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-Fe-0 modification to obtain pre-S/Fe-0 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/Fe-0-EF process was enhanced 11.9 times compared to conventional Fe-0-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/Fe-0, 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 Fe-0 to the surface through FeS rather than Fe3O4. Tafel curve proved the enhanced corrosion rate of S/Fe-0 after pre-magnetization. Electron paramagnetic resonance (EPR) analysis and radical quenching experiments certified the role of (OH)-O-center dot, O-center dot(2)- and O-1(2). Eight consecutive runs experiment and the treatment of other typical organic pollutants proved the excellent stability and wide application of pre-S/Fe-0-EF process. Besides, the CBZ degradation and mineralization in three real wastewaters by pre-S/Fe-0-EF process also illustrated better performance and relatively low electric energy consumption when compared with that of Fe-0-EF process. Overall, this study provides a new approach for improving heterogeneous Fe-0-based EF process for highly efficient degradation of refractory pollutants in wide pH ranges.

Automated summary

In this study, the coupling of sulfidation and pre-magnetization was used for the modification of micron-Fe-0, resulting in pre-S/Fe-0 particles. These particles performed as highly active and recyclable catalysts for the degradation of carbamazepine using heterogeneous electro-Fenton process. The rate constant of the pre-S/Fe-0-EF process was significantly enhanced compared to conventional Fe-0-EF process, and it exhibited excellent performance in a wide pH range.