High
Performance Nanofiltration Membrane for Effective
Removal of Perfluoroalkyl Substances at High Water Recovery
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Abstract
We
demonstrate the fabrication of a loose, negatively charged nanofiltration
(NF) membrane with tailored selectivity for the removal of perfluoroalkyl
substances with reduced scaling potential. A selective polyamide layer
was fabricated on top of a poly(ether sulfone) support via interfacial
polymerization of trimesoyl chloride and a mixture of piperazine and
bipiperidine. Incorporating high molecular weight bipiperidine during
the interfacial polymerization enables the formation of a loose, nanoporous
selective layer structure. The fabricated NF membrane possessed a
negative surface charge and had a pore diameter of ∼1.2 nm,
much larger than a widely used commercial NF membrane (i.e., NF270
with pore diameter of ∼0.8 nm). We evaluated the performance
of the fabricated NF membrane for the rejection of different salts
(i.e., NaCl, CaCl<sub>2</sub>, and Na<sub>2</sub>SO<sub>4</sub>) and
perfluorooctanoic acid (PFOA). The fabricated NF membrane exhibited
a high retention of PFOA (∼90%) while allowing high passage
of scale-forming cations (i.e., calcium). We further performed gypsum
scaling experiments to demonstrate lower scaling potential of the
fabricated loose porous NF membrane compared to NF membranes having
a dense selective layer under solution conditions simulating high
water recovery. Our results demonstrate that properly designed NF
membranes are a critical component of a high recovery NF system, which
provide an efficient and sustainable solution for remediation of groundwater
contaminated with perfluoroalkyl substances