Solar photo-Fenton-like process at neutral pH: Fe(III)-EDDS complex formation and optimization of experimental conditions for degradation of pharmaceuticals

This paper demonstrates the effectiveness of Fe(III)-EDDS complex for degradation of pharmaceutical compounds in a solar photo-Fenton-like process at neutral pH in two different aqueous matrixes. Electrochemical experiments were performed to monitor the formation and stability of the complex, as a function of the amount of complexing agent and pH. Eight compounds, including diazepam, dipyrone, fluoxetine, furosemide, nimesulide, paracetamol, progesterone, and propranolol, were analyzed in distilled water and simulated wastewater, at initial concentrations of 500 mu g L-1. By applying Doehlert matrix design and the response surface methodology the optimal experimental conditions were found to be 0.28 mmol L-1 Fe(III)-EDDS and 5.00 mmol L-1 H2O2, with a ratio of 1:2 for Fe(III)-EDDS. The most persistent transformation products (TPs) generated during the treatment process were investigated using liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. 16 TPs were identified and classified as having high toxicity (according to the Cramer rules), low biodegradability (according to the START scheme), and possible carcinogenicity and/or mutagenicity. Most of the compounds were degraded in the first minutes of treatment, and most of the identified TPs had been successfully removed at the end of the process.