Equilibrium isotherm studies for the uptake of cadmium and lead ions onto sugar beet pulp

The adsorption of Cd²⁺ and Pb²⁺ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd²⁺) and lead (Pb²⁺) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd²⁺ and Pb²⁺ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70min of contact. As much as 70-75% removal of Cd²⁺ and Pb²⁺ ions for (SBP) are possible in about 70min, respectively, under the batch test conditions. Uptake of Cd²⁺ and Pb²⁺ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1mgg⁻¹ for Cd²⁺ and at pH 5.0 and gives 43.5mgg⁻¹ for Pb²⁺ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8gL⁻¹ was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO₃ the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd²⁺ and Pb²⁺ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.