SORPTION EXTRACTION OF COBALT (II) BY DIOCTAHEDRAL SMECTITE FROM AQUEOUS SOLUTIONS
Rubrics: 1. CHEMISTRY
Authors:
1.
Mari State University
2.
Mari State University
3.
KNITU
Type:
Article
Pages:
from 19
to 23
Status:
Published
Received:
19.01.2026
Accepted:
25.01.2026
Published:
26.02.2026
Language:
Russian
Keywords:
SORPTION, COBALT(II), DIOCTAHEDRAL SMECTITE, DEGREE OF EXTRACTION, SORPTION ISOTHERM, LIMITING SORPTION, EFFECTIVE SORPTION ENERGY, LANGMUIR MODEL, DUBININ-RADUSHKEVICH EQUATION
Abstract:
The aim of the work was to establish the key physicochemical parameters characterizing the sorption behavior of natural dioctahedral smectite with respect to cobalt(II) ions in aqueous solutions of cobalt sulfate, as well as to identify the dominant sorption mechanism. The effect of solution acidity on the sorption properties was estimated. It was shown that dioctahedral smectite is characterized by a wide sorption plateau in the pH range > 4. The analysis showed that the experimentally obtained sorption isotherms are satisfactorily approximated by both the classical Langmuir model, which assumes monomolecular adsorption on homogeneous active sites, and the Dubinin-Radushkevich model, which describes the process from the standpoint of the volume pore filling theory (VPF). The specific surface area of the sorbent (based on the results of Co(II) sorption) and the sorption-desorption equilibrium constant (Langmuir isotherm constant) were calculated. The agreement between the results obtained using two independent models confirms the adequacy and consistency of the experimental data. The calculated effective sorption energies for the studied system indicate that the sorption of Co(II) ions on the surface of dioctahedral smectite occurs predominantly via the physical sorption mechanism. This mechanism is characterized by the predominance of reversible and relatively weak interactions between the sorbent and sorbate, such as electrostatic and van der Waals forces. The established physicochemical mechanism is naturally explained by the specific structure of the natural aluminosilicate used, characterized by a low content of functional groups with high chelating capacity for transition metal ions (e.g., carboxyl or phenolic), as well as a limited number of ionogenic groups capable of ion exchange.
The aim of the work was to establish the key physicochemical parameters characterizing the sorption behavior of natural dioctahedral smectite with respect to cobalt(II) ions in aqueous solutions of cobalt sulfate, as well as to identify the dominant sorption mechanism. The effect of solution acidity on the sorption properties was estimated. It was shown that dioctahedral smectite is characterized by a wide sorption plateau in the pH range > 4. The analysis showed that the experimentally obtained sorption isotherms are satisfactorily approximated by both the classical Langmuir model, which assumes monomolecular adsorption on homogeneous active sites, and the Dubinin-Radushkevich model, which describes the process from the standpoint of the volume pore filling theory (VPF). The specific surface area of the sorbent (based on the results of Co(II) sorption) and the sorption-desorption equilibrium constant (Langmuir isotherm constant) were calculated. The agreement between the results obtained using two independent models confirms the adequacy and consistency of the experimental data. The calculated effective sorption energies for the studied system indicate that the sorption of Co(II) ions on the surface of dioctahedral smectite occurs predominantly via the physical sorption mechanism. This mechanism is characterized by the predominance of reversible and relatively weak interactions between the sorbent and sorbate, such as electrostatic and van der Waals forces. The established physicochemical mechanism is naturally explained by the specific structure of the natural aluminosilicate used, characterized by a low content of functional groups with high chelating capacity for transition metal ions (e.g., carboxyl or phenolic), as well as a limited number of ionogenic groups capable of ion exchange.
Keywords:
SORPTION, COBALT(II), DIOCTAHEDRAL SMECTITE, DEGREE OF EXTRACTION, SORPTION ISOTHERM, LIMITING SORPTION, EFFECTIVE SORPTION ENERGY, LANGMUIR MODEL, DUBININ-RADUSHKEVICH EQUATION
SORPTION, COBALT(II), DIOCTAHEDRAL SMECTITE, DEGREE OF EXTRACTION, SORPTION ISOTHERM, LIMITING SORPTION, EFFECTIVE SORPTION ENERGY, LANGMUIR MODEL, DUBININ-RADUSHKEVICH EQUATION
