Efficient removal of the pharmaceutical pollutants included in the EU Watch List (Decision 2015/495) by modified magnetite/H2O2

Abstract

The European Union (EU) approved in 2015 a Watch List of pollutants of emerging concern especially harmful for the aquatic environment (Decision 2015/495/EU). In this work, we explore the application of an inexpensive and environmentally-friendly catalytic system based on modified natural magnetite (Fe3O4-R400) and H2O2 for the removal of all the pharmaceuticals included in the EU Watch List (hormones: estrone, 17-beta-estradiol and 17-alpha-ethinylestradiol; macrolide antibiotics: azithromycin, clarithromycin and erythromycin; and the non-steroid anti-inflammatory diclofenac). The experiments were carried out with a representative initial concentration of the drugs (1000 μg L−1) at a circumneutral pH value (pH0 = 5) within the temperature range of 17–50 °C. A low catalyst concentration (0.2 g L−1) was used while the applied amount of H2O2 corresponded to the stoichiometric one for the complete mineralization of the drugs (4–6 mg L−1). Operating under ambient-like conditions, total conversion of the target pollutants as well as the aromatic intermediates was achieved. Notably, total organic carbon was strongly reduced (>50%), being the residual carbonaceous products short-chain organic acids. The applicability of the catalytic system was demonstrated using different real wastewater treatment plant (WWTP) effluents spiked with the mixture of pharmaceuticals. Apart from the complete removal of pharmaceuticals in relatively short reaction times (60–90 min), the disappearance of total coliforms was warranted. Remarkably, the catalyst showed a reasonable stability, with low iron leaching (<0.7 mg L−1) and maintaining its magnetic properties almost unchanged.