fore for the further experiment, 30–35 min of contact time between
metal ion and adsorbent has been selected.
3.5. Effect of initial concentration on metal ion uptake
The initial concentration of Pb(II), Cd(II) and Co(II) provides the
necessary driving force to overcome all mass-transfer resistance
of metals between the aqueous and solid phases. Hence, a higher
initial metal concentration will have a benefit effect on the mangosteen
shells sorption capacity. Such an effect is clearly shown in
Fig. 6. From the figure it seen that the equilibrium sorption capacity
seems to increase essentially linearly with an increases in the
initial metals concentration up to 50 mg/l for Cd(II) ion, 125 mg/l
for Co(II) ion. On the other hand Pb(II) ion reach 250 mg/l by using
extracted yields mangosteen shell. The distribution of the solute,
i.e. Pb(II), Cd(II) and Co(II) metal ions between the liquid phase and
solid phase can be described by several mathematical relationships
such as the standard Langmuir–Freundlich isotherm model [24,25].
From the experimental data for binding metal ions-mangosteen