Electrochemical oxidation of perfluorooctanoic acid (PFOA) using graphite substrate lead dioxide (GSLD) as anode: Investigating reaction mechanism, degradation byproducts and influences of process parameters

The research examines the degradation of perfluorooctanoic acid (PFOA) through the electrochemical advanced oxidation process (EAOP). A graphite substrate lead dioxide electrode (GSLD) was used as anode material. The GSLD anode was prepared by depositing a lead dioxide layer onto a graphite plate. FESEM-EDX analysis revealed morphological alterations accompanied by a compositional peak resulting from the deposition of lead on the graphite anode. XRD analysis revealed the prevalence of tetragonal beta-PbO2 over orthorhombic alpha-PbO2, suggesting higher conductivity during the oxidation process. XPS analysis revealed the deposition of Pb(IV) and Pb (II) oxides over the surface of the anode. The oxygen evolution potential of the anode was obtained as 1.85 V (vs. SHE) using linear sweep voltammetry (LSV). Various operational parameters, including pH, current density, initial concentration, electrode spacing, and supporting electrolyte, were systematically altered to assess their influence on the degradation process. It was observed that at an optimized condition of pH 3 ( f 0.25), current density of 30 mA cm-2, and electrode spacing of 2 cm, the degradation of PFOA reached approximately 80 % after 2 h of electrolysis. The second-order hydroxyl radical rate constant with PFOA was determined by competition kinetics with para-chlorobenzoic acid (pCBA) as a probe compound. Additionally, the byproducts produced upon degradation of PFOA were identified using HR-MS analysis, which showed an increased potential for biodegradation. The potential degradation pathway was also investigated.