Sorption of copper cations from aqueous solutions by brown coals and humic acids

The sorption of copper cations by the samples of brown coal, humic acids (HAs), and residual coal after HA extraction was studied with the use of Fourier transform IR spectroscopy, EPR spectroscopy, and solid-state C-13 NMR spectroscopy. The sorption of copper cations humic acids depends on a noticeable contribution of ion exchange process. The sorption of copper cations by the initial and residual coals mainly occurred due to the formation of complexes with both individual functional groups and negatively charged surface regions. Aromatic structures and oxygen-containing functional groups make the main contribution to the complexation.