Magnetic and Optical Properties of CoFe2O4 Nanoparticles Synthesized by Reverse Micelle Microemulsion Method

CoFe2O4 nanoparticles were successfully synthesized by reverse micelle microemulsion method. The X-ray diffraction (XRD) results show that all samples have a spinel ferrite structure with calculated crystallite sizes in the range of 3.6–21.7 nm. Increasing calcination temperature from 650 to 900 °C can increase the crystallization of the powders. Transmission electron microscopy (TEM) images reveal the spherical shape of nanoparticles with serious agglomeration. Particle sizes of the samples calcined at 700, 800, and 900 °C estimated from TEM images are 9.7 ± 2.1, 10.6 ± 1.6, and 14.9 ± 0.4 nm, respectively. The UV–visible spectroscopy results show a decrease in the energy band gap (Eg) from 4.3 to 3.0 eV with increasing crystallite size. The room temperature magnetic properties of the calcined CoFe2O4 nanoparticles performed by vibrating sample magnetometry (VSM) indicate ferrimagnetic behavior in all samples. In addition, the specific magnetizations measured at the maximum field of ±30 kOe (Mmax) and coercivity (Hc) are increased with increasing calcination temperature. These characteristics of the prepared CoFe2O4 nanoparticles make them a promising magnetically separable photocatalyst for wastewater treatment.