QCM sensor is a response to a kind of broad spectrum, high sensitivity, and simple structure, low-cost detection device, and particularly its quality as a type of gas sensor is widely used. With the successful oscillation in liquid phase, QCM sensor has been involved in the application analytical chemistry, surface chemistry, biochemistry and environmental monitoring side and many other scientific fields. With sensitive surface film as the sensitive element, AT-cut quartz crystal as energy transducer components by changes of the relationship between mass of surface film and frequency of QCM sensor transduces signals of mass or concentration into output frequency signal of sensor, thus achieve changes of mass or concentration detection. This paper mainly states how to design a low-cost QCM system platform with Arduino microcontroller board based on QCM sensor specific properties. For the oscillator circuit selection and differential frequency circuit design, the shield board has properly matched Arduino Mega2560, then by programming code to make Arduino acquire frequency of QCM sensor in real-time. Meanwhile, the interface and data store are corresponding convenient for real- time observing and data post-processing. By the tests of anhydrous ethanol evaporation, QCM system platform was calibrated and Sauerbrey equation verification. Moreover, this paper studies that photocatalytic degradation processing of Rhodamine B (RB) and methyl orange solution at the Surface of nanocrystalline TiO2 by QCM sensor.

Titanium Dioxide (TiO2) emerged as one of the most popular photocatalysts since 1970's. However, its photocatalytic activity requires UV irradiation due to its large band gap unless further functionalization or modifications are performed. Furthermore, recovery issue has always been a major drawback, if the more effective form nano particles are utilized. The key objectives of this research were synthesizing new TiO2 based photocatalyst systems that are effective with both the UV and the visible light while utilizing novel superior environmentally friendly techniques enabling development of nano-structured photocatalysts that can be easily recovered. In this dissertation research, highly porous nano-structured TiO2/WO3/Fe3+ aerogel composite photocatalyst are prepared, characterized, and tested for model photocatalytic reactions. The photocatalyst structure is tailored to capture environmental pollutants and enable their decomposition in-situ under both UV and visible light through photodecomposition to smaller benign substances. A novel and green method is applied to prepare unique surfactant templated aerogel photocatalysts with highly porous nano-structure, high surface area, and tailored pore size distribution. Sol-gel process followed by supercritical fluids extraction and drying allowed synthesis of highly porous composite TiO2/WO3 aerogel. The surfactant template was completely removed with the aid of a supercritical solvent mixture followed with heat treatment. Fe3+ ion was incorporated within the composite aerogel photocatalyst as dopant either at the sol-gel co-precipitation step or at a subsequent supercritical impregnation process. Supercritical drying followed with heat treatment results in titanium dioxide with the most profound anatase crystal structure. Neutral templates were used to further enhance retention and tuning of the nano-pore structure and the surface properties. The Nitrogen adsorption-desorption isotherms methods were used to follow the removal of solvents and templates as well as tracking the textural properties of the synthesized aerogel. Surfactant-templated aerogels, which show remarkable thermal stability and uniform pore size distribution, exhibit specific surface areas three times more than the highly optimized commercial nano-particles, industry standard TiO2 photocatalyst Degussa P-25, even after heat treatment. The synthesized catalysts were characterized by using SEM, FIB, EDS, XRD, XPS and porosimetry prior to post photocatalytic activity evaluation through a model photocatalytic reaction. The band gaps of the catalysts were also determined by using diffuse reflectance spectroscopy. The model reaction employed Methylene Blue (MB) photo-oxidation under UV and visible light. Resulting aerogel TiO2/WO3/Fe3+ photocatalyst exhibited comparable photocatalytic capability to Degussa P25 under UV light exposure and offered much superior photocatalytic capability under visible light exposure.

Made available in DSpace on 2014-06-11T19:30:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-22Bitstream added on 2014-06-13T20:40:10Z : No. of bitstreams: 1 kataoka_fp_me_bauru.pdf: 2231157 bytes, checksum: 41333d9fadeec00b484d0df4442b5ebd (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Os problemas ambientais gerados pelo crescimento das atividades humanas e industriais têm aumentado a necessidade pelo desenvolvimento de tecnologias alternativas para a remediação de sistemas aquáticos contaminados. A fotocatálise heterogênea, utilizando dióxido de titânio, tem se mostrado eficiente neste aspecto. Neste trabalho, foram sintetizadas nanoestruturas de TiO2 utilizando como precursor o isopropóxito de titânio pela rota hidrotérmica. Os materiais obtidos foram caracterizados por DRX, FT-Raman, FTIR, BET e MEV. A fim de avaliar a atividade fotocatalítica das amostras produzidas, foram realizados testes de degradação do corante rodomina B sob irradiação UV, luz branca e luz solar. A medida da degradação da molécula foi mensurada por espectroscopia UV-Vis. Os resultados das caracterizações mostraram que a rota de síntese utilizada foi eficiente na produção de nanoestruturas cristalinas de TiO2 com morfologias diferentes e os ensaios de degradação revelaram que a propriedade fotocatalítica dos materiais esta diferente relacionada com a morfologia, a área superficial e a presença de grupos químicos ligados à superfície / The environmental problems generated by tye growth of human and industrial activities have increased the need for the development of alternative technologies for the remediation of contaminated aquatic systems. The heterogeneous photocatalysis using titanium dioxide, has been show effective in this respect. In this work, nanoestructures have been synthesized as a precursor of TiO2 using titanium isopropóxido by the hydrothermal route. The materials were characterized by XRD, FT-Raman, FTIR, BET and SEM. In order to evaluate the photocatalytic activity of the samples produced, tests were performed using degradation of the dye rhodamine B under UV, white light and sunlight. The measurements of the degradation of the molecule was measured by UV-Vis spectroscopy. The results of the characterizations showed that the synthetic route used was efficient in the production of crystalline nanostructured TiO2 with different morphologies and degradation testing revealed that the photocatalytic properties of materials is directly associated to the morphology, surface area and the presence of chemical groups bound to the surface

This work investigates the elimination of new and emerging microcontaminants (EMs) from water by means of photochemical oxidation processes, namely heterogeneous and homogeneous photocatalysis. Representative compounds of artificial sweeteners (saccharin, SAC), endocrine disruptors (bisphenol-A, BPA), and pharmaceutica ls (antipyrine, AP) of high environmental persistence and widespread occurrence in the water cycle are used as case studies. Novel concepts that can make photochemica l oxidation a more cost-effective and environmentally benign technology are tested. In Chapter 4, the photocatalytic treatment of SAC and BPA is investigated. Novel submicronic anatase-rutile nanocomposite particles with tuned phase ratio are used as catalysts to increase the photocatalytic performance under UVA irradiation. At the best-assayed conditions (C0 = 3 mg/L, catalyst = 400 mg/L), SAC and BPA are completely degraded within 90 and 150 min of photocatalytic treatment, respectively. [variables: anatase-rutile ratio; initial substrate concentration; catalyst concentration; catalyst reuse; sonication during catalyst recovery] In Chapter 5, a UVA light-emitting diode (UVA-LED) and sunlight are used as irradiation sources to reduce energy requirements and environmental impacts of photocatalytic processes. The photocatalytic degradation of SAC and BPA is studied under UVA irradiation provided by either a UVA-LED or a conventional fluoresce nt blacklight UVA lamp (UVA-BL) and solar irradiation. At the best-assayed conditions (C0 = 2.5 mg/L, TiO2 = 250 mg/L), BPA is completely degraded within 20, 30, and 120 min under UVA-LED, solar, and UVA-BL irradiation, respectively. The treatment time required for the complete elimination of SAC is 20 min under UVA-LED and 90 min under UVA-BL irradiation. [variables: initial substrate concentration; catalyst concentration; water matrix; light source; reactor configuration] In Chapter 6, a comparative study is carried out among the photocatalytic systems of Chapters 4 and 5 in terms of EMs removal, photonic and energy efficiencies. Technica l and economic aspects of all the processes are assessed. LED-driven photocatalysis achieves the highest efficiency in terms of organic removal with the minimum energy consumption, rendering it the most sustainable technology for the treatment of EMs. In Chapter 7, olive mill wastewater (OMW) is used as an iron-chelating agent in the photo-Fenton reaction to obviate the need for water acidification at pH 2.8. Conventional, OMW- and EDDS-assisted photo-Fenton treatment is applied for SAC degradation in a solar compound parabolic collector (CPC). It was found that OMW forms iron complexes able to catalyse H2O2 decomposition and generate hydroxyl radicals. At the optimal OMW dilution (1:800), 90% of SAC is degraded within 75 min. [variables: pH; iron-chelating agent; initial SAC concentration; OMW dilution] In Chapter 8, other complexing and oxidising agents, namely oxalate and persulfate, are used for the intensification of AP degradation during UVA-LED photo-Fenton treatment. Neural networks are applied for process modelling and optimisation. At the optimal conditions (hydrogen peroxide = 100 mg/L, ferrous iron = 20 mg/L, oxalic acid = 100 mg/L), complete degradation of AP and 93% mineralisation is achieved within 2.5 and 60 min, respectively. [variables: initial concentration of hydrogen peroxide, ferrous iron, oxalic acid, persulfate] It is concluded that LED-driven photocatalysis is a sustainable technology for the elimination of EMs from water. Results from this work highlight the need for development and optimisation of engineering proper LED reactors. Furthermore, this work introduces a new concept towards the sustainable operation of photo-Fenton that is based on the use of wastewaters rich in polyphenols instead of pricey and hazardous chemicals for iron chelation. The addition of ferrioxalate complexes is proposed for the intensification of EMs mineralisation during UVA-LED photo-Fenton treatment. Finally, the findings of this work encourage the use of chemometric tools as predictive and optimisation tools.

Pollution created by textile dyeing operations attracts significant attention because an effluent containing a complex mixture of coloured and potentially toxic compounds can be released with the discharged water. Developing dyes and dyeing conditions to reduce the amount of residual dye contained in any effluent has been one of many approaches to minimise this environmental impact. However, the presence of coloured discharge cannot be totally eliminated using only this strategy. Thus, development of efficient post-dyeing wastewater treatment methods capable of removing coloured products from the water is of paramount importance. TiO2-mediated photocatalytic degradation of organic dye molecules via oxidation is the focus of the study reported in this thesis. TiO₂ significantly increases the rate of photodegradation of a wide range of organic dyes under mild operating conditions, and is able to mineralise a wide spectrum of organic contaminants. TiO₂ is also one of the very few substances appropriate for the industrial applications. One of primary aims of this thesis is to test the hypothesis that augmenting standard TiO₂ photocatalysts with Au nanoparticles could increase performance of a catalyst, while immobilizing TiO₂ on SiO₂ support may improve the cost of the process efficiency, i.e. more photocatalytic degradation per particle of TiO₂. Combining TiO₂ doped with gold nanoparticles on SiO₂ support has the potential to provide the highest photocatalytic ability at the lowest cost. The first half of the thesis is concerned with establishing and optimizing experimental conditions for monitoring photodegradation via UV-Visible spectroscopy. Effects of various conditions such as temperature, sequence of addition of reagents, exposure to light vs. experiments in dark, sampling methods, and the use of quenching agent were examined. The main conclusions from this study are that light-induced photodegradation using titanium dioxide nanoparticles catalysts is comparatively more efficient than purely chemical catalytic (e.g. non-light mediated) degradation, even if the latter is performed at elevated temperature. Further, the rate of dye degradation is affected considerably by the parameters of the system. The degradation rate depends strongly on the pH of the solution, due to charges on both the catalyst surface and in the dye. In general, at pH ≤ 6.8, which is the zero charge point for TiO₂, reactions proceeded faster than those at higher pH. Six dyes from four different classes of dyes used in industry were used in this study, and all showed different photodegradation behaviour. The second half of thesis tests the photocatalytic abilities of various TiO₂-based catalysts: pure TiO₂ (commercial and custom-made in our laboratory), TiO₂-supported gold nanoparticles (Au/TiO₂), SiO₂-supported TiO₂ (TiO₂/SiO₂), and SiO₂-supported Au/TiO₂. The best photocatalytic performance was observed for the custom-made TiO₂ code-named as e-TiO₂, which was synthesized using the sol-gel method in dry ethanol. TiO₂-supported Au55 nanoparticles showed a similar level of catalytic ability but are significantly more expensive. It was observed that dye adsorption played a significant role in the case of SiO₂-immobilized photocatalysts.

Orientador: Fenelon Martinho Lima Pontes / Banca: Alejandra Hortencia Miranda González / Banca: Alberthmeiry Teixeira de Figueiredo / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi / Resumo: Os problemas ambientais gerados pelo crescimento das atividades humanas e industriais têm aumentado a necessidade pelo desenvolvimento de tecnologias alternativas para a remediação de sistemas aquáticos contaminados. A fotocatálise heterogênea, utilizando dióxido de titânio, tem se mostrado eficiente neste aspecto. Neste trabalho, foram sintetizadas nanoestruturas de TiO2 utilizando como precursor o isopropóxito de titânio pela rota hidrotérmica. Os materiais obtidos foram caracterizados por DRX, FT-Raman, FTIR, BET e MEV. A fim de avaliar a atividade fotocatalítica das amostras produzidas, foram realizados testes de degradação do corante rodomina B sob irradiação UV, luz branca e luz solar. A medida da degradação da molécula foi mensurada por espectroscopia UV-Vis. Os resultados das caracterizações mostraram que a rota de síntese utilizada foi eficiente na produção de nanoestruturas cristalinas de TiO2 com morfologias diferentes e os ensaios de degradação revelaram que a propriedade fotocatalítica dos materiais esta diferente relacionada com a morfologia, a área superficial e a presença de grupos químicos ligados à superfície / Abstract: The environmental problems generated by tye growth of human and industrial activities have increased the need for the development of alternative technologies for the remediation of contaminated aquatic systems. The heterogeneous photocatalysis using titanium dioxide, has been show effective in this respect. In this work, nanoestructures have been synthesized as a precursor of TiO2 using titanium isopropóxido by the hydrothermal route. The materials were characterized by XRD, FT-Raman, FTIR, BET and SEM. In order to evaluate the photocatalytic activity of the samples produced, tests were performed using degradation of the dye rhodamine B under UV, white light and sunlight. The measurements of the degradation of the molecule was measured by UV-Vis spectroscopy. The results of the characterizations showed that the synthetic route used was efficient in the production of crystalline nanostructured TiO2 with different morphologies and degradation testing revealed that the photocatalytic properties of materials is directly associated to the morphology, surface area and the presence of chemical groups bound to the surface / Mestre

Made available in DSpace on 2016-08-19T12:56:49Z (GMT). No. of bitstreams: 1 dissertacao IZA NATALIA MORAES FERREIRA.pdf: 986525 bytes, checksum: 25ae0969a8c6f5a0458aadb1c5e26485 (MD5) Previous issue date: 2014-07-15 / Pesticides that are used to combat pests in plantations operate in parallel on other species causing serious problems to be toxic and remain in the environment for a long time. This study aimed to evaluate the photocatalytic degradation of an organophosphorus pesticide by advanced oxidation processes, the insecticide methyl parathion were selected (PM), widely used in Brazilian crops, especially Maranhão. The POA consisti the application of immobilized TiO₂ as photocatalyst and UV radiation to accelerate the degradation of the pesticide. Effects of some parameters such as the illumination time and initial concentration of the compounds during photocatalytic degradation were studied. Was optimized a method for pesticide analysis by liquid chromatography and two advanced reviews (POA) for the destruction of this contaminant oxidation processes. The POA tested were: combination TiO₂/UV and TiO₂/H₂O₂/UV. The analytical method was suitable for evaluation of the POA, with limits of detection and quantification limits of 0,05 mg Lˉ¹ and 0,17 mg Lˉ¹, respectively, this method was then applied to monitoring the concentrations of the pesticide during application of POA procedures. Among the POAs, both cases showed good results in catalytic destruction of pesticide, where 100% of the pesticide was removed immediately first 30 min of exposure to UV radiation. The results showed that the efficiency of photodegradation of PM increases with increasing illumination time and photodegradation efficiency decreases with an increase in the initial concentration of PM. / Os pesticidas que são utilizados no combate às pragas em plantações atuam paralelamente sobre outras espécies causando sérios problemas por serem tóxicos e permanecerem no ambiente por um longo tempo. Este trabalho propôs avaliar a degradação fotocatalítica de um pesticida organofosforado por processos oxidativos avançados, tendo sido selecionado o inseticida paration metilico (PM), amplamente utilizado nas lavouras brasileiras, em especial maranhenses. O POA consisti na aplicação do TiO₂ imobilizado, como fotocatalisador, bem como a radiação UV para acelerar o processo de degradação do pesticida. Foram estudados efeitos de alguns parâmetros, tais como o tempo de iluminação e concentração inicial dos compostos durante a degradação fotocatalítica . Foi otimizado um método para análise do pesticida por cromatografia a líquido bem como avaliados dois processos oxidativos avançados (POA) para a destruição deste contaminante. Os POA testados foram os seguintes: combinação TiO₂/UV e TiO₂/H₂O₂/UV. O método analítico mostrou-se adequado para fins de avaliação do POA, com limites de limites de detecção e quantificação de 0,05 mg Lˉ¹ e 0,17 mg Lˉ¹, respectivamente, este método foi, então, aplicado para o monitoramento das concentrações do pesticida, durante a aplicação dos procedimentos POA. Entre os POAs, os dois casos apresentaram bons resultados na destruição catalítica do pesticida, onde 100% do pesticida foi removido logo nos primeiro 30 min de exposição à radiação UV. Os resultados mostraram que a eficiência de fotodegradação do PM aumenta com o aumento do tempo de iluminação e a eficiência de fotodegradação diminui com o aumento na concentração inicial do PM.

>Magister Scientiae - MSc / The aim of this study was to enrich electrospun fibres with the active mineral phase TiO2 nanoparticles and then to evaluate how well the composite fibres performed in the photocatalytic degradation of methylene blue (MB). Electrospun hydrophobic PAN polymer fibres were used as support structures for the TiO2 nanoparticles. The photocatalytic activity of the TiO2 enriched fibres for dye degradation was evaluated and the effect of external stressors on the fibres was assessed. A comparison was also made to determine whether the TiO2 - photocatalyst catalyst should be coated on top of, or loaded inside the electrospun PAN fibres

Microplastic (MP) pollution has recently been recognized as a threat to the biosphere including humans due to its widespread distribution, persistent nature and infinitesimal size. This study focused on the solid phase degradation of microplastic residues (particularly low density polyethylene, LDPE) in water through heterogeneous photocatalysis process by designed photocatalysts of zinc oxide nanorods (ZnO NRs) and platinum nanoparticles deposited on zincoxide nanorods (Pt NPs-ZnO NRs) under visible light irradiation. These photocatalysts were assessed following standard protocol (ISP 10678: 2010), and characterized using SEM, EDX andoptical spectroscopies (UV-VIS and PL). Deposition of Pt-NPs on ZnO NRs for certain minutes has been found optimum that enhanced the photodegradation process about 38% under UV irradiation and 16.5% under visible light irradiation by improving of both electrons-holes pair separation process and visible light absorption. Photocatalytic degradation of LDPE films was confirmed by FTIR spectroscopy, dynamic mechanical analyzer (DMA), optical and electron microscopes. When LDPE film irradiated in presence of Pt-ZnO, degradation was found quicker than ZnO alone of similar concentration which exhibited formation of a large number of wrinkles, cracks and cavities on the film surface. Dynamic mechanical analyzer (DMA) test indicated stiffness and embrittlement of exposed LDPE films in presence of photocatalysts. Thus, the present work provides a new insight about modified catalysts for the degradation of microplastics in water using visible light.

No description available.