Interaction of Copper and Lead Cations with Residues Derived from Lignite

The coal residues (CR) obtained after the removal of humic matter from lignite is characterized by infrared (IR), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR). The structural groups present in the residues differ from those in the initial lignite. The sorption of copper and lead cations by the coal residues is studied. The sorptional capacity of the residues is greater for copper than for lead. Two mechanisms are involved in the interaction of the residues with copper and lead cations: ion exchange of the metal cations for protons of the carboxyl groups; and complex formation. The ligands involved may be oxygen-bearing structural groups such as carboxyl and phenol hydroxyl groups.