Adsorption behaviour of Cu2+ and Cd2+ onto natural bentonite

The adsorption behaviour of Cu2+ and Cd2+ onto bentonite was studied as a function of temperature under optimized conditions of amount of adsorbent, particle size, pH, concentration of metals, and shaking time. The adsorption patterns of metal ions onto followed the Langmuir, Freundlich and Dubinin–Radushkevich isotherms. This included adsorption isotherms of single-metal solutions at 298–333 K by batch experiments. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnKo vs. 1 / T plots. The adsorptions were endothermic reactions. The results suggested that natural bentonite was suitable as sorbent material for the recovery and adsorption of metal ions from aqueous solutions.