Carbon-encapsulated MnFe2O4 nanoparticles: effects of carbon on structure, magnetic properties and Cr(VI) removal efficiency

In this work, the influences of carbon on structure, magnetic properties and Cr(VI) absorption efficiency of carbon-encapsulated MnFe 2 O 4 nanoparticles (MFO/C NPs) are studied. SEM images indicate that the fabricated MnFe 2 O 4 nanoparticles (MFO NPs) are enveloped by carbon layers, forming encapsulating structure. By the BET analysis, it is demonstrated that the average specific surface area of MFO/C samples is higher than that MFO sample. From FTIR and XPS spectra, the presence of carbon-coated MnFe 2 O 4 nanoparticles is confirmed. It is found that the Cr(VI) absorption efficiency of the MFO/C NPs first increases to reach the maximum value at 5% C concentration, and then decreases with the further increment of C concentration. The maximum absorption efficiency and capacity of 90.1% and 73.26 mg/g are obtained, respectively. Finally, a removal mechanism for the removal of Cr(VI) is proposed. The obtained results demonstrate that the carbon-encapsulated MnFe 2 O 4 NPs is a promising candidate as an advanced absorbent for the removal of Cr(VI) from wastewater.