PROCESSES OF SORPTION OF IONIC FORMS OF NICKEL(II) FROM AQUEOUS SOLUTIONS BY NANOSIZED MAGNETITE

Abstract

At the current stage of development of science and industry, environmental pollution, in particular water bodies, is considered one of the most important global problems of mankind. In particular, one of the key goals for 2030 in the EU countries is to guarantee accessibility and long-term provision of water supply and sanitation for all, as stated in the sixth goal of sustainable development (SDG), therefore, the search for effective methods of purifying water to a drinking state remains an urgent issue of today. In this work, the synthesis of nanosized magnetite sol-gel by the Elmore method was performed. The Fe3O4 phases were identified by X-ray spectroscopy methods. The average size of magnetite particles was calculated by the Scherrer method to be 75.93 nm. It was determined that the degree of extraction of ionic forms of Nickel(II) from aqueous solutions of 57.5 % is achieved during the first 40–50 minutes from the beginning of contact between the components. Sorption equilibrium occurs within 60 minutes from the beginning of contact at the interface. It is shown that the kinetics of sorption of ionic forms of Nickel(II) from a solution by the magnetite surface can be described by the pseudo-second-order Ho-McKay model, which indicates interparticle interaction between sorbate ions at the phase interface due to intermolecular forces. It was established that the character of the isotherm curve resembles the Langmuir isotherm curves (L2-type) according to the Giles classification with saturation, and the sorption capacity is 19.2 mg/g. It is shown that the adsorption isotherm of ionic forms of Nickel(II) is satisfactorily described by the Langmuir model, in comparison with other models, which can be seen from the value of the correlation coefficient (R2 = 0.997), i.e. the adsorption of ionic forms of Nickel(II) occurs on homogeneous (homogeneous) centers of the magnetite surface, where all active centers are energetically homogeneous and only a monomolecular layer of sorbate can form on the surface. The calculated adsorption energy according to the Dubinin-Radushkevich equation for the adsorbent surface does not exceed 2 kJ/mol, which indicates the physical adsorption of ionic forms of Nickel(II) from aqueous solutions by the magnetite surface.