Electrochemically oxidized carbon fibres as an adsorbent for the attachment of dissolved substances. Adsorption of nitro compounds and ion-exchange of heavy metals

Abstract

The adsorption of several aromatic nitro compounds and the ion-exchange of heavy metal ions on electro-oxidized carbon fibres have been investigated using cyclic voltammetric and polarographic techniques. Electro-oxidation is performed by potentiostatic double pulse application. This procedure results in the generation of many functional —OH and —COOH groups with adsorptive and ion-exchanging properties.Multimolecular layers of adsorbed substances may be formed through a procedure of successive adsorption of the nitro-compound and electro-reduction to the corresponding amine, resulting in the attachment of considerable amounts of the nitro-compound to the carbon fibres.The ion-exchange capacity is estimated to be ca. 1 mequiv. g−1 and with slight deviations it follows the rank Ag, Cu, Cd, Pb, Hg. After the electro-reduction of the exchanged metal ions, the ion-exchange process can be repeated several times. This procedure is of importance for the removal of significant amounts of heavy and toxic metals from industrial waste waters. Key words: electro-oxidized carbon fibres, adsorption of aromatic nitro compounds, cation-exchange of heavy metals.