Adsorption of heavy metal cations by organic ligands grafted on porous materials

The purpose of this work is the development of new sorbents containing different ligands grafted on the surface of a porous support. These materials are capable of immobilizing heavy metals in order to prevent leaching into the ground water. In this study, we grafted the ligands on silica gel, and two types of zeolites: ZSM-5 and Y. Due to the highest achievable loading, silica gel was selected for further studies. Immobilized complexes with Cd, Cu, Ni, Pb and Zn were prepared and studied by physical and chemical methods in order to determine their composition and structural characteristics. The stability of the complexes with heavy metals and the metal leaching from the sorbents were studied for different pH values. Studies of the immobilized metals by NMR and ESR showed that the metals form several complexes of different structures. The resulting silica-grafted materials can be used for the treatment of contaminated soils containing heavy metals, thus allowing a safe disposal of sludge, without the risk of contaminant leaching, in order to increase the environmental security in contaminated areas.