氧化锌基复合光催化剂的制备及光降解四环素废水应用研究

发布时间：2018-04-22 19:05

本文选题：光催化技术 + ZnO　；参考：《江苏大学》2017年硕士论文

【摘要】：光催化技术不仅是一种具有易于操作和可完全降解有机物分子等优点的高级氧化法,也是一项利用光能来降解有机污染物的绿色环保技术。在众多催化剂中,ZnO是一种宽禁带(约为3.37 eV)直接带隙n型半导体材料,因其具有来源丰富、价格低廉、化学稳定性好、热稳定性高和无毒等优点,使得其在光催化剂的研究中备受关注。但是,ZnO的带隙较宽,使得其对太阳能的利用效率较低,光生载流子的复合率高,量子效率低,大大限制了ZnO的应用。基于ZnO光催化剂在应用过程中存在的这些问题,本论文中我们采用了一系列改性方法合成了氧化锌基光催化剂。利用半导体间电子转移过程原理构建异质结型复合光催化剂,采用具有合适的导带和价带位置的CeO_2来与ZnO耦合,以埃洛石纳米管(HNTs)为载体,通过湿法煅烧制得ZnO/CeO_2@HNTs异质结光催化剂;利用碳量子点(CQDs)独特的光学特性设计量子点敏化型复合光催化剂,以埃洛石纳米管为载体,制备CQDs/ZnO@HNTs复合光催化剂;利用贵金属的等离子体共振效应,通过其电荷传输和能量传递来提高光利用率和降低光生载流子的复合率,构筑具有等离子体效应的碳参杂氧化锌壳-银核结构的Ag@ZnO/C复合光催化剂;利用温敏聚合物独特的温度响应性亲疏水功能设计出ZnO/C表面接枝聚(N-异丙基丙烯酰胺)(PNIPAM)温敏响应聚合物,获得温敏型智能识别选择性降解功能的复合光催化材料。具体内容如下:以埃洛石纳米管为载体,通过湿法煅烧制备了星云状ZnO/CeO_2@HNTs异质结纳米复合光催化剂。采用透射电镜(TEM)、高倍透射电镜(HRTEM)、X射线衍射仪(XRD)、红外光谱仪(FT-IR)、紫外-可见光漫反射仪(UV-vis DRS)、X射线光电子能谱仪(XPS)、电化学测试等表征手段对材料进行表征。在模拟太阳光的照射下,通过降解四环素水溶液来测试样品的光催化活性。从表征结果中可以得到:湿法煅烧过程中,水分子为氧化物的形成提供了充足的氧源,在水分的快速蒸发过程中,促使星云状的ZnO/CeO_2纳米簇的形成。当Zn:Ce摩尔比为3:1,煅烧温度为500℃,氧化物:载体的质量比为1:1时,制备出的光催化剂对四环素呈现出了最好的光降解率,60 min内其光降解率可达到87%。以柠檬酸和乙二胺为原料,利用微波法制备出碳量子点(CQDs)溶液。以氯化锌、氢氧化锂为原料,以HNTs为载体,以乙醇为溶剂,通过超声-沉淀法制得ZnO@HNTs纳米复合前躯体。通过二次水热制备CQDs/ZnO@HNTs量子点敏化复合光催化剂。通过TEM、XRD、FT-IR、UV-vis DRS、XPS、电化学测试等表征手段对材料进行表征,通过在可见光下降解四环素来考察所得催化剂的活性。实验结果表明:CQDs成功修饰于分散性良好的ZnO@HNTs前躯体表面,并且增强了可见光下的催化活性。采用葡萄糖为碳源,以醋酸锌、硝酸银、氢氧化锂为原料,以乙二醇为溶剂,经过一步还原制得Ag纳米粒子,通过溶剂热法形成ZnO纳米粒子包裹Ag核结构,制得Ag@ZnO/C等离子体效应核壳型复合光催化剂。通过扫描电镜(SEM)、X射线能谱仪(EDS)、TEM、XRD、FT-IR、UV-vis DRS、XPS、电化学测试等对所制备材料进行表征,并通过降解四环素来考察催化剂的性能。结合表征结果可以得到:当ZnO:Ag摩尔比为5:1,葡萄糖用量为0.4 g时,样品降解效果最好,降解率可达到82.2%。此外,结合电子自旋共振图谱分析(ESR),基于ZnO壳-Ag核结构和等离子体共振效应,提出了可能的反应机理。以N-异丙基丙烯酰胺(NIPAM)为温敏功能单体,N’N-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸铵(APS)为引发剂,通过3-(异丁烯酰氧)丙基三甲氧基硅烷(MPS)对ZnO/C前躯体进行表面修饰并接枝温敏聚合物,合成了PNIPAM@ZnO/C温敏响应功能化光催化剂。用SEM、EDS、XRD、FT-IR、UV-vis DRS等测试手段对复合光催化剂进行表征,并通过光催化降解四环素溶液来考察其催化活性。结果显示,在高温下(45℃),催化剂活性受到抑制;在低温下(20℃),催化剂表现出良好的催化活性。PNIPAM修饰的ZnO/C复合智能光催化剂具有良好的温度响应性能和光催化降解活性,达到了温度调节控制降解活性的功能化要求。
[Abstract]:Photocatalytic technology is not only a kind of advanced oxidation method, which has the advantages of easy to operate and completely degrade organic molecules, but also a green technology to degrade organic pollutants by using light energy. In many catalysts, ZnO is a kind of wide band gap (about 3.37 eV) direct band gap n semiconductor material, because of its rich source and price. Low lattice, good chemical stability, high thermal stability and non-toxic and so on, it has attracted much attention in the study of photocatalyst. However, ZnO has a wide band gap, which makes the utilization of solar energy low, the recombination rate of light carrier is high, and the quantum efficiency is low. The application of the ZnO photocatalyst in the application process is based on the large limit of the application of the photocatalyst in the application process. In this paper, we used a series of modified methods to synthesize the Zinc Oxide based photocatalyst, using the principle of electron transfer between semiconductors to construct a heterojunction composite photocatalyst, coupled with ZnO with a suitable guide band and valence band position CeO_2, and using the HNTs as the carrier and wet calcined by wet method. The ZnO/CeO_2@HNTs heterojunction photocatalyst was prepared, and a quantum dot sensitized composite photocatalyst was designed by using the unique optical properties of carbon quantum dots (CQDs). The CQDs/ZnO@HNTs composite photocatalyst was prepared by using the yallot nanotube as the carrier, and the use of the plasma resonance effect of precious metals was used to improve the optical utilization by its charge transfer and energy transfer. The Ag@ZnO/C composite photocatalyst of a carbon mixed Zinc Oxide shell and silver nucleus with plasma effect was constructed by rate and reduction of the recombination rate of the photogenerated carrier, and a thermosensitive intellect was obtained by using the unique temperature responsive hydrophobicity of the thermosensitive polymers to graft poly (N- isopropyl acryl amine) (PNIPAM) Wen Min response polymer on the surface of ZnO/C. The composite photocatalyst can be used to identify the selective degradation function. The contents are as follows: the nano composite photocatalyst of nebulous ZnO/CeO_2@HNTs heterojunction was prepared by wet calcination with the hydrometallurgy of the eno nanotube. Using transmission electron microscope (TEM), high transmission electron microscope (HRTEM), X ray diffractometer (XRD), infrared spectrometer (FT-IR), UV visible The material is characterized by UV-vis DRS, X ray photoelectron spectroscopy (XPS) and electrochemical measurement. The photocatalytic activity of the sample is tested by the degradation of the tetracycline water solution under the irradiated sunlight. The water molecules can be obtained from the characterization results as the formation of the oxide in the process of wet calcination. A sufficient oxygen source promotes the formation of a nebula like ZnO/CeO_2 nanocluster in the process of rapid evaporation of water. When the Zn:Ce molar ratio is 3:1, the calcining temperature is 500, and the mass ratio of the carrier is 1:1, the prepared photocatalyst presents the best light degradation rate to tetracycline, and the photodegradation rate can reach 87%. with citric acid within 60 min. Carbon quantum dots (CQDs) solution was prepared by microwave method with ethylenediamine as raw material. Using zinc chloride and lithium hydroxide as raw material, HNTs as the carrier and ethanol as solvent, the ZnO@HNTs nanocomposite precursor was obtained by ultrasonic precipitation method. The CQDs/ZnO@HNTs quantum dot sensitized composite photocatalyst was prepared by two times of water heat. Through TEM, XRD, FT-IR, UV-vis D RS, XPS, electrochemical testing and other characterization methods were used to characterize the material, and the activity of the catalyst was investigated by degradation of tetracycline under visible light. The results showed that CQDs was successfully modified on the well dispersed ZnO@HNTs precursor surface and enhanced the catalytic activity under visible light. The Ag nanoparticles were prepared by one step reduction by one step reduction of lithium hydroxide as the raw material. ZnO nanoparticles were formed by solvent thermal method to wrap the Ag nuclear structure. The Ag@ZnO/C plasma effect nuclear shell composite photocatalyst was prepared. By scanning electron microscope (SEM), X ray energy spectrometer (EDS), TEM, XRD, FT-IR, UV-vis DRS, electrochemical testing and so on, The prepared materials were characterized, and the performance of the catalyst was investigated by degradation of tetracycline. When the ZnO:Ag molar ratio was 5:1 and the amount of glucose was 0.4 g, the degradation efficiency was best, the degradation rate could reach 82.2%., combined with the electron spin resonance spectrum analysis (ESR), based on the ZnO shell -Ag nuclear structure and plasma. The possible reaction mechanism was proposed, with N- isopropyl acrylamide (NIPAM) as thermosensitive monomer, N 'N- methylene diacrylamide (MBA) as crosslinking agent, ammonium persulfate (APS) as initiator, and 3- (isobutylyl) propyl trimethoxy silane (MPS) on the surface modification of the ZnO/C precursor and grafting of temperature sensitive polymers. PNIPAM@ZnO/C thermosensitive functionalized photocatalyst was used to characterize the composite photocatalyst with SEM, EDS, XRD, FT-IR, UV-vis DRS and so on. The catalytic activity of the catalyst was investigated by photocatalytic degradation of tetracycline solution. The results showed that the activity of the catalyst was inhibited at high temperature (45 C), and the catalyst was good at low temperature (20 degrees C). A good catalytic active.PNIPAM modified ZnO/C composite photocatalyst has good temperature response and photocatalytic degradation activity, which has achieved the functional requirements of temperature regulation to control degradation activity.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;O643.36

【参考文献】