Polyamide-6 for the removal and recovery of the estrogenic endocrine disruptors estrone, 17β-estradiol, 17α-ethinylestradiol and the oxidation product 2-hydroxyestradiol in water

Abstract

The removal and recovery of highly potent endocrine disrupting chemicals (EDCs) estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) and the oxidation product 2-hydroxyestradiol (2OHE2) in water was achieved on polyamide 6 (PA6) particles. Hydrogen bonding was the main mechanism driving the adsorption of these EDCs on PA6 at pHs lower than the EDCs pKas (∼10.5) and their adsorption was not affected by the water matrix nor by solute-solute interaction. The adsorption isotherms were linear and the values of the linearity constants for E2 and EE2 were almost double those for E1 and 2OHE2. This was correlated to the number of intermolecular hydrogen bonds via OH groups of the EDCs (H-bond donors) available for interaction with PA6’s surface via the amide groups (H-bond acceptors). The effect of pH on the adsorption of the EDCs on PA6 was significant only at pHs>EDCs pKa (∼10.5). The breakthrough curves of the EDCs on PA6 particles in a fixed-bed column were successfully modelled using a linearised mass transfer model. This study shows that PA6 appears an effective sorbent for the removal as well as the enrichment and pre-concentration of EDCs in wastewater samples.