The comparison of the removal of copper(II) and zinc(II) ions from aqueous solution using 2,6-diaminopyridine in a polymer inclusion membrane and in a classic solvent extraction

In this work, the recovery of copper(II) and zinc(II) ions from aqueous solutions using solvent extraction and polymer inclusion membranes (PIMs) was compared. 2,6-Diaminopyridine was used as an extractant in solvent extraction and as a carrier in PIMs. The characteristic parameters of these two processes were determined. The results of all the experiments were processed and, additionally, standard deviations were calculated. The percentage of extraction was dependent on the ligand concentration in the organic phase. For solvent extraction, the highest extraction percentage was 83.53% for copper(II) ions and 93.12% for zinc(II) ions. In the case of application of the PIM containing 20 wt.% of 2,6-diaminopyridine as a carrier, the highest recovery factor determined after 24 h was 72.81% for copper(II) ions and 93.65% for zinc(II) ions, respectively. The stability constants of its complexes of 2,6-diaminopyridine with copper(II) and zinc(II) ions were determined spectrophotometrically. Electrospray ionization high-resolution mass spectrometry was applied for the confirmation of the ability of 2,6-diaminopyridine to form complexes with Cu(II) and Zn(II) ions in solutions and for determination of the elemental composition of these complexes.