| The electrochemical oxiadation processes have attracted a great deal of attention because of their versatility, which makes the treatment of liquids, gases and solids possible, environmental compatibility, and especially, destruction of toxic and non-biodegradable organics by direct or indirect anodic oxidation. In fact, the main reagent used here is electron, which is a clean reagent and therefore there is no need for adding extra reagent. In recent years, it is much more cried for electrochemical methods that have been successfully applied in the purification of domestic sewage, landfill leachate, tannery wastes, oil refinery wastewaters, textile wastes, etc. However, there are many desiderative problems solved for the application of electrochemical oxidation process. The aim of the present work was to investigate the electro-catalytic oxidation degradation mechanisms and processes of organic pollutants, to develop anode materials for the practical problems of electrochemical treatment of organic wastewater.It has been indirectly confirmed for the oxidation mechanisms on metal oxide anodes that the current efficiency has directly connections with anodic oxidation reaction and selectivity of anode. The studies demonstrated that the effect of anode materials in organic electrochemical degradation was greater. The major reason for this effect is the difference in hydroxyl radicals produced on the anode suface. The performance of Ti/SnO2-Sb2O5 anodespreparated by Brush Coating Thermal Decomposition is as good as by a standard spray-pyrolysis method. Ti/SnO2-Sb2O5 anodes are one of the present best anode materials in make use of organic electrochemical degradation, but its stability is poor. Ti/SnO2-Sb2O5/PbO2 anode with higher oxygen evolution over-potential and longer lifetime is the present most promising anode material for electrochemical wastewater treatment.In the electrochemical process, the pollutants are destroyed by either direct or indirect oxidation process, but the two processes are not isolated. In definite conditions, the direct or indirect oxidation process may be simultaneous carry out. In this thesis, the electrochemical oxidation process characterizations and correlative problem has been studied using DSA anodes for treatment of the refractory organic pollutants, such as anilines (dyes industry), phenols (oil refinery, petrochemical industry, pharmaceutical industry, etc.), nitrobenzenes (fine chemicals), Vanillin wastewater. The results have shown that electrochemical oxidation degradation of organic mainly occur directly on the anode, in the absence of NaCl. The key of oxidation is the production of hydroxyl radicals on the anodes. Organics are easily oxided on the high oxygen over-voltage anodes, but low oxygen over-voltage anodes.The thesis has demonstrated that the addition of chloride ions in the electrolyte caused an increase in removal efficiency, and the complete degradation of pollutants can be performed due to the participation of active chlorine, in the form of chlorine, hypochlorous acid and hypochlorite, regenerated on anode surface in the oxidation. In the presence of chloride ions, indirect oxidation of organics occurs, but also direct oxidation of organics occurs at the same time, and the complete removal of ammonia and accompanying COD reduction was achieved. The anode materials have great effect on direct oxidation of organics, but indirect oxidation of organics.Electrochemical generation of active chlorine in dilute and concentrated NaCl solutions is investigated using Ti/PbO2 anode. The active chlorine yielded by the electrolysis was significantly affected by the concentration of chloride ion, temperature, current density, pH, electrode materials, diaphragm. The effect of upwords factors is comparatively different in dilute and concentrated NaCl solutions. It was found that the active chlorine produced in the solution was is consistently higher on Ti/Ru-Ti-Sn oxide coated titanium anodes compared to Ti/PbO2 anodes. The results may be to provide as much information as possible on the practical use of electrochemical treatment for industry wastewaters.The electrochemical oxidation in aqueous solution of phenol and aniline were studied on Ti/PbCh and Ti/Ru-Ti-Sn Oxide Coating Electrode. The effects of different electrodes on the electrochemical oxidation reactions and reaction intermediates of phenol and aniline were investigated using Uv-Vis spectroscopy. The electrogeneration of benzoquinones were detected by the method of high performance liquid chromatograph (HPLC). The results have shown that the oxidation and removal of phenol and aniline in aqueous solution are attributed to a further oxidation of hydroxylated products (hydroquinone and pyrocatechol). Therefore, it may be considered as the electrochemical oxidation route of phenol and aniline was same, but the route was not completely identical result from aniline occurs electrochemical polymerization. Organic structure effects on the electrochemical degradation pathway.In electrochemical oxidation process of organics, the effects of cathode are not ignored. In most case, electrochemical oxidation degradation of organics is the effect of cathodes cooperating with anodes.The experimental results indicated that the removal of COD depends on the wastewater source, electrolysis time, electrode materials, current density, chloride ion concentration, pH, electrode space, electrolytic cell structure and the flow rate. It was concluded that the electrocatalytic oxidation method could be used for the removal of COD in the wastewater. If COD is less than 30mg/L after wastewater treatment, the electric consumed is about lKWh/m3 wastewater.The chloride ion concentration and flow rate have a great effect on NH3-N concentration removal rate. For the operational conditions used in the experiments, the rate constant for NH3-N decay was with a average value of 9.0x10"^- L"'-s"s for a current density of 50mA/cm2 and a flow rate of 50ml/min. Using these parameters, 5.57Wh is consumed for the complete removal of 1L of NH3-N wastewater.The study harvests have successfully applied in industries. It has been showed that the electrochemical oxidation process is promising for industrial wastewater treatment and reuse.
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