Dissertations / Theses on the topic 'Water – Purification – Photocatalysis'

Although many aspects of the semiconductor photocatalysed mineralisation of water contaminants have been studied by researchers over the past decade, there are still certain areas which need further clarification, if the technique is to be used as an alternative to the presently available methods of water purification. It was the objective of the work in this thesis to provide further understanding of some of these remaining areas. One of the greatest inducements for the introduction of the technique of semiconductor photocatalysed pollutant mineralisation, in preference to the currently available technology, would be an efficiency advantage. The work in Chapter 3, studies the effect of many reaction variables (e.g. T, pH, [TiO₂]) in order to provide rate enhancements and therefore further efficiency of the technique. In Chapter 4 the model pollutant, 4-chlorophenol, is used to illustrate the role of activation energies in semiconductor photocatalysed mineralisation reactions, an area which has been largely ignored by researchers in this field to date. In order to speed up the process of reactor designs for commercial semiconductor photocatalysis reactors, there was a need for a predictive kinetic model, to provide information on individual pollutant mineralisation rates, under certain reaction conditions. Chapter 5 outlines a kinetic model which is able to accurately model the mineralisation of various pollutants and can also be used as a predictive tool for non-standard conditions. Chapter 6 enhances this work, to provide a model capable of modelling further pollutant systems, previously unable to be modelled. The technique of semiconductor photocatalysed pollutant mineralisation, will only become a plausible alternative to the currently available technology, if it can be scaled up from the batch reactor level. The work in Chapter 7 aims to provide scale up of the batch system used in Chapter 3 from 2.5 ml to 101.

As traditional disinfection techniques have proved to be inefficient in coping with toxic pollutants, there is a real need to create and develop alternatives such as Advanced Oxidation Processes (AOP's). As one of the most promising AOP's developed to date, heterogeneous semiconductor UV-photocatalysis has been shown to efficiently mineralise and inactivate a wide range of organic, inorganic and biological pollutants. This technique is based on the powerful redox properties of UV-illuminated semiconductors. The photocatalyst (semiconductor), which is insoluble in water, can be used in the form of a dispersion or as a thin coated film over which the pollutant can flow and interact in the liquid as well as in the gas phase. Although many pollutants have been studied, the development of more powerful analytical tools has meant that trace levels of water pollutants such as bromate, a potential carcinogenic by-product of the ozonation process and their destruction needs to be addressed. Chapters Three, Four and Five investigate the development and use of an analytical method for monitoring trace levels of bromate (ppb level or μg.dm^-3), in studies involving the use of Granular Activated Carbon (or GAC) and platinised TiO₂ (Pt-TiO₂) UV-photocatalysis for the removal of this inorganic pollutant. In Chapter Six, a study of TiO₂ photocatalysed oxidation of urea-based pesticides is given. Chapter Seven investigates two photoreactor designs for use in flow systems with larger volumes of pollutant which is required if the system is to be commercially viable. These flow photoreactors use thin immobilised films of TiO₂ over which the pollutant can flow. Finally, using the flow photoreactor designs studied in Chapter Seven, Chapter Eight presents a study of the photocatalysed oxidation of volatile organic pollutants (or VOC's) in the gas phase.

Thesis (PhD)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: The photo-mineralization of organic compounds (in the combined presence of a Ti02 based semiconductor catalyst, UV radiation and molecular oxygen) represents an advanced oxidation technology with significant potential for environmental pollution abatement. This oxidation process (generally known as photocatalytic oxidation - PCO) is currently the subject of extensive global research, with the main objective being the oxidative removal of organic and inorganic pollutants from water, air and soil. Presently, many barriers still block the way to commercial implementation of this technology, hence a unique (and effective) configuration of catalyst, light source and reactor design needs to identified. In terms of the water treatment scenario (which is the emphasis of this work) the need exists to develop a practical and affordable PCO reactor for water treatment on a large scale. The two laboratory-scale PCO reactors investigated in this work were based on a "falling film" flow reactor design and were constructed with commercially available materials and components. Degussa P-25 Ti02 was used as semiconductor catalyst and two types of low-pressure mercury lamps as the UV light source. Three modes of operation were investigated in order to determine the practical feasibility of the reactors. These included the recirculation, single pass and sequential single pass modes. The reactors were operated either as a Ti02 slurry-phase reactor (Reactor 1), or with Ti02 immobilized on stationary fiber glass and fibrous activated carbon sheet modules (Reactors 2A and 28 respectively). Extensive parametric evaluations were done using conventional one-factor variation and statistical methods according to optimal experimental design principles. The PCO treatment of two model organic pollutants (para-Chlorophenol and cyanobacterial microcystin YA, YR, LR and RR) were investigated. These pollutants were spiked into various water matrices to the desired concentration level. The combined photocatalyticcarbon adsorption treatment of these two pollutants was also investigated in Reactor 28. The experimental results obtained through this work showed that both model pollutants were successfully degraded in several water matrices by means of treatment in the respective PCO reactors. Moreover, this research was the first ever demonstration of the Ti02 photocatalytic degradation of microcystin toxins in the aqueous phase. The large number of parametric and optimization studies yielded the relative contributions of the various process parameters (in terms of the defined photocatalytic efficiency parameters as responses) very effectively. Furthermore, statistical evaluation of the experimental data provided valuable insight into the scientific phenomena associated with Ti02 mediated PCO processes.
AFRIKAANSE OPSOMMING: Die foto-mineralisasie van organiese verbindings (in die gekombineerde teenwoordigheid van 'n Ti02 gebaseerde halfgeleier katalisator, UV straling en molekulêre suurstof) verteenwoordig 'n gevorderde oksidasie-tegnologie met beduidende potensiaal vir bekamping van omgewingsbesoedeling. Hierdie oksidasie-proses (algemeen bekend as fotokatalitiese oksidasie - FKO) is tans wêreldwyd die onderwerp van ekstensiewe navorsing, met hoofdoel die oksidatiewe verwydering van organiese en anorganiese besoedelingstowwe uit water, lug en grond. Huidiglik bestaan daar nog vele struikelblokke wat die weg na kommersiële implementering van hierdie tegnologie blokkeer, gevolglik moet 'n unieke (en effektiewe) konfigurasie van katalisator, ligbron en reaktor-ontwerp nog identifiseer word. In terme van die waterbehandeling situasie (wat die klem van hierdie werk is) bestaan die nodigheid om 'n praktiese en bekostigbare FKO reaktor te ontwikkel vir watersuiwering op 'n groot skaal. Die twee laboratorium-skaal FKO reaktore in hierdie studie was gebaseer op 'n "vallende film" vloeireaktor ontwerp en is gekonstrueer met kommersieël beskikbare materiale en komponente. Degussa P-25 Ti02 is aangewend as halfgeleier katalisator en twee tipes lae-druk kwik lampe as die UV ligbron. Drie bedryfsmodes is ondersoek met die doel om die praktiese haalbaarheid van die reaktore te bepaal. Hierdie het ingesluit die resirkulasie, enkeldeurvloei en enkeldeurvloei-sekwensie modes. Die reaktore is bedryf as óf 'n Ti02 flodder-fase reaktor (Reaktor 1) óf met Ti02 ge-immobiliseer op 'n stasionêre veselglas en veselagtige ge-aktiveerde koolstof blad-modules (Reaktor 2A en 28 onderskeidelik). Omvattende parametriese evaluasies is gedoen deur gebruik te maak van konvensionele een-faktor variasie en statistiese metodes na aanleiding van optimale eksperimentele ontwerp beginsels. Die FKO behandeling van twee modelorganiese besoedelingstowwe (para-Chlorofenol en siano-bakteriese mikrosistien YA, YR, LR en RR) is ondersoek. Hierdie besoedelingstowwe is ge-ent in verskeie watermatrikse tot die verlangde konsentrasievlak. Die gekombineerde fotokatalitiese - aktiveerde koolstof behandeling van die twee besoedelingstowwe is ook ondersoek in Reaktor 28. Die eksperimentele resultate verkry deur hierdie werk het getoon dat beide die modelbesoedelingstowwe suksesvol gedegradeer is in verskeie watermatrikse deur behandeling in die onderskeie FKO reaktore. Trouens, hierdie navorsing was die eerste demonstrasie ooit van die Ti02 fotokatalitiese degradasie van mikrosistien toksiene in die waterige fase. Die groot aantal parametriese en optimiseringstudies het die bydraes van die verskeie proses-parameters (in terme van die gedefinieerde fotokatalitiese effektiwiteitsparameters as response) baie effektief verskaf. Verder, statistiese evaluasie van die eksperimentele data het waardevolle insig verskaf tot die wetenskaplike verskynsels te assosieer met Ti02 gemedieërde FKO prosesse.

This dissertation presents a method for enhancement of the efficiency and scalability of photocatalytic water purification systems, along with an experimental validation of the concept. A 3-dimensional photocatalyst structure, made from a TiO2-SiO2 composite, has been designed and fabricated for use in a custom designed LED-source illumination chamber of rotational symmetry that corresponds with the symmetry of the photocatalyst material. The design of the photocatalyst material has two defining characteristics: geometrical form and material composition. The design of the material was developed through the creation of a theoretical model for consideration of the system's photonic efficiency. Fabrication of the material was accomplished using a Ti alkoxide solution to coat a novel 3D support structure. The coatings were then heat treated to form a semiconducting thin-film. The resulting films were evaluated by SEM, TEM, UV-vis spectroscopy and Raman spectroscopy. The surface of the material was then modified by implantation of TiO2 and SiO2 nanoparticles in order to increase catalytic surface area and improve the photoactivity of the material, resulting in increased degradation performance by more than 500%. Finally, the efficiency of the photocatalytic reactor was considered with respect to energy usage as defined by the Electrical Energy per Order (EEO) characterization model. The effects of catalyst surface modification and UV-illumination intensity on the EEO value were measured and analyzed. The result of the modifications was an 81.9% reduction in energy usage. The lowest EEO achieved was 54 kWh per cubic meter of water for each order of magnitude reduction in pollutant concentration -- an improvement in EEO over previously reported thin-film based photoreactors.

Thesis (Masters of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, [2018].
Enhancing the efficiency of large scale photocatalytic systems has been a concern for decades. Engineering design and modelling for the successful application of laboratory-scale techniques to large scale is obligatory. Among the many fields of research in heterogeneous photocatalysis, photocatalytic reaction engineering can initiate improvement and application of conservative equations for the design and scale-up of photocatalytic reactors. Various reactor configurations were considered, and the geometry of choice was the annular shape. Theory supports the view that annular geometry, in the presence of constant transport flow properties, monochromatic light, and an incompressible flow, will allow a system to respect the law of conservation of mass. The degradation of a simulated dye, methyl orange (MO), by titanium dioxide (TiO2) with a simulated solar light (halogen lamp) in a continuous recirculating batch photoreactor (CRBPR) was studied. A response surface methodology (RSM) based on central composite design (CCD) was applied to study interaction terms and individual terms and the role they play in the photocatalytic degradation of MO. The studied terms were volume (L), TiO2 (g), 2 (mL), and initial dye concentration (mg/L), to optimize these parameters and to obtain their mutual interaction during a photocatalytic process, a 24 full-factorial CCD and RSM with an alpha set to 1.5 were employed. The polynomial models obtained for the chosen responses (% degradation and reaction rate constant, k) were shown to have a good externally studentized vs normal percentage probability fit with R2 values of 0.69 and 0.77 respectively. The two responses had a common significant interaction term which was the H2O2 initial dye concentration term. The optimum degradation that was obtained in this study was a volume of 20 L, TiO2 of 10 g, H2O2 of 200 mL and the initial dye concentration of 5 mg/L which yielded 64.6% and a reaction rate constant of 0.0020 min-1. The model of percentage degradation was validated on a yield of 50% and 80% over a series of set volumes and the model validation was successful.

The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated. During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes. Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition. As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health. Further investigation of the different TiO2 colloids was performed using in situ FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG.

The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated. During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes. Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition. As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health. Further investigation of the different TiO2 colloids was performed using in situ FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG.

Advanced oxidation processes are capable of removing organic compounds that cannot be removed by conventional water treatment methods. Among the oxidation processes, photo-catalysis using titanium dioxide (TiO2) is a promising method but suffers from rapid electron-hole recombination rates and only absorbs UV light which is a small percentage (5 percent) of the total solar radiation. Therefore there is a need to reduce the recombination rates and also extend the absorption of the photo-catalyst into the visible region which constitutes 55 percent of the total solar radiation. The major aims of this study were to prepare plasmon metal decorated and doped TiO2 photo-catalysts immobilized on quartz substrates and test their photo-catalytic and antimicrobial activities. The effect of film thickness (loading) and use of different shapes of plasmon metal nanostructures was investigated. TiO2 thin films were prepared by a sputter coating technique while plasmon metal (Au & Ag)/carbon co-doped TiO2 by a simple sol gel process and plasmon metal films were prepared by the thermal evaporation technique. Different plasmon metal nanostructures (nanorods, dendrites, nanowires and spherical nanoparticles) were prepared using a wet chemical technique using sodium borohydride as the reducing agent. Nanocomposites of co-doped TiO2 photo-catalyst and plasmon elements of different proportions were also prepared. The prepared photo-catalysts were coated onto etched and MPTMS (3-Mercaptopropyl trimethoxysliane) treated quartz glass substrate which is a stable support favouring easy recovery. The prepared materials were characterized by XRD, HRTEM, TEM, HRSEM, FT-IR, SEM, PIXE and TGA while the doped TiO2 was characterized by XPS, BET, CHNS and Raman Spectroscopy. The effect of pH of solution, presence of other contaminants and salts in solution, initial concentration of the model pollutant and type of the plasmonic elements on the photocatalytic activity of TiO2 towards 4-(4-sulfophenylazo)-N,N-dimethyl aniline (methyl orange) were also investigated. The selected TiO2 photo-catalyst films were tested for antimicrobial properties. The effect of different types of plasmon elements on the antimicrobial activity of TiO2 against E. coli ATCC 3695 was evaluated under both sunlight and weak UV light. Under UV light, Ag showed the highest enhancement in photo-catalytic activity of TiO2 than Au and Cu. The photo-catalytic activity of TiO2 increased with an increase in Ag content to an optimum loading and then started to decrease with a further increase in loading. For Cu and Au, photo-activity activity increased with an increase in plasmon metal content. Under sunlight, Cu showed the highest enhancement of TiO2 photocatalytic compared to Ag and Au. The change in order of deposition showed that Au films enhanced the photo-activity better when they were deposited underneath rather than on top of TiO2 on quartz supports but Ag films performed better in enhancing photo-activity when they were deposited on top of TiO2. The use of bimetallic layers and three layer systems of different plasmon elements enhanced photo-catalytic activity better than the use of a monometallic layer. The presence of other organic contaminants and salts in solutions was found to reduce the photo-degradation of methyl orange due to preferential adsorption of other contaminants. When the pH was increased, the photocatalytic activity of TiO2 towards methyl orange was reduced. In antimicrobial studies, it was found that the plasmon elements greatly improved the antibacterial action of TiO2 against Escherichia coli ATCC 3695 in water and the best antibacterial action was observed with silver/carbon co-doped TiO2 photo-catalyst under sunlight The doped samples consisted of polydisperse nanoparticles which were found to be beneficial for photo-catalytic activity enhancement under sunlight.

The thesis focuses on synthesis and characterization of nanocatalysts for applications in wastewater treatment and hydrogen production through electrochemical water splitting. Different photocatalysts and electrocatalysts are synthesized using wet chemistry techniques as well as Pulsed Laser Deposition (PLD). The synthesized catalysts pave demonstrate excellent catalytic activity thereby paving way for their use on an industrial scale.

Metal-Ethylenediaminetetraacetic acid (EDTA) complexes are found in a variety of industrial process. The stability of the formed complexes makes these compounds often inert to conventional wastewater treatment systems. In this work, the photocatalytic oxidation of NiEDTA was investigated as a means of breaking up the chelated nickel. The studied variables included the light intensity rate, the catalyst (TiO2), oxygen and NiEDTA concentrations. Photocatalytic experiments showed that increasing the catalyst concentration (0.5-3.0 g/L) decreases the light penetration inside the reactor resulting in a decrease in the reaction rate. The effect of oxygen and NiEDTA concentration was shown to exhibit Langmuir-Hinshelwood type kinetics. Total organic carbon (TOC) did not show any significant mineralization of NiEDTA for all investigated conditions. As a result, the by-products of the reaction were measured and found to include ED3A (ethylenediaminetriacetic acid), N-N'-EDDA (ethylenediamindiaacetic acid), IDA (iminodiacetic acid), oxalic acid, oxamic acid, glyoxylic acid, formaldehyde, ammonia, nitrate and nitrite. ED3A was found to be the major by-product of the reaction and nitrogen added from NiEDTA was found to be released as ammonia nitrogen. Oxygen consumption experiments were demonstrated as an effective way to monitor the rate of the reaction through measurement of the electron oxygen utilization rate. Nickel precipitation experiments showed that some of the by-products of NiEDTA degradation formed complexes with nickel. Finally, a light distribution model was generated using a CFD software (Fluent 6.1.22). For the catalyst concentration range of 0.5 to 3.0 g/L, this model showed that all of the light energy supplied by a centered UV lamp is absorbed within a one centimeter distance. Using the local volumetric rate of energy absorption (LVREA) calculated from the model the rate of the reaction was expressed in terms of quantum yield. For experiments carried out with air the quantum yield showed that the degradation rate was limited from an insufficient oxygen supply for electron scavenging. Increasing the oxygen concentration to 0.60 mmole O2/L increased the quantum yield for the highest light intensity rate; however the quantum yield never reached an optimum value thus indicating that other limiting conditions exist.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.

Three studies were performed to obtain fundamental mechanistic information on the TiO2 catalyzed photooxidations of organic substrates irradiated at 350 nm in dilute aqueous solutions under oxygenated conditions: (a) The photodecomposition of three haloethers, 2-chloroethyl ether, 4-chlorophenyl phenyl ether, and 4-bromophenyl phenyl ether, was investigated in an aqueous media at pH 7.0. (b) A comparative study of structure-reactivity was conducted on para-substituted phenols whose substituents range from electron-withdrawing to electron-donating in an aqueous media at pH 3.0. (c) The initial rates of the TiO2 catalyzed photodegratation of phenol were studied in an aqueous media at pH 1.0, 3.0, 5.0, 7.0, 9.0, 11.0, and 13.7 and a pH effect profile was obtained and compared to the removal efficiency after four hours of irradiation. Controls were carried out throughout the three studies in the absence of light and under anoxic conditions, as well as without the semiconductor to evaluate the role of photolysis. The Langmuir-Hinshelwood model was employed in an attempt to characterize and evaluate differences in reactivity.

Dans le contexte de la réduction de la ressource en eau potable à échelle mondiale, un intérêt croissant est porté au développement de technologies efficaces de purification de l'eau. Dans les travaux de cette thèse de doctorat, nous avons exploré le potentiel des micro- et nanotechnologies afin de proposer et évaluer deux méthodes de purification de l'eau, toutes deux entièrement autonomes en énergie et n'utilisant que l'énergie solaire pour leur mise en œuvre. La première méthode consiste en la génération de vapeur d'eau de façon accélérée grâce à la mise en œuvre d'une méta-mousse que nous avons conçus, dont nous avons modélisé et simulé le fonctionnement, puis optimisé pour la rendre la plus efficace en terme de quantité de vapeur générée par unité de temps et par unité de surface. En exploitant le silicium noir nanostructuré et en y rajoutant une micro-structuration bidimensionnelle contrôlée, unesérie de méta-mousses ont été réalisées et évaluées et les résultats ont montré une efficacité de conversion de 89% et une vitesse d'évaporation de 1,34 kg/(h·m2), ce qui représente une performance au-delà de l'état de l'art et proche de la limite théorique. La deuxième méthode est basée sur la photocatalyse. Elle se veut complémentaire de la première car elle permet de purifier les polluants résiduels volatils qui persistent après la mise en œuvre de la première méthode basée sur l'évaporation (et la condensation). Pour répondre aux exigences du traitement de l'eau à grande échelle, il y a deux points importants : L'un est la durabilité incluant la stabilité chimique du matériau photocatalyseur, en particulier dans des conditions extrêmes de pH de l'eau. L'autre est la facilité de synthèse de tels photocatalyseurs avec unenano-structure spécifiques. Sur la base de l'expérience du laboratoire en matière de croissance de nanofils (NWs) de ZnO, connu pour ses excellentes propriétés photocatalytiques, notre principale contribution dans cette thèse a consisté à le rendre plus durable et robuste aux environnements chimiques agressifs. A cet effet, nous avons proposé et évalué une combinaison de ZnO et de TiO 2 , tous deux ayant de hautes performances de dépollution. Cette combinaison a pour objectif de tirer profit des avantages respectifs des deux matériaux: la très bonne robustesse chimique du TiO 2 d'une part et la possibilité de synthétiser du ZnO sous forme de nanofils, donc avec une très grande surface spécifique. Il nous a semblé donc avantageux d'effectuer un revêtement de TiO 2 d'une épaisseur nanométrique sur des nanofils de ZnO (NW) après qu'un réseau homogène de ZnO NW ait été synthétisé. Cet assemblage original du tandem TiO 2 /ZnO nanostructuré a été caractérisé puis nous avons évalué sa durabilité et sa fonctionnalité de purification de l'eau. Notre solution s'est avérée efficace aussi bien dans dessolutions aqueuses fortement acides et fortement basiques. De plus, l'expérience de purification photocatalytique de l'eau des colorants organiques a été démontrée avec succès. Les résultats engrangés dans cette thèse offrent la perspective de valorisation en vue de la réalisation de systèmes de purification d'eau complètement autonomes et à bas coût
In the context of increasing global water scarcity, many efforts have been devoted to developing efficient water purification technologies. In this thesis work, two eco-friendly and promising approaches water purification approaches, surface-enhanced solar steam generation and photocatalysis, are studied to come out with a nano-enabled, fully self-consistent device that operates solely based on sunlight for delivering high-quality water.Surface-enhanced solar steam generation can be applied to purify insoluble and soluble water pollutants. It requires proper active photothermal material surface and optimized porosity to achieve high evaporation efficiency by localizing the heat at the water-air interface during solar steam generation. Herein, Taking the advantage of the characteristics of silicon that can be tailored to the target shape in the nanofabrication process and the high absorptivity of the black silicon, we report a bilayer black absorber sheet consisting of black silicon and commercial foam, being capable of providing superior performance in photothermal conversion, thermal insulation, and water imbibition simultaneously. The porosity of the foam is theoretically optimized by numerical modeling. Subsequent scanning electron microscopy and Fourier-transform infrared spectroscopy characterization and validated experiments revealed that the solar steam generation efficiency was increased to above 88% with the evaporation rate of 1.34 kg/(h·m2) under 1 sun illumination, a pioneering value compared with the state-of-the-art. In addition to insoluble and soluble water pollutants, there are some volatile organic water pollutants that cannot be eliminated by enhanced steam generation. Therefore, the photocatalysis water purification method is also studied, which proved to be effective in degrading organic water pollutants. To meet the requirement of large-scale water treatment, there are two important points: One is the lifetime and chemical stability of the photocatalyst material, especially in complex and harsh aqueous conditions. The other is the ease of synthesis of such photocatalysts with specific nano-morphology. In this thesis work, ZnO and TiO2 these two common photocatalysts are selected due to their high performance in degradation by producing the oxidative free radical after being illuminated by UV light. This involves the combination of both TiO2 and ZnO in a two-step si mple synthesis method. It appears advantageous to exploit the conformal deposition of atomic layer deposition (ALD) to achieve nanometer-thick TiO2 coating on ZnO nanowires (NWs) after a homogeneous ZnO NW array successfully grown using hydrothermal synthesis method with a high aspect ratio, which is firmly anchored to a substrate and exhibit a large specific surface area. After being characterized by energy-dispersive X-ray analysis via high resolution- scanning electron microscopy measurements, the high chemical stability of the ALD TiO2 coating has been investigated in detail and proven to be effective under both strong acid and strong alkaline aqueous solutions. In addition, the photocatalysis for water purification experiments with organic dyes shows that via this simple two-step synthesis method. Finally, it’s proved that the produced ZnO/TiO2 tandem does indeed exhibit improved chemical stability in a harsh environment while allowing efficient photodegradation

Water pollution is a major concern in vast countries such as India and other developing nations. Several methods of water purification have been practiced since many decades, Semiconductor photocatalysis is a promising technique, for photodegradation of various hazardous chemicals that are encountered in waste waters. The great significance of this technique is that, it can degrade (detoxify) various complex organic chemicals, which has not been addressed by several other methods of purification. This unique advantage made this field of research to attract many investigators particularly in latter eighties and after. This thesis incorporates the studies on the various semiconductor photocatalysts that have been employed for the detoxification purposes. The fundamental principles involved in the photoelectrochemistry, reactions at the interface (solid - liquid or solid - gas) and photocatalytic reactions on fine particles are briefed. General nature and size quantization in semiconductor particles, photocatalytically active semiconductors, TiCh and ABO3 systems, chemical systems and modifications for solar energy conversions are brought out in the introduction chapter besides giving brief description about photocatalytic mineralization of water pollutants with mechanism involved, formation of reactive species and the factors influencing photomineralization reactions. Scope of the present work is given at the end of the first chapter. Second chapter deals with the materials used for the preparation of photocatalyst, preparative techniques, methods of analysis, instruments employed for the photodegradation experiments and a brief description of material characterization methods such as X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis, optical absorption spectro photometry, Electron paramagnetic resonance (EPR), and gas chromatograph - mass spectroscopy (GC - MS). Various preparative routes such as wet chemical and hydrothermal methods for obtaining TiO2 (both rutile and anatase forms), BaTiOs and SrTiO3 fine particles and the chemical analysis of their constituents have been described in brief. Third chapter presents the results of materials characterization. T1O2 (rutile and anatase), BaTiO3 and SrTiO3 have been characterized separately using various techniques. Different routes of obtaining the photocatalyst fine particles, heat treatment at various temperature ranges, experimental procedures and the results of characterization are brought out in this chapter. Fourth and fifth chapters present the details of degradation studies carried out on the photomineralization of chlorophenol, trichloroethylene and formaldehyde. Studies include photodegradation of the pollutants with different catalysts varying experimental conditions to check the effects of change in concentration of pollutants, oxidizer, pH, surface hydroxylation, etc. The most favorable conditions for the complete mineralization of the pollutants have been studied. In case of TiO2, anatase form has shown greater photoactivity when compared to rutile and complete mineralization of chlorophenols has been achieved at low pollutant concentrations, neutral pH, with H2O2 and UV illumination. Retarding effects of surface hydroxylation and the formation of peroxotitanium species during photodegradation have been presented. TCE and HCHO degradation with BaTiO3/SrTiO3 has been studied. Photocatalyst heat-treated at 1100°G-1300°C is found to be highly active in combination with H2O2 as electron scavenger. HCHO is not getting degraded to its completeness in aqueous conditions owing to the strong competition in surface adsorption posed by H2O molecules. Vapour-solid phase reaction however gave good results in the detoxification of HCHO via disproportionation. Summary and conclusions are given at the end of the thesis.

This thesis is focused on developing metal-organic and organic molecules for photocatalytic water splitting and carbon dioxide reduction. In chapter 1, an overview of hydrogen production, dye-sensitized solar cells and carbon dioxide reduction are provided. The development history and reaction mechanisms of catalytic systems are introduced along with the typical examples in each field. The applications of both metal-organic and organic compounds are covered. In chapter 2, nine molecular organic photosensitizers were designed and synthesized. The nine molecules were employed as the photosensitizing reagent in the fabrication of dye-sensitized solar cells and applied in photocatalytic water reduction via coupling with TiO2 semiconductors and Pt co-catalyst. The highest turnover number (TON) of 10200 was achieved by organic photosensitizer 1g for hydrogen generation. The effect of alkyl chains and triarylamine donor moiety to the photocatalytic performance was investigated. A shorter alkyl chain was found to favor the reaction due to a lower hydrophobicity which in turn may block the interaction between the photocatalyst and water molecules. Besides, the triarylamine donor units facilitated high hydrogen generation rates by reducing the contact between catalytic active sites and the oxidized form of sacrificial reagents. In chapter 3, five earth-abundant metal complexes were synthesized to serve as the catalyst and CdS nanorods (NRs) were prepared to be the photosensitizer for the photocatalytic water reduction. A cobalt dithiolene complex (2a) achieved a TON of 30635 in 20 h under the blue light irradiation at a concentration of 10 µM. A new complex 2c also gave a high TON of 12375 under the same conditions and its TON was further improved to 115213 in 87 h by reducing the concentration of catalyst by ten times. The size effect of CdS NRs was investigated and larger nanoparticles exhibited higher hydrogen production rates. In chapter 4, ten iridium(III) complexes were synthesized and used as dual-functional molecules in photocatalytic carbon dioxide reduction by acting as both the photosensitizing reagent as well as the catalyst. The best performance was achieved by 3j, giving a TON of 230 under the irradiation of blue LED. A push-pull effect brought by trifluoromethyl and methoxy group sucessfully enhanced the carbon dioxide reduction efficiency. The hydrophobicity of n-butyl chain also provided effective protection to the active sites of reaction intermediate. Additional steric hindrance was found to extend the lifespan of photocatalytic systems but led to a drop in the overall conversion efficiency. Chapter 5 summarizes the specific synthetic procedures and characterization parameters of the molecules in chapters 2-4.

L’oxyde de zinc (ZnO) est un semi-conducteur II-VI remarquable et très prometteur dans le développement des nouveaux matériaux pour l’énergie renouvelable et pour l’environnement. ZnO est l’un des rares matériaux multifonctionnels. Grâce à ses nombreuses propriétés physiques, chimiques et optoélectroniques très intéressantes, lui confèrent d’être un matériau utilisé dans différents domaines d’applications telles que les cellules solaires, les diodes électroluminescentes, les capteurs de gaz, la dépollution de l’eau et de l’air par effet photocatalytique, etc.Dans cette thèse, nous nous sommes intéressés tout d’abords à optimiser l’élaboration de nanofils de ZnO (ZnO NWs) par méthode hydrothermale. Un procédé à deux étapes a été optimisé qui nous a permis d’obtenir des nanofils de ZnO ayant des excellentes propriétés morphologiques et structurales, avec une très bonne reproductibilité. Une nouvelle méthode d’élaboration, dite Electrospinning, a été mise au point. Ce procédé nous permet d’obtenir des micro- et nanofibres contenant des nanocristallites de ZnO. La combinaison des deux méthodes de synthèse nous a permis d’obtenir des nanostructures hiérarchiques de ZnO (NWs/NFs) possédant une surface effective beaucoup plus importante que la nanostructure classique (ZnO NWs).Deux applications ont été développées dans cette thèse. Dans un premier temps, des tests de détection de trois gaz réducteurs ont été réalisés sur les deux types de nanostructures de ZnO. Par la suite, une étude de purification de l’eau par effet photocatalytique a été réalisée sur un réseau de nanofils de ZnO sous irradiation UV pour les trois colorants (MB, MO et AR14). Afin d'améliorer la performance de la photocatalyse, deux nouvelles méthodes ont été développées. La première consiste à mettre en place un système microfluidique en utilisant des microréacteurs contenant des nanofils de ZnO comme photocatalyseur permettant ainsi à raccourcir considérablement le temps de dépollution. La seconde méthode est basée sur un procédé de dopage de ZnO permettant ainsi d’améliorer l'efficacité de la photocatalyse
Zinc oxide (ZnO) is a remarkable and very promising wide-gap II-VI semiconductor in the development of new materials for renewable energy and for the environment. Thanks to its many interesting physical, chemical and optoelectronic properties, this multifunctional material is used in many application fields such as solar cells, light emitting diodes, gas sensors, and water & air purification by photocatalytic effect, etc.In this thesis, we were interested in optimizing the synthesis of ZnO nanowires (ZnO NWs) by hydrothermal method. A two-step process has been optimized allowing us to obtain ZnO NWs having excellent morphological and structural properties, with very good reproducibility. A new synthesis method “Electrospinning” has been developed and the micro- & nanofibers containing ZnO nanocristallites can be obtained by this process. The combination of the two synthesis methods results a hierarchical nanostructure of ZnO (NWs/NFs) with an effective surface much larger than the classical one (ZnO NWs).Two applications have been developed in this thesis. Firstly, three reducing gases sensing tests have been carried out on the two types of ZnO nanostructures. Then, a photocatalytic water purification study has been carried out on a ZnO nanowire array under UV irradiation for the three dyes (MB, MO and AR14). In order to improve the photocatalysis performance, two new methods have been developed. The first is to set up a microfluidic system using microreactors containing ZnO NWs as a photocatalyst, thus the depollution time has been considerably shortened. The second method is based on the ZnO doping in order to improve the photocatalysis efficiency

Advanced water purification methods are required to answer the growing demand for clean water throughout the world. Current methods of removing the pollutants rely on moving the pollutants from one place to another rather than breaking them down. The use of advanced oxidative processes (AOPs) presents a highly effective opportunity to achieve the full mineralisation of pollutants without the added cost of regeneration methods. Photocatalysts, such as titanium dioxide and zinc oxide, can be used as AOPs when activated by electromagnetic radiation in the form of ultraviolet and visible light. To facilitate the activation with visible light, titanium dioxide doped with rare earth elements was produced via a sol gel method. Both single doped and co-doped systems were investigated with efficiency determined by the percentage of degraded methylene blue over 48 hours under ultraviolet filtered visible light. The incorporation of rare earth ions restricted the growth of the more active anatase phase and the method produced highly agglomerated, sintered nano particles which exhibited as micron sized particles. The highest methylene blue removal rate achieved in 48 hours for a single doped system was 70% for the 1 mol% yttrium doped titanium dioxide. This was improved further on inclusion of 1 mol% praseodymium which showed an 86% removal of methylene blue over the same time period. The coating of known up-converting phosphors with the successfully developed doped titanium dioxide was investigated. Yttrium silicate doped with praseodymium and lithium, was found to be the most successful known phosphor when used with the commercially available P25 titanium dioxide. When coated with the doped titanium dioxide shell at a 2:1 ratio of phosphor to titanium dioxide, a methylene blue degradation of 94% was reached. Initial tests on the coating of titanium dioxide with the known up-converting phosphor showed that methylene blue was absorbed rather than broken down so was not developed further. An investigation into the incorporation of zinc oxide, both pure and doped with the same successful titanium dioxide system was carried out. Zinc oxide shells were coated onto doped titanium dioxide, the known up-converting phosphor and the doped titanium dioxide coated known phosphor. The crystalline form of zinc oxide was inhibited by the incorporation of rare earth ions, as with the titanium dioxide system, and from the thickness of the zinc oxide shell. The highest degradation achieved was a 91% removal rate for the ZnO-PrY:TiO2-PrY:Y2SiO5-Pr,Li core shell shell structure indicating there was no further improvement on incorporation of zinc oxide, either doped or un-doped.

Even though titanium dioxide photocatalysis has been promoted as a leading green technology for water purification, many issues have hindered its application on a large commercial scale. For the materials scientist the main issues have centred the synthesis of more efficient materials and the investigation of degradation mechanisms; whereas for the engineers the main issues have been the development of appropriate models and the evaluation of intrinsic kinetics parameters that allow the scale up or re-design of efficient large-scale photocatalytic reactors. In order to obtain intrinsic kinetics parameters the reaction must be analysed and modelled considering the influence of the radiation field, pollutant concentrations and fluid dynamics. In this way, the obtained kinetic parameters are independent of the reactor size and configuration and can be subsequently used for scale-up purposes or for the development of entirely new reactor designs. This work investigates the intrinsic kinetics of phenol degradation over titania film due to the practicality of a fixed film configuration over a slurry. A flat plate reactor was designed in order to be able to control reaction parameters that include the UV irradiance, flow rates, pollutant concentration and temperature. Particular attention was paid to the investigation of the radiation field over the reactive surface and to the issue of mass transfer limited reactions. The ability of different emission models to describe the radiation field was investigated and compared to actinometric measurements. The RAD-LSI model was found to give the best predictions over the conditions tested. Mass transfer issues often limit fixed film reactors. The influence of this phenomenon was investigated with specifically planned sets of benzoic acid experiments and with the adoption of the stagnant film model. The phenol mass transfer coefficient in the system was calculated to be km,phenol=8.5815x10-7Re0.65(ms-1). The data obtained from a wide range of experimental conditions, together with an appropriate model of the system, has enabled determination of intrinsic kinetic parameters. The experiments were performed in four different irradiation levels (70.7, 57.9, 37.1 and 20.4 W m-2) and combined with three different initial phenol concentrations (20, 40 and 80 ppm) to give a wide range of final pollutant conversions (from 22% to 85%). The simple model adopted was able to fit the wide range of conditions with only four kinetic parameters; two reaction rate constants (one for phenol and one for the family of intermediates) and their corresponding adsorption constants. The intrinsic kinetic parameters values were defined as kph = 0.5226 mmol m-1 s-1 W-1, kI = 0.120 mmol m-1 s-1 W-1, Kph = 8.5 x 10-4 m3 mmol-1 and KI = 2.2 x 10-3 m3 mmol-1. The flat plate reactor allowed the investigation of the reaction under two different light configurations; liquid and substrate side illumination. The latter of particular interest for real world applications where light absorption due to turbidity and pollutants contained in the water stream to be treated could represent a significant issue. The two light configurations allowed the investigation of the effects of film thickness and the determination of the catalyst optimal thickness. The experimental investigation confirmed the predictions of a porous medium model developed to investigate the influence of diffusion, advection and photocatalytic phenomena inside the porous titania film, with the optimal thickness value individuated at 5 ìm. The model used the intrinsic kinetic parameters obtained from the flat plate reactor to predict the influence of thickness and transport phenomena on the final observed phenol conversion without using any correction factor; the excellent match between predictions and experimental results provided further proof of the quality of the parameters obtained with the proposed method.

Titanium dioxide nanoparticles were prepared using the sol-gel process. The effect of temperature and precursor concentration on particle size was investigated. The optimum conditions were then used to prepare carbon and nitrogen doped titanium dioxide (TiO2) nanoparticles. Doping was done to reduce band gap of the nanoparticles in order to utilize visible light in the photocatalytic degradation of organic compounds. A significant shift of the absorption edge to a longer wavelength (lower energy) from 420 nm to 456 nm and 420 nm to 428 nm was observed for the carbon doped and nitrogen doped TiO2 respectively. In this study, the prepared TiO2 photocatalyst was immobilized on carbon nanofibres to allow isolation and reuse of catalyst. The photocatalytic activity of the catalyst was tested using methyl orange as a model pollutant and was based on the decolourization of the dye as it was degraded. The doped TiO2 exhibited higher photocatalytic activity than the undoped TiO2. The materials prepared were characterized by XRD, TEM, SEM, FT-IR, DSC and TGA while the doped TiO2 was characterized by XPS, ESR and Raman Spectroscopy.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The purpose of this study was to develop modi ed tract-etched membranes using nanocomposite TiO2 for advanced water treatment processes. Photocatalytic oxidation and reduction reactions take place on TiO2 surfaces under UV light irradiation, therefore sunlight and even normal indoor lighting could be utilised to achieve this effect. In membrane ltration, caking is a major problem, by enhancing the anti-fouling properties of photocatalysts to mineralise organic compounds the membrane life and e ciency can be improved upon. In this study the rst approach in nanocomposite membrane development was to directly modify the surface of polyethylenetherephthalate (PET) track-etched membranes (TMs) with titanium dioxide (TiO2) using inverted cylindrical magnetron sputtering (ICMS) for TiO2 thin lm deposition. The second approach was rst to thermally evaporate silver (Ag) over the entire TM surface, followed by sputtering TiO2 over the silver-coated TM. As a result a noble metal-titania nanocomposite thin lm layer is produced on top of the TM surface with both self-cleaning and superhydrophilic properties. Reactive inverted cylindrical magnetron sputtering is a physical vapour deposition method, where material is separated from a target using high energy ions and then re-assimilated on a substrate to grow thin lms. Argon gas is introduced simultaneously into the deposition chamber along with O2 (the reactive gas) to form TiO2. The photocatalytic activity and other lm properties, such as crystallinity can be in uenced by changing the sputtering power, chamber pressure, target-to-substrate distance, substrate temperature, sputtering gas composition and ow rate. These characteristics make sputtering the perfect tool for the preparation of di erent kinds of TiO2 lms and nanostructures for photocatalysis. In this work, the utilisation of ICMS to prepare photocatalytic TiO2 thin lms deposited on track-etched membranes was studied in detail with emphasis on bandgap reduction and TM surface regeneration. Nanostructured TiO2 photocatalysts were prepared through template directed deposition on track-etched membrane substrates by exploiting the good qualities of ICMS. The TiO2-TM as well as Ag-TiO2-TM thin lms were thoroughly characterised. ICMS prepared TiO2 lms were shown to exhibit good photocatalytic activities. However, the nanocomposite Ag-TiO2 thin lms were identi ed to be a much better choice than TiO2 thin lms on their own. Finally a clear enhancement in the photocatalytic activity was achieved by forming the Ag-TiO2 nanocomposite TMs. This was evident from the band-gap improvement from 3.05 eV of the TiO2 thin lms to the 2.76 eV of the Ag-TiO2 thin lms as well as the superior surface regenerative properties of the Ag-TiO2-TMs.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om verbeterde baan-ge etste membrane (BMe) met behulp van nano-saamgestelde titaandioksied (TiO2) vir gevorderde water behandeling prosesse te ontwikkel. Fotokatalitiese oksidasie- en reduksie reaksies vind plaas op die TiO2 oppervlaktes onder UV-lig bestraling, en dus kan sonlig en selfs gewone binnenshuise beligting gebruik word om die gewenste uitwerking te verkry. In membraan ltrasie is die aanpaksel van onsuiwerhede 'n groot probleem, maar die verbetering van die self-reinigende eienskappe van fotokatalisators deur organiese verbindings te mineraliseer, kan die membraan se leeftyd en doeltre endheid verbeter word. In hierdie studie was die eerste benadering om nano-saamgestelde membraan ontwikkeling direk te verander deur die oppervlak van polyethylenetherephthalate (PET) BMe met 'n dun lagie TiO2 te bedek, met behulp van reaktiewe omgekeerde silindriese magnetron verstuiwing (OSMV).Die tweede benadering was eers om silwer (Ag) termies te verdamp oor die hele BM oppervlak, gevolg deur TiO2 verstuiwing bo-oor die silwer bedekte BM. As gevolg hiervan is 'n edelmetaal-titanium nano-saamgestelde dun lm laag gevorm bo-op die oppervlak van die BM, met beide self-reinigende en verhoogde hidro liese eienskappe. OSMV is 'n siese damp neerslag metode, waar materiaal van 'n teiken, met behulp van ho e-energie-ione, geskei word, en dan weer opgeneem word op 'n substraat om dun lms te vorm. Argon gas word gelyktydig in die neerslag kamer, saam met O2 (die reaktiewe gas), vrygestel om TiO2 te vorm. Die fotokatalitiese aktiwiteit en ander lm eienskappe, soos kristalliniteit, kan be nvloed word deur die verandering van byvoorbeeld die verstuiwingskrag, die druk in die reaksiekamer, teiken-tot-substraat afstand, substraattemperatuur, verstuiwing gassamestelling en vloeitempo. Hierdie eienskappe maak verstuiwing die ideale hulpmiddel vir die voorbereiding van die verskillende soorte TiO2 lms en nanostrukture vir fotokatalisasie. In hierdie tesis word OSMV gebruik ter voorbereiding van fotokatalitiese TiO2 dun lms, wat gedeponeer is op BMe. Hierdie lms word dan in diepte bestudeer, met die klem op bandgaping vermindering en BM oppervlak hergenerasie. Nanogestruktureerde TiO2 fotokataliste is voorberei deur middel van sjabloongerigte neerslag op BM substrate deur die ontginning van die goeie eienskappe van OSMV. Die TiO2-BM dun lms, sowel as Ag-TiO2-BM dun lms, is deeglik gekarakteriseer. OSMV voorbereide TiO2 dun lms toon goeie fotokatalitiese aktiwiteite. Nano-saamgestelde Ag-TiO2 dun lms is egter ge denti seer as 'n veel beter keuse as TiO2 dun lms. Ten slotte is 'n duidelike verbetering in die fotokatalitiese aktiwiteit bereik deur die vorming van die Ag-TiO2 nano-saamgestelde BMe. Dit was duidelik uit die bandgapingverbetering van 3,05 eV van TiO2 dun lms in vergelyking met die 2,76 eV van Ag-TiO2 dun lms. 'n Duidelike verbetering is behaal in die fotokatalitiese aktiwiteit deur die vorming van die Ag-TiO2 nano-saamgestelde TMs.

The integration of photocatalytic advanced oxidation into solar disinfection is a robust method of improving the microbial and chemical quality of treated water. This study evaluates the performance of photocatalytic solar irradiated batch reactors through an analytical model that reduces treatment parameters by simplifying photoreactor geometry and relating performance to reactor configuration. Accompanying experiments compare the performance of titanium dioxide coated foams of varying pore size to suspended and fixed film configurations through degradation of organic dyes (acid orange 24 and methylene blue), Escherichia coli, and 1,4-dioxane. Results indicate that a catalyst immobilized on a foam support can match the performance of a suspension due to effective mass transport and association between analyte and foam. Additionally, the potential treatment capacity of solar photocatalysis was compared to conventional treatment methods. Results of this comparison stress the fundamental limitation of solar photocatalysis if visible light wavelengths are not harnessed.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand in partial fulfilment of the requirement for the degree Master of Science (M.Sc.) in Chemistry. Johannesburg, 31 October 2017.
Nanotechnology has been instrumental in finding strategies of combating some of the world’s grand challenges. Water scarcity and the growing industrialization have made it an imperative to find ways of cleaning water. Photocatalysis is a promising method for water purification personified by the use of solar energy as well as nanomaterials with tailored properties. Colloidal synthesis has made it possible to synthesize new materials with tailored properties, in particular the single-source precursor method has been found to be a useful method in synthesizing nanomaterials with high purity. In the synthesis of metal chalcogenides, the single-source precursor method has an advantage of the precursor having the desired metal-chalcogenide bond hence eliminating the possible formation of side products particularly metal oxides. Herein, acylthiourea (ATU) and thiourea (TU) zinc complexes were used as precursors for the synthesis of ZnS nanoparticles. Bis(N,N-diethyl-N’-benzoylthiourea)Zn(II) [Zn(ATU)2] and bis(diaminomethylthio)Zn(II) chloride [Zn(TU)2Cl2] complexes were synthesized using a conventional method and characterized with elemental analysis, 1H NMR , 2D NMR, COSY, FTIR, mass spectrometry and X-Ray crystallography. The resultant precursors, Zn(ATU)2 and Zn(TU)2Cl2 complexes were then thermolyzed to yield ZnS nanocrystals and characterized fully. Reaction parameters that included the synthetic time, temperature, concentration and capping agents were optimized for each single-source precursor in an attempt to control the nanoparticles yielded hence their properties. Time and temperature studies generally demonstrated the most pronounced effect and with an increase, they showed increasing particle sizes through the Ostwald ripening effect. Also visible from the TEM was that the temperature had an effect on the morphology of the nanoparticles. Increasing the precursor concentration resulted in the agglomeration of nanoparticles, while using different capping agents yielded similar nanoparticles with different degrees of agglomeration. Evident from the results the ATU precursor behaved similar to the TU precursor and generally the particles obtained from the two precursors regardless of the reaction condition were very small. Preliminary investigations into the use of the synthesized nanoparticles obtained from the two precursors revealed potential in photocatalytic degradation of Rhodamine B (RhB) dye in water. While smaller particles were obtained from the synthesized nanoparticles, the degradation efficiencies were lower than the commercial ZnO and TiO2. This is due to the presence of the long-chained capping agents on the synthesized particles blocking the interaction of the core ZnS and the light.
LG2018

In this thesis, a feasible photocatalytic technology for water treatment was explored using a bottom-up approach in four separate research and developmental stages. These include (1) the synthesis, characterizations and photocatalytic activity (PCI) evaluation of a thin nanocrystals layer of titanium dioxide (TiO₂) immobilised onto modified mesoporous kaolin clay; (2) optimization and kinetics study of the photocatalytic reaction with recalcitrant organic dye Congo red (CR); (3) optimization and kinetics study of the photocatalytic disinfection with surrogate Escherichia coli and (4) assessment of a sequential batch reactor (SBR) mode for semi-continuous removal of dissolved pharmaceutical organic matters from secondary municipal wastewater. A modified two step sol-gel approach was used to immobilise layered of TiO₂ nanocrystals onto structurally stable kaolin (TiO₂-K) particles for enhanced physical properties. The TiO₂-K demonstrated a superior settling ability, adsorption capacity, PCI and stability compared to other conventional TiO₂ particles. Microscopic characterizations revealed that the modified kaolin provides a delaminated sandwich silica structure which minimizes chemical intercalation and further promotes high external surface area for heterocoagulation with microporous TiO₂ nanocrystals. Thermal regeneration cycles for the photocatalysts lifespan study examines that the PCI of TiO₂-K was improved over six treatment cycles, as a result of the change in average TiO₂ nanocrystals size and porosity. The real operational performances of the TiO₂-K photocatalysts for the organic degradation in water were investigated in a self-designed laboratory scale annular slurry photoreactor (ASP) system. The effect of key operational factors for the ASP system, such as TiO₂-K loading, pH, aeration rate and CR concentration were investigated. Results show that pH was the most significant factor that affects the adsorption and photocatalytic reactions in the ASP system. The point of zero charge (PZC) for the TiO₂-K particles was found to shift towards more basic extent of 9.5, resulting in a detrimental PCI when the ASP was operated at pH > PZC (TiO₂-K). The optimum operating conditions of the ASP was found to be 6.0 g L⁻¹ TiO₂-K loading, pH 7.0, 7.5 L min⁻¹ aeration rate and 40 mg L⁻¹ CR concentration. Under these optimum ASP conditions, the CR was completely photo-degraded in 4 h along with 80% reduction in chemical oxygen demand (COD) of the LC/MS-identified intermediates species. Owing to the lack of understanding and predictive in the singular optimum ASP condition, the Taguchi method was employed to collectively optimise the operating factor; determine the synergistic factor interactions and key influential factors, and further develop an empirical response surface model for the PCI prediction. From the Taguchi experiments, the photo-oxidation kinetics of CR exhibited saturation kinetics and thus, the Langmuir-Hinshelwood (L-H) model was applied. The Taguchi method predicted the optimum L-H apparent first order rate constant of 3.46 x 10⁻² min⁻¹ under the ASP operating conditions of 8.0 g L⁻¹ TiO₂-K, pH 5.0, 7.5 L min⁻¹ aeration rate and 40 mg L⁻¹ CR. Analysis of variance revealed that the CR concentration is the most significant factor, while pH appears to be the least significant one. The aeration rate in ASP was determined to have a significant synergistic effect on the TiO₂-K loading from the 3-D response surface plot. When the photo-oxidation of CR was referenced to the anatase titanate nanofiber (TNC) with PZC of 4.6, it was observed that the ASP operation was constrained by a narrow functional pH range. The optimum ASP operating conditions with slurry TNC were 4.0 g L⁻¹ TNC loading, pH 3.0, 5 L min⁻¹ aeration rate and 60 mg L⁻¹ CR, resulting in a degradation rate of 3.47 x 10⁻² mol L⁻¹ min⁻¹. Subsequent Taguchi analysis found that the low PZC (TNC) has a profound effect on the synergistic interaction with its loading concentrations. The 3D response plots showed that the low PZC (TNC) could be compensated with a high TNC loading at pH >PZC (TNC) and low aeration rate for optimal conditions. The Taguchi method predicted that the optimum ASP operating conditions were 6.0 g L⁻¹ TNC, pH 9, 5.0 L min⁻¹ aeration rate and 20 mg L⁻¹ CR. Analysis of variance shows that the pH, aeration rate and CR concentration were the significant factors, while TNC loading is the least significant one. The PCI for both photocatalysts were also tested against the photo-disinfection of Escherichia coli (ATCC 11775) as the surrogate indicator in the batch ASP system. In both investigations, the photocatalytic inactivation kinetics was found to exhibit non-linearity in the enumerated bacteria against irradiation time. The modified Hom model was used to fit a sigmoidal-shape bacterial survivor curve with strong shoulder and tailing characteristics. Using the TNC, the dissolved oxygen level in the open ASP system was found to be constantly replenished and further affects the photocatalytic inactivation kinetics. An L-H mechanistic model was proposed to determine oxygen transfer limitation in the photocatalytic disinfection process at different TNC loadings. A Fe²⁺ up to 1.0 mg L⁻¹ could initiate the residual disinfecting effect (RDE) of the photocatalytic reaction in the ASP, with constant dissociation of hydrogen peroxide (H₂O₂) to hydroxyl radicals (OH•). The RDE was diminished with increasing COD values. To effectively suppress the bacterial regrowth, the dissolved organic carbon should be well suppressed below 16 mg COD L⁻¹. Finally, the ASP system was operated as a SBR mode to allow semi-continuous treatment of the secondary municipal wastewater spiked with pharmaceutical Carbamazepine (CBZ) compound. A microfiltration module of 0.2 μm in porosity was fitted parallel to the reactor light source. The effects of key factors such as SBR cycles, nitrate (NO₃⁻), phosphate (PO₄³⁻), COD and photocatalysts on the effective photocatalytic CBZ removal were investigated. When the CBZ was degraded in the presence of high molecular weight effluent organic matter (EOM) in wastewater, the photocatalytic reaction appeared to have a preferential attack on the EOM that subsequently lower the degradation efficiency of CBZ. Other than this, the PO₄³⁻ in the wastewater showed a detrimental effect of photocatalyst fouling and deactivation on both TiO₂ catalysts used, resulting in a strong catalyst deactivation, and fouling of the catalysts. The deactivation and fouling are site specific and do not completely retard the photoactivity of the catalysts used. The sequential batch-annular slurry photoreactor (SB-ASP) was effectively operated up to two SBR cycles at catalyst loading (1 gL⁻¹) without any photocatalyst replacement, as the semi-continuous operation allows simultaneous water discharge and UV photocatalyst reactivation phase.
Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2010

So, Wai Man.
Thesis submitted in: October 2007.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves 112-124).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstract --- p.ii
Table of Contents --- p.vi
List of Figures --- p.x
List of Plates --- p.viii
List of Tables X --- p.v
Abbreviations --- p.xvii
Equations --- p.xix
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Importance of water disinfection --- p.1
Chapter 1.2 --- Conventional disinfection methods --- p.2
Chapter 1.2.1 --- Chlorination --- p.2
Chapter 1.2.2 --- Ozonation --- p.3
Chapter 1.2.3 --- Ultraviolet-C (UV-C) irradiation --- p.4
Chapter 1.2.4 --- Sunlight irradiation --- p.5
Chapter 1.2.5 --- Others --- p.6
Chapter 1.3 --- Photocatalytic oxidation --- p.7
Chapter 1.3.1 --- Reactions in PCO --- p.8
Chapter 1.3.2 --- Disinfection mechanism of PCO --- p.11
Chapter 1.3.3 --- Photocatalysts --- p.14
Chapter 1.3.3.1 --- Titanium dioxide (TiO2) --- p.14
Chapter 1.3.3.2 --- Modification of TiO2 --- p.15
Chapter 1.3.3.2.1 --- Sulphur cation-doped TiO2 (S-TiO2) --- p.17
Chapter 1.3.3.2.2 --- Copper(I) oxide-sensitized P-25 (Cu20/P-25) --- p.18
Chapter 1.3.3.2.3 --- Silicon dioxide-doped TiO2 (SiO2-TiO2) --- p.18
Chapter 1.3.3.2.4 --- Nitrogen-doped TiO2 (N-TiO2) --- p.19
Chapter 1.4 --- Bacterial defense systems against oxidative stress --- p.20
Chapter 1.5 --- Bacterial species --- p.22
Chapter 1.5.1 --- Salmonella typhimurium --- p.23
Chapter 1.5.2 --- Klebsiella pneumoniae --- p.24
Chapter 1.5.3 --- Bacillus thuringiensis --- p.25
Chapter 1.5.3 --- Bacillus pasteurii --- p.26
Chapter 2. --- Objectives --- p.27
Chapter 3. --- Material and Methods --- p.28
Chapter 3.1 --- Culture media and diluents --- p.28
Chapter 3.2 --- Screening of target bacteria --- p.28
Chapter 3.3 --- PCO disinfection reaction --- p.29
Chapter 3.3.1 --- Photocatalysts --- p.29
Chapter 3.3.2 --- Bacterial cultures --- p.31
Chapter 3.3.3 --- PCO reactor --- p.32
Chapter 3.3.4 --- PCO efficacy test --- p.34
Chapter 3.3.5 --- Comparison of different photocatalysts --- p.35
Chapter 3.4 --- Optimization of PCO disinfection conditions --- p.35
Chapter 3.5 --- Transmission electron microscopy (TEM) --- p.39
Chapter 3.6 --- Superoxide dismutase (SOD) activity assay --- p.42
Chapter 3.7 --- Catalase (CAT) activity assay --- p.44
Chapter 3.8 --- Spore staining --- p.45
Chapter 3.9 --- Atomic absorption spectrophotometry (AAS) --- p.45
Chapter 3.10 --- X-ray photoelectron spectrometry (XPS) --- p.46
Chapter 4. --- Results --- p.47
Chapter 4.1 --- Screening of wastewater bacteria --- p.47
Chapter 4.2 --- PCO efficacy test --- p.49
Chapter 4.3 --- PCO under visible light irradiation --- p.53
Chapter 4.3.1 --- Fluorescence lamps with UV filter --- p.53
Chapter 4.3.2 --- Solar lamp with UV filter --- p.61
Chapter 4.3.3 --- Sunlight with UV filter --- p.67
Chapter 4.4 --- Optimization of PCO disinfection conditions --- p.75
Chapter 4.4.1 --- Effect of visible light intensities --- p.75
Chapter 4.4.2 --- Effect of photocatalyst concentrations --- p.77
Chapter 4.4.3 --- Optimized conditions --- p.79
Chapter 4.5 --- Transmission electron microscopy (TEM) --- p.79
Chapter 4.6 --- Superoxide dismutase (SOD) activity assay --- p.83
Chapter 4.7 --- Catalase (CAT) activity assay --- p.84
Chapter 4.8 --- Spore staining --- p.85
Chapter 4.9 --- Studies on Cu20/P-25 --- p.88
Chapter 4.9.1 --- Atomic absorption spectrophotometry (AAS) --- p.88
Chapter 4.9.2 --- X-ray photoelectron spectrometry (XPS) --- p.88
Chapter 5. --- Discussion --- p.90
Chapter 5.1 --- Screening of wastewater bacteria --- p.90
Chapter 5.2 --- PCO efficacy test --- p.90
Chapter 5.3 --- Comparison between different light sources --- p.90
Chapter 5.4 --- Comparison between different photocatalysts --- p.93
Chapter 5.5 --- Optimization of PCO disinfection conditions --- p.95
Chapter 5.5.1 --- Effect of visible light intensities --- p.95
Chapter 5.5.2 --- Effect of photocatalyst concentrations --- p.96
Chapter 5.6 --- Transmission electron microscopy (TEM) --- p.97
Chapter 5.7 --- Comparison between different bacterial species --- p.99
Chapter 5.8 --- Possible factors affecting susceptibility of bacteria towards PCO --- p.99
Chapter 5.8.1 --- Formation of endospores --- p.99
Chapter 5.8.2 --- Differences in cell wall structure --- p.100
Chapter 5.8.3 --- SOD and CAT activities --- p.101
Chapter 5.9 --- Dark control of Cu20/P-25 --- p.103
Chapter 5.10 --- Studies on Cu20/P-25 --- p.104
Chapter 6. --- Conclusion --- p.107
Chapter 7. --- References --- p.112
Chapter 8. --- Appendix --- p.125
Chapter 8.1 --- Production of S-Ti02 --- p.125
Chapter 8.2 --- Production of Si02-Ti02 --- p.125
Chapter 8.3 --- Production of N-Ti02 --- p.125

在過去的幾十年中，人們越來越關心由致病微生物引起的水傳播疾病的爆發。作為一種綠色技術，太陽能光催化在不引起二次污染的殺滅各種致病微生物方面引起了廣泛關注。但是，目前最廣泛應用的TiO₂光催化劑僅在紫外光激發範圍內有效，而紫外光僅占太陽光譜的4%。因為太陽光譜中有45%是可見光，所以新型可見光催化劑的開發是現今光催化技術亟待解決的問題。另一方面，目前對於光催化殺菌機理的研究報導非常稀少而且主要集中于紫外-TiO₂光催化系統中，而對於可見光催化系統中的殺菌機理研究還鮮有報導。
本研究介紹三種新型可見光催化劑的殺菌性能。它們是B,Ni共摻TiO₂微米球（BNT），BiVO₄納米管（BV-NT）和CdIn₂S₄微米球（CIS）。其中一種是修飾的TiO₂催化劑，另兩種是新型的非TiO₂基催化劑。採用加入各種湮滅劑結合一種分離裝置的研究方法系統研究了三種催化劑的可見光殺菌機理。首先，研究發現當用BNT作為光催化劑的時候，可見光催化降解染料和殺菌之間存在巨大的差異。對於光催化降解染料，光催化反應主要發生在催化劑的表面，是由表面活性物質如h⁺, ・OHs和・O₂⁻參與，而細菌可以被擴散物種如・OH[subscript b]和H₂O₂，以不直接接觸催化劑表面的方式被殺死。可擴散的H₂O₂在這種殺菌過程中起了最重要的作用，而它可以在催化劑價帶以・OH[subscript b]溶液體相耦合和・OH[subscript s]催化劑表面耦合兩種方式產生。
其次，在用BV-NT作為光催化劑可見光殺滅大腸桿菌的過程中，光生空穴（h⁺）以及由空穴產生的氧化物種，如・OH[subscript s], H₂O₂和・HO₂/・O₂⁻，是主要的活性物種。但是這個殺菌過程只有很少量的H₂O₂可以擴散到溶液中，導致有效殺菌需要細菌和光催化表面直接接觸。研究還發現，細菌本身可以捕獲光生電子（e⁻）來降低空穴-電子複合率，這個作用在無氧氣參與的殺菌過程中尤為明顯。透射電鏡顯示，細菌的破壞是由細胞壁開始從外到內的被破壞。研究認為，表面羥基・OH[subscript s]比溶液體相羥基・OH[subscript b]更加重要，並且很難從BV-NT表面擴散進容易中。
最後，研究還發現CIS也具有不接觸細菌而有效可見光催化殺滅大腸桿菌的能力，這也歸結為可擴散H₂O₂，而不是・OH的作用。H₂O₂可以通過・O₂⁻從催化劑導帶和價帶同時產生。本研究提供了幾種具有應用前景的高效可見光催化殺菌催化劑，並對其光催化機理提出了新的思路，指出可見光催化殺菌機理與使用的光催化劑是密切相關的。更重要的是，本研究建立了一種簡便易行的研究方法，可用於對其他各種可見光催化殺菌系統進行深入的機理研究。
During the last few decades, there has been an increasing public concern related to the outbreak of waterborne diseases caused by pathogenic microorganisms. As a green technology, solar photocatalysis has attracted much attention for the disinfection of various microorganisms without secondary pollution. However, the most commonly used TiO₂ photocatalyst is only active under UV irradiation which accounts for only 4% of the solar spectrum. Therefore, new types of photocatalysts that can be excited by visible light (VL) are highly needed, as 45% of the solar spectrum is covered by VL. In addition, existing reports on the mechanisms of photocatalytic bacterial disinfection are rather limited and mostly based on TiO₂-UV irradiated systems, thus the mechanisms in visible-light-driven (VLD) photocatalystic disinfection systems are far from fully understandable.
In this study, three different kinds of VLD photocatalysts were discovered for the photocatalytic bacterial disinfection. They were B-Ni-codoped TiO₂ microsphere (BNT), bismuth vanadate nanotube (BV-NT), and cadmium indium sulfide (CIS). One was modified TiO₂-based photocatalyst, and the other two were new types of non-TiO₂ based photocatalyst. The mechanisms of VLD photocatalytic disinfection were investigated by multiple scavenging studies combined with a partition system. Firstly, significant differences between VLD photocatalytic dye decolorization and bacterial disinfection were found in the case of BNT as the photocatalyst. For photocatalytic dye decolorization, the reaction mainly occurred on the photocatalyst surface with the aid of surface-bounded reactive species (h⁺, ・OH[subscript s] and ・O₂⁻), while bacterial cell could be inactivated by diffusing reactive oxidative species such as ・OH[subscript b] and H₂O₂ without the direct contact with the photocatalyst. The diffusing H₂O₂ played the most important role in the photocatalytic disinfection, which could be produced both by the coupling of ・OH[subscript b] in bulk solution and ・OH[subscript s] on the surface of photocatalyst at the valence band.
Secondly, when using BV-NT as the photocatalyst for Escherichia coli K-12 inactivation, the photogenerated h⁺ and reactive oxidative species derived from h⁺, such as ・OH[subscript s], H₂O₂ and ・HO₂/・O₂⁻, were the major reactive species. However, the inactivation requires close contact between the BV-NT and bacterial cells, as only a limited amount of H₂O₂ can diffuse into the solution to cause the inactivation. The bacterial cells can trap e⁻ in order to minimize e⁻-h⁺ recombination, especially under anaerobic condition. Transmission electron microscopic study indicated the destruction process of bacterial cell began from the cell wall to other cellular components. The ・OH[subscript s] was postulated to be more important than ・OH[subscript b] and was not supposed to be released very easily from BV-NT surface.
Finally, it was found that E. coli cells could be effectively inactivated without the direct contact with CIS, which was attributed to the function of diffusing H₂O₂ rather than ・OH. H₂O₂ was produced from both conduction and valance bands with the involvement of ・O₂⁻, which were detected by ESR spin-trap with DMPO trapping technology. While this study provided promising candidates of efficient VLD photocatalysts for water disinfection as well as deep insights into the disinfection mechanisms, it was notable that the photocatalytic disinfection mechanisms were quite dependent on the selected photocatalysts. Nevertheless, the research methodology established in this study was proved to be facile and versatile for the in-depth investigation of mechanisms in different VLD photocatalyst systems.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Wang, Wanjun.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 140-170).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Acknowledgements --- p.i
Abstract --- p.vi
List of Figures --- p.xvi
List of Plates --- p.xxiii
List of Tables --- p.xxiv
List of Equations --- p.xxv
Abbreviations --- p.xxvii
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Water disinfection --- p.1
Chapter 1.2 --- Traditional water disinfection methods --- p.2
Chapter 1.2.1 --- Chlorination --- p.2
Chapter 1.2.2 --- Ozonation --- p.3
Chapter 1.2.3 --- UV irradiation --- p.4
Chapter 1.3 --- Advanced oxidation process --- p.5
Chapter 1.4 --- Photocatalysis --- p.6
Chapter 1.4.1 --- Fundamental mechanism for TiO₂ photocatalysis --- p.7
Chapter 1.4.2 --- Photocatalytic water disinfection --- p.12
Chapter 1.5 --- Visible-light-driven photocatalysts for water disinfection --- p.16
Chapter 1.5.1 --- Modified TiO₂ photocatalysts --- p.16
Chapter 1.5.1.1 --- Surface modication of TiO₂ by noble metals --- p.16
Chapter 1.5.1.2 --- Ion doped TiO₂ --- p.18
Chapter 1.5.1.3 --- Dye-sensitized TiO₂ --- p.19
Chapter 1.5.1.4 --- Composite TiO₂ --- p.20
Chapter 1.5.2 --- Non-TiO₂ based photocatalysts --- p.22
Chapter 1.5.2.1 --- Metal oxides --- p.22
Chapter 1.5.2.2 --- Metal sulfides --- p.24
Chapter 1.5.2.3 --- Bismuth metallates --- p.25
Chapter 1.6 --- Photocatalystic disinfection mechanisms --- p.27
Chapter 2 --- Objectives --- p.30
Chapter 3 --- Comparative Study of Visible-light-driven Photocatalytic Mechanisms of Dye Decolorization and Bacterial Disinfection by B-Ni-codoped TiO₂ Microspheres --- p.32
Chapter 3.1 --- Introduction --- p.32
Chapter 3.2 --- Experimental --- p.35
Chapter 3.2.1 --- Materials --- p.35
Chapter 3.2.2 --- Characterizations --- p.36
Chapter 3.2.3 --- Photocatalytic decolorization of RhB --- p.36
Chapter 3.2.4 --- Photocatalytic disinfection of E. coli K-12 --- p.37
Chapter 3.2.5 --- Partition system --- p.40
Chapter 3.2.6 --- Scavenging study --- p.41
Chapter 3.2.7 --- Analysis of ・OH and ・O₂⁻ --- p.42
Chapter 3.2.8 --- Analysis of H₂O₂ --- p.43
Chapter 3.3 --- Results and Discussion --- p.44
Chapter 3.3.1 --- XRD and SEM images --- p.44
Chapter 3.3.2 --- Photocatalytic decolorization of RhB --- p.46
Chapter 3.3.2.1 --- Role of reactive species --- p.46
Chapter 3.3.2.2 --- Partition system for dye decolorization --- p.49
Chapter 3.3.3 --- Photocatalytic bacterial disinfection --- p.51
Chapter 3.3.3.1 --- Role of reactive species --- p.51
Chapter 3.3.3.2 --- Partition system for bacterial disinfection --- p.54
Chapter 3.3.3.3 --- pH effects --- p.58
Chapter 3.3.3.4 --- Role of H₂O₂ --- p.60
Chapter 3.3.4 --- Role of ・O₂⁻ in RhB decolorization and bacterial disinfection --- p.67
Chapter 3.4 --- Conclusions --- p.75
Chapter 4. --- Visible-light-driven Photocatalytic Inactivation of E. coli K-12 by Bismuth Vanadate Nanotubes: Bactericidal Performance and Mechanism --- p.76
Chapter 4.1 --- Introduction --- p.76
Chapter 4.2 --- Experimental --- p.78
Chapter 4.2.1 --- Materials --- p.78
Chapter 4.2.2 --- Photocatalytic bacterial inactivation --- p.80
Chapter 4.2.3 --- Bacterial regrowth ability test --- p.82
Chapter 4.2.4 --- Analysis of reactive species --- p.82
Chapter 4.2.5 --- Preparation procedure for bacterial TEM study --- p.83
Chapter 4.2.6 --- Analysis of bacterial catalase activity --- p.84
Chapter 4.2.7 --- Analysis of potassium ion leakage --- p.84
Chapter 4.3 --- Results and Discussion --- p.85
Chapter 4.3.1 --- Photocatalytic bacterial inactivation --- p.85
Chapter 4.3.2 --- Mechanism of photocatalytic inactivation --- p.87
Chapter 4.3.2.1 --- Role of primary reactive species --- p.87
Chapter 4.3.2.2 --- Role of direct contact effect --- p.96
Chapter 4.3.3 --- Destruction model of bacterial cells --- p.98
Chapter 4.3.4 --- Analysis of radical production --- p.104
Chapter 4.4 --- Conclusions --- p.109
Chapter 5 --- CdIn₂S₄ Microsphere as an Efficient Visible-light-driven Photocatalyst for Bacterial Inactivation: Synthesis, Characterizations and Photocatalytic Inactivation Mechanisms --- p.111
Chapter 5.1 --- Introduction --- p.111
Chapter 5.2 --- Experimental --- p.113
Chapter 5.2.1 --- Synthesis --- p.113
Chapter 5.2.2 --- Characterizations --- p.114
Chapter 5.2.3 --- Photocatalytic bacterial inactivation --- p.116
Chapter 5.3 --- Results and Discussion --- p.117
Chapter 5.3.1 --- Characterizations of Photocatalyst --- p.117
Chapter 5.3.2 --- Photocatalytic bacterial inactivation and mechanism --- p.121
Chapter 5.3.3 --- Destruction process of bacterial cell --- p.128
Chapter 5.3.4 --- Analysis of radical generation --- p.131
Chapter 5.4 --- Conclusions --- p.133
Chapter 6 --- General Conclusions --- p.135
Chapter 7 --- References --- p.140

Monodisperse titanium dioxide (TiO2) nanoparticles were synthesized by a novel freeze-drying process herein called lyophilization. The process of lyophilization is described in detail. The materials were characterized by scanning electron microscopy SEM) including energy dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Raman spectroscopy and UV-Vis-IR spectrophotometry. The TiO2 nanoparticles have narrow size distribution, mono-disperse, strained with most of the characteristics showing presence of the four phases of TiO2 thus: anatase, brookite, rutile with each lyophilization process producing its own phase mostly controlled by pH and precursor concentration and anneal/calcining temperatures. With specific reference to HRTEM, Raman spectroscopy results and XRD, it was found that the Scherrer equation, the Williamson-Hall method and others of similar nature were not enough to explain the strain and the grain sizes of these particles. Therefore the Williamson-Hall method was revised to properly explain the new results. The obtained TiO2 nanoparticles were used in three applications: (1) gas sensing (2) degradation of organic water-borne pollutants using methylene blue as an indicator (3) anti-bacterial activity.
Physics
D. Phil. Physics)

PhD. (Chemistry)
Pre-synthesised gadolinium oxide decorated multiwalled carbon nanotubes (MWCNT-Gd) were coupled with titania to form nanocomposite photocatalysts (MWCNT-Gd/TiO2) using a sol-gel method. Rare earth metal ions (Eu, Nd and Gd), nitrogen and sulphur tridoped titania were decorated on MWCNT-Gd to yield composite photocatalysts (MWCNT-Gd/Eu/Nd/Gd/N,S-TiO2) by a similar method, using thiourea as nitrogen and sulphur source. Different carbon nanomaterials were incorporated into tridoped titania to form various composite photocatalysts (MWCNT/Gd,N,S-TiO2, MWCNT/Nd,N,S-TiO2, SWCNT (single walled carbon nanotube)/Nd,N,S-TiO2 and rGO (reduced graphene oxide)/Nd,N,S-TiO2) via the sol-gel method. Likewise, gadolinium doped graphitic carbon nitride (g-C3N4-Gd3+) was obtained by heating a mixture of gadolinium nitrate hexahydrate and cyanoguanidine and subsequently hybridised with MWCNT/TiO2 using the sol-gel method to yield composite photocatalysts with varying g-C3N4-Gd3+ loadings. All the prepared photocatalysts were characterised by microscopic tools (FE/FIB-SEM-EDX, TEM), crystallographic technique (XRD), spectroscopic tools (UV-Vis, Raman and FT-IR) and nitrogen sorption technique (BET).

Chen, Yanmin.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (leaves 140-160).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

Leung, Tsz Yan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves 132-146).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstract --- p.ii
Table of Contents --- p.vii
List of Figures --- p.xii
List of Plates --- p.xiv
List of Tables --- p.xvii
Abbreviations --- p.xviii
Equations --- p.xxi
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Water crisis and water disinfection --- p.1
Chapter 1.2 --- Common disinfection methods --- p.2
Chapter 1.2.1 --- Chlorination --- p.2
Chapter 1.2.2 --- Ozonation --- p.4
Chapter 1.2.3 --- Ultraviolet-C (UV-C) irradiation --- p.6
Chapter 1.2.4 --- Solar disinfection (SODIS) --- p.7
Chapter 1.2.5 --- Mixed disinfectants --- p.9
Chapter 1.2.6 --- Other disinfection methods --- p.10
Chapter 1.3 --- Advanced oxidation processes (AOPs) --- p.11
Chapter 1.4 --- Photocatalytic oxidation (PCO) --- p.13
Chapter 1.4.1 --- Understanding of PCO process --- p.15
Chapter 1.4.2 --- Proposed disinfection mechanism of PCO --- p.18
Chapter 1.4.3 --- Titanium dioxide (Ti02) photocatalyst --- p.21
Chapter 1.4.4 --- Irradiation sources --- p.22
Chapter 1.4.5 --- Bacterial species --- p.23
Chapter 1.4.5.1 --- Escherichia coli K12 --- p.23
Chapter 1.4.5.2 --- Shigella sonnei --- p.24
Chapter 1.4.5.3 --- Alteromonas alvinellae --- p.25
Chapter 1.4.5.4 --- Photobacterium phosphoreum --- p.26
Chapter 1.4.6 --- Bacterial defense mechanism towards oxidative stress --- p.27
Chapter 1.4.6.1 --- Superoxide dismutase (SOD) activity --- p.28
Chapter 1.4.6.2 --- Catalase (CAT) activity --- p.29
Chapter 1.4.6.3 --- Fatty acid (FA) profile --- p.30
Chapter 1.4.7 --- Significance of the project --- p.31
Chapter 2. --- Objectives --- p.34
Chapter 3. --- Material and Methods --- p.36
Chapter 3.1 --- Chemicals --- p.36
Chapter 3.2 --- Screening of freshwater and marine bacterial culture --- p.36
Chapter 3.3 --- Photocatalytic reaction --- p.39
Chapter 3.3.1 --- Preparation of reaction mixture --- p.39
Chapter 3.3.2 --- Preparation of bacterial culture --- p.39
Chapter 3.3.3 --- Photocatalytic reactor --- p.41
Chapter 3.3.4 --- PCO disinfection reaction --- p.42
Chapter 3.3.4.1 --- Effect of initial pH --- p.44
Chapter 3.3.4.2 --- Effect of reaction temperature --- p.45
Chapter 3.3.4.3 --- Effect of growth phases --- p.45
Chapter 3.4 --- Measurement of superoxide dismutase (SOD) activity --- p.47
Chapter 3.5 --- Measurement of catalase (CAT) activity --- p.49
Chapter 3.6 --- Fatty acid (FA) profile --- p.50
Chapter 3.7 --- Bacterial regrowth test --- p.51
Chapter 3.8 --- Atomic absorption spectrophotometry (AAS) --- p.52
Chapter 3.9 --- Total organic carbon (TOC) analysis --- p.53
Chapter 3.10 --- Chlorination --- p.55
Chapter 3.11 --- UV-C irradiation --- p.56
Chapter 3.12 --- Transmission electron microscopy (TEM) --- p.56
Chapter 4. --- Results --- p.60
Chapter 4.1 --- Screening of UV-A resistant freshwater and marine bacteria --- p.60
Chapter 4.2 --- Control experiments --- p.62
Chapter 4.3 --- Treatment experiments --- p.65
Chapter 4.3.1 --- UV-A irradiation from lamps --- p.65
Chapter 4.3.2 --- Fluorescent light from fluorescent lamps --- p.65
Chapter 4.3.3 --- Effect of initial pH --- p.67
Chapter 4.3.4 --- Effect of reaction temperature --- p.70
Chapter 4.3.5 --- Effect of growth phases --- p.70
Chapter 4.4 --- Factors affecting bacterial sensitivity towards PCO --- p.73
Chapter 4.4.1 --- Superoxide dismutase (SOD) and catalase (CAT) activities --- p.73
Chapter 4.4.2 --- Superoxide dismutase (SOD) and catalase (CAT) induction --- p.74
Chapter 4.4.3 --- Fatty acid (FA) profile --- p.75
Chapter 4.5 --- Bacterial regrowth test --- p.78
Chapter 4.6 --- Disinfection mechanisms of fluorescent light-driven photocatalysis --- p.79
Chapter 4.6.1 --- Atomic absorption spectrophotometry (AAS) --- p.79
Chapter 4.6.2 --- Total organic carbon (TOC) analysis --- p.81
Chapter 4.6.3 --- Transmission electron microscopy (TEM) --- p.83
Chapter 4.7 --- Chlorination --- p.89
Chapter 4.7.1 --- Disinfection efficiency --- p.89
Chapter 4.7.2 --- Transmission electron microscopy (TEM) --- p.92
Chapter 4.8 --- UV-C irradiation --- p.96
Chapter 4.8.1 --- Disinfection efficiency --- p.96
Chapter 4.8.2 --- Transmission electron microscopy (TEM) --- p.96
Chapter 5. --- Discussions --- p.103
Chapter 5.1 --- Screening of UV-A resistant freshwater and marine bacteria --- p.103
Chapter 5.2 --- Comparison of PCO coupled with UV-A lamps and fluorescent lamps --- p.103
Chapter 5.3 --- Effect of initial pH --- p.105
Chapter 5.4 --- Effect of reaction temperature --- p.106
Chapter 5.5 --- Effect of growth phases --- p.107
Chapter 5.6 --- Factors affecting bacterial sensitivity towards PCO --- p.108
Chapter 5.6.1 --- Superoxide dismutase (SOD) and catalase (CAT) activities --- p.108
Chapter 5.6.2 --- Superoxide dismutase (SOD) and catalase (CAT) induction --- p.110
Chapter 5.6.3 --- Fatty acid (FA) profile --- p.110
Chapter 5.6.4 --- Cell wall structure --- p.112
Chapter 5.6.5 --- Bacterial size --- p.114
Chapter 5.6.6 --- Other possible factors --- p.114
Chapter 5.7 --- Bacterial regrowth test --- p.115
Chapter 5.8 --- Disinfection mechanisms of fluorescent light-driven photocatalysis --- p.116
Chapter 5.8.1 --- Atomic absorption spectrophotometry (AAS) --- p.116
Chapter 5.8.2 --- Total organic carbon (TOC) analysis --- p.117
Chapter 5.8.3 --- Transmission electron microscopy (TEM) --- p.118
Chapter 5.9 --- Chlorination --- p.122
Chapter 5.9.1 --- Disinfection efficiency --- p.122
Chapter 5.9.2 --- Transmission electron microscopy (TEM) --- p.122
Chapter 5.10 --- UV-C irradiation --- p.123
Chapter 5.10.1 --- Disinfection efficiency --- p.123
Chapter 5.10.2 --- Transmission electron microscopy (TEM) --- p.124
Chapter 5.11 --- Comparisons of three disinfection methods --- p.124
Chapter 6. --- Conclusions --- p.126
Chapter 7. --- References --- p.132

by Fong Wai-lan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 138-152).
Text in English; abstracts in English and Chinese.
by Fong Wai-lan.
Acknowledgements --- p.i
Abstracts --- p.ii
Contents --- p.vi
List of figures --- p.xii
List of Plates --- p.xviii
List of tables --- p.xix
Abbreviations --- p.xxi
Chemical equations --- p.xxiii
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Pentachlorophenol --- p.1
Chapter 1.1.1 --- Characteristics of pentachlorophenol --- p.1
Chapter 1.1.2 --- Use of pentachlorophenol --- p.4
Chapter 1.1.3 --- Annual consumption and regulations for the use of pentachlorophenol --- p.4
Chapter 1.1.4 --- Pentachlorophenol in the environment --- p.4
Chapter 1.1.5 --- Toxicity of pentachlorophenol --- p.5
Chapter I. --- Mechanism --- p.5
Chapter II. --- Toxicity towards plant and animals --- p.7
Chapter III. --- Toxicity towards human --- p.7
Chapter 1.2 --- Treatments of pollutant --- p.9
Chapter 1.2.1 --- Physical treatment --- p.9
Chapter 1.2.2 --- Chemical treatment --- p.9
Chapter 1.2.3 --- Biological treatment --- p.12
Chapter 1.2.4 --- Advanced Oxidation Processes (AOPs) --- p.14
Chapter Chapter 2 --- Objectives --- p.28
Chapter 3 --- Materials and methods --- p.29
Chapter 3.1 --- Chemical reagents --- p.29
Chapter 3.2 --- Photocatalytic reactor --- p.29
Chapter 3.3 --- Determination of pentachlorophenol concentration --- p.31
Chapter 3.4 --- Optimization of reaction conditions for UV-PCO --- p.34
Chapter 3.4.1 --- Batch system --- p.34
Chapter 3.4.1.1 --- Effect of initial hydrogen peroxide concentration --- p.34
Chapter 3.4.1.2 --- "Effect of initial titanium dioxide concentration, light intensity and initial pH" --- p.34
Chapter 3.4.1.3 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.36
Chapter 3.4.2 --- Continuous system --- p.36
Chapter 3.5 --- Optimization of reaction conditions for VL-PCO --- p.38
Chapter 3.5.1 --- "Effect of VL source, initial hydrogen peroxide, titanium dioxide concentration，light intensity, pH and reaction volume" --- p.38
Chapter 3.5.2 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.39
Chapter 3.6 --- Optimization of reaction conditions for S-PCO --- p.39
Chapter 3.6.1 --- "Effect of initial hydrogen peroxide, titanium dioxide concentration，light intensity and pH" --- p.39
Chapter 3.6.2 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.41
Chapter 3.7 --- Modification of photocatalytic oxidation --- p.41
Chapter 3.7.1 --- Buffering system --- p.41
Chapter 3.7.2 --- Immobilized titanium dioxide system --- p.41
Chapter 3.7.2.1 --- Preparation of titanium dioxide coated spiral column --- p.41
Chapter 3.7.2.2 --- Effect of flow rate for the UV-PCO (continuos- buffering/immobilized titanium dioxide) system --- p.43
Chapter 3.8 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.43
Chapter 3.9 --- Evaluation for the toxicity change of pentachlorophenol during the degradation process --- p.43
Chapter 3.9.1 --- Microtox® test --- p.43
Chapter 3.9.2 --- Amphipod survival test --- p.45
Chapter Chapter 4 --- Results --- p.47
Chapter 4.1 --- Determination of pentachlorophenol concentration --- p.47
Chapter 4.2 --- Optimization of reaction conditions for UV-PCO --- p.47
Chapter 4.2.1 --- Batch system --- p.47
Chapter 4.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.47
Chapter 4.2.1.2 --- Effect of initial titanium dioxide concentration --- p.54
Chapter 4.2.1.3 --- Effect of light intensity --- p.54
Chapter 4.2.1.4 --- Effect of initial pH --- p.54
Chapter 4.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.61
Chapter 4.2.2 --- Continuous system --- p.61
Chapter 4.3 --- Optimization of reaction conditions for VL-PCO --- p.69
Chapter 4.3.1 --- Effect of VL source --- p.69
Chapter 4.3.2 --- Effect of initial hydrogen peroxide concentration --- p.69
Chapter 4.3.3 --- Effect of initial titanium dioxide concentration --- p.69
Chapter 4.3.4 --- Effect of light intensity --- p.76
Chapter 4.3.5 --- Effect of initial pH --- p.76
Chapter 4.3.6 --- Effect of reaction volume --- p.76
Chapter 4.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.83
Chapter 4.4 --- Optimization of reaction conditions for S-PCO --- p.83
Chapter 4.4.1 --- Effect of initial hydrogen peroxide concentration --- p.83
Chapter 4.4.2 --- Effect of initial titanium dioxide concentration --- p.90
Chapter 4.4.3 --- Effect of initial pH --- p.90
Chapter 4.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.90
Chapter 4.5 --- Modification of photocatalytic oxidation --- p.96
Chapter 4.5.1 --- Buffering system --- p.96
Chapter 4.5.2 --- Immobilized titanium dioxide system --- p.104
Chapter 4.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.104
Chapter 4.7 --- Evaluation of the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.104
Chapter 4.7.1 --- Microtox® test --- p.104
Chapter 4.7.2 --- Amphipod survival test --- p.112
Chapter Chapter 5 --- Discussion --- p.116
Chapter 5.1 --- Determination of pentachlorophenol concentration --- p.116
Chapter 5.2 --- Optimization of reaction conditions for UV-PCO --- p.116
Chapter 5.2.1 --- Batch system --- p.116
Chapter 5.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.116
Chapter 5.2.1.2 --- Effect of initial titanium dioxide concentration --- p.117
Chapter 5.2.1.3 --- Effect of light intensity --- p.119
Chapter 5.2.1.4 --- Effect of initial pH --- p.119
Chapter 5.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.120
Chapter 5.2.2 --- Continuous system --- p.120
Chapter 5.3 --- Optimization of reaction conditions for VL-PCO --- p.121
Chapter 5.3.1 --- Effect of visible light (VL) source --- p.121
Chapter 5.3.2 --- Effect of initial hydrogen peroxide concentration --- p.121
Chapter 5.3.3 --- Effect of initial titanium dioxide concentration --- p.122
Chapter 5.3.4 --- Effect of light intensity --- p.123
Chapter 5.3.5 --- Effect of initial pH --- p.124
Chapter 5.3.6 --- Effect of reaction volume --- p.124
Chapter 5.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.124
Chapter 5.4 --- Optimization of reaction conditions for S-PCO --- p.125
Chapter 5.4.1 --- Effect of initial hydrogen peroxide concentration --- p.125
Chapter 5.4.2 --- Effect of initial titanium dioxide concentration --- p.126
Chapter 5.4.3 --- Effect of initial pH --- p.127
Chapter 5.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.127
Chapter 5.5 --- Modification of photocatalytic oxidation --- p.128
Chapter 5.5.1 --- Buffering system --- p.128
Chapter 5.5.2 --- Effect of flow rate on removal efficiency for the UV-PCO (continuos-buffering/immobilized titanium dioxide) system --- p.129
Chapter 5.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.130
Chapter 5.7 --- Evaluation for the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.132
Chapter 5.7.1 --- Microtox® test --- p.132
Chapter 5.7.2 --- Amphipod survival test --- p.133
Chapter Chapter 6 --- Conclusions --- p.135
Chapter Chapter 7 --- References --- p.138
Appendix i --- p.153
Appendix ii --- p.154
Appendix iii --- p.154

水資源缺乏引起的一系列問題在世界上已建得到廣泛關注，因此，確保提供潔淨衛生的水在保護人類健康和環境方面起著重要作用。近來，光催化作為頗有前景的替代方法被廣泛應用殺菌除污。二氧化鈦是目前研究最多應用最廣的光催化劑。基於紫外光譜照射，催化劑表面產生活性氧化物種，這些物種具有強氧化性能殺滅細胞。
本文首次研究了母體菌種大腸桿菌BW25113和它的同源單基因缺陷變異體對光催化殺菌的靈敏度差異。母體菌種和變異菌種表現出不同的耐受性。基於此，能幫助發掘出重要的變種。通過生物化學方法，可以檢測出不同菌種的生理性特徵。結合其他方法，可以進一步揭示光催化殺菌的生理性機理。
首先，我們篩選出了兩種重要的變異體。一種是大腸桿菌JW1081，即脂肪酸變異體，該菌種缺乏脂肪酸合成調節的關鍵基因。一種是大腸桿菌JW3942，即乙酰輔酶A變異體，該菌種缺乏乙酰輔酶A合成調控得到關鍵激酶。我們發現脂肪酸變異體對光催化處理的耐受性稍低，而乙酰輔酶A變異體則耐受性較高。 同時發現，溫度可以調節細胞膜的不飽和酸和飽和酸的比例。因此，我們提出脂肪酸和乙酰輔酶A是光催化殺菌中的重要影響因子。
更進一步研究發掘了細胞內酶和光催化產生的活性氧物種間的關係。大腸桿菌JW3914，即過氧化氫酶變異體，是發現的另一個重要的變異體。通過對母體和變異體的淬滅劑實驗，主要的殺菌活性氧物種是光催化產生的雙氧水，而不是羥基自由基。細胞體內的過氧化氫酶誘導在母體菌體內發現，而未在變異體內檢測到。
本課題採用母體/單基因變異體的研究方法，為全面深刻理解光催化殺菌的深層機理提供一種全新的研究思路。
Many problems associated with the lack of clean, fresh water worldwide are well known. Developing countries will particularly be affected by water availability problems and there will be further pressure on water demand resulting from economic development and population growth. Therefore, the provision of safe and clean water plays a key role in protecting human health and the environment. Recently, photocatalytic oxidation (PCO) has been widely accepted as a promising alternative method of water disinfection. Titanium dioxide (TiO₂) has been investigated extensively and is the most widely used photocatalyst. Upon the irradiation of UVA lamp, reactive charged and oxidative species are generated on TiO₂ surface and can inactive the bacterial cells.
In this study, the photocatalytic performances of a parental strain (E.coli BW25113) and its isogenic single-gene deletion mutant strains have been investigated for the first time. These bacterial strains exhibited different sensitivies towards photocalytic inactivation. Based on this, it can help reveal some important mechanism from the mutations. Biotic factors were confirmed by physiological biochemical measurement.
Firstly, we screened out the potential mutation fabF⁻ mutant (E. coli JW1081, carrying the mutation of fabF759(del)::kan) and coaA⁻ mutant (E. coli JW3942, carrying the mutation of coaA755(del)::kan). The isogenic fabF⁻ mutant is slightly more susceptible, and coaA⁻ mutant is less susceptible to photocatalytic inactivation. Through conditioning temperature, it adjusts the ratio of unsaturated to saturated fatty acid (FA) of cell membrane. We propose that FA profile and coenzyme A level significantly affect photocatalytic inactivation of bacteria. Moreover, we show photogenerated electrons (e⁻) can directly inactivate the cells of E. coli.
Furthermore, we report the relationship between the bacterial intracellular enzyme and the reactive charged and oxidative species (ROSs) generated during photocataltic inactivation. The katG⁻ mutant, E. coli JW3914, carrying the mutation of katG729(del)::kan is another important mutation. The parental and katG⁻ mutant strains reveal that photogenerated H₂O₂ but not OH[subscript free] is another important reactive oxygen species to inactivate bacteria. The inducible catalase (CAT) corresponding to H₂O₂can be detected in parental strain but not in katG⁻ mutant.
The research methodology using parental/single-gene deletion mutant strains is expected to shed light on fully understanding of the fundamental mechanism of photocatalytic inactivation of E. coli.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Gao, Minghui.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 130-177).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Acknowledgements --- p.i
Abstract --- p.v
Table of contents --- p.ix
List of Figures --- p.xiii
List of Plates --- p.xvii
List of Tables --- p.xviii
List of Equations --- p.xix
Abbreviations --- p.xxi
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Water crisis --- p.1
Chapter 1.2 --- Traditional disinfection methods --- p.3
Chapter 1.2.1 --- Chlorination --- p.4
Chapter 1.2.2 --- Ozonation --- p.6
Chapter 1.2.3 --- Ultraviolet irradiation --- p.8
Chapter 1.2.4 --- Multiple disinfectants --- p.10
Chapter 1.3 --- Advanced oxidation process (AOPs) --- p.10
Chapter 1.3.1 --- Hydrogen Peroxide/Ozone (H₂O₂/O₃) --- p.11
Chapter 1.3.2 --- Ozone/Ultraviolet Irradiation (O₃/UV) --- p.12
Chapter 1.3.3 --- Hydrogen Peroxide/ Ultraviolet Irradiation (H₂O₂/UV) --- p.12
Chapter 1.3.4 --- Fenton's --- p.Reaction
Chapter 1.4 --- Solar photocatalytic disinfection (SPC-DIS) --- p.14
Chapter 1.4.1 --- Photocatalyst-TiO₂ --- p.31
Chapter 1.4.2 --- Irradiation sources --- p.35
Chapter 1.4.3 --- TiO₂ photocatalytic process --- p.35
Chapter 1.4.4 --- The role of photogenerated reactive charged and oxidative species (ROSs) --- p.38
Chapter 1.5 --- Bacteria --- p.40
Chapter 1.5.1 --- E. coli BW25113 --- p.40
Chapter 1.5.2 --- E. coli Keio Collection --- p.41
Chapter 1.5.3 --- Bacterial defense mechanism towards oxidative stresses --- p.44
Chapter 1.6 --- Photocalytic applications --- p.53
Chapter 1.7 --- Significance of the project --- p.55
Chapter 2. --- Objectives --- p.58
Chapter 3. --- Genetic studies of the roles of fatty acid and coenzyme A in photocatalytic inactivation of Escherichia coli --- p.61
Chapter 3.1 --- Introduction --- p.61
Chapter 3.2 --- Materials and methods --- p.65
Chapter 3.2.1 --- Photocatalyst --- p.65
Chapter 3.2.2 --- Bacterial nutrient --- p.66
Chapter 3.2.3 --- Bacterial strains --- p.67
Chapter 3.2.4 --- Photocatalytic inactivation --- p.69
Chapter 3.2.5 --- Fatty acid profile --- p.72
Chapter 3.2.6 --- Fluorescent measurement of bacterial coenzyme A content --- p.74
Chapter 3.2.7 --- The role of photogenerated electrons (e⁻) to bacterial inactivation --- p.74
Chapter 3.2.8 --- Transmission Electron Microscopic (TEM) --- p.75
Chapter 3.2.9 --- Photoelectrochemical measurement --- p.77
Chapter 3.3 --- Results --- p.77
Chapter 3.3.1 --- Photocatalytic inactivation --- p.77
Chapter 3.3.2 --- Effects of pre-incubation at different temperatures --- p.80
Chapter 3.3.3 --- Fatty acid profile --- p.83
Chapter 3.3.4 --- Fluorescent measurement of bacterial coenzyme A content --- p.84
Chapter 3.3.5 --- The role of electron (e⁻) in photocataytic inactivation --- p.84
Chapter 3.3.6 --- Transmission electron microscopy (TEM) --- p.89
Chapter 3.3.7 --- Photocurrent measurement --- p.90
Chapter 3.4 --- Discussion --- p.90
Chapter 3.5 --- Conclusions --- p.96
Chapter 4 --- Genetic and physiological studies of the role of Catalase and H₂O₂ in photocatalytic inactivation of E. coli --- p.98
Chapter 4.1 --- Introduction --- p.98
Chapter 4.2 --- Materials and methods --- p.101
Chapter 4.2.1 --- Bacterial strains --- p.101
Chapter 4.2.2 --- Photocatalytic performance --- p.102
Chapter 4.2.3 --- Scavenger studies --- p.103
Chapter 4.2.4 --- Effects of different pHs on photocatalytic inactivation --- p.104
Chapter 4.2.5 --- Measurement of bacterial catalase activity and H₂O₂ --- p.104
Chapter 4.2.6 --- Transmission electron microscopy (TEM) --- p.105
Chapter 4.2.7 --- Atomic absorption spectrophotometer (AAS) --- p.105
Chapter 4.3 --- Results and discussion --- p.106
Chapter 4.3.1 --- Photocatalytic performance --- p.106
Chapter 4.3.2 --- Scavenger studies --- p.108
Chapter 4.3.3 --- Contribution of hydrogen peroxide (H₂O₂) --- p.111
Chapter 4.3.4 --- Effects of different pHs on photocatalytic inactivation --- p.114
Chapter 4.3.5 --- Bacterial catalase (CAT) activity --- p.116
Chapter 4.3.6 --- Destruction model of bacterial cells --- p.118
Chapter 4.4 --- Conclusions --- p.120
Chapter 5. --- General conclusions --- p.122
Chapter 6. --- Prospectives --- p.125
Chapter 7. --- Appendix --- p.127
Chapter 8. --- References --- p.130

Wong Man Yung.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (leaves 106-120).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstract --- p.ii
Table of Contents --- p.vi
List of Figures --- p.xi
List of Plates --- p.xiii
List of Tables --- p.xv
Abbreviations --- p.xvi
Equations --- p.xviii
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Water disinfection --- p.1
Chapter 1.2 --- Bacterial species --- p.2
Chapter 1.2.1 --- Staphylococcus saprophyticus --- p.2
Chapter 1.2.2 --- Enterobacter cloacae --- p.3
Chapter 1.3 --- Disinfection methods --- p.4
Chapter 1.3.1 --- Physical methods --- p.4
Chapter 1.3.1.1 --- UV-C irradiation --- p.4
Chapter 1.3.1.2 --- Solar disinfection --- p.5
Chapter 1.3.2 --- Chemical methods --- p.6
Chapter 1.3.2.1 --- Chlorination --- p.6
Chapter 1.3.2.2 --- Ozonation --- p.7
Chapter 1.3.2.3 --- Mixed disinfectants --- p.8
Chapter 1.3.3 --- Other disinfection methods --- p.8
Chapter 1.4 --- Advanced oxidation processes (AOPs) --- p.9
Chapter 1.5 --- Photocatalytic oxidation (PCO) --- p.10
Chapter 1.5.1 --- PCO process --- p.12
Chapter 1.5.2 --- Photocatalysts --- p.14
Chapter 1.5.2.1 --- Titanium dioxide (P25) --- p.15
Chapter 1.5.2.2 --- Silver sensitized P25 (Ag/P25) --- p.16
Chapter 1.5.2.3 --- Silicon dioxide doped titanium dioxide (SiO2-TiO2) --- p.17
Chapter 1.5.2.4 --- Copper(I) oxide sensitized P25 (Cu2O/P25) --- p.18
Chapter 1.5.3 --- Irradiation sources --- p.19
Chapter 1.5.4 --- PCO disinfection mechanisms --- p.20
Chapter 1.6 --- Bacterial defense mechanisms against oxidative stress --- p.22
Chapter 2. --- Objectives --- p.25
Chapter 3. --- Materials and Methods --- p.26
Chapter 3.1 --- Chemicals --- p.26
Chapter 3.2 --- Bacterial culture --- p.26
Chapter 3.3 --- Photocatalytic reactor --- p.27
Chapter 3.4 --- PCO efficacy test --- p.30
Chapter 3.5 --- Optimization of PCO conditions --- p.31
Chapter 3.5.1 --- Effect of P25 concentrations --- p.31
Chapter 3.5.2 --- Effect of UV intensities --- p.32
Chapter 3.5.3 --- Combinational study of P25 concentrations and UV intensities --- p.32
Chapter 3.5.4 --- Effect of stirring rates --- p.32
Chapter 3.5.5 --- Effect of initial cell concentrations --- p.33
Chapter 3.6 --- PCO disinfection using different photocatalysts --- p.33
Chapter 3.6.1 --- Effect of CU2O/P25 concentrations --- p.33
Chapter 3.6.2 --- Effect of CU2O powder on the two bacterial species --- p.33
Chapter 3.7 --- Transmission electron microscopy (TEM) --- p.34
Chapter 3.8 --- Catalase (CAT) test --- p.37
Chapter 3.9 --- Superoxide dismutase (SOD) activity assay --- p.39
Chapter 4. --- Results --- p.40
Chapter 4.1 --- Efficacy test --- p.40
Chapter 4.2 --- PCO disinfection under UV irradiation --- p.40
Chapter 4.2.1 --- Control experiments --- p.40
Chapter 4.2.2 --- Optimization of PCO conditions using P25 as a photocatalyst --- p.42
Chapter 4.2.2.1 --- Effect of P25 concentrations --- p.42
Chapter 4.2.2.2 --- Effect of UV intensities --- p.45
Chapter 4.2.2.3 --- Combinational study of P25 concentrations and UV intensities --- p.48
Chapter 4.2.2.4 --- Effect of stirring rates --- p.54
Chapter 4.2.2.5 --- Effect of initial cell concentrations --- p.57
Chapter 4.2.3 --- Comparison of PCO inactivation efficiency between S. saprophyticus and E. cloacae --- p.60
Chapter 4.2.4 --- PCO disinfection using different photocatalysts --- p.62
Chapter 4.2.4.1 --- Control experiments --- p.62
Chapter 4.2.4.2 --- Ag/P25 --- p.62
Chapter 4.2.4.3 --- SiO2-TiO2 --- p.64
Chapter 4.2.4.4 --- Cu2O/P25 --- p.64
Chapter 4.3 --- PCO disinfection under visible light irradiation --- p.66
Chapter 4.3.1 --- Effect of Cu2O/P25 concentrations --- p.67
Chapter 4.3.2 --- Effect of CU2O powder on the two bacterial species --- p.70
Chapter 4.4 --- Feasibility use of indoor light (fluorescent lamps) for PCO disinfection --- p.71
Chapter 4.5 --- Transmission electron microscopy (TEM) --- p.74
Chapter 4.5.1 --- Morphological changes induced by PCO using P25 as a photocatalyst --- p.74
Chapter 4.5.2 --- Morphological changes induced by PCO using Cu2O/P25 as a photocatalyst --- p.77
Chapter 4.6 --- Catalase (CAT) test --- p.80
Chapter 4.7 --- Superoxide dismutase (SOD) activity assay --- p.82
Chapter 5. --- Discussion --- p.83
Chapter 5.1 --- Efficacy test --- p.83
Chapter 5.2 --- PCO disinfection under UV irradiation --- p.83
Chapter 5.2.1 --- Optimization study --- p.84
Chapter 5.2.1.1 --- Effect of P25 concentrations --- p.84
Chapter 5.2.1.2 --- Effect of UV intensities --- p.85
Chapter 5.2.1.3 --- Combinational study of P25 concentrations and UV intensities --- p.86
Chapter 5.2.1.4 --- Effect of stirring rates --- p.86
Chapter 5.2.1.5 --- Effect of initial cell concentrations --- p.87
Chapter 5.2.2 --- Comparison of PCO inactivation efficiency between S. saprophyticus and E. cloacae --- p.88
Chapter 5.2.3 --- PCO disinfection using different photocatalysts --- p.89
Chapter 5.2.3.1 --- Ag/P25 --- p.89
Chapter 5.2.3.2 --- SiO2-TiO2 and Cu2O/P25 --- p.90
Chapter 5.3 --- PCO disinfection under visible light irradiation --- p.90
Chapter 5.3.1 --- Effect of Cu20/P25 concentrations --- p.91
Chapter 5.3.2 --- Effect of CU2O powder on the two bacterial species --- p.92
Chapter 5.4 --- Feasibility use of fluorescent lamps for PCO disinfection --- p.93
Chapter 5.5 --- Transmission electron microscopy (TEM) --- p.95
Chapter 5.5.1 --- Morphological changes induced by PCO using P25 as a photocatalyst --- p.95
Chapter 5.5.2 --- Morphological changes induced by PCO using CU2O/P25 as a photocatalyst --- p.96
Chapter 5.6 --- Catalase (CAT) test --- p.98
Chapter 5.7 --- Superoxide dismutase (SOD) activity assay --- p.99
Chapter 6. --- Conclusion --- p.101
Chapter 7. --- References --- p.106
Chapter 8. --- Appendix --- p.121

Kwong Tsz Yan Alex.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 77-84).
Abstracts in English and Chinese.
Abstract --- p.i
Declaration --- p.iii
Acknowledgement --- p.iv
Table of contents --- p.v
List of tables --- p.ix
List of figures --- p.x
Chapter Chapter One : --- Introduction --- p.1
Chapter 1.1 --- The outbreak of SARS --- p.1
Chapter 1.2 --- Characteristics of triclosan --- p.2
Chapter 1.3 --- Environmental fate of triclosan --- p.3
Chapter 1.4 --- Treatment methods for triclosan --- p.5
Chapter 1.5 --- Ti02 photocatalysis --- p.6
Chapter 1.6 --- Addition of hydrogen peroxide to the photocatalytic system --- p.9
Chapter 1.7 --- Gas chromatography/ ion trap mass spectrometry analysis --- p.10
Chapter 1.8 --- Scope of work --- p.11
Chapter Chapter Two : --- Experimental --- p.13
Chapter 2.1 --- Chemical reagents --- p.13
Chapter 2.2 --- Photocatalytic experiments --- p.14
Chapter 2.3 --- "Analysis of 2,8-DCDD and triclosan by GC/ITMS" --- p.15
Chapter 2.4 --- Optimization of GC/ITMS conditions --- p.17
Chapter 2.5 --- Analysis of other reaction intermediates by GC/MS (full scan mode) --- p.18
Chapter 2.6 --- "Analysis of 2,4-dichlorophenol and triclosan by GC/MS (SIM mode)" --- p.20
Chapter 2.7 --- Effect of hydrogen peroxide concentration on triclosan degradation --- p.20
Chapter 2.8 --- Determination of total organic carbon (TOC) removal --- p.21
Chapter 2.9 --- UV-Visible spectrometry --- p.21
Chapter Chapter Three : --- Results --- p.22
Chapter 3.1 --- Selection of precursor ions for GC/ITMS analysis --- p.22
Chapter 3.2 --- Optimization of GC/ITMS conditions --- p.25
Chapter 3.3 --- "Analysis of 2,8-DCDD and triclosan by GC/ITMS" --- p.27
Chapter 3.4 --- "Analysis of 2,4-dichlorophenol and triclosan by GC/MS (SIM mode)" --- p.29
Chapter 3.5 --- "Quantitative measurement of 2,8-DCDD in UV irradiated samples" --- p.31
Chapter 3.6 --- Photocatalytic oxidation of triclosan by UV at 365nm --- p.33
Chapter 3.7 --- TOC removal in triclosan degradation --- p.35
Chapter 3.8 --- Identification of intermediates in photocatalytic oxidation of triclosan --- p.36
Chapter 3.9 --- Quantitative measurement of the intermediates in photocatalytic oxidation of triclosan --- p.41
Chapter 3.10 --- Effect of hydrogen peroxide concentration on triclosan degradation --- p.43
Chapter 3.11 --- Effect of hydrogen peroxide concentration on TOC removal --- p.46
Chapter 3.12 --- "Effect of hydrogen peroxide concentration on 2,4-dichlorophenol generation during triclosan degradation" --- p.47
Chapter 3.13 --- "Photocatalytic degradation of 2,4-dichlorophenol" --- p.49
Chapter 3.14 --- "Identification of intermediates in photocatalytic oxidation of 2,4-dichlorophenol" --- p.50
Chapter 3.15 --- "Quantitative measurement of the intermediates in photocatalytic oxidation of 2,4-dichlorophenol" --- p.54
Chapter Chapter Four : --- Discussions --- p.56
Chapter 4.1 --- "Photochemical conversion of triclosan to 2,8-DCDD" --- p.56
Chapter 4.2 --- Proposed mechanism of triclosan degradation --- p.57
Chapter 4.3 --- "Proposed mechanism of 2,4-dichlorophenol degradation" --- p.63
Chapter 4.4 --- TOC removal in triclosan degradation --- p.65
Chapter 4.5 --- Effect of hydrogen peroxide concentration on photocatalytic oxidation of triclosan --- p.65
Chapter 4.6 --- "Adverse environmental and human health effects of 2,8-DCDD" --- p.69
Chapter 4.7 --- "Adverse environmental and human health effects of 2,4-dichlorophenol" --- p.71
Chapter 4.8 --- "Discharge limitations for 2,4-dichlorophenol" --- p.73
Chapter Chapter Five : --- Conclusions --- p.75
References --- p.77

由於潔淨用水日漸短缺，科學家著力研究各種水淨化方法，其中以光催化技術作水淨化處理為可行的方法之一。光催化是以半導體光催化劑在光照射下所產生的活性物種（reactive oxidative species）進行消毒，其中的失活原理、各活性物種的作用和活性物種對細菌的攻擊方位，雖然已有廣範的研究，但當中仍有不清之處，比如說過氧化氫(H₂O₂)在光催化失活的作用便是其中之一，在光催化系統中所產生的H₂O₂濃度一般較低，因此其對細菌失活的效能仍然存有爭議。
本研究設計一種新的反應器去研究H₂O₂在連續供應模式中的失活動力學。在 8 mM 的H₂O₂下，10⁵的大腸桿菌(Escherichia coli)在8小時內完全失活。而在 2 mM 的H₂O₂ 下，並無出現顯著失活，由於該濃度遠遠高於一般光催化系統所產生的濃度（<50 μM），因此可以推斷，即使一般光催化系統所產生的H₂O₂是連續供應，也不會使細菌失活。然而在光照的情況下，其失活動力學大為不同，在強光照射(200 mW cm⁻²)下，H₂O₂的失活效率顯著增強，證明光照和過氧化氫之間存有協同效應。這現象亦出現於光預處理過(light pretreated)的大腸桿菌，進一步證實了光照改變細菌的生理機能，從而使其易於被H₂O₂失活。
其後我們使用RNA測序(RNA sequencing)去檢測的大腸桿菌的基因表達水平在光照下的變化，以便研究光照和H₂O₂之間的協同作用的機理。大多數涉及抵抗氧化的基因，包括過氧化氫酶(catalase, CAT)和超氧化物歧化酶(superoxide dismutase,SOD)的表達、DNA修復及細菌內的鐵含調控等等，其mRNA 水平沒有顯著的增加或減少，只有dps、fes和sodB有明顯的變化。此外，還有幾種調控細胞內的銅合量（cutA和cueR）和細胞膜組成（ompA、ompC、resx和gnsB）的基因在光照下產生顯著變化。 經RNA測序後，我們選定了10個目標基因，並選擇相對的大腸桿菌變異體(mutants)，對比他們和母體(E. coli BW25113)經過光預處理後被H₂O₂的失活效能。雖然這次研究並未找到相關基因，但研究結果表示，光照和H₂O₂的協同效應，應該是光照增加細胞膜的通透性和提高細菌內Fenton劑含量，使細菌內的羥基自由基(·OH)的濃度增加，因此加強對細菌DNA的損傷。
最後，我們亦比較了AgBr/Ag/Bi₂WO₆在不同的光源的照射下的對大腸桿菌的光催化失活效率。雖然發光二極管(light emitting diode)和熒光管都常用於室內照明，但AgBr/Ag/Bi₂WO₆的細菌失活效率在兩者的光照下表現出顯著的差異，而不同的發射波長下的細菌失活效率和AgBr/Ag/Bi₂WO₆光學吸收表現出良好的相關性。此外，相對其他顏色的發光二極管，綠色發光二極管照射下在犧牲劑研究(scavenger study)的結果大為不同，進一步表明了光照的發射波長(emissionwavelength)對光催化失活機制的影響。
本研究揭示了H₂O₂和光照在光催化失活中的重要性，並演示了H₂O₂和光照射之間的協同作用，也闡明了光照的屬性如何影響光催化下各活性物種的產生。本研究不僅提供了一個新的角度去探討的光照、H₂O₂和細菌的生理狀態在光催化失活中的重要性，也提供了新的方向和方法去研究光催化失活機制的。
Due to the increasing concern for the need of clean drinking water, different methods for water purification have been developed. Photocatalysis, which makes use of semiconductor photocatalyst for the generation of reactive charged and oxidative species (ROSs) under light irradiation, is one of the most promising methods for water disinfection. The mechanisms of the photocatalytic inactivation have been extensively investigated. Different factors, including the roles of ROSs and the ROSs target site(s) of bacterial cell, were elaborated by different studies. However, there are still controversial issues on the role of H₂O₂ in photocatalytic inactivation. The effectiveness of the low concentration of H₂O₂ in the bacterial inactivation process is still under question.
This study designs a new reactor to study the kinetic of H₂O₂ inactivation in continuous supply mode. Complete inactivation of 5-log Escherichia coli within 8 h is achieved when 8 mM of H₂O₂ is applied. No significant inactivation was observed when 2 mM H₂O₂ is applied, this concentration of H₂O₂ is much higher than that detected in common photocatalytic system (< 50 μM). The results show that H₂O₂ produced by common photocatalytic system is not harmful to bacterial cell, even they are produced continuously. However, when light irradiation of 200 mW cm⁻² , using Xenon lamp as lighting source, was applied to the system, the inactivation efficiency of H₂O₂ was significantly enhanced, which demonstrate the synergistic effect between the light irradiation and H₂O₂. The enhancement of inactivation by H₂O₂ can also be observed with light pretreated E. coli K-12, further confirms that light irradiation alter the physiology of the bacterial cell which increases their sensitivity to H₂O₂.
In order to find out the mechanism(s) of the synergism between the light irradiation and H₂O₂, RNA sequencing (RNA-Seq) was used to reveal the change of gene expression level of the E. coli under light irradiation. The mRNA level of most of the genes involve in catalase (CAT) and superoxide dismutase (SOD) expression, DNA repairing and intracellular iron regulation did not have significant increase or decrease. Only dps, fes and sodB showed significantly changes. Moreover, some genes that related to regulation of intracellular copper (cutA and cueR) and membrane composition (ompA, ompC, resX and gnsB) also showed significantly changes under light irradiation. After the RNA-Seq, ten genes were chosen as the possible target genes that related to the mechanism(s). Then the inactivation of E. coli BW25113 (parental strain) and the isogenic deleted mutants by H₂O₂ with light pretreatment were conducted and compared. Although the gene(s) that directly involved in the mechanisms of the synergy between H₂O₂ and light irradiation are not identified in the study, the results show that genes that are important to bacterial defense of oxidative damages, such those responsible for CAT and SOD expression and DNA repairing, are not involved in the mechanism(s). Increase of cell permeability and intracellular Fenton’s reagent content should be the main causes for the enhancement of H₂O₂ under light irradiation.
Finally, the inactivation efficiency of E. coli K-12 using AgBr/Ag/Bi₂WO₆ under different lighting sources is compared. The results show that inactivation efficiency under different emission wavelength are highly correlated with the optical absorption of the AgBr/Ag/Bi₂WO₆. Photocatalytic inactivation under two indoor lighting sources, LED lamps and Fluorescence tubes, also showed significant difference. The result of scavenger study under green LED lamps is completely different from those under other colour of LED lamps, indicates that emission wavelength also has great influence in photocatalytic inactivation mechanisms.
This study reveals the roles of H₂O₂ and light irradiation in photocatalytic inactivation and demonstrates the synergism between the H₂O₂ and light irradiation. The influence of the properties of light irradiation, including the light intensity and major emission wavelength, on the ROSs production by photocatalyst is also reported as well. This study not only provides a new perspective to the importance of light irradiation, H₂O₂ and the physiology of bacteria in photocatalytic inactivation, but a new approach in the investigation of photocatalytic inactivation mechanisms as well.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Ng Tsz Wai.
Thesis (Ph.D.) Chinese University of Hong Kong, 2014.
Includes bibliographical references (leaves 111-131).
Abstracts also in Chinese.

by Wong Kin-hang.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references (leaves 99-127).
Text in English; abstracts in English and Chinese.
by Wong Kin-hang.
Acknowledgements --- p.i
Abstracts --- p.ii
Contents --- p.vi
List of Figures --- p.ix
List of Tables --- p.x
Abbreviations --- p.xi
Chemical Equations --- p.xii
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Poly chlorinated biphenyls --- p.1
Chapter 1.1.1 --- Characteristics of polychlorinated biphenyls (PCBs) --- p.1
Chapter 1.1.2 --- Use of polychlorinated biphenyls --- p.3
Chapter 1.1.3 --- World-wide production of polychlorinated biphenyls --- p.7
Chapter 1.1.4 --- Polychlorinated biphenyls in the environment --- p.8
Chapter 1.1.5 --- Toxicity of polychlorinated biphenyls --- p.12
Chapter I. --- Mechanism --- p.12
Chapter II. --- Toxicity towards plant and animals --- p.13
Chapter III. --- Toxicity towards human --- p.14
Chapter IV. --- Enzymatic induction by PCBs --- p.14
Chapter V. --- Carcinogenicity of PCBs --- p.18
Chapter 1.2 --- Treatments of pollutant --- p.19
Chapter 1.2.1 --- Physical treatment --- p.19
Chapter 1.2.2 --- Chemical treatment --- p.20
Chapter 1.2.3 --- Biological treatment --- p.22
Chapter 1.2.4 --- Photocatalytic oxidation (PCO) --- p.25
Chapter Chapter 2 --- Objectives --- p.35
Chapter Chapter 3 --- Materials and methods --- p.36
Chapter 3.1 --- Chemical reagents --- p.36
Chapter 3.2 --- Photocatalytic oxidation reactor --- p.36
Chapter 3.3 --- Separation and determination of eight PCB congeners --- p.39
Chapter 3.4 --- Determination of tetra-CB concentration --- p.40
Chapter 3.5 --- Determination of PCO intermediates and products --- p.41
Chapter 3.6 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.44
Chapter 3.6.1 --- Control experiments and effect of initial titanium dioxide concentration --- p.44
Chapter 3.6.2 --- Effect of initial hydrogen dioxide concentration and UV intensity --- p.44
Chapter 3.6.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.45
Chapter 3.7 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.45
Chapter 3.8 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB during PCO by Microtox® test --- p.45
Chapter 3.9 --- Determination of H202 concentration after PCO --- p.47
Chapter Chapter 4 --- Results --- p.50
Chapter 4.1 --- Separation and determination of eight PCB congeners --- p.50
Chapter 4.2 --- Photocatalytic oxidation of mono-CB --- p.50
Chapter 4.3 --- Determination of tetra-CB --- p.55
Chapter 4.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.56
Chapter 4.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.56
Chapter 4.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.56
Chapter 4.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.60
Chapter 4.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.71
Chapter 4.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.72
Chapter 4.7 --- Determination of H202 concentration after PCO --- p.72
Chapter Chapter 5 --- Discussion --- p.89
Chapter 5.1 --- Separation and determination of eight PCB congeners --- p.89
Chapter 5.2 --- Photocatalytic oxidation of mono-CB --- p.89
Chapter 5.3 --- Determination of tetra-CB --- p.90
Chapter 5.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.90
Chapter 5.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.91
Chapter 5.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.91
Chapter 5.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.93
Chapter 5.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.95
Chapter 5.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.96
Chapter 5.7 --- Determination of H202 concentration after PCO --- p.97
Chapter Chapter 6 --- Conclusions --- p.98
Chapter Chapter 7 --- References --- p.99

D.Phil. (Chemistry)
Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water-pollution control. Among the many organic pollutants are dyes and emerging pollutants such as natural organic matter (NOM). Dyes such as Eosin Yellow (EY), an anionic xanthene fluorescent dye, can originate from many sources such as textile industrial processes, paper pulp industries and agricultural processes. Most dyes are problematic because they are resistant to conventional chemical or biological water-treatment methods and therefore persist in the environment. NOM consists of a highly variable mixture of products found in water and soils. NOM is formed as a result of the decomposition of plant and animal material and is a precursor to the formation of disinfection by-products (DBP) during water disinfection. These organic compounds cause undesirable colour, taste and odour in water. NOM affects the capacity of other treatment processes to effectively remove organic micro-pollutants or inorganic species that may be present in the water. Its removal also uses up chemicals and energy and so it is expensive to treat. Titanium dioxide (TiO2) has emerged as one of the most fascinating materials in the modern era due to its semiconducting and catalytic properties. TiO2 is a large band-gap semiconductor that exists mainly in the anatase (band gap 3.2 eV) and rutile (band gap 3.0 eV) phases. Its response to UV light has led to increased interest in its application in the photocatalysis research field. It has been investigated extensively for its super hydrophilicity and use in environmental remediation and solar fuel production. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the ultimate goal of this research was to fabricate highly photoactive catalysts composed of non-metal, platinum-group metal (PGM) co-doped TiO2 and carbon nanotubes (CNTs) and to apply them for water purification using solar radiation...

by chan Cho-Yin.
"November 2005."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (p. 128-142).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Text in English; abstracts in English and Chinese.
by Chan Cho-Yin.

by Cheung Kit Hing.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 175-199).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstracts --- p.ii
Table of Contents --- p.vi
List of Figures --- p.xviii
List of Plates --- p.xxii
List of Tables --- p.xxiii
Abbreviations --- p.xxv
Equations --- p.xxviii
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- The chemistry of azo dyes --- p.1
Chapter 1.2 --- Azo dyes classification --- p.2
Chapter 1.3 --- Environmental concerns and toxicity --- p.4
Chapter 1.3.1 --- Toxicity of azo dyes --- p.5
Chapter 1.3.2 --- Carcinogenicity --- p.5
Chapter 1.3.3 --- Ecotoxicity --- p.11
Chapter 1.3.3.1 --- Toxicity to microorganisms --- p.12
Chapter 1.3.3.2 --- Toxicity towards vertebrates --- p.13
Chapter 1.4 --- Treatment of azo dyes --- p.13
Chapter 1.4.1 --- Physical treatment --- p.14
Chapter 1.4.1.1 --- Adsorption --- p.14
Chapter 1.4.1.2 --- Membrane technology --- p.15
Chapter 1.4.2 --- Chemical treatments --- p.15
Chapter 1.4.2.1 --- Chlorination --- p.16
Chapter 1.4.2.2 --- Fenton's reaction --- p.16
Chapter 1.4.2.3 --- Ozonation --- p.16
Chapter 1.4.2.4 --- Coagulation --- p.17
Chapter 1.4.3 --- Biological treatments --- p.17
Chapter 1.4.3.1 --- Activated sludge process --- p.18
Chapter 1.4.3.2 --- Biodegradation --- p.18
Chapter 1.4.3.3 --- Biosorption --- p.21
Chapter 1.4.3.3.1 --- Modeling of sorption --- p.24
Chapter 1.4.3.3.1.1 --- Langmuir sorption model --- p.24
Chapter 1.4.3.3.1.2 --- Freundlich sorption model --- p.25
Chapter 1.4.4 --- Advanced oxidation processes --- p.25
Chapter 1.4.4.1 --- Photocatalytic oxidation --- p.26
Chapter 1.4.4.2 --- Titanium dioxide (TiO2) --- p.26
Chapter 1.4.4.3 --- Mechanism of photocatalytic oxidation using photocatalyst TiO2 --- p.28
Chapter 1.4.4.4 --- Photocatalytic oxidation of s-triazine containing compounds --- p.30
Chapter 1.4.4.5 --- Photocatalytic oxidation of Procion Red MX-5B --- p.31
Chapter 1.4.4.6 --- Cyanuric acid --- p.32
Chapter 1.4.4.6.1 --- Application --- p.32
Chapter 1.4.4.6.2 --- Toxicity --- p.32
Chapter 1.4.4.6.3 --- Photocatalytic oxidation resistance --- p.34
Chapter 1.4.4.6.4 --- Biodegradation --- p.35
Chapter 1.4.4.7 --- Enhancement of photocatalytic oxidation by using sorbent immobilized with TiO2 --- p.35
Chapter 1.4.4.7.1 --- Sorption --- p.35
Chapter 1.4.4.7.2 --- Immobilization of TiO2 --- p.37
Chapter 1.4.8 --- Integration of treatment methods --- p.39
Chapter 2. --- Objectives --- p.41
Chapter 3. --- Materials and methods --- p.42
Chapter 3.1. --- Sorption --- p.42
Chapter 3.1.1 --- Chemical reagents --- p.42
Chapter 3.1.2 --- Determination of Procion Red MX-5B --- p.42
Chapter 3.1.3 --- Sampling --- p.44
Chapter 3.1.4 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.44
Chapter 3.1.5 --- Screening of Procion Red MX-5B sorption ability --- p.44
Chapter 3.1.6 --- Identification of isolated bacterium --- p.46
Chapter 3.1.7 --- Optimization of cell yield and sorption capacity --- p.47
Chapter 3.1.7.1 --- Preparation of cell culture of Vibrio sp. --- p.47
Chapter 3.1.7.2 --- Growth phase --- p.47
Chapter 3.1.7.2.1 --- Growth curve --- p.47
Chapter 3.1.7.2.2 --- Dye sorption capacity --- p.47
Chapter 3.1.7.3 --- Initial pH --- p.48
Chapter 3.1.7.3.1 --- Growth curve --- p.48
Chapter 3.1.7.3.2 --- Dye sorption capacity --- p.48
Chapter 3.1.7.4 --- Temperature --- p.49
Chapter 3.1.7.4.1 --- Growth curve --- p.49
Chapter 3.1.7.4.2 --- Dye sorption capacity --- p.49
Chapter 3.1.7.5 --- Glucose concentrations --- p.49
Chapter 3.1.7.5.1 --- Growth curve --- p.49
Chapter 3.1.7.5.2 --- Dye sorption capacity --- p.50
Chapter 3.1.8 --- Optimization of sorption process --- p.50
Chapter 3.1.8.1 --- Preparation of sorbent --- p.50
Chapter 3.1.8.2 --- Dry weight of sorbent --- p.50
Chapter 3.1.8.3 --- Temperature --- p.50
Chapter 3.1.8.4 --- Agitation rate --- p.50
Chapter 3.1.8.5 --- Salinity --- p.51
Chapter 3.1.8.6 --- Initial pH --- p.51
Chapter 3.1.8.7 --- Concentration of Procion Red MX-5B --- p.51
Chapter 3.1.8.8 --- Combination study of salinity and initial pH --- p.51
Chapter 3.2. --- Photocatalytic oxidation reaction --- p.52
Chapter 3.2.1 --- Chemical reagents --- p.52
Chapter 3.2.2 --- Photocatalytic reactor --- p.52
Chapter 3.2.3 --- Optimization of sorption and photocatalytic oxidation reactions using biomass of Vibrio sp.immobilized in calcium alginate beads --- p.54
Chapter 3.2.3.1 --- Effect of dry weight of immobilized cells of Vibrio sp. --- p.54
Chapter 3.2.3.1.1 --- Sorption --- p.55
Chapter 3.2.3.1.2 --- Photocatalytic oxidation --- p.56
Chapter 3.2.3.2 --- Effect of UV intensities --- p.57
Chapter 3.2.3.3 --- Effect of TiO2 concentrations --- p.57
Chapter 3.2.3.3.1 --- Sorption --- p.57
Chapter 3.2.3.3.2 --- Photocatalytic oxidation --- p.57
Chapter 3.2.3.4 --- Effect of H202 concentrations --- p.57
Chapter 3.2.3.5 --- Effect of the number of beads --- p.58
Chapter 3.2.3.5.1 --- Sorption --- p.58
Chapter 3.2.3.5.2 --- Photocatalytic oxidation --- p.58
Chapter 3.2.3.6 --- Effect of initial pH with and without the addition of H2O2 --- p.58
Chapter 3.2.3.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.59
Chapter 3.2.3.8 --- Combinational study of UV intensities and H2O2 concentrations --- p.59
Chapter 3.2.3.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.59
Chapter 3.2.3.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L TiO2" --- p.59
Chapter 3.3 --- Biodegradation --- p.60
Chapter 3.3.1 --- Chemical reagents --- p.60
Chapter 3.3.2 --- Sampling --- p.60
Chapter 3.3.3 --- Enrichment --- p.60
Chapter 3.3.4 --- Isolation of cyanuric acid-utilizing bacteria --- p.61
Chapter 3.3.5 --- Determination of cyanuric acid --- p.61
Chapter 3.3.6 --- Screening of Procion Red MX-5B sorption ability --- p.61
Chapter 3.3.7 --- Screening of cyanuric acid-utilizing ability --- p.61
Chapter 3.3.8 --- Bacterial identification --- p.63
Chapter 3.3.9 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.63
Chapter 3.3.10 --- Optimization of reaction conditions --- p.64
Chapter 3.3.10.1 --- Effect of salinity --- p.64
Chapter 3.3.10.2 --- Effect of cyanuric acid concentrations --- p.65
Chapter 3.3.10.3 --- Effect of temperature --- p.65
Chapter 3.3.10.4 --- Effect of agitation rate --- p.65
Chapter 3.3.10.5 --- Effect of initial pH --- p.66
Chapter 3.3.10.6 --- Effect of initial glucose concentration --- p.66
Chapter 3.3.10.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.66
Chapter 3.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.66
Chapter 3.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.67
Chapter 4. --- Results --- p.68
Chapter 4.1. --- Sorption --- p.68
Chapter 4.1.1 --- Determination of Procion Red MX-5B --- p.68
Chapter 4.1.2 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.68
Chapter 4.1.3 --- Screening of Procion Red MX-5B sorption ability --- p.68
Chapter 4.1.4 --- Identification of isolated bacterium --- p.72
Chapter 4.1.5 --- Optimization of cell yield and sorption capacity --- p.72
Chapter 4.1.5.1 --- Growth phase --- p.72
Chapter 4.1.5.1.1 --- Growth curve --- p.72
Chapter 4.1.5.1.2 --- Dye sorption capacity --- p.72
Chapter 4.1.5.2 --- Initial pH --- p.75
Chapter 4.1.5.2.1 --- Growth curve --- p.75
Chapter 4.1.5.2.2 --- Dye sorption capacity --- p.75
Chapter 4.1.5.3 --- Temperature --- p.75
Chapter 4.1.5.3.1 --- Growth curve --- p.75
Chapter 4.1.5.3.2 --- Dye sorption capacity --- p.79
Chapter 4.1.5.4 --- Glucose concentrations --- p.79
Chapter 4.1.5.4.1 --- Growth curve --- p.79
Chapter 4.1.5.4.2 --- Dye sorption capacity --- p.79
Chapter 4.1.6 --- Optimization of sorption process --- p.82
Chapter 4.1.6.1 --- Dry weight of sorbent --- p.82
Chapter 4.1.6.2 --- Temperature --- p.82
Chapter 4.1.6.3 --- Agitation rate --- p.86
Chapter 4.1.6.4 --- Salinity --- p.86
Chapter 4.1.6.5 --- Initial pH --- p.86
Chapter 4.1.6.6 --- Concentration of Procion Red MX-5B --- p.90
Chapter 4.1.6.7 --- Combination study of salinity and initial pH --- p.90
Chapter 4.2. --- Photocatalytic oxidation reaction --- p.94
Chapter 4.2.1 --- Effect of dry weight of immobilized cells of Vibrio sp. --- p.94
Chapter 4.2.1.1 --- Sorption --- p.94
Chapter 4.2.1.2 --- Photocatalytic oxidation --- p.96
Chapter 4.2.2 --- Effect of UV intensities --- p.96
Chapter 4.2.3 --- Effect of TiO2 concentrations --- p.96
Chapter 4.2.3.1 --- Sorption --- p.96
Chapter 4.2.3.2 --- Photocatalytic oxidation --- p.101
Chapter 4.2.4 --- Effect of H2O2 concentrations --- p.101
Chapter 4.2.5 --- Effect of the number of beads --- p.101
Chapter 4.2.5.1 --- Sorption --- p.105
Chapter 4.2.5.2 --- Photocatalytic oxidation --- p.105
Chapter 4.2.6 --- Effect of initial pH with and without the addition of --- p.105
Chapter 4.2.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.109
Chapter 4.2.8 --- Combinational study of UV intensities and H202 concentrations --- p.112
Chapter 4.2.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.112
Chapter 4.2.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L Ti02" --- p.112
Chapter 4.3 --- Biodegradation --- p.116
Chapter 4.3.1 --- Isolation of cyanuric acid-utilizing bacteria --- p.116
Chapter 4.3.2 --- Determination of cyanuric acid --- p.116
Chapter 4.3.3 --- Screening of Procion Red MX-5B sorption ability --- p.116
Chapter 4.3.4 --- Screening of cyanuric acid-utilizing ability --- p.116
Chapter 4.3.5 --- Bacterial identification --- p.118
Chapter 4.3.6 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.118
Chapter 4.3.7 --- Optimization of reaction conditions --- p.122
Chapter 4.3.7.1 --- Effect of salinity --- p.122
Chapter 4.3.7.2 --- Effect of cyanuric acid concentrations --- p.122
Chapter 4.3.7.3 --- Effect of temperature --- p.126
Chapter 4.3.7.4 --- Effect of agitation rate --- p.126
Chapter 4.3.7.5 --- Effect of initial pH --- p.132
Chapter 4.3.7.6 --- Effect of initial glucose concentration --- p.132
Chapter 4.3.7.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.132
Chapter 4.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.137
Chapter 4.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.137
Chapter 5. --- Discussion --- p.141
Chapter 5.1 --- Sorption --- p.141
Chapter 5.1.1 --- Isolation of Procion Red MX-5B-sorbing bacteria --- p.141
Chapter 5.1.2 --- Screening of Procion Red MX-5B sorption ability --- p.141
Chapter 5.1.3 --- Identification of isolated bacterium --- p.141
Chapter 5.1.4 --- Optimization of cell yield and sorption capacity --- p.142
Chapter 5.1.4.1 --- Growth phase --- p.142
Chapter 5.1.4.1.1 --- Growth curve --- p.142
Chapter 5.1.4.1.2 --- Dye sorption capacity --- p.143
Chapter 5.1.4.2 --- Initial pH --- p.146
Chapter 5.1.4.2.1 --- Growth curve --- p.146
Chapter 5.1.4.2.2 --- Dye sorption capacity --- p.146
Chapter 5.1.4.3 --- Temperature --- p.146
Chapter 5.1.4.3.1 --- Growth curve --- p.146
Chapter 5.1.4.3.2 --- Dye sorption capacity --- p.147
Chapter 5.1.4.4 --- Glucose concentrations --- p.147
Chapter 5.1.4.4.1 --- Growth curve --- p.147
Chapter 5.1.4.4.2 --- Dye sorption capacity --- p.147
Chapter 5.1.5 --- Optimization of sorption process --- p.148
Chapter 5.1.5.1 --- Dry weight of sorbent --- p.148
Chapter 5.1.5.2 --- Temperature --- p.148
Chapter 5.1.5.3 --- Agitation rate --- p.149
Chapter 5.1.5.4 --- Salinity --- p.149
Chapter 5.1.5.5 --- Initial pH --- p.150
Chapter 5.1.5.6 --- Concentration of Procion Red MX-5B (MX-5B) --- p.152
Chapter 5.1.5.7 --- Combination study of salinity and initial pH --- p.153
Chapter 5.2. --- Photocatalytic oxidation reaction --- p.153
Chapter 5.2.1 --- Effect of immobilized cells of Vibrio sp. --- p.153
Chapter 5.2.1.1 --- Sorption --- p.153
Chapter 5.2.1.2 --- Photocatalytic oxidation --- p.154
Chapter 5.2.2 --- Effect of UV intensities --- p.155
Chapter 5.2.3 --- Effect of TiO2 concentrations --- p.155
Chapter 5.2.3.1 --- Sorption --- p.155
Chapter 5.2.3.2 --- Photocatalytic oxidation --- p.156
Chapter 5.2.4 --- Effect of H2O2 concentrations --- p.156
Chapter 5.2.5 --- Effect of the number of beads --- p.157
Chapter 5.2.5.1 --- Sorption --- p.157
Chapter 5.2.5.2 --- Photocatalytic oxidation --- p.158
Chapter 5.2.6 --- Effect of initial pH with and without the addition of --- p.158
Chapter 5.2.7 --- Control experiments for photocatalytic oxidation of Procion Red MX-5B --- p.160
Chapter 5.2.8 --- Combinational study of UV intensities and H202 concentrations --- p.161
Chapter 5.2.9 --- Photocatalytic oxidation of Procion Red MX-5B under optimal conditions --- p.161
Chapter 5.2.10 --- "Sorption isotherms of calcium alginate beads immobilized with 70 mg Vibrio sp. and 5,000 mg/L Ti02" --- p.161
Chapter 5.3 --- Biodegradation --- p.162
Chapter 5.3.1 --- Isolation of cyanuric acid-utilizing bacteria --- p.162
Chapter 5.3.2 --- Determination of cyanuric acid --- p.163
Chapter 5.3.3 --- Screening of Procion Red MX-5B sorption ability --- p.163
Chapter 5.3.4 --- Screening of cyanuric acid-utilizing ability --- p.163
Chapter 5.3.5 --- Bacterial identification --- p.163
Chapter 5.3.6 --- Growth and cyanuric acid removal efficiency of the selected bacterium --- p.164
Chapter 5.3.7 --- Optimization of reaction conditions --- p.165
Chapter 5.3.7.1 --- Effect of salinity --- p.165
Chapter 5.3.7.2 --- Effect of cyanuric acid concentration --- p.165
Chapter 5.3.7.3 --- Effect of temperature --- p.166
Chapter 5.3.7.4 --- Effect of agitation rate --- p.167
Chapter 5.3.7.5 --- Effect of initial pH --- p.167
Chapter 5.3.7.6 --- Effect of initial glucose concentration --- p.167
Chapter 5.3.7.7 --- Combinational study of glucose and cyanuric acid concentrations --- p.168
Chapter 5.4 --- Detection of cyanuric acid formed in photocatalytic oxidation reaction --- p.170
Chapter 5.5 --- "Integration of sorption, photocatalytic oxidation and biodegradation" --- p.171
Chapter 5.6 --- Recommendations --- p.171
Chapter 6. --- Conclusions --- p.173
Chapter 7. --- References --- p.175
Appendix --- p.200

Cheng Yee Wan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 95-112).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstract --- p.ii
Table of Contents --- p.vi
List of Figures --- p.xi
List of Plates --- p.xiv
List of Tables --- p.xvi
Abbreviations --- p.xviii
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Legionella pneumophila --- p.1
Chapter 1.1.1 --- Bacterial morphology and ultrastructure --- p.2
Chapter 1.1.2 --- Microbial ecology and natural habitats --- p.4
Chapter 1.1.2.1 --- Association with amoeba --- p.5
Chapter 1.1.2.2 --- Association with biofilm --- p.5
Chapter 1.2 --- Legionnaires' disease and clinical significance --- p.6
Chapter 1.2.1 --- Epidemiology --- p.6
Chapter 1.2.1.1 --- Worldwide distribution --- p.6
Chapter 1.2.1.2 --- Local situation --- p.7
Chapter 1.2.2 --- Clinical presentation --- p.7
Chapter 1.2.3 --- Route of infection and pathogenesis --- p.8
Chapter 1.2.4 --- Diagnosis --- p.10
Chapter 1.2.4.1 --- Culture of Legionella --- p.10
Chapter 1.2.4.2 --- Direct fluorescent antibody (DFA) staining --- p.13
Chapter 1.2.4.3 --- Serologic tests --- p.13
Chapter 1.2.4.4 --- Urine antigen testing --- p.14
Chapter 1.2.4.5 --- Detection of Legionella nucleic acid --- p.15
Chapter 1.2.5 --- Risk factors --- p.15
Chapter 1.2.6 --- Treatment for Legionella infection --- p.16
Chapter 1.3 --- Detection of Legionella in environment --- p.16
Chapter 1.4 --- Disinfection methods --- p.17
Chapter 1.4.1 --- Physical methods --- p.19
Chapter 1.4.1.1 --- Filtration --- p.19
Chapter 1.4.1.2 --- UV-C irradiation --- p.20
Chapter 1.4.1.3 --- Thermal eradication (superheat-and-flush) --- p.21
Chapter 1.4.2 --- Chemical methods --- p.21
Chapter 1.4.2.1 --- Chlorination --- p.21
Chapter 1.4.2.2 --- Copper-silver ionization --- p.22
Chapter 1.4.3 --- Effect of biofilm and other factors on disinfection --- p.23
Chapter 1.5 --- Photocatalytic oxidation (PCO) --- p.24
Chapter 1.5.1 --- Generation of strong oxidants --- p.24
Chapter 1.5.2 --- Disinfection mechanism(s) --- p.27
Chapter 1.5.3 --- Major factors affecting the process --- p.28
Chapter 2. --- Objectives --- p.30
Chapter 3. --- Materials and Methods --- p.31
Chapter 3.1 --- Chemicals --- p.31
Chapter 3.2 --- Bacterial strains and culture --- p.31
Chapter 3.3 --- Photocatalytic reactor --- p.33
Chapter 3.4 --- PCO efficacy tests --- p.33
Chapter 3.5 --- PCO sensitivity tests --- p.35
Chapter 3.6 --- Optimisation of PCO conditions --- p.35
Chapter 3.6.1 --- Optimization of TiO2 concentration --- p.36
Chapter 3.6.2 --- Optimization of UV intensity --- p.36
Chapter 3.6.3 --- Optimization of depth of reaction mixture --- p.36
Chapter 3.6.4 --- Optimization of stirring rate --- p.37
Chapter 3.6.5 --- Optimization of initial pH --- p.37
Chapter 3.6.6 --- Optimization of treatment time and initial cell concentration --- p.37
Chapter 3.6.7 --- Combinational optimization --- p.37
Chapter 3.7 --- Transmission electron microscopy (TEM) --- p.38
Chapter 3.8 --- Fatty acid profile analysis --- p.40
Chapter 3.9 --- Total organic carbon (TOC) analysis --- p.42
Chapter 3.10 --- UV-C irradiation --- p.44
Chapter 3.11 --- Hyperchlorination --- p.44
Chapter 3.12 --- Statistical analysis and replication --- p.45
Chapter 3.13 --- Safety precautions --- p.45
Chapter 4. --- Results --- p.46
Chapter 4.1 --- Efficacy test --- p.46
Chapter 4.2 --- PCO sensitivity --- p.47
Chapter 4.3 --- Optimization of PCO conditions --- p.48
Chapter 4.3.1 --- TiO2 concentration --- p.48
Chapter 4.3.2 --- UV intensity --- p.48
Chapter 4.3.3 --- Depth of reaction mixture --- p.51
Chapter 4.3.4 --- Stirring rate --- p.56
Chapter 4.3.5 --- Effect of initial pH --- p.56
Chapter 4.3.6 --- Effect of treatment time and initial concentrations --- p.56
Chapter 4.3.7 --- Combinational effects --- p.63
Chapter 4.4 --- Transmission electron microscopy (TEM) --- p.66
Chapter 4.4.1 --- Morphological changes induced by PCO --- p.66
Chapter 4.4.2 --- Comparisons with changes caused by UV-C irradiation and chlorination --- p.67
Chapter 4.5 --- Fatty acid profile analysis --- p.71
Chapter 4.6 --- Total organic carbon (TOC) analysis --- p.73
Chapter 4.7 --- UV-C irradiation --- p.74
Chapter 4.8 --- Hyperchlorination --- p.74
Chapter 5. --- Discussion --- p.76
Chapter 5.1 --- Efficacy test --- p.76
Chapter 5.2 --- PCO sensitivity --- p.76
Chapter 5.3 --- Optimization of PCO conditions --- p.77
Chapter 5.3.1 --- Effect of TiO2 concentration --- p.77
Chapter 5.3.2 --- Effect of UV intensity --- p.78
Chapter 5.3.3 --- Effect of depth of reaction mixture --- p.79
Chapter 5.3.4 --- Effect of stirring rate --- p.79
Chapter 5.3.5 --- Effect of initial pH --- p.80
Chapter 5.3.6 --- Effect of treatment time and initial concentrations --- p.81
Chapter 5.3.7 --- Combinational effect --- p.82
Chapter 5.4 --- Transmission electron microscopy (TEM) --- p.83
Chapter 5.4.1 --- Morphological changes induced by PCO --- p.83
Chapter 5.4.2 --- Comparisons with changes caused by UV-C irradiation and chlorination --- p.85
Chapter 5.5 --- Fatty acid profile analysis --- p.85
Chapter 5.6 --- Total organic carbon (TOC) analysis --- p.86
Chapter 5.7 --- Comparisons of the three disinfection methods --- p.88
Chapter 6. --- Conclusion --- p.91
Chapter 7. --- References --- p.95
Chapter 8. --- Appendix --- p.113

by Chan Shuk Mei.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references (leaves 138-149).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstracts --- p.ii
Contents --- p.vi
List of figures --- p.xi
List of plates --- p.xiv
List of tables --- p.xv
Abbreviations --- p.xvi
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Pentachlorophenol --- p.1
Chapter 1.1.1 --- Characteristics of pentachlorophenol --- p.1
Chapter 1.1.2 --- Application of pentachlorophenol --- p.4
Chapter 1.1.3 --- The fate of pentachlorophenol in environment --- p.5
Chapter 1.1.4 --- The toxicity of pentachlorophenol --- p.9
Chapter 1.1.5 --- Remediation of pentachlorophenol --- p.13
Chapter 1.1.5.1 --- Physical treatment
Chapter 1.1.5.2 --- Chemical treatment
Chapter 1.1.5.3 --- Biological treatment
Chapter 1.1.5.4 --- Alternative for combining two treatments
Chapter 1.2 --- Biosorbents --- p.18
Chapter 1.2.1 --- Chitin and chitosan --- p.21
Chapter 1.2.1.1 --- History of chitin and chitosan --- p.21
Chapter 1.2.1.2 --- Structures of chitin and chitosan --- p.21
Chapter 1.2.1.3 --- Sources of chitin and chitosan --- p.23
Chapter 1.2.1.4 --- Application of chitin and chitosan --- p.26
Chapter 1.2.1.5 --- Study on PCP removal by chitinous material --- p.28
Chapter 1.2.2 --- Factors affecting biosorption --- p.29
Chapter 1.2.2.1 --- Solution pH --- p.29
Chapter 1.2.2.2 --- Concentration of biosorbent --- p.30
Chapter 1.2.2.3 --- Retention time --- p.31
Chapter 1.2.2.4 --- Temperature --- p.32
Chapter 1.2.2.5 --- Agitation rate --- p.32
Chapter 1.2.2.6 --- Initial sorbate concentration --- p.33
Chapter 1.2.3 --- Modeling of biosorption --- p.33
Chapter 1.2.3.1 --- Langmuir adsorption model --- p.34
Chapter 1.2.3.2 --- Freundlich adsorption model --- p.34
Chapter 1.3 --- Photocatalytic degradation --- p.35
Chapter 1.3.1 --- Titanium dioxide --- p.36
Chapter 1.3.2 --- Mechanism of photocatalytic oxidation using photocatalyst TiO2 --- p.36
Chapter 1.3.3 --- Advantages of photocatalytic oxidation with Ti02 and H2O2 --- p.41
Chapter 1.3.4 --- Degradation of PCP by photocatalytic oxidation --- p.41
Chapter 2. --- Objectives --- p.45
Chapter 3. --- Materials and methods --- p.46
Chapter 3.1 --- Biosorbents --- p.46
Chapter 3.1.1 --- Production of biosorbents --- p.46
Chapter 3.1.2 --- Scanning electron microscope of biosorbents --- p.48
Chapter 3.1.3 --- Pretreatment of biosorbents --- p.48
Chapter 3.2 --- Pentachlorophenol preparation --- p.48
Chapter 3.3 --- Batch biosorption experiment --- p.48
Chapter 3.3.1 --- Quantification of pentachlorophenol by HPLC --- p.51
Chapter 3.3.2 --- Data analysis for biosorption --- p.51
Chapter 3.3.3 --- Selection of optimal conditions for batch PCP adsorption --- p.52
Chapter 3.3.3.1 --- Effect of initial pH and biosorbent concentration --- p.52
Chapter 3.3.3.2 --- Improvement on pH effect and biosorbent concentration --- p.52
Chapter 3.3.3.3 --- Effect of temperature --- p.53
Chapter 3.3.3.4 --- Effect of agitation rate --- p.53
Chapter 3.3.4 --- Effect of initial PCP concentration and biosorbent concentration --- p.53
Chapter 3.3.4.1 --- Adsorption isotherm --- p.54
Chapter 3.4 --- Photocatalytic oxidation --- p.54
Chapter 3.4.1 --- Reaction mixture solution --- p.54
Chapter 3.4.2 --- Photocatalytic reactor --- p.55
Chapter 3.4.3 --- Batch photocatalytic oxidation system --- p.55
Chapter 3.4.4 --- Selection of extraction solvent --- p.59
Chapter 3.4.5 --- Extraction efficiency --- p.59
Chapter 3.4.6 --- Data analysis for PCO --- p.60
Chapter 3.4.7 --- Irradiation time --- p.60
Chapter 3.4.8 --- Determination of hydrogen peroxide concentration --- p.61
Chapter 3.4.9 --- Effect of biosorbent concentration in PCO --- p.61
Chapter 3.4.10 --- Effect of PCP amount on biosorbent in PCO --- p.61
Chapter 3.4.11 --- Determination of chloride ion concentration and total organic carbon during PCO --- p.62
Chapter 3.4.12 --- Identification the intermediates of PCP degradation by PCO --- p.62
Chapter 3.4.13 --- Evaluation of the change of PCO treated biosorbents --- p.63
Chapter 3.4.13.1 --- Chitin assay --- p.64
Chapter 3.4.13.2 --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.64
Chapter 3.4.13.3 --- Protein assay --- p.66
Chapter 3.4.13.4 --- Biosorption efficiency --- p.66
Chapter 3.4.14 --- Multiple biosorption and PCO cycles of PCP --- p.66
Chapter 3.4.15 --- Evaluation for the toxicity change of PCP adsorbed biosorbents during PCO --- p.67
Chapter 4. --- Results --- p.68
Chapter 4.1 --- Batch biosorption experiment --- p.68
Chapter 4.1.1 --- Selection of optimal conditions for batch PCP adsorption --- p.68
Chapter 4.1.1.1 --- Effect of initial pH and biosorbent concentration --- p.68
Chapter 4.1.1.2 --- Effect of Tris buffer and biosorbent concentrations --- p.73
Chapter 4.1.1.3 --- Effect of temperature --- p.73
Chapter 4.1.1.4 --- Effect of agitation rate --- p.73
Chapter 4.1.2 --- Effect of initial PCP concentration and biosorbent concentration --- p.81
Chapter 4.1.2.1 --- Adsorption isotherm --- p.82
Chapter 4.2 --- Photocatalytic oxidation --- p.88
Chapter 4.2.1 --- Selection of extraction solvent --- p.88
Chapter 4.2.2 --- Determination of hydrogen peroxide concentration --- p.88
Chapter 4.2.3 --- Effect of biosorbent concentration in PCO --- p.88
Chapter 4.2.4 --- Effect of PCP amount on biosorbent in PCO --- p.94
Chapter 4.2.5 --- Determination of chloride ion concentration and total organic carbon during PCO --- p.98
Chapter 4.2.6 --- Identification the intermediates of PCP degradation by PCO --- p.102
Chapter 4.2.7 --- Evaluation of the change of PCO treated biosorbents --- p.102
Chapter 4.2.7.1 --- Chitin assay --- p.102
Chapter 4.2.7.2 --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.102
Chapter 4.2.7.3 --- Protein assay --- p.102
Chapter 4.2.7.4 --- Biosorption efficiency --- p.109
Chapter 4.2.8 --- Multiple biosorption and PCO cycles of PCP --- p.109
Chapter 4.2.9 --- Evaluation for the toxicity change of PCP adsorbed biosorbents during PCO --- p.109
Chapter 5. --- Discussion --- p.115
Chapter 5.1 --- Batch biosorption experiment --- p.115
Chapter 5.1.1 --- Selection of optimal conditions for batch PCP adsorption --- p.115
Chapter 5.1.1.1 --- Effect of initial pH --- p.115
Chapter 5.1.1.2 --- Effect of Tris buffer and biosorbent concentrations --- p.118
Chapter 5.1.1.3 --- Retention time --- p.119
Chapter 5.1.1.4 --- Effect of temperature --- p.120
Chapter 5.1.1.5 --- Effect of agitation rate --- p.121
Chapter 5.1.2 --- Effect of initial PCP concentration and biosorbent concentration --- p.121
Chapter 5.1.2.1 --- Modeling of biosorption --- p.122
Chapter 5.2 --- Photocatalytic oxidation --- p.123
Chapter 5.2.1 --- Selection of extraction solvent --- p.124
Chapter 5.2.2 --- Determination of hydrogen peroxide concentration --- p.124
Chapter 5.2.3 --- Effect of biosorbent concentration in PCO --- p.125
Chapter 5.2.4 --- Effect of PCP amount on biosorbent in PCO --- p.127
Chapter 5.2.5 --- Determination of chloride ion concentration and total organic carbon during PCO --- p.127
Chapter 5.2.6 --- Identification the intermediates of PCP degradation by PCO --- p.128
Chapter 5.2.7 --- Evaluation of the change of PCO treated biosorbents --- p.128
Chapter 5.2.7.1 --- Chitin assay --- p.129
Chapter 5.2.7.2 --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.129
Chapter 5.2.7.3 --- Protein assay --- p.131
Chapter 5.2.7.4 --- Biosorption efficiency --- p.131
Chapter 5.2.8 --- Multiple biosorption and PCO cycles of PCP --- p.132
Chapter 5.2.9 --- Evaluation for the toxicity change of PCP adsorbed biosorbents during PCO --- p.132
Chapter 6. --- Conclusion --- p.134
Chapter 7. --- Recommendation --- p.137
Chapter 8. --- References --- p.138

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology
Water pollution caused by organic and inorganic contaminants represents an important ecological and health hazard. Simultaneous treatment of organic and inorganic contaminants had gradually gained great scientific interest. Advanced oxidation processes such as photocatalysis, using TiO2 as a photocatalyst, have been shown to be very robust in the removal of biorecalcitrant pollutants. These methods offer the advantage of removing the pollutants, in contrast to conventional techniques. At present, the main technical challenge that hinder its commercialization remained on the post-recovery of the photocatalyst particles after water treatment. Supporting of the photocatalyst on the adsorbent surface is important as it assists during the filtration step, reducing losses of the materials and yielding better results in degrading pollutants. To overcome this challenge, in this study composite photocatalysts of TiO2/zeolite and TiO2/silica were prepared and investigated to explore the possible application in the simultaneous removal of organic and inorganic compounds from contaminated water. The main objective of this study was to investigate the heterogeneous photocatalytic degradation of organic compounds in the presence of metal ions using composite photocatalysts. The Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy and Energy Dispersive X-ray (SEM-EDX), Raman spectroscopy (RS) and zeta potential (ZP) analyses were used to characterize the prepared composite photocatalysts. The successive composite photocatalysts were used in a semi-batch reactor under an irradiation intensity of 5.5 mW/m2 (protected by a quartz sleeve) at 25 ± 3°C for the photocatalytic degradation of synthetic textile (methyl orange) and agricultural (atrazine) wastewater in the presence of ions. The effect of operating parameters such as TiO2 composition on supporting material, particle size, composite photocatalyst loading, initial pollutant concentration and pH were optimized. The effects of inorganic salts and humic acid on dye and pesticides degradation were also studied, respectively. The performance of the photocatalyst reactor was evaluated on the basis of color removal, metal ion reduction, total organic carbon (TOC) reduction, intermediates product analysis and modeling of kinetics and isotherms. Different kinetic and isotherm models were introduced and applied in this work. Important aspects such as error functions with the optimal magnitude were used for the selection of the best suitable model.
European Union. City of Mikkeli, Finland. Water Research Commission (RSA)

碩士
國立臺灣科技大學
營建工程系
94
Nano photocatalyst is applied on the proposed water purification device in this research. The device is located on the roof of the building by using the nature power of sun to perform the reaction of nano photocatalyst. A series of testing is designed in this research to investigate the proposed device which included the parameter of climate, contact area of nano photocatalyst, density of pollutant. The result showed the higher the intensity of sun power, the higher of the capability of purification. Higher contact area induced higher capability of purification from nano photocatalyst. The higher density of pollutant induced the higher purification. The device is going to apply a pattern for commercial purpose.

M. Tech. (Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.
Advanced oxidation processes (AOPs) are supposedly effective means for removal of low concentration of organic pollutants from waste water as compared to conventional treatment methods. However, TiO2 metal semiconductor is the most promising photocatalyst for degradation of organic pollutant under heterogeneous photocatalysis as compared to other metal semiconductors. Challenges such as aggregation in solution, low adsorptive ability for non-polar organic contaminants and recycling are limitations in application of TiO2 for commercial purposes. The other limitations of TiO2, is it only utilizes 4-6% of the solar energy reaching the earth's surface which is in the UV region and also rapid electron-hole recombination due its wide band gap. In this work, the limitations are overcome by synthesis of a new photocatalyst material and further applied on degradation of model organic contaminants. The first part of this work focused on preparation and characterization of photocatalyst material. The photocatalyst synthesized were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and UV-VIS diffuse reflectance spectrophotometer (DRUV-VIS). Supporting characterization techniques revealed partly dispersion of TiO2 within the cavities of dealuminated Clinoptilolite (HCP). TiO2 exist as nanoparticles or clusters on the HCP surface ascribed to lower loading of TiO2. XRD analysis showed that the support material employed was mainly Clinoptilolite and absorption band of prepared photocatalyst was red-shifted into the visible region, with slight reduction in band gap of photocatalyst. The second part focused on adsorption and photocatalytic degradation of methyl orange solution (MO) conducted under UV-irradiation in the presence of TiO2/HCP. The influence of operational parameters on degradation efficiency of photocatalyst material on MO was carried out in this study. Parameters such as initial dye concentration, pH, calcination temperature, inorganic anions and peroxide concentration were varied during degradation activities of MO. Comparative degradation efficiency of TiO2/HCP, TiO2 and HCP were conducted on dye mixture (Methyl orange and Methylene Blue) under UV irradiation. Kinetic analysis employing Langmuir-Hinshelwood model on dependencies of organic contaminants degradation was also conducted at different operational parameters. The adsorption capacity of MO was highest in the presence of TiO2/HCP at lower loading, which is ascribed to good dispersion of TiO2 on HCP and increased surface area of dealuminated Clinoptilolite. The photocatalytic degradation of methyl orange in the presence of TiO2/HCP was optimized at low dye concentration (30 ppm), acidic condition (pH 4), and calcination temperature of 873 K. Nitrate ion of Sodium salt accelerates degradation activities on methyl orange as compared to other inorganic anions. Photocatalytic degradation of methyl orange was greatly enhanced upon addition of oxidant (H2O2) and the photocatalyst possessed good repeatability after 3 cycles. TiO2/HCP exhibit highest degradation activities, followed by HCP as compared to TiO2 during the degradation of dye mixture. The degradation of MO by the photocatalyst fits into pseudo-first order kinetic model, while for comparative analysis of photocatalyst on dye mixtures follows second order kinetic model.