Identification of Oxidation Intermediates and Investigation of Toxicity Changes in Heterogenic Catalytic Ozonation Process in the Presence of MgO Nanoparticles for Metronidazole Removal from Aqueous Solution

Metronidazole, as one of the most widely used antibiotics in the world, in addition to various benefits, has significant adverse effects on the environment and animals. The catalytic ozonation process is one of the most successful methods for antibiotics removal. However, it should be noted that this process, like other oxidation processes, has some byproducts that can be toxic in the process effluent.
Under optimum conditions for catalytic ozonation in the presence of MgO nanoparticles, 1 sample was obtained from a reactor after 10 minutes of ozonation. The sample was analyzed by gas chromatography–mass spectrometry (GS-MS) and the intermediates were identified. The mineralization rate was determined using TOC analysis and the toxicity changes were calculated through bioassay with Daphnia magna.
Findings: In the present study, 4 compositions were identified as oxidation intermediates. The mineralization rate was about 93.5% and the 48-hour toxicity unit decreased from 1.24 in the influent to 0.32 in the effluent.
A high mineralization rate was obtained in the process. Nevertheless, it was not complete, and thus, the influent solution was converted from toxic to slightly toxic. In conclusion, we can say that catalytic ozonation process in the presence of MgO nanoparticles can be acceptable for metronidazole removal.