半导体材料的固定化及其对雨水消毒性能的研究
发布时间：2018-09-02 06:23
【摘要】：有效利用雨水资源可缓解人类社会日益严重的水危机,然而传统的雨水处理技术如生物过滤等尽管可有效去除悬浮物、有机物和重金属等污染物,但并不能完全杀灭粪便微生物如大肠杆菌(E.coli)。光催化是一种经济高效、环境友好的水质消毒技术,与液氯消毒、臭氧消毒和电化学消毒等相比,在雨水消毒方面有特殊的优势。光催化水质消毒技术中,TiO_2是目前应用最广的光催化材料,但在实际使用过程中分离与回收TiO_2纳米颗粒并不容易,往往需要高速离心或者膜过滤等高能耗的工艺。另外,光照停止后,TiO_2等常规光催化材料不会再继续产生电子和空穴,而其在光照过程中产生的活性氧如双氧水(H2O_2)、羟基自由毖(·OH)和过氧自由基(·O_2-)等寿命很短,光照停止后会迅速消失,所以光照停止之后TiO_2等便不再具有杀菌的能力。因此,发展经济、安全的光催化雨水消毒技术,除需解决纳米光催化材料的分离问题,还需研发可在光照停止后持续杀灭微生物的新材料。本研究在第2章采用超声处理法将TiO_2纳米颗粒固定于氧化石墨烯(GO)纳米片上,制备了可在水中高效分离的TiO_2-GO复合物,并研究了该复合物在水中的分离性能以及在太阳光下杀灭雨水中E.col的能力和杀菌机理；在第3、4、5章利用可在光照下储存电子的钛酸盐纳米片(Titanium oxide nanosheets,TONs)钨酸盐纳米点(Tungsten oxide nanodots, TODs),通过层层自组装法制备了具有暗活性的光催化薄膜,研究了它们在光照停止后杀灭雨水中E.coli的能力和杀菌机理,以期为发展经济、高效且具有持续杀菌能力的光催化雨水消毒技术提供技术支持和理论依据。研究结果表明：(1)TiO_2-GO复合物在水中具有良好的沉降性能,可通过自由沉降从水中快速分禺。TiO_2-GO(1.0 g/L)混合液在超纯水中经5h静置沉降,浊度可从5200 NTU降至30NTU以下,在模拟雨水中经8 h静置沉降可降至50 NTU以下,TiO_2-GO可快速沉降的主要原因是TiO_2与GO在静电引力作用下形成了粒径较大的颗粒物；(2) TiO_2-GO复合物在太阳光下具有良好的光催化性能,90 min内可杀灭雨水中100%的E.coli,而且TiO_2-GO具有良好的稳定性,循环使用过程中沉降性能和杀菌能力并未明显降低；(3)钨酸盐(Na_2WO_4)和二氧化钛(TiO_2)可通过质子化、逐层剥离的方法转化为二维纳米材料TODs和TONs,它们可在光照下储存电子并在光照停止后将其缓慢释放；释放的电子可与O_2反应生成H2O_2和·O_2-并杀灭水中的E.coli；电化学分析表明W6+/W5+和Ti4+/Ti3+的还原与氧化是TODs和TONs储存电子的主要原因；(4)TODs和TONs表面电荷为负,可通过层层自组装法固定于玻璃基底表面,形成透明的光催化薄膜,且由于TODs和TONS能够储存电子,经紫外光预处理的TODs和TONS薄膜具有一定的暗活性,可在光照停止后杀灭水中的E.coli,经过6 h的暗反应可分别杀灭雨水中约38%和40%的E.coli；(5)由于能带结构不同,将TONs与TODs复合可提高TODs储存电子的能力。同样条件下,TONs-TODs复合膜在60 min内储存的电子量(14.2±0.1×10~(-6)C/cm~2)大于TONs(7.8±0.3×10~(-6)C/cm~2)和TODs(2.7±0.1 × 10~(-6) C/cm~2)单独储存的电子量的总和,因此具有更强的暗活性,可在同样条件下杀灭更多的E.coli。TiO_2-GO复合物制备简单,在雨水中可高效分离且具有良好、稳定的杀菌能力,可有效解决TiO_2纳米颗粒分离困难的问题；TODs、TONs光催化薄膜制备简单且能够产生一定的暗活性,光照停止后仍可杀灭E.coli。本研究的结果可为发展经济、高效且具有持续杀菌能力的光催化雨水消毒技术提供技术支持和理论依据。
[Abstract]:Effective utilization of rainwater resources can alleviate the increasingly serious water crisis in human society. However, although traditional rainwater treatment technologies such as biofiltration can effectively remove suspended solids, organic matter and heavy metals, they can not completely kill fecal microorganisms such as E. coli. Photocatalysis is an economical, efficient and environmentally friendly water. Compared with liquid chlorine disinfection, ozone disinfection and electrochemical disinfection, the quality disinfection technology has special advantages in rainwater disinfection. Among the photocatalytic water disinfection technology, titanium dioxide is the most widely used photocatalytic material at present, but it is not easy to separate and recover titanium dioxide nanoparticles in the actual use process, often requires high-speed centrifugation or membrane filtration. In addition, conventional photocatalytic materials such as TiO_2 will not continue to produce electrons and holes after the light stops, and the active oxygen species such as hydrogen peroxide (H2O_2), hydroxyl free radicals (.OH) and peroxide free radicals (.O_2-) produced in the process of irradiation have very short lifetimes, which will disappear rapidly after the light stops, so the TiO_2 and so on after the light stops. Therefore, in order to develop economical and safe photocatalytic rainwater disinfection technology, it is necessary to solve the separation problem of nano-photocatalytic materials, and to develop new materials that can continuously kill microorganisms after the light stops. In chapter 2, the nano-particles of TiO_2 were immobilized on graphene oxide (GO) nanoparticles by ultrasonic treatment. Titanium oxide nanosheets (TONs) tungstate nanodots (Tuns) that can store electrons under light were used in chapter 3, 4 and 5. Photocatalytic thin films with dark activity were prepared by layer-by-layer self-assembly of gsten oxide nanodots (TODs). Their ability to kill E.coli in rainwater and its sterilization mechanism were studied after light stopping. The results will provide technical support and theoretical basis for developing economical, efficient and sustainable photocatalytic rainwater disinfection technology. The results show that: (1) the TiO_2-GO composite has good sedimentation property in water, and can be rapidly separated from water by free sedimentation. The turbidity of the mixture of TiO_2-GO (1.0 g/L) can be reduced from 5200 NTU to below 30NTU after 5 hours of static sedimentation in ultrapure water, and can be reduced to below 50 NTU after 8 hours of static sedimentation in simulated rainwater. The main reason is that the particle size of TiO_2 and GO is larger under the action of electrostatic attraction; (2) TiO_2-GO composite has good photocatalytic activity in sunlight, and can kill 100% of E.coli in rainwater within 90 minutes. Moreover, the stability of TiO_2-GO is good, and the sedimentation and sterilization ability are not significantly reduced in the recycling process; (2) the composite has good photocatalytic activity in sunlight and can kill 100% of E.coli in rain 3) Tungstate (Na_2WO_4) and titanium dioxide (TiO_2) can be transformed into two-dimensional nano-materials TODs and TONs by protonation and layer-by-layer peeling. They can store electrons under light and release them slowly after light stops. The released electrons can react with O_2 to form H2O_2 and O_2 - and kill E.coli in water. Electrochemical analysis shows that W6 +/O_2 can be used to remove E.coli in water. The reduction and oxidation of W5+ and Ti4 +/Ti3+ are the main reasons for TODs and TONs to store electrons; (4) The surface charges of TODs and TONs are negative, which can be fixed on the glass substrate by layer-by-layer self-assembly method to form transparent photocatalytic films. Because TODs and TONS can store electrons, the TODs and TONS films pretreated by ultraviolet light have a certain dark activity. It can kill E. coli in water after light stopping, and 38% and 40% of E. coli in rainwater can be killed by dark reaction after 6 hours. (5) Because of the different band structure, the ability of TODs to store electrons can be improved by compounding TONs with TODs. Under the same conditions, the electronic storage capacity of TONs-TODs composite film in 60 minutes (14.2 0.1 (-6) C/cm~2) is greater than that of TONs. (7.8 (-6) C/cm~2) and TODs (2.7 (-6) C/cm~2) stored separately have a higher dark activity and can kill more E.coli.TiO_2-GO under the same conditions. TODs and TONs photocatalytic thin films are easy to prepare and can produce certain dark activity, and can kill E. coli even after the light stops. The results of this study can provide technical support and theoretical basis for the development of economic, efficient and sustainable disinfection technology of photocatalytic rainwater disinfection.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU992;TV213.9
本文编号：2218524
[Abstract]:Effective utilization of rainwater resources can alleviate the increasingly serious water crisis in human society. However, although traditional rainwater treatment technologies such as biofiltration can effectively remove suspended solids, organic matter and heavy metals, they can not completely kill fecal microorganisms such as E. coli. Photocatalysis is an economical, efficient and environmentally friendly water. Compared with liquid chlorine disinfection, ozone disinfection and electrochemical disinfection, the quality disinfection technology has special advantages in rainwater disinfection. Among the photocatalytic water disinfection technology, titanium dioxide is the most widely used photocatalytic material at present, but it is not easy to separate and recover titanium dioxide nanoparticles in the actual use process, often requires high-speed centrifugation or membrane filtration. In addition, conventional photocatalytic materials such as TiO_2 will not continue to produce electrons and holes after the light stops, and the active oxygen species such as hydrogen peroxide (H2O_2), hydroxyl free radicals (.OH) and peroxide free radicals (.O_2-) produced in the process of irradiation have very short lifetimes, which will disappear rapidly after the light stops, so the TiO_2 and so on after the light stops. Therefore, in order to develop economical and safe photocatalytic rainwater disinfection technology, it is necessary to solve the separation problem of nano-photocatalytic materials, and to develop new materials that can continuously kill microorganisms after the light stops. In chapter 2, the nano-particles of TiO_2 were immobilized on graphene oxide (GO) nanoparticles by ultrasonic treatment. Titanium oxide nanosheets (TONs) tungstate nanodots (Tuns) that can store electrons under light were used in chapter 3, 4 and 5. Photocatalytic thin films with dark activity were prepared by layer-by-layer self-assembly of gsten oxide nanodots (TODs). Their ability to kill E.coli in rainwater and its sterilization mechanism were studied after light stopping. The results will provide technical support and theoretical basis for developing economical, efficient and sustainable photocatalytic rainwater disinfection technology. The results show that: (1) the TiO_2-GO composite has good sedimentation property in water, and can be rapidly separated from water by free sedimentation. The turbidity of the mixture of TiO_2-GO (1.0 g/L) can be reduced from 5200 NTU to below 30NTU after 5 hours of static sedimentation in ultrapure water, and can be reduced to below 50 NTU after 8 hours of static sedimentation in simulated rainwater. The main reason is that the particle size of TiO_2 and GO is larger under the action of electrostatic attraction; (2) TiO_2-GO composite has good photocatalytic activity in sunlight, and can kill 100% of E.coli in rainwater within 90 minutes. Moreover, the stability of TiO_2-GO is good, and the sedimentation and sterilization ability are not significantly reduced in the recycling process; (2) the composite has good photocatalytic activity in sunlight and can kill 100% of E.coli in rain 3) Tungstate (Na_2WO_4) and titanium dioxide (TiO_2) can be transformed into two-dimensional nano-materials TODs and TONs by protonation and layer-by-layer peeling. They can store electrons under light and release them slowly after light stops. The released electrons can react with O_2 to form H2O_2 and O_2 - and kill E.coli in water. Electrochemical analysis shows that W6 +/O_2 can be used to remove E.coli in water. The reduction and oxidation of W5+ and Ti4 +/Ti3+ are the main reasons for TODs and TONs to store electrons; (4) The surface charges of TODs and TONs are negative, which can be fixed on the glass substrate by layer-by-layer self-assembly method to form transparent photocatalytic films. Because TODs and TONS can store electrons, the TODs and TONS films pretreated by ultraviolet light have a certain dark activity. It can kill E. coli in water after light stopping, and 38% and 40% of E. coli in rainwater can be killed by dark reaction after 6 hours. (5) Because of the different band structure, the ability of TODs to store electrons can be improved by compounding TONs with TODs. Under the same conditions, the electronic storage capacity of TONs-TODs composite film in 60 minutes (14.2 0.1 (-6) C/cm~2) is greater than that of TONs. (7.8 (-6) C/cm~2) and TODs (2.7 (-6) C/cm~2) stored separately have a higher dark activity and can kill more E.coli.TiO_2-GO under the same conditions. TODs and TONs photocatalytic thin films are easy to prepare and can produce certain dark activity, and can kill E. coli even after the light stops. The results of this study can provide technical support and theoretical basis for the development of economic, efficient and sustainable disinfection technology of photocatalytic rainwater disinfection.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU992;TV213.9
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