Photochemical degradation of Rhodamine B in aqueous solutions using ZnO nano photocatalyst contaminated with C, N, S

Number of pages: 119 File Format: word File Code: 31868
Year: 2014 University Degree: Master's degree Category: Chemical - Petrochemical Engineering
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  • Summary of Photochemical degradation of Rhodamine B in aqueous solutions using ZnO nano photocatalyst contaminated with C, N, S

    Dissertation for M.S.c degree

    Trend: applied

    Abstract:

    In recent years, semi-conducting nanoparticles due to electrical and mechanical properties, which are limited quantum effects compared to Their counterpart materials have attracted a lot of attention. Among semiconductor nanoparticles, ZnO nanoparticles have higher efficiency. In order to achieve higher photocatalytic activity, semiconducting nonmetal ZnO doped with C,N,S was prepared.

    In this thesis, the photocatalytic degradation of rhodamine B pigment was investigated using ZnO/C,N,S nano photocatalyst synthesized in the laboratory. Zinc sulfate and thiourea were used as raw materials. Photochemical degradation of paint using ZnO/C, N, S nano photocatalyst was investigated by reviewing changes in material concentration using UV spectrophotometric technique according to irradiation time. The shape, structure and optical properties of this photocatalyst were determined by XRD, XPS, EDX and FE-SEM photo.

    The rate of rhodamine B color degradation, in the presence of UV lamp, by examining various factors such as the effect of color concentration, a specific amount of photocatalyst, pH of the solution, the presence of various oxidants such as H2O2, K2S2O8, KBrO3, KIO3, mineral ions, irradiation time. The optimal conditions for the maximum degradation were determined. In the present work, based on the results, the optimal amount of photocatalyst used is 7 mg, the color concentration is 20 ppm, and pH=9. It should be noted that the greatest degradation occurred in the presence of the oxidant K2S2O8 with a value of (mM3). style="direction: rtl;">

    Introduction:

    The topic studied in this thesis is the photochemical degradation of rhodamine B in aqueous solutions using ZnO nanophotocatalyst contaminated with C,N,S. Rhodamine B is a synthetic dye that belongs to the class of xanthene dyes. This color is used in the textile industry, leather industry, pharmaceuticals and as an additive color for cosmetics. Due to its toxicity and carcinogenicity, it causes many problems for living beings.

    This dye causes a lot of environmental effects due to its wide use and causes domestic and industrial wastewater pollution. In this project, the goal is to remove this dye from solvent wastewater with the help of photochemical degradation using nano photocatalyst ZnO contaminated with nonmetals (C,N,S) and find the optimal degradation conditions.

    On the other hand, achieving the best conditions for photochemical degradation of paint with the help of ZnO photocatalyst contaminated with non-metals (C, N, S) by examining various factors affecting the degradation process, it is possible to propose the process in a laboratory pilot to paint production companies, water and wastewater, textile and pharmaceutical industries. The results of this research, in addition to expanding the boundaries of knowledge and observing economic aspects in solvent recovery, can prevent the entry of toxic and dangerous chemicals into running water and wastewater that the raised issues clarify the necessity of conducting the present research and the goals of this research for us.

    The questions and hypotheses that we face in this project include:

    Degradation of paint is done with the help of UV light and ZnO photocatalysts contaminated with non-metals (C,N,S)

    .                                                                                   

    2. Evaluation of the amount of destruction is done with the help of spectrophotometric absorption measurement.

    3. Optimum reaction conditions in terms of pollutant concentration and amount, photocatalyst amount, pH, temperature, etc. is checked.                                   

    4. Degradation kinetics is investigated in terms of reaction order. 

    5. Comparison of color degradation by visible and ultraviolet light under the same conditions.      

    Chapter One

    General

    Removing impurities by photocatalytic destruction method

    Various chemical methods such as sedimentation and separation of pollution, Coagulation [1], electric coagulation [2] and removal by absorption process on the absorbent surface (for example on active carbon) etc. are not destructive methods and only transfer pollution from one place to another [1]. Therefore, another method is needed to remove pollution.

    Among the number of proposed methods and even developed methods in order to destroy organic pollution, the method of biological destruction [3] or microbial [4] have attracted the most attention. However, a large number of organic compounds could not be modified by microbial methods [2]. Recently, the studies of scientists have focused on the use of semiconductors as a tool for the oxidation of various organic chemical poisons [3, 4].                                                 

    Most colored compounds have a polar molecular structure, so they are not completely absorbed under the soil and by dissolving in underground water, they penetrate into surface water [5 and 6].

    Since photocatalytic degradation has advantages such as not producing chemical residues and toxic waste at the end of the process, it can be a very suitable method for cleaning all kinds of Wastewater should be used [6]. Ultraviolet rays are a very strong and simple oxidant. This radiation has a high potential for oxidation at a wavelength of 253.7 nm with a strength of 4.89 electron volts, which is suitable and sufficient for interaction with the electronic structure of materials [7]. Recently, the study of advanced oxidation processes [5] for the complete destruction of all kinds of organic structures has attracted a lot of attention. This method is based on the production of active particles such as Hydroxyl radicals (which have the ability to oxidize a wide range of organic pollutants with high speed and without selectivity) are stable [8]. AOPs include photocatalytic systems such as the combination of semiconductor and light or semiconductor and oxidant. Today, heterogeneous photocatalysts are known as the most widely used destructive technology, which completely convert most organic pollutants with aliphatic and aromatic molecular structures [6] into inorganic form [9-13].

    Choosing an optimal condition for removing colors and destroying their structure requires many investigations and studies. Considering the commercial and environmental importance of paints, all factors participating in the degradation process, including photocatalyst, oxidant, radiation intensity, etc., should be studied and investigated. In the next part, we will examine some of these factors.

    Familiarization with some photocatalysts in destructive reactions

    The photocatalysts used in photocatalytic degradation reactions are semiconductor oxides in nano dimensions, these catalysts are very efficient due to their high surface to volume ratio. Common photocatalysts in photocatalytic degradation reactions are semiconductor oxides in nano dimensions. Nowadays, the use of semi-conducting materials in nano dimensions has attracted a lot of attention and has wide applications such as: photoelectric energy, material conversion [14-16] and water and air purification as environmentally friendly photocatalysts [17, 18] and super magnetic materials [19]. Some semiconductors such as TiO2, ZnO, SnO2 have a very high photocatalytic ability due to their gap gap [20]. 1-2-1 TiO2 photocatalyst Titanium dioxide photocatalyst is one of the most important and widely used photocatalysts used to degrade organic substances. The photocatalytic activity increases with the reduction of TiO2 particles, with the reduction of the particle size, the surface area of ??TiO2 increases, which improves the photonic effect and consequently the catalytic properties [21 and 22].

    TiO2 is a wide bandgap semiconductor, in TiO2, the valence band is made of hybridized p2 orbitals with d3 states of titanium, while Conductive tape is obtained from pure titanium d3.

  • Contents & References of Photochemical degradation of Rhodamine B in aqueous solutions using ZnO nano photocatalyst contaminated with C, N, S

    List:

    Abstract: 1

    Introduction: 2

    General Chapter. 3

    Unpure removal of photocatalytic degradation products. 4

    Familiarity with a number of photocatalysts and destructive reactions. 5

    1-2-1 TiO2 photocatalyst. 6

    1-2-2 ZnO photocatalyst: 10

    Chapter 2 describes symptoms and other studies in this field. 17

    2-1 Introduction. 17

    2-2 Color forming components. 19

    2-3 characteristics of color constituents. 20

    2-3-1-color pigments: 20

    2-3-2-resins: (Resin) 20

    2-3-3 solvents. 21

    2-3-4 color additives. 21

    2-5 Water Pollution 22

    2-5-1 Pollution caused by dyes 23

    2-5-2 Pollution caused by solvents 24

    2-6 Nanotechnology in the water industry. 24

    2-7 Investigating methods of wastewater purification using nanotechnology 26

    2-7-1 Porous nanopolymers. 27

    2-7-2 nanofilters 27

    2-7-3 nanophotocatalysts 29

    2-8 solvent purification methods. 31

    2-9 basic laws of photochemistry. 32

    2-9-1 molecular excitation and relaxation processes. 32

    2-9-2 Excited electron carriers 34

    2-9-3 Position of the band. 38

    2-9-4 electron transfer process on the catalyst surface 39

    2-10 different mechanisms of photocatalytic destruction. 40

    2-10-1 oxidation of hydroxyl radicals. 42

    2-10-2 Kolbe photochemical reaction. 44

    2-11 Semiconductor nanomaterials with photocatalytic properties. 44

    2-11-1 Quantum size effects (QSE) 1. 45

    2-11-2 Effects of increasing solar surface area. 46

    Chapter 3 Methods and materials used 15

    3-1 Chemicals used 47

    3-1-1 Pollutants used 47

    3-1-2 Chemical compounds. 47

    3-1-3 photocatalysts 47

    3-2 devices used 48

    3-2-1 ultraviolet-visible spectrometer (UV-Vis) 48

    3-2-2 centrifuge 48

    3-2-3 digital scale. 48

    3-2-4 water distiller. 48

    3-2-5 PH meter 48

    3-2-6 photochemical reactor. 48

    3-3 Software used 50

    3-3-1 Minitab 15 software. 50

    3-4 ZnO/C,N,S photocatalyst synthesis. 50

    3-5 absorption spectrum and standard curve for the pollutant under investigation. 51

    3-6 photocatalytic degradation experiments and investigation of different reaction conditions. 51

    3-6-1 Checking the effect of catalyst type 52

    3-6-2 Checking the effect of UV radiation. 52

    3-6-3 Investigating the effect of oxidants on photocatalytic reactions. 53

    3-6-4 Checking the effect of pH. 53

    3-6-5 Investigating the effects of radiation time. 53

    3-6-6 Investigating the effect of catalyst amounts 54

    3-6-7 Investigating the effect of color concentration on photocatalytic degradation. 54

    3-6-8 Investigating the effect of the rotation speed of the magnet. 54

    3-6-9 Investigating the effects of mineral ions. 55

    3-6-10 Kinetic studies. 55

    3-6-11 Review of photocatalytic degradation experiments using the Taguchi method. 55

    Chapter Four Results. 59

     

    4-1 XRD, FE-SEM, XPS, EDX spectrum to ensure the synthesis of ZnO/C, N, S nanophotocatalyst. 59

    4-1-1 XRD. 59

    4-1-2 FE-SEM. 61

    4-1-3 XPS. 61

    4-1-4 EDX. 62

    2-4 drawing of the standard curve for determining pollutant concentration 63

    4-3 Results of inspection of photocatalytic dye degradation tests. 64

    4-3-1 The results of the investigation of the photocatalytic ability of different photocatalysts in pollutant degradation 65

    4-3-2 The results of the investigation of the effect of UV light in the degradation of paint. 66

    4-3-3 The results of investigating the effect of depressants on photocatalytic degradation. 67

    4-3-4 results of investigation of pH effect. 72

    4-3-5 results of investigation of radiation time effect. 74

    4-3-6 results of investigation of the effect of the presence and amount of catalyst 76

    4-3-7 results of investigation of the effect of color concentration. 78

    4-3-8 The results of investigating the effect of the rotation speed of the magnet. 80

    4-3-9 results of investigation of mineral ions. 80

    4-3-10 results of kinetic studies. 82

    4-3-11 The results of investigating photocatalytic degradation of rhodamine B using the Taguchi method. 85

    Chapter five discussion and conclusion. 91

    5-1 The general results of what was achieved in this project are summarized as follows: 91

    5-2 Side research works. 92

    References. 91

     

    Abstract 105

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Photochemical degradation of Rhodamine B in aqueous solutions using ZnO nano photocatalyst contaminated with C, N, S