Dégradation photocatalytique de polluant pharmaceutique en présence des acides organiques et des métaux de transitions en solution aqueuse.

Abstract

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.