【作者】 孙宏伟；

【导师】 霍明昕；

【作者基本信息】 东北师范大学 ， 环境工程， 2013， 博士

【摘要】 随着农药的生产和使用量逐年增加，含农药的废水的排放量也越来越大。农药废水成分复杂，毒性高，因而很难处理。在能源紧缺的今天，开发高效、低耗的农药废水处理技术具有重要意义。近年来，光催化技术在有机废水处理领域中得到了广泛的研究，然而由于光催化剂量子效率低、催化活性不高等瓶颈问题，该技术应用到实际废水处理中还具有一定的困难。为了解决这一问题，本论文尝试通过贵金属沉积的方法对TiO₂纳米管膜进行改性以获得更高的光催化效率；此外还研究了纳米多孔Ta₂O₅薄膜这一钽基氮氧化物的前驱物的制备方法和性质，为后续可见光光催化剂的研究打基础。在关注农药母体对环境影响的同时，也应给予降解产物或中间体足够的重视，因为这些产物或中间体同样有可能具有高毒性或高风险。在农药降解或农药生产过程中，通常伴随有产物或中间体的排放，例如磷酸盐即是有机磷农药的降解产物之一，其对环境的危害同样不可忽视；另外，被广泛用于合成除草剂、灭菌剂等农药的肼，对环境亦有危害。目前，对于磷酸盐和肼的检测方法多为光度法或发光法，尽管这些方法准确度较高，但易受到水体颜色、浊度等因素的干扰。电化学分析技术操作简单、测试灵敏、速度快，但在以往的研究中，均存在一定的问题，或采用的电极不够稳定，使用寿命短；或测试条件比较苛刻，易产生二次污染；或电极的制备过程比较复杂等等。因此，肼和磷酸盐的测定方法还需进一步改进。本文拟以更灵敏、更稳定的电极为研究对象，开展肼和磷酸盐的电化学检测方法研究。围绕以上两个方面，本论文主要开展研究内容如下：（1）采用阳极氧化法制备TiO₂纳米管薄膜光催化剂，并对其进行Au-Pd共修饰，以有机磷农药马拉硫磷为探针考察Au-Pd沉积对光催化剂活性的影响。结果显示，光还原法修饰Au，Pd后，TiO₂纳米管薄膜形貌基本没有变化，XRD等表征分析证实了Au-Pd以富金型合金形式存在。光催化实验结果表明，Au-Pd共修饰TiO₂纳米管膜（Au-Pd-TiO₂）光催化活性明显高于未经修饰的TiO₂纳米管，反应速率常数提高1.72倍，单位级数能耗显著降低。催化活性的提高主要归因于Au-Pd的沉积改性：一方面，光生电子可以快速转移至Au-Pd上，从而抑制光生电荷载流子的复合；另一方面，电子在Au-Pd的催化作用下更易与氧分子反应生成超氧自由基阴离子（O₂）和过氧化氢（H₂O₂）。由此，光生空穴寿命得以延长，进而更有效地参与氧化反应。过氧化氢产率实验也表明，Au-Pd共修饰后，H₂O₂产率提高了1.89倍，这一结果说明还原反应也得到了加强。（2）采用阳极氧化法在有机-无机混合电解质中制备多孔Ta₂O₅纳米薄膜，考察了制备条件对薄膜形貌的影响，并利用SEM、XRD等手段进行了表征。结果显示，在阳极氧化过程中，水/磷酸含量及氟离子含量是至关重要的两个参数。较高的水或磷酸含量有利于钽金属的阳极氧化反应，得到的Ta₂O₅薄膜呈现致密的、板结片状形貌。当水含量降低后，如采用水含量为10%的乙二醇为电解质溶液，同时提高氟化铵含量至3%，则此时制备的Ta₂O₅薄膜呈多孔状，均匀分布，孔径30-50nm，孔道相互交错，深度150-200nm，薄膜与基底接触紧密而牢固，适合用于进一步改性，就表面积而言，远优于板结片状Ta₂O₅薄膜。煅烧处理后，Ta₂O₅薄膜由无定型转化为正交斜方晶系，在短波紫外光区的吸收性能显著提高。（3）采用电化学聚合法对玻碳电极进行了聚孔雀绿（PMG）修饰。研究表明，PMG与玻碳电极之间接触良好，电化学反应过程主要受电子传递动力学控制。溶液中磷酸盐与钼酸铵反应生成电活性物质磷钼酸，在PMG修饰电极表面的电化学反应主要受扩散控制，这是采用伏安法检测磷酸盐的理论基础。PMG修饰后，大大拓展了伏安法检测磷酸盐的线性范围，其中差分脉冲伏安法（DPV）检测线性范围为0.05-10.0mg·L-1，超过标准光度法10倍以上。另外，与未修饰的玻碳电极相比，磷酸盐的检测限显著降低，达到国家标准光度法水平（0.01mg·L-1）。PMG修饰电极伏安法（尤其是DPV法）在检测低浓度磷酸盐方面与标准方法相当，但在检测范围方面远远优于光度法，这主要是源于导电聚合膜PMG在电荷传递、离子传输和催化能力等方面的优良特性。（4）以BDD为电极，研究高电位下硫酸肼的电化学行为，同时采用伏安法对其进行检测。结果表明，硫酸肼在BDD电极上可以被直接氧化，反应过程受扩散控制，整个氧化过程中转移电子数为4。电化学阻抗研究表明，BDD电极氧化硫酸肼的电荷传递电阻显著小于析氧反应。加入硫酸肼后电荷传递电阻由200kΩ降低至300Ω，降低约3个数量级。DPV法检测硫酸肼的测量信号分别在低浓度区段（0.002-0.1mM）和高浓度区段（0.1-4.0mM）与相应硫酸肼浓度呈现良好的线性关系，但不同区段灵敏度不同。在低浓度区段BDD电极对硫酸肼响应更灵敏，每mmol可产生55.75μA的响应值，而高浓度区段响应值降低为33.50μA。当硫酸肼浓度超过4.0mM后，响应值偏离线性。另外，平行实验结果表明该方法重复性较好。更多还原

【Abstract】 The pesticide wastewater is more difficult to remove from wastewater due to its hugeamount, complex components, and high toxicity. In view of energy shortage, the investigationof an efficient, low energy consumped pesticide wastewater treatment technology issignificantly important. In recent years, photocatalytic technology has been studied widely inthe field of organic wastewater treatment. However, owing to its low quantum efficiency andphotocatalytic activity, this technology has not been applied in practice. Therefore, we havedeveloped an approach to enhanced the photocatalytic efficiency of TiO₂nanotube membraneby depositing noble metal on the surface of the TiO₂nanotube membrane. Besides, we haveinvestigated the fabrication of nano-porous Ta₂O₅films which can be used as a precursor forpreparation of nitrogen oxide tantalum.It is well known that the degradation products or intermediates are also important asmuch as the parent compound of pesticide due to their high toxicity or high risk. For example,phosphate is one of the products when organic phosphorus pesticides degrade. Phosphate willbe harmful if the content in water reaches a certain level. Hydrazine is another hazardouschemical that can be used as a raw material for the herbicide or fungicide production. Atpresent, there are some methods to detect phosphate and hydrazine such as spectrophotometryand luminescence measurement. Although these methods are normally accurate, they arevulnerable to water color, turbidity, and other factors. Electrochemical analysis possessesmany advantages including simple operation, sensitive test, fast speed, and so on. However, inthe previous works, there were still some problems in practic application, such as bad stability,short service life, harsh testing conditions and complex processes for preparing electrodes.Therefore, the other purpose of this work is to explore a more sensitive and stable electrode inorder to determine hydrazine and phosphate in aqueous solution. The main content is asfollows:（1） We have prepared a TiO₂nanotube film by anodic oxidation, and then modified itwith Au-Pd bimetal. The effect of the bimetal deposition on photocatalytic activity wasinvestigated using malathion, an organic phosphorus pesticide, as a probe. The experimentalresults suggest that the morphology of TiO₂nanotube film modified with Au-Pd （gold richalloy） by the photoreduction method is similar with that of original TiO₂nanotube film. Thephotocatalytic experiments indicate that the catalytic activity of the Au-Pd modified TiO₂nanotube membrane （Au-Pd-TiO₂） is significantly higher than that of the naked TiO₂nanotube, and the reaction rate increases by1.72times. The energy consumption per order isreduced remarkably. The improvement of catalytic activity is mainly attributed to the deposition of Au-Pd alloy. On one hand, the photogenerated electrons can be rapidlytransferred to the Au-Pd, thereby inhibiting the photogenerated charge carriers recombination;on the other hand, the electrons on Au-Pd can be trapped readily because molecular oxygencan form superoxide radical anions （O₂） and hydrogen peroxide （H₂O₂）. Thus, the life ofphotogenerated hole is prolonged, which is of great benefit to the oxidation reaction. Thereduction reaction can also be improved due to the fact that the yield of H₂O₂increased by1.89times after depositing Au-Pd bimetal.（2） We have also prepared nano-porous Ta₂O₅films by anodic oxidation inorganic-inorganic hybrid electrolytes. The influences of preparation conditions on the filmgrowth were investigated using SEM, XRD, etc. The results demonstrate that water/phosphatecontent and fluorine ion content are two essential parameters in anodic oxidation processes.Ta₂O₅film exhibites a dense, lamellar morphology at a higher water or phosphate content.When the water content is decreased, i.e.10%water with the rest of ethylene glycol as theelectrolyte solution （3%ammonium fluoride）, nano-porous Ta₂O₅films appeare uniformly.The pores interlace each other with an average diameter of30-50nm and a depth of150-200nm. The film is contacted with the substrate closely and firmly. Undoubtedly, owing its highsurface area, the nano-porous Ta₂O₅film will be far superior to a dense, lamellar film. Aftercalcination, amorphous Ta₂O₅can be crystallized orthorhombic crystal system. The absorptionin the short wave ultraviolet light region is improved greatly.（3） Poly-malachite green （PMG） was electrochemically polymerized on a glassy carbonelectrode. The results indicate that PMG is well contacted with the glassy carbon electrode,and the reaction between them is controlled by electron transfer kinetics. On the surface ofPMG modified electrode, the redox of phosphomolybdic acid, a electroactive substanceformed by phosphate and ammonium molybdate, is mainly controlled by mass transfer, whichis the theoretical basis of the voltammetric detection of phosphate. The linear range for thevoltammetric detection of phosphate is greatly expanded due to PMG modification. The linearrange of the method for differential pulse voltammetry （DPV） is0.05-10.0mg·L-1, which ismore than10times wider than that for the standard photometric method. In addition,compared with that of the bare glassy carbon electrode, the detection limit of PMG modifiedelectrode is lower and reach the national standard photometric level （0.01mg·L-1）. Thevoltammetric detection of phosphate （especially DPV） using PMG modified electrode canprovide a lower detection limit and a wider linear range, which is mainly derived fromexcellent characteristics of the conductive polymerized film PMG, such as charge transfer, iontransport, and catalytic ability.（4） The electrochemical behavior of hydrazine sulfate was investigated on a boron dopeddiamond （BDD） electrode under a high potential. At the same time, the voltammetricdetection of hydrazine sulfate was also carried out. The results demonstrate that hydrazine sulfate can be directly oxidized on the BDD electrode. The reation is controlled by the masstransfer process. The number of electrons involved in the reation is four. Electrochemicalimpedance studies indicate that the charge transfer resistance of hydrazine oxidation issubstantially smaller than that of oxygen evolution. The charge transfer resistance can bedecreased from200kΩ to300Ω （about3orders） by adding hydrazine sulfate into solutionsunder the same conditions. The linear range for DPV detection of hydrazine sulfate is dividedto two sections,0.002-0.1mM and0.1-4.0mM, while the sensitivity in different segments isnot same. The BDD electrode is more sensitive to hydrazine when its concentration is lowerthan0.1mM. One mmol of hydrazine could produce55.75μA signal current. The currentdecreases to33.50μA in the range of0.1-4.0mM. The reponse value deviates from the linearwhen hydrazine sulfate concentration exceed4mM. In addition, the parallel experimentresults confirme that this method could be well repeated.更多还原