Abstract

The aim of this study is to investigate Lewatit TP 214, which is a chelating ion-exchange polymer containing chemically bonded thiourea
group, for the sorption of Pb(II) and Cd(II) ions from aqueous solutions. The effects of parameters such as the concentration, pH, contact
time, ionic strength and temperature have been investigated. The results showed more affinity of resin towards cadmium than for lead
cations. Lewatit TP 214 exhibited a good sorption potential at initial pH values for Pb(II) and Cd(II) at room temperature. The extraction
kinetics, for both Pb(II) and Cd(II), is best described by the pseudo second order model. This study showed that the diffusion of moving
boundary particles fits well the experimental data (r > 0.99) for the sorption of both Pb(II) and Cd(II) ions. The Langmuir isotherm fits
better with the obtained equilibrium data as compared to that with the Freundlich isotherm. The thermodynamic data for the sorption of
Pb(II) and Cd(II), on the resin, indicate that the process is endothermic for Pb(II) while it is exothermic for Cd(II). The process showed
negative ∆G values, indicating that the sorption of both Pb(II) and Cd(II) ions is spontaneous

Key words: Pb(II), Cd(II), polystyrene thiourea, kinetics, thermodynamics, diffusion