Decomposition of Perfluorooctanesulfonate (PFOS) by Multiple Alternating Argon Plasmas in Bubbles with Gas Circulation

H. Obo, N. Takeuchi, and K. Yasuoka

Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Japan

Abstract- Perfluorooctanesulfonate (PFOS) is used in a wide range of industrial applications, owing to its superior characteristics; however, its environmental persistence and biopersistence have become matters of concern, leading to the demand for decomposition treatments for industrial effluent containing PFOS. Although it is possible to decompose PFOS using direct current plasma generated within bubbles in water, low time and energy efficiencies arising from ballast resistance losses are major issues. This paper reports on the development of a reactor for generating plasma, with the number of treatment holes increased from one (in previous studies) to 21. Decomposition of 1 L of PFOS in 1200 min was successfully completed using this reactor, with a mass balance of fluorine reaching 90% or more over time. Furthermore, loss of ballast elements, which are used to stably generate electrical discharge, was significantly reduced by switching from resistors to capacitors. The exhaust gas from the reactor was recirculated through the treatment holes to successfully reduce the gas consumption flow rate to approximately 10% that of conventional systems.

Keywords-Perfluorooctanesulfonates (PFOS), plasma, water treatment, organic fluorine

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