Destrucción electroquímica de ácido perflurooctanoico (PFOA) mediante electrodos de diamante

Abstract

Perfluorooctanoic acid (PFOA C7F15COOH) is a persistent organic pollutant that is non biodegradable. PFOA is also recalcitrant to the common physical-chemical treatments due to the high strength of the C-F bond. In this work, aqueous solutions with an initial concentration of 100 mg/L of PFOA were electrooxidized in an undivided electrochemical cell provided with ultrananocrystalline diamond (UNCD) anode and Nb cathode. The influence of the main operation variables was experimentally studied: i) the applied current density in the range 50-200 A/m2; ii) the temperature in the range 20-40ºC ; iii) the flowrate through the cell, in the range 2.4- 10.3 l/min; and iv) the electrolyte composition, NaClO4 and Na2SO4. High degrees of PFOA degradation (> 94%) and mineralization (>90 %) were observed. The PFOA degradation kinetics was strongly influenced by the applied current density. Two kinetic regimes have been identified: for low applied current density, the oxidation of PFOA follows zero order kinetics and the direct transfer of electrons on the anode surface limits the kinetics of degradation; for high applied current density, the process follows first order kinetics and the improved generation of hydroxyl radicals enhances the oxidation kinetics. The reproducibility of new commercial UNCD electrodes was also analyzed using two electrodes from different batches at several current densities.