Degradation of 4‐Chlorophenol by Anodic Oxidation, Electro‐Fenton, Photoelectro‐Fenton, and Peroxi‐Coagulation Processes

Abstract

The degradation of 4‐chlorophenol in acidic solution of pH ∼3.5 has been studied by different electrochemical methods involving electrogeneration from an ‐diffusion cathode. While the solution is slowly mineralized by anodic oxidation in the presence of the rate for organic carbon removal increases notably by electro‐Fenton, photoelectro‐Fenton, and peroxi‐coagulation, where acts as catalyst to produce oxidizing from electrogenerated . A complete mineralization was only reached in the photoelectro‐Fenton process. For peroxi‐coagulation, the removal of organic carbon in solution is mainly due to the coagulation of dechlorinated intermediates with the precipitate formed. The decay for substrate concentration is faster by electro‐Fenton and photoelectro‐Fenton than by peroxi‐Coagulation. In all methods, the initial hydroxylated intermediate is 4‐chloro‐1,2‐dihydroxybenzene, which is further oxidized with loss of chloride ion to yield maleic and fumaric acids. complexes are produced in the processes using iron ions. These complexes are slowly mineralized by electro‐Fenton and rapidly photodecomposed to by photoelectro‐Fenton processes. The apparent current efficiencies for the mineralization processes have been determined. A general pathway for the degradation of 4‐chlorophenol by the different methods studied is proposed.