Sulfite activation by water film dielectric barrier discharge plasma for ibuprofen degradation: efficiency, comparison of persulfate, mechanism, active substances dominant to pathway, and toxicity evaluation

Herein, we proposed sulfite [S(IV)] activation by water film dielectric barrier discharge plasma (WFDBD) to produce ·SO4- to improve the removal efficiency of ibuprofen (IBP). The results show that the WFDBD/S(IV) system can significantly improve the removal rate of IBP by 22.3% compared with the WFDBD plasma system alone. Compared with persulfate (PS), a small amount of S(IV) can present a high degradation promotion, and S(IV) instead of PS can indeed reduce cost consumption. The active substances including ·OH, ·SO4-, 1O2, and ·O2–, were detected by electron paramagnetic resonance (ESR), and the quenching agents were added to verify the important role and contribution of the above active substances in the degradation of IBP. The degradation of IBP consumes H2O2, O3, ·OH, and ·SO4- in WFDBD/S(IV) system. Through liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) simulation, the degradation pathway of IBP and the role of active substances in the degradation process were inferred. Subsequently, by ECOSAR calculation and seed detection toxicity, it was found that the toxicity was significantly reduced after treatment with WFDBD/S(IV) system. The increase in input power, duty cycle, and solution flow rate all has a positive impact on the degradation of IBP, and IBP degrades better under acidic conditions. Finally, by treating different organic compounds and actual wastewater, it was found that inorganic ions have an impact on the WFDBD/S(IV) system, but the selectivity of the system is low and it has good effects on the treatment of domestic wastewater.