【作者】 吴梅芬；

【导师】 赵国华；

【作者基本信息】 同济大学 ， 物理化学， 2006， 硕士

【摘要】 金刚石膜（Boron-doped Diamond简写为BDD）电极是一种新颖的电极，由于它具有电极表面化学性质稳定，电化学催化性能优良，电催化性能不易失活，电极的电势窗口宽，尤其具有高析氧电位等电催化氧化阳极应具备的特性而成为国际环境学科和电化学学科广泛关注的电极材料。本文以BDD电极为工作电极，研究了一些典型的有机污染物如苯、染料分子次甲基蓝、芳香羧酸分子在BDD电极上的氧化反应特性；采用恒电流降解方法，并结合电化学方法和紫外可见分光光度法与高效液相色谱法等分析手段研究了这些难生化、难氧化的有机污染物在BDD电极上的降解效果和电化学氧化机理。（1）实现了难生化难氧化降解的芳香分子苯在BDD电极上的电化学氧化降解。以BDD电极为阳极，纯钛板为阴极，阳极有效面积为5.0cm²，固定电极间距为10mm，50ml初始浓度为1019.5mg/L的苯溶液，电解电流密度的为10mA／cm²，电化学氧化反应11小时后，其TOC去除率能达到94.3％能得到彻底的降解。。采用现场的微分咏冲伏安法、紫外可见光谱、和高效液相色谱技术研究表明，苯在降解过程初步氧化生成苯酚、对苯二酚、间苯二酚和邻苯二酚等中间产物，随着降解过程中羟基自由基的不断产生，初始反应物苯以及酚类氧化中间产物在BDD电极上失去电子或在羟基自由基作用下继续氧化开环，生成草酸、顺丁烯二酸等脂肪酸小分子，脂肪酸进一步矿化降解。由于苯的氧化电位高达2.8V，采用电化学这种温和氧化方式将芳香烃分子得以去除，具有重要的理论研究意义和实际应用价值。（2）次甲基蓝分子在BDD电极上在有氯和无氯离子介质中的氧化降解研究。对比BDD、Pt、石墨、DSA四种电极在无氯和有氯离子的介质中的线性扫描伏安实验表明，BDD电极具有最高的析氧电位，有利于有机物在电极表面的直接电化学氧化，表明BDD电极非常适用于对无Cl^-介质体系中有机污染物的直接电化学降解处理；相反，BDD电极上的析氯电位最高，不利于生成氯气进行间接氧化降解污染物，不利于提高间接氧化的电流效率，不能发挥BDD电极的优异的电化学性能。高浓度的次甲基蓝染料废水的降解结果也表明，BDD电极比其它各类电极更适于在无氯离子介质中的直接电化学氧化降解，氧化电流效率几乎可达到100％，COD的降解动力学方程符合一级反应模型，其降解速率常数为0.0089lmin^-1。降解过程的紫外可见光谱、电化学分析方法的动态变化检测也表明，次甲基蓝氧化的COD去除速率与染料脱色速率是同步的，这说明次甲基蓝分子在BDD电极上的氧化是其整个分子结构的共轭体系的完全破坏，染料分子由此得以脱色，矿化。（3）研究了采用BDD电极的电化学氧化方法与超声处理方法的联用技术和降解过程。比较了电化学氧化、超声处理与超声—电化学氧化三种方式对邻苯二甲酸降解的结果。单一的超声处理不能使邻苯二甲酸降解，单一BDD电极电化学氧化方法对邻苯二甲酸的降解可取得较理想效果，电极面积为3.85cm²，电极间距为10mm，电流密度为20mA／cm²，模拟废水处理体积为20mL，进行电解反应，4个小时后TOC的去除率达到100％。采用超声与电化学氧化联用处理时，能大大加快邻苯二甲酸的降解，经1.5小时后邻苯二甲酸的TOC去除率达到99.37％，这表明超声对BDD电极电化学氧化过程起到很有效的强化作用，超声—电化学氧化协同处理是一种更为高效的污染物降解方法。更多还原

【Abstract】 As a new kind of the most popular electrode materials, boron-doped diamond (BDD) film electrode exhibits several excellent electrochemical properties that electrochemical catalytic anodes should possess, including high electrochemical stability, excellent and hardly deactivated catalytic property, a wide electrochemical potential window in either aqueous or non-aqueous media, and especially high oxygen evolution potential which makes BDD a prevalent electrode extensively concerned in the domestic and foreign environment and electrochemistry discipline. In this paper, BDD electrode, as a work electrode, was firstly adopted to study the electrochemical oxidation behavior of several typical organic pollutants, such as benzene, methylene blue, aroma acid. Then the degradation efficiency and the mechanism of electrochemical oxidation of these non-biodegradable and refractory organic pollutants at BDD electrode was investigated by galvanostatic oxidization degradation combined with other electrochemical techniques, UV-VIS spectrum and HPLC.The electrochemical oxidation degradation of a non-biodegradable and refractory aromatic molecule, benzene, at BDD electrode was realized. Under the current density of 10mA/cm~2, electrode area of 5cm~2, solution volume of 50ml, after 11 hours of electrochemical oxidation, the removal efficiency of TOC was achieved to be 94.3%, which means benzene at BDD electrode could be completely degraded. Moreover, in situ differential pulse voltamrnetry, UV-VIS spectrum and HPLC were used to investigate the degradation process. It was observed that during the whole process, the intermediate products of benzene primarily oxidized at BDD electrode were phenol, hydroquinone, resorcin, catechol and etc. With this process proceeding, a great amount of hydroxyl radicals emerged nearby BDD electrode, the initial and remnant benzene plus the above phenol-like intermediates was further losing electrons or subjected to these hydroxyl radicals attacking. As a result of this, these rings of benzene and phenol-like intermediates were opened. And these substances were converted into little molecules of fatty acids, such as oxalic acid and maleic acid which would be further degraded. As well-known, the oxidation potential of benzene is achieved as high as 2.8V, which makes the moderate oxidation and degradation of aromatic compounds by electrochemical technique of great significance in the field of both theoretical research and practical application. With and without chlorine presented in supporting electrolyte, the oxidation degradation of methylene blue at BDD electrode was studied respectively. The following results at BDD electrode were compared with the ones at Pt, Graphite, and DSA electrode. And it was found that the direct electrochemical oxidation of organic compounds at BDD electrode proceeded more facilely because of the higher oxygen evolution potential ofBDD electrode. It indicates that BDD electrode is fit for the direct electrochemical degradation of organic pollutants under the condition of no chlorine presented in supporting electrolyte. On the contrary, due to the same higher chlorine evolution potential at BDD electrode, it is much harder for BDD electrode to generate a great amount of chlorine which can degrade organic pollutants indirectly. Hereby, it is not of avail for increasing the current efficiency of indirect oxidation. So the unique electrochemical property of BDD electrode will not be exerted effectively. The degradation results of concentrated methylene blue solution shows that BDD electrode, compared with the other electrodes, is suitable for direct electrochemical degradation with no chlorine presented in supporting electrolyte. And the current efficiency of degradation was almost achieved to be 100%. The kinetics formula of degradation calculated from the COD values agreed with the model of first-order reaction quite well. And the degradation rate constant was calculated to be 0.00891rain-1. During the degradation process of methylene blue, the dynamic analytical data obtained from UV-VIS spectrum and electrochemical techniques indicated that the removal rate of COD and decoloration rate were isochronous, which means the whole molecule conjugate system of methylene blue was completely destructed during the oxidation process at BDD electrode. The dye molecules were therefore decolored and mineralized.The electrochemical oxidation technique at BDD electrode with ultrasound electric microfield degradation was explored. And the results gained from three methods, electrochemical oxidation, ultrasound electric microfield degradation, and electrochemical oxidation-ultrasound electric microfield degradation, were compared for the degradation of phthalic acid. It was obtained that the degradation of phthalic acid could not be achieved by only ultrasound electric microfield degradation, while the degradation efficiency of phthalic acid through only electrochemical oxidation at BDD electrode was perfect. Under the condition of current density of 20mA/cm~2, electrode area of 3.85cm~2, solution volume of 20ml, after 4 hours of electrochemical degradation, the removal efficiency of TOC was achieved to be 100%. The degradation rate of phthalic acid could be enhanced highly by electrochemical oxidation with ultrasound electric microfield degradation It was calculated that after 1.5 hours of degradation, the removal efficiency of TOC was 99.37%, which indicates that ultrasound electric microfield has an effective and strengthening effect on the oxidation process at BDD electrode. As a conclusion, we believe that the cooperative treatment through ultrasound electric microfield with electrochemical oxidation should be one of the most effective degradation techniques for the degradation of pollutants.更多还原