Effect of pH, ionic strength, foreign ions and temperature on the adsorption of Cu(II) from aqueous solution to GMZ bentonite

The adsorption of Cu(II) from aqueous solution to GMZ bentonite was studied using batch technique under ambient conditions. Removal percentage (%) and distribution coefficient (Kd) were determined as a function of contact time, pH, ionic strength and temperature. The adsorption of Cu(II) on GMZ bentonite increased with increasing pH gradually at pH < 6.5, and maintained high level at pH > 6.5. At pH < 6.5, the removal percentage of Cu(II) was the highest at ionic strength of 0.001 M NaNO3 and was the lowest at ionic strength of 0.1 M NaNO3. The presence of complementary cations depressed the adsorption of Cu(II) on bentonite in the order of Li+ > Na+ > K+ at pH < 6.5. The adsorption isotherms were simulated by the Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) models very well. The thermodynamic parameters (i.e., ΔH0, ΔS0 and ΔG0) for the adsorption of Cu(II) were determined from the temperature dependent isotherms at 293.15, 313.15 and 333.15 K, respectively, and the results indicated that the adsorption reaction was favored at higher temperature. The results suggest that GMZ bentonite is a suitable material as an adsorbent for preconcentration and immobilization of Cu(II) from aqueous solution.