Nanoparticle-embedded hydrogel synthesized electrodes for electrochemical oxidation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)

Abstract

In this study, sliver (Ag) and gold (Au) nanoparticles (NPs) were embedded on poly (acrylic acid) (PAA)/poly (allylamine) hydrochloride (PAH) hydrogel fibers for improved electrochemical oxidation (EO) of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal. The NPs-loaded PAA/PAHs shows the better charge transport compared to the ceramic nanofiber membranes (CNM) electrodes. At 10 mA cm−2 of current density, the Ag-PAA/PAH electrodes showed a faster removal of PFAS compared to the Ag-CNM electrode probably due to large surface area-volume ratio and high porosity from the hydrogel. Among NPs-loaded PAA/PAH electrodes, the Ag/Au-PAA/PAH electrodes showed the highest removal of PFOA (72%) and PFOS (91%) in 2 h with the maximum removal rate of PFOA (0.0046 min−1) and PFOS (0.0093 min−1). The rapid PFOS removal is possibly due to the high activity of electron transfer with a higher redox potential of SO4•- than •OH. The highly stable F− generation was obtained from each electrode during reproducibility (n = 3). The net energy consumption from Ag/Au–PAA/PAH electrode was 164.9 kWh m−3 for 72% PFOA removal and 90 kWh m−3 for 91% PFOS removal, respectively. The developed Au-PAA/PAH electrodes were applied to lake water samples and showed acceptable PFOS removal (65%) with relative standard deviations (RSD) of 10.2% (n = 3) at 10 mA cm−2 of current density. Overall, the NP-embedded hydrogel nanofibers were proven to be a promising sustainable catalyst for the electrochemical PFAS oxidation in water.