Pharmaceutical compounds are considered as emerging environmental pollutants due to their persistence in the aquatic ecosystem even at low concentrations [1]. Fluoxetine is one of the antidepressants widely used in the past decade. This drug has been detected in surface waters due to imperfect destruction after therapeutic use [2]. In this study, the degradation of fluoxetine drug in aqueous solutions was investigated via the homogeneous photochemical process using potassium persulfate in the presence UV-LED irradiation. Persulfate oxidizing agent was activated with the emitted ultraviolet/visible light [3]. A falling film horizontally located light source photo-reactor was employed for conducting experiments. An array of 24 LED lamps (1 W with 395-400 nm wavelength) was utilized. The content was circulated by means of an external pump. Iron salts can be incorporated in this process favoring sulfate anion radical generation and the degradation efficiency [4]. The variation of degradation efficiency with persulfate concentration, Fe2+ concentration, pH, reaction temperature, and reaction time variables were investigated. The substrate concentration was followed by means of a UV-Vis spectrophotometer. The fluoxetine maximum wavelength is 226 nm. Under the found optimum conditions of persulfate concentration (100 mg/L), Fe2+ concentration (1 mg/L), natural pH (6.4) and temperature (40 to 71.1% after only 40 min treatment (fluoxetine initial concentration of 40 mg/L). Meanwhile, kinetic studies showed that degradation of fluoxetine follows a pseudo first-order reaction. In mechanism study, the free radical test indicated that both the sulfate radical and hydroxyl radical were involved in the reaction system, and further, the degradation products were explored by liquid chromatography-tandem mass spectrometry. The transformation pathways were proposed, being mainly the hydroxylation, breaking of the carbon-oxygen bond, defluorination of the -CF3 to the carboxylic group,
