where qe (mg/g) and Ce (mg/l) are the equilibrium concentrations
of copper in the solid and liquid phases, respectively. kf
[(mg/g)/(mg/l)1/n] is the Freundlich constant related to the sorption
capacity of the adsorbent and 1/n is the Freundlich constant
related to the energy heterogeneity of the system and the size of
the adsorbed molecule. The values of kf and n can be determined
from the linear plot of log qe versus log Ce. In Eq. (2) Q0 (mg/g) represents
the theoretical monolayer saturation capacity and b (1/g) is
an empirical parameter related to the energy of adsorption. A plot
of 1/qe versus 1/Ce gives a straight line of slope 1/Q0b and intercepts
1/Q0.