Competitive Adsorption of Ag⁺, Pb²⁺, Ni²⁺, and Cd²⁺ Ions on Vermiculite

Abstract

Competitive adsorption of Ag⁺, Pb²⁺, Ni²⁺, and Cd² ions on vermiuculite in a binary, ternary, and quaternary mixture was investigated in batch experiments. The effects of the presence of Ag⁺, Ni²⁺, and Cd²⁺ ions on the adsorption of Pb²⁺ ions were investigated in terms of the equilibrium isotherm. Experimental results indicated that Pb²⁺ ions always favorably adsorbed on vermiculite over Ag⁺, Ni²⁺, and Cd²⁺ ions. The adsorption equilibrium data of Pb²⁺ ions better fitted the Langmuir model than the Freundlich model. The results showed that the pseudo-second-order kinetics model was in good agreement with the experimental results for all metal ions, and the adsorption rate among the metal ions followed Ag⁺ > Pb²⁺ > Ni²⁺ > Cd²⁺. The desorption and regenration study indicated that vermiculite can be used repeatedly and be suitable for the design of a continuous process.

Keywords:

• competitive adsorption
• metal ion
• vermiculite

ACKNOWLEDGMENTS

The authors thank the Xinjiang Yuli Xinlong Vermiculite Company, China, for supplying the vermiculite used in this study and Wenshu Yang, Analysis and Testing Center, Sichuan University, China, for help with AAS measurements.