The effect of the initial methylene blue concentrations in the solution
on the removal efficiency is presented in Fig. 3. The percent dye
removal increased with decreasing initial methylene blue concentrations.
Equilibrium is established at shorter contact times for the
higher dye concentrations and at longer times for the lower dye
concentrations.
The initial concentrations of the methylene blue solutions were
changed in order to determine the proper methylene blue adsorption
rate, while maintaining the contact time at 24 h and at a pH of
8. Figure 3 shows that the amount adsorbed, qe (mg g– 1), and percentage
removal rate increases with an increase in the dye concentration.
However, the percentage dye removal rate (99%) was constant
after 70 mg L – 1 of methylene blue concentration. Therefore,
the experiments which followed were performed at a methylene
blue concentration of 70 mg L – 1.