Langmuir isotherm: 1/Qe = 1/(q 9 bCe) ? 1/q, where
Qe is the concentration of adsorbed metal per unit weight of
adsorbent, Ce is the concentration of Pb(II) ions in the
aqueous phase, q is the maximumadsorption capacity per unit
weight of adsorbent, b is the adsorption equilibrium constant.