The objectives of the thesis: The thesis focused on the synthesis of Mn, Ce, C doped ZnO nanoparticles materials and doped ZnO with multi-layered carbon nanotube nanocomposite materials and assessed their photo-oxidative potentiality through photocatalytic reactions of methylene blue (MB) decomposition in aqueous solution under visible light.
MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY - LUU THI VIET HA SYNTHESIS AND CHARACTERIZATION OF NANOMATERIALS Mn, Ce AND C DOPED ZnO AND EVALUATION OF THEIR PHOTO-OXIDATION POTENTIAL Major: Inorganic chemistry Code: 9.44.01.13 SUMMARY OF CHEMISTRY DOCTORAL THESIS Hanoi - 2018 This thesis was completed at: Graduate University Science and Technology - Vietnam Academy of Science and Technology Adviser 1: Assoc Prof Dr Luu Minh Đai Adviser 2: Assoc Prof Dr Dao Ngoc Nhiem 1st Reviewer: 2nd Reviewer: 3rd Reviewer: The thesis will be defended at Graduate University of Science and Technology - Vietnam Academy of Science and Technology, at hour date month 2018 Thesis can be found in The library of the Graduate University of Science and Technology, Vietnam Academy of Science and Technology 1 INTRODUCTION The urgency of thesis Today, the rapid growth of industries is in parallel with the level of serious environmental pollution, especially water pollution The textile industry is one of the industries that causes bad water pollution due to direct discharge of wastewater into rivers The World Bank estimated that from17 % to 20 % of industrial water pollution came from dyeing and fabric processing plants which cause alarming number for textile manufacturers, as well as environmental managers and scientists So far, the methods of treating textile wastewater are used such as coagulation, sintering, biodegradation, adsorption by activated carbon, oxidation methods Among these methods, the biodegradation is widely applied to treat textile wastewater on a large scale However, under anaerobic condition, azo dye can be reduced to byproducts as the very toxic aromatic amines Recently, we have found out advanced oxidation method which is a new and promising method for treating textile and dyeing wastewater This method usually uses a catalyst as photocatalysts to generate OH radicals , under illumination which have strong oxidizing ability and can breakdown most organic chemicals Photocatalysts are oxides such as TiO2, ZnO, SnO2, WO2 and CeO2, which are abundant in nature and are widely used by heterogeneuos processes Among them, ZnO is considered to be a promising catalyst for decomposition of organic pigments as well as for water disinfection The photocatalytic ability of ZnO is higher than that of TiO2 and some other semiconductor oxides on the basis of absorption of solar radiation energy However, ZnO has a relatively large (3,27eV) bandgap energy, which corresponds to the ultraviolet light zone for optimum photocatalytic efficiency Meanwhile, ultraviolet light accounts about % radiation of solar Therefore, practical application of ZnO has limited In order to improve photocatalytic activity and expand application field, it is necessary to transform the electron properties in ZnO nanostructure and reduce bandgap energy and electron recombination dynamics and optical hole properties DopedMetallic or non-metallic or co-doped metallic and non-metalic to the ZnO is one of the effective methods to increase photocatalytic activity of ZnO Thus, the research topic of the thesis "Synthesis and characterization of doped Mn, Ce and C to ZnO nanoparticles and evaluation of their photo- oxidation potentiability" was selected with the following objectives and contents: The objectives of the thesis: The thesis focused on the synthesis of Mn, Ce, C doped ZnO nanoparticles materials and doped ZnO with multi-layered carbon nanotube nanocomposite materials and assessed their photo-oxidative potentiality through photocatalytic reactions of methylene blue (MB) decomposition in aqueous solution under visible light The content of the thesis: 2.1 The material synthesis: - Synthesis of Mn doped ZnO and Ce doped ZnO nanoparticle materials by combustion and hydrothermal method; - Synthesis of C, Mn and C, Ce co-doped ZnO nanoparticles by hydrothermal method; - Synthesis of C, Ce co-doped ZnO combined with multi-layer carbon nanotube composite materials 2.2 Physical properties and characteristic studies of the synthesized materials: Synthesized materials were investigated using thermo-gravimetric and differential thermal analysis (DTA-TG), X-ray diffraction (XRD) analysis, Fourier-transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-VIS), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS), Brunauer-Emmett-Teller (BET)analysis and energy –dispersive x-ray spectroscopy (EDX) 2.3 Study of photo-oxidative potentiality of the materials: Synthesized materials were evaluated for photo-oxidative potentiality through photocatalytic reactions of methylene blue (MB) decomposition in aqueous solution under visible light CHAPTER 1: OVERVIEW 1.1 ZnO materials 1.1.1 Introduction of ZnO 1.1.2 Application of ZnO 1.2 Methods of synthesizing ZnO materials 1.2.1 Hydrothermal method 1.2.2 Combustion method 1.3 Doped ZnO materials 1.3.1 Doped ZnO materials 1.3.2 Reseaches of ZnO and doped ZnO photocatalytic materials 1.4 Photocatalyst 1.4.1 ZnO photocatalysis 1.4.2 Doped ZnO photocatalysis CHAPTER 2: EXPERIMENTS AND RESEARCH METHODS 2.1 Synthesis of materials 2.1.1 Synthesis of Mn doped ZnO and Ce doped ZnO 1.1.1.1 Synthesis of Mn doped ZnO and Ce doped ZnO by combustion method (Mn-ZnOĐC) a> Synthesis of Mn doped ZnO by combustion method 1,32 grams of PVA were dissolved completely in 40 ml of distilled water at 50oC, then cooled to room temperature and added slowly 9,9 ml of Zn(NO3)2 1M solution and 0,1 ml of Mn(CH3COO)21M solution (molar ratio Mn2+/ (Zn2+) = 1:100) The solution was stirred on the magnetic stirrer Distilled water was added and adjusted pH = by ammonium acetate buffer The solution was stirred continuously on the magnetic stirrer for about hours at 80°C until the water is evaporated completely The gel obtained is clear, transparent and viscous The gel was aged about 12 hours at room temperature anddred at 100oC and heated at 500oC to obtain gray powder The surveys on the conditions of Mn-ZnOĐC materials were synthesized - Effects of temperature: Experimental process was synthesized as above, the samples were calcited at different temperatures, from 300 to 800oC in the air with the heating ramp of 8oC/min - Effects of pH: The experiments werethe same conditions with different pH The pHs of the reaction solution were changed 3, 4, and respectively - Effects of doped manganese concentration: The molar ratios of Mn2+/ Zn2+ were 1%; 3%; 5% and 8% respectively 𝑃𝑉𝐴 - Effect of PVA content: The molar ratios of the synthesized 𝑍𝑛2+ +𝑀𝑛2+ of samples were 1/1; 2/1; 3/1 and 4/1 respectively - Effect of temperature of gel formation: The temperatures of gel formation were 50°C, 60°C, 80°C and 95°C, respectively b> Synthesis of ZnO doped by Ce by combustion method The synthesis of Ce doped ZnO(Ce-ZnOĐC) was the same as that of the Mn-ZnOĐC synthesis Salt Mn(CH3COO)2was changed by salt Ce(NO3)3 2.1.1.2 Synthesis of Mn doped ZnO and Ce doped ZnO by hydrothermal method a>Synthesis of Mn doped ZnO doped (Mn-ZnO) 0,664 g of Zn(CH3COO)2.2H2O and an amount of Mn(CH3COO)2.4H2O salt (the molar ratio of Mn2+/Zn2+ 2%) were dissolved in 75 ml of C2H5OH to obtain the solution A 0,4g of NaOH were dissolved in 75ml of distilled water to obtain solution B Solution A was added gradually to solution B and stirred for 1,5 hours The whole mixture was transferred to the autoclave and heat in the oven at 150°Cfor 24 hours cooled to room temperature, filtered and rinsed twice with distilled water and ethanol and dried the final product at 80°C for 10 hours to obtain a solid powder The survey on the conditions of material was synthesized - Effects of the temperature: The temperatures of hydrothermal were changed from 110°C to 170°C - Effects of NaOH concentration: The molar ratios of NaOH/Zn2+were changed 1.5; 3.0 and 6.0 - Effect of solvent: The volume ratio (ml) of water/ethanol (H/R) solution were 150/0, 70/80, 110/40 and 40/110 - Effect of doped manganese content: The molar ratios were Mn2+/Zn2+ were 1%, 2% and 6%, respectively - Influence of PVA content: Experiments carried out were 7%, 10% and 15%, respectively b> Synthesis of Ce doped ZnO by hydrothermal method The synthesis of Ce-ZnO was prepared similarly to the Mn-ZnO synthesis Salt Mn(CH3COO)2 was replaced by salt Ce(NO3)3 2.1.1.3 Synthesis of C, Mnco- doped ZnO and C,Ce co-doped ZnO by hydrothermal method a> Synthesis of C and Mn co-doped ZnO by hydrothermal method (C, MnZnO) 0,664 g of Zn(CH3COO)2.2H2O and 0,015 g of Mn(CH3COO)2.4H2O salt (the molar ratio of Mn2+/Zn2+ 2%) were dissolved in 60 ml of C2H5OH to obtain the solution A 0,0132 g of PVA (the molar ratio of PVA/Zn2+ =10%) were dissolved in 30 ml of distilled water to obtain solution B 0,4 g of NaOH (the molar ratio of NaOH/Zn2+ = 3) were dissolved in 60 ml of C2H5OH to obtain solution C Solution A was added gradually to solution B and stirred for 0,5 hours Then, solution C was added gradually and stirred for hours This mixture was transferred to the autoclave and heat in the oven at 150°C for 24 hours After, the autoclave was cooled to room temperature The thermal products were filtered and rinsed twice with distilled water and ethanol and dried the final product at 80°C for 10 hours to obtain a solid powder The survey on the conditions for material was synthesized - Effects of the temperature: The temperatures of hydrothermal were changed from 110°C to 170°C - Effects ... non-metalic to the ZnO is one of the effective methods to increase photocatalytic activity of ZnO Thus, the research topic of the thesis "Synthesis and characterization of doped Mn, Ce and C to ZnO nanoparticles. .. to the Mn -ZnO synthesis Salt Mn(CH3COO)2 was replaced by salt Ce( NO3)3 2.1.1.3 Synthesis of C, Mnco- doped ZnO and C ,Ce co -doped ZnO by hydrothermal method a> Synthesis of C and Mn co -doped ZnO. .. method The synthesis of Ce doped ZnO (Ce- ZnO C) was the same as that of the Mn -ZnO C synthesis Salt Mn(CH3COO)2was changed by salt Ce( NO3)3 2.1.1.2 Synthesis of Mn doped ZnO and Ce doped ZnO by hydrothermal