Removal of estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) from wastewater by liquid-liquid extraction

With the recent wide spread concerns of the environmental and public health effects of endocrine disrupting chemicals (EDCs), it is becoming important to develop new techniques to remove these substances from wastewater. EDCs find their way to the environment mainly via effluents from WWTPs. They are often cited as moderately hydrophobic, hence they have tendency to distribute to organic solvents and can then be removed using liquid-liquid extraction (LLE) techniques. However, despite being a mature chemical engineering unit operation, LLE has not been studied for the removal of EDCs in water. This study investigated the removal of three EDCs of concerns including estrone (E1), 17 beta-estradiol (E2), and 17 alpha-ethinylestradiol (EE2) using decamethylcyclopentasiloxane (D5) as an extraction solvent in three water matrix types (Milli-Q, tap water, and a secondary treated wastewater). The study showed that all three EDCs were distributed to D5 but at varying distribution coefficients: K-E1 = 2.66, K-E2 = 0.61 and K-EE2 = 1.67 +/- 5% at pH 6 and 20 degrees C. Due to the high pK(a) values of the three EDCs, pH had no significant effect on K-EDCs up to about pH 9.5 but higher pHs reduced the distribution ratios up to almost zero at pH 12. Van't Hoff equation described the effect of temperature on K-EDCs and showed that the process was endothermic. The overall estrogenic potency of the three EDCs in mixtures was quantified with an E2 equivalent potency, which was found to distribute well into the solvent at a K-E2EQ= 1.43. The study suggests that LLE is an effective method to remove estrogenic potency of wastewater. (C) 2014 Elsevier B.V. All rights reserved.