【作者】 陈金銮；

【导师】 施汉昌；

【作者基本信息】 清华大学 ， 环境科学与工程， 2008， 博士

【摘要】 本文从电化学反应具有氧化和微气泡同步发生的特点出发,提出对电化学氧化氨氮和活性污泥的电解浮选进行研究。对氨氮电化学氧化的影响因素,电极表征,氨氮电化学氧化特征、降解机理、产物和动力学,电极材料研制,电解浮选进行活性污泥固液分离进行了系统的研究,并设计了新型的化学强化生物流化复合反应器,用于污水处理。获得的主要结论如下:电极反应是氨氮电化学反应的控速步骤;电流密度、氯离子浓度、电极材料是影响氨氮电化学氧化去除的主要因素;初始水温和极板间距的影响不大;弱碱性条件下,有利于氨氮的氧化去除;Mg²⁺、Ca²⁺、Sn²⁺、Fe²⁺、Al³⁺等金属离子,HCO₃^-、CO₃^2-和NO₃^-等阴离子对氨氮去除的影响比较小;SO₄^2-和PO₄^3-对氨氮去除影响较大,NO₂^-和氨氮的氧化存在竞争,NO₂^-优先于氨氮氧化;COD和氨氮都可以被电化学氧化去除,且氨氮的氧化占主导地位,优先于COD的降解。直接电化学氧化和间接电化学氧化是氨氮电化学氧化的两种方式。在低氯离子浓度（[Cl-]<500mg/L）下,电化学氧化过程中产生的羟基自由基浓度约10-15 mol/L,氨氮主要通过电化学氧化产生的游离氯氧化去除。电化学氧化产物与体系组成及pH值有关,在氯离子存在的情况下,产物主要是N2和少量的氯胺及硝酸根。氨氮的电化学氧化过程符合表观一级动力学规律,反应的活化能为19.81kJ/mol。动力学经验方程可以表示为:3种Ti/RuO₂基电极材料的析氧、析氯过电位较低,氯、氧过电位差较小,导致氨氮电化学氧化的电流效率不高（低于30%）。单扫伏安曲线表明氨氮在3种电极材料上的电催化反应很小,基本上是析氧、析氯反应。SEM和加速寿命测试试验表明,3种DSA阳极具有较好的电化学稳定性,适合用于废水处理。研究了热分解氧化法制备锡锑电极的影响因素,制备的Ti/SnO₂-Sb₂O₃电极对氨氮的直接电化学氧化效果较好,Ti/SnO₂-Sb₂O₃（-CeO₂）电极与Ti/RuO₂-TiO₂电极对氨氮的间接电化学氧化效果相当,但价格更为低廉。采用不溶性阳极的电解浮选工艺能高效地进行活性污泥固液分离。在双筒式内循环三相生物流化床顶部耦合电解浮选单元形成具有自主知识产权的新型复合反应器,对模拟生活污水进行处理研究,可进一步提高24%的氨氮去除率。更多还原

【Abstract】 Based on the functions of electrochemical reaction with the oxidation and microbubble production, the research of ammonia oxidation and activated sludge separation by electrolysis was proposed. The factors that affected ammonia electro-oxidation, characterization of electrode and ammonia electro-oxidation, oxidation mechanism, oxidation products and dynamic kinetics, preparation of electrode materials, the feasibility of electro-flotation for the solid-liquid separation of activated sludge were investigated. A novel chemical enhanced biological fluidized reactor was developed and applied for wastewater treatment. The following results were achieved.Electrode reaction was the reaction rate control step for ammonia electro-oxidation. Current density, chloride concentration and electrode material were the main factors for ammonia electro-oxidation. The influence of initial water temperature and electrode gap was rather little. Under alkalescence condition, the chloride ion would transform in a circle, it was favourable for ammonia removal. Metal ion such as Mg²⁺, Ca²⁺, Sn²⁺, Fe²⁺, Al3+, and anion such as HCO3-, CO32- and NO3- had little effect on ammonia electro-oxidation removal, but SO42- and PO43- had significant effect. There were completive oxidation between NO₂^- and ammonia, NO₂^- was oxidized prior to ammonia oxidation. COD and ammonia can be removed simultaneously by electrochemical oxidation and the removal of ammonia is the dominant reaction in this method.In the electrochemical process, ammonia was removed by either direct or indirect electrochemical oxidation process. When the concentration of chloride was low （[Cl-]<500mg/L）, the hydroxyl radicals produced during electrochemical process was about 10-15mol/L, the free chlorine produced during electrochemical process had significant effect on ammonia oxidation. The oxidation products of ammonia related with the content of electrolyte and pH. When chloride presented, the main product was N2, a little chloramine and NO3-. The ammonia electro-oxidation followed pseudo-first-order kinetics. The reaction activation energy was 19.81kJ/mol. The dynamic kinetic equation could be expressed as:The over-voltages of three types of Ti/RuO₂-based electrode of oxygen evolution and chlorine evolution were low, and the difference of over-voltage between oxygen evolution and chlorine evolution was very small, which resulted in a low current efficiency of ammonia electro-oxidation （lower than 30%）. The voltammetry curves showed that the electro-catalytic of ammonia on these three type electrodes was small and the main reactions were oxygen evolution and chlorine evolution. SEM and accelerated life test showed that these three types of DSA anode with good electro -chemical stability. They were suitable for wastewater treatment.The factors that affected the preparation of tin and antimony oxide electrode by thermal decomposition were investigated. The Ti/SnO₂-Sb₂O₃ electrode showed good performances of direct electro-oxidation of ammonia. Ti/SnO₂-Sb₂O₃ （-CeO₂） electrode had the same effect as well as Ti/RuO₂-TiO₂ electrode on indirect electro-oxidation of ammonia, but the Ti/SnO₂-Sb₂O₃（-CeO₂） electrode was cost effective.Electro-flotation using inert anode is a high efficiency technology for the solid-liquid separation of activated sludge. Combined the inner circulation three phase biological fluidized bed reactor with electrochemical technology, a novel chemical enhanced biological fluidized reactor was developed. Applied the new reactor for synthetic municipal wastewater treatment, the ammonia removal ratio increased 24%.更多还原