ADSORPTION OF WATER FROM CD(II) IONS WITH MAGNETO-SENSITIVE NANOADSORBENT FE3O4/HYDROXYAPATITE

Abstract

In Ukraine, the problem of combating the consequences of natural pollution of the environment, natural water bodies and soils, as well as food products, in particular drinking water, is more acute than ever. Contaminants of military origin (remnants of shells, equipment, weapons, etc.) also pose a potential danger. Extremely harmful pollutants are ions of heavy metals, such as Ferrum, Copper, Manganese, Cadmium and others. The accumulation of such pollutants in the body of living beings leads to various pathologies, the development and strengthening of diseases. One of the reasons for such an impact of heavy metal ions on living organisms is that they are quite difficult to remove from the body, which only exacerbates the problem. In accordance with the EU Directive “Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the quality of water intended for human consumption”, drinking water, for which the standards for the content of heavy metals have been adopted, is recognized as one of the important food products, in particular cadmium, and other pollutants (dyes, pesticides, herbicides, etc.). In order to study the possibility of adsorption extraction of Cd(II) ions from aqueous solutions, the synthesis of sol-gel magnetite was carried out by the Elmore co-precipitation method. The synthesized samples were examined by TEM-microscopy methods and it was established that Fe3O4 particles are spherical in shape, prone to the formation of aggregates. The size of the crystallites is 3–23 nm. The magnetite surface was modified with hydroxyapatite in order to obtain a magnetically sensitive nanoadsorbent for the extraction of Cd(II) ions. With the help of TEM, it was established that there is no influence of magnetite surface modification on the size and morphology of the particles. A comparative analysis of the adsorption of Cd(II) ions from aqueous solutions by Fe3O4 and Fe3O4/hydroxyapatite surfaces was carried out. It was established that the degree of extraction of more than 60.0% of Cd(II) ions from an aqueous solution in the range of pH = 7.9–8.1 at a temperature of 293 K is achieved in the first 60–90 minutes from the beginning of the adsorbate – adsorbent contact. The adsorption equilibrium at the separation boundary for both surfaces is satisfactorily described by the pseudo-second-order model. It was determined that the adsorption capacity is 21.1 and 22.3 mg/g for Fe3O4 and Fe3O4/hydroxyapatite surfaces, respectively. It is shown that the adsorption isotherms are satisfactorily described by the Langmuir model, which indicates monomolecular adsorption of Cd(II) ions on energetically homogeneous surface centers.