4.8 Article

Electric Field-Assisted Nanofiltration for PFOA Removal with Exceptional Flux, Selectivity, and Destruction

Journal

ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume -, Issue -, Pages -

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acs.est.2c04874

Keywords

electric field; nanofiltration; PFAS; rejection; degradation

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Due to the inability of widely used removal processes to destroy PFAS, this study applies an electric field in a crossflow membrane system to assess the performance of PFOA rejection, water flux, and energy consumption. The electric field-assisted nanofiltration design achieved a high PFOA rejection rate of 97% and a water flux of 68.4 L/m2 hr, requiring low electrical energy consumption of 7.31 × 10-5 kWh/m3/order.
Per-and polyfluoroalkyl substances (PFAS) pose significant environmental and human health risks and thus require solutions for their removal and destruction. However, PFAS cannot be destroyed by widely used removal processes like nanofiltration (NF). A few scarcely implemented advanced oxidation processes can degrade PFAS. In this study, we apply an electric field to a membrane system by placing a nanofiltration membrane between reactive electrodes in a crossflow configuration. The performance of perfluorooctanoic acid (PFOA) rejection, water flux, and energy consumption were evaluated. The reactive and robust SnO2-Sb porous anode was created via a sintering and sol-gel process. The characterization and analysis techniques included field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ion chromatography, mass spectroscopy, porosimeter, and pH meter. The PFOA rejection increased from 45% (0 V) to 97% (30 V) when the electric field and filtration were in the same direction, while rejection capabilities worsened in opposite directions. With saline solutions (1 mM Na2SO4) present, the induced electro-oxidation process could effectively mineralize PFOA, although this led to unstable removal and water fluxes. The design achieved an exceptional performance in the nonsaline feed of 97% PFOA rejection and water flux of 68.4 L/m2 hr while requiring only 7.31 x 10-5 kWh/m3/order of electrical energy. The approach's success is attributed to the proximity of the electrodes and membrane, which causes a stronger electric field, weakened concentration polarization, and reduced mass transfer distances of PFOA near the membrane. The proposed electric field-assisted nanofiltration design provides a practical membrane separation method for PFAS removal from water.

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