Tài liệu Evaluation on the photocatalytic decompose of toluene using led ultraviolet light uva

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURAL AND FORESTRY HA THI NGOC EVALUATION ON THE PHOTOCATALYTIC DECOMPOSE OF TOLUENE USING LED ULTRAVIOLET LIGHT BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : International Programs Office Batch : 2014 - 2018 Thai Nguyen, 25/09/2018 Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student name Ha Thi Ngoc Student ID DTN1453170024 Thesis Title Evaluation on the photocatalytic decompose of toluene using LED ultraviolet light UVA Supervisor(s) 1. Prof. Sue-Min Chang 2. Dr. Nguyen Huu Tho Supervisor’signature Abstract: Environmental cleanup by the photocatalytic degradation of pollutants using TiO2 was proposed. Key features of the technology include rapid response to visible light and rapid recycling of the magnetic nanofibers with an outside magnet. Specially, if irradiated TiO2 with the light have energy matching its bandgap, semiconducting TiO2 at anatase form generates photocurrent in a photoelectron chemical system. When irradiation the UV light, the electron-hole pairs in TiO2 will be generated. Whereas, from this advantage, photocatalysis now using to degrade nonbiodegradable toxic contaminants into their nontoxic degradation products. The results shows that, the high development of the TiO2 surface result in the ratio of surface to high volume creates favorable conditions for the transfer of charge in the redox holes and redox reduction and priority to increase the activity of photocatalytic. i Keywords Photocatalytic, photocatalysis, toluene, ultraviolet, UVA. Number of pages 32 Date of submission 25/9/2018 ii ACKNOWLEDGMENT No success is associated with the relief of more or less, directly or indirectly, of others. From the beginning of my studies at the university, I have received a lot of help from teachers and friends. I would like to sincerely thank the teachers in the Faculty of International Program, Thai Nguyen University of Agriculture and Forestry who have been passionate in imparting knowledge during their years of study here. With the knowledge acquired during the learning process is not only the basis for the research process but also valuable jewelry to my life in a firm and confident. Deepest appriciation to the kind and helpfu adviser, Prof. Sue Min Chang of Institue of Environmental Engineering National Chiao Tung University, Taiwan which serve my greates inspiration; for giving me the opportunity to be a member of Environmental Nanomaterial Lab; for suggesting the ideas and assistance as the author conducted my research study. Sincerest thank to Dr. Nguyen Huu Tho Office of Research and International Affairs of Thai Nguyen University of Agriculture and Forestry. Thanks for his guidance and interest in helping me to the complete of this thesis. Ever grateful to Staff of Environmental Nanomaterial Laboratory of National Chiao Tung University for providing equipment to conduct my research; for sharing knowlegde and happy memories along my journey in Taiwan. Harvesting is done over a period of 4 months. Initially went into the field of science research, my knowledge is limited, so inevitably left many shortcomings. I hope to receive the comments of teachers so that my knowledge in this field is more complete. Student Ha Thi Ngoc ~ ii ~ TABLE OF CONTENTS LIST OF ABBREVIATIONS .........................................................................................v LIST OF FIGURE ..........................................................................................................vi PART 1. INTRODUCTION ............................................................................................1 1.1. Research rationale .....................................................................................................1 1.2. Research’s Objective ................................................................................................1 1.3. Research’s Contents ..................................................................................................2 1.4. Research’s Scope ......................................................................................................2 PART 2. LITERATURE REVIEW .................................................................................3 2.1. Toluene......................................................................................................................3 2.1.1 Toluene and its application. ....................................................................................5 2.1.2 Toluene toxicity ......................................................................................................5 2.2. TiO2 photocatalysis ..................................................................................................5 2.2.1. Photocatalysis mechanism .....................................................................................8 2.2.2. TiO2 photocatalysts................................................................................................8 2.3. Photocatalysis .........................................................................................................16 2.4. UV absorption .........................................................................................................17 PART 3. MATERIALS AND METHODOLOGY .......................................................18 3.1. Materials ................................................................................................................18 3.2. Experimental methods ............................................................................................18 3.2.1 Synthesis TiO2 and Fe-TiO2 ..............................................................................18 3.2.1 Surface doping Fe .................................................................................................18 3.2.2 Test the degradation rate of toluene by using 3 samples of powder produced. 19 3.2.4 Investigate the effective way to let the degradation process go faster. ................19 PART 4: RESULTS ......................................................................................................21 4.1 Result of synthesis photocatalyst.............................................................................21 4.1.1 Photocatalyst P25 ...............................................................................................21 4.1.2 Product of synthesized TiO2..............................................................................21 4.1.3 Product of doped iron(Fe) ...................................................................................22 4.1 Results of photocatalyst by deposition ...................................................................22 4.2 Results of different conditions ................................................................................23 ~ iii ~ 4.3. Results of different light intensity ..........................................................................24 4.5 Results of different concentration ...........................................................................24 PART 5: Discussion and Conclusion ............................................................................26 5.1 Discussion ...............................................................................................................26 5.2 Conclusion ..............................................................................................................28 REFERENCES ..............................................................................................................30 ~ iv ~ LIST OF ABBREVIATIONS VOCs : Volatile Organic Compounds PCO : Photocatalytic oxidation EPA : Environmental Protection Agency GC : Gas Chromatography machine AC : Active Carbon IPA : Isopropalnol HTOPs: Highly Toxic Organic Pollutants CB : Conduction Band SPF : Sun Protection Factor VB : Valence Band WBS : Wide Band-gap Semiconductor ~v~ LIST OF FIGURE Figure 1. Toluene chemical structure .............................................................................4 Figure 2: Photo catalyst oxidation process ....................................................................6 Figure 3. Schematic image for the kinetic and thermodynamic control polymerization of TiO6 octahedral units as the nucleation of anatase and rutile in TiO2. ....................10 Figure 4: Photocatalyst was irradiated using UVA LED 370nm .................................20 Figure 5: Commercial photocatalyst P25 powder ........................................................21 Figure 6: TiO2 powder made in laboratory ..................................................................21 Figure 7: Fe-TiO2 powder made in laboratory .............................................................22 Figure 8: Product of iron doping on TiO2 using filter paper ........................................22 Figure 9: Environment condition affect to the degradation of toluene.........................23 Figure 10: Light irradiation at different distance to the photocatalyst ......................24 Figure 11: Different concentration degradation through the time ...............................25 ~ vi ~ PART 1. INTRODUCTION 1.1. Research rationale Toluene is the popular solvents in daily life, contributing to the development of society. Toluene is a very important raw material in the industry, as well as a good organic solvent, but it also has serious effects on the body and the environment. Humans are both responsible for the toluene pollution in their living environment and are the primary victims of exposure in the manufacturing sector. However, because of its importance, people still use a lot of toluene in the manufacturing sector. Understanding the toxicity of toluene is necessary to take preventive measures in the produce and create of toluene. So in this essay toluene was chosen as the object of study, review. Because of the benefits in minimizing of Highly Toxic Organic Pollutants (HTOPs), photocatalytic properties of titania are studied in depth in wastewater treatment (Shen, 2016). Toluene was discovered by P. Kelley and P. Walter in 1037 when he developed coal gas from resin. Hence, in the present work, to study the application of photocatalyst for degradation of toluene, and evaluate the toluene degradation of this material in comparison with difference condition. The nanotechnology concept has evolved since its future application to the present location is a research innovation with wide applications in many aspects of science. 1.2. Research’s Objective - Evaluate the capability of P25, TiO2 powder, Fe/TiO2 in the degradation of toluene. - Examine photocatalytic activity under the UVA light source - Assess these condition has effect on the degradation of toluene. ~1~ 1.3. Research’s Contents 1. Literature review about toluene, its adverse effects on ecosystem and human health. 2. Synthesis and investigate the characteristics of materials to the degradation of toluene. 3. Compare the photocatalytic activity differences type of photocatalysts to ward toluene degradation. 1.4. Research’s Scope The sample of toluene and photocatalyst were prepared in Environmental Nanomaterial Laboratory, Chiao Tung University, Taiwan. The experimental process was done in the laboratory. ~2~ PART 2. LITERATURE REVIEW 2.1. Toluene Volatile compounds that exist in the atmosphere, such as toluene, are very noticeable because they cause side effects on human health as well as the environment (Beydoun et al., 1999; Bernstein et al., 2008).. Research shows that regular exposure to toluene easily leads to neurological complications, such as memory loss and muscle growth, as well as some degree of hearing loss and color vision (Peral et al., 1997; Neubert et al., 2001). EPA (Environmental Protection Agency) reported that toluene was found in well water, surface water, or soil and its relative vapors are also present in air. Because of its usage in consumed products, the concentrations of toluene in indoor air may surpass those in outdoor air. Indoor toluene levels from consumer products and outdoor levels due to car or gasoline emissions, are estimated to be an average absorbed dose of 300 µg/day. Toluene plays an important role as the starting material in the explosive industry and is used as a solvent. The maximum toluene concentration is within the current allowed level of about 200 parts per million part of air. But there is little evidence to be able to maintain the validity of this concentration always within the maximum allowable limit.Air quality control remains one of the most important issues in environmental science and technology research. Photocatalytic oxidation (PCO) processes have been studied to a high degree to control air quality when the target compounds are CO, NO, volatile organic compounds (VOC) and bioaerosol in an enclosed environment PCO is valuable for controlling these compounds, especially in ~3~ their depressive conditions. To remove VOC from polluted air, TiO2 catalysts are popular because of their high activity, safety and low cost. The visual oxidation of organic compounds including aromatic compounds on TiO2 catalysts irradiated at close range has been elucidated. The toluene name is derived from the toluol name, which stands for "TOL" the balsamic resin of South America. Toluene is a transparent liquid, low viscosity. Toluene is water-insoluble liquid, it can melt completely with most organic solvents such as alcohol, ether, ketone ...Toluene is a flammable and predominantly used as an industrial feedstock and a solvent. Figure 1. Toluene chemical structure The toluene molecule consists of two parts: the benzene ring and the ankyl ring. So its properties include the aroma of the benzene ring and the satiety of the base. However, the nature of the benzene ring and the alkyl base is altered by the relative influence between the two. The basic reaction of toluene is the substitution reaction SE plus in the benzene ring, reaction SR , Oxidation at methyl base. Application of toluene Toluene is an aromatic hydrocarbon that is widely used in the industry, often ~4~ as a substitute for benzene: Toluene is used primarily in applications requiring solubility and the highest volatility. 2.1.1 Toluene and its application. As in the manufacture of synthetic resins, automotive paints, interior paint and marine paint, toluene is highly soluble, so it is used in the production process of adhesives and binders. Toluene is also used as a diluent and as a component in detergents, in the manufacture of benzene and in the manufacture of dyes, textiles, and many other industries. 2.1.2 Toluene toxicity • If exposed to toluene for a long time, cancer may develop. • Eye contact: Stimulating, but does not affect the eye membrane. • Skin contact: Frequent or prolonged contact may be irritated and inflamed. Short and irregular contact with liquids will not cause serious irritation, which occurs when evaporation occurs. Skin contact may cause severe dermatitis. • Inhalation (respiratory system): High evaporation content (greater than about 1000 ppm) causes eye and respiratory irritation, can cause headaches, drowsiness, unconsciousness, affecting the nerve center , brain damage and can cause death. • Ingestion (digestive system): A small amount enters the abdomen or causes or damages the human lungs, which cause death. 2.2. TiO2 photocatalysis Titanium dioxide (TiO2) is a semiconductor and is famous as an anti-ultraviolet (UV) catalyst in oxidizing photos of organic matter and inactivating bacteria, algae and viruses. ~5~ By absorbing the energy of light, titanium oxide changes from the insulating property to a conductor, so it is thought to be an optical semiconductor. This happens because the excited electrons move from the valence band to the conduction band and create holes in the valence band. The excited electrons react with oxygen in the atmosphere to form superoxide anions, the holes continue to react with atmospheric moisture to produce hdroxyl radicals. These types of active oxygen readily react, oxidize and decompose organic matter Figure 2: Photo catalyst oxidation process With an angle of contact with water of 5 ° or below, the surface of titanium oxide exhibits super permeability when exposed to light. Under the light irradiation, the electron-hole pairs are formed once again, the superfluidity is a straightforward result of the formation of oxygen vacancies due to the interaction of the holes with the ~6~ oxygen atoms in the lattice. Such holes form a hydrophilic area, and because water is readily adsorbed there, super-permeable products are generally. Advanced oxidation processes (AOP) with UV irradiation and titanium photocatalytic titanium (TiO2) are improving their ability to accept conveniently as an effective wastewater treatment. A comprehensive review of UV-TiO2 catalyst oxidation was conducted with insight into the relevant equipment, TiO2 catalysts, irradiation sources, and reactor types, comparisons among Effective mode of TiO2 application as surface immobilization or as system suspension. Photocatalytic decomposition technology with titanium dioxide is often used to treat wastewater containing organic pollutants due to the ability to achieve complete mineralization of organic pollutants under mild conditions such as temperature environment and environmental pressure. Recently, photocatalytic studies using TiO2 have drawn attention to the degradation of persistent organic pollutants and other organic chemicals known as endocrine disruptors.Waste water treatment in titanium dioxide suspended mud reactor has been widely used due to its simplicity and improved degradation efficiency. However, this system requires the separation of TiO2 from the water after the photocatalytic process.The final part of the manuscript focused on removing TiO2 with the hybridization system. A two-stage coagulation and deposition process associated with the microfiltration hollow microfiltration process has been found to completely remove TiO2, and the recovered TiO2 can be reused for photocatalytic processes after reincarnated (Korea J, 2008). ~7~ Semiconductors are primary light absorbers. Due to a favorable combination of electronic structure, absorption properties, they are used in photocatalysis (S. Sappideen, PhD Dissertation, 2000). 2.2.1. Photocatalysis mechanism 2.2.2. TiO2 photocatalysts (a) TiO2 (b) TiO2 was singled out as an important oxide material in the wide-ranging review of future directions in solid chemistry of nation by Cava et al. (2002) for the US National Science Foundation. The photocatalytic cleavage of water on TiO2 electrodes, named the “Honda–Fujishima Effect,” was reported by Fujishima and Honda in 1972. TiO2, the naturally occurring oxide of titanium, was discovered in 1795, and its commercial production started in the 1920s. (c) An extensive and extensive literature on titanium dioxide polymorphs (TiO2) has been accumulated over the past few decades, providing a huge source of data on its properties, functions and many current and potential industrial applications. TiO2 has been used in many commercial applications including as an opacifying agent in paints, plastics, paper textiles and inks, corrosion-resistant coating, antimicrobial, air and water cleaning, self-cleaning surfaces, food additives as a ultra-violet absorber in cosmetic products. In addition to its current use in industry, TiO2 has been extensively studied for applications in water remediation, photocatalysis, recharcheable batteries, super capacitors and sensor devices etc. (d) Substances studied in different lighting conditions. The initial reaction step involves the creation of electron-hole pairs by irradiating TiO2 with light that has ~8~ a higher energy content than the band gap (Uddin et al., 2007). For TiO2 anatase and rutile, the band gap ranges are 3.2 eV and 3.0 eV, respectively, with wavelengths of 388 nm and 410 nm (Mills et al., 1997 Therefore, ultraviolet (UV) is needed to activate TiO2.With UV irradiation, electron pairs are excited in the valence band of TiO2 and then move to the surface to initiate redox reactions for adsorbed organic pollutants (Zhang et al. , 2007).The design of the TiO2 photocatalyst is embedded in supporting materials with a large surface area, which can condense the diluted pollutants, which is of great significance, not only to avoid small photocatalyst particles but also more effective. Various alternatives have been proposed over the past few years, having tried various auxiliary materials and coating methods in different arrangements to decompose some organic compounds. One possible way is to use materials such as glass beads, glass tubes, fiberglass, quartz, stainless steel, aluminum, activated carbon (AC) and silica (Hosseini et al., 2007). AC is another type of adsorbent that is used in the decomposition of organic pollutants in the aqueous phase. (e) This effect explained that the adsorption of organic matter on AC is followed by a transition to the TiO2 surface, where they are attenuated immediately. It is based on the interaction between light particles and semiconductors, producing highly reactive oxygen species, such as OH• , O2•- and HO2• . In general, the main issues for practical catalytic applications are the specific surface area, the range of absorption of the UV light spectrum and the photochemical or efficiency of photochemical catalysts (Ao et al. ., 2003) ~9~ (f) TiO2 is a simple inorganic compound that exists in four basic crystal forms (space groups): anatase , rutile, brookite (Pbca) and TiO2. Furthermore, the TiO2 phase diagram is rich at elevated pressures, including high pressure phases thought by geologists to be candidates for the minerals in the Earth’s mantle. Columbite (Pbcn), baddeleyite (P21/c), cotunnite (Pnma), pyrite and fluorite structures are high pressure polymorphs of TiO2. (g) Rutile, the most stable phase at ambient pressure and temperature at macroscopic size while anatase is more stable at nanoscale (Shannon, R.D., 1965). (h) (i) (j) (k) (l) (m) (n) (o) Figure 3. Schematic image for the kinetic and thermodynamic control polymerization of TiO6 octahedral units as the nucleation of anatase and rutile in TiO2. (p) Geometrically, the ratio of cis coordination positions to anatase to rutile is 7/1 in octahedral dimer. Because of the symmetry broken down in the anatase cutter, only half of the cis coordinate sites are arrowed on the anatase regulator. The high probability for cis coordination polymerization is why atanase tends to form as easily as metastable structures. ~ 10 ~ (q) The more compact structure of rutile relative to anatase causes important differences in physical properties. Rutile has a higher refractive index, higher specific gravity and greater chemical stability than anatase. Rutile melts at 1825˚C while anatase irreversibly transforms to rutile beginning at about 500˚C. Brookite is the unusual naturally form of TiO2 and is difficult to produce in pure form. Brookite has the same color and luster as the rutile. Its hardness and density are almost the same as that of rutile. TiO2 is less well known than rutile, anatase and brookite. TiO2 was synthesized in 1980 by Marchand et al., and found in nature by Banfield et al. in 1991. “B” in TiO2(B) stands for bronze, by analogy with the tungsten bronze compounds. TiO2(B) is the least dense of the four natural polymorphs of TiO2, so it seems to be a great host for the alternating Li compared to other polymorphs. However, due to its metastable properties, only a few investigations have been carried out in the field of electrochemistry. (r) The biggest barrier to using TiO2 as a photo-activated the catalyst is the large energy gap between the conduction band and the valence.Excitation of electrons over this wide band distance is possible with respect to only 3%–4% of the air-mass 1.0 solar spectrum. Therefore, numerous efforts have been made to reduce the TiO2 band gap to operate effectively with visible light. Lowering the band gap of TiO2 is also expected to pave the way for applications in the field of renewable energy, including photovoltaic cells and hydrogen production by photo catalysis.. (s) The thermodynamic properties of micro-and nanoparticles depent on surface energy, this energy also a factor determining nanoparticles properties. Nanosized particles contained higher surface areas, and this make surface energy greater. ~ 11 ~ (t) For maximizing the efficiency of photo catalytic reactions, an essential factor by deposition of a noble metal on semiconductor nanoparticles. It is well-known assumed that the noble metal acts as a sink for photo-induced charge carriers and promotes interfacial charge transfer process. Because the Fermi concentration of these noble metals are lower than that of TiO2, photo-excited electrons can be moved from the CB to metal particles deposited on the surface of TiO2, while photo generated VB holes stayed on the TiO2. These activities help to greatly reduce the possibility of electron-hole recombination, making an efficient division and stronger photo catalytic reactions. The TiO2 doping has different surface properties compared to pristine TiO2 including thickness of the space charge layer, existence and concentration of surface states. By doping, the chemical nature and electronic structure of doped-oxide was changed. To improve the performance of TiO2, by narrowing band gap could leads to increased photoactivity in the visible spectral region. It has been observed that the threshold image energy for activating the doped Titania samples changes, which causes the adsorbed edge to shift red to improve Titania's luminescent properties. (u) By enhancement or reduction of photo catalytic activity, the explanation in terms of alteration of the bulk electronic structure of the semiconductor, could influences its electron-hole generation and separation capacity under illumination. The position of the Fermi energy level, the formation of new energy levels by the interaction of a derivative alternating with the semiconductor network and the conductivity of the semiconductor, also affects surface properties such as thickness of space charge layer, existence and concentration of surface state and potential for decomposition which affect the photo corrosion process. Although disagreements ~ 12 ~