Electrochemical oxidation of concentrated perfluorooctanoic acid (PFOA) solutions that may be generated by ion exchange or foam fractionation was studied using Bi-doped SnO2 (BTO) deposited on a Ti4O7 reactive electrochemical membrane (REM). BTO was deposited on REMs using pulsed laser deposition (PLD) (BTO-PLD/REM) and electrodeposition followed by thermal oxidation (BTO-EDT/REM). Transmission electron microscopy analyses showed catalyst particle size ranging from 2.2 nm to 15.3 nm for the PLD method depending on the number of pulses used. By contrast, the EDT method produced much larger catalytic particles of ~ 1 micron in size. The electrodes fabricated by both catalyst deposition methods showed PFOA removal of &gt; 92% of a 100 mM feed solution at an anode potential of 4.2 V/SHE and a residence time of ~11s, which was significantly higher than the Ti4O7 REM. Analysis of the treated solutions by liquid chromatography-tandem mass spectroscopy (LC-MS/MS) showed the formation of shorter chained perfluoroalkyl substances (PFAS) carboxylates with carbon chain lengths of five to seven. The detected products support a sequential CF2 elimination mechanism during electrochemical oxidation. The experimental results were simulated by a reactive transport model, which allowed an estimation of kinetic parameters for electrochemical oxidation of PFAS.

Electrochemical oxidation of perfluorooctanoic acid using Bi-doped SnO2 deposited reactive electrochemical membranes

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