Competitive adsorption of heavy metal ions on peat

The uptake capacities, and the adsorption kinetics, of copper, Cu(II), nickel, Ni(II), and cadmium, Cd(II), on peat have been studied under static conditions. The results show that the adsorption rates are rapid: equilibrium is reached in twenty minutes. The adsorption of copper, nickel and cadmium is pH dependent over the pH range from 2 to 6. The adsorption kinetics can be excellently described by the Elovich kinetic equation. The adsorption isotherm fits a Langmuir model very well. The adsorption capacities follow the order Cu2+ > Ni2+ > Cd2+ in single-component systems and the competitive adsorption capacities fall in the decreasing order Cu2+ > Ni2+ > Cd2+ in multi-component systems. The adsorption capacities of these three heavy metal ions on peat are consistent with their observed competitive adsorption capacities.