Adsorption of Ni(II), Cu(II), and Zn(II) ions by natural alumosilicate modified with N,N'-bis(3-triethoxysilylpropyl)thiocarbamide

Immobilization of N,N'-bis(3-triethoxysilylpropyl)thiocarbamide on the surface of natural alumosilicates from Eastern Transbaikal has been carried out. Adsorption isotherms of Ni(II), Cu(II), and Zn(II) ions on modified adsorbents have been plotted. The experimental data have been treated using the Langmuir, Freundlich, BET, and Dubinin–Radushkevich models. The constants of these equations have been determined. It has been shown that adsorption on alumosilicates modified with N,N'-bis(3-triethoxysilylpropyl)thiocarbamide is described in the best way by the Freundlich and Langmuir adsorption models. The Dubinin–Radushkevich model has been employed for the calculation of free energy of adsorption. For all the specimens under study, the free energy of adsorption indicates the presence of an ion-exchange mechanism, while the adsorption of heavy-metal ions has a chemical nature.