Simultaneous degradation of pharmaceuticals by classic and modified photo-Fenton process

Pharmaceutical compounds are known to be persistent. Their presence after conventional treatments in sewage treatment plants may harm aquatic environments. The simultaneous degradation of the pharmaceuticals gemfibrozil, hydrochlorothiazide and naproxen involving photo-Fenton processes was evaluated using different sources and concentrations of iron (Fe2+, Fe3+ and the iron complexes of oxalate- FeOx), initial pH (2.6, 5.0 and 7.0) and concentrations of H2O2. The classic photo-Fenton reaction (at initial pH 2.6, using Fe2+ and Fes+) showed a limited efficiency in promoting gemfibrozil degradation, which, based on evidence provided by LC-MS measurements, is related to the formation of associations between this compound and iron ions. The simultaneous degradation of gemfibrozil and the other compounds was improved using FeOx (1.0 mg L-1- in iron) at an initial pH of 2.6 and 2.0 mg L-H2O2. In addition, using this catalyst it was possible to efficiently degrade the pharmaceuticals at an initial pH of 5.0, reaching complete degradation of these compounds with a treatment time varying between 20 and 60 min and generating a low toxicity effluent. These results highlight the potential applicability of ferrioxalate as a photocatalyst in the photo-Fenton process as an alternative method to degrade this kind of pollutant at a pH near neutrality.