In the present study the adsorption of reactive dyes, RB21 and
RR195 on ZEC has been investigated in batch model. The equilibrium
time of adsorption was found to be 90 min for ZEC. In
the adsorption in single dye solutions, the adsorption isotherms
of RB21 and RR195 onto ZEC were well described by the Langmuir
adsorption equation. The single-component isotherms for
RB21 and RR195 have monolayer saturation capacities of 9.652
and 3.186 mg/g, respectively. It is obvious that RB21 have a higher
absorbed on ZEC than RR195. For single and binary solution of
RR195, the basic assumption of Langmuir model could be accepted.
The extended Langmuir model could described the adsorption
behaviour of RB21 in binary systems. The adsorption kinetics for
the two dyes from single dye systems, and the total amounts of
dyes adsorbed from mixed dye systems, followed the pseudosecond-
order kinetic equation. The adsorption rate constants were
observed to decrease with increasing dosage of the reactive
dyes.