Adsorption of Pb(II) and Cd(II) metal ions from aqueous solutions by mustard husk

The adsorption of Pb(II) and Cd(II) metal ions on mustard husk has been found to be concentration, pH, contact time, adsorbent dose and temperature dependent. The adsorption parameters were determined using Langmuir and Freundlich isotherm models. The adsorption isotherm studies clearly indicated that the adsorptive behavior of Pb(II) and Cd(II) metal ions on mustard husk satisfies not only the Langmuir assumptions but also the Freundlich assumptions, i.e. multilayer formation on the surface of the adsorbent with an exponential distribution of site energy. Ion exchange and surface complexation are the major adsorption mechanisms involved. The applicability of Lagergren kinetic model has also been investigated. Themodynamic constant (k(ad)), free energy change (Delta G), enthalpy change (Delta H) and entropy change (Delta S) were calculated for predicting the nature of adsorption. The results indicate the potential application of this method for effluent treatment in industries and also provide strong evidence to support the adsorption mechanism proposed. (c) 2007 Published by Elsevier B.V.