京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22467号 / 工博第4728号 / 新制||工||1738(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 江口 浩一, 教授 佐藤 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The main aim of this thesis was to optimalise composition of the titanium dioxide with a silica binder deposited on a PET foil. Emphasis was put on achieving maximum possible adhesion and hardness of the layer and the effect on photocatalytic activity. For the evaluation of photocatalytic activity comparative experiments with prepared layers were performed. Benzoic acid, dimethyl sulfoxide and azo dye Acid Orange 7 were used as model pollutants. Photocatalytic activity was investigated using UV-VIS spectrophotometry, formal rate constants and degree of conversion were also determined. The study results can be used for removing water pollutants from the water solution.

Over the last several decades, there have been a tremendous developments and greatinnovations in photocatalysis process along with the development of efficient nanosized catalysts for simple approach and economic viability. In this study, magnetic core@doubleshell nanomaterials were investigated and synthesized in lab with three-step innovative approach where Fe3O4 nanoparticles (NPs) were produced first to act as cores without using any surfactants. The magnetite/silica core–shell structure was then prepared by hydrolysis of tetraethoxysilane (TEOS) in the presence of core particles under alkaline conditions. And the outermost shell, the α-Fe2O3/TiO2 nanoparticles, were grown over magnetic core of Fe3O4@SiO2 using coprecipitation and calcination method. Furthermore, the Fe3O4@SiO2@α-Fe2O3/TiO2 NPs were then loaded on the reduced graphene oxide (r-GO) using hydrothermal method and are also mixed by kneading with the layered double hydroxides (LDH) of Mg2+ and Al3+. These nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDS). Different model compounds like microcrystalline cellulose (90 μm), D-xylose, and sodium lignosulfonate representing cellulose, hemicellulose, and lignin, respectively, were converted to valuable chemicals with different NPs under visible light for different time periods. For example, valeric acid (VA) and vanillylmandelic acid (VMA) were produced when cellulose was used for the conversion with core-double shell NPS which were quantified using high performance liquid chromatography (HPLC). Similar approach was adopted for the conversion of brewers’ spent grain (BSG), a lignocellulosic biomass, without oxygen under visible light, which yielded ethanol as the main product along with other sugars and acids of very low concentrations. The magnetic property of the nanomaterials made it easy for recycle and reuse. From a sustainability point of view, this study will fill a large need in the biomass photocatalysis field by developing core-shell multi-functional photocatalysts for direct transformation of lignocellulose into valuable chemicals under low temperatures, atmospheric pressure, and visible light from the sun.

This thesis is focused on gathering all available information on the application forms of photocatalytic TiO2 in concretes, especially in the surface layers of precast and monolithic structures. The paper describes in detail the properties of titanium dioxide alone, his special abilities, leading to a substantial improvement of the environment, through photocatalysis. Further verification methods are described photocatalytic activity of titanium dioxide and titanium dioxide application in real projects. The practical part is tested recipes of secondary coatings from the production of company Precheza a.s. Přerov.

No description available.

This research work discusses the removal of organic pollutants specifically diclofenac and acid blue-25 using chalcogenide semiconductors. Semiconductors are materials that absorb light of specific energy and potentially degrade these organic pollutants into smaller compounds that are not toxic such as carbon dioxide and water. / Civil and Chemical Engineering

PhD (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Anaerobic digestion (AD) is usually applied in the treatment of distillery effluent due to the fact that it is effective in chemical oxygen demand (COD) reduction and bioenergy recovery. However, due to the presence of biorecalcitrant melanoidins present in distillery effluent, AD is ineffective in colour reduction. For this reason, ultraviolet (UV) photodegradation, which is effective in melanoidins’ degradation, can be integrated with AD to achieve high efficiency in colour and COD reduction. However, the UV process is energy intensive, majorly due to the electricity requirement of the UV lamp. In contrast, the AD process has high potential of renewable energy production in the form of biomethane, which can be transformed into electrical energy and applied to supplement the energy requirement of the UV process. The aim of this study was to evaluate the efficiency of a combined AD-UV system in colour and COD reduction for the treatment of distillery effluent in fluidised bed reactors. The potential of the application of the bioenergy produced by the AD process to supplement the energy intensive UV process was evaluated and modelled using response surface methodology. In the first place, the optimal hydrodynamic conditions of the fluidised bed reactors were determined using optical attenuation technique. The best homogeneity in the bioreactor, in which zeolite was used as microbial support, was found to be at a superficial liquid velocity of 0.6 cm/s while the best catalyst and gas hold up in the photoreactor were found to be 0.077 and 0.003, respectively. At these conditions, it was found that the initial biological step removed about 90% of COD and only about 50% of the colour while photodegradation post-treatment removed 98% of the remaining colour. Kinetic analysis of the bioreactor showed that ~ 9% of the feed total organic carbon (TOC) was non-biodegradable and this was attributed to the biorecalcitrant melanoidins. Photodegradation post-treatment mineralized the biorecalcitrant melanoidins via a reductive pathway as was indicated by the formation of NH4+ in large quantity compared to NO3-. Kinetic analysis further showed that the rate of substrate utilization in the bioreactor increased with an increase in organic loading rate and it was inversely proportional to the rate of photodegradation post-treatment. Modeling using response surface methodology (RSM) was applied to predict the effects of the operating parameters of the initial AD step on the performance of the photodegradation post-treatment process and the energy efficiency. Energy analysis of the integrated system showed that the AD process could produce 59 kWh/m3 of electricity which could supplement the electricity demand of the UV lamp by 30% leading to operation cost reduction of about USD 4.8/m3. This led to a presumed carbon dioxide emission reduction (CER) of 28.8 kg CO2e/m3.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21333号 / 理博第4429号 / 新制||理||1636(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺西 利治, 教授 倉田 博基, 教授 時任 宣博 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The development of nanoscale heterostructure photocatalysts for the effective, direct utilization of visible light (400-750 nm, ~44% of solar spectrum) to drive important chemical conversions is a prime research area in the field of photocatalysis. Particles at nanoscale dimensions have a large surface area-to-volume ratio, expose a high number of active surface sites, and exhibit unique electronic properties (different from bulk) that are beneficial for improving the overall catalytic activity. However, the advantages of size reduction are often overshadowed by the low optical absorption (as absorption power  size3) and colloidal instability (extensive aggregation) of particles at the nanoscale. In this dissertation, we demonstrate a strategy to improve the colloidal stability and enhance the optical absorption of nano-sized semiconductor and metal nanoparticles (NPs) that exhibit weak visible light absorption. The colloidal, free-standing NPs are placed on transparent, dielectric silica nanospheres (SiOx NSs) that act as optical antenna supports, forming SiOx/NP composite nanostructures. The spherical morphology of SiOx enables scattering resonances (Fabry Perot or Whispering Gallery Modes) which enhances the local electric field on or near the surface of the NS. The NPs placed on the surface of SiOx NS interact with the locally enhanced electric field and exhibit improved optical absorption. By varying the size of the SiOx NS, the resonance wavelengths and the intensity of the local electric field enhancement can be tuned, offering the ability of such structures to effectively utilize a wide range of energies in the visible region. Composite nanostructures comprised of various classes of nanomaterials such as metal-doped semiconductor, plasmonic, and non-plasmonic metal NPs were investigated to perform the desirable solar-to-chemical transformations. First, we employed SiOx-loaded silver-doped silver chloride (SiOx/AgCl(Ag)) photocatalyst to investigate the role of metal-induced gap states in AgCl, a wide bandgap semiconductor. SiOx/AgCl(Ag) exhibit high catalytic performance and photostability after 10 cycles of the probe reaction, methylene blue (MB) degradation under visible light irradiation. The results indicate that the visible light absorption due to metal-induced gap states can be further improved by employing the SiOx NSs as supports that act as optical nanoantenna. We then studied the influence of NP size on the catalytic activity to understand the effect of size in promoting the generation and transfer of hot electrons to surface adsorbates. Our findings indicate that upon employing Ag NPs of different particle size (<10 nm and >10 nm) and normalizing for the optical absorption and moles of surface Ag atoms, the efficient generation and transfer of photoexcited hot electrons is favored in the small-sized Ag NPs (size <10 nm) than bigger Ag NPs. Next, we investigated the selective partial hydrogenation of nitroarene to N-aryl hydroxylamine using SiOx-loaded platinum (SiOx/Pt) photocatalysts. We found that change in the surface electronic structure of the small Pt NPs (size <5 nm) due to light illumination and surface modification (by adding suitable organic ligands), minimize the adsorption of the electron-rich hydroxylamine molecules and minimize their complete conversion to aniline, resulting in high N-hydroxylamine selectivity. Overall, our work shows that well-controlled composite nanostructures comprising of active catalyst loaded on dielectric SiOx NS supports that act as optical nanoantenna are a promising class of photocatalysts for driving photon-to-chemical transformations with high activity and product selectivity. / Chemistry

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Petroleum wastewater is highly contaminated with toxic organic pollutants that are harmful to the environment. The heterogeneous photocatalytic oxidation (HPO) process has shown the ability to remove these pollutants through the application of a fluidized bed reactor (FBR). The purpose of the study was to apply response surface modelling (RSM) and computational fluid dynamics (CFD) to optimize the operating conditions for the photodegradation process in an FBR. This was done by investigating the hydrodynamics, photodegradation efficiency and reaction kinetics; that gave a holistic view on the performance of the FBR. The hydrodynamic study focused on modelling the axial liquid velocity, gas hold-up and turbulence quantities due to their substantial impact on the design and performance of the FBR. This was done by implementing the Eulerian-Eulerian approach which solves the continuity and momentum equations for each phase. In addition, the standard k-ε turbulence model was used to capture the turbulent characteristics in the liquid phase. A numerical optimization technique (desirability) was used to determine the optimal simulation setting methods; that were found to be a fine grid size (500 000 cells), 2nd Order Upwind discretization scheme and a small time step size (0.001) and gave the best desirability (0.985). The axial liquid velocity was maximal towards the centre of the reactor and decreased towards the wall. The same trend was seen with the local gas hold-up, where it was high towards the centre and low near the wall region. This was an indication that the bubbles tended to gather towards the central region as they move up. Furthermore, the bubbles had a spherical–like shape due to the low superficial gas velocity and operating within the homogeneous regime. The turbulent kinetic energy increased at distances away from the distributor region, due to the bubbles accelerating, and it balanced well with the energy introduced by the bubbles. Central composite design (CCD), which is a type of response surface modelling technique, was used to investigate and optimize the photodegradation operating parameters. The maximal degradation efficiency in the current study was found to be 65.9%, which was relatively low when compared to literature (80.84%). This was attributed to the increase in the catalyst particle size from nanometer to micrometer. Furthermore, the second-order empirical model that was developed, using the analysis of variance (ANOVA), presented a sufficient correlation to the photodegradation experimental data. The optimal photodegradation operating conditions were found to be: superficial gas velocity of 17.32 mm/s, composite catalyst loading of 1.0 g/L, initial pH level of 3.5 and reaction time being 210 min. Using the Langmuir-Hinshelwood model, it was found that the photocatalytic degradation of petroleum wastewater follows pseudo first-order reaction kinetics. Since the photocatalytic degradation mechanism of phenol follows three stages whereby the second stage is the photocatalytic degradation on the surface of the catalyst to form by-products. This is the rate dominant stage and follows the pseudo firstorder reaction kinetics.