Effect of initial MB concentration and contact time
The driving force for the dye mass transfer between the aque-ous and solid phase is correlated to the initial dye concentration.
The effect of the initial MB concentration on the adsorption capacity
and removal efficiency, evaluated at pH 6 and 20
◦
C, using an adsor-bent dosage of 1 g L
−1
and a contact time of 24 h is shown in Fig. 2a
and Fig. 3a, respectively. As can be seen, the adsorption capac-ity increased with increasing the initial MB concentration until a
plateau was reached (Fig. 2a): the maximum adsorption capacity
was of about 170 mg g
−1
and it was reached at the initial MB con-centration of 250 mg L
−1
. This behavior can mainly attributed to
the concentration gradient increase which results in an enhanced
driving force for the mass transfer