Removal of lead from aqueous solutions by natural clinoptilolite: equilibrium and kinetic studies

In this study, the removal of lead ions from aqueous solution using natural clinoptilolite under different experimental conditions was investigated. The effects of the initial metal concentration, agitation speed, temperature and pH on the removal efficiency of lead were studied. Langmuir and Freundlich isotherm constants and correlation coefficients for the present system at different conditions were calculated and compared. The equilibrium process was described well by the Langmuir isotherm model with the maximum sorption capacity of 166 mg/g of lead on clinoptilolite. The sorption kinetics were tested for the first order reaction, intra-particle diffusion, pseudo-first order, and pseudo-second order reaction at different experimental conditions. The rate constants of sorption for all these kinetic models were calculated. Good correlation coefficients were obtained for the pseudo-second order kinetic model showing that lead uptake process followed the pseudo-second order rate expression. (C) 2003 Elsevier B.V. All rights reserved.