Chemisorption of estrone in nylon microfiltration membranes: Adsorption mechanism and potential use for estrone removal from water

Estrone is a representative steroid estrogen contaminant that has been detected in effluents from sewage treatment facilities, as well as in surface and ground waters. Our study shows that estrone can be readily removed from water via a unique chemisorption mechanism using nylon microfiltration membranes. Experiments on a laboratory in-line filtration system showed instant removal of estrone from 200 μg/l aqueous solutions by 0.45-μm nylon membranes (ca. 35 L per m2 membrane). Comparisons with 0.45-μm PVDF, PTFE and glass microfiber membranes suggested that the significant estrone adsorption in nylon membrane should be predominately driven by a different mechanism rather than common physical adsorption. Fourier transform infrared spectroscopy study on nylon membranes and a model compound, N-methylacetamide, showed that the significant adsorption originated from the hydrogen bonding between terminal –OH groups on estrone molecules and nucleophile –CO groups in amide groups of nylon 6,6. The saturated nylon membrane showed very low leachability in ambient water, while it could be effectively regenerated in alkaline or ethanol solutions. Preliminary reusability study showed that the membrane maintained a consistent adsorption capacity for estrone during ten cycles of reuse. The chemisorption-based polymeric adsorption may provide a new alternative approach for removing estrone and potentially other trace organic contaminants from water.

Chemisorption of estrone on nylon 6,6 via hydrogen-bonding in aqueous solutions.Figure optionsDownload high-quality image (59 K)Download as PowerPoint slideHighlights
► Instant removal of estrone from water via chemisorption on nylon 6,6.
► Adsorption driven by inter-molecular hydrogen bonding between estrone and nylon 6,6.
► Very low leachability in ambient water.
► Thorough membrane regeneration in ambient alkaline or ethanol solution.
► Consistent adsorption capacity for estrone during ten cycles of membrane reuse.