Biosorption of copper by dried plant leaves studied by electron paramagnetic resonance and infrared spectroscopy

We report on the biosorption of copper ions by dried leaves from the Brazilian flora. By Electron Paramagnetic Resonance (EPR), it is shown that the copper ions are incorporated in the leaves in a strongly axial site. Washing with a basic solution does not remove the copper from the leaves, however, it modifies the axial site symmetry. Infrared absorption seems to be compatible with a site that is located near to a simple or a double carbon-oxygen bond. Dried leaves are a good and commercially interesting alternative for sorption of metal ions compared to other biomasses.