Decomposition of Perfluorooctanoic Acid in Water Using Multiple Plasma Generation

Perfluorooctanoic acid (PFOA) can be decomposed using dc plasma generated within gas bubbles in water. However, the decomposition rate is extremely reduced by increasing the amount of treatment solution, because PFOA is decomposed only on the gas-liquid interface of the bubbles. In this paper, we carried out the degradation of PFOA using multiple plasma sources. A sawtooth-wave voltage was applied to a speaker to generate a pressure wave in a reactor and control bubble formation. Then, a pulsed voltage synchronized with the bubble formation was applied to the reactor to generate multiple plasmas within the bubbles. For the treatment of a 200-mL PFOA solution at an initial concentration of 44.9 mg/L, 10 plasmas were generated. The PFOA concentration decreased to 5.00 mg/L after 140 min, while exhibiting the same decomposition efficiency as a conventional single plasma.