Thermodynamic and isotherm studies of the biosorption of Cu(II), Pb(II), and Zn(II) by leaves of saltbush (Atriplex canescens)

The Freundlich and Langmuir isotherms were used to describe the biosorption of Cu(II), Pb(II), and Zn(II) onto the saltbush leaves biomass at 297 K and pH 5.0. The correlation coefficients (R) obtained from the Freundlich model were 0.9798, 0.9575, and 0.9963 for Cu, Pb, and Zn, respectively, while for the Langmuir model the R-2 values for the same metals were 0.0001, 0.1380, and 0.0088, respectively. This suggests that saltbush leaves biomass sorbed the three metals following the Freundlich model (R-2 > 0.9575). The K-F values obtained from the Freundlich model (175.5 center dot 10(-2), 10.5 center dot 10(-2). and 6.32 center dot 10(-2) mol center dot g(-1) for Pb, Zn, and Cu, respectively), suggest that the metal binding affinity was in the order Pb > Zn > Cu. The experimental values of the maximal adsorption capacities of saltbush leaves biomass were 0.13 center dot 10(-2), 0.05 center dot 10(-2). and 0.107 center dot 10(-2) mol center dot g(-1) for Pb. Zn, and Cu, respectively. The negative Delta G degrees values for Pb and the positive values for Cu and Zn indicate that the Pb biosorption by saltbush biomass was a spontaneous process. (c) 2006 Elsevier Ltd. All rights reserved.