The Langmuir model fitted to the experimental data better than
other isotherm models, indicating the adsorption of Yellow 18 onto
the activated carbon tended to monolayer adsorption. Furthermore,
the R2 values of the four isotherm models descend in the order
of: Langmuir > Temkin > Freundlich > Dubinin–Radushkevich.
The results revealed that the equilibrium data fitted better by the
two-parameter models rather than three-parameter models.