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High Performance Nanofiltration Membrane for Effective Removal of Perfluoroalkyl Substances at High Water Recovery

Chanhee Boo, Yunkun Wang, Ines Zucker, Youngwoo Choo, Chinedum O. Osuji, Menachem Elimelech
Environmental science & technology 2018 v.52 no.13 pp. 7279-7288
calcium, calcium chloride, cations, gypsum, molecular weight, nanofiltration, nanopores, organochlorine compounds, perfluorocarbons, perfluorooctanoic acid, piperazine, polyamides, polymerization, remediation, sodium chloride, sodium sulfate
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, CaCl₂, and Na₂SO₄) 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.