Low cost natural adsorbent for removal of Pb(II) ions from waste solutions

Abstract

In this paper, the adsorption behavior of Pb 2+ ions from aqueous solutions onto castor stem as a natural adsorbent was investigated under various experimental conditions. Characterization of castor sorbent was evaluated by SEM, XRD, FTIR, TGA, BET surface area analysis, and CHNS elemental analyses. Operational parameters such as pH, contact time, initial ion concentrations, sorbent amount, particle size, competing ions, and temperature were also studied. Adsorption data fitted well with the Langmuir and Freundlich models. However, Freundlich isotherm displayed a better fitting model than Langmuir isotherm because of the higher correlation coefficient that the former exhibited, thus, indicating the applicability of multilayer coverage of the Pb (II) on the surface of adsorbent. On the basis of distribution studies, the distribution coefficient (K d ) increases with increasing the reaction temperature of the solution. Thermodynamic parameters, ∆H o , ∆G o , and ∆S o were calculated and indicated an endothermic and spontaneous process.