Preparation of Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate by coprecipitation and its uptake of rare earth ions from aqueous solution

A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta•Cu-Al LDH) was prepared by the dropwise addition of a Cu-Al nitrate solution to an edta solution at constant pH values of 8.0, 9.0, and 10.0. The edta•Cu-Al LDH had Hedta^3- in the interlayer. Furthermore, the preparation at pH 8.0 resulted in the intercalation of Cu(edta)^2-. The edta•Cu-Al LDH was found to take up rare earth ions from aqueous solution. The uptake of Sc³⁺ and Y ³⁺ by edta•Cu-Al LDH was attributed to both the chelating functions of the edta ion in the interlayer and the chemical properties of Cu-Al LDH itself. The uptake of La³⁺ by edta•Cu-Al LDH was primarily caused by the chelating function of edta ions in the interlayer. The edta ions in the edta•Cu-Al LDH interlayer formed chelate complexes in the order Sc³⁺ > Y³⁺ > La³⁺ due to their relative stabilities, Sc(edta)^- > Y(edta)^- > La(edta) ^-. Thus, edta ions retain their chelating function even when intercalated in a Cu-Al LDH interlayer.