Comparative degradation of 5-fluorouracil in aqueous solution by using H2O2-modified subcritical water, photocatalytic oxidation and electro-Fenton processes

This study investigated the degradation of the antineoplastic agent 5-fluorouracil (5-FU) widely applied to treat different cancers using different advanced oxidation processes such as electro-Fenton (EF), photocatalysis with TiO2, and H2O2-modified subcritical water oxidation. The treatment with the EF process was the most efficient compared to others. Interestingly, in the EF process, the oxidative degradation of 5-FU behaved differently depending on the anode used. At low currents (20 and 40 mA), Pt and DSA anodes performed better than BDD and Ti4O7 anodes. In contrast, at the higher current of 120 mA, the production of heterogeneous hydroxyl radicals (M(center dot OH)) became important and contributed significantly to the oxidation of 5-FU in addition to homogeneous center dot OH generated in the bulk solution. These latter have high O2-evolution overpotential leading to the high amount of physisorbed M(center dot OH) compared to Pt and DSA. The oxidative degradation of 5-FU was then performed by titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes, both of which showed a lower degradation efficiency and failed to achieve complete mineralization. Finally, a comparison was performed in laboratory-scale, taking into account the following performance indicators: the degradation efficiency, the mineralization power, the cost of equipment and reagents, and the energy required for the treatment of 5-FU.

Automated summary

This study investigated the degradation of the antineoplastic agent 5-FU using various advanced oxidation processes, with the EF process being the most efficient. Different anodes in the EF process showed varying effects on the oxidative degradation of 5-FU, with the production of heterogeneous hydroxyl radicals playing a significant role at higher currents. Titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes showed lower degradation efficiency compared to the EF process. Overall, performance indicators such as degradation efficiency, mineralization power, cost, and energy consumption were considered in the comparison between the different treatment methods.