Green synthesis, structure, cations distribution and bonding characteristics of superparamagnetic cobalt-zinc ferrites nanoparticles for Pb(II) adsorption and magnetic hyperthermia applications

A simple green method for the synthesis of cobalt-zinc ferrites nanoparticles has been proposed. XRD, SEM/EDX, TEM, Mossbauer and FTIR techniques have been applied to investigate structure and morphology of the obtained spinel ferrites. Analysis of the cation distribution showed that during the transition from cobalt ferrite to zinc ferrite the inversion degree of the Fe cations decreases from delta = 0.89 to delta = 0.00. IR spectra show the presence of characteristic peaks of the M-A-O (at similar to 450 cm(-1)) and M-B-O (at similar to 610 cm(-1)) vibrations as well as the vibrations of functional groups of the honey residuals. It was concluded that honey acts as reductant and stabilizer preventing agglomeration of the nanoparticles. The force constants of the tetrahedral and octahedral bonds have been calculated. Dependence of the Debye temperature on Zn content was also established for the first time: it is increased from 782 K to 805 K with Zn increasing. It was shown that the ZnFe2O4 sample exhibits the highest adsorption capacity (289 mg/g) towards lead cations. This result is explained in terms of surface acidity of the examined samples, estimated from the variations of the ionic-covalent bond parameter. The Langmuir, Freundlich and Dubinin-Radushkevich models were tested to evaluate the adsorption mechanism. The efficiency of heat release by the CoxZn1-xFe2O4 magnetic nanoparticles for magnetic hyperthermia was investigated as well. The registered induction heating curves depend on the Zn content in the CoxZn1-xFe2O4 samples. The sample with x(Zn) = 0.6 exhibits the maximal specific loss power equal to 2.56 W/g. The intrinsic loss power (ILP) value is 0.40, and is 2.7 times higher than the ILP value of commercial Fe3O4. The obtained ferrite materials can be, therefore, used in magnetic hyperthermia applications and Pb(II) adsorption. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A simple green method for the synthesis of cobalt-zinc ferrites nanoparticles was proposed in this study, with detailed structural and morphological analysis conducted using various techniques. The samples exhibited high adsorption capacity and magnetic hyperthermia performance, making them promising for potential applications in these fields.