Cobalt Ferrite Nanospheres as a Potential Magnetic Adsorbent for Chromium(VI) Ions.

In the present work the cobalt ferrite nanospheres (CFO NS) were prepared via one-step, template-free solvothermal method and used as a magnetic adsorbent of chromium(VI) ions. The synthesized materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). The XRD results confirmed the cubic spinel structure of CFO NS while the SEM revealed sphere-like morphology with diameters of the CFO NS in the range of 100-300 nm. TEM images showed that each NS is composed of smaller CFO nanoparticles with size around 7-8 nm. The magnetic measurements revealed ferromagnetic character of CFO nanospheres with the maximum saturation magnetization and coercivity of 75 emu/g and 677 Oe, respectively. The synthetized CFO NS were tested as an adsorption material for removal of chromium(VI) ions from aqueous solution. The obtained removal efficiency is in the range from 38 to 88%. The results suggest that the adsorption capacity of CFO NS strongly depends on conditions of the solvothermal synthesis.