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

Complete decomposition of perfluorooctanoic acid (PFOA) at a concentration of 41.4mg/L and perfluorooctane sulfonate (PFOS) at a concentration of 60mg/L in water was successfully demonstrated by DC plasma within oxygen bubbles. PFOA and PFOS were decomposed completely after 3-hour operation and 8-hour operation, respectively. The decomposition efficiency was evaluated by measuring the amounts of fluorine ions which were detached from PFOA or PFOS in the solution. From the measurement of LC/MS, the main by-products generated during the plasma treatment turned out to be perfluorocarboxylic acids. For the 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.