The effect of initial concentration on percentage removal of
Pb(II) ions (range 100–600 mg/L) is shown in (Fig. 6). It
can be seen that percentage adsorption of lead ion
increased with increase in initial concentration up to a
certain amount, and then it shows no further effect on
adsorption. Maximum adsorption takes place at 500 mg/L
of lead ion concentration. This can be explained as follows:
at low initial concentration the ratio of number of metal
ions to the number of available adsorption site was small
and consequently the adsorption was independent of initial
ion concentration, but as the concentration of metal ion
increased, the situation changes and the competition for
adsorption site becomes less. As a result, the extent of
adsorption decreases, or remains constant.