Sorption characteristics and factors affecting the adsorption behavior of bisphenol A and 17β-estradiol/ethinyl estradiol in river- and farmland-based artificial groundwater recharge with reclaimed water

Abstract

Endocrine-disrupting chemicals (EDCs) in river- and farmland-based natural groundwater recharge using reclaimed municipal wastewater pose a major threat to groundwater-based drinking water supplies in Beijing, China. The sorption characteristics of three selected typical EDCs, bisphenol A (BPA), 17β-estradiol (E2), and ethinyl estradiol (EE2) were investigated in river sediment– and farmland soil–water systems to simulate the sorption process and the factors influencing sorption during reclaimed water recharge. The results showed that the two-compartment first-order model fitted the kinetics of sorption very well (R2 > 0.99). The fast sorption rates for E2 and EE2 onto soil were higher than those onto sediment, while the rate was different for BPA. The partitioning and π–π bonds might be a relatively more important mechanism for the sorption of BPA onto sediment, while surface adsorption contributed significantly to E2 and EE2 sorption onto soil. The fast sorption rate was negatively correlated to the △G values in all adsorption media. The average removal rate (η) of the three EDCs was in the order η(BPA) < η(17β−E2) < η(EE2) and soil < sediment which showed that E2 was easily adsorbed onto sediment, while BPA was more mobile in the farmland-based artificial groundwater recharge system. The absolute free energy values of ΔG were less than 40 kJ/mol, indicating that the adsorption process consisted primarily of physical sorption. With an increase in pH value, the adsorption capacity and partition coefficient clearly decreased, especially when the pH value was higher than the pKa values of the EDCs. The amounts of BPA, E2, and EE2 that were adsorbed increased with an increase in ionic strength, especially for the E2 and EE2, because the amount of ion exchange and polar sorption would increase. However, these values decreased with an increase in temperature. These results could be useful for predicting a potential pathway for removal and the ecological risks of EDCs when using reclaimed municipal wastewater for aquifer recharge.