Synthesis of two new pyrazole based ligands for the liquid–solid extraction of heavy metals Pb, Cd and Cu in the aqueous medium

Abstract

Most of heavy metals (Pb(II), Cu(II), Cd(II)) which are toxic even at a low concentration. These toxic metals are released into the environment by various natural or industrial sources. Faced with this situation, many methods have been developed to extract these toxic metals from the environment and namely when they are present in water. This work consists of the development of a synthesis based on two new heterocyclic ligands L1 (N1, N1, N5, N5-tetrakis ((3,5-dimethyl-1H-pyrazol-1-yl) methyl) naphthalene-1,5-diamine) and L2 (2-(bis ((1H-pyrazol-1-yl) methyl) amino) pyrimidine-4,6-diol) based on pyrasole. The outcome is to extract certain heavy metals when present in an aqueous medium. The synthesis of these two ligands L1 and L2 is achieved via condensation reactions between hydroxymethyl pyrazoles units and an aromatic primary amines and diamines. The characterization of these two synthetic ligands is carried out by IR and NMR analysis techniques. Subsequently a study of their capacities and their selectivity in the liquid–solid extraction of the metal cations Pb(II), Cd(II) and Cu(II) was made from an aqueous solution in batch mode. The effect of the operating conditions (C0, ph, T) on this extraction is also studied. The modeling of the adsorption of heavy metals studied by our two ligands is established by the isotherms of the Langmuir and Freundlich models. The results obtained show a high adsorption capacity and an excellent selectivity of the two ligands towards Pb(II) (80% for L1 and 60% for L2).