Abstract
In this study, a low-cost biosorbent was prepared using Populas nigra leaves as biomass. The leaves were modified chemically by nitric acid/calcium chloride and characterized through different instrumental techniques (Fourier transformed infrared spectroscopy, scanning electron microscopy and surface area analyzer). The prepared biosorbent was used as adsorbent for the removal of Cd(II), Cr(VI) and Pb(II) ions from aqueous media. Biosorption was studied as a function of pH (2-7), biosorbent dose (1-30 mg/L), contact time (5-120 min), and initial metal ion concentration (20-700 mg/L) at a shaking speed of 170 rpm. The experimental isothermal data were analyzed by the Langmuir and Freundlich isotherm models. The maximum monolayer biosorption capacity of Cd(II), Cr(VI), and Pb(II) was found to be 107.526, 208.3, and 172.413 mg g(-1), respectively, with best fitting obtained for Langmuir model. Kinetic data fitted well to the pseudo-second order equation rather than the pseudo-first order equation. The thermodynamic parameters such as standard enthalpy change (Delta H degrees), entropy change (Delta S degrees), and Gibbs free energy (Delta G degrees) determined suggest that biosorption of these metals by this biosorbent is an exothermic, spontaneous and favorable process.