【作者】 王宝娟；

【导师】 姚秉华；

【作者基本信息】 西安理工大学 ， 应用化学， 2008， 硕士

【摘要】 农药废水因毒性大、浓度高和组分复杂，成为废水治理难题之一。半导体TiO₂是一种高效的光催化剂，具有很强的氧化能力，在紫外光辐射下，它能将空气中和水中的有机污染物降解为CO₂和H₂O，无二次污染，已引起研究者的极大关注。但普通粉体TiO₂催化剂存在电荷分离效率差、光催化活性低、不易回收等缺点，致使它的工业应用受到限制。光电催化技术是一种通过施加外加电压，将光激发半导体产生的光生电子迁移到对电极上，减少光生电子-空穴的复合，从而提高光催化活性的新技术。它集光电技术于一体，在降解有机污染物等环境污染治理方面已显示出广泛的应用前景。本文应用光电催化技术，主要围绕TiO₂光催化薄膜电极的制备和改性展开研究，以高效氯氰菊酯（BEC）和辛硫磷为目标降解物，评价所制薄膜电极的光电催化活性，揭示光电催化降解规律，具体研究工作如下：1．薄膜电极的制备研究以泡沫镍为载体，采用溶胶-凝胶法分别研究了TiO₂及Ce⁴⁺/TiO₂薄膜电极的制备方法。以钛酸丁酯[Ti（OC₄H₉）₄]为前驱体，无水乙醇为溶剂，乙酰丙酮为络合剂，聚乙二醇[（PEG）400]为致孔剂，以冰醋酸为抑制剂，制得TiO₂溶胶；通过浸渍提拉技术在泡沫镍基体上制备了所需的TiO₂膜层；将镀好的电极置于马福炉中，500℃下保温2h，随炉冷却至室温即制得TiO₂薄膜电极。制备Ce⁴⁺/TiO₂薄膜电极，只需向上述TiO₂溶胶中添加一定量的硫酸高铈Ce（SO₄）₂·4H₂O，制备出掺杂不同摩尔浓度n(Ce⁴⁺)/n（TiO₂）的薄膜电极，记作：n％Ce⁴⁺/TiO₂薄膜电极。2．TiO₂薄膜电极光电催化性能研究利用自行设计的光电催化反应装置，使用三电极体系（以光催化薄膜电极为工作电极（WE），饱和甘汞电极（SCE）为参比电极（RE），铂电极为对电极（CE）），125W高压汞灯为光源，使用CHI600b电化学工作站较为系统地研究了TiO₂薄膜电极的光电催化性能，探讨了影响光电催化反应的各种因素，确定最佳降解条件，并对光电催化过程进行动力学分析。（1）选择BEC为实验对象，研究了TiO₂薄膜电极的光电催化活性。结果表明，当煅烧温度为500℃、镀膜层数为5层、BEC初始浓度为45mg·L^-1，初始pH 6．08、NaCl浓度为0．01mol·L^-1、外加电压为0．6V（vs．SCE）时，反应120min，BEC的降解率可达80．3％，COD去除率达71．6％。降解过程服从Langmuir-Hinshehwood动力学模型，在较低质量浓度(≤90mg·L^-1)下，光电催化降解过程为一级反应，并求得Langmuir速率常数k₀=2．166 mg·（L·min）^-1，吸附常数K=2．214×10^-2L·mg^-1。（2）选择辛硫磷为实验对象，通过考察COD的变化，研究了TiO₂薄膜电极的光电催化性能。结果表明，当煅烧温度为500℃、镀膜层数为5层、辛硫磷初始浓度为70mg．L^-1、初始pH6．25、NaCl浓度为0．01mol·L^-1、光源为125W高压汞灯、外加电压为0．6V（vs．SCE）时，降解120min，辛硫磷溶液的COD去除率达63．6％。3．Ce⁴⁺/TiO₂薄膜电极光电催化性能研究选择BEC为实验对象，使用三电极体系（以光催化薄膜电极为工作电极，饱和甘汞电极为参比电极，铂电极为对电极），分别用125W高压汞灯及25W日光灯作为辐射光源，对Ce⁴⁺/TiO₂薄膜电极光电催化性能进行较为系统的对比研究。结果表明，当Ce⁴⁺掺杂量0．5％（摩尔分数）、镀膜层数为5层、煅烧温度450℃、BEC初始浓度为45mg·L^-1、初始pH6．01、NaCl浓度为0．01mol·L^-1、光源为125W高压汞灯、外加电压为0．1V（vs．SCE）时，120min BEC降解率达到92．1％；保持其他条件不变，光源改为25W日光灯，选用TiO₂薄膜电极为工作电极时，120min BEC降解率只有3％，而用0．5％Ce⁴⁺/TiO₂薄膜电极时，120min BEC降解率可以达到73％。更多还原

【Abstract】 Due to high toxicity, high concentration and complicated composition of wastewater from manufacturing agrochemicals, its treatment and purification have become one of the biggest challenges.As a semiconductor oxides, TiO₂ is a photocatalyst that shows high photoefficiency and oxidation activity. TiO₂ has become a hot research area because it can decompose organic pollutants into CO₂ and H₂O in gases and liquids. The TiO₂ photo-oxidation process, however, has not been widely applied due to, for instance, low electron transfer rate to oxygen and high recombination rate of electron-hole pairs and, thus, low photo-oxidation rate of organic compounds on the catalyst surface.Photoelectrocatalysis is a method that applied the bias potential to take away the photoelectrons and decrease the combination of electronholes. So the method can increase the photoeeffciency evidently. Rare earth doped on the photocatalytic activities of TiO₂ was investigated. As the model pollutant of Beta-cypermethrin（BEC） and phomix to evaluate the photoelectrocatalysis activity of thin-film electrodes, the experimental results were as follows:1. Preparation of thin-film electrodesTiO₂ and Ce⁴⁺/TiO₂ thin-film electrodes were successfully prepared on foam nickel substrates by sol-gel technique. TiO₂ sols were prepared with Ti（OC₄H₉）₄ as precusor, alcohol as solvent, acetylacetone as complexation, polyethylene glycol（PEG400） as pore-forming agent, glacial acetic acid as inhibiting agent. The needed TiO₂ films on substrate of nickel foam were prepared via a sol-gel dip-coating method. TiO₂ thin-film electrode was obtained by annealing the deposited coatings for 2h at 500℃. It was found that TiO₂ films were stabile. Meanwhile, it was also showed that photoproduction current of Ce⁴⁺/TiO₂ films electrode increased obviously by single sweep voltammetry measurements.2. Photoelectrocatalytic activities of TiO₂ filmsA new photoelectrocatalytic reactor was designed,in which 125W mercury lamp was used as light source,and CHI600b used as power. A three-electrode system was used, in which photoelectrochemical thin-film electrode was used as working electrode（WE）, Pt electrode as counting electrode（CE） and a saturated calomel electrode（SCE） as the reference electrode（RE）. The photoelectrocatalysis activities of TiO₂ films were evaluated by the photoelectrodegradation of BEC and phomix, and the effects of various conditions on the photoelectrocatalytic characteristics were investigated. The experimental results were as follows:（1）BEC was choosed as the target. The experimental results showed that when heat-treated temperature was 500℃, the film layers was 5, concentration of BEC was 45mg·L^-1,initial pH was 6.08, concentration of NaCl concentration was 0.01mol·L^-1, potential was 0.6V（vs. SCE）, degradation rate and COD removal were 80.3% and 71.6% in 120min, respectively. The results showed that the degradation reaction of the BEC almost followed Langmuir-Hinshehwood model, and the photoelectrocatalysis reaction is a first-order reaction at lower concentration (（?）90mg·L^-1). The reaction rate constant k₀ and the absorption constant K were determined to be 2.166 mg·（L·min）^-1 and 2.214×10^-2 L·mg^-1, respectively.（2）Phomix was choosed as the target. Photoelectrocatalytic activities of TiO₂ electrode was evalued by COD removal efficiency.It’s found that when heat-treated temperature was 500℃, concentration of phomix was 70mg·L^-1,the film layers was 5, initial pH was 6.25, concentration of NaCl was 0.0lmol·L^-1, potential was +0.6V（vs. SCE）, COD removal was 63.6% in 120min.3. Photoelectrocatalytic activities of Ce⁴⁺/TiO₂ filmsBEC was chosen as the research object.A three-electrode system was used,in which the photoelectroncatalytic thin-film electrode was used as working electrode, Pt electrode as counting electrode and a saturated calomel electrode as the reference electrode. Photoelectrocatalytic activities were evalued by 125W mercury lamp and 25W fluorescent lamp as light source, respectively.The results showed that when doping amount of Ce⁴⁺ was 0.5%（molar fraction）, heat-treated temperature was 450℃, the film layers was 5, concentration of BEC and NaCl were 45mg·L^-1 and 0.01mol·L^-1 respectively,initial pH was 6.01, 125W mercury lamp as light source, potential was +0.1V（vs. SCE）, degradation rate of BEC was 92.1% in 120 min.Compareing to 25W fluorescent lamp as light source with the same other conditions, the degradation rate of BEC by using TiO₂ films was 3% in 120min. When Ce⁴⁺/TiO₂ films was used, however,the rate was even reached 73% in 120min.更多还原