Summary of doctor thesis: Research on effective treatment of DDT by photocatalyst method using Fe - CuOx /GO; SBA – 15 nanocomposite materials, Theoretical chemistry and physical chemistry

Objectives of the study: Focusing on studying how to incorporate of Fe and Cu atoms into GO and SBA-15 frameworks by atomic implantation method to create new, advanced and highly efficient nanocomposite catalysts for DDT treatment.

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - - NGUYEN THANH TUAN RESEARCH ON EFFECTIVE TREATMENT OF DDT BY PHOTOCATALYTIC METHOD USING Fe-CuOx/GO; SBA – 15 NANOCOMPOSITE MATERIALS Major: Theoretical Chemistry and Physical Chemistry Code : 62.44.01.19 SUMMARY OF DOCTOR THESIS Hanoi - 2019 The thesis was completed at Institute of Chemistry, Vietnam Academy of Science and Technology Supervisors: Prof PhD Vu Anh Tuan PhD Trịnh Khac Sau Reviewer 1: Reviewer 2: Reviewer 3: The dissertation defended at Graduate University of Science and Technology, 18 Hoang Quoc Viet street, Hanoi Time: hour, date /month/2019 The thesis could be found at: - National Library of Vietnam - Library of Graduate University of Science and Technology - Library of Institute of Chemistry INTRODUCTION * The thesis necessity Along with the economic development, Vietnam has been facing pollution problems arising from agricultural and industrial production activities In particular, Persistent Organic Pollutants (POPs) are halogenated organic compounds that are environmentally toxic and stable compounds They are capable of bioaccumulation through the food chain and stored for long periods of time with potential adverse impacts on human health and the environment Due to the hazardous potential of these compounds, 92 countries signed the Convention on May 22, 2001 in Stockholm (Sweden), commonly known as the Stockholm Convention to place a global ban on these particularly harmful and toxic compounds Initially, the Stockholm convention was designed to reduce and eliminate the 12 most dangerous POPs out of human life Among of the 12 POPs in the Stockholm Convention, up to types of POPs-pesticides include Aldrin, chlordane, DDT, Dieldrin, Endrin, Hetachlor, Mirex and Toxaphene Then, at the sixth meeting (May 2013), the convention added a list of POPs up to the total 28 of persistent organic pollutants In Vietnam, persistent organic pollutants such as Dioxin (due to war consequences, the burning of hazardous wastes, PVC, ), pesticides such as Chlordane, DDT, 2,4-D; 2,4,5-T as well as PCBs (from waste oil in transformers) cause serious pollution affecting human health, the environment and sustainable development To remove these pollutants in water environment, many methods have been used such as: adsorption, biodegradation, chemical decomposition, advanced oxidation In which the adsorption method causes secondary pollution, biodegradation method requires long time and low efficiency Therefore, the advanced oxidation processes (AOPs) improved the removal efficiency using photochemical nanocatalysts such as Fe2O3, Fe3O4, FeOOH, Feo is being studied throughly Advanced oxidation processes (AOPs) refer to an oxidation process through the formation of hydroxyl radicals (•OH) which is a promising approach to degrade primarily organic chemical contaminants in water treatment Advanced oxidation processes (AOPs) have shown many advantages such as costeffectiveness, high efficiency, low toxicity and simple operation Several recent studies have shown that the simultaneous incorporation of different metals and metal oxides onto the same carrier to enhance efficiency of these composite catalysts Among the carriers, graphene and graphene oxide (GO) have been received a great interest due to their unique structure and physical-chemical properties such as high conductivities at room temperature, high specific surface and chemical stability, and high visible light absorption ability Unlike graphene, graphene oxide (GO) contains functional groups like hydroxyl, carbonyl, epoxi, carboxylic on the surface, so it is easy to form covalent bonds, strong chemical bonds with transition metal ions Therefore, GO is an ideal carrier in the synthesis of new composite nanomaterials Meanwhile, SBA-15 is a material with well-ordered hexagonal mesoporous silica structure which has a very large surface area (600 - 1000m2/g) However, the purely siliceous SBA-15 has a lack of functionality due to its electrically neutral framework, it can be used as adsorbent but not as acidic or redox catalysts In order to use as catalysts, SBA-15 can be modified by incorporation of transition metals into framework by direct synthesis and post-synthesis In this thesis, we focus on studying how to incorporate of Fe and Cu atoms into GO and SBA15 frameworks by atomic implantation method to create new, advanced and highly efficient nanocomposite catalysts for DDT treatment From the above arguments, we choose the thesis topic: "Research on effective treatment of DDT by photocatalyst method using Fe - CuOx /GO; SBA – 15 nanocomposite materials" to research and evaluate the catalytic activity of these new catalytic systems for DDT degradation * Objectives of the study Focusing on studying how to incorporate of Fe and Cu atoms into GO and SBA-15 frameworks by atomic implantation method to create new, advanced and highly efficient nanocomposite catalysts for DDT treatment * Main research contents of the thesis - Synthesize some new and advanced nanocomposite materials based on metalic oxide combination with GO and SBA-15 as highefficiency photocatalysts for toxic and persistent organic pollutants treatment by various methods such as co-precipitation, hydrothermal and especially atomic implantation method - Study on structural characteristics, morphology and physicchemical properties of synthesized materials by modern methods such as XRD, FTIR, TEM, XPS, BET, UV-Vis - The photocatalytic activity of these novel materials under visible light for the removal of DDT from aqueous solution was investigated and discussed - Study on the influencing factors such as pH, H2O2 concentration, DDT concentration, catalytic concentration to the DDT degradation efficiency - Research and propose reaction mechanism, decompose DDT through intermediate products formed in the process of DDT decomposition on synthesized catalytic systems * Thesis structure This thesis consists of 136 pages, 78 figures, 25 tables and 143 references including these main parts: introduction, three chapters in content and conclusion The main results were published on journals: 02 articles was published on international journals, 04 article was published on national journals Chapter Literature review Chapter is presented in 36 pages, in which general introduction of persistent organic pollutants (POPs), structure and toxicity of DDT as representative for research in this thesis Also in this chapter, technologies to treat persistent organic substances in the world and in Vietnam are also explored Among the methods, Advanced Oxidation Processes (AOPs) have shown many advantages such as costeffectiveness, high degradation efficiency, low toxicity and simple operation Therefore the advanced oxidation processes (AOPs) was mentioned in this chapter includes the theoretical basis and classification of the AOP, the theoretical basis of Fenton processes (Fenton homogeneous process, Fenton heterogeneous process, Fenton photo process) Chapter also introduces some highly effective nanocomposite catalysts based on graphene, GO and SBA15 in the treatment of persistent organic pollutants in water environment Overview of synthetic methods, research and application of nanocomposite catalysts for advanced oxidation processes to treat persistent organic substances in water environment was introduced Evaluation and analysis of the applicability of these catalysts in environmental treatment: dye treatment; toxic organic substances and DDT Chapter Experimental Chapter is presented in 20 pages including: 2.1 Process of synthesizing materials - Synthesis of Fe3O4, Fe3O4/GO nanocomposite materials by coprecipitation method - Synthesis of TiO2/GO and Fe-TiO2/GO nanocomposite materials by hydrothermal method - Synthesis of Fe-Cu/SBA-15 and Fe-Cu/GO nanocomposite materials by atomic implantation method The equipment for synthesis of Fe-Cu/GO nanocomposite by atomic implantation method is illustrated in Figure 2.6 Figure 2.6 Schematic illustrating the equipment for synthesis of Cu/Fe/GO nanocomposite by atomic implantation method - Study on photocatalytic process in the decomposition reaction of DDT by these synthesized catalysts - Analysis and evaluation of intermediate products formed in the process of decomposing DDT on some of the most effective catalytic systems 2.2 Characterisation Techniques - Techniques for characterisation are approached from the modern method using research facilities in Vietnam and Korea: XRD, XPS, EDX, SEM, HR-TEM, BET, FT-IR, UV-Vis 2.3 Methods of evaluating the photocatalytic ability of materials in the photocatalytic process of decomposing DDT - Develop a model to assess the photocatalytic activity of materials in the reaction of DDT decomposition - Methods of analysis and determination of removal efficiency in DDT decomposition process: GC-MS, TOC Chapter Results and Discussions Chapter is presented in 60 pages including: 3.1 Characteristics of structure and morphology of catalytic systems 3.1.1 X-ray diffraction (XRD) Results of XRD for Fe3O4 and Fe3O4/GO samples (Figure 3.3) appear typical peaks of Fe3O4 at values of 2θ: 30.1 ° (220), 35.4 ° (311), 43, 05 ° (400), 54o (422), 62.51 ° (511) and 6395 ° (553) [88] Meanwhile, XRD patterns of GO, Fe/GO and Fe-Cu/GO samples (Figure 3.5) shows that the peak at position 2Ɵ ~ 11o is belong to GO material [42] When Fe3+ and Cu2+ was delivered on GO, the peak of GO in this position decreased sharply As shown in XRD diagram of Fe/GO and Fe-Cu/GO, there are typical peaks such as: 24.1 ° (012), 33.1 ° (104), 36.5 ° (110), 40, ° (113), 49.4 ° (024), 54.1 ° (116), 57.5 ° (018), 62.3 ° (214) and 64 ° (300) which fit the standard data for the structure of Fe2O3 Figure 3.3 XRD patterns of Fe3O4 Fe3O4/GO nanocomposite material Figure 3.5 XRD patterns of GO, Fe/GO Fe-Cu/GO nanocomposite material Figure 3.6 Small-angle X-ray scattering patterns (a) and wide-angle X-ray scattering patterns (b) of SBA-15, 5Fe-2Cu/SBA-15, 10Fe-2Cu/SBA-15 and 15Fe-2Cu/SBA-15 samples In figure 3.6, small-angle X-ray scattering patterns showed that all samples has three peaks, in which the peak intensity is sharp and strong at 2  0.8o and two peaks are smaller at 2 1.5o 2 1.7o that can be indexed as the (100), (110), and (200) diffractions of 2D hexagonal p6mm symmetry of SBA15, respectively [20,28,32] The peak intensity of these samples was slightly changed according to the different Cu-Fe loading amounts into SBA-15 framework 3.1.2 Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) Figure 3.9 FE-SEM image of Fe3O4/GO Figure 3.10 HR-TEM image of Fe3O4/GO Figure 3.11 TEM images of Fe-TiO2 (a) and Fe-TiO2/GO (b) SEM image (Figure 3.9) and HR-TEM image (Figure 3.10) show that Fe3O4 nanoparticles have a spherical shape with the size of 15-20 nm which dispersed well on GO carriers From TEM images of FeTiO2/GO and Fe-TiO2 nanocomposite materials shown in Figure 3.11, we can see that Fe-TiO2 nanotubes are dispersed on the layers of GO Fe-TiO2 nanotube structure has - 12 nm diameter and the tube length is about 100-200 nm There are some bundles of Fe-TiO2 3.1.3 Energy-dispersive X-ray spectroscopy (EDX) EDX mapping images and EDX analysis for the elemental composition (Figure 3.18 and 3.19) of nanocomposite Fe-Cu/GO showed that Fe content accounted for 17.87% by weight and Cu content only accounted for 1.84% by weight Figure 3.18 EDX mapping images and Figure 3.19 EDX analysis for the elemental composition of nanocomposite Fe-Cu/GO EDX analysis of Fe-Cu/SBA-15 nanocomposite materials with different Fe/Cu ratios showed that when Fe, Cu with content