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This dissertation, Electrochemical Wastewater Treatment for Denitrification and Toxic Organic Degradation Using Ti-based SnO2 and RuO2 Electrodes by Zhaoming, Xie, 謝昭明, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Electrochemical Wastewater Treatment for Denitrification and Toxic Organic Degradation Using Ti-based SnO and RuO Electrodes 2 2 submitted by Xie, Zhaoming for the degree of Doctor of Philosophy at the University of Hong Kong in December 2006 Many wastewater pollutants, including toxic organic compounds and nutrients at a high concentration, are difficult to treat with conventional treatment processes. Wastewater treatment technologies require continuous advances to ensure that the effluent continues to comply with more stringent discharge standards and to improve the cost-effectiveness of the practice. The electrochemical (EC) method is an advanced oxidation process that has shown promise as an effective treatment alternative for wastewater containing toxic substances. This study focused on the development of the electrochemical technology for degradation of aromatic and chlorinated aromatic organic pollutants and for nitrogen removal from landfill leachate and sewage sludge liquor. A double-layer coating technique was employed to make titanium-based catalytic active electrodes in Ti/SnO-Sb-Al for EC organic oxidation. The experimental results show that the Ti/SnO -Sb-Al anode is much more effective for electrolysis of phenol and chlorophenol than other conventional anodes of Pt, Ti/RuO and Ti/IrO . For phenol (100 mg/L) treatment, complete organic removal was 2 achieved after 5 hrs on anode Ti/SnO -Sb-Al at 20 mA/cm, compared with only 36% and 12% organic reductions provided by the Pt and Ti/RuO anodes, respectively. Similarly, for chlorophenol electrolysis, the best treatment performance was obtained with anode Ti/SnO -Sb-Al, followed by Pt and then Ti/RuO . Analysis with the High 2 2 Performance Liquid Chromatography (HPLC) revealed many intermediate products during the EC process, from aromatic compounds to aliphatic acids, which were oxidized rapidly by Ti/SnO -Sb-Al but accumulated in the Pt and Ti/RuO cells. In 2 2 addition, formation of colored polymeric materials occurred in the Pt and Ti/RuO electrolyzed solutions. Based on the EC degradation performance and the HPLC results, modified pathways of phenol and chlorophenol electrolysis at different types of electrodes were proposed. The different electrodes were characterized for their electrochemical behavior and surface properties. Compared to the Pt and Ti/RuO anodes, Ti/SnO -Sb-Al had a 2 2 considerably higher overpotential of oxygen evolution according to the voltammograms, which would facilitate the production of hydroxyl radicals. Direct phenol and chlorophenol oxidation could take place on the Ti/SnO -Sb-Al surface but not on the Pt and Ti/RuO anodes. The Ti/SnO -Sb-Al electrode also had apparently a 2 2 higher affinity with organic substances than Ti/RuO . It is argued that the anodic property has a significant influence on the kinetics, pathway and mechanism of organic electrolysis. Specific surface treatment such as the SnO -Sb-Al coating provides the anode with a catalytic function for rapid degradation of toxic organics. In addition, electrochemical denitrification experiments were performed using a lab-scale system with Ti/RuO -based mesh electrode plates for treating saline sewage sludge li

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