3.4. Effect of shaking time
The capacity of adsorption for 10 and 50 mg/l of Cd2 + solution increased rapidly until around 30 min and then became constant until 24 h of shaking. It was clear from the result of this study in Fig. 5 that shaking time required for maximum adsorption of Cd2 + ion by this adsorbent was dependent on the initial cadmium concentration. The adsorption capacity of cadmium ion for high initial cadmium ion concentration was higher than for low initial cadmium ion concentration of the solution at the same time. This result is important because the time required to reach equilibrium is one of the considerations for the application of economical wastewater treatment plant (Khalfa and Bagane, 2011 and Rao et al., 2006).