where C
e is the adsorbate concentration at equilibrium (mg/L),
qe is the adsorption capacity at equilibrium (mg/g), b is the
adsorption equilibrium constant (L/mg) related to the apparent
energy of adsorption, qm is the maximum adsorption capacity
of absorbent (mg/g), n indicates the bond energies between
metal ion and the adsorbent, and k F (L/g) is related to bond
strength [2].