The presence of endocrine disrupting compounds (EDCs) such as Ethinylestradiol (EE2) in the aquatic environments has significant impact on the mechanism and the function of the endocrine system of human health and wildlife. The US Food and Drug Administration (FDA) and National Center for Toxicological Research published a report which classified EE2 as a prominent estrogenic chemical in EDCs. In recent experiments it is observed that the hydrophilic PES membrane filter has high efficiency to retain EE2 (98%) from aqueous solution. A computational study is performed to understand and compare the interaction of EE2 with polymer membranes, namely, polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyamide 612 (PA612), and polystyrene (PS). The choice of PES and PVDF polymer membranes in this work is mainly to provide molecular insights to our recent experimental observations on the absorption of EE2. The equilibrium molecular dynamics simulation results based on the membrane-solution interface system show that the interaction of EE2 with PES is specific and strong, whereas the interaction is weak and non-specific for PVDF. The potential of mean forces (PMFs) and binding free energies are also consistent with the interaction behavior found in experiments. To test the proposed computational framework, the systems of testosterone interacting with PES and PVDF are also investigated as a control. Using the similar calculations, the interactions of testosterone with PES and PVDF observed in experiments are also explained. In total, the binding free energies of all the systems considered in this study are in the order as: PES-EE2 &gt; PES-Testosterone &gt; PA612-EE2 &gt; PS-EE2 &gt; PVDF-EE2 &gt; PVDF-Testosterone. The diffusion coefficient results show that the mobility of organic solute in the membrane is in the same trend as their binding free energies with the membranes, indicating that if the interaction with the membrane is strong then the mobility is small. The non-bonded short range interaction energies are consistent with the binding free energies and mobility. The formation of hydrogen-bonds and π-π interactions are observed between the EE2 and polymer membranes. This molecular dynamics simulation study provides molecular insights on the experimental observations and helps as a computational methodology to screen the membrane materials for EE2 removal from waste water and can be extended for the other type of micro-pollutant.

Molecular insight of ethinylestradiol (EE2) interaction with polymer membranes in waste water purification

253rd National Meeting (2017)

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