Dimethylglyoxime based ion-imprinted polymer for the determination of Ni(II) ions from aqueous samples

Abstract

A Ni(II)-dimethylglyoxime ion-imprinted polymer {Ni(II)-DMG IIP} was synthesised by the bulk polymerisation method. The morphology of the Ni(II)-DMG IIP and non-imprinted polymer were observed by scanning electron microscopy and the chemical structures were evaluated by infrared spectroscopy. Selectivity of the Ni(II)-DMG IIP was studied by analysing, using an inductively coupled plasma-optical emission spectrometer, for Ni(II) ions that were spiked with varying concentrations of Co(II), Cu(II), Zn(II), Pd(II), Fe(II), Ca(II), Mg(II), Na(I) and K(I) in aqueous samples. The studies revealed Ni(II) recoveries ranging from 93 to 100% in aqueous solutions with minimal interference from competing ions. Enrichment factors ranged from 2 to 18 with a binding capacity of 120 µg•g −1. Co(II) was the only ion found to slightly interfere with the determination of Ni(II). Selectivity studies confirmed that the Ni(II)-DMG IIP had very good selectivity, characterised by %RSD of less than 5%. The limits of detection and quantification were 3x10-4 µg•mℓ −1 and 9x10-4 µg•mℓ −1 , respectively. The accuracy of the method was validated by analysing a custom solution of certified reference material (SEP-3) and the concentration of Ni(II) obtained was in close agreement with the certified one. The Ni(II)-DMG IIP was successfully employed to trap Ni(II) ions from a matrix of sea, river and sewage water. It is believed that the Ni(II)-DMG IIP has potential to be used as sorbent material for pre-concentration of Ni(II) ions from aqueous solutions by solid-phase extraction.

Optimal synthesis of a Ni(II)-dimethylglyoxime ion-imprinted polymer for the enrichment of Ni(II) ions in water, soil and mine tailing samples

“…These extraction efficiencies were achieved with a smaller total volume of the mixture (from 12.93 to 10.55 mℓ), though the volume of monomer used was greater than that used in the previous study (Rammika et al, 2011) i.e. before optimisation.…”

“…A polymer was expected to be formed in Run 3, but with lower absorption capacity than in Run 7, as the only difference between Runs 3 and 7 was the volume of porogen. The optimum volume of porogen was 8.0 mℓ compared to the 10.0 mℓ that was used without optimisation (Rammika et al, 2011). The extraction efficiency of Ni(II) increased from 99.35 to 99.91% after varying the amounts of template, monomer and ligand (Table 3).…”

“…The morphology of the imprinted, non-imprinted and DMG polymers is discussed in Rammika et al (2011); the polymers in this earlier study were also characterised using infrared spectra.…”

“…Ni(II)-DMG IIP was prepared as outlined by Rammika et al (2011). For the uniform design experiments, a series of Ni(II)-DMG IIPs were prepared through the process described but with varying concentrations of the reactants (Tables 1, 2 and 3 and Fig.…”

“…Sample collection and preparation Sea, river, untreated sewage and treated sewage water samples were collected and treated as outlined by Rammika et al (2011). Soil and mine tailing samples were collected in polyethylene bags from buildings around the Chemistry and Pharmaceutical Sciences Building (Rhodes University, Grahamstown) and Selibe Phikwe copper-nickel mine (Selibe Phikwe, Botswana), respectively.…”