where qmax represents the mass of dye adsorbed over mass of
adsorbent for a complete monolayer, KL is the Langmuir constant, Ce
is the equilibrium concentration. Freundlich isotherm is used to
describe a heterogenous adsorption. The model assumes neither
homogenous site energies nor limited level of adsorption, and
therefore as the dye concentration increases so does the concentration
of dye on the adsorbent surface. The equation is given as,