The effect of contact time on sorption of malachite green onto
AL at different temperatures was shown in Fig. 2. As can be seen
from Fig. 2, the amount of sorbed MG is rapid at early stages and
becomes slow with increasing of time and gradually approaches
equilibrium state. When Fig. 2 was taken into account, 5 h may be
considered as sufficient time to reach equilibrium state.
To gain a better understanding adsorption kinetics and ratelimiting
step, several kinetic models were used. These kinetic
models are Lagergren-first-order model, pseudo-second-order
kinetic model, Elovich’s model and Intraparticle diffusion model.
Lagergren equation was used to investigate the suitability of
pseudo-first-order kinetic model and obtain rate constants [22].