Luận văn 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 h 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) Prof Sue-Min Chang 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 h Keywords Photocatalytic, photocatalysis, toluene, ultraviolet, UVA Number of pages 32 Date of submission 25/9/2018 ii h 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 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 ~ h TABLE OF CONTENTS LIST OF ABBREVIATIONS v LIST OF FIGURE vi PART INTRODUCTION 1.1 Research rationale .1 1.2 Research’s Objective 1.3 Research’s Contents 1.4 Research’s Scope PART LITERATURE REVIEW 2.1 Toluene 2.1.1 Toluene and its application 2.1.2 Toluene toxicity 2.2 TiO2 photocatalysis 2.2.1 Photocatalysis mechanism .8 2.2.2 TiO2 photocatalysts 2.3 Photocatalysis 16 2.4 UV absorption 17 PART 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 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 ~ h 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 ~ h 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~ h LIST OF FIGURE Figure Toluene chemical structure .4 Figure 2: Photo catalyst oxidation process Figure 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 ~ h PART 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~ h 1.3 Research’s Contents Literature review about toluene, its adverse effects on ecosystem and human health Synthesis and investigate the characteristics of materials to the degradation of toluene 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~ h Fe+3 solution: 0.5ml The molar ratio of Ferric Nitrate, 9-Hydrate to IPA is 1:5 IPA: 40ml Step 1: Apply IPA solution to the tube containing TiO2 powder Pump 0.5ml of Fe+3 solution into the tube Use an ultrasonic machine to separate the residue and solution within 10 minutes Step 2: Continue the tube on the contrifuge machine to allow the sediment to settle at 10000rpm for minutes Step 3: Put the dregs into the furnace at a temperature of 500 degrees Celsius for hours 3.2.2 Test the degradation rate of toluene by using samples of powder produced Prepare three petri dishes glass, each dish containing 0.3gram of powder For degradation test, the powder was put into a reactor then adding the same amount of toluene and using the same energy from the LED UVA Without any water inside the reactor which contained sample, the degradation of toluene happened fastest followed by the indoor gas And for humidified air with 100% of humid make the surface of photocatalyst contained much of water which leads to the absorption toluene take a long time than the two environments with less water This experiment was conducted at room temperature 3.2.4 Investigate the effective way to let the degradation process go faster Experiments designed to analyze the kinetics of toluene adsorption onto the selected Fe-TiO2 powder using filter paper The photocatalyst was synthesis in different amount of chemicals make different products ~ 19 ~ h By applying the same step as doping Fe into TiO2 but to get the most Fe-TiO2 powder, filter paper was used After doping Fe, the solution was poured onto the filter paper during using gravitational filtration Then put the finished product into the furnace overnight at 500 degree To examine the conditions affect the degradation process some factors is not change as: • Catalyst weight: 0.3g • Room temperature : 23 ~ 26 oC • Humidity : 17 % Figure 4: Photocatalyst was irradiated using UVA LED 370nm ~ 20 ~ h PART 4: RESULTS 4.1 Result of synthesis photocatalyst The photocatalyst was synthesis in different amount of chemicals make different products 4.1.1 Photocatalyst P25 Figure 5: Commercial photocatalyst P25 powder The powder has the milk white colour and smooth 4.1.2 Product of synthesized TiO2 Figure 6: TiO2 powder made in laboratory This product is pure white and has a little sparkle ~ 21 ~ h 4.1.3 Product of doped iron(Fe) Figure 7: Fe-TiO2 powder made in laboratory The powder was consumed has a little red colour from Fe doped 4.1 Results of photocatalyst by deposition Figure 8: Product of iron doping on TiO2 using filter paper By using filter paper, TiO2 doped Fe was synthesis with the best quality of powder ~ 22 ~ h 4.2 Results of different conditions To test the degradation of toluene, the light source has no change in three environmental conditions Concentration(ppm) 25 Dried Air 20 Humidified Air Indoor Gas 15 10 0 20 40 60 80 100 Time (min) Figure 9: Environment condition affect to the degradation of toluene Without any water inside the reactor which contained sample, the degradation of toluene happened fastest followed by the indoor gas And for humidified air with 100% of humid make the surface of photocatalyst contained much of water which leads to the absorption toluene take a long time than the two environments with less water To test the degradation of toluene, the light source has no change in three environmental conditions ~ 23 ~ h 4.3 Results of different light intensity For examining the light intensity could affect to the degradation, UVA LED was set up at first distance as 1.5cm and second distance as 2.5cm irradiation to the photocatalyst surface; there is no change in temperature and humidity Concentration (ppm) 25 20 st distance 1rd 15 2nd distance 10 0 10 20 30 40 50 60 70 Time (min) Figure 10: Light irradiation at different distance to the photocatalyst At the first distance, light intensity more focus on the surface of photocatalyst it make the toluene inside the reactor decreased faster than the light at the second distance and sorption equilibrium was established after 30 minutes 4.5 Results of different concentration To test the concentration has effect on degradation of toluene, the light intensity was set up at 1st distance; the condition of environment in 25-ppm, 50-ppm, 100-ppm, 200-ppm is the same as humidity at 17% and room temperature at 23°C ~ 24 ~ h Concentration(ppm) 120 100 25ppm 80 50ppm 60 100ppm 40 200ppm 20 0 20 40 60 80 100 120 140 160 Time (min) Figure 11: Different concentration degradation through the time As the decreased of concentration of toluene inside reactor, time for toluene degradation also decreased Based on data in Fig.11 The results of experiments are presented as a function of the different concentrations of toluene From Fig.11, it seen that as the concentration increased the removal efficiency of toluene decreased At 25ppm and 50ppm concentration of toluene, the tolunene degradation efficiency by the photocatalyst within hours Subsequently, by further increasing the concentration, the toluene degradation correspondingly increased The concentration higher takes longer time for degradation ~ 25 ~ h PART 5: Discussion and Conclusion 5.1 Discussion Titanium-dioxide had a wide band-gap semiconductor, with the main polymorphs (rutile, anatase, brookite) having measured band-gaps in the range 3.05– 3.18 eV The functional performance of TiO2 is fundamentally determined by its band structure, which is sensitive to crystal structure and changes to the stoichiometry or chemical identity of the constituent atoms Yamashita et al also studied the visible light activity of transition metal implanted TiO2 using XAFS analysis and theoretical calculations The substitution of Ti ions by isolated metal ions is the determining factor for the utilization of solar light Yamashita et al also studied the properties of Fe ion-implanted TiO2 The photochemical degradation of toluene under UV irradiation in the absence and presence of TiO2 was studied It can be asserted that the absence of TiO2 almost could not bring about the photo catalytic decomposition of toluene When added TiO2 into a reactor, the degradation rate become significant Light intensity effected: The UVA intensity has effect of on the photocatalytic efficiency of prepared catalysts was investigated by changing the position of UV source lamps The photo catalytic reaction in a photo reactor under UV irradiation conditions was successfully decomposed the toluene in the gas phase It was already studied a interaction effect when using TiO2 in the photo catalytic degradation of toluene For the decomposition of toluene, the rate of decomposition is almost independent of the initial toluene concentration This suggests that the catalyst coating ~ 26 ~ h increases the speed of UVA light transmission and promotes the contact between the surface of the catalyst and the catalyst, so toluene can be decomposed more efficiently over time shorter stay At higher toluene input concentrations, the decomposition rate decreases with increasing the initial toluene concentration due to the creation of more and more intermediate products, development and finish The results of experiments shows that, the decomposition of toluene increases by the UV intensity irradiated, and the photo catalytic efficiency with 1.5cm distance of lamp in all catalysts was more than the 2.5cm distance lamp So when UV light intensity higher the more photons generated, more photons participated in the photo catalytic reaction As the consequence, more OH• radicals with strong oxidizability were formed to decompose more toluene By increase in UV light intensity, toluene decomposition rate also increase Several suggestions have already been made for the likely photo catalytic oxidation methods (Carp et al., 2004; Zhang et al., 2007; Saquib et al., 2008) Surface oxidation may involve the transfer of photosynthetic electrons to adsorbed holes and holes created for organic molecules and subsequent interaction between ionic surface species (Amalric et al.,1994) It is generally accepted that the total degradation of organic molecules is favored by surface mechanisms in which the organic molecule reacts in the adsorbed phase (Aramendía et al., 2008) Other oxidation pathways could require OH radicals attack Generation of OH radicals via H2 O splitting or via O2 - intermediates has been previously suggested by many authors (Saquib et al., 2008) ~ 27 ~ h TiO2 sample, contain a high concentration of conduction electrons The presence of these charge carriers could favor the surface O2 reduction step to O2 - without help from photogeneration Maybe the adsorption of O2 competes with the adsorption of other molecules The dissociation of water on these samples is also possible Homogeneous pathways through OH radical attack could also occur in such cases Undoubtedly the nano TiO2 catalyst prepared in the laboratory showed good photocatalytic performance On the other hand, the operating parameters including initial toluene concentration and ultraviolet light intensity have great effects on toluene decomposition rate The results also showed that the degradation rate of toluene increased with increasing UVA light intensity 5.2 Conclusion In this study, three materials were characterized and used for degradation of toluene The following conclusions were based on the results obtained from the experiment: • Dopping ferric on TiO2 is better on degradated toluene because it preserves a higher degree of charge carriers and promotes charge utilization • Although the deposition is lighter than the coating, the effect is better Deposition can make the surface of photocatalyst uniform, that make the degradation go faster by irradiation • The time for toluene concentration to reach equilibrium state was around 20 minutes to 30 minutes • Light source at different distance has effect to the degradation The samples were irradiation with more light intensity make the degradation process become faster ~ 28 ~ h • The environmental condition also a factors has most impact on the degradation of toluene Inside the environment without appearances of water, the photo catalyst more active to absorb toluene than the environment has water or humidity ~ 29 ~ h REFERENCES Agrios, 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