Electrochemical advanced oxidation of PFOA by Ti4O7 reactive electrochemical membrane anode

In recent years, per and polyfluoroalkyl substances (PFAS) have garnered significant attention due to their persistent and harmful effects on the environment and human health. Traditional treatment methods often fall short of effectively removing PFAS from water, prompting the need for innovative techniques. One promising approach is electrochemical advanced oxidation, based on highly reactive chemical species generated through electrochemical reactions to degrade organic pollutants. In this study, a specific reactive electrochemical membrane (REM) anode was used to degrade perfluorooctanoic acid (PFOA). The anode is a tubular Ti4O7-based REM (mixture of Ti4O7 and Ti5O9 Magneli phases) with a water permeability of 3300 L m- 2 h- 1 bar- 1. The impact of various operating parameters, including current density, flux through REM, and feed concentration, on PFOA degradation efficiency was investigated. It was found that higher current densities, feed concentrations and lower flux through REM led to increased PFOA removal rates. With this type of REM, a total degradation of PFOA was observed at PFOA flux (passing throw the REM) under 0.2 g h- 1 m- 2 even at the lowest current density (71 A/m2). The degradation mechanism was investigated by evaluating the generated by-products after several degradation cycles, and the results confirmed that the degradation occurs via the decomposition cycle of CF2. Energy consumption has been taken into account, as it is the major limitation of advanced oxidation processes, exhibiting value under 5 kWh/g for the lowest current density and the highest PFOA flux. The originality of this study relies on the use of a specific anode; a tubular shape Ti4O7-based REM (by Saint Gobain Company). Such concentric REM reactor is optimal for the treatment of recalcitrant effluent containing PFOA as it significantly improved mass transfer leading to a very interesting energy efficient system that can easily be scale up.