Magnetic Characterization of Co and Zn Nano Ferrites: Property Consideration for Oil-Spill Clean Up

Abstract

Nano-magnetic particles are significantly finding applications in environmental remediation. This work studied the magnetic properties of Co and Zn nano-ferrites, CoFe2O4 and ZnFe2O4 respectively, with considerations for the properties that are desirable for oil spill cleanup. The ferrite nanoparticles were synthesized by the glycol-thermal method at 200 ºC for 6 hours using a stirred pressure reactor. Single phase spinel crystal structures were obtained for both samples as determined by an X-ray diffraction (XRD) machine. The high-resolution transmission electron microscope and surface electron microscope images showed nano structures. The magnetic properties and magnetic hyperfine parameters were determined using a lakeshore vibrating sample magnetometer and 57Fe Mössbauer spectroscopy. The XRD peaks were consistent with that of a single phase spinel structure. No impurity phase was detected. The nano-ferrites have crystallite sizes of about 10 nm and 17 nm for CoFe2O4 and ZnFe2O4. The nano almost-spherical nature of the samples was also confirmed from their morphology studies. The saturation magnetization of CoFe2O4 and ZnFe2O4 were about 50 emu/g and 30 emu/g respectively. They both exhibited superparamagnetic properties with a component of para-magnetism observed in ZnFe2O4 nano-ferrites. CoFe2O4 nano-ferrites exhibited better desired property for oil spill cleanup. The ZnFe2O4 nano-ferrites showed tendencies of slow response to magnetic field, however, it is more environmentally friendly. The magnetic hyperfine parameters and the isomer shift values for CoFe2O4 and ZnFe2O4 showed strong internal magnetic fields and the obtained values are consistent with spinel structure. The oxidation state of Fe was observed to be Fe3+. Due to the low coercivity and high magnetization values, these particles could be considered as potential candidates for oil spill cleanup. These desirable magnetic properties will improve the recyclability of the nanoparticles using low applied magnetic fields.