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

Abstract

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.