO₂ P-25 was found to be the most photoactive catalyst for the removal of 5-FU, under simulated solar irradiation. Among N/S-doped TiO₂ catalysts, the one with molar Ti:N/S ratio equal to 0.5 was the most efficient under simulated solar irradiation. In contrast, under visible irradiation the catalyst with equimolar Ti:N/S ratio showed the highest performance for the removal of 5-FU. Scavenging experiments revealed that HO· radicals and h⁺ were the major reactive species mediating photocatalytic degradation of 5-FU using TiO₂ P-25 and N/S-doped TiO₂ catalysts, under simulated solar irradiation. On the other hand, the essential contribution of ¹O₂ and O₂·⁻ in the degradation of 5-FU under visible light was proved. The transformation products (TPs) of 5-FU, were identified by LC-MS-TOF suggesting that defluorination followed by hydroxylation and oxidation are the main transformation pathways, under all the studied photocatalytic systems. - Highlights: • Photocatalytic degradation of 5-fluorouracil using TiO₂-based photocatalysts was studied. • N/S-doped TiO₂ catalysts was proved efficient for the removal of 5 fluorouracil. • Defluorination followed by hydroxylation and oxidation are the main transformation pathways. • HO· radicals are the main reactive radicals under simulated solar light. • ¹O₂ and O₂·⁻ oxidant species contributed significantly under visible light.