MINISTRY OF EDUCATION AND TRAINING QUY NHON UNIVERSITY TRUONG DUY HUONG SYNTHESIS OF MS2 (M = Mo, W) AND THEIR MODIFICATION WITH g-C3N4 AS PHOTOCATALYSTS MAJOR: PHYSICAL AND THEORETICAL CHEMISTRY CODE No.: 9440119 DOCTORAL THESIS IN CHEMISTRY BINH DINH - 2021 MINISTRY OF EDUCATION AND TRAINING QUY NHON UNIVERSITY TRUONG DUY HUONG SYNTHESIS OF MS2 (M = Mo, W) AND THEIR MODIFICATION WITH g-C3N4 AS PHOTOCATALYSTS MAJOR: PHYSICAL AND THEORETICAL CHEMISTRY CODE NO. Nguyen Van Thang Reviewer 2: Assoc. Nguyen Duc Cuong Reviewer 3: Assoc. Tran Thi Van Thi Supervisor: Assoc.
VO VIEN – Quy Nhon University BINH DINH – 2021 DECLARATION This thesis has been completed at the Quy Nhon University, in cooperation with KU Leuven, under the supervisor of Assoc. I hereby assure that this research project is mine. All the results are honest, have been approved by co-authors and have not been released by anyone else before. Supervisor Author Assoc.
VO VIEN TRUONG DUY HUONG ACKNOWLEDGEMENTS Firstly, from my heart, I would like to express my gratitude to both of my promoters, Prof. Vo Vien and Prof. Enis Leblebici not only for your enthusiastic guidance, expertise and invaluable time, but also for your encouragement when I encountered difficulties during the time of doing the research. Furthermore, from the beginning to the very end of my study time in KU Leuven, Belgium, I could say that without the constant support from Prof.
Enis Leblebici my study would haven’t accomplished any progress as I have today. Meanwhile, the belief that I have ability to do the research from Prof. Vo Vien made me more energetic to overcome the tough time on my scientific pathway. Another professor who inspired me a lot and that also the one always is in my heart, Prof.
Tom Van Gerven. You always gave me a warm welcome and a lovely smile that made me feel more confident and relax when we had unforgetable group meetings together along with Prof. I am not exaggerated when say that the meeting time with both of you has been the most beautiful moments that I have experienced in my life. Even in the time of writing this acknowledgement, I still feel that happy time in my mind.
So, it is not easy to express that feeling in words, especially in English, I just try to say how kind of you are. Having the opportunity to study in Belgium, a heart of Europe how can I forget the financial support from TEAM project, VLIR-UOS. Without this project, without the effort from all the project maker members, including Prof. Do Ngoc My (Rector of QNU), Prof.
Nguyen Tien Trung, Prof. Vu Thi Ngan, Prof. Vo Vien, especially from Prof. Minh Tho Nguyen, my dream could not come true.
I also would like to thank my friends who stood with me in any circumstances. Those from Vietnam like Mis. Vu Thi Lien Huong, rector of Le Khiet High School for the Gifted, Mr. Le Van Trung chemistry group leader of the school and all lovely colleagues.
To Pham Hoang Quan, one of my closest friends who taught me some basic experimental skills from the beginning, the fact that you suddenly passed away made me could not believe, I promise to take care of your little daughter as much as I can within my ability, Mr. Tran Duc Trung for your help in heating my samples at Dung Quat Technology and Engineering and encouraging me in time when I had troubles, my students Quoc Nhat and Quang Tan for your effort to do the experiments in the school laboratory in the early days for the first Vsef that we achieved the best prize, the second group with Tuan Anh and Nguyen Khang, the third group with Vu Quan and Anh Kiet, Mr. Dinh Trong Nghia and Le Van Phuong for your time in coffee shops whenever I need someone to talk and those who I worked and met in KU Leuven such as Lief in the Admission Office, Alena in the Secretary Office, Christine for your instructions in the lab and characterizing my samples, Michelle for your ordering chemicals, Ruijun for some wonderful parties, watching a football match of OH Leuven and XPS analysis, Thomas and Glen for your support in the lab, Mohammed for your nice conversation, Joris in MTM for your acceptance and instruction of using inert atmosphere furnace, the CIT football team which gave me a chance to be a goalkeeper for the first season and a defender for the second, Tri who being with me all the time from Camelo Tores to Home Vesalius, the two nice family of Mr. Thanh Hai & Mis.
Mien Trung, Hung & Hang with a lot of support from the early days, Tan Hung (little Hung) for your unforgettable Martini wine party and Hung, Linh, Tuyet Anh, brother Giang for the last but beautiful visit. My lovely group, Mis. Lan, Thanh Tam, To Nu, Zoan An, Huu Ha, all of you are also still in my mind today and future. Last but not least, I would like to give all of my loving heart to my wife and two daughters Ha Khanh and Cao Nguyen, who always give me an unlimited energy source and the strongest motivation to overcome the difficulties during the time of studying.
To my beloved wife, you know, your sacrifice and hard working to take care our angels during the time I was away from home is the most valuable thing that I have ever had, that reminded me of the responsibility not only to our little family but also to myself to keep my spirit on track without giving up regardless the inevitable obstacles. To my father, you have always been beside me on my way in spite of the fact that you have let us alone on this planet for six years, I miss you so much. Mama, how can I show how much important you are to me when now you are become unique for my life, you don’t have direct contribution to my work, but the way you have overcome the big loss made me feel that you have been hiding your broken heart to help me to focus more on my work. I also would like to give my sincere gratitude to my mother- and father-in-law for your uncountable support in terms of finance and emotion.
My siblings Thuy, Tai, Mis. Tram and my brother-in-law Binh, all of you also in my mind for your sentimental value that you gave me. CONTENTS DECLARATION ACKNOWLEDGEMENTS CONTENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION. OVERVIEW OF CURRENT PHOTOCATALYSTS.
MS2-BASED (M = Mo, W) PHOTOCATALYSTS. Structures of MS2 (M = Mo, W). MS2-based composites. PHOTOCATALYTIC PROCESS, LIGHT SOURCES AND ASSESSMENT BENCHMARKS.
Photocatalytic degradation mechanism. Adsorption role in photocatalytic process. Light sources for photocatalysis – Light emitting diodes (LEDs) 17 1. Photocatalytic reactor assessment.
PHOTODEGRADATION OF ANTIBIOTICS AND DYES IN AQUEOUS SOLUTION. PHOTOCATALYTIC PILOT DESIGN OVERVIEW. Slurry reactors versus immobilized catalyst reactors. CHEMICALS AND EQUIPMENTS.
Fabrication of WS2/g-C3N4. Fabrication of MoS2/g-C3N4. Determining point of zero charge. Light spectra and intensity.
Photocatalytic activity evaluation. Measurement of emitted irradiance using spectrophotometer probe. High performance liquid chromatography (HPLC) and mass spectrometry (MS). Active species determination.
Pilot description and operating principles. Timing program for Arduino circuit. Sedimentation procedure and catalyst recovery percentage. Reaction rate constant and photochemical space-time yield (PSTY).
Flow rate for turbulent regime. Throughput for pilot plant. RESULTS AND DISCUSSION. X-ray diffraction patterns.
Scanning electron microscopy images. Transmission electron microscopy images. X-ray photoelectron spectroscopy spectra. UV-Vis diffuse reflectance spectra.
X-ray diffraction patterns. X-ray photoelectron spectroscopy. UV–vis diffuse reflectance spectroscopy. MATERIAL PHOTOCATALYTIC ACTIVITY.
Adsorption-desorption equilibrium time. Photocatalytic activity comparisons. Effect of catalyst loading. Adsorption and photocatalysis.
Point of zero charge and existed forms of dye molecules. Effect of pH solution, important role of adsorption step. A new benchmark for efficiency evaluation of reaction reactor – Photochemical space time yield. Calculate reaction rate constant under optimal condition.
PSTY calculations for the chosen reaction systems. Effect of oxidant concentration. Reactive species trapping experiments and proposed photocatalytic mechanism. Photodegradation of a selected antibiotic, enrofloxacin.
Designed-pilot evaluation. 100 LIST OF PUBLICATIONS. 103 APPENDIXES LIST OF ABBREVIATIONS AND SYMBOLS 1. Abbreviations AOPs : Advanced oxidation processes BET : Brunauer – Emmett – Teller BQ : p-Benzoquinone CB : Conduction band COD : Chemical oxygen demand CVD : Chemical vapour deposition DMSO : Dimethyl sulfoxide DRS : Diffuse reflectance spectroscopy EDX : Energy-dispersive X-ray spectroscopy FTIR : Fourier transform infrared IR : Infrared LC-MS : Liquid chromatography – Mass spectrometry LED : Light-emitting diode LP : Standardized lamp power MB : Methylene blue MCN : MoS2/g-C3N4 PL : Photoluminesence PSTY : Photochemical space-time yield pzc : Point of zero charge RhB : Rhodamine B SEM : Scanning electron microscopy STY : Space-time yield TBA : Tert-butyl alcohol TEM : Transmission electron microscopy TEOA : Triethanolamine TGA : Thermalgravimetric analysis UV : Ultraviolet WCN : WS2/g-C3N4 VB : Valence band XPS : X-ray photoelectron spectroscopy XRD : X-ray diffraction 2.
Symbols C : Concentration D : Inner diameter Eg : Bandgap h : Planck constant k : Rate constant m : Mass P : Power Q : Flow rate q : Adsorption capacity Re : Reynold number r : reaction rate S : Surface area t : Time V : Volume ρ : Density of flowing fluid π : Pi number μ : Dynamic viscosity ν : Frequency θ : Fraction of reactant absorbed LIST OF TABLES Table 2. Main features of the used chemicals. Equipments for pilot building. BET specific surface area and pore volume of the g-C3N4 and MCNx samples.
PSTY data for the chosen reaction systems. 83 LIST OF FIGURES Figure 1. MoS2 structure in three dimensions with the distance between the two adjacent layers of 6. Four common MoS2 poly-types [12].
Five-step flowchart of heterogeneous photocatalysis [17]. Molecular structure of enrofloxacin (left) and its UV-Vis spectrum (right). Methylene blue (a) and rhodamine B (b) structures and their corresponding UV-Vis spectra. Reaction system: (a) black box, (b) DC power supply and (c) thermostat bath.
Spectrum of light emitted from the incandescent lamp. Spectrum of the blue LED light. Calibration curves for quantitative determination of target molecules. Schematic representation of the pilot:discharging valve (1), charging valve with filter (2), control box (3), stirrer (4), pumping valve (5), flow sensor (6), delivery tube (7), blue LEDs (8), recharging tube (9), pump (10) and settling column (11).
XRD patterns of 5WCN, 7WCN, 10WCN, WS2, g-C3N4, and the reference for WS2 (Rf). SEM images of 5WCN (a), 7WCN (b), 10WCN (c), WS2 (d), and g-C3N4 (e). EDX elemental mapping of C (a), N (b), S (c) and W (d) elements for 10WCN. TEM images of 10WCN (a) and g-C3N4 (b).
IR spectra of 5WCN, 7WCN, 10WCN, WS2, and g-C3N4 in the wavenumber region of 400-4000 cm-1. IR spectra of 5WCN, 7WCN, 10WCN, WS2 in the wavenumber region of 400 – 600 cm-1. Raman spectrum of 10WCN. High-resolution XPS of C1s (a), N1s (b), S2p (c), W4d (d), W4f (e) and XPS of 10WCN (f).
TGA curves of samples 5WCN, 7WCN, 10WCN, WS2 and g-C3N4. UV-Vis diffuse reflectance spectra of 5WCN, 7WCN, 10WCN composites, WS2, and g-C3N4. XRD patterns of MoS2, g-C3N4, and MCNx (x = 1, 2, 3, 5). FTIR spectra of MoS2, g-C3N4 and MCNx (x = 1, 2, 3, 5) samples.
XPS spectra of Mo 3d (a), S 2p (b) and (c) XPS survey spectrum of MCN5 sample. N2 adsorption isotherms of MoS2, g-C3N4 and MCNx (x = 1, 2, 3, 5) samples. TGA curves of samples MoS2, g-C3N4, and MCNx (x = 1, 2, 3, 5) in Ar atmosphere.
