Magnetized manganese oxide nanocomposite

In this study, a composite with magnetic properties has been successfully synthesized by a novel and environmentally friendly route and is applied to Cd(II) adsorption for water decontamination. The quantification of the phases obtained by Rietveld refinement has shown the presence of 84% of Mn3O4 and 16% of Fe3O4. Transmission electron microscopy image shows an aggregate of Mn3O4 nanoparticles without specific orientation and the predominance of octahedral morphology with nanoparticles size estimated around 25–30 nm. The Cd(II) adsorption isotherm is fitted using the Langmuir–Freundlich model. The estimated maximum adsorption capacities of Cd(II) at pH 6 and 7 are similar (0.28 ± 0.02 and 0.31 ± 0.02 mg/m², respectively). The kinetic results show that the studied system follows the pseudo-second-order model. The Raman results indicate that Cd is being specifically adsorbed by the Mn3O4 in the composite. The turbidity tests showed that the magnetic sedimentation was efficient and promising for wastewater treatment in large scale. These materials can be conveniently recovered by magnetic separation, avoiding the filtration steps, which will make easier the solid–liquid separation operation that follows the adsorption process.