AUTOXIDATION OF GENTISIC ACID IN AQUEOUS-MEDIA

The oxidation behaviour of gentisic acid, from which a humic acid mode l was synthesized, was studied. Electrochemical investigation coupled with Electron Spin Resonance analysis revealed the complexity of the m echanism. Coupled chemical reactions appeared after the two electron o xidation, leading to trihydroxybenzoic acids, and to dimeric compounds . The presence of methylenic groups, particularly important to mimic t he flexibility and aggregative properties of natural humic substance, was confirmed. Assuming a free radical mechanism for the chemical evol ution of humic substances, metal ions could help the reaction process, leading to efficient spin-trapping matters to be considered in water treatments. Copyright (C) 1996 Elsevier Science Ltd.