Thermodynamic and kinetic parameters of adsorption of heavy metals ions on magnetic composite sorbent

Abstract

Copyright © 2019 American Scientific Publishers. All rights reserved. The process of adsorption of Cr 6+ , Cu 2+ and Ni 2+ ions on the magnetic composite sorbent (MCS) that obtained by magnetite deposition on the surface of wood fiber waste was studied. The research of adsorption of the considered heavy metal ions (HMI) was carried out in a static mode in a neutral and acidic medium at temperatures of 288, 298, 308 K. It was found that with increasing temperature, the adsorption capacity MCS increases, that indicates the chemical nature of the forces holding HMI on the composite surface. The adsorption capacity of MCS decreases in an acidic medium, and when the temperature decreases. Adsorption capacities MCS were calculated and adsorption isotherms HMI were constructed based on the obtained data. The adsorption capacity for Cr 6+ ions was 1.47 mmol/g in a neutral medium at 298 K, for Cu 2+ ions—1.09 mmol/g, for Ni 2 + ions—0.60 mmol/g. It is determined that the Langmuir equation the best describes adsorption process with approximation coefficients R 2 more than 0.998. From the data of treatment of adsorption isotherms, it follows that the adsorption processes of HMI on MCS relate to the processes of chemical adsorption. Kinetic dependences were obtained under static conditions in a neutral medium at different temperatures. For determining the limiting stage of adsorption, the obtained experimental data are processed using different kinetic models: diffusion model, pseudo-first and pseudo-second order models. It is found that adsorption process the best describes a pseudo-second order model, that assumes that the chemical reaction of the exchange limits the adsorption process.