A self-sufficient electro-Fenton system with enhanced oxygen transfer for decontamination of pharmaceutical wastewater

Abstract

The need for extra iron catalyst, limited selectivity of the oxygen reduction reaction (ORR) to produce H2O2, and harsh pH applicability still plague the electro-Fenton (EF) process. To alleviate these concerns simultaneously, a novel self-sufficient EF system was constructed, in which the newly fabricated Fe, N and S co-doped cathode was aerated via microporous aeration and a greater number of cathodes was utilized. Results indicated that the prepared cathode achieved a high H2O2 accumulation (15.60 ± 0.16 mg L−1 cm−2) coupled with nearly 90% H2O2 selectivity. The microporous aeration tube, which delivered microbubbles and changed the diffusion direction to supply more O2 to the electrode active sites, is beneficial to the H2O2 formation. Apart from its high H2O2 accumulation, the proposed system was set up to automatically reduce the bulk pH by regulating different current densities on electrodes. The proposed EF system was employed to treat real pharmaceutical wastewater, in which ·OH, 1O2, ·O2− and Fe(IV) were the main active species. Finally, an improvement of BOD5/COD values after EF treatment was a good indicator to confirm the feasibility of the developed system as a pretreatment prior to the subsequent engineering applications.