Uptake of Cu, Cd and Pb 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 C_i = 10 mM, the amount adsorbed was C_s = 1117, 375 and 871 μmol/g for Cu²⁺, Cd²⁺ and Pb²⁺, respectively.