Removal of heavy metal ions by using dithiocarbamated-sporopollenin

In this study, the sorption conditions of Cu(II), Pb(II) and Cd(II) metal ions onto dithiocarbamated-spororpollenin (DTC-S) have been investigated. The different variables affecting the sorption capacity such as pH of the solution, sorption time, initial metal ion concentration and temperature have been investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the sorption processes. Sorption isotherms correlated well with the Langmuir type sorption isotherm and sorption capacities were found to be 0.2734, 0.4572 and 0.0631 mmol g-1 for Cu(II), Pb(II) and Cd(II) metal ions, respectively. Sorption processes for three target heavy metal ions were found to follow pseudo-second order type sorption kinetics. Intraparticle diffusion was found to take part in sorption processes but it could not be accepted as the primary rate determining step. On the evaluation of the results obtained for the mean free energies of sorption (E) and enthalpy of sorption (ΔH°) it was observed that the resin mainly shows the characteristics of a chelating exchanger. Thermodynamic parameters, ΔH°, ΔS° and ΔG° were also calculated from graphical interpretation of the experimental data. Standard heats of sorption (ΔH°) were found to be endothermic and ΔS° values were calculated to be positive for the sorption of Cu(II), Pb(II) and Cd(II) ions onto the adsorbent. Negative ΔG° values indicated that sorption process for these three metal ions onto DTC-Sp is spontaneous. © 2006 Elsevier B.V. All rights reserved.