FT-IR and ESR studies on Cu II -loaded microspheres

Imprinting polymerisation for recognition and separation of metal ions 

the amount of Cu(II) carried by the microsphere samples was estimated for Samples 1-3. This was determined by measuring the concentration of free Cu(II) in the aqueous solution at adsorption equilibrium Sample 1, 1.5 x 10 mol g Sample 2, 5.7 x 10 mol g Sample 3, 1.4 x 10 mol g.  

The preparation of the microspheres followed the recipe by Okubo et al. [19]. Therefore, the amount of carboxyl groups in the microspheres was expected to be similar to that of Okubo s microspheres. It was assumed that the total amount of surface carboxyl groups in the microspheres would be 2.2 x 10 mol g, according to Okubo s report, and that each Cu(ll) ion would be coordinated by two carboxylate groups. Then, the mole fraction of carboxyl groups bound to Cu(ll) with respect to the total surface carboxyl groups in the Cu(ll)-loaded microspheres was to be as follows Sample 1, 1/70 Sample 2, 1/20 Sample 3, 1/1. It is noted that all the carboxyl groups on the surface of Sample 3 seem to be complexed with Cu(ll). 

ESR spectra were examined for Samples 1-3 [17]. As these spectra suffer from considerable noise due to the small sample volume of Cu(II), g// and A// values could not be determined clearly. However, all spectra indicated a pattern characteristic for a square-planar Cu(II) complex carrying four coordinating oxygen atoms [20,21]. 

Cu(II) spectral intensities for Samples 1-3 were in the order of Sample 3 Sample 2 Sample 1. Although ESR spectrometry in general is semi-quantitative in nature, the order of the spectral intensity was consistent with the amount of Cu(II) on the microspheres as determined by the Cu(II) adsorption study. The imprinting effect or an enhanced Cu(II) adsorption behaviour as indicated by the metal adsorption test is in a sense indirect, because it only shows the decrease in Cu(II) concentration in a test solution. Meanwhile, the presented ESR spectra directly indicated such an enhanced Cu(II) adsorption and complex chemical structure of the adsorbed Cu(II) species in the Cu(II)-imprinted microspheres. 

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