半導體材料的固定化及其對雨水消毒性能的研究
發(fā)布時間：2018-09-02 06:23
【摘要】：有效利用雨水資源可緩解人類社會日益嚴重的水危機,然而傳統(tǒng)的雨水處理技術如生物過濾等盡管可有效去除懸浮物、有機物和重金屬等污染物,但并不能完全殺滅糞便微生物如大腸桿菌(E.coli)。光催化是一種經(jīng)濟高效、環(huán)境友好的水質消毒技術,與液氯消毒、臭氧消毒和電化學消毒等相比,在雨水消毒方面有特殊的優(yōu)勢。光催化水質消毒技術中,TiO_2是目前應用最廣的光催化材料,但在實際使用過程中分離與回收TiO_2納米顆粒并不容易,往往需要高速離心或者膜過濾等高能耗的工藝。另外,光照停止后,TiO_2等常規(guī)光催化材料不會再繼續(xù)產(chǎn)生電子和空穴,而其在光照過程中產(chǎn)生的活性氧如雙氧水(H2O_2)、羥基自由毖(·OH)和過氧自由基(·O_2-)等壽命很短,光照停止后會迅速消失,所以光照停止之后TiO_2等便不再具有殺菌的能力。因此,發(fā)展經(jīng)濟、安全的光催化雨水消毒技術,除需解決納米光催化材料的分離問題,還需研發(fā)可在光照停止后持續(xù)殺滅微生物的新材料。本研究在第2章采用超聲處理法將TiO_2納米顆粒固定于氧化石墨烯(GO)納米片上,制備了可在水中高效分離的TiO_2-GO復合物,并研究了該復合物在水中的分離性能以及在太陽光下殺滅雨水中E.col的能力和殺菌機理；在第3、4、5章利用可在光照下儲存電子的鈦酸鹽納米片(Titanium oxide nanosheets,TONs)鎢酸鹽納米點(Tungsten oxide nanodots, TODs),通過層層自組裝法制備了具有暗活性的光催化薄膜,研究了它們在光照停止后殺滅雨水中E.coli的能力和殺菌機理,以期為發(fā)展經(jīng)濟、高效且具有持續(xù)殺菌能力的光催化雨水消毒技術提供技術支持和理論依據(jù)。研究結果表明：(1)TiO_2-GO復合物在水中具有良好的沉降性能,可通過自由沉降從水中快速分禺。TiO_2-GO(1.0 g/L)混合液在超純水中經(jīng)5h靜置沉降,濁度可從5200 NTU降至30NTU以下,在模擬雨水中經(jīng)8 h靜置沉降可降至50 NTU以下,TiO_2-GO可快速沉降的主要原因是TiO_2與GO在靜電引力作用下形成了粒徑較大的顆粒物；(2) TiO_2-GO復合物在太陽光下具有良好的光催化性能,90 min內可殺滅雨水中100%的E.coli,而且TiO_2-GO具有良好的穩(wěn)定性,循環(huán)使用過程中沉降性能和殺菌能力并未明顯降低；(3)鎢酸鹽(Na_2WO_4)和二氧化鈦(TiO_2)可通過質子化、逐層剝離的方法轉化為二維納米材料TODs和TONs,它們可在光照下儲存電子并在光照停止后將其緩慢釋放；釋放的電子可與O_2反應生成H2O_2和·O_2-并殺滅水中的E.coli；電化學分析表明W6+/W5+和Ti4+/Ti3+的還原與氧化是TODs和TONs儲存電子的主要原因；(4)TODs和TONs表面電荷為負,可通過層層自組裝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能夠儲存電子,經(jīng)紫外光預處理的TODs和TONS薄膜具有一定的暗活性,可在光照停止后殺滅水中的E.coli,經(jīng)過6 h的暗反應可分別殺滅雨水中約38%和40%的E.coli；(5)由于能帶結構不同,將TONs與TODs復合可提高TODs儲存電子的能力。同樣條件下,TONs-TODs復合膜在60 min內儲存的電子量(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)單獨儲存的電子量的總和,因此具有更強的暗活性,可在同樣條件下殺滅更多的E.coli。TiO_2-GO復合物制備簡單,在雨水中可高效分離且具有良好、穩(wěn)定的殺菌能力,可有效解決TiO_2納米顆粒分離困難的問題；TODs、TONs光催化薄膜制備簡單且能夠產(chǎn)生一定的暗活性,光照停止后仍可殺滅E.coli。本研究的結果可為發(fā)展經(jīng)濟、高效且具有持續(xù)殺菌能力的光催化雨水消毒技術提供技術支持和理論依據(jù)。
[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.
【學位授予單位】：中國地質大學(北京)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TU992;TV213.9
本文編號：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.
【學位授予單位】：中國地質大學(北京)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TU992;TV213.9
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