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

Abstract

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 Hedta3− 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 Y3+ 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.