OZONATION OF CETIRIZINE, FEXOFENADINE AND HYDROCHLOROTHIAZIDE: DETERMINATION OF RATE CONSTANTS AND NON-TARGET SCREENING FOR THE IDENTIFICATION OF TRANSFORMATION PRODUCTS

摘要

The removal of pharmaceuticals by ozonation in water and wastewater is currently widely investigated. However, in the last decades, concern about the formation of transformation products (TPs) has been growing. In the present study, the ozonation of three pharmaceuticals considered as emerging contaminants, cetirizine (antihistamine), fexofenadine (antihistamine), and hydrochlorothiazide (diuretic), were investigated: rate constants were determined followed by the characterization of transformation products. Bench-scale ozonation experiments were conducted with the selected pharmaceuticals (0.1 - 0.4 mM) in ultrapure water, and a competition kinetic method was implemented to determine rate constants k_(o3) for the reaction of the target compounds with ozone. All the selected compounds exhibited a high reactivity with ozone with apparent second order rate constants k_(o3,app) ranging from 10~3 and 10~6 M~(-1) s~(-1) in the pH range 3 -12. Transformation products formed during ozonation were detected by a non-target approach using LC-HRMS data (Q-Exactive, Thermo Scientific, San Jose, CA) and SIEVE software (Thermo Scientific, San Jose, CA). Depending on the parent compound, this approach revealed between 6 and 16 transformation products, for which a chemical structure was proposed based on the HRMS and HRMS/MS data. When commercially available, transformation products were confirmed with standards and their formation during ozonation was quantified. Formation yields of these transformation products were then calculated and in the case of hydrochlorothiazide reached 85% for the major ozonation products. Based on the TP structures and known reactivity an ozonation pathway was proposed for the three parent compounds. Finally, environmental relevance of the results was studied with real ozonated wastewater or surface water samples. Fast and efficient removal of the selected parent compounds (> 95%) confirmed the potential of ozonation to remove emerging contaminants. Meanwhile, several ozonation products identified during the bench-scale experiments were confirmed to be present in ozonated effluent samples at ng L~(-1) level.