Pre-magnetized Fe as heterogeneous electro-Fenton catalyst for the degradation of p-nitrophenol at neutral pH.

Pre-magnetized Fe (Pre-Fe) was for the first time applied as heterogeneous catalyst to enhance the oxidation efficiency of electro-Fenton (EF) for the degradation of p-nitrophenol (PNP). The parameters including current, initial pH and pre-Fe dosage of Pre-Fe/EF process were optimized and compared with other two processes (conventional Fe/EF and electro-oxidation) to confirm its advantage. The rate constants of PNP removal were 1.40-3.82 folds of those by Fe/EF process under various experimental conditions. The application of pre-Fe as catalyst could extend the working pH range from 3.0 to neutral conditions for PNP removal and reduce the Fe dosage from 2 to 0.5 mM corresponding to Fe/EF, avoiding the second pollution of iron sludge. The superiority of Pre-Fe/EF process was also verified to improve the degradation and mineralization of other phenols and antibiotics. Furthermore, a possible pathway of PNP degradation was revealed by the identification of intermediates and organic acids, and the possible mechanism of pre-Fe efficiently enhanced the EF efficiency was proposed. This work demonstrated that such a novel heterogeneous EF process using pre-Fe catalyst was clean and promising for the degradation of refractory organic pollutants.