Feasibility of Fenton's Oxidation for Removal of Estrogens from Aqueous Solutions

Presented research has been focused on the effectiveness of degradation of natural (17 beta-estradiol - E2) and synthetic (17 alpha-ethinylestradiol - EE2) hormones with Fenton's oxidation. Numerous studies have demonstrated, that the impact of hormones on organisms was shown already at environmental concentrations close to 1 pg L-1, so their effective removal from wastewaters is important. Fenton's oxidation is very efficient in terms of oxidation of organics, while its main withdrawal is the formation of waste sludge, leading to adsorption of organics, which sometimes makes it impossible to reliably value the extent of actual degradation. The ratio among degradation and adsorption of estrogens on sludge during oxidative treatment was determined as a part of our study. It depends upon the molar ratio of reagents Fe2+ and H2O2 (1:0.5, 1:10; 1:20; 1:33), reaction time and initial concentrations of the investigated estrogens E2 (0.279/27.9 mg L-1) and EE2 (0.296/29.6 mg L-1). The most efficient removal of E2 was achieved at 1:33 molar ratio of reagents (100%, 26-50% adsorption) while EE2 removed efficiently at 1:10 and 1:33 ratios (99-100%, 20-76% adsorption). It was confirmed, that adsorption plays an important role in Fenton's oxidative treatment of estrogens. It is prevailing process at higher pHs, while at lower ones (pH = 3.0-5.0) oxidation is dominant, because it is not limited by mass transport.