Per-and polyfluoroalkyl degradation in a hybrid dielectric barrier discharge plasma and electrooxidation system through involving more reactive species by air and water circulation

Abstract

The presence of PFAS in water matrices has become a global environmental issue in the last half-century. Dielectric barrier discharge (DBD) and electrooxidation (EO) showed potential for PFAS degradation but have yet to find practical application due to relatively high energy consumption. In this study, a hybrid DBD-EO system for efficient degradation of PFAS was developed by involving more reactive oxygen, sulfate radicals (${\mathrm{SO}}_4^{\mathrm{•}-}$) and nitrogen species (RONS). The results showed that using the hybrid DBD-EO system under optimal conditions (applied voltage = 6 kV and current density = 7.5 mA/cm²) could increase PFOA degradation efficiency from 65.0% (DBD) and 62.5% (EO) to 89.14%. While the EE/O decreased from 67.0 kWh/m³ (DBD) and 47.82 kWh/m³ (EO) to 21.61 kWh/m³. In addition, the effect of operational parameters and water matrices revealed that the hybrid DBD-EO system had high potential for PFOA removal from water under various conditions. According to the EPR and DFT calculation results, integration of reactive species in EO (${\mathrm{SO}}_4^{\mathrm{•}-}$, ^•OH, ${\mathrm{O}}_2^{\mathrm{•}-}$) and ONOOH) and DBD (^•OH, ${\mathrm{O}}_2^{\mathrm{•}-}$, ${\mathrm{NO}}_2^{\mathrm{•}-}$, ¹O₂ and ONOOH) processes in the DBD-EO system led to efficient degradation of PFOA through a mechanism of decarboxylation/defluorination cycle. Our findings suggested the combination of DBD and EO is a promising approach for complete degradation of PFAS from water with low energy consumption and minimal environmental side effects.