The degradation of 4-chiorophenol in acidic solution of pH -3.5 has been studied by different electrochemical methods involving 11202 electrogeneration from an 02-diffusion cathode. While the solution is slowly mineralized by anodic oxidation in the presence of 11202, the rate for organic carbon removal increases notably by electro-Fenton, photoelectro-Fenton, and peroxi-coagulation, where Fe2 acts as catalyst to produce oxidizing 0H from electrogenerated H202. 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 Fe(OH)3 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. Fe3 complexes are produced in the processes using iron ions. These complexes are slowly mineralized by electro-Fenton and rapidly photodecomposed to CO2 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.
A novel electrochemical method for wastewater treatment, called peroxi‐coagulation, is presented in this paper. Degradation of aniline in acidic solution of pH ∼ 3 has been studied using this method. Electrolyses were performed in an undivided cell with an Fe anode and a carbon‐polytetrafluoroethylene
O2
‐fed cathode which continuously electrogenerates
H2O2
. The anode dissolves yielding
Fe2+
and
Fe3+
. This last ion gives a precipitate of hydrated Fe(III) oxide. Aniline and its intermediates are oxidized mainly by reaction with OH•, which is produced from Fenton's reaction between electrogenerated
H2O2
and
Fe2+
. Competitive coagulation of oxidation products with the hydrated Fe(III) oxide precipitate also occurs. These processes allow a fast and almost complete total organic carbon removal for aniline solutions in short‐time electrolyses. The method has higher decontamination power than other electrochemical treatments tested, such as electrocoagulation with a graphite cathode, and electro‐Fenton and photoelectro‐Fenton with a Pt anode. Benzoquinone, nitrobenzene,
NH4+
, and
NO3−
were detected in electrolyzed solutions. Precipitates contain coagulated organics with a major proportion of nitrogen‐containing compounds. A pathway for aniline peroxi‐coagulation involving these species is proposed.
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