High electron transfer rate and efficiency on Fe0 modified by sulfidation and pre-magnetization for carbamazepine degradation by heterogeneous electro-Fenton in wide pH ranges

The coupling of sulfidation and pre-magnetization was for the first time applied for micron-Fe0 modification to obtain pre-S/Fe0 particle and tested as a highly active and recyclable catalyst for heterogeneous electro-Fenton (EF) degradation of carbamazepine (CBZ), observing the rate constant of this pre-S/Fe0-EF process was enhanced 11.9 times compared to conventional Fe0-EF process. Especially it performed well in wide pH ranges (3–9), all achieving the complete removal of CBZ of initial concentration of 5.0 mg L-1 within 60 min at current 50 mA and optimum dose of 56 mg L−1 pre-S/Fe0, although the removal rate constant decreased obviously when pH ≥ 5. Density functional theory (DFT) calculations illustrated that electrons were more easily transferred from the inner Fe0 to the surface through FeS rather than Fe3O4. Tafel curve proved the enhanced corrosion rate of S/Fe0 after pre-magnetization. Electron paramagnetic resonance (EPR) analysis and radical quenching experiments certified the role of •OH, •O2– and 1O2. Eight consecutive runs experiment and the treatment of other typical organic pollutants proved the excellent stability and wide application of pre-S/Fe0-EF process. Besides, the CBZ degradation and mineralization in three real wastewaters by pre-S/Fe0-EF process also illustrated better performance and relatively low electric energy consumption when compared with that of Fe0-EF process. Overall, this study provides a new approach for improving heterogeneous Fe0-based EF process for highly efficient degradation of refractory pollutants in wide pH ranges.