Development and Application of Different Non-thermal Plasma Reactors for the Removal of Perfluorosurfactants in Water: A Comparative Study

The degradation of perfluorosurfactants (PFS), particularly of PFOS, has been studied in dielectric barrier discharge (DBD) and nano-pulse corona discharge (PCD) reactors. DBD-plasma is generated in two different types of reactors. First, in a suitable falling film reactor with a planar configuration for the treatment of ca. 0.4 L PFS solution, and second, in a horizontal trough reactor for the treatment of ca. 8 L PFS contaminated water. For the comparison, the efficiency of PFS degradation by ozonation and photocatalytic ozonation processes were also examined using a similar falling film reactor, and it was found that these methods are not as efficient as the DBD plasma. The degradation of PFSs by non-thermal plasma was investigated in dependence on PFS concentration and gas atmosphere by HPLC/MS and ion chromatography. Concerning the energy yield, the nano-pulse corona is significantly more efficient than the DBD plasma. For an initial PFOS concentration of 10 mg/L the G50 of the PCD is about 200 mg/kWh, while it is less than 100 mg/kWh for the DBD reactor. Compared to the plasma in He atmosphere, in all reactors the decomposition of PFS under Ar atmosphere results in a deeper mineralization, which is expressed by fluoride recovery.