Fe3O4-MWCNT magnetic nanocomposites as efficient peroxidase mimic catalysts in a Fenton-like reaction for water purification without pH limitation

The Fenton-based reaction is powerful enough to decompose refractory organic pollutants, but it is limited by having a low pH range and it is necessary to have a secondary disposal of the iron sludge. This study demonstrates that Fe3O4-multi-walled carbon nanotube (Fe3O4-MWCNT) magnetic hybrids can be used as an efficient peroxidase mimic catalyst that could overcome such pH limitations in a Fenton-like reaction and could be reused after a simple magnetic separation. The Fe3O4-MWCNT hybrid was prepared using a simple one-pot strategy via in situ growth of Fe3O4 magnetic nanoparticles onto the surface of the MWCNTs. In this process, MWCNTs act as an excellent dispersant, which ensures that the Fe3O4 is well dispersed. The Fe3O4-MWCNT hybrid was characterized by X-ray diffractometry, Fourier transform infrared spectrometer, thermogravimetric analysis and vibrating sample magnetometry, which indicated that the Fe3O4 nanoparticles were successfully deposited on to the surface of MWCNTs. Furthermore, it was revealed that the Fe3O4-MWCNTs could catalyze H2O2 decomposition by acting as a peroxidase mimic catalyst. Then heterogenous Fenton-like reactions were performed using the Fe3O4-MWCNT nanocomposites as a catalyst to degrade methylene blue (10.0 mg L-1; MB) in aqueous solution. The results showed that MB could be efficiently removed in a broad pH range of 1.0-10.0, with a degradation efficiency of 88.13% to 98.68% in two hours, and a highest total organic carbon removal efficiency of 35.6% in 12 hours. Furthermore, the magnetic nanocomposites exhibited an enhanced removal efficiency for MB compared with the Fe3O4 magnetic nanocomparticles and MWCNTs used individually. In addition, Fe3O4-MWCNT nanocomposites exhibited strong magnetism, and thereby could be easily separated from aqueous solution using an external magnetic field. Therefore, the as-prepared Fe3O4-MWCNT nanocomposites could be used as a promising and effective catalyst in Fenton-like reactions for the purification of MB polluted water in a wide pH range.