Uptake of Cu2+, Cd2+ and Pb2+ on Zn–Al layered double hydroxide intercalated with edta

Hydrotalcite-like compound [Zn2Al(OH)6]2edta·nH2O(ZnAl-edta) was obtained from the precursor [Zn2Al(OH)6]NO3·nH2O (ZnAl-NO3), by the anion exchange method, with the aim of uptake Cu2+, Cd2+ and Pb2+ from the aqueous solutions by chelating process between edta and metal cations. The amount of Cu2+, Cd2+ and Pb2+ adsorbed was monitorized by atomic absorption technique at different contact time, pH and metal concentrations. The results indicate the very fast adsorption of the metal cations by ZnAl-edta reaching the equilibrium of the uptake reaction in two hours for Cu and Pb and 24 h for Cd. The shape of the adsorption isotherms suggests specific interaction and high host–guest affinity. At pH 5.5 and initial concentration Ci = 10 mM, the amount adsorbed was Cs = 1117, 375 and 871 μmol/g for Cu2+, Cd2+ and Pb2+, respectively.