Lead separation by sorption onto powdered marble waste

Batch adsorption experiments were carried out, aiming to remove lead ions from aqueous solutions and water samples using powdered marble wastes (PMW) as an effective inorganic sorbent, which is cheap, widespread, and may represent an environmental problem. The main parameters (i.e., solution pH, sorbent and lead concentration, shaking time, and temperature) influencing the sorption process, were investigated. The results obtained showed that the sorption of Pb²⁺ ions onto PMW was fitted well with the linear Freundlich and Langmuir models over the concentration range studied. From the Dubinin–Radushkevick (D–R) isotherm model it was found that the adsorption was chemical in nature. Thermodynamic parameters viz. the change in Gibbs free energy change (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also calculated. These parameters indicated that the adsorption process of Pb²⁺ ions on PMW was spontaneous and endothermic in nature. Under the optimum experimental conditions employed, the removal of about 100% of Pb²⁺ ions was attained. The procedure was successfully applied to remove lead ions from aqueous and different natural water samples. Moreover, the adsorption mechanism is suggested.