Decomposition of Perfluorinated Compounds in Water by DC Plasma within Oxygen Bubbles

Complete decomposition of perfluorooctanoic acid (PFOA) at a concentration of 41.4 mg/L and perfluorooctane sulfonate (PFOS) at a concentration of 60 mg/L in water was successfully completed by DC plasma within oxygen bubbles. PFOA and PFOS were decomposed completely after 3-h operation and 8-h operation, respectively. The decomposition efficiency was evaluated by measuring the amounts of fluorine ions that were detached from PFOA and PFOS in the solution. As indicated by the measurement of LC/MS, the main byproducts generated during the plasma treatment turned out to be perfluorocarboxylic acids. For practical application, 2-parallel operation of DC plasma was also demonstrated as a basic technology for a large capacity reactor. The decomposition efficiency of 2-parallel operation was at the same level as that of single operation.