【作者】 段小月；

【导师】 袁中新； 马放；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2013， 博士

【摘要】 电催化氧化技术能有效降解生物难降解有机污染物，并具有二次污染风险小和操作灵活等优点，受到国内外研究者的青睐。电极材料是电催化氧化技术的核心，与电催化氧化过程中有机物降解效果和电流效率密切相关。本文以二氧化铅电极的改性为主要内容，开展了电极电沉积条件优化、改性，以及电催化氧化降解水中酚类污染物效能等方面的研究工作。主要研究内容和结果如下：采用热沉积法制备了Ti基PbO₂电极的SnO₂-Sb₂O₃底层，采用电沉积法制备了电极的α-PbO₂中间层和β-PbO₂表面活性层。利用扫描电子显微镜（SEM）、X射线衍射仪（XRD）、开路电位及电催化氧化实验研究了电沉积条件对α-PbO₂中间层和β-PbO₂表面活性层形貌、结构与性能的影响。确定α-PbO₂中间层的优化条件为：电流密度3mA/cm²，电沉积温度40℃，电沉积时间1h；β-PbO₂表面活性层的优化条件为：电流密度15mA/cm²，电沉积温度65℃，电沉积时间1h。利用β-PbO₂电极电催化氧化降解水中苯酚，研究了苯酚降解过程中有机物矿化、降解动力学、电流效率和能耗情况，并利用高效液相色谱（HPLC）检测分析了苯酚降解的中间产物，提出苯酚可能的降解路径。循环伏安曲线表明苯酚可以被β-PbO₂电极直接氧化，该氧化过程受吸附过程控制。β-PbO₂电极电催化氧化降解苯酚过程符合一级反应动力学规律。通过向β-PbO₂电极的电沉积液中添加碳纳米管（CNT）制备了CNT改性PbO₂电极（CNT-PbO₂）。但CNT的单独添加并不能将CNT掺杂到β-PbO₂电极的膜层中，故在电沉积液中又添加了表面活性剂，在表面活性剂的作用下可成功地将CNT掺杂到β-PbO₂电极的膜层中。对比研究了阴离子表面活性剂十二烷基苯磺酸钠（LAS）和阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）对CNT掺杂效果的影响。SEM和X射线能谱分析（EDS）结果表明，在阴离子表面活性剂的作用下有更多的CNT掺杂到膜层中。在LAS作用下制备的CNT改性PbO₂电极（LAS-CNT-PbO₂）具有更高的电催化活性、电流效率和使用寿命，对4-CP的降解速率和使用寿命分别为传统β-PbO₂电极的2.35和1.87倍。利用LAS-CNT-PbO₂电极对水中毒性有机污染物4-氯酚（4-CP）的氧化情况进行了研究。首先，采用循环伏安技术研究了pH值、温度和4-CP浓度对4-CP氧化反应的影响。结果表明：碱性体系有利于4-CP的氧化，随着温度和4-CP浓度的升高，4-CP氧化峰电位负移。然后，研究了LAS-CNT-PbO₂电极电催化氧化降解4-CP过程中，电流密度、4-CP初始浓度、电解质浓度和温度等实际操作条件对4-CP去除率、有机物矿化、降解动力学和电流效率的影响。在LAS-CNT-PbO₂电极电催化氧化4-CP过程中，电流密度越高和4-CP初始浓度越低，有机物的矿化程度越高，但电流效率越低。温度越高，4-CP和TOC去除率越高，电流效率越高。电解质浓度对电催化氧化过程的影响不大。4-CP的降解过程符合一级反应动力学规律。此外，利用HPLC对4-CP降解的中间产物进行了鉴定，推测出4-CP的可能降解路径，并考察了降解液的可生化性与毒性变化，结果表明，降解120min后，4-CP降解液的可生化性明显提高，毒性明显降低。向LAS-CNT-PbO₂电极的电沉积液中添加Ce（NO3）3，制备了Ce与CNT复合改性PbO₂电极（Ce-LAS-CNT-PbO₂）。由SEM、EDS和XRD结果可知， Ce与CNT确实被引入到了Ce-LAS-CNT-PbO₂电极中，Ce-LAS-CNT-PbO₂电极具有较β-PbO₂、Ce-PbO₂和LAS-CNT-PbO₂电极更小的晶粒尺寸和更大的活性表面积。由[Fe（CN）6]4–/[Fe（CN）6]3–体系中的循环伏安、羟基自由基产生能力测试、电催化氧化4-CP实验及加速寿命实验结果可知，Ce与CNT的复合掺杂可在LAS-CNT-PbO₂电极的基础上进一步提高了PbO₂电极的电催化活性和使用寿命。比较Ce-LAS-CNT-PbO₂电极和Ce-CNT-SnO₂电极发现，虽然前者的电催化活性低于后者，但前者的使用寿命却远远长于后者。更多还原

【Abstract】 The electro-catalytic oxidation technology attracts extensive attention becauseof its effectiveness in the degradation of bio-refractory organic pollutants,environmental compatibility and easy implementation. The material of electrode, asthe key of electro-catalytic oxidation, is closely related to the degradation efficiencyof pollutants and the current efficiency of electro-catalytic oxidation process.Therefore, in present work, the lead dioxide electrode was modified, theelectrodeposition conditions of lead dioxide electrode were optimized, and theelectrochemical degradation of phenolic pollutants was studied with the lead dioxideelectrodes. The main research contents and results were summarized as follows:The SnO₂-Sb₂O₃interlayer of PbO₂electrode was prepared by thermaldecomposition. The α-PbO₂intermediate layer and β-PbO₂top layer of PbO₂electrode were prepared by electrodeposition. Scanning electronic microscopy（SEM）, X-ray diffraction （XRD）, open-circuit potential and electrochemicaloxidation of phenol were used to investigate the effect of electrodepositionconditions on the morphology, crystal structure and properties of α-PbO₂intermediate layer and β-PbO₂top layer. The experimental results showed that theα-PbO₂interlayer was prepared under optimum conditions: current density is3mA/cm², temperature is40℃and time is1h; β-PbO₂interlayer was prepared underoptimum conditions: current density is15mA/cm², temperature is65℃and time is1h.The electrochemical oxidation of phenol in aqueous solution was studied usingβ-PbO₂electrode as anode. The removal, mineralization and degradation kinetics ofphenol were studied and the current efficiency and energy consumption werecalculated during the course of electrolysis. In addition, the intermediates generatedin the degradation of phenol were indentified using high-performance liquidchromatography （HPLC） and a general pathway for the electrochemical degradationof phenol on β-PbO₂anode was proposed. The cyclic voltammetric curves indicatedthat phenol could be directly oxidized on β-PbO₂electrode, and this oxidationprocess was controlled by adsorption process. The phenol degradation on β-PbO₂electrode always followed a pseudo-first-order kinetics.Carbon nanotube （CNT） modified PbO₂electrodes （CNT-PbO₂） were fabricatedby adding CNT into the electrodeposition solution. However, CNT couldn’t bedoped into β-PbO₂films when the CNT was added alone. Thus, the surfactants werealso added into electrodeposition solution, and then CNT could be successfully doped into β-PbO₂films under the synergistic effect of surfactants. The influence ofcationic surfactant etyltrimethylammonium bromide （CTAB） and anionic surfactantlauryl benzene sulfonic acid sodium （LAS） on the doping of CNT was compared.The results of SEM and Energy Dispersive X-ray Spectrometer （EDS） showed thatmore CNT could be doped into β-PbO₂film under the synergistic effect of LAS.Polarization curves and cyclic voltammetry were adopted to measure theelectrochemical properties of these PbO₂electrodes. The CNT-PbO₂electrodeprepared with LAS （LAS-CNT-PbO₂） had higher activity, higher current efficiencyand longer lifetime. The degradation rate of4-CP and lifetime of LAS-CNT-PbO₂electrode was2.35and1.87times higher than those of β-PbO₂electrode,respectively.The oxidation process of4-chlorophenol （4-CP） was studied onLAS-CNT-PbO₂electrode in detail. First, the cyclic voltammetry technology wasexclusively used to study the effect of pH, temperature and4-CP concentration onthe oxidation of4-CP. The results indicated that4-CP was oxidized more easily inalkaline medium than acidic and neutral mediums, and the oxidation peaks of4-CPshifted toward lower potential values with increasing temperature and4-CPconcentration. Secondly, the effect of operating conditions of initial4-CPconcentration, current density, supporting electrolyte concentration, and temperatureon the removal and mineralization of4-CP, current efficiency, and kinetics were alsoinvestigated during electro-catalytic oxidation of4-CP on LAS-CNT-PbO₂electrode.The experimental results showed that higher mineralization of organic compoundsand lower current efficiency was obtained by higher current density and lower initial4-CP concentration; the higher the temperature, the higher the4-CP and TOCremoval ratios; the concentration of supporting electrolyte is not the significantparameter in this process. The4-CP degradation always followed apseudo-first-order kinetics. HPLC was employed to identify the products resultingfrom the electrochemical degradation of4-CP and the degradation pathways of4-CPwere proposed. Besides, the biodegradability and the toxicity of4-CP degradationsolution were investigated. The results showed that, after120min ofelectro-catalytic oxidation, the biodegradability of degradation solution wasimproved and the toxicity was decreased significantly.Ce and CNT co-doped PbO₂（Ce-LAS-CNT-PbO₂） electrode was prepared byadding Ce（NO3）3into the electrodeposition solution of LAS-CNT-PbO₂electrode.The results of SEM, EDS and XRD revealed that Ce and CNT had been introducedinto Ce-LAS-CNT-PbO₂electrode. Compared with β-PbO₂, Ce-PbO₂, andLAS-CNT-PbO₂electrodes, Ce-LAS-CNT-PbO₂electrode had smaller grain size and higher active surface area. The results of cyclic voltammetry tests in[Fe（CN）6]4–/[Fe（CN）6]3–system, determination of hydroxyl radical generation,electro-catalytic oxidation degradation of4-CP and accelerating lifetime testsexhibited that the co-doping of CNT and Ce further improved the electro-catalyticactivity and lifetime of PbO₂electrode based on LAS-CNT-PbO₂electrode. Thecomparison of Ce-LAS-CNT-PbO₂electrode and Ce-CNT-SnO₂electrode indicatedthat the electro-catalytic activity of former was superior to that of latter, but theservice life of latter was far longer.更多还原