APPLICATION OF ADSORPTION MODELS FOR DESCRIPTION OF BALANCES IN THE SYSTEMS «CATIONS OF COPPER (II) AND LEAD (II) – NATURAL MATERIALS OF ASTRAKHAN REGION »

Abstract

I In the work there were studied the regularities of extracting copper (II) and lead (II) cations from aqueous solutions with the help of natural sorbents from the Astrakhan region such as the marl of the Baskunchak deposit, the Kamennyy yar deposit and the clay of the Volzhsky deposit. A comparative study was made of the applicability of the adsorption models of Langmuir, Freindlich, Temkin, and Dubinin-Radushkevich to describe the experimental adsorption isotherms of these cations on the surface of aluminosilicates. The constants and parameters of the equations corresponding to these models are determined. A comparison of the regression coefficients shows that the Temkin model is suitable for describing the adsorption equilibria in the "M2+ -clay" systems. The Freundlich model most adequately describes the experimental data on adsorption in the "M2+ -marl/opoka" systems, which reveals the heterogeneous surface of both of these materials with a large number of energetically dissimilar active centers. The regression coefficients found in this case by the Langmuir model are small; the boundary conditions for the description of systems with a monomolecular coating are not observed. The Dubinin-Radushkevich model was also used to describe the process of concentrating lead (II) compounds on the marl surface of the Baskunchak deposit and the Kamennyy Yar deposit. The calculated values of the free energy of adsorption were 11.2 (opoka) and 4.17 kJ/mol (marl). The process of fixing lead cations on these natural sorbents in the Astrakhan region proceeds according to the ion-exchange mechanism. The adsorption activity of Cu2+, Pb2+ ions on the surface of sorbents is confirmed by the calculated values of Gibbs energy and entropy. The endothermic nature of the processes taking place with the participation of the clay of the Volzhsky deposit and the Kamennyy Yar deposit is explained by the considerable energy expenditure for the dehydration of the surface groups of sorbents. For citation: Dzhigola L.A., Sadomtseva O.S., Shakirova V.V., Kargina K.V., Syutova E.A., Razgovorov P.B., Nagornov R.S. Application of adsorption models for description of equilibria in systems cations of copper (II) and lead (II) – natural materials of Astrakhan region. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 105-112