where qt and qe are the amounts of the lead ions adsorbed at time t and at equilibrium,
respectively. k1 and k2 are the pseudo-first and second-order rate constants for the adsorption
process.
Two adsorption isotherms models had been used to analyze the adsorption data at equilibrium.
These models were used to fit the experimental data through two equations [32]:
(i) Langmuir