TRƯỜNG ĐẠI HỌC BÁCH KHOA HÀ NỘI LUẬN VĂN THẠC SĨ Xúc tác quang hóa TiO2 pha tạp vanadi ứng dụng xử lý nước thải NGUYỄN ĐỨC MẠNH Manh.vn Ngành Hóa học Giảng viên hướng dẫn: 1. Nghiêm Thị Thương Viện Kỹ thuật Hóa học, ĐHBKHN Chữ ký của GVHD 2. Esteban Mejia Viện LIKAT, ĐH Rostock Chữ ký của GVHD HÀ NỘI, 10/2022 HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Visible light-driven photocatalysts based on V-doped TiO2 for wastewater treatment NGUYEN DUC MANH Manh.vn Master of Science in Chemistry Supervior: 1. Nghiem Thi Thuong School of Chemical Engineering, HUST Signature 2.
Esteban Mejia Leibniz Institute for Catalysis, UR Signature Hanoi, 10/2022 ĐỀ TÀI LUẬN VĂN Tên đề tài: Xúc tác quang hóa TiO2 pha tạp vanađi ứng dụng xử lý nước thải Giảng viên hướng dẫn chính Giảng viên hướng dẫn phụ PGS. Nghiêm Thị Thương TS. Esteban Mejia Acknowledgments First of all, I would like to express my deepest gratitude towards Dr. Esteban Mejia, Department of Biocatalysis & Polymer Chemistry, Leibniz Institute for Catalysis, for giving me the great opportunity to work in his group and for his guidance as well as his outstanding support during my master’s research.
I would like to thank Dr. Nguyen Van Anh, School of Chemical Engineering, Hanoi University of Science and Technology, for giving me the concept of my thesis and her helpful guidance. I am also thankful to Assoc. Nghiem Thi Thuong, School of Chemical Engineering, Hanoi University of Science and Technology, for her all advice and her much support throughout the master’s program.
I am also indebted to M. Paul Hünemörder, M. Gustavo Alvarez and M. Shuoping Ding at Leibniz Institute for Catalysis, who supported my research with a great deal of valuable discussions.
Special thanks go to my Vietnamese friends, namely Hung, Thuyen, Tuan, M. Phong Dam, as well as the Vietnamese pioneers, namely Dr. Huyen Vuong, Dr. Hieu Do, Dr.
Vien Che, for their understanding and for giving me the warm atmosphere in Rostock. I would like to thank the RoHan project for giving me the excellent opportunity to visit Germany for studying with fully financial support. Last but not least, I am wholeheartedly grateful to my family, especially my parents, my sister, my uncle and his wife for their unconditional love, their encouragement and never-ending support. Abstract Trichloroethylene (TCE) is a volatile chlorinated organic compound (VCOC) commonly used as a solvent in automotive, metal, finishing, and textile industries.
Wastewaters contaminated with TCE are a pollutant of serious concern in groundwaters, as it is harmful to aquatic and surface ecosystems and to the human health. There are various reported methods for the degradation of TCE in aqueous media, including the “air stripping method”, where the volatilization is often incomplete, and consequently a residual amount of TCE can still be found in the treated water. Moreover, gas-phase degradation of TCE produces toxic by-products such as phosgene and dichloroacetyl chloride. Photocatalytic degradation of VCOCs in the aqueous phase using semiconductors such as TiO2 is well known and offers a promising alternative owing to its cost- effectiveness and nontoxicity.
However, pure TiO2 can only absorb UV light, which accounts for 2 5% of the solar spectrum, thus restricting its practical application. Furthermore, the rapid recombination of photogenerated electron-hole pairs kinetically impedes many desired routes to complete pollutant mineralization. In this regard, vanadium ions doping has been considerably investigated to improve the optical properties of TiO2 as well as to promote separation of electron-hole pairs. In this work, vanadium-doped TiO2 photocatalysts were prepared via a simple one- step hydrothermal method for photocatalytic degradation of TCE at a high concentration in aqueous phase.
Different characterization methods were employed to reveal the role of vanadium in the enhancement of visible light absorption as well as charge separation, which lead to an improved photoactivity of catalysts. In addition, the study also provides evidence for the formation of V2O5 on the surface of TiO2 when doping at high vanadium concentrations and its influence on the photodegradation of TCE under visible light was also discussed. Master student NGUYEN DUC MANH Table of Contents LIST OF FIGURES. i LIST OF TABLES.
iv LIST OF ABBREVIATION. Chemical identity and Properties. Applications and Disposal. Environmental effects and Human’s health risks.
Nanostructured Titanium Dioxide. Structural and Crystallographic properties. Photocatalysts based on TiO2 materials in wastewater treatment. MATERIALS AND METHODS.
Photocatalytic activity experiments. Recycling experiments for catalysts. RESULTS AND DISCUSSION. FT-IR and Raman spectra.
ICP-OES analysis. SEM – EDX data. BET surface area and pore distribution. 58 LIST OF FIGURES Figure I.
Families collecting water from water well in Africa (left) and the industrial wastewater disposal in Asia (right) (Source: UNICEF, 2020). Proportion of population using safely managed drinking water services, 2017 (%) [1]. Applications of Trichloroethylene (all images were taken without permission from public internet sites. The rights belong to the corresponding sources).
Illustration of air-stripping technology (Source: Federal Remediation Technologies Roundtable) [12]. Unit cell of TiO2 phases: (a) Anatase, (b) Rutile, and (c) Brookite; blue and red spheres represent titanium and oxygen atoms, respectively [21]. Crystallite structure of TiO2 phases: (a) Anatase, (b) Rutile, and (c) Brookite [22]. the XRD patterns and the ball-and-stick structures of (a) anatase, (b) rutile, and (c) brookite [28].
The ideal structure of TiO2(B) [34]. Comparison of recombination pathways of electron-hole pairs within the direct band-gap semiconductor and the indirect band-gap semiconductors [41]. Photo-induced reactions in the TiO2 photocatalysis versus the corresponding time [42]. Effect of the initial pH on the TiO2 morphology [44].
Different possible growth mechanisms for the formation of TiO2 nanostuctures [28]. The proposed condensation pathway for the nucleation of TiO2 crystals [47]. Photocatalytic activities of different shape-controlled TiO2 nanomaterials for MO degradation and SEM images of TiO2 nanomaterials [50]. Mechanism of photocatalytic reactions of V-doped TiO2 under UV-Vis irradiation.
The PL spectra and catalytic activity of V-modified TiO2 samples calcined at 300 oC from [54]. UV-Vis DRS of V-N co-doped TiO2 samples and photodegradation of PCP- Na under visible light irradiation with prepared catalysts from [53]. XRD pattern of V2O5/TiO2 at different V/Ti molar ratio (right) and SEM images of V2O5/TiO2 nanofibers from [56]. Schematic illustration of the one-step hydrothermal process to prepare V- doped TiO2 photocatalysts.
Schematic illustration of photocatalytic activity experiments. XRD patterns of as prepared TiO2 samples and the inset shows anatase (101) peak in detail. Structural properties of as prepared TiO2 samples: Phase content (a), Average crystallite size (b), and Unit cell volume (c). FT-IR spectra of as prepared TiO2 samples measured at room temperature.
Raman spectra of as prepared TiO2 samples with the expanded regions. EDX data of V-doped TiO2 samples. EDX mapping of Ti, O, V elements of 0. Nitrogen adsorption/desorption isotherms and the corresponding pore size distribution plot (the inset) of Undoped TiO2 and 0.
High-resolution XPS spectra of the Ti 2p, V 2p, O 1s, and the C 1s regions of Undoped TiO2 and 0. STEM images and expanded regions (a1-a4; b1-b4) of 0.10V-TiO2; (a5) and (b5) are the images of inverse fast Fourier transform of (a4) and (b4), respectively; (a6) and (b6) is the plot profile of IFFT of the selected regions in (a5) and (b5) respectively, obtained by the ImageJ software. UV-VIS DRS spectra (left) and the Tauc plot (right) of as prepared TiO2 samples. Photoluminescence spectra of as prepared TiO2 samples upon 355 nm excitation.
The photocatalytic degradation of Trichloroethylene over the as-prepared TiO2 samples under the UV irradiation (left) and the visible irradiation (right) at room temperature. 46 ii Figure III. Recycling experiments over 0.10V-TiO2 (Light: 390 nm, 40W; irradiation time: 3h; Catalyst dose: 2 g L-1, CTCE = 1000 ppm, mCat : mTCE = 2 : 1) (left); and XRD pattern of fresh 0.10V-TiO2 and after 4 cycles. 1H-NMR spectra (300 MHz, D2O) of TCE degradation over 0.10V-TiO2 photocatalyst under the UV light at 0h and 3h.
Proposed mechanism of photodegradation of TCE over Vanadium-doped TiO2 photocatalyst. 51 iii LIST OF TABLES Table I. Chemical identity of Trichloroethylene. Physicochemical properties of Trichloroethylene a.
The crystallite properties of TiO2 [23]. Total V/Ti molar ratio of the TiO2 samples measured by ICP-OES. Textural properties of Undoped TiO2 and 0. Comparison of TCE removal efficiency with various photocatalysts.
48 iv LIST OF ABBREVIATION Abbreviation Meaning Atm Atmosphere BET equation Brunauer – Emmett – Teller equation BJH model Barrett – Joyner – Halenda model CB Conduction Band DCAAD 2,2-dichloroacetaldehyde DRS Diffuse Reflectance Spectra EDX Energy Dispersive X-ray EPA Environmental Protection Agency FT-IR Fourier Transform Infrared ICP-OES Inductively Coupled Plasma – Optical Emission Spectroscopy IFFT Inverse Fast Fourier Transform IS Internal Standard JCPDS Joint Committee on Powder Diffraction Standards NMR Nuclear Magnetic Resonance PL Photoluminescence SEM Scanning Electron Microscopy STEM Scanning Transmission Electron Microscopy TCE Trichloroethylene Temp. Temperature UV light Ultraviolet light VB Valance Band VCOC Volatile Chlorinated Organic Compound Vis light Visible light WHO World Health Organization XPS X-ray Photoelectron Spectra XRD X-ray Powder Diffraction [Cat.] Catalyst dose [TCE] Concentration of Trichloroethylene v CHAPTER I. Water Crisis “There is a water crisis today. But the crisis is not about having too little water to satisfy our needs.
It is a crisis of managing water so badly that billions of people, and the environment suffer badly” – World Water Vision Report. Families collecting water from water well in Africa (left) and the industrial wastewater disposal in Asia (right) (Source: UNICEF, 2020) According to a 2019 WHO’s press release, more than 2 billion people in the world lack access to fresh water that is free from health risks. In fact, nearly 40% of global population of 117 countries can only access to safely managed water services. In the other regions, collecting data is difficult generally, with a focus on Africa, Cental and Southern Asia, and Latin America, primarily in least developed and developing coutries.
There is no doubt that in these countries, the water source is typically of poor quality. It could be understandable because of high priority on economic development as well as the rapid industrialization and civilization, whereas there are a lack of the water treatment infrastructure in these countries. Proportion of population using safely managed drinking water services, 2017 (%) [1] 1 There was a time when people belived water was an infinite resource. Around fifty years ago, there were fewer than half as many people on the planet as today.
They required a third of the volume of water we presently obtain from surface sources. Nevertheless, the Earth’s population is forecast to reach 9 billions by 2050 [2]. More water will be needed for various human’s purposes, consequently the consumption of water resources will be much more intense. Thus, water scarcity will occur unless the timely actions in water conservation and recycling of water resource are conducted.
Fresh water availability is one of the critical issues facing our world. In an estimation, one-third of water need of the world is obtained from surface sources such as rivers, lakes, dams, and canals [3]. However, these sources of water have being been contaminated by the domesic and industrial or agricultural wastewater from human’s activities of economic development. Especially, many communities in regions of developing or poor countries still rely on untreated or improperly treated water from these surface resources for their daily supply.
The pollution of water sources with pathogenic organisms, organic or inorganic compounds could result in serious health risks for people who use it for purposes downstream [4-5]. Nowadays, many countries and organizations have taken steps to enhance water quality worldwide as well as to provide access to safe water for human all and preserve the Earth’s water ecosystems, while scientists around the world are also studying and developing on sustainable means to treat contaminated waters effectively [6-7].