Control for selective sorption of heavy metals cations with anion exchanger AB-17-8 by modifying the surface with citrate groups

The citric acid modification produces an intermediate layer on the AB-17-8:C₆H₈O₇ surface; the layer, on one hand, is firmly secured to the surface owing to the electrostatic coupling between the citrate anion and the positively charged trimethylammonium centers of the anion exchanger surface; on the other hand, it has carbonyl groups with a local negative electron density. The sorption of heavy metals cations occurs through coordination interactions via electrostatic mechanism with local centers of negative electron density, in particular, with the carbonylic oxygen atom.