The uptake of MB onto RPR and APR was increased
with the increase in contact time. The adsorption
equilibrium at 110 min was achieved for RPR and
90 min for APR. Compared to APR, RPR is more time
consuming and also the percentage of dye removal is
less. Initial adsorption was rapid due to the adsorption
of dye onto exterior surface, after that dye molecules
enter into pores (interior surface), a relatively slow
process [20]. Data on the adsorption kinetics of dyes
by various adsorbents have shown a wide range of
adsorption rates. For example, the effect of contact
time for the adsorption of Orange-G and Crystal Violet
dye by bagasse fly ash was studied for a period of 24 h
for initial dye concentrations of 10 mg L-1 at 30 °C
[21]. Mall et al. [21] reported that after 4 h of contact,
a steady-state approximation was assumed and a
quasi-equilibrium situation was achieved.
Spectrochemical Characterization