Abstract:

In this work, the effect of different phenolic substituents on the electrochemical oxidation of phenols on a boron doped diamond (BDD) electrode was investigated. The specific relationship between the position and type of substituent and the electrochemical oxidation activity on the BDD electrode was systematically studied by employing Chemical Oxygen Demand and concentration variation. Electrochemical mineralization of hydroquinone was conducted on electrodes with different oxygen evolution potentials. It was found that there exists an important relationship between the electrochemical activity and the ability to generate hydroxyl radicals. A high activity was achieved on the BDD electrode owing to its higher electro-generation ability for hydroxyl radicals. The mineralization of substituted phenols is indirectly conducted by the hydroxyl radicals and the divorce of the substituent group is the rate determining step for the mineralization process. Meanwhile, the electrochemical mineralization rate towards substituted phenol contaminants is limited by the electronic effects of the substituents. The mineralization rate increases with increasing electron donating ability of the substituent. A linear relationship is found to exist between the reaction rate and the Hammett constant during degradation of substituted phenols.

Key words: Boron-doped diamond electrode, Electrochemical oxidation, Phenol contaminants, Substituent effect