Electrochemical Destruction of Aniline and 4‐Chloroaniline for Wastewater Treatment Using a Carbon‐PTFE  O 2 ‐ Fed Cathode

Abstract

The electrochemical degradation of i00 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between I0.i and 12.7 has been studied at constant current intensity using a Pb/PbQ anode and a carbon-polytetrafluoroethylene O2-fed cathode. Under these conditions, hydrogen peroxide was electrogenerated in the cell via a two-electron reduction of oxygen gas fed to the cathode. The current efficiency for H~O2 generation depended on the applied current intensity and the background electrolyte used. The concentration decay for each contaminant with electrolysis time was followed by high pressure liquid chromotography (HPLC). Kinetic analysis of these data showed a pseudo first-order decomposition reaction for both substrates at anodic current densities of 30 mAcm -2 or higher, as well as a decrease of their half-lifetimes when current intensity increased. A gradual decrease in total organic carbon (TOC) for 0.05 tool dm 3 NaOH solutions with electrolysis time was always found. Product analysis of these electrolyzed solutions by gas chromatographymass spectroscopy (GC-MS) and HPLC allowed the detection of nitrobenzene and l-chloro-4-nitrobenzene proceeding from the anodic decomposition of aniline and 4-chloroaniline, respectively. Maleic acid was also detected as intermediate and ammonia was found as final product. Destruction of initial pollutants and intermediates is explained by their oxidative reactions with OH" and HO~ at the anode reaction layer. The effect of HO~ upon decomposition pathways of anilines is discussed.

Study on superoxide and hydroxyl radicals generated in indirect electrochemical oxidation by chemiluminescence and UV-Visible spectra

“…Several possible mechanisms of indirect electrochemical oxidation have brought forward that there are possible additional steps and other reactive oxygen intermediates involved in Reactions (2) and (3), which have been used in the indirect oxidation of organic pollution compounds (Brillas et al, 1995;Yu et al, 2006). However, to the authors' knowledge, few of them have adequate or instantaneous evidence about the generation mechanism of the reactive species.…”

“…The electrochemical oxidation process will not be economical because of the high-energy consumption that hinders its large scale application. Since the 1990s, there has been an increasing interest in the indirect oxidation of organic pollutions by reactive species such as hydrogen peroxide, which are generated on the cathode which cut the energy cost dramatically (Shen et al, 2005;Brillas et al, 1995). Although the degradation efficiency of the reactive species has been largely researched and several possible mechanisms of indirect electrochemical oxidation have brought forward, to the authors' knowledge, few of them have adequate and instantaneous evidence about the generation mechanism of the reactive species, especially radicals on the cathode.…”

Evaluation of the Electrocatalytic Activity of Antimony-Doped Tin Dioxide Anodes toward the Oxidation of Phenol in Aqueous Solutions

“…25,28 Typical layers employed in the elimination of organic compounds have this characteristic, for example, SnO 2 or PbO 2 . 1,11,23,29 The introduction of platinum in the oxide layer decreases the overpotential for OER and, therefore, the electrocatalytic performance in organic oxidation decreases according to the increase of "active" sites for hydroxyl radicals. 25 In fact, the electrodes containing platinum ͑13 atom %͒ have a lower efficiency for elimination of phenol, in good agreement with the presence of a higher concentration of chemisorbed OH · radicals.…”

Anodic Materials with High Energy Efficiency for Electrochemical Oxidation of Toxic Organics in Waste Water

“…These redox couples can be added to or present in the waste water. In irreversible process, strong oxidants like ozone Wang et al, 2006), chlorine (Panizza & Cerisola, 2003), hydrogen peroxide (Brillas et al, 1996;Brillas et al, 1995;Do & Chen, 1993) and hydroxyl free radicals etc. are generated and in-situ applied to mineralize the organic pollutants.…”