3.4. Effect of metal concentration
For a given quantity of adsorbent (0.4 g) the effect of metal concentration on the adsorption is shown in Fig. 6. The percentage of metal ions adsorption decreased with upto certain increase in metal ion concentration after which the decrease was minimal in the case of Ni both for MBAC and MBRC. In the case of Zn (II), the decrease in adsorption is very less with increase in concentration for both the activated and the raw charcoal. This can be explained as; at low metal
ion/adsorbent ratios, metal ion adsorption involves higher energy sites. As the metal ion/adsorbent ratio increases, the higher energy sites are saturated and adsorption begins on lower energy sites, resulting in decrease in the adsorption efficiency [40,41].