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Electrochemistry Degradation of Organic Pollutants with Boron-doped Diamond (BDD) Electrode

Author: WuMeiFen
Tutor: ZhaoGuoHua
School: Tongji University
Course: Physical and chemical
Keywords: Diamond film electrode ( BDD ) Electrochemical oxidation Ultrasound Benzene (Methylene blue) Phthalate High Performance Liquid Chromatography UV - visible spectrum Degradation mechanism
CLC: X703
Type: Master's thesis
Year: 2006
Downloads: 84
Quote: 0
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Abstract

A diamond film (Boron-doped Diamond abbreviated BDD) electrodes is a novel electrode, due to it having an electrode surface the chemically stable excellent electrochemical catalytic performance, the electrocatalytic performance is difficult to inactivation, the electric potential of an electrode width of the window, in particular having high oxygen evolution potential, such as the electrocatalytic oxidation anode should have the characteristics of international environmental disciplines and electrochemical disciplines widespread concern electrode material. BDD electrode as the working electrode of a typical organic pollutants such as benzene, dye molecules (methylene blue), aromatic carboxylic acid molecules on the BDD electrode oxidation reaction characteristics; constant current degradation, combined with electrochemical methods spectrophotometry and high performance liquid chromatography and ultraviolet-visible spectroscopy were used to study these biorefractory, difficult oxidation of organic pollutants degradation effect on the BDD electrode and electrochemical oxidation mechanism. (1) hard biodegradable difficult oxidative degradation of aromatic molecules benzene the BDD electrode electrochemical oxidation degradation. BDD electrode as an anode, a titanium plate as a cathode, an anode active area of ??5.0cm ^{2 , the fixed electrode spacing of 10mm, 50 ml of the initial concentration of 1019.5mg / L benzene solution for electrolytic current density 10mA/cm ^{2 , the electrochemical oxidation reaction after 11 hours, the TOC removal rate can reach 94.3% can be thoroughly degradation. . Site Differential Wing punch voltammetry, UV-visible spectroscopy, and high performance liquid chromatography technique study showed that the initial oxidation of benzene in the degradation process to produce phenol, hydroquinone, resorcinol and catechol intermediates, With the continuous generation of hydroxyl radicals in the degradation process, the initial reactants benzene and phenolic oxidation intermediates in the BDD electrode loses electrons or open-loop under the action of hydroxyl radical oxidation generated oxalic acid, maleic acid and other fatty acids small molecules, further mineralized degradation of fatty acids. Benzene oxidation potential of up to 2.8V, using electrochemical this mild oxidation of the aromatic hydrocarbon molecules can be removed, has important theoretical significance and practical value. (2) methylene blue molecules in the BDD electrode in the oxidative degradation of chlorine and chlorine-ion medium. Comparison of four electrodes in the BDD, Pt, graphite, DSA chlorine and linear sweep voltammetry experiments show that the chloride ions in the medium The BDD electrodes having the highest oxygen evolution potential, is conducive to direct electrochemical oxidation of organic matter in the surface of the electrode, that the BDD electrode is ideal for direct electrochemical degradation of organic pollutants on the Cl ^{- medium system processing; contrary, is not conducive to generate chlorine indirect oxidation potential of chlorine evolution on the BDD electrode degradation pollution material not conducive to improving the current efficiency of the indirect oxidation, can not play excellent electrochemical performance of the BDD electrode. High concentrations of the degradation of methylene blue dye results also show that more than other types of electrodes, the BDD electrode suitable for direct electrochemical oxidation degradation, oxidation current efficiency can reach 100% in almost no chlorine ions in the medium, the COD degradation The kinetic equation of the first order reaction model, the degradation rate constant 0.0089lmin ^{-1 . Its degradation process of ultraviolet-visible spectroscopy, electrochemical analysis method also shows that the dynamic change detecting times methylene blue oxidized COD removal rate and decolorization rate is synchronous, indicating that the oxidation of the methylene blue molecules in BDD electrodes the complete destruction of the entire molecular structure of a conjugated system, the dye molecules is thereby decolorization mineralization. (3) Study of the the BDD electrode electrochemical oxidation method with ultrasonic processing method associated with the degradation process. The electrochemical oxidation, ultrasonic treatment with ultrasound - the results of electrochemical oxidation of three ways phthalate degradation. Single ultrasonic treatment can not make a phthalate degradation, the single BDD electrode electrochemical oxidation method of phthalic acid degradation can obtain a more satisfactory result, an electrode area of ??3.85cm ^{2 , electrode spacing of 10mm the current density was 20mA/cm ^{2 , the simulated wastewater treatment volume to 20mL, and the electrolytic reaction, and the TOC removal rate reached 100% after 4 hours. Combined with ultrasound and electrochemical oxidation treatment can greatly accelerate the degradation of phthalic acid, TOC removal reached 99.37% after 1.5 hours of phthalic acid, suggesting that ultrasound the BDD electrode electrochemical oxidation process play a very an effective role in strengthening, ultrasound - co-processing of electrochemical oxidation degradation of pollutants is a more efficient method.}}}}}}

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