In the above equations, Q is the maximum amount of the
dye absorbed per unit weight of fibre to form a complete
monolayer coverage on the surface bound at high equilibrium
dye concentration Ce, qe is the amount of dye adsorbed per
unit weight of fibre at equilibrium, and b is the Langmuir con-
stant related to the affinity of the binding sites. The value of Q
represents a practical limiting adsorption capacity when the
surface is fully covered with dye molecules and assists in
the comparison of adsorption performance [18]. The values
of Q and b are calculated from the intercepts and slopes of
the straight lines of plot of 1/qe versus 1/Ce.
The Langmuir constant b is related to the enthalpy of ad-
sorption, (b f (exp(DHo
/RT ))) [21]. Therefore, the thermo-
dynamic parameters including the free energy change (DGo
),
enthalpy change (DHo
) and entropy change (DSo
) were also
evaluated using the following equations [22,23]: