Mechanism study of electrochemical oxidation in the terylene diaphragm cell
Department of Environmental Science and Engineering, Heilongjiang University, Harbin 150086, China. Journal of Environmental Sciences
(Impact Factor: 2).
By using a self-made carbon/polytetrafluoroethylene (C/PTFE) O2-fed as cathode and Ti/IrO2/RuO2 as anode, the effects of electrochemical oxidation of phenol and the coal-gas wastewater containing phenol were studied. The terylene diaphragm which kept pH >12 in cathodic compartment and pH < 1 in the anodic compartment was selected in the experiment in comparison with the other types of diaphragm. Furthermore, hydroxyl radical (HO*) was determined in the cathodic compartment of the diaphragm cell by electron spin resonance spectrum (ESR) and the fluorescence spectra. Compared with pH, the accumulated H2O2 and the COD removal of the no-diaphragm cell, the mechanism of electrochemical oxidation in the terylene diaphragm cell was supposed. The degradation of phenol was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H2O2, HO* produced by oxygen reduction at the cathode. The mineralization of phenol in the diaphragm cell was better than that in the no-diaphragm cell. When the coal-gas wastewater was treated by the electrolysis system with terylene diaphragm, the average removal efficiency of the volatile phenol and COD were 100% and 79.6%, respectively.
Available from: Bo-Tao Zhang
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ABSTRACT: The generation and transformation of radicals on the cathode of indirect electrochemical oxidation were studied by chemiluminescence (CL) and UV-Visible spectra in the reactor with a salt bridge that connected the separated chambers. The CL intensity of 4 x 10(-9) mol/L luminol on the cathode with bubbling oxygen was about seven times that of the intensity without it, which was because of the generation of reactive oxygen species (ROS). The existence of ROS, especially the generation of the superoxide radical, could be affirmed by the fact that the CL intensity of 4 x 10(-9) mol/L 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-one with bubbling oxygen was about four times that of the intensity without it. However, there was no chemiluminescence on the anode under the same condition. The change in the UV-Visible spectra of nitro blue tetrazolium and N,N-dimethyl-4-nitrosoaniline at the cathode chamber affirmed the transformation from oxygen to superoxide and hydroxyl radicals. The mechanism of the superoxide and hydroxyl radical generation and transformation on the cathode was discussed with the help of the experimental results and relative references.
Journal of Environmental Sciences 02/2008; 20(8):1006-11. DOI:10.1016/S1001-0742(08)62200-7 · 2.00 Impact Factor
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ABSTRACT: Pd/C catalyst was prepared by a hydrogen reduction method and used for making a Pd/C gas-diffusion electrode. It was fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). In the catalyst, Pd particles with an average size of 4.0 nm were highly dispersed in the activated carbon with an amorphous structure; Pd content on the surface of the Pd/C catalyst reached 1.3 at% (atomic concentration). The Pd/C gas-diffusion electrode was then used as the cathode to investigate the electrochemical degradation of pentachlorophenol (PCP) in a diaphragm electrolysis device, feeding firstly with hydrogen gas then with air, compared with the carbon/polytetrafluoroethylene (C/PTFE) gas-diffusion cathode. The Pd/C gas-diffusion cathode can not only reductively dechlorinate PCP by feeding hydrogen gas, but also accelerate the two-electron reduction of O2 to hydrogen peroxide (H2O2) by feeding air. Therefore, both the removal efficiency and the dechlorination degree of PCP exceeded 80% after 100 min, and the average removal efficiency of PCP in terms of total organic carbon (TOC) was more than 75% after 200 min by using Pd/C gas-diffusion cathode, which was better than that of the C/PTFE gas-diffusion cathode. Phenol was identified as the dechorination product using high-performance liquid chromatography (HPLC).
Water Science & Technology 02/2009; 59(9):1759-67. DOI:10.2166/wst.2009.176 · 1.11 Impact Factor
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ABSTRACT: Multifunctional gas-diffusion electrode with electrochemical reduction and oxidation properties was achieved based on the palladium-modified activated carbon (Pd/C). Pd/C catalysts were prepared using the formaldehyde reduction from nitric acid treated activated carbon and fully characterized by Boehm titration method, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cyclic voltammetry (CV) techniques. The electrochemical degradation of three typical chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) was investigated in a diaphragm electrolysis system with the Pd/C gas-diffusion electrode as a cathode, feeding firstly with hydrogen gas and then with air. The electrolysis system with 15% mass fraction nitric acid pretreated activated carbon showed better electrocatalytic activity compared to those from other mass fractions nitric acid, due to the active organic function groups increased on the surface of the activated carbon. When the ratio of Pd/C was low, Pd particles with an average size of 3.5 nm were highly dispersed in the activated carbon with an amorphous structure. The Pd/C gas-diffusion cathode cannot only reductively dechlorinate chlorinated phenols by feeding hydrogen gas, but also accelerate the two-electron reduction of O2 to H2O2 by feeding air. Therefore, the removal efficiency of chlorinated phenols reached almost 100%, conforming to the sequence of 4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol. The dechlorination of three chlorinated phenols exceeded 80% after 100 min. For H2O2 and HO existed in the catholyte, the mineralization of organic pollutants in the cathodic compartment was better than that in the anodic compartment. Finally, chlorinated organic pollutants were efficiently degraded by the combined processes of reduction and oxidation in the present system.
Applied Catalysis B Environmental 08/2012; 125:449–456. DOI:10.1016/j.apcatb.2012.06.019 · 7.44 Impact Factor
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