Removal of nickel(II) and cadmium(II) ions from aqueous solutions using an oxide adsorbent of MgO·SiO₂ type

Abstract

The principal aim of the present work was to obtain an inorganic oxide system, MgO·SiO₂, with unique physicochemical and electrokinetic properties which would enable its use as an effective adsorbent of nickel(II) and cadmium(II) ions. An important component of the work was involved in determining, how the pH and the quantity of adsorbent affect the efficiency of the process for the removal of nickel(II) and cadmium(II) ions from model aqueous solutions. The effectiveness of the adsorption process was evaluated using various analytical techniques, including atomic absorption spectroscopy and energy dispersive X-ray spectroscopy. Nickel or cadmium elution was also tested, in order to determine the durability of the bonds between adsorbent and adsorbate. At the next stage, Langmuir’s and Freundlich’s models were used to describe the equilibrium adsorption isotherms, applying the method of nonlinear regression. The experimental data were found to fit well with Langmuir’s isotherm model. The maximum adsorption capacity of an MgO·SiO₂ monolayer was 56.59 mg (Ni²⁺)/g and 35.86 mg (Cd²⁺)/g, which indicates that the synthesized material acts as a highly effective adsorbent of nickel(II) as well as cadmium(II) ions.

Keywords:

• Synthetic oxide adsorbents
• Adsorption
• Nickel
• Cadmium
• Adsorption isotherms

Acknowledgments

The study was financed within the Polish National Centre of Science funds according to decision no. DEC-2011/03/D/ST5/05802.