Voltammetric Investigations of the Reduction of Direct Orange-31 a Bisazo Dye

The electrochemical reduction of bisazo dye Direct Orange–31 has been studied at Pyrolytic graphite electrode (PGE) in the pH range 2.0–10.3. Two well-defined 4e–, 4H+ pH dependent reduction peaks (Ic & IIc ) have been observed in linear and cyclic sweep voltammetry. It has been observed that reduction of azo groups in the dye does not stop at hydrazo stage but further reduction leads to the cleavage of –NH–NH– linkage to give amino compounds as the final products. At pH 3.0 and 7.0, 4-aminosalicylic acid and 3,3'-dimethylbenzidine have been characterized as the major products of reduction. A tentative mechanism for the reduction has also been suggested.