Extraction of Hg2+ ions from aqueous solutions nanocomposites based on magnetite

Abstract

The aim of the work is to study the adsorption properties of nanosized magnetite (Fe3O4) and nanocomposites based on it capable of sorption of Hg2+ ions from aqueous solutions. The direction of research includes the synthesis of nanoscale single-domain magnetite as a magnetosensitive carrier, modification of its surface with a biocompatible coating. The following samples were synthesized for research: Fe3O4, Fe3O4/SiO2 and Fe3O4/DMSA (meso-2,3-dimercaptosuccinic acid), Fe3O4/SiO2/DMSA. Coatings known for their biocompatibility with the environment of a living organism were used to modify the surface of magnetite nanoparticles, in particular, tetraethoxysilane and DMSA. Adsorption of Hg2+ ions on the surface of magnetite and nanocomposites (NCs) was carried out in an aqueous medium in the concentration range С0 = 1,0 – 40,0 mg/l (g = 0,03 g, V = 5 ml, pH = 2,7 ) for 1 hour at room temperature. The concentration of Hg2+ ions before and after adsorption was determined photometrically in the form of monosubstituted dithizonate at a wavelength of 490 nm. The pHIIP value of the surface of the synthesized nanocomposites was determined, and the dependence of the sorption activity on the pH level and the isoionic point of the surface in the range of pH= 2 – 9 was established. To study the kinetics of sorption, a solution with a concentration of Hg2+ = 36 mg/l and pH = 2,7 was used, with a contact time of 15 – 180 minutes. The kinetics and isotherm of sorption were analyzed using kinetic equations and models that take into account the contribution of the chemical reaction to the sorption process. It was established that the kinetics of sorption of Hg2+ ions corresponds to the pseudo-second-order kinetic model. Sorption isotherms correspond to the Freundlich model. The obtained data can be useful in the creation of magnetically controlled sorption materials for the extraction of Hg2+ ions from aqueous solutions and biological fluids.