A stoichiometric imprinted chelating resin for selective recognition of copper(II) ions in aqueous media

This work reports the preparation of a new copper(II) ion-imprinted polymer (IIP) material, using 5,6;14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane-5,14-diene (DBDA15C4) and 2-vinylpyridine (VP) as a non-vinylated chelating agent and a functional vinyl monomer, respectively. The Cu2+ ion can form stable complexes with DBDA15C4 and VP. The stoichiometries of Cu2+–DBDA15C4 and ternary Cu2+–DBDA15C4-VP complexes were elucidated using conductometric and spectrophotometric methods, and found to be Cu2+(DBDA15C4), Cu2+(DBDA15C4)2 and Cu2+(DBDA15C4)(VP)2. The results obtained from solution studies were also supported by ab initio theoretical calculations. The resulting ternary complex Cu2+(DBDA15C4)(VP)2 was copolymerized with ethyleneglycoldimethacrylate, as a cross-linking monomer, via bulk polymerization method. The imprinted copper ion was removed from the polymeric matrix by 0.1 M HNO3. The Cu2+-imprinted polymer particles were characterized by IR spectroscopy and elemental analysis. Optimum pH range for rebinding of Cu2+ on the IIP and equilibrium binding time were 7.0–7.5 and 45 min, respectively. Sorbent capacity and enrichment factor for Cu2+ were obtained as 75.3 ± 1.9 μmol g−1 and 100, respectively. In selectivity study, it was found that imprinting results in increased affinity of the material toward Cu2+ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for five times without a significant decrease in polymer binding affinities.