VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGHIEM XUAN DUC FABRICATION AND APPLICATION OF MgFe2O4/WO3/rGO NANOCOMPOSITE AS AN ADVANCED PHOTOCATALYST FOR ANTIBIOTIC DEGRADATION IN AQUEOUS SOLUTIONS MASTER'S THESIS VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGHIEM XUAN DUC FABRICATION AND APPLICATION OF MgFe2O4/WO3/rGO NANOCOMPOSITE AS AN ADVANCED PHOTOCATALYST FOR ANTIBIOTIC DEGRADATION IN AQUEOUS SOLUTIONS MAJOR: ENVIRONMENTAL ENGINEERING CODE: 8520320.01 RESEARCH SUPERVISORS: Associate Prof. TRAN DINH TRINH Dr. NGUYEN THI AN HANG Hanoi, 2022 COMMITMENT I have read and understood the plagiarism violations. I pledge with personal honor that this research result is my own and does not violate the Regulation on prevention of plagiarism in academic and scientific research activities at VNU Vietnam Japan University (Issued together with Decision No 700/QD-ĐHVN dated 30/9/2021 by the Rector of Vietnam Japan University).
Author of the thesis ACKNOWLEDGEMENTS This research would not have been possible without the guidance, support, and patience of a number of individuals with whom I have had the honor of engaging and learning over the years. Before anything else, I would like to express my profound appreciation to Associate Professor Tran Dinh Trinh and Doctor Nguyen Thi An Hang for their enthusiastic instruction and supervision throughout this research. Secondly, I would like to take this opportunity to thank all of the professors, lecturers, and students in the Master’s Program in Environmental Engineering at VNU Vietnam Japan University for their assistance and encouragement during this work, which has been fully appreciated. Lastly, I would like to thank my closest friends Thao, Huong, Dai and Hoang Anh for their support and encouragement throughout this lengthy journey.
TABLE OF CONTENTS List of tables. i List of figures. ii List of abbreviations. Ciprofloxacin pollution in aquatic environment.
Introduction of Ciprofloxacin (CIP). Occurrence of CIP in aquatic environment. Negative impacts of CIP on aquatic medium. Methods for treatment of CIP in aquatic medium.
Advanced Oxidation Processes (AOP) by photocatalyst. Introduction of MgFe2O4 nanoparticle. Introduction of WO3 nanoparticle. Introduction of reduced graphene oxide (rGO).
Overview of Z-scheme photocatalytic system. MgFe2O4/WO3/rGO nanoparticle as a direct Z-scheme photocatalytic system 28 2. Conclusion of literature review. Materials and methods.
Chemicals and Apparatus. Synthesis of MgFe2O4. Synthesis of WO3. Synthesis of GO.
Synthesis of MgFe2O4/WO3/rGO nanocomposite. Material characterization method. Fourier-transform infrared spectroscopy. Scanning electron microscope.
Energy-dispersive X-ray spectroscopy. UV–Vis Diffuse Reflectance Spectroscopy. pH point of zero charge. Study of photocatalytic removal of Ciprofloxacin by MgFe 2O4-WO3-rGO nanocomposite.
Determination of Ciprofloxacin concentration. Determine efficiency of Ciprofloxacin removal .3 Comparative study of CIP removal by MgFe 2O4, WO3 and MgFe2O4/WO3/rGO. Factors influencing the CIP removal efficiency. Stability and recyclability of MgFe 2O4/WO3/rGO nanocomposite.
Results and discussion. Fourier-transform infrared spectroscopy. Scanning electron microscope. Energy-dispersive X-ray spectroscopy.
UV–Vis Diffuse Reflectance Spectroscopy. pH point of zero charge. Study of photocatalytic removal of Ciprofloxacin by MgFe 2O4-WO3-rGO nanocomposite. Comparative study on the removal of CIP by MgFe 2O4, WO3 and MgFe2O4/WO3/rGO.
Factors influencing the CIP removal efficiency. Kinetic study of CIP photodegradation. Radical scavengers and proposed mechanism of CIP photodegradation process. Stability and recyclability of MgFe 2O4/WO3/rGO nanocomposite.
Conclusion and recommendations. 74 LIST OF TABLES Table 2. Antibiotics and their respective highest concentration in Vietnam. Methods for removal of CIP from aqueous solutions.
The positions of cations, formula and example of normal, inverse and mixed spinel ferrites. Chemical synthesis methods of spinel ferrites. Different method for synthesis of GO. Different methods for synthesis of rGO.
Comparison of three generations of Z-scheme photocatalytic system. Elemental composition of MgFe2O4/WO3/rGO nanocomposite. Eg of MgFe2O4, WO3 and MgFe2O4/WO3/rGO. The comparison of CIP photodegradation between MgFe 2O4/WO3/rGO nanocomposite and other photocatalysts.
64 i LIST OF FIGURES Figure 2. Structure of CIP. Species of CIP at different pH values. The amount of antibiotics imported into Vietnam.
Sources of CIP in aquatic medium. Schematic diagram of AOP. Diagram of spinel ferrite demonstrating tetrahedral (yellow), octahedral (green) and oxygen atoms (red) units. Crystallite structure of WO3 at different temperature.
Chemical structure of GO. Historical progression of Z-scheme photocatalytic system. Mechanism of a direct Z-scheme photocatalytic system. Operation of XRD method.
XRD MiniFlex 600, Rigaku Corp. FT-IR 4600, Jasco Corp. Schematic diagram of a FT-IR instrument. SEM TM 4000 Plus, Hitachi Corp.
Fundamental principle of EDX instrument. EDX MisF+, Oxford Instruments plc. UV-Vis DRS UH 5300, Hitachi Corp. Calibration curve of CIP.
Schematic diagram of CIP degradation by photocatalyst. XRD spectra of MgFe2O4, WO3, rGO and MgFe2O4/WO3/rGO. FT-IR spectra of MgFe2O4, WO3, rGO and MgFe2O4/WO3/rGO. SEM image of MgFe2O4.
SEM image of WO3. SEM image of MgFe2O4/WO3/rGO. EDX spectrum of MgFe2O4/WO3/rGO. Electron mapping of a) Mg, b) C, c) Fe, d) O, and e) W elements in the MgFe2O4/WO3/rGO nanocomposite.
UV-Vis DRS absorption spectra of MgFe2O4, WO3 and MgFe2O4/WO3/rGO. Tauc plot of MgFe2O4, WO3 and MgFe2O4/WO3/rGO. Photoluminescene spectra of MgFe 2O4/WO3/rGO nanocomposite and pristine MgFe2O4 nanoparticle. pHpzc of MgFe2O4/WO3/rGO nanocomposite.
Comparison of CIP removal between MgFe2O4, WO3, and MgFe2O4/WO3/rGO. Comparison of CIP removal by MgFe2O4/WO3/rGO nanocomposite at various pH values. CIP species at different pH value. Comparison of CIP removal at various dosage of MgFe 2O4/WO3/rGO nanocomposite.
Comparison of CIP removal at various initial CIP concentration by MgFe2O4/WO3/rGO nanocomposite. Pseudo-zero-order kinetic model for CIP-photodegradation by MgFe2O4/WO3/rGO nanocomposite. Pseudo-first-order kinetic model for CIP-photodegradation by MgFe2O4/WO3/rGO nanocomposite. Pseudo-second-order kinetic model for CIP-photodegradation by MgFe2O4/WO3/rGO nanocomposite.
Comparison between CIP removal with or without t-BuOH by MgFe2O4/WO3/rGO nanocomposite. Proposed mechanism for CIP photodegradation by MgFe2O4/WO3/rGO nanocomposite. MgFe2O4/WO3/rGO (a) before and (b) after extracted by magnet. Stability and recyclability of MgFe2O4/WO3/rGO nanocomposite after three cycles.
70 iii LIST OF ABBREVIATIONS AOP: Advanced Oxidation Processes BSE: Backscattered electron CB: Conduction band CIP: Ciprofloxacin COD: Chemical Oxygen Demand EDX: Energy-dispersive X-ray Eg: Band gap energy FT-IR: Fourier-transform infrared spectroscopy GO: Graphene oxide KLAMG: VNU Key Laboratory for Advanced Materials for Green Growth MARD: Ministry of Agriculture and Rural Development NHE: Normal hydrogen electrode pHpzc: pH point of zero charge PL: Photoluminescence RE: Removal efficiency rGO: Reduced graphene oxide ROS: Reactive Oxygen Species SE: Secondary electron SEM: Scanning electron microscope SHE: Standard hydrogen electrode UV-Vis UV–Vis Diffuse Reflectance Spectroscopy DRS: VB: Valance band WWTPs: Wastewater treatment plants XRD: X-ray Diffraction iv 1. Research significance Using antibiotics is an effective treatment for infectious diseases in both humans and animals. There are numerous applications of antibiotics, such as preventive medicine, and growth promoters in agriculture and animal husbandry (Binh et al. Thanks to the use of antibiotics, mortality and morbidity rates caused by common infectious diseases have been decreased significantly.
However, the widespread production and use of antibiotics has resulted in the fact that antibiotics have become ubiquitous in the environment (Kümmerer, 2009b). Antibiotics have been detected in aquatic medium, including lakes, rivers, water reservoirs, wastewater, groundwater, and even treated drinking water. Moreover, even at low antibiotic concentrations, antibiotic resistance has a remarkable potential to occur in the environment (Kümmerer, 2009a; Yu et al. Therefore, antibiotics are considered as significant emerging environmental pollutants (Hu et al.
In recent years, water pollution due to the increase in consumption and improper disposal of antibiotics has emerged as a major concern (Yu et al. Ciprofloxacin (CIP), which is widely used in the therapy of mild-to-moderate urinary and respiratory tract infections, can cause various negative impacts on the public health and aquatic life if they are present in water resources. To be more specific, the presence of CIP in drinking water can cause nervousness, nausea, and vomiting. Additionally, its presence in water resources can result in the development of antibiotic resistant bacteria (Ahmadzadeh et al., 2017; Mandal et al.
Hence, the degradation of residues of CIP in water resources is crucial. Unfortunately, most antibiotics cannot be removed completely by traditional technologies such as activated sludge and trickling filter due to their poor biodegradability (Yu et al., 2019) Advanced oxidation processes (AOP) by photocatalysts, which are based on the generation of reactive oxygen species with high redox potential, such as hydroxyl radical (HO•), superoxide radical (O2-•), have been received enormous attention due to their 1 ability to break down recalcitrant organic compounds into CO 2 and H2O (Chen et al., 2017; Guo et al., 2021; Mahdi et al. However, one of the most important challenges in the use of photocatalysts is the difficulty in separation and recovery of the catalyst after use. Fortunately, in recent years, the use of spinel ferrites (AB 2O4) can favor the recovery of the spent photocatalysts because of magnetic forces (Mahdikhah et al.
Of which, magnesium ferrite nanoparticle (MgFe 2O4 NP), which is one outstanding example of spinel ferrites, has received high interest due to 1) narrow band- gap (2.0 eV), 2) magnetic recovery property, and 3) no toxic metal in the molecules (Garcia-Muñoz et al., 2020; Yao et al. Moreover, in this research, to enhance the photocatalytic performance of the individual MgFe2O4, WO3 and reduced graphene oxide (rGO), which are gaining tremendous interest from researchers (Bai et al., 2021; Chaudhary et al., 2020; Mao et al., 2021; Vu et al., 2022), their combination is implemented to fabricate MgFe2O4/WO3/rGO nanocomposite. Research novelty So far, there have been several studies on nanocomposites for CIP treatment. Nevertheless, these nanocomposites either use UV irradiation or lack of the ability to be recovered by magnetic forces (Chen et al., 2019; Costa et al., 2021; Malakootian et al., 2019; Tamaddon et al.
Hence, the present research aims at filling the above research gaps by developing a lab-scale advanced photocatalytic system for effective CIP degradation from aqueous solutions, which is characterized by (1) simultaneous formation of both effective reactive oxygen species (HO• and O2-•), (2) reduction in recombination rate of photogenerated holes (h+) and electrons (e-) during AOP, (3) effective performance in visible light region, and (4) possible separation after use by external magnetic forces. Research objectives This research involves four main objectives, including: • Synthesis of MgFe2O4/WO3/rGO nanocomposite. • Characterization of synthesized MgFe 2O4/WO3/rGO nanocomposite. 2 • Investigation of factors (e., pH, catalyst dosage and initial CIP concentration) influencing the CIP removal by the MgFe 2O4/WO3/rGO nanocomposite as well as the CIP removal efficiency at the optimal condition.
• Study of photodegradation kinetics and mechanism by radical scavengers. • Investigation of stability and regeneration of MgFe2O4/WO3/rGO nanocomposite. Thesis structure This thesis is composed of 5 chapters. The main contents of these chapters are presented below: Chapter 1 introduces the research context and significance.
The novelty, objectives, and scope of the research are highlighted. The first chapter closes with the thesis outline. Chapter 2 provides information on the sources, occurrence, negative impacts on the aquatic environment, and existing treatment methods of CIP. Especially, AOP by photocatalysts in general and nanocomposites in particular are focused with their merits and demerits as well as possible pathways to overcome the bottlenecks.
Chapter 3 demonstrates the materials, instruments and procedures utilized in this investigation. The details of experiments are presented, including chemical preparation, experimental setup, analytical methodologies, and experimental instruments. Chapter 4 presents the main research results, including characteristics of the synthesized MgFe2O4/WO3/rGO nanocomposite, influential factors, treatment performance of CIP, photodegradation mechanism and kinetics. Chapter 5 summarizes the major research findings.
Additionally, it ends with recommendations for future research directions. Ciprofloxacin pollution in aquatic environment 2. Introduction of Ciprofloxacin (CIP) Ciprofloxacin (1-cyclopropyl-6-fluoro-7-(1-piperazinyl)-1,4-dihydro-4-oxo-quinoline- 3-carboxylic acid), hereinafter referred to as CIP, is a member of fluorinated quinolones that are structurally similar to nalidixic acid. The structure of CIP is shown in Figure 2.
The CIP exhibits numerous advantageous characteristics, including high bioavailability, good tissue penetration, and a low incidence of undesirable and toxic effects. This antibiotic is used to treat urinary tract infections and prostatitis.