Kinetic and isothermal studies of lead ion adsorption onto bentonite

The use of bentonite for the removal of Pb(II) from aqueous solutions for different contact times, pH of suspension, and initial concentration of Pb and particle sizes of absorbent was investigated. Batch adsorption kinetic experiments revealed that the adsorption of Pb(II) onto bentonite involved fast and slow processes. The adsorption mechanisms in the lead/bentonite system followed pseudo-second-order kinetics with a significant contribution of film diffusion. The adsorption isotherms were described by means of the Langmuir and Freundlich isotherms and the Langmuir model represented the adsorption process better than the Freundlich model. The maximum adsorption capacity of Pb(II) onto natural bentonite was 78.82 mg g^− 1.