Résumé:
The objective of this work is to study the photochemical fate of paracetamol or acetaminophen (PC) as a model pharmaceutical pollutant, in the presence of three iron complexes (FeIII-Aspartate, FeIII-Glutamate, or FeIII-Lactate) under irradiation at 365 nm. First, the FeIII complexes were characterized by UV-visible spectrophotometry; the results confirmed that these complexes are stable in the dark and at room temperature. Under irradiation at 365 nm, the photolysis of these complexes is relatively rapid: about 71% of the FeIII-Aspartate complex (t1/2 = 10.5 min, pH = 3.0) decomposed after 1 hour of irradiation, and about 73% (t½ = 6.2 min, pH = 3.40), and 91% (t½ = 6.4 min, pH = 3.0) in the case of the FeIII-Glutamate and FeIII-Lactate complex, respectively. In addition, this photochemical transformation depends on the wavelength of irradiation and pH. Direct photolysis of paracetamol under UVA irradiation showed a negligible effect, while the presence of FeIIIcomplexes favors the photodegradation of PC, which is faster in the presence of the FeIII-Lactate complex. Photodegradation was studied using various parameters such as initial pH, complex concentration, oxygen, and paracetamol concentration. The addition of T-BuOH as a hydroxyl radical scavenger and anaerobic conditions inhibit the photodegradation of PC, indicating that the photodegradation of paracetamol in the presence of FeIII-Asp, FeIII-Glu, or FeIII-Lact complexes is limited by the formation of hydrogen peroxide, the source of HO●. Seven transformation by-products have been identified by HPLC-MS, mainly hydroxylated derivatives. Reaction pathways are identified, highlighting the role of long-lived photoformed radicals. This study highlights the important role that organic iron complexes can play on the fate of pharmaceutical pollutants in the environment aquatic.
