RESUMO
Oxidative degradation and mineralization of the antifungal drug Nystatin (NYS) was investigated using photochemical advanced oxidation processes UV-C irradiation (280-100 nm), H2O2 photolysis (UV/H2O2), and photo-Fenton (UV/H2O2/Fe3+). The effect of operating parameters such as [H2O2], [Fe3+], and [NYS] initial concentrations on degradation efficiency and mineralization ability of different processes was comparatively examined in order to optimize the processes. Photo-Fenton was found to be the most efficient process attaining complete degradation of 0.02 mM (19.2 mg L-1) NYS at 2 min and a quasi-complete mineralization (97%) of its solution at 5 h treatment while UV/H2O2 and UV-C systems require significantly more time for complete degradation and lower mineralization degrees. The degradation and mineralization kinetics were affected by H2O2 and Fe3+ initial concentration, the optimum dosages being 4 mM and 0.4 mM, respectively. Consumption of H2O2 during photo-Fenton treatment is very fast during the first 30 min leading to the appearance of two stages in the mineralization. The evolution of toxicity of treated solutions was assessed and confirmed the effectiveness of photo-Fenton process for the detoxification of NYS solution at the end of treatment. Application to real wastewater from pharmaceutical industry containing the target molecule NYS showed the effectiveness of photo-Fenton process since it achieved 92% TOC removal rate at 6-h treatment time.
