Removal of ethinylestradiol (EE2) from water via adsorption on aliphatic polyamides

This study demonstrates the use of aliphatic polyamides (PAs) as efficient adsorbents for the removal of ethinylestradiol (EE2), a synthetic hormone and high-potency estrogenic contaminant, from water via strong adsorptive interactions. PA612 and PA12 showed significantly higher adsorption capacities than PA6 for EE2 adsorption from water. Isothermal adsorption studies showed that PA612 had an adsorption capacity for EE2 comparable to the benchmark macroreticular polymeric adsorbent, AMBERLTIE XAD4 (XAD4), despite its nonporous structure and far smaller surface area. The substantial adsorption of EE2 on PA612 is predominantly driven by Lewis acid-base interactions between EE2 and PA612 amide functionalities and facilitated by the hydrophobic partitioning of EE2 solutes in water. Rapid column adsorption tests demonstrated efficient removal of EE2 from water on a continuous flow basis. With an empty bed contact time of 0.8–1.0 min, the fixed-bed column with 1.0 g PA612 particles removed the EE2 from 24.1 L of 30 μg L−1 EE2 spiked solution to non-detectable levels by HPLC analysis. Regeneration was readily effected by rinsing the exhausted column with 4 wt.% NaOH solution at room temperature. Regenerated PA612 particles showed consistent performance to fresh PA612 particles in subsequent batch and column adsorption studies.

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► Substantial adsorption of EE2 on polyamide 612 and polyamide 12 particles.
► Exceptional surface-area-normalized adsorption capacity of EE2 on PA612.
► EE2 removed from 24 L feed solution (30 μg/L) by 1.0 g PA612 in column adsorption.
► In-situ regeneration of exhausted column by 4 wt.% NaOH solution at room temperature.
► Regenerated PA612 particles showed no sign of loss in adsorption capacity.