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

Competitive adsorption of Ag+, Pb2+, Ni2+, and Cd-2 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.