Decomposition of naproxen by plasma in liquid process with TiO2 photocatslysts and hydrogen peroxide.

Naproxen (NPX), one of the representative non-steroidal anti-inflammatory drug (NSAID) ingredients, was decomposed by plasma in liquid process (PiLP). Strongly oxidized species generated in the plasma field of the PiLP, such as OH radicals, were confirmed by optical emission spectroscopy Increasing the operation parameters (pulse width, frequency and applied voltage) of the power supply promoted plasma field generation and OH radical generation, and affected the NPX decomposition rate. Although the NPX decomposition reaction rate was improved by up to 18-30% by adding TiO2 photocatalyst powder and H2O2 to PiLP, but the optimal addition amount should be determined considering the plasma generation and scavenger effects. A decomposition pathway was proposed, in which NPX was mineralized into CO2 and H2O through five intermediates mainly by decarboxylation, demethylation, hydroxylation, and dehydration reactions via hydroxyl radicals.

Removal of oxytetracycline from water by liquid-phase plasma process with an iron precipitated TiO2 photocatalyst.

This study developed a new water treatment method using liquid-phase plasma (LPP) process that can decompose oxytetracycline (OTC) remaining in the aquatic environment. Relatedly, the OTC causes damage to the human body and cannot be removed by traditional water treatment methods. The study also prepared Fe/TiO2 photocatalyst responding to visible light using the LPP process. In particular, the OTC decomposition efficiency of the LPP process improved by more than 10% with the use of the Fe/TiO2 photocatalyst as compared to that of the one with the use of bare TiO2 photocatalyst. Further, the optimal LPP process parameters and Fe/TiO2 photocatalyst amount in the LPP process for OTC decomposition were established in the study. Finally, the degradation pathway of the OTC in the LPP process was found based on the five intermediates of the LPP reaction that were detected by the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis. In particular, the decomposition pathway was estimated to be involving the mineralization of the OTC through demethylation, deamination, dehydration, and ring cleavage.