Removal of Pb(II) and Cd(II) ions from aqueous solutions with selected organic waste

Abstract

The authors investigated sorption of Pb(II) and Cd(II) ions from aqueous solutions on selected natural wastes: sunflower hulls, walnut shells and plum stones. The chemical and physical structure of the surface of these sorbents was determined using infrared spectrometry and scanning electron microscopy. The most favourable physicochemical parameters of the sorption processes were also defined. The sorption of Pb(II) and Cd(II) ions was described according to the Langmuir and Freundlich models. It has been shown that the adsorbents studied can be effectively used in removing heavy metals from aqueous solutions. The sunflower hulls have the highest sorption capacity for Pb(II) and Cd(II) ions. It is equal to 36.93 mg/g for the Pb(II) ions and 19.93 mg/g Cd(II) ions. The calculated values of thermodynamic functions indicate a spontaneous (ΔGo< 0) and exothermic (ΔHo< 0) nature of the sorption processes. A participation of ion exchange in these processes is significant. Desorption tests confirm that the adsorbed heavy metals can be recovered and the sorbent materials after regeneration can be reused.