Peroxi‐coagulation of Aniline in Acidic Medium Using an Oxygen Diffusion Cathode

Abstract

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.

Electrochemical Processes for In-Situ Treatment of Contaminated Soils - Final Report - 09/15/1996 - 01/31/2001

“…Table 3.1 classifies various Fenton oxidation and related processes, including conventional Fenton (CF), electro-Fenton (EF), UV-assisted Fenton (Photo-CF or Photo-EF), electro-generation of H 2 O 2 and electro-regeneration of Fe(II). The illustrative presentation of Fenton oxidation processes is shown in Figure 3 Brillas et al, , 1997. Notation:…”

“…This process concurrently generates H 2 O 2 and regenerates Fe(II). It has been employed not only for organic synthesis, such as oxidation of alkylbenzene , benzene and fluorobenzene , phenol and chlorobenzene , and Riluzole [2-amino-5-(trifluoromethoxy)benzothiazole] (Oturan et al, 1999); but also for wastewater decontamination, such as the decomposition of phenol , chlorophenols , aniline and 4 -chlorophenol (Brillas et al, , 1997, and chlorophenoxyacid herbicides . The forth type, EF-H 2 O 2 -FeOx, combines electro-generated H 2 O 2 with a sacrificial Fe anode.…”

“…The forth type, EF-H 2 O 2 -FeOx, combines electro-generated H 2 O 2 with a sacrificial Fe anode. Brillas et al (1997) applied this process to treat aniline and 4 -chlorophenol-containing wastewaters. However, they reported that most of TOC was removed by the Fe(OH) 3 (s) precipitates instead of organic mineralization.…”

“…reported that a higher residual Fe(II) concentration was obtained in the photo-EF process and consequently, a higher TOC removal than those in the EF process. The treatment of aniline and 4 -chlorophenol wastwaters with the photo-EF process were also investigated by the same authors (Brillas et al, 1997. Among all Fenton oxidation processes, the photo-EF appears to be the most effective one.…”

“…More recently, H 2 O 2 has been electro-generated in an acidic solution by either constant potential or constant current mode for the purpose of direct application of the Fenton oxidation process DeLeon and Pletcher, 1995;Brillas et al, , 1997Brillas et al, , 1998aBrillas et al, , 1998b; Alvarez-Gallegos and Pletcher, 1999; Qiang et al, 2000). Moreover, a novel technology that generates HO 2 -in an alkaline solution but synthesizes H 2 O 2 in an acidic solution has been developed by Sudoh et al (1991).…”