Investigation of the adsorption of the tetracycline antibiotic by NiFe2O4 and CoFe2O4 nanoparticles

Tetracycline is a bacteriostatic antibiotic with stable chemical composition, which difficults its degradation in the environment. The presence of this antibiotic in the aquatic environment can cause toxic effects and potential development of resistant bacteria. In this work, the structural and magnetic properties of NiFe2O4 and CoFe2O4 nanoparticles and their applications in tetracycline adsorption were investigated. Ferrites were synthesized by coprecipitation, heat treated at 623 K for 2 h and characterized by thermogravimetric analysis, X-ray diffractometry, Fourier transform infrared spectroscopy, Mössbauer spectroscopy, vibrating sample magnetometry, electrophoretic light scattering and gas adsorption. The experimental data confirmed the formation of the partially inverse spinel phase of NiFe2O4 and CoFe2O4, with crystallite sizes of 6 and 4 nm, respectively, superparamagnetic behavior, low saturation magnetization and coercivity, isoelectric point close to pH 7 and mesoporous structure. NiFe2O4 exhibited better performance in the adsorption of tetracycline (50 mgTCN.g-1NiFe2O4 and 96% removal) at pH 7. FTIR and XPS spectroscopy measurements indicate that the main adsorption mechanism is hydrogen bonding.