Removal of PFAS from aqueous solution using PbO2 from lead-acid battery

Abstract

Whilst advanced electrochemical oxidation can break down per- and polyfluoroalkyl substances (PFAS), the requirement for expensive electrode materials usually prevents its widespread application. Here we use an industrial material of lead peroxide (PbO2) from a lead-acid battery to break down PFAS including perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and 1H,1H,2H,2H-perfluorooctanesulfonic acid (6:2 FTS). By optimising the PbO2 panel (activating and doping) and working conditions including supporting electrolyte (1 L 10 mM Na2SO4), initial concentration (10 μM), temperature (room temperature), current density (5 A for a 10 cm × 10 cm PbO2 panel) etc., we successfully remove > 99% PFAS (individual PFAS monitored via HPLC-MS) whilst mineralising ∼59% PFOA (defluorination, F- released and monitored via F-ISE, fluoride-ion selective electrode). By studying the pseudo-first-order kinetics of the PFAS breakdown (0.0028-0.007 min-1) and defluorination (0.84-5.9 × 10-8 min-1), we assign the difference to the adsorption of PFAS on the PbO2 panel and the appearance of intermediates before the full defluorination. The leaked HF gas (∼10-5 M, collected using 0.25 L 0.1 M NaOH) and Pb2+ (∼12 μM, or ∼ 2.5 ppm) are also confirmed. This study employs an economic industrial material, highlights the contribution of adsorption towards the PFAS removal and breakdown, and identifies the possible leakage of secondary contaminants.