Titanatos nanoestruturados (TNS) obtidos pelo tratamento hidrotérmico de TiO2 são semicondutores muito estudados por suas propriedades de alta área superficial e capacidade de troca iônica. No entanto, sua estrutura cristalina e a influência das condições de síntese e pós-tratamento ainda são motivos de controvérsia. Neste estudo, TNSs foram produzidos em diversas condições e submetidos a diferentes tipos de tratamento ácido e térmico. Os materiais foram caracterizados por difratometria de raios X (DRX), espectroscopias vibracionais (Raman e FTIR), espectroscopia de refletância difusa (DRS), análise térmica (TG, DTG e DSC), análise textural por adsorção de N2 a 77 K, análise química por ICP-OES, e microscopia eletrônica de transmissão. Acompanhando a transformação hidrotérmica de TiO2 (anatase) nanocristalino obtido em laboratório com o tempo, observou-se que os nanocristais de TiO2 se transformam em estruturas lamelares com formato de folhas entre 3h e 12h. As nanofolhas se enrolam parcial ou totalmente formando nanotubos. A transformação da morfologia é acompanhada por uma transformação de fase de anatase para uma fase titanato lamelar, que se completa entre 12h e 24h. Utilizando TiO2 P25 como precursor, observou-se que as amostras obtidas apresentam alto teor de Na+, que é progressivamente eliminado por lavagens do sólido com H2O ou solução ácida. Quanto menor o pH de equilíbrio da suspensão, menor foi o teor de Na+ até o limite de pH 2, em que esse cátion foi praticamente eliminado. A diminuição do teor de sódio foi acompanhada de aumento da área superficial (BET, 155 e 205 m2.g-1 para pH 9 e 2, respectivamente); aumento do espaço interlamelar; diminuição da cristalinidade; e diminuição do bandgap (3,60 e 3,45 para pH 9 e 2, respectivamente). Em pH 1,5, ocorreu ainda maior aumento do espaço interlamelar e da área superficial (368 m2.g-1) indicando que a troca iônica de Na+ por H3O+ não é unicamente responsável pelas transformações estruturais que ocorrem durante a neutralização de TNSs. A desidratação em baixa temperatura (até 150 °C) sofrida por TNSs acidificados é irreversível, levando à diminuição do espaço interlamelar, e formação de vacâncias de oxigênio responsáveis pela absorção de radiação acima de 420 nm (visível). A transformação de fase de titanato para anatase ocorreu à temperatura ambiente quando a neutralização foi feita com HF; entre 300 e 400 °C quando feita com HCl, HNO3, H2SO4 ou ácido acético; e acima de 600 °C quando usado H3PO4. Foi possível inserir diferentes quantidades de prata em TNS através da suspensão dos sólidos em solução de AgNO3. A reação levou à formação de nanopartículas cristalinas de 3 a 5 nm, contendo prata, na superfície das partículas de TNS. Ag+ foi reduzido a Ag0 pelo tratamento térmico das amostras a 250 °C em presença de H2(g). Essas amostras apresentaram absorção de radiação em todo o espectro visível e menor bandgap (3,06 em amostra contendo 3% de Ag, em massa). Em amostras com pouca quantidade de prata (menos de 0,05% em massa), foram observadas bandas largas de absorção (DRS) de ressonância de plasmon de superfície quando calcinadas a 250 °C em H2(g). / Titanate nanostructures (TNS) obtained by the hydrothermal treatment of TiO2 are extensively studied due to their high surface area and ion-exchange ability. However, their crystal structure and influence of synthesis and post-treatment conditions are still under debate. In this study, TNSs were produced under different synthetic conditions and underwent different types of acid and thermal treatments. The materials were characterized by means of X-ray diffractometry (XRD), vibrational spectroscopy (Raman and FTIR), diffuse reflectance spectroscopy (DRS), thermal analysis (TG, DTG and DSC), textural analysis by N2 adsorption at 77 K, chemical analysis by ICP-OES, and transmission electron microscopy (TEM). Following the hydrothermal transformation of homemade crystalline TiO2 (anatase) with time, we observed that TiO2 nanocrystals change into lamellar sheet-like structures between 3h and 12h. The nanosheets roll up partial or totally, thus forming nanotubes. The morphological transformation is accompanied by a phase transformation from anatase to lamellar titanate, which is completed between 12h and 24h. Using TiO2 P25 as precursor, we observed that as-obtained samples have a high Na+ content, which is progressively removed by washing the solids with H2O or acidic solution. The smaller the suspensions equilibrium pH, the smaller the Na+ content to the limit of pH 2, when the removal of this cation was complete. The decrease in sodium content was followed by an increase in the surface area (BET, 155 and 205 m2.g-1 at pH 9 and 2, respectively); an increase in the interlamellar distance; a decrease in crystallinity; and a decrease in bandgap energy (from 3.60 eV at pH 9 to 3.45 eV at pH 7). After treating at pH 1.5, the interlamellar distance and the surface area (368 m2.g-1) increased further, suggesting that the Na+ to H3O+ ion-exchange is not the only factor in the structural transformations that take place during the acid treatment of TNSs. Acidic TNSs undergo an irreversible dehydration process at low temperature (150 °C). It leads to the decrease of the interlamellar distance and to the formation of oxygen vacancies responsible for the absorption of radiation in the visible range (> 420 nm). The phase transformation of the titanate phase to TiO2 anatase took place at room temperature when the TNS was treated with HF; between 300 and 400 °C for samples neutralized with HCl, HNO3, H2SO4 or acetic acid; and over 600 °C when H3PO4 was used. It was possible to insert different amounts of silver by the immersion of the solids in AgNO3 solution, leading to the formation of nanocrystalline-silver-containing nanoparticles (3 to 5 nm) on the surface of the TNS particles. Ag+ was reduced to Ag0 by heat treating the samples at 250 °C in presence of H2(g). These materials showed absorption of radiation in entire visible spectrum and narrowed bandgap energy (3,06 eV for sample with 3wt% of Ag). Samples containing low amounts of Ag (less than 0,05 wt%) showed a wide surface plasmon resonance band (DRS) when calcined at 250 °C under H2(g).

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-10-19T13:45:26Z No. of bitstreams: 1 JACYELLI CARDOSO MARINHO DOS SANTOS - DISSERTAÇÃO (PPGEQ) 2017.pdf: 1181213 bytes, checksum: 831251b803f8b040ed40be41dac19267 (MD5) / Made available in DSpace on 2018-10-19T13:45:26Z (GMT). No. of bitstreams: 1 JACYELLI CARDOSO MARINHO DOS SANTOS - DISSERTAÇÃO (PPGEQ) 2017.pdf: 1181213 bytes, checksum: 831251b803f8b040ed40be41dac19267 (MD5) Previous issue date: 2017-03-17 / Atualmente existem três gerações de células solares, sendo a mais recente a Dye-Sensitized Solar Cells-DSSC, também denominadas como células de Grätzel. Uma das partes essenciais desse tipo de célula solar são os eletrodos transparentes formados a partir de óxido metálicos, sendo o mais comum o de estanho (SnO2). Esse óxido vem sendo largamente utilizado como película condutora em vidro, uma vez que combina características como condutividade elétrica com transparência na região do visível do espectro eletromagnético, podendo assim ser aplicado a- uma grande quantidade de dispositivos eletrônicos. Porém, devido o dióxido de estanho se tratar de um material de alto valor agregado, alternativas para sua obtenção estão sendo estudadas, um desses estudos é a utilização de cloreto de estanho para formação do filme condutor em vidro. Dessa forma, esse trabalho tem como objetivo obtenção de uma solução promotor de estanho a partir de liga de solda comercial. Duas técnicas foram avaliadas, o tratamento ácido e o hidrometalúrgico. Amostras de liga de solda (Sn/Pb) foram submetidas a um tratamento ácido e térmico, com a realização da separação chumbo do estanho e formação da solução de cloreto de estanho. Foram realizados ensaios de dopagem com a utilização da solução de cloreto de estanho juntamente com fluoreto de amônia, utilizadas na formação dos filmes em superfícies de placas de vidro. O parâmetro de verificação da formação do filme condutor foi a resistência elétrica, obtida a partir da condutividade elétrica. A solução de cloreto de estanho gerada pelo processo hidrometalúrgico da liga de solda possibilitou a deposição de uma camada condutora em vidro, sendo resistência obtida com filme condutor com essa metodologia foi de 0,4 a 3 KΩ.Apesar da resistência estar acima da dos valores comerciais, a obtenção da solução de cloreto de estanho da partir da solda comercial, ou de lixo eletrônico, minimiza significativamente o custo de produção dos filmes finos condutores, tornando ainda o processo reciclável, se aproveitada a liga de solda de lixos eletrônicos. / There are currently three generations of solar cells, the most recent being the Dye-Sensitized Solar Cells-DSSC, also referred to as Grätzel cells. One of the essential parts of this type of solar cell is transparent electrodes formed from metal oxide, the most common being tin(SnO2). T-his oxide has been widely used as a conductive glass film, since it combines characteristics such as electrical conductivity with transparency in the visible region of the electromagnetic spectrum, and can be applied to a large number of electronic devices. However, because tin dioxide is a high value-added material, alternatives for its production are being studied, one of these studies is the use of tin chloride to form the conductive glass film. Thus, this work has as objective to obtain a solution promoter of tin from commercial welding alloy. Two techniques were evaluated: acid and hydrometallurgical treatment. Samples of solder alloy (Sn/Pb) were subjected to an acid and thermal treatment, with the lead separation of the tin and formation of the tin chloride solution. Doping tests were carried out using the tin chloride solution together with ammonium fluoride used in the formation of films on glass plate surfaces. The verification parameter of the conductive film formation was the electrical resistance, obtained from the electrical conductivity. The solution of tin chloride generated by the hydrometallurgical process of the weld alloy allowed the deposition of a conductive layer in glass, and resistance obtained with conductive film with this methodology was of 0.4 to 3 KΩ. Although the resistance is above commercial values, obtaining the tin chloride solution from the commercial solder or electronic waste minimizes significantly the cost of production of the conductive thin films, making the process even more recyclable, if the alloy is used Soldering of electronic waste.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / The South African economy relies heavily on mining. The residues of these activities contain harmful metals that are discharged into the environment as industrial wastes, contaminating the air, soil, surface and ground water. A lot of people who live in remote areas in South Africa rely on ground water to drink and cook. They also cultivate their own vegetables increasing the risk of metal toxicity. Some of these metals are very toxic and can cause adverse effects upon being ingested. Toxic metals are well known to be harmful to humans. Some of these metals are carcinogenic or nephrotoxic when a large amount is accumulated in the human body causing cancer and destroying tissues such as the kidneys. The detrimental health effects of these metals may take months to years before manifestation causing people to sideline them as hazards. One of the major toxic elements that are discharged into the environment is lead. A natural zeolite called clinoptilolite has been widely used as an adsorbent for toxic metals from contaminated water and from the human body because of its properties such as ion-exchange capacity and pore size. However, this natural zeolite clinoptilolite is not pure and may contain traces of toxic elements of which the nature and concentration depend on the origin of clinoptilolite. The structural stability of clinoptilolite in acidic or alkaline media is not well documented. The lack of documented information about the leachates of clinoptilolite and their long term effects on the human body may cause harm to people who ingest this zeolite. This has led to investigation of synthetic zeolites such as faujasite which has already been used for decontamination of sludge, industrial effluents and other waste water by removing toxic metals such as Pb, Cd, Cu, Zn and As. This study focuses on comparing the toxic metal removal efficiency of natural zeolite clinoptilolite (C), clinoptilolite-based faujasite (FAU3) and clinoptilolite-based ultrastable Y zeolite (USY3), from contaminated water and simulated gastric juice containing lead and cadmium and to evaluate the extent of leaching of other elements from these zeolites. Clinoptilolite was used as a starting material for the synthesis of faujasite (FAU3) which was further treated with oxalic acid to get an ultrastable Y zeolite (USY3). Various techniques were used to characterise the as-received clinoptilolite, faujasite zeolite and USY, namely XRD, SEMEDS, FTIR, solid state NMR (27Al and 29Si) and BET-N2. These characterisation techniques confirmed that clinoptilolite was successfully transformed into faujasite and that the treatment of faujasite with oxalic acid yielded USY3. A comparative adsorption study was conducted using three zeolite samples: namely Clinoptilolite (C), clinoptilolite-based faujasite (FAU3) and ultrastable Y zeolite (USY3). ICP was used to characterise the liquid samples and it was concluded that zeolites were efficient in removing lead and cadmium from contaminated water samples as well as from simulated gastric juice. Some leachates from these zeolites were also observed. A contaminated water sample containing lead and cadmium was used as a medium where the removal capacity and percentage removal with C, FAU3 and USY3 was investigated. It was observed that the optimum dosage varied from one zeolite to the other and also from one metal to the other. The optimum dosage for C, FAU3 and USY3 for the uptake of lead was found to be 0.2 g, 0.2 g and 0.05 g respectively while for cadmium it was 0.4 g, 005 g and 0.1 g, respectively. It was also shown in this study that the removal capacity for lead and cadmium could be hindered by the Na content in FAU3 and USY3 due to the fact that these metals could be in an uptake competition with Na and other cations that leached out or exchanged from the zeolites. It was observed that the optimum metal concentration for lead uptake as well as for cadmium with few metals being released back into the solution was 0.1 mg/L. The optimum contact time for both lead and cadmium was 15 minutes. The factor that varied depending on the type of metal was pH, which was at its optimum at 3.5 for lead and at 5.5 for cadmium. A simulated gastric juice was contaminated with toxic metals (lead and cadmium) and the zeolites were used to treat the contaminated samples. It was shown that the removal capacity of these zeolites increased with the increase in initial concentration of the metal. Time proved to be one factor that affected the behaviour of zeolites. The modification of the synthesised faujasite into an ultrastable Y zeolite proved to have played a role in increasing the removal of toxic metals and in preventing the high leaching of some elements out of the zeolite. / 2018-12-14

Os objetivos deste trabalho foram: i) estudar a degradação de catalisadores do tipo Pt-M (onde M = Co e Cr) suportados em carbono após tratamento ácido e a atividade catalítica dos mesmos para a reação de redução de oxigênio; ii) avaliar o desempenho e a estabilidade de eletrocatalisadores de platina suportada em monocarbeto e dióxido de tungstênio (WC/C e WO2/C, respectivamente) para a reação de redução de oxigênio em eletrólitos ácidos. O tratamento ácido foi realizado mantendo-se uma certa quantidade do eletrocatisador em uma solução ácida (H2SO4 0,5 mol L-1) a 90ºC por 24 h. Os catalisadores Pt3Co/C e Pt3Cr/C foram caracterizados antes e após o tratamento pelas seguintes técnicas: Espectroscopia por Dispersão de Energia de Raios X (EDX), Difratometria de Raios X (DRX), Microscopia Eletrônica de Transmissão (MET), Espectroscopia de Absorção de Raios X (XAS), como também submetidos a testes eletroquímicos. Os resultados mostraram que os metais menos nobres foram lixiviados devido ao tratamento ácido e que houve variações da região do potencial de redução de óxidos. Em relação aos carbertos de tungstênio, este foram sintetizados pelo método sonoquímico e caracterizados por EDX, DRX e MET. Os resultados eletroquímicos obtidos a partir desses materiais não apresentaram atividade catalítica significante para a RRO, porém, quando se tem Pt ancorada nesse material, a reação de redução de oxigênio é catalisada, similarmente ao desempenho de Pt/C, e segue uma reação via 4 elétrons. Já os materiais formados por dióxido de tungstênio foram sintetizados pelo método de impregnação e também foram caracterizados por EDX, DRX e MET. Os dados obtidos nos testes eletroquímicos destes materiais demonstraram uma certa atividade catalítica para RRO, e que esta reação se ocorre via 2 elétrons. Já para os materiais com Pt suportada em WO2/C, a reação segue a conhecida via 4 elétrons, como no caso de Pt/C. Ao serem submetidos ao tratamento ácido, tanto os catalisadores suportados em WC/C quanto os suportados em WO2/C apresentaram maior estabilidade quando comparados ao Pt/C comercial. / The objectives of this work were: i) to study the degradation of Pt-M catalysts (where M = Co and Cr) supported on carbon after acid treatment and their catalytic activities for the oxygen reduction reaction; ii) to evaluate the performance and stability of platinum electrocatalysts based in tungsten monocarbide (WC/C) and tungsten dioxide (WO2/C) for the oxygen reduction reaction in acidic electrolytes. The acid treatment was carried out by keeping a certain amount of eletrocatalyst in an acidic solution (H2SO4 0.5 mol L-1) at 90°C for 24 h. The Pt3Co/C and Pt3Cr/C catalysts were characterized before and after treatment by the following techniques: Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), X-Ray Absorption Spectroscopy (XAS), followed by electrochemical tests. The results showed that the non-noble metals have been leached due to the acid treatment and that there are variations in the potential region of oxide reduction. Tungsten carbides, were synthesized by a chemistry and characterized by EDS, XRD and TEM. The electrochemical results obtained for the WC/C materials showed no significant catalytic activity for the ORR, but when Pt is anchored, the oxygen reduction reaction is catalyzed, and the performance is similar to that of Pt/C, and with reaction following the 4 electrons pathways. The materials formed by tungsten dioxide were synthesized by an impregnation method, and also characterized by EDS, XRD and TEM. The data obtained in the electrochemical tests of the bare materials showed some catalytic activity for ORR, but the reaction is promoted via the 2 electrons pathways. As for the previous cases the materials formed by Pt supported on WO2/C the reaction follows the 4 electrons steps. When subjected to the acid treatment, as in the case of the catalysts supported on WC/C, the WO2/C-supported materials had higher stability when compared to the commercial Pt/C catalyst.

Submitted by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-01-25T19:15:21Z No. of bitstreams: 1 DissALP.pdf: 1718193 bytes, checksum: 49e0c5e9f494782677bd84e48bbf0257 (MD5) / Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-01-25T19:15:34Z (GMT) No. of bitstreams: 1 DissALP.pdf: 1718193 bytes, checksum: 49e0c5e9f494782677bd84e48bbf0257 (MD5) / Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-01-25T19:15:43Z (GMT) No. of bitstreams: 1 DissALP.pdf: 1718193 bytes, checksum: 49e0c5e9f494782677bd84e48bbf0257 (MD5) / Made available in DSpace on 2018-01-25T19:15:55Z (GMT). No. of bitstreams: 1 DissALP.pdf: 1718193 bytes, checksum: 49e0c5e9f494782677bd84e48bbf0257 (MD5) Previous issue date: 2017-04-11 / Não recebi financiamento / One of the main concerns in the ethanol-producing industries is the growth control of undesirable microorganisms that can cause decrease in the fermentative yield. Among non-Saccharomyces yeasts which can contaminate the fermentation process, the genus Dekkera is the most important because it is able to grow in fermentation conditions and be adapted to the substrates. Regarding the bacteria, Lactobacillus is the most representative genus. In the wine industry, several antimicrobial agents are utilized to control the undesirable yeast and bacteria populations, among them the sulphur dioxide (SO2) which is used in the form of sulphite salts. However, the microbial control by this substance is not known yet in the sugar and alcohol industries, in which the acid treatment of the cells and antibiotics are largely utilized to control the growth of bacteria. In this context, this work aimed to verify the effect of the addition of potassium metabisulphite (PMB) in two steps of the fermentative process for fuel alcohol production: to the raw sugarcane juice and to the acid treatment of the cells. In the first step, PMB concentration and exposure time to the antimicrobial were determined to cause decrease in the number of native yeast and bacteria in the sugarcane juice. Secondly, the minimum inhibitory concentration of PMB was determined to control the growth of Dekkera bruxellensis, an important yeast contaminant of the alcoholic fermentation, when added to the acid treatment of the cells, both in pure culture and in co-culture with Saccharomyces cerevisiae and Lactobacillus fermentum. The effect of this treatment on the fermentative parameters was also analysed. The PMB was effective to control the growth of native yeast and bacteria in the sugarcane juice at the concentration of 800 mg/L with exposure time that varied from 3 to 6 hours, resulting in a maximal reduction of one log cycle for yeasts and from 1.5 to 1.9 log cycles for bacteria. When added to the acid treatment of the cells (pH 2.0), a reduction of approximately one log cycle of D. bruxellensis was verified from the concentration of 225 mg/L of PMB. However, in co-culture with S. cerevisiae and L. fermentum, this concentration also resulted in the decrease of S. cerevisiae cell number, with negative effect on ethanol production. In a cell-recycled batch fermentation, the combination of acid treatment and 150 mg/L of PMB caused a substantial decrease in S. cerevisiae viability as well in the growth of both contaminants, with reduction in the ethanol production and fermentative efficiency. Although the potassium metabisulphite is effective in the context of wine fermentation, it was not appropriate to the fuel ethanol production especially due to the peculiar characteristics of the substrate and the conditions in which the fermentation is carried out. / Uma das principais preocupações das indústrias de produção de etanol combustível é controlar o crescimento de micro-organismos não selecionados para o processo, os quais podem causar prejuízos ao rendimento e a produtividade. Dentre as leveduras não-Saccharomyces contaminantes da fermentação, destaca-se o gênero Dekkera, por apresentar capacidade de crescimento nas condições de fermentação e adaptação aos substratos, e dentre as bactérias, o gênero Lactobacillus. Na indústria do vinho, vários agentes antimicrobianos são utilizados para o controle das populações de leveduras e bactérias indesejáveis, dentre eles o dióxido de enxofre (SO2), utilizado na forma de sais de sulfito. No entanto, o controle de micro-organismos com este agente é pouco conhecido na indústria sucroalcooleira, a qual faz uso principalmente do tratamento ácido entre os ciclos fermentativos e antibióticos para o controle de contaminantes bacterianos. Neste contexto, este trabalho teve por objetivo verificar o efeito da adição de metabissulfito de potássio (MBP) em duas fases do processo fermentativo para produção de etanol combustível: ao caldo de cana bruto e ao tratamento ácido do fermento. Na primeira etapa, verificou-se a concentração e o tempo de contato com o antimicrobiano para causar redução no número de leveduras e bactérias nativas do caldo. Em seguida, determinou-se a concentração mínima inibitória de MBP para o controle do crescimento de Dekkera bruxellensis, uma importante levedura contaminante da fermentação etanólica, quando adicionado ao tratamento ácido do fermento, em cultura pura e em co-cultura com Saccharomyces cerevisiae e Lactobacillus fermentum e o efeito dessa adição sobre os parâmetros fermentativos. O MBP foi eficaz no controle de bactérias e leveduras nativas do caldo na concentração de 800 mg/L com tempo de contato que variou de 3 a 6 horas, proporcionando uma redução máxima de cerca de 1 ciclo log para leveduras e de 1,5 a 1,9 ciclos log para bactérias. Quando adicionado ao tratamento ácido (pH 2,0), ocorreu uma redução de aproximadamente 1 ciclo log de D. bruxellensis a partir de 225 mg/L de MBP. Porém em co-cultura com S. cerevisiae e L. fermentum, essa concentração ocasionou também redução do número de células de S. cerevisiae, com efeito sobre a produção de etanol. Em sistema de fermentação em batelada com reciclo celular, a combinação do tratamento ácido e 150 mg/L de MBP ocasionou queda substancial na viabilidade da levedura do processo e dos contaminantes D. bruxellensis e L. fermentum, com consequente decréscimo na produção de etanol e eficiência fermentativa. Embora seja eficiente no contexto da fermentação para produção de vinhos, o metabissulfito de potássio não se mostrou adequado para a fermentação alcoólica para produção de etanol combustível, devido às características peculiares do substrato utilizado e das condições em que é realizada a fermentação.

Made available in DSpace on 2014-12-17T14:07:03Z (GMT). No. of bitstreams: 1 LidianeB_DISSERT.pdf: 4154722 bytes, checksum: 488f09116e9123d31a90be2e32d3f613 (MD5) Previous issue date: 2012-07-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Structural changes in waste for zeolites synthesis are subject of many studies carried out in the synthesis of molecular sieves. These materials are named molecular sieves because they have well defined pore sizes and they have the capacity of select molecules by its size. In this work, it was studied the synthesis processes of two types of molecular sieves: pillared acid clays using as starting material one natural montmorillonite clay and the synthesis of zeolites from a silico-aluminous residue. This residue is a byproduct of the extraction of lithium -spodumene. The preparation of pillared acid clays was performed in two steps: 1? acid treatment of clay samples (time and temperature studies) and 2?pilarization of them with Al13 (Keggin ion). The temperature and acid concentration affect the removal of cations in the structure and porosity of the material obtained. The analysis of X-ray diffraction (XRD) and infrared spectroscopy (IR), showed that increasing the severity of the acid treatment compromises the structural material. Also the pore size distribution is approximately uniform. Despite presenting a structural disorganization, the samples were pillared. As evidenced by XRD increasing the basal spacing, specific area and uniform porosity by adsorption of N2. Regarding the microporous molecular sieves were synthesized zeolites A and NaP1 from a silico-aluminous residue, a byproduct of extracting lithium. The temperature and time of agitation during the synthesis were the most important factors for obtaining zeolite A. The aging of the gel and the highest crystallization time promoted the formation of zeolite NaP1 using a Si / Al ratio = 3.2 / Modifica??es estruturais de res?duos para s?ntese de ze?litas ? tema de muitos estudos desenvolvidos na ?rea de s?ntese de peneiras moleculares. Estes materiais s?o chamados de peneiras moleculares por possu?rem tamanho de poros bem definido e por terem a capacidade de selecionar as mol?culas pelo tamanho. Neste trabalho foram estudados os processos de s?ntese de dois tipos de peneiras moleculares: argilas ?cidas pilarizadas, utilizando como mat?ria prima natural uma argila montmorilonita, e tamb?m a s?ntese de ze?litas a partir de um res?duo s?lico-aluminoso subproduto da extra??o de L?tio do -espodum?nio. A prepara??o de argilas ?cidas pilarizadas foi realizada em duas etapas: 1? tratamento ?cido das amostras de argila (estudos de tempo e temperatura) e 2? pilariza??o das mesmas com Al13 (?on de keggin). As vari?veis temperatura e concentra??o do ?cido influenciaram na retirada de c?tions estruturais e na porosidade do material obtido. A partir das an?lises de difra??o de raios-X (DRX) e espectroscopia de infravermelho (IV), observou-se que o aumento da severidade do tratamento ?cido compromete a organiza??o estrutural do material. Tamb?m a distribui??o no tamanho de poros fica menos uniforme. Mesmo apresentando menor organiza??o estrutural, as amostras foram pilarizadas. Foi comprovado por DRX o aumento do espa?amento basal e por adsor??o de N2 o aumento da ?rea espec?fica e uniformiza??o dos poros. Com rela??o ?s peneiras moleculares microporosas, foram sintetizadas ze?litas A e NaP1 a partir de um res?duo s?lico-aluminoso, subproduto da extra??o de L?tio. A temperatura e o tempo de agita??o durante o processo de s?ntese s?o par?metros importantes para a obten??o da ze?lita A. O envelhecimento do gel e o maior tempo de cristaliza??o promoveram a forma??o da ze?lita NaP1, utilizando uma rela??o Si/Al = 3,2

Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2015 / The study has focused on the effects of different acids treatments on the nanostructure of MWCNTs; doping metal oxides (copper oxide (CuO), Iron (III) oxide (Fe2O3), nickel oxide (NiO) and cobalt oxide (Co3O4)) on MWCNTs and investigates their electrochemical hydrogen and energy storage capabilities. Fourier transform infrared (FTIR) confirmed the formation of functional groups on the surface of the acid treated MWCNTs. X-ray diffraction (XRD) showed that the graphitic structure of the MWCNTs was retained after treatment with mild acids (nitric acid (HNO3), hydrogen peroxide (H2O2), a mixture of the acids, hydrogen peroxide: nitric acid (H2O2:HNO3) and hydrogen peroxide: sulfuric acid (H2O2:H2SO4)). Transmission electron microscopy (TEM) confirms the removal of bamboo carbon structures inside the inner tubes of the MWCNTs after treatment with mild acids. Brunauer-Emmet- Teller (BET) showed an increase in the surface area of mild acids treated MWCNTs. Thermogravimetric analysis (TGA) results demonstrated that the thermal stability of MWCNTs increases after treatment with mixtures of the acids. Different metal oxides treated at different temperatures were incorporated into MWCNTs (treated by a mixture of H2O2:HNO3). X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) confirmed the presence of different metal oxides inside/on the surface of the acid treated MWCNTs. The MWCNTs treated by H2O2:HNO3 gave both the highest discharge capacity (72.63 mAh/g) and capacitance (8.61 F/g), as compared to the other electrode materials. The improved hydrogen storage capacity and specific capacitance can be attributed to high surface area, wider pore size distribution and the amount of functional groups on the surface of H2O2:HNO3-treated MWCNTs; with the functional groups acting as electron transmitters. The 5wt.% CuO@300oC-MWCNTs composite showed the highest hydrogen storage capacity of 159 mAh/g. This capacity was further improved by addition of manganese oxide resulting in the highest discharge capacity of 172 mAh/g (which is equivalent to 0.64 wt.% of hydrogen stored). The highest specific capacitance of 9.70 F/g was obtained on 5wt% Fe2O3@400oCMWCNTs composite.

Beton wird global als Werkstoff eingesetzt, weist als Natur-verwendendetes Material allerdings unterschiedliche regionale Spezifikationen auf. Hier entsteht ein Spannungsfeld zwischen Universalismus und Partikularismus. Die beim Absäuern offengelegten Sandkörner werden zum ortsbezogenen Naturpigment, die diese Ambivalenz sinnlich erfahrbar machen. Die Werkgruppe präsentiert in ihrer Uniformität ein Bild der Gemeinsam- und Verbundenheit. Gleichzeitig erheben die einzelnen Platten Anspruch auf spezifische, in ihrer Körnung auf partikularer Ebene abgebildete Eigenschaften der Diversität und Einzigartigkeit.

Trä är den bästa förnyelsebara källan för att producera många produkter på grund av dess biokompatibla och biologiskt nedbrytbara natur. Träets biomassa har en motstridig natur mot enzymatisk uppgradering. Det beror på olika orsaker som ligninhalt, acetylhalt i hemicellulosa och cellulosakristallinitet som blockerar enzymets bindningsställe. Denna studie kommer under BioUPGRADE, som är en samarbetsplattform för att skapa högvärdiga och mångsidiga material på ett hållbart sätt med hjälp av biokatalys. Det allmänna syftet med denna studie är att producera holocellulosa och hemicellulosasubstrat från olika träslag och producera, rena och validera galaktosoxidas som en potentiell biokatalysator för träfibermodifiering. Studien undersöker effekten av kemisk perättiksyradelignifiering på två träslag, lövträ av eukalyptus (HW), och barrträ av gran (SW), undersökta vid olika tidsintervall, där PAA framställdes exsitu med ett volymetriskt förhållande på 1:3. Med resultaten från PAA-behandlingen avlägsnades 38,53 % lignin i eukalyptus och 31,80 % i barrved. Hemicellulosautbytet ökade med 47,40 % för eukalyptus och 19,05 % för gran med en ökning av tiden för PAA-behandling. Acetylhalten i hemicellulosan minskade från 2 % till 0,6 % i lövträ och 1,96 % till 0,6 % i barrträ. Cellulosautvinningen efter delignifieringen var nästan 100 %. Galaktosoxidaset producerades i en skakkolv med användning av Pichia pastoris KM71H-stammen. Pichia pastoris KM71H-celler odlades med användning av det buffrade komplexa glycerolmediet (BMGY) och galaktosoxidas uttrycktes med användning av Pichia pastoris KM71H-stammen i buffrat komplex metanolmedium (BMMY). Det uttryckta GaOx-proteinet renades därefter med användning av AKTA-kromatografi med användning av en 5 ml Histrap FF-kolonn. För att bestämma proteinkoncentrationen utfördes bicinchoninsyra (BCA) analys och GaOx som producerades i skakkolvsodling var 286,25 mg/L. Den specifika aktiviteten hos skakkolven som produceras GaOx är 164,24 U/mg. Det kan observeras att PAA-behandling visar sig vara en effektiv metod för delignifiering eftersom cellulosautvinningen är nära 100 % och förlusten av hemicellulosa är relativt låg med det använda volymetriska förhållandet. GaOx som produceras i skakkolvsproduktion visar ett lovande utbyte med en betydande specifik aktivitet mot galaktosen som substrat och kan användas i framtiden för enzymatisk uppgradering av träets biomassa. / Wood is the best renewable source for producing many products due to its biocompatible and biodegradable nature. The wood biomass has a recalcitrance nature towards enzymatic upgrading. It is due to various reasons such as lignin content, acetyl content in hemicellulose, and cellulose crystallinity which blocks the enzyme binding site. This study comes under BioUPGRADE, which is a collaborative platform to create high-value and multipurpose materials sustainably using biocatalysis. The general aim of this study is to produce holocellulose and hemicellulose substrates from different wood species and produce, purify, and validate galactose oxidase as a potential biocatalyst for wood fiber modification. The study investigates the effect of chemical peracetic acid delignification on two wood species, eucalyptus hardwood (HW), and spruce softwood (SW) investigated at different time intervals, where the PAA was prepared ex-situ with a volumetric ratio of 1:3. With the results from the PAA treatment, 38.53% of lignin was removed in eucalyptus and 31.80% in softwood. The hemicellulose yield increased by 47.40% for eucalyptus and 19.05% for spruce with an increase in the time of PAA treatment. The acetyl content of the hemicellulose was reduced from 2% to 0.6% in hardwood and 1.96% to 0.6% in softwood. The cellulose recovery after the delignification was nearly 100%. The galactose oxidase was produced in a shake flask using the Pichia pastoris KM71H strain. Pichia pastoris KM71H cells were cultivated using the buffered complex glycerol media (BMGY) and galactose oxidase was expressed using the Pichia pastoris KM71H strain in Buffered complex methanol media (BMMY). The expressed GaOx protein was subsequently purified using AKTA chromatography using a 5ml Histrap FF column. To determine the protein concentration Bicinchoninic acid (BCA) analysis was performed and the GaOx produced in shake flask cultivation was 286.25 mg/L. The specific activity of the shake flask produced GaOx is 164.24 U/mg. It can be observed that PAA treatment proves to be an efficient method for delignification as the cellulose recovery is near 100% and the loss of hemicellulose is relatively low with the volumetric ratio used. The GaOx produced in shake flask production shows a promising yield with a significant specific activity towards the galactose as substrate and could be used in the future for the enzymatic upgrading of the wood biomass.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / For centuries the contamination of surface water has been problematic, especially in third world countries whereby socio-economic issues are prevalent. With the development of various technologies for surface water rehabilitation, adsorption has been found to be the most viable due to its lower cost implications. As such the development of innovative adsorbents which are synergistic to the low cost method have been sought. Herein, the use of fossil coral limestone from Mauritius as adsorbents for the removal of Pb(II), Cr(VI) and methylene blue is presented. The pristine material (PCLS) was thermally treated by calcination to temperatures 800°C (CLS-800) and 900°C (CLS-900) and chemically treated by using an acid HCl (ACL) and base NaOH (BCL). The optimum conditions found for chemical and thermal treatment of the pristine material were used for the one pot synthesis of magnetite and maghemite calcium carbonate based nanocomposites. The pristine fossil coral limestones were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray fluorescence XRF), X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET) and Fourier transformed infrared (FTIR) spectroscopy, UV visible spectrophotometer (UV/vis) and Photolumiscent spectroscopy (PL). Surface morphology of the material was found to contain an interconnected framework of pores, with a surface area of 20.45 m2/g and pore with of 4.04 nm. Thermal treatment of the material was found to increase the surface area of the materials to 64.10 and 63.28 m2/g for CLS-800 and CLS-900. The surface morphology of the calcined materials compared to the pristine were fibrous like and irregularly shaped for CLS-800 and CLS-900 respectively. The FTIR revealed the dominant surface groups to be (-C-O) and (-C=O) asymmetric stretch of the in and out of plane bend of carbonate (-CO32-), with the composition of the material being 91.76 % (-CaO) and 3.32% SrO. The thermally treated materials also exhibited vibrations of asymmetric stretch, which are characteristics of the carbonates as with the pristine material. However, EDS of the pristine compared to that of the calcined materials show a decline in the carbon and oxygen content, due to calcination. The XRD analysis confirmed the orthorhombic structure of aragonite, while CLS-800 was rhombohedral calcite with newly developed (-CaO) peaks. CLS-900 showed complete removal of CaCO3 polymorphs with more (-CaO) peaks. The surface morphology of the chemically modified samples show irregularly shaped surface. The XRD analysis confirmed that chemical treatment did convert the materials to a different polymorph. The FTIR of the chemically modified materials compared to the pristine, were found to reveal a removal of the vibrations of the asymmetric stretch associated with carbonates. However, vibrations associated with (-CaO) were observed. The SEM of the nanocomposites was observed to deviate from sphericity with variable size distribution. The materials were both red and blue shifted due to their variable sizes. Their UV/vis revealed absorption bands in the visible region. The adsorption analysis was done by varying parameters such as time, pH, concentration and temperature. The data was such that the highest capacity for the pristine material was found to be 37.24, 39.26 and 69.42 mg/g for MB, Pb(II) and Cr(VI) respectively. The removal of MB and Pb(II) pollutants were due to physical adsorption, as observed from the good fitting to pseudo first order model (PFOM). The removal of Cr(VI) was due chemisorption and the good fit on pseudo second order model (PSOM). The adsorption process was supported on a heterogeneous surface whereby multilayer adsorption could occur. Adsorption was spontaneous and feasible, exothermic for MB and Pb(II) and endothermic for Cr(VI) at all the studied temperatures as observed from thermodynamics. The adsorption of methylene blue was found to be more favourable on adsorption compared to photo-degradation Chemical modification was observed to increase adsorption and the maximum removal capacities for PCLS, ACL and BCL for Cr(VI) ions were 69.42, 65.04, 64.88 mg/g, Pb(II) ions 39.36, 74.11, 78.34 mg/g and methylene blue 37.24, 46.28, 46.39 mg/g, respectively. Uptake of Cr(VI) and methylene blue on ACL and BCL was feasible on a heterogeneous surface whereby multilayer adsorption took place. Monolayer adsorption on a homogenous surface of ACL and BCL was observed for Pb(II) uptake. The uptake of Pb(II) was exothermic on PCLS and ACL while methylene blue only on PCLS. The adsorption of Cr(VI) ions onto PCLS, ACL and BCL and methylene blue dye onto ACL and BCL were endothermic in nature. The adsorption process was spontaneous and feasible at all the studied temperatures. Thermal modification further increased the adsorption uptake of the pollutants. The recorded uptake for Cr(VI) and Pb(II) were 99.12 and 98.42 mg/g onto CLS-800 and CLS-900, respectively. The adsorption process was found to be physisorption, due to the good fit on PFOM. In addition, the adsorption occurred on a heterogeneous surface whereby multilayer adsorption was possible. The removal of Cr(VI) was found to be exothermic for both the materials and Pb(II) was found to be endothermic. The materials were tested for their reusability to up to four cycles, whereby the removal on the fourth cycle were 16.87, 63.60, 73.13 mg/g for Cr(VI), 9.87, 64.19 and 70.95 mg/g for Pb(II) on PCLS, CLS-800 and CLS-900. While the leaching test for PCLS, CLS-800 and CLS-900 for the release of Ca2+ into solution was found to be within the permissible limits of world health organisation (WHO). The as synthesized nanocomposites increase adsorption of the pollutants. Maximum capacities were found to be 345.34, 388.31, 377.92 and 375.35 mg/g for Pb(II) onto magnetite-PCLS, magnetite-CLS, maghemite-PCLS and maghemite-CLS, respectively and 308.01, 335.3, 335.29 and 335.27 mg/g for Cr(VI) onto magnetite-PCLS, magnetite-CLS, maghemite-PCLS and maghemite-CLS, respectively. From the data it was observed that the maghemite samples were much more favourable for the removal of the pollutants. The removal was due to chemical adsorption, as observed from the good fit onto PSOM and intraparticle diffusion (IPD), whereby surface adsorption was the rate limiting step. The adsorption process was heterogeneous and multilayer, while thermodynamic data reveal that adsorption was spontaneous and favourable at the studied temperature.