Selective solid-phase extraction of trace cadmium(II) with an ionic imprinted polymer prepared from a dual-ligand monomer

A novel dual-ligand reagent (2Z)-N,N′-bis(2-aminoethylic)but-2-enediamide, was synthesized and applied to prepare metal ion-imprinted polymers (IIPs) materials by ionic imprinted technique for selective solid-phase extraction (SPE) of trace Cd(II) from aqueous solution. In the first step, Cd(II) formed coordination linkage with the two ethylenediamine groups of the synthetic monomer. Then the complex was copolymerized with pentaerythritol triacrylate (crosslinker) in the presence of 2,2′-azobisisobutyronitrile as initiator. Subsequently, the imprinted Cd(II) was completely removed by leaching the dried and powdered materials particles with 0.5 M HCl. The obtained IIPs particles exhibited excellent selectivity for target ion. The distribution ratio (D) values of Cd(II)-IIPs for Cd(II) were greatly larger than that for Cu(II), Zn(II) and Hg(II). The relative selective factor (α_r) values of Cd(II)/Cu(II), Cd(II)/Zn(II) and Cd(II)/Hg(II) were 25.5, 35.3 and 62.1. The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Cd(II) was 32.56 and 6.30 mg g⁻¹, respectively. Moreover, the times of adsorption equilibration and complete desorption were remarkably short. The prepared Cd(II)-IIPs were shown to be promising for solid-phase extraction coupled with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the determination of trace Cd(II) in real samples. The precision (R.S.D.) and detection limit (3σ) of the method were 2.4% and 0.14 μg L⁻¹, respectively. The column packed with Cd(II)-IIPs was good enough for Cd(II) separation in matrixes containing components with similar chemical behaviour such as Cu(II), Zn(II) and Hg(II).