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 MnO and 16% of FeO. Transmission electron microscopy image shows an aggregate of MnO 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/m, 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 MnO in the composite. The hysteresis curve of the composite MnO/FeO has changed when compared to the pure magnetite; however, the coercive field after the addition of manganese oxide remains unaltered and does not change with a value around 158 Oe. 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.
What differentiates the nano materials from the others is that they allow enhancing physical and chemical properties in extremely low concentrations, giving new characteristics to a given product, which in the past was not possible. This range of properties is basically due to the fact that these structures have nanometric dimensions, resulting in a high surface area, a greater degree of dispersion and functionalities that depend on the size of the structure. The nanotechnology research that is being developed in the country indicates that business opportunities arise at first in the cosmetics, chemicals from the chemical industry (catalysts, paints, coatings) and petrochemicals, plastics, rubbers and metal alloys.
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