Studying the Adsorption of Copper, Zinc, and Cadmium Ions on Native and Modified Montmorillonite-Containing Clay

Results of studying the adsorption of copper(II), zinc(II), and cadmium(II) ions on native and modified montmorillonite clay in the OH form from the Tobolsk district of the Tyumen oblast are described. The studies are conducted using model solutions with concentrations of 0.5–15 mg/mL at a temperature of 298 K. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models are used to describe the experimental adsorption isotherms of the studied ions. The constants and parameters of all the equations used are calculated. The determined regression coefficients R2 confirm that the Langmuir model is the best model to describe the experimental adsorption data for Cu+2, Zn+2, and Cd+2 ions. The experimental data with correlation coefficients for the ions are 0.9997 for Cu+2, 0.995 for Zn+2, and 0.9902 for Cd+2. The sorption energy calculated in terms of the Dubinin–Radushkevich model confirms that cadmium and zinc ions undergo physical sorption, while copper ions are sorbed in accordance with the ion-exchange mechanism. The results obtained show that montmorillonite clay modified in the OH form can be used to remove heavy metal ions from water bodies.