摘要
工业废水排放带来的水体污染引起社会广泛关注，光催化技术开辟了水体中微量重金属离子处理的新途径，TiO2由于性质稳定、无毒无害、价格低廉成为最常用的光催化剂。但TiO2带隙较宽，仅限于吸收紫外光，成为困扰光催化技术应用到实际的难点。本论文立足实际，以工业化生产的纳米二氧化钛P25为光催化剂，辅以其他方法修饰或改性，通过一系列的表征方法，考察其形貌、晶型、光学性能、附加条件等因素对重金属离子降解的影响，结合光催化和自由基捕获实验探究光催化还原重金属离子的机理。具体研究内容如下：（1）利用甲酸钠原位修饰P25作光催化剂，在紫外光下处理游离态的Cd (Ⅱ)，并通过XRD、TEM、XPS、UV-vis、FT-IR等一系列手段进行表征。实验表明，紫外光照下，P25在60 min内无法将Cd(Ⅱ)光催化降解，经甲酸钠修饰后，P25在400~600 nm的可见光区域表现出较强吸光特性，并在30 min紫外光照下将Cd(Ⅱ)完全降解，甲酸钠的最佳浓度为1.0 g/L。研究表明甲酸钠与P25形成双齿螯合物将Cd(Ⅱ)吸附到催化剂表面，甲酸钠中羧基与光生空穴反应生成的强还原性物质将光生电子转移至重金属离子上，完成Cd(Ⅱ)降解。
永定客家土楼
（2）通过改变单一因素法考察P25在紫外光下降解Cr(Ⅵ)的影响条件。固定紫外光照时间为30 min，实验表明pH为4.0，Cr(Ⅵ)浓度为0.2 mg/L，P25的加入量为1.5 g/L时分别为各自条件的最佳，Cr(Ⅵ)的降解率最高分别为86.39%、77.18%、91.20%。
（3）采用真空活化光沉积法和乙醇还原法制备Ag-P25复合光催化剂并进行光催化性能的测试。在最佳条件下，可见光照射90 min，乙醇还原法制备的样品对Cr(Ⅵ)能够实现完全降解，光沉积法制备的样品由于Ag反应条件不易控制，容易发生团聚现象造成光催化性能下降。
蒜蓉蒸排骨的做法（4）对乙醇还原法制备的Ag-P25进行结构、形貌、结合能、吸光度等分析，研究表明Ag纳米颗粒成功负载到催化剂表面，并将催化剂拓宽到可见光吸收。对其光催化机理分析，Ag纳米粒子加快电子与空穴分离的效率，柠檬酸诱导空穴反应生成强还原性自由基CO2·-，将Cr(Ⅵ)光催化降解还原。
电脑win键是哪个（5）光电催化实验表明，电催化与光催化在还原降解重金属离子方面有协同作用。对于乙醇还原法制备的3.0-Ag-P25，pH为3.0，电流为0.01 A为最佳，在此条件下，观察到20 min内Cr(Ⅵ)的降解率为88.57%。30 min内，Cr(Ⅵ)在任一电流条件会基本完全降解。实验表明光电协同作用提高了光催化剂的反应速率，大幅缩短重金属离子降解时间，为重金属离子降解提供一种可行性方法。
关键词：氧化钛(P25)；重金属离子；Ag-P25；光催化
Abstract手机掉电快
Water pollution caud by industrial wastewater discharge has been widespread concerned by the whole society. Photocatalytic technology has opened up a new approach to the treatment of poisono
us heavy metal ions in water. TiO2 is the most ud photocatalyst due to its stable nature, non-toxicity, harmlessness, and low price. However, becau of the wide bandgap, TiO2 is that it only absorbs a small portion of solar spectrum in the ultraviolet (UV) region, which limits its effective applications. In this work, the photocatalytic degradation ability of nano titanium dioxide (P25) as a photocatalyst to heavy metals industrially produced was studied. A ries of characterizations were ud to analy its morphology, crystal form and optical properties. The mechanism of photocatalytic reduction of heavy metal ions was explored through photocatalytic performance and free radical capture experiments. The specific rearch content are as follows:
1. As a photocatalyst, P25 that surface in situ modified with sodium formate was ud to degrade free Cd (II) under ultraviolet light, and characterized by XRD, TEM, XPS, UV-vis, FT-IR. The experimental results show that the pure P25 cannot photocatalytically degrade Cd (II) in 60 minutes under UV light. While modified with sodium formate, P25 had a strong absorption at wavelength of 400-600 nm, and showed the high catalytic activity. When the optimal concentration of sodium formate was 1.0 g/L, Cd (II) was completely degraded in 30 minutes. Theoretical analysis showed that Cd (II) was adsorbed on the catalyst surface by the bidentate chelate structure formed between P25 and sodium formate. The strong reducing substance that formed in the reaction of carboxyl grou
ps of sodium formate with photogenerated holes, and photogenerated electrons transfered to heavy metal ions, achieving reduction of heavy metal ions.
俯视人物2. Fixed irradiation of UV light for 30 min, the effect of P25 degradation of Cr (VI) under UV light was investigated by changing the single factor method. The
results showed that the optimal conditions of every factors were pH value 4.0, the concentration of Cr (VI) 0.2 mg/L, and the amount of P25 1.5 g/L, respectively. The supreme degradation rate for Cr (VI) reached 91.20% under the optimal conditions.
3. The Ag-P25 composite photocatalyst was prepared by vacuum activated photodeposition method and ethanol reduction method,respectively. The as-prepard samples were tested for photocatalytic performance. Under the optimal conditions, the samples prepared by the ethanol reduction method could completely degrade Cr (VI) after 90 min under visible light irradiation. However, for the sample prepared by the photodeposition method, it was difficult to control the formation of Ag, which leads to the agglomeration of the Ag particles, resulting in a decrea in photocatalytic performance.
4. The Ag-P25 prepared by the ethanol reduction method were characterized through a variety of properties such as the structure, morphology, binding energy, and absorbance. The results showed t
hat Ag nanoparticles were successfully loaded on the catalyst surface, and the absorption of catalyst was broadened to visible light region. The possible mechanism involved that the Ag nanoparticles accelerated the efficiency of electron and hole paration, and citric acid reacted with holes to produce a strong reducing free radical CO2·-, which degraded Cr (VI).
5. The photoelectrocatalysis experiments approveded that electrocatalysis and photocatalysis had synergistic effects in reducing heavy metal ions. For 3.0-Ag-P25 prepared by the ethanol reduction method, the pH 3.0 and the current intensity 0.01 A were the optimum values. Under the optimal conditions, the degradation rate of Cr (VI) was 88.57% within 20 minutes. After 30 minutes, Cr (VI) were completely degraded under any current conditions. The results above mentioned showed that the photoelectric synergy improved the reaction rate of the photocatalyst, greatly shortened the degradation time of heavy metal ions. This provided a feasible method for the degradation of heavy metal ions.
Keywords: TiO2 (P25), heavy metal ions, Ag-P25, photocatalysis中国十大银行排名
目录
第一章绪论 ...................................................................................................... - 1 -
1.1 重金属离子的现状 ..................................................................................... - 1 -
1.1.1 重金属离子对人体的危害 ................................................................... - 1 -
1.1.2 重金属离子去除的研究现状 ............................................................... - 2 - 1.2 半导体光催化技术 ..................................................................................... - 3 -
1.2.1 光催化反应的机理 ............................................................................... - 3 -
1.2.2 光催化去除重金属离子 ....................................................................... - 4 - 1.3 二氧化钛光催化剂 ..................................................................................... - 4 -
1.3.1 二氧化钛光催化剂的改性研究 ........................................................... - 6 -
1.3.2 二氧化钛在重金属离子处理上的发展 ............................................... - 6 - 1.4 论文研究内容 ............................................................................................. - 8 -
第二章甲酸钠原位修饰P25降解镉的性能与机理研究 ............................... - 10 -
2.1 前言 ........................................................................................................... - 10 - 2.2 实验部分 ................................................................................................... - 10 -
2.2.1 实验试剂与仪器设备 ......................................................................... - 10 -
2.2.2 光催化剂的表征 ................................................................................. - 11 -
2.2.3 光催化实验 ......................................................................................... - 12 - 2.3 结果与分析 ............................................................................................... - 13 -
2.3.1 XRD分析............................................................................................ - 13 -
玉龙雪山一日游2.3.2 形貌分析 ............................................................................................. - 14 -
大国制造2.3.3 FT-IR分析........................................................................................... - 16 -
2.3.4 UV-vis分析......................................................................................... - 17 -
2.3.5 XPS分析............................................................................................. - 18 -
2.3.6 光催化性能分析 ................................................................................. - 20 -
2.3.7 光催化机理分析 ................................................................................. - 21 - 2.4 本章小结 ................................................................................................... - 26 -
第三章重金属离子Cr(Ⅵ)的光催化降解及性能研究.................................... - 28 - 3.1 前言 ........................................................................................................... - 28 -
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