where q is the adsorbed amount (mg/g), qmax is the maximum
amount adsorbed (mg/g), KL is the equilibrium constant (L/mg),
and C is the concentration of lignosulfonate in solution (mg/L). On
the other hand, the Freundlich equation is an empirical nonlinear
equation for a non-ideal and heterogeneous adsorption process
and expressed linearly as: