Dual Electrodes Oxidation of Dye Wastewater with Gas Diffusion Cathode

Abstract

The high energy cost of an electrochemical method is the fatal drawback that hinders its large scale application in wastewater treatment. In traditional single-chamber electrolysis cell, only direct oxidation at an anode exists. Although a small amount of hydrogen peroxide is produced at the cathode by reduction, it is transferred to the anode and destroyed there without adding much benefit to organic decomposition. A two-chamber electrolytic cell, connected with an electrolyte bridge, was developed in this work. In this new reactor, direct oxidation at anode and indirect oxidation by hydrogen peroxide at cathode can occur simultaneously. Therefore "dual electrodes oxidation" in one electrochemical reactor was achieved successfully. Compared to a traditional one cell reactor, this reactor cuts the energy cost by 50%, and thus might lead to reconsideration of the electrochemical role in wastewater treatment. A Pt/C gas diffusion electrode (GDE) is fabricated and used as a cathode fed with oxygen-containing gases to produce hydrogen peroxide. When purified air diffuses through the active layer on the GDE, oxygen is reduced to hydrogen peroxide with a high yield to decompose organics. It has been found that the direct oxidation process at an anodic zone is slightly affected by factors such as pH variation, Fe(II) existence and aeration, while indirect oxidation at the cathodic zone is strongly affected. Dye used as a model pollutant was oxidized into small organic acids in both anode and cathode regions in this electrolytic reactor. GC-MS and IR spectrum were employed to analyze the intermediates formed during the degradation. Twenty intermediates have been detected, including 14 esters, 3 acids and 3 compounds with NO2 or N-OH groups. Thereafter, the degradation pathways of dye Acid Red B are proposed.

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

“…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.…”

Performance evaluation of chemical coagulation process to treat bagasse wastewater: modeling and optimization

“…After that, the individual and interactive impacts of treatment parameters on reaction were concentrated on 3D response surface graph from created numerical models. Optimization of treatment factors for the most effective treatment productivity was completed by Derringer's desired function strategy utilizing numerical optimizing technique 17 .…”

COD reduction studies of paper mill effluent using a batch recirculation electrochemical method

“…A review of the previous work have been undertaken in order to achieve a systematic and proper procedure for accomplishing the aim of this investigation. During the review of the published material it was found that great emphasis had been put on treating various industrial effluents using electrochemical methods [5][6][7][8] . The electrochemical processes involve the direct reaction of species at electrode surface, while others involves the production of active species at the electrode and further reaction with the targeted pollutants.…”