Electrochemical degradation of gallic acid on a BDD anode.

The electrochemical oxidation of gallic acid (3,4,5-trihydroxybenzoic acid) has been studied on a boron-doped diamond anode (BDD). Cyclic voltammetries, chronoamperometries and bulk electrolyses were performed to characterise the electrochemical behaviour of gallic acid on diamond-type anode and to study the kinetics of gallic acid degradation. UV spectroscopy, HPLC analysis, COD and TOC measurements were conducted to study the reaction pathway for gallic acid mineralisation. The results showed that both direct and mediated electrochemical processes were involved in the oxidation of gallic acid. The degradation of gallic acid evidenced a pseudo first-order kinetics and the rate constant increased with applied current. Aliphatic acids were the main intermediates formed during the electrolyses and they were finally mineralised to CO(2) and water. The degradation rate on boron-doped diamond was under mass-transport control and was favoured by the increase of the flow rate of the solution into the electrochemical reactor.