Dissertations / Theses on the topic 'Metals'
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Silva, Marcio Wagner da. "Efeitos da adição de metais básicos aos catalisadores à base de Pd e Ru para a hidrodescloração do pentaclorofenol." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266936.
Full textTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Alguns compostos organoclorados são motivo de grande preocupação, em razão da elevada toxicidade e persistência, tanto no meio ambiente quanto em organismos vivos. Dentre tais compostos, encontra-se o pentaclorofenol, utilizado para a conservação de madeira e na proteção de lavouras. Uma das tecnologias mais promissoras para o tratamento dessa classe de compostos tóxicos é a hidrodescloração catalítica, através da qual é possível recuperar a matéria-prima utilizada na síntese do contaminante. Embora diferentes catalisadores possam ser utilizados nesta reação, destacam-se os sólidos à base de Pd e Ru, notadamente devido à maior atividade catalítica. No entanto, os elevados preços destes metais nobres podem aumentar significativamente os custos do processo. Nesse contexto, o objetivo do presente trabalho é estudar os efeitos da presença dos metais básicos Fe e Ni em catalisadores à base de Pd e Ru, destinados à hidrodescloração do pentaclorofenol em fase líquida. Para tanto, catalisadores monometálicos e bimetálicos, suportados em alumina (Al2O3) ou titânia (TiO2), foram preparados a partir dos precursores clorados, através do método de co-impregnação a seco. Os sólidos obtidos foram caracterizados por meio das técnicas de adsorção de N2 (método BET), microscopia eletrônica de varredura com espectrometria de energia dispersiva de raios-X (MEV-EDX), espectroscopia fotoeletrônica de raios-X (XPS), redução à temperatura programada (TPR) e microscopia eletrônica de transmissão (MET). A hidrodescloração do pentaclorofenol foi conduzida num reator Parr® do tipo "slurry", à temperatura de 383 K e sob pressão de H2 de 0,5 MPa. Na reação de interesse, a adição de Ni ao catalisador de Ru/TiO2 diminui a atividade catalítica, porém mantém a elevada seletividade de cicloexanol, possibilitando, portanto, uma diminuição do custo do catalisador, sem perda de seletividade. Já para o catalisador de Pd/TiO2, a presença de Ni também diminui a atividade catalítica, assim como observado no caso do catalisador de Ru/TiO2, mas verifica-se uma diminuição da seletividade de fenol. Por sua vez, a adição de Fe ao catalisador de Pd/TiO2 tem pouca influência sobre a atividade e a seletividade, possibilitando, assim, uma significativa diminuição do custo do catalisador, sem prejuízo do desempenho catalítico. Os comportamentos catalíticos observados são analisados e interpretados à luz dos resultados obtidos através das caracterizações dos sólidos, assim como das informações disponíveis na literatura
Abstract: Some organic chlorine compounds are of great concern, because of high toxicity and persistence, both the environment and in living organisms. Among these compounds, is the pentachlorophenol, which is used to Wood conservation and for the protection of crops. A very promising technology to treating this class of toxic compounds is the catalytic hydrodechlorination, through which it is possible the recovery of raw material used in the synthesis of the contaminant. Although various catalysts may be used in this reaction, we highlight the solids Pd and Ru, mainly due to higher catalytic activity. However, the high prices of these noble etals can increase significantly the process costs. In this context, the objective of this work is to study the effects of base metals addition, Fe and Ni, in the catalysts based on Pd and Ru, for the pentachlorophenol hydrodechlorination in liquid phase. For this, monometallic and bimetallic catalysts, supported in alumina (Al2O3) or titanium oxide (TiO2), were prepared from chlorinated precursors by the incipient impregnation method. The obtained solids were characterized by techniques of N2 adsorption (BET method), scanning electronic microscopy with X-ray spectrometry analysis (EDX), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and transmission electronic microscopy. The pentachlorophenol hydrodechlorination was carried out in a "slurry" Parr® reactor, at the temperature of 373 K under the hydrogen pressure of 0,5 MPa. In the interest reaction, the addition of Ni to the Ru/TiO2 catalysts reduces the catalytic activity, but the high cyclohexanol selectivity is maintained, enabling thus, decrease the catalyst cost, without loss of selectivity. To the Pd/TiO2 catalyst, the i presence reduce the catalytic activity, like to the observed to the Ru/TiO2 case, but is verified the decreasing of phenol selectivity. In turn, the Fe addition to the Pd/TiO2 catalyst has little influence on the activity and selectivity, leading thus to a significant decrease in the catalyst cost, without prejudice to the catalytic performance. The observed catalytic behaviors are analyzed and interpreted based in the results obtained through the characterization of solids, as well as information available in the literature
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutor em Engenharia Química
Nowicki, Timothy. "Statistical model prediction of fatigue life for diffusion bonded Inconel 600 /." Online version of thesis, 2008. http://hdl.handle.net/1850/7984.
Full textClegg, Richard Edward. "Liquid-metal embrittlement of metals and alloys." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260608.
Full textBernard, William J. "The continuous rheoconversion process Scale-up and optimization." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-082305-102150/.
Full textZwigl, Peter 1963. "Transformation-superplasticity of metals and metal matrix composites." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/49665.
Full textIncludes bibliographical references (p. 156-162).
The work covers transformation superplasticity of metals, alloys and metal matrix composites. Fundamental studies of transformation superplasticity in unreinforced metals, which either deform plastically or by creep, form the basis of further investigations in metal matrix composites. Experiments and analytical modeling are complemented by numerical analysis. The transformation superplastic behavior is related to microstructure and chemical composition. Based on an existing linear theory, a non-linear model is developed and applied to the experimental data. Numerical methods are used to model the stress-, strain and temperature evolution during the phase transformation. The results are in good agreement with the experiment and analytical predictions. First, transformation superplasticity of iron and iron-TiC composites is demonstrated with strains of 450% and 230% respectively. The reduction of the transformation superplasticity in the composites is attributed to the dissolution of TiC in iron and effect which is shown for iron-carbon alloys. Effects of transient primary creep, ratchetting and partial transformation through the ferrite-austenite phase field are examined. Second, transformation superplasticity of zirconium is demonstrated for the first time with a strain of 270% without fracture. Partial transformation resulting from high cycle frequencies is analyzed and related to material properties and cycle characteristics. Finally, nickel aluminide with unstabilized zirconia particulates shows significant higher strain rates upon thermal cycling as compared to the unreinforced matrix. Although, the fracture strain of 23% is below the superplastic limit, the composite shows a high strain rate sensitivity of m = 0.71, which is a necessary characteristic of transformation superplasticity.
by Peter Zwigl.
Ph.D.
Mendonça, Marília Assunção. "Reator contínuo com leito de lodo biológico anaeróbio para a remoção de íons metálicos em solução aquosa /." Jaboticabal, 2016. http://hdl.handle.net/11449/142849.
Full textCoorientador: Allynson Takehiro Fujita
Banca: Mariana Carina Frigieri
Banca: Luciano dos Santos Rodrigues
Resumo: Reatores contínuos com leito de lodo biológico anaeróbio, in natura e seco em estufa, foram utilizados para a remoção de metais (Cu+2, Mn+2 e Zn+2) em solução aquosa. Com o lodo in natura avaliou-se o efeito conjunto da bioacumulação e biossorção; e com o lodo seco em estufa o efeito exclusivo da biossorção. Foram utilizadas baixas concentrações de Cu+2, Mn+2 e Zn+2 (0,01 a 5,00 mg L-1), tendo em vista que para a ocorrência de bioacumulação devem ser mantidas condições não tóxicas para os micro-organismos. Portanto, os resultados poderão ser aplicados para o pós-tratamento de efluentes com concentrações remanescentes desses metais, que necessitem de polimento para a disposição final, atendendo aos limites legais de qualidade de água do corpo receptor. Os lodos utilizados foram coletados de reatores anaeróbios horizontal (RAH) e de fluxo ascendente com manta de lodo (UASB) utilizados no tratamento de águas residuárias de suinocultura. A temperatura foi controlada a 20°C em todos os ensaios. Foram avaliadas vazões de 5, 10 e 15 mL min-1, valores de pH 4,0 e 6,0 e concentrações de 0,01, 0,5 e 1,0 mg L-1 de Cu2+ e Mn2+, e de 0,05; 2,5 e 5,0 mg L-1 de Zn2+. O pH ótimo para a remoção de Mn2+ e Zn2+ foi 4,0 e para o Cu2+ não foi verificada diferença. A maior eficiência foi encontrada quando utilizou-se os menores valores de concentração e fluxo para os três biossorventes avaliados. Foi verificado que os valores de concentração de metais utilizados demonstraram não serem tóxicos para... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Continuous reactors with anaerobic biological sludge bed, in nature and dry in an oven, were used for removal of metals (Cu+2, Mn+2 and Zn+2 ) in aqueous solution. With the sludge in natura it was evaluated the combined effect of bioaccumulation and biosorption; and the dry sludge in greenhouse sole effect of biosorption. It was used lower concentrations of Cu+2, Mn+2 and Zn+2 (0.01 to 5.00 mg L -1 ), considering that for bioaccumulation occurring should be kept non-toxic conditions for the micro-organisms. Therefore, the results can be applied to the posttreatment of effluents with remaining concentrations of these metals, which require polishing to final disposal, meeting the legal limits of quality of the receiving water body. The used sludges were collected from horizontal anaerobic reactors (RAH) and ascendant upflow sludge blanket (UASB) used in the treatment of swine wastewater. The temperature was controlled at 20°C in all tests. It was analyzed outputs of 5, 10 and 15 ml min-1, pH values 4.0 and 6.0 and concentrations of 0.01, 0.5 and 1.0 mg L- 1 Cu+2 and Mn+2, and 0.05; 2.5 and 5.0 mg L -1 Zn+2 . The optimum pH for the removal of Mn+2 and Zn+2 was 4.0 and the Cu+2 it was not verified difference. The highest efficiency was found when it was used the lowest values of concentration and flux for all three reviews biosorbents. It has been found that the metals concentration values used proved not to be toxic to cells of microorganisms present in the sludge in nature,... (Complete abstract click electronic access below)
Mestre
Malas, James C. "Methodology for design and control of thermomechanical processes." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1173324636.
Full textMiljana, Prica. "Efekti primene različitih postupaka remedijacije na imobilizaciju teških metala u sedimentu." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2009. https://www.cris.uns.ac.rs/record.jsf?recordId=73282&source=NDLTD&language=en.
Full textThis work is concerned with the comparison of the different methods of metal risk assessment in sediments based on examination of the qualityof water courses in Vojvodina. Besides, it deals with the possibility of applying remediation treatments of contaminated sediment and with the efficiency of the different methods, that is the techniques, for immobilization of sediment heavy metals by applying S/S and thermal treatments. A dominant mechanism is proposed for the process of leaching ofthe metals from treated mixtures.Comparison of the results obtained by the different methods of sediment quality assessment showed that in some cases one approach to solving this problem is not sufficient. Metal concentrations in particular sediment samples (the Begej, the DTD Canal, the Nadela, the Sava at Šabac) indicate the presence of contamination, the analyzed samples being of Class 4. According to the Dutch regulations, a sedimentof Class 4 is of unacceptable quality and requires urgent intervention in the sense of sediment dredging, disposal into special depots, and, if possible, remediation. For some samples, despite a high pseudo-total concentration (Class 4), no potential toxicity was confirmed onthe basis of the ratioof the acidic volatile sulfide and simultaneously extracted metals. The results showed that, apart from chemical analyses, biological tests are also necessary, but also sequential extraction analysis, which can more clearly define the way of metal binding to the particular sediment fractions, to allow a more reliable prediction of metal mobility, potential toxicity and bioavailability. In the analysis of sediment quality it is also necessary toinclude the aspect of radioactivity, as it has been shown that the results of this analysis can, not only confirm some of the results of the other analyses, but also indicate the sediment age, origin of contamination and potential toxicity.The subsequent steps should be directed to the control and prevention of contamination, in order to ensure that the water course reviatalization has a lasting positive effect on the environment, an unimpared and safe navigation and application of remediation methods.In the sediment sample (Class 4) that was usedfor the examination of the efficiency of it appeared that zinc, nickel and lead exhibit a high risk, as the percentages of these metals in the exchangeable and carbonate phases were in the range from 40.1 to 45.2%. On the other hand, chromium and cadmium exhibited a moderaterisk, whereas copperin these fractions was present at the levels corresponding to a low risk (5.3%). This is alsoin agreement with the results of pore water analysis and simultaneously extracted metals and acid volatile sulphide examinations.The investigations presented in this work provided an answer to the question whetehr the remediation can successfully remove the contamination in the sense of the immobilization of metals in a state that will not be harmful tothe environment. All the treatments applied yielded a decrease of the percentage of cumulatively leached metals from the S/S mixtures, but none of the mixtures of treated sediments with the tested immobilization agents belongs to the group of inert materials if the cumulative leached concentrations are compared with the concntrations for the wastes given by the EU legislation (2003/33/EC). Ifthe goal is to obtain a non-hazardous material it is necessary to treat the contaminatedsediment with at least 30% of the immobilizing agent (cement or calcium oxide). Based on the diffusion coefficients and leachability index, the highest immobilization efficiency was achieved using a mixture of cement and calcium oxide (30% of cement and 10% of CaO) and by applying thermal treatment at a higher temperature (11000C) with clay (20%). A dominant mechanism of leaching metals from these mixtures is diffusion.
Clark, Amy Louise. "Mechanisms of metal binding and resistance to toxic metals in bacteria from soils polluted with toxic metals." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341456.
Full textSekhula, Koena Sinah. "Heavy metal ion resistance and bioremediation capacities of bacterial strains isolated from an Antimony Mine." Thesis, University of Limpopo, 2005. http://hdl.handle.net/10386/139.
Full textSix aerobic bacterial strains [GM 10(1), GM 10 (2), GM 14, GM 15, GM 16 and GM 17] were isolated from an antimony mine in South Africa. Heavy-metal resistance and biosorptive capacities of the isolates were studied. Three of the isolates (GM 15, GM 16 and GM 17) showed different degrees of resistance to antimony and arsenic oxyanions in TYG media. The most resistant isolate GM 16 showed 90 % resistance, followed by GM 17 showing 60 % resistance and GM 15 was least resistant showing 58 % resistance to 80 mM arsenate (AsO4 3-). GM 15 also showed 90 % resistance whereas isolates GM 16 and GM 17 showed 80 % and 45 % resistance respectively to 20 mM antimonate (SbO4 3-). Arsenite (AsO2 -) was the most toxic oxyanion to all the isolates. Media composition influenced the degrees of resistance of the isolates to some divalent metal ions (Zn2+, Ni2+, Co2+, Cu2+ and Cd2+). Higher resistances were found in MH than in TYG media. All the isolates could tolerate up to 5 mM of the divalent metal ions in MH media, but in TYG media, they could only survive at concentrations below 1 mM. Also, from the toxicity studies, high MICs were observed in MH media than TRIS-buffered mineral salt media. Zn2+ was the most tolerated metal by all the isolates while Co2+ was toxic to the isolates. The biosorptive capacities of the isolates were studied in MH medium containing different concentrations of the metal ions, and the residual metal ions were determined using atomic absorption spectroscopy. GM 16 was effective in the removal of Cu2+ and Cd2+ from the contaminated medium. It was capable of removing 65 % of Cu2+ and 48 % of Cd2+ when the initial concentrations were 100 mg/l, whereas GM 15 was found to be effective in the biosorption of Ni2+ from the aqueous solutions. It was capable of removing 44 % of Ni2+ when the initial concentration was 50 mg/l. GM 17 could only remove 20 % of Cu2+ or Cd2+. These observations indicated that GM 16 could be used for bioremediation of xvi Cu2+ and Cd2+ ions from Cu2+ and Cd2+-contaminated aqueous environment, whereas GM 15 could be used for bioremediation of Ni2+.
National Research Foundation and the University of the North Research Unit
Fernandes, Paulo Jorge Luso. "Fatigue and fracture of metals in liquid-metal environments." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337963.
Full textMullins, M. "Subcellular localization of metals in metal tolerant higher plants." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384378.
Full textYoung, Kirsty. "Epitaxy on quasicrystals : metals, semi-metals and molecules." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8113/.
Full textNguyen, Bao Anh. "Economics of Base Metals." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35007.
Full textDinescu, Adriana Cundari Thomas R. "Metals in chemistry and biology computational chemistry studies /." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3678.
Full textMorgan, Mark Williams. "The art of rokusho /." Online version of thesis, 1990. http://hdl.handle.net/1850/11513.
Full textDey, Gopal Ch. "Application of functionalised chelating resins for selective sorption of metal ions with special reference to heavy metals." Thesis, University of North Bengal, 2011. http://hdl.handle.net/123456789/1391.
Full textFindon, Matthew M. "Semi-solid slurry formation via liquid metal mixing." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0721103-161140/.
Full textSadjadi, Seyedabdolreza. "Ab initio relativistic-consistent calculations and charge density and experimental mass-spectroscopic analysis of mono and poly-nuclearclusters of group 11 and 12 transition metals and metal chlorides: ySeyedabdolreza Sadjadi." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B5060577X.
Full textpublished_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
Ngule, Chrispus M. Jr. "In Vitro Adsorption of Heavy Metals Using Metal-Organic Frameworks." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1597664070125999.
Full textSilveira, Géssica Aparecida [UNESP]. "Influência do manejo do solo em atributos químicos, físicos e microbiológicos dos córregos Jaboticabal e Cerradinho." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132925.
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Atividades agropecuárias contribuem para a degradação das águas, alterando processos físico-químicos e biológicos, principalmente pela ocupação e uso do solo, por processos de lixiviação e/ou erosão. Os objetivos do presente trabalho foram: avaliar a influência do uso do solo na qualidade da água dos córregos Jaboticabal e Cerradinho e estudar o perfil metabólico da população microbiana da água. As coletas (C1 a C6) foram realizadas bimestralmente (Fev a Dez/2014) em oito pontos (P1 a P8), um deles situado na entrada do município de Jaboticabal, no córrego Cerradinho; outro, próximo à nascente do Córrego Jaboticabal; três pontos localizados em área urbana e os demais, em área rural. Foram determinadas variáveis físicas e químicas e a comparação metabólica da população microbiana das amostras de água foi realizada pela avaliação da capacidade de metabolização de diversas fontes de carbono pelo método EcoPlate (Biolog). Os resultados para oxigênio dissolvido, cloreto, nitrito, nitrato, sólidos totais dissolvidos e turbidez, estão de acordo com os valores estabelecidos na resolução 357/2005 do Conselho Nacional do Meio Ambiente (CONAMA), para corpos d´água classe 2. Em todos os pontos e coletas, o teor de fósforo total (Ptotal) excedeu o limite estabelecido pelo CONAMA. Em pontos próximos de atividades agrícolas ocorreram alterações nos valores de variáveis físicas e de variáveis químicas, observando-se resultados elevados para Ptotal e demanda química de oxigênio. A estatística multivariada auxiliou na interpretação dos resultados, mostrando que as atividades antropogênicas afetam a qualidade da água. O estudo de comparação das populações microbianas pela análise da capacidade de metabolização de diferentes fontes de carbono mostrou que a população microbiana da água parece não estar sendo alterada pelas atividades agrícolas. O perfil metabólico da população bacteriana das amostras não apresentou correlação com a presença das atividades agrícolas, os resultados mostram diferenças entre as coletas, mas não entre os pontos de amostragem. Atividades agropecuárias contribuem para a degradação das águas. Metais incorporados no solo, devido a diferentes manejos, podem ser transportados para as águas superficiais por processos de lixiviação e/ou erosão contaminando-as. Bactérias resistentes a metais podem ser utilizadas em processos de biorremediação. Objetivos: determinar as concentrações de metais traço em dois corpos d´água e no seu sedimento e isolar micro-organismos presentes na água para testes de resistência aos metais. As coletas de água (C1 a C6) foram realizadas bimestralmente (fevereiro a dezembro/2014) em oito pontos (P1 a P8). Um deles situado na entrada do município de Jaboticabal, no córrego Cerradinho; outro, próximo à nascente do Córrego Jaboticabal; três pontos localizados em área urbana e os demais, em área rural. O sedimento foi coletado na C6 nos pontos P3, P4, P6, P7 e P8. Nas amostras de água e sedimento foram determinadas as concentrações de cobre, cádmio, zinco, chumbo, níquel e cromo. Visando relacionar os teores de metais encontrados na água com os presentes no solo do entorno, foram coletadas (em fevereiro e agosto/2014), amostras de solo, em doze pontos (PS1 a PS12): PS1, PS2 e PS3, distantes do córrego Jaboticabal; PS4, PS5 e PS6 em área de plantação; PS7, PS8, PS9, PS10, PS11 e PS12, nas matas ciliares presentes nas imediações do córrego Jaboticabal. Foram isolados 182 micro-organismos das amostras de água e submetidos a testes de resistência aos metais estudados em meio de cultivo contendo diferentes concentrações (1, 2, 3, 4 e 5 mmol L-1) dos metais. Em pontos próximos ao córrego Jaboticabal foi possível observar maiores concentrações de metais no solo que, portanto, pode afetar a qualidade da água por meio de processos de erosão e/ou lixiviação, promovendo aumento da concentração de metais no corpo d’ água. Para a água observou-se reta de tendência com aumento nas concentrações de cádmio, cobre e cromo nos pontos da área agrícola (P6, P7 e P8). No sedimento, as maiores concentrações de metais foram encontradas em área agrícola evidenciando que o córrego está sendo impactado. Os micro-organismos isolados mostraram capacidade de se desenvolver mesmo na maior concentração estudada (5 mmol L-1) em proporções diferentes: para Zn (62,1%) e Pb (92,9%), Cd (32,4%) e Ni (29,7%), Cu (0,5%) e Cr (0%). Dos isolados resistentes 35 se desenvolveram em meio com quatro metais (Cd, Zn, Pb e Ni), mas apenas 1 isolado apresentou resistência aos cinco metais (Cu, Cd, Zn, Pb e Ni). Os microrganismos isolados precisam ser identificados e poderão ser utilizados em processos de biorremediação.
Farming activities contribute significantly to water degradation through alterations in physico-chemical and biological properties, which are mainly derived from land use and occupation as well as processes such as leaching and/ or erosion. This paper focused on assessing the influence of soil use on the water quality of surface waters of Jaboticabal and Cerradinho streams and study the metabolic profile of microbial communities found in this water body. Sampling dates (C1 to C6) were carried out bimonthly (from February to December of 2014) at eight different points (P1 to P8). One of these areas was set at the entrance of Jaboticabal city in Cerradinho stream. Another point lies near the source of the Jaboticabal stream. Three points were set within the urban area and the others within the rural area of Jaboticabal. Water physical and chemical variables were assessed. Moreover, we compared the ability of microorganisms to metabolize different sources of carbon using the Ecoplate method (Biolog). The results on dissolved oxygen, chloride, nitrite, nitrate, total dissolved solids and turbidity are in accordance with standards established by resolution number 357/ 2005 of the National Council on the Environment (CONAMA) for class 2 water bodies. The concentration of total phosphorus (TP) exceeded the limit value set by the CONAMA. We also noted significant changes on physical and chemical variables in areas near agricultural activities such as alterations of TP and chemical oxygen demand. Multivariate statistics assisted on data interpretation and showed the influence of human activities on water quality. Furthermore, the comparisons among microbial communities via study of metabolization of various carbon sources proved that farming activities have not affected the population structures. Therefore, the bacterial metabolic profile had no association with farming practices; however, the results showed differences among sampling dates, but not referring to the sampling points. Agricultural activities contribute to the degradation of the water bodies. Metals incorporated into the soil, due to different management, can be transported to the surface waters through the processes of lixiviation and / or erosion, contaminating them. Bacteria which are resistant to metals can be used in the bioremediation processes. Objectives: To determine the concentrations of trace metals in two a bodies of water and its sediment and isolate micro-organisms present in the water for testing their resistance to metals. The water sampling dates (C1 to C6) were carried out bimonthly (from february to december of 2014) at eight different points (P1 to P8). One of these areas was set at the entrance of Jaboticabal city in Cerradinho stream. Another point lies near the source of the Jaboticabal stream. Three points were set within the urban area and the others within the rural area of Jaboticabal. The sediment was sampling dates in C6 in the points P3, P4, P6, P7 and P8. For the water and sediment samples were determined the concentrations of copper, cadmium, zinc, lead, nickel and chromium. Aiming to relate the the levels of metals found in water with the ones present in the soil from the surroundings, were collected (in february and august / 2014), samples of the soil in twelve points (PS1 to PS12): PS1, PS2 and PS3, far from the stream Jaboticabal; PS4, PS5 and PS6 in plantation areas; PS7, PS8, PS9, PS10, PS11 and PS12,in riparian forests present in the stream nearby. 182 micro-organisms from the samples were isolated in the water samples and tested for resistance to the metals in culture media containing different concentrations(1, 2, 3, 4 and 5 mmol L-1) of metals. At points near the stream it was possible to observe higher metal concentrations in soil, therefore, may affect the quality of water through erosion and / or leaching, promoting increased concentration of metals in the body of water. For the water, the trend was observed with the increase in the concentrations of cadmium, copper and chromium in points of the agricultural area (P6, P7 and P8). In the sediment, the highest concentrations of metals were found in agricultural areas, showing that the stream is being impacted. The micro-organisms isolated showed the same ability to grow even in the highest concentration studied (5 mmol L-1) in different proportions: for Zn(62.1%) and Pb (92.9%), Cd (32.4%) and Ni (29.7%), Cu (0.5%) and Cr (0%). From the 35 isolated resistant organisms developed in medium with four metals (Cd, Zn,Pb and Ni), but only one isolate was resistant to the five metals (Cu,Cd, Zn, Pb and Ni). The microorganisms need to be identified and will be able to be used in bioremediation processes.
Sze-To, Lap, and 司徒立. "The structural chemistry of coordination compounds containing d-block or f-block metals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45204470.
Full textKraemer, Ute. "Nickel hyperaccumulation in the genus Alyssum L." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318487.
Full textChoi, Yuk-ning Alta. "Repair technology for cracked metallic structures using composite materials /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21213239.
Full textLee, Yew-wing. "The effect of cold rolling on the formability of thermoplastics /." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12334364.
Full textThuramalla, Naveen. "Multiscale modeling and analysis of failure and stability during super plastic deformation -- under different loading conditions." Lexington, Ky. : [University of Kentucky Libraries], 2004. http://lib.uky.edu/ETD/ukymeen2004t00171/NAVEEN.pdf.
Full textTitle from document title page (viewed Jan. 5, 2005). Document formatted into pages; contains x, 112p. : ill. Includes abstract and vita. Includes bibliographical references.
Bernard, III William J. "The Continuous Rheoconversion Process: Scale-up and Optimization." Digital WPI, 2005. https://digitalcommons.wpi.edu/etd-theses/957.
Full textProuff, N. "Oxidation of metals." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377188.
Full textCarr, A. J. "New hard metals." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373069.
Full textNgwanakgagane, Sentsho Zelda. "Hydrogenisation of metals." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/4430.
Full textTransition metals are a group of metals which are light in weight and have high hydrogen solubility. Their interaction with hydrogen is exorthermic and this phenomenon makes them “ideal” candidates for various applications of hydrogen storage systems. This explains why the phenomenon of hydrogen storage in Pd is used as a model for hydrogen storage systems because of the nature of absorption associated with it (like a sponge even at low temperatures). The hydrogenation process can be conducted at either room or high temperatures in a furnace under low pressure-low hydrogen gas concentration-short hydrogenation time (LP-LC-ST) and in intelligent gravimetric analyser under high pressurehigh hydrogen gas concentration-long hydrogenation time conditions. Most of the research on hydrogen storage sytems is based on gravimetric analysis of absorbed and desorbed hydrogen concentration. In this work, a comparison study of the hydrogen content in pure Pd, Pd-Pt coated systems, Pd-Pt alloys, commercially pure Ti and Ti-6Al-4V alloy determined by gravimetric methods and elastic recoil detection analysis (which is based on the detection of recoiled hydrogen after interaction with He+ ions) technique was investigated. The changes in the structural properties and the hydrogen content of the materials when exposed to a hydrogen gas environment for different durations at various system temperatures and pressures will be reported. These changes have an effect on the microstructure of CP-Ti and Ti-6Al-4V alloy and structural properties of all the hydrogenated materials. The results obtained from optical microscopy, scanning electron microscopy, x-ray diffraction, intelligent gravimetric analyser, digital balance, elastic recoil detection analysis and Vickers hardness test, show the following: it is found that hydrogenation of Pd at elevated temperatures (550 ˚C and 650 ˚C) does not yield hydrides under LP-LC-ST conditions. However, at room temperature the absorption of hydrogen occurred faster at the beginning of the process. Furthermore, the absorption of hydrogen increased with pressure where optimum absorption (0.67 wt. % hydrogen concentration) occurred under a system pressure of 2000 mbar. After pressure release, the remaining hydrogen content in the Pd sample was 0.6 wt. %. The Pd-Pt coated system provide hydrogen mobility at 550 and 650 ˚C where hydrides were formed under LP-LC-ST conditions. In addition to the decrease of hydrogen solubility in Pd-Pt alloys with an increase in Pt content, the probability of the alloys to achieve full saturation also decreases with an increase in Pt content under HP-HC-LT conditions. CP-Ti and Ti-6Al-4V alloy absorb substantial amount of hydrogen in the first hour of room temperature hydrogenation under LP-LC-ST conditions but hydrides were not formed. Therefore, under LP-LC-ST conditions at room temperature, Pd is able to store hydrogen in the form of hydrides whereas Ti and Ti-6Al-4V alloy could not. The 550 ˚C is the optimum temperature for hydrogenation of CP-Ti under LP-LC-ST conditions. The Ti- 6Al-4V alloy absorb optimum hydrogen at 650 ˚C under LP-LC-ST conditions. Consequently, the change of microhardness of CP-Ti and Ti-6Al-4V alloy was found to depend on hydrogenation temperature.
Kart, Hasan Huseyin. "Molecular Dynamics Study Of Random And Ordered Metals And Metal Alloys." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605467/index.pdf.
Full textStone, Diane L. "Dendritic metals : biomimicry in a branched shell & metal directed assembly." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274498.
Full textTse, Hiu Wah. "Hydrothermal synthesis of metal carboxylate polymers using high coordination number metals /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202004%20TSE.
Full textBarari, Farzad. "Metal foam regenerators : heat transfer and pressure drop in porous metals." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6366/.
Full textPadavala, Ramesh. "Failure mechanisms in impact erosion of ductile materials." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3539.
Full textTitle from document title page. Document formatted into pages; contains ix, 87 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 66-68).
Nkqenkqa, Vuyiseka. "Metal and microbial contamination of agricultural soil and the Veldwachters River, Stellenbosch, South Africa." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2423.
Full textSurface water is used as a source of water supply in many countries, including South Africa. One of the sources of surface water pollution is leachate and surface runoff from landfills. In agricultural soils, the landfill runoff and leachate deteriorate the quality and affect the fertility of soil. The entry of metals and microorganisms from landfill leachate to adjacent environments is through surface runoff due to rainfall. Adverse effects on human- and environmental health triggers a need to monitor and control contaminants in the environment. The aims of the study are to determine the effect of landfill runoff and leachate on agricultural soil and river water (Veldwachters River) running adjacent to the Devon Valley landfill site and to identify potential metal-tolerant organisms in environmental samples collected in Stellenbosch, Western Cape, South Africa. Samples (agricultural soil, river water and sediments) were collected once a month for a period of six months from the study area for analysis. Physicochemical parameters that are known to have major effects on environmental samples were assessed and the concentrations of various metals (Al, Pb, Cr, Mn, Mo, Co, Ni, Cu, Zn, Fe, Cd and V) were also determined by means of inductively coupled plasma mass spectrometry (ICP-MS). Soil texture analysis was tested in order to monitor the metal distribution in soils under the influence of environmental factors.
Junior, José Paulo Queiroz Prado. "Bactérias fixadoras de nitrogênio em cana-de-açúcar: crescimento em ambiente com altas concentrações de Cd, Cr, Ni e Pb \"in situ\" e \"in vitro\"." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-21092012-131247/.
Full textThe objectives of this study were to evaluate the concentration of Cd, Pb, Cr and Ni in the tissues of sugarcane, noting the presence of the BFN in IAC87-3396 variety grown in contaminated environment and evaluate the BFN tolerance to heavy metals \"in situ\" and \"in vitro\". Sugarcane variety IAC87-3396 was grown in an soil contaminated by metals. Before planting, five mitigators of heavy metals were applied. Analysis were performed to detect nickel, lead, chromium and cadmium in tissues of sugarcane, including leaf +1, roots and pregerminated sett (shoot and root) at harvest of the plant cane and ratoon cane. To quantify the nitrogen-fixing bacteria, three tests were performed comprising the shoots and roots, one in the plant cane (at harvest) and two in ratoon cane (6 months and harvesting) using the methodology of pre-germinated sett. The test \"in vitro\" consisted of adding to the culture medium Pb, Cd, Ni, Cr, mixed metals and inoculated in a petri dish of 4 bacteria (Herbaspirillum seropedicae, Gluconacetobacter diazotrophicus, Azospirillum amazonense and Burkholderia tropica). The behavior in different concentrations was evaluated by assigning values to different growth patterns. For all metals, the highest concentration was found in the roots and the lowest values were found in leaf +1. This values in leaf +1 increased from plant cane to ratoon cane while in root it decreased. In relation to the pregerminated sett, metal concentration in root of plant cane was lower than that found in the field while the leaf had a higher concentration only for Ni and Cd. The field ratoon cane has the highest concentrations for both the aerial and root part. For the quantification of bacteria, the comparison between the measurement periods showed that in general it is greater in the plant cane. The location of bacteria inside the plant revealed that, in the plant cane, it was higher in the shoot. However, for the first six months of ratoon cane the predominance of bacterias was in the root. At harvest of the ratoon crop a more uniform distribution of bacteria was found inside the plant. In the \"in vitro\" essay the maximum concentration studied was the maximum tolerated for Pb (248 mg L-1), Cd (8 mg L-1) and Ni (40 mg L-1). The association between Cr and 2, 3 and 4 metals provided no growth of bacteria. For most of the bacteria a significant association was found between growth patterns and concentrations of metals in the culture medium. All the four kinds of NFB were found in IAC87-3396 even in roots where the levels of Pb, Ni, Cr and Cd were high. The tolerance of the NFB to these metals \"in situ\" is different from that \"in vitro\". The chromium and its association with other metals have limited growth \"in vitro\" of all bacteria. The methodology of pre-germinated sett did not reflect the conditions of metal concentration in material collected in the field. Sugarcane plant has the potential to be a culture of phytoextraction and accumulation of Pb, Ni, Cr and Cd
Caporalin, Carolina Baldin [UNESP]. "Comparação da biossorção de metais terras-raras pela biomassa melanizada do fungo Aspergillus nidulans nas formas livre e imobilizada." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/88024.
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Os metais terras-raras (TRs) apresentam um alto valor agregado, o qual não provém de sua baixa ocorrência mineral, mas sim da dificuldade na separação destes pelos métodos clássicos, uma vez que os elementos desta série apresentam semelhantes comportamentos físico-químicos. Desta maneira, altos custos são despendidos anualmente para a obtenção das TRs na forma pura, sendo esta necessária para as suas aplicações tecnológicas. Uma alternativa a esta problemática é o emprego da biossorção, a qual apresenta potencial aplicação para a extração e separação de metais valiosos, por ter como vantagem uma alta eficiência agregada a um baixo custo. Alguns requisitos são necessários para que o processo de biossorção possa ter competitividade técnica e econômica, tais como, o material biológico empregado deve apresentar um baixo custo, sendo assim necessário estabelecer as condições ótimas de cultivo do micro-organismo para sua produção em larga escala, e também a utilização do biossorvente na forma imobilizada possibilita seu uso como um adsorvente convencional, o qual apresenta tamanho desejado, alta porosidade e um bom desempenho físicoquímico. Por esta razão, o presente trabalho teve como principal objetivo avaliar a potencialidade de utilização da biomassa melanizada (inativa) obtida da linhagem mutante MEL 1 do fungo Aspergillus nidulans, na sua forma livre e imobilizada, no processo de biossorção dos metais terras-raras neodímio, lantânio e cério em soluções monometálicas. Com os resultados obtidos foi possível estabelecer a condição ótima de cultivo da linhagem MEL 1 do A. nidulans que proporcionou uma biomassa mais melanizada, a qual apresentou uma maior capacidade biossortiva. Para tal condição, a massa micelial obtida após o crescimento do fungo por três dias, sob agitação à...
The rare-earth metals (TRs) have a high added value, which does not come from its low mineral occurrence, but the difficulty in separating these by classical methods, since the elements of this series show similar physical and chemical behavior. Thus, high costs are spent annually to obtain the TRs in pure form, which is necessary for their technological applications. An alternative to this problem is the use of biosorption, which has potential application for extraction and separation of valuable metals, having the advantage of a high aggregate efficiency at a low cost of production. Some requirements are necessary for the biosorption process may have technical and economic competitiveness, such as the biological material used must be low cost and it is necessary to establish the optimum conditions for cultivation of the microorganism to its large scale production, and also the use of biosorbent immobilized in the form enables its use as a conventional adsorbent, which has the desired size, high porosity and good physical and chemical performance. For this reason, this study aimed to evaluate the potential use of biomass melanized inactive mutant of the fungus Aspergillus nidulans MEL1 in its free form and immobilized in calcium alginate, in the process of biosorption of neodymium rare-earth metals, lanthanum and cerium. The results concerning the kinetics of biosorption showed that the ability of TRs biosorptive varied between different forms of biomass, and this capacity was higher compared to free biomass immobilized. Regarding the maximum biosorption capacity (Qmax), we observed that the immobilized biomass caused a reduction in Qmax of lanthanum and neodymium in approximately 60 and 33% respectively, have kept their Ce Qmax for both types of biomass (open and immobilized). The affinity of biomass... (Complete abstract click electronic access below)
Soares, Isaac Vaz [UNESP]. "Síntese e caracterização de silsesquioxanos organofuncionalizados: aplicações em adsorção, pré-concentração e catálise." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/97901.
Full textEste trabalho descreve as sínteses e caracterizações de silsesquioxanos organofuncionalizados com tiouréia (T8-Pr-TU), 2,2’-dipiridilamina (T8-Pr-DPA) e 2-Amino-1,3,4-Tiadiazol (T8-Pr-ATD). Os materiais foram caracterizados por: espectroscopia na região do infravermelho (FTIR), ressonância magnética nuclear 29Si e 13C no estado sólido (RMN) e análise elementar. Nos estudos de batelada para os materiais, foram utilizados os íons metálicos de Cd (II), Cu (II), Ni (II) e Co (II) e os solventes foram água e etanol. Determinou-se a dose de adsorvente na solução e o tempo de equilíbrio, na qual, para o material T8-Pr-TU em todos os meios e metais, a capacidade máxima de adsorção ocorreu em 50 mg de adsorvente, e o equilíbrio de adsorção foi de aproximadamente 9 minutos para todos os solventes e íons metálicos, enquanto que, para o T8-Pr-DPA em todos os meios e metais, a capacidade máxima de adsorção ocorreu com 10 mg de adsorvente e tempo de equilíbrio de 10 minutos; já para o T8-Pr-ATD, independentemente do solvente e dos metais, a capacidade máxima de adsorção foi em 50 mg de adsorvente e tempo de equilíbrio de 10 minutos. Estudou-se ainda a capacidade máxima de adsorção (Nf) para os solventes, na qual a capacidade máxima se deu em meio etanólico > aquoso. O efeito dos contra-íons Cl-, Br- e ClO4- foi estudado para todos os materiais, na qual observou-se que para os três adsorventes a capacidade de adsorção seguiu a seguinte ordem: Cl- > Br- > ClO4-. Em seguida, as isotermas de adsorção foram ajustadas pelos modelos Langmuir, Freundlich, Temkin e Dubinin-Radushkevich (D-R). Para cinética de adsorção dos metais, foram usados três modelos cinéticos como pseudo-primeira-ordem, pseudo-segunda-ordem e Elovich. Os modelos de Langmuir e Elovich foram os mais apropriados para descrever os dados...
This work describes the synthesis and characterization of silsesquioxanes organofuncionalizados with thiourea (T8-Pr-TU), 2,2 '-dipyridylamine (T8-Pr-DPA) and 2-Amino-1,3,4-thiadiazole (T8-Pr-ATD). The materials were characterized by infrared spectroscopy (FTIR), nuclear magnetic resonance 29Si and 13C solid state (NMR) and elemental analysis. In studies to batch materials were used for metal ions of Cd (II), Cu (II), Ni (II) and Co (II) and the solvents were water and ethanol. It was determined the dose of adsorbent in the solution and equilibrium time in which, for the material T8-Pr-TU in all ways and metals, the maximum adsorption capacity observed in 50 mg of adsorbent, and adsorption equilibrium was about 9 minutes for all metal ions and solvents, whereas for T8-Pr-DPA in all ways and metals, the maximum adsorption capacity was 10 mg of adsorbent and equilibration time of 10 minutes, whereas for T8-Pr-DPA, regardless of solvent and metals, the maximum adsorption capacity was 50 mg of adsorbent and equilibration time of 10 minutes. It was also studied the maximum adsorption capacity (Nf) for solvents, in which the maximum capacity was in ethanolic > aqueous. The effect of the counter ions Cl-, Br-and ClO4- was studied for all materials in which it was observed that the three adsorbents for the adsorption capacity followed the order: Cl-> Br-> ClO4-. Then the adsorption isotherm models were fitted by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DR). For adsorption kinetics of metals, three kinetic models were used as pseudo-first-order, pseudo-second-order and Elovich. The Langmuir model and Elovich were most suitable to describe the data and kinetics of adsorption, respectively, of all materials. From the model isotherm DR, one can calculate the free energy (E)... (Complete abstract click electronic access below)
Botega, Daniela Maffei 1977. "Resistencia a tração do titanio comercialmente puro soldado a laser em diferentes distancias e diametros." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289921.
Full textTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Este trabalho avaliou a resistência à tração e alongamento de amostras de diferentes diâmetros (1,5, 2,0 e 5,0 mm) fundidas em titânio comercialmente puro (Tritan - Dentaurum), submetidas a soldagem a laser em diferentes distâncias de soldagem (0,0 mm e 0,6 mm). Foram confeccionadas 45 amostras, separadas em 9 grupos (n= 5): G1) diâmetro 1,5 mm controle (não submetidas à soldagem); G2) diâmetro 1,5 mm e distância zero; G3) diâmetro 1,5 mm e distância 0,6 mm; G4) diâmetro 2,0 mm (controle); G5) diâmetro 2,0 mm e distância zero; G6) diâmetro 2,0 mm e distância 0,6 mm; G7) diâmetro 5,0 mm (controle); G8) diâmetro 5,0 mm e distância zero; e G9) diâmetro 5,0 mm e distância 0,6 mm. Após a fundição, todas as amostras, exceto as dos grupos controle, foram seccionadas e unidas, utilizando-se resina acrílica autopolimerizável, para a soldagem com as seguintes especificações: 320V / 9 milisegundos (ms) (amostra de 1,5mm), 330V / 9 ms (amostra de 2,0mm) e 350V / 9 ms (amostra de 5,0mm) em um aparelho de soldagem a laser Desktop-F (Dentaurum KG). Após a soldagem, foram submetidas ao ensaio de resistência à tração até a ruptura em máquina servohidráulica (MTS 810) com velocidade de 1mm/min. As superfícies de fratura foram analisadas em microscópio eletrônico de varredura (M.E.V. ¿ JEOL). Os resultados foram submetidos à Análise de Variância e teste de Tukey (p<0,05). Os valores médios de resistência máxima à tração (MPa) revelaram que o grupo controle apresentou valores, para todos os diâmetros, estatisticamente superiores aos grupos experimentais, que não diferiram entre si, exceto para 5,0 mm de diâmetro, onde a distância de 0,6 mm apresentou maiores valores (G1- 595,64; G2- 496,46; G3- 441,04; G4- 516,54; G5- 397,85; G6- 442,15; G7- 560,19; G8- 200,88; e G9- 316,04). Os valores médios de alongamento (mm) para o grupo controle foram estatisticamente superiores aos experimentais nos diâmetros 2,0 e 5,0 mm, não havendo diferença entre os grupos no diâmetro 1,5 mm. Não houve diferença estatística entre os grupos experimentais (G1- 1,68; G2- 1,47; G3- 1,20; G4- 2,61; G5- 1,34; G6- 1,05; G7- 2,51; G8- 0,92; e G9- 1,32). As imagens revelaram eficiente penetração do laser nas amostras de 1,5 e 2,0 mm de diâmetro, e insuficiente nas de 5,0 mm de diâmetro. A resistência à tração para todos os diâmetros e o alongamento para os diâmetros 2,0 e 5,0 mm foram influenciados pela técnica de soldagem a laser de forma significativa. Dentre as amostras de 5,0 mm de diâmetro submetidas à soldagem a laser, aquelas com distância de 0,6 mm entre as partes apresentaram maior alcance do feixe de laser
Abstract: The aim of this study was to evaluate the tensile strength and elongation of commercially pure titanium samples (Tritan - Dentaurum), with 3 diameters (1.5, 2.0 and 5.0 mm of diameter x 42 mm length), submitted to laser welding in 2 distances of soldering (0.0 mm and 0.6 mm). 45 samples were made (dumbbell), divided in 9 groups (5 each): G1) 1.5 mm control (without welding procedures); G2) 1.5 mm and no distance; G3) 1.5 mm and 0.6 mm of distance; G4) 2.0 mm (control); G5) 2.0 mm and no distance; G6) 2.0 mm and 0.6 mm; G7) 5.0 mm (control); G8) 5.0 mm and no distance; G9) 5.0 mm and 0.6 mm of distance. After casting, all the samples, except control groups, were sectioned and joined with self curing acrylic resin for the welding procedures, as follows: 320V/9 miliseconds (ms) (samples of 1.5mm), 330V/9ms (samples of 2.0 mm) and 350V/9ms (samples of 5.0 mm) using a laser welding machine Desktop-F (Dentaurum KG). After soldering, the samples were submitted to tensile test using a servohidraulic machine MTS-810 with speed of 1mm/min. The fractured surfaces were microscopically analyzed (M.E.V. ¿ JEOL). Data were submitted to ANOVA and Tukey¿s test (p<0.05). The tensile strength mean values (MPa) for control group were statistically higher than the experimental groups, which did not differ from each other, except for 5.0 mm group, in which the samples with 0.6 mm of distance had the highest values (G1- 595.64; G2- 496.46; G3- 441.04; G4- 516.54; G5- 397.85; G6- 442.15; G7- 560.19; G8- 200.88 and G9- 316.04). The mean values of elongation (mm) for the control group were statistically higher than experimental groups in the 2.0 and 5.0 mm, having no difference for the groups with 1.5 mm. There was no difference between the experimental groups (G1- 1.68; G2- 1.47; G3- 1.20; G4- 2.61; G5- 1.34; G6- 1.05; G7- 2.51; G8- 0.92; and G9- 1.32). The SEM images showed a good penetration of laser in the samples of 1.5 and 2.0 mm of diameter, and insufficient penetration of laser in the samples of 5.0 mm. Ductile fractures were predominant in all groups with the presence of dimples. Laser welding procedure is an effective method of joining titanium, however, caused a decrease in the values of tensile strength for all diameters and elongation for 2.0 and 5.0 mm. Among the 5.0 mm samples submitted to laser welding procedures, the laser welding was more effective for the samples with distance of 0.6 mm between the parts
Doutorado
Protese Dental
Doutor em Clínica Odontológica
Barros, Arielle Muniz de. "Bioadsorção e dessorção dos íons 'Cd POT. 2+', 'Cu POT. 2+' , 'Ni POT. 2+', 'Pb POT. 2+' e 'Zn POT. 2+' pela macrófita aquáica Azolla pinnata." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266685.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Pesquisas no campo da tecnologia têm buscado avaliar técnicas e/ou processos econômicos e eficientes para o tratamento de efluentes que contenham metal pesado. Atualmente a bioadsorção vem se apresentando como uma boa alternativa às tecnologias existentes. Este trabalho teve como objetivo a investigação da macrófita Azolla pinnata como bioadsorvente de cinco íons metálicos: Cd2+, Cu2+, Ni2+, Pb2+ e Zn2+ em soluções sintéticas. A caracterização do biomaterial foi realizada utilizando-se técnicas como Microscopia Eletrônica de Varredura (MEV) para análise da superfície do material; análise de Espectroscopia de Energia Dispersiva de Raios-X (EDX), que mostrou que qualitativamente a diminuição de íons de competição (Ca, Na e K) após o processo de adsorção, evidenciando que a troca iônica pode ser um dos mecanismos do processo; e análise de Infravermelho por Transformada de Fourier (FTIR), em que se pôde constatar que alguns grupos funcionais como carboxilas e grupos sulfonados são fundamentais no processo. A cinética de adsorção foi ajustada pelos modelos de pseudoprimeira e pseudossegunda ordem, sendo que o melhor ajuste variou de acordo com o íon estudado. O modelo de difusão intrapartícula mostrou que muitos mecanismos podem ser limitantes na taxa com a qual ocorre o processo. Os dados de equilíbrio foi ajustado pelos modelos de isoterma de Langmuir e de Freundlich em duas temperaturas, 25 e 45 ºC. O processo foi favorecido pelo acréscimo de temperatura para todos os íons. O modelo de Langmuir se ajustou melhor aos dados experimentais de todos os íons e o valor de capacidade máxima de adsorção (qmax) a 25 ºC foi de 0,359; 0,448; 0,254; 0,472 e 0,357 mmol/g para Cd2+, Cu2+, Ni2+, Pb2+ e Zn2+, respectivamente. Os eluentes HCl, EDTA e CaCl2 foram testados no processo de dessorção em batelada e o cloreto de cálcio se mostrou eficiente além de não causar danos ao material nem diminuir a capacidade de adsorção da macrófita. Ensaios dinâmicos em coluna de leito fixo foram realiados para os íons Cu2+ e Pb2+ com soluções mono e bicomponentes. Nos ensaios em sistema binários, pode-se constatar uma grande preferência pela adsorção de íons chumbo e, portanto, uma grande queda na adsorção de cobre. Foram testados ciclos de adsorção/dessorção em coluna utilizando o CaCl2 como eluente e, em três ciclos, a macrófita manteve suas propriedades adsortivas. Com estes resultados, pode-se constatar que a realização deste trabalho contribuiu para a avaliação deste material como bioadsorvente alternativo e que, especificamente, macrófita A. pinnata mostrou-se atrativa para utilização nos processos de tratamento e/ou estabilização de metais pesados presentes em baixas concentrações em efluentes industriais
Resumo: No processo Kraft para produção de papel e celulose, os cavacos de madeira são cozidos em um digestor com uma solução aquosa denominada licor branco, constituída de hidróxido de sódio (NaOH) e sulfeto de sódio (Na2S). Durante o cozimento uma pasta fibrosa é produzida. Esta pasta é filtrada e segue para o branqueamento. O produto filtrado chama-se licor negro, devido à mudança da sua cor nesta etapa. O licor negro possui aproximadamente 15 % de sólidos em massa. Ele é bombeado para a unidade de recuperação, na qual ele será concentrado em evaporadores de múltiplosefeitos até 75 % de sólidos em massa. Em seguida, ele é bombeado para uma caldeira onde é queimado, para recuperar os sais inorgânicos e, principalmente, fornecer calor para geração de calor. Durante a evaporação do licor negro, quando a porcentagem em sólidos ultrapassa 50 %, ocorre a precipitação de sais inorgânicos. Estes sais se depositam nas superfícies de troca térmica dos evaporadores diminuindo sua eficiência e causando prejuízos à indústria. Os principais sais que causam este problema são o carbonato de sódio (Na2CO3) e o sulfato de sódio (Na2SO4). O objetivo do presente trabalho foi testar e validar um método experimental para a determinação da quantidade de Na2CO3 presente em amostras industriais de licor negro. Além disso, também foram analisadas algumas propriedades físico-químicas do licor negro, como massa específica, teor de sólidos e viscosidade. Com os resultados obtidos, tentou-se obter uma correlação entre o teor de carbonato de sódio e as demais propriedades do licor que foram determinadas. Os resultados das análises das características físico-químicas demonstraram coerência e boa reprodutibilidade, porém, os resultados das análises de teor de carbonato de sódio não foram satisfatórios e mostraram que a técnica deve ser aperfeiçoada
Abstract: Research in the technology field has been looking for evaluating efficient and economic techniques and/or process for effluents that contains heavy metal. The biodsorption process has been seemed as a good alternative to the existing technology. This work had the aim to investigate the use of Azolla pinnata macrophyte as biosorbent of five metallic ions: Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+ in synthetic solutions. The biomaterial characterization was carried out by techniques as scanning electron microscopy (SEM) for the analyze of material superficies; the energy dispersive X-ray spectroscopy (EDX), which showed, qualitatively, a decreasing in the competitions ions (Ca, Na e K) after the sorption process, indicating that the ion exchange can be one o the process mechanism; and Fourier Transform Infrared Spectroscopy (FTIR), in which it was possible implied functional groups as carboxyl and sulfonate play a important role in the adsorption. The kinetics was adjusted by primer and second order models and the model which fit better depends on each ion. The intra-particle diffusion model showed that several mechanisms may be limiting to the process rate. The equilibrium data were adjusted by Langmuir and Freundlich models in two temperatures: 25 and 45 ºC. The process was favored by the increasing in the temperature for all five ions. The Langmuir model fit better the experimental data and the maximum adsorption capacity (qmax) were 0,359; 0,448; 0,254; 0,472 and 0,357 mmol/g for Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+, respectively. The HCl, EDTA and CaCl2 eluents were tested in the desorption process and the calcium chloride was efficient and did not cause any damage in the biomaterial or decreasing the biosorption capacity. Dynamics runs were carried out in fixed-bed in mono and bi-components solutions. In the binary were found a great preference for lead instead of copper and as a result, a significant decrease in the removal of copper. Adsorption/desorption cycles were tested in fixed-bed system using CaCl2 as eluent. After three cycles no damage, weight lost or significant decrease in the biosorption capacity was noticed. These results indicating that the A.pinnata macrophyte is an attractive potential new biosorbent to be used in heavy metal removal especially in low concentrations effluents
Abstract: In the Kraft process for pulp and paper production, wood chips are cooked in a digester with an aqueous solution named white liquor, consisted by sodium hydroxide (NaOH) and sodium sulfide (Na2S). During this cooking process, wood chips are transformed generating a fibrous paste and a liquid solution. This paste is filtered and separated from the liquid solution, named black liquor due to its color. The paste goes to the bleaching stage to produce cellulose. Black liquor contains inorganic and organic (mainly lignin) compounds from wood. Initially this black liquor contains approximately 15 mass/% of solids and is sent to the recovery unit to have this concentration raised to approximately 75 mass/% to be burned in a recovery boiler in order to generate power and recover inorganic reactants, recycling them to the process. The concentration process of black liquor occurs in a multiple effect evaporators unit. During this process, when the concentration of solids exceeds 50%, the precipitation of inorganic salts (mainly Na2CO3 and Na2SO4) begins. These salts are deposited in the heat transfer surfaces of the evaporator tubes, reducing their efficiency, leading to a reduction in the production capacity. The scope of this work was testing and validate an experimental method to estimate the content of Na2CO3 present in industrial black liquor samples. Moreover, some black liquor's physical-chemical properties as density, solids content and viscosity were also analyzed. An attempt to develop a predictive model to evaluate sodium carbonate content from the other properties was made. The results obtained for physical-chemical properties have shown a good consistency. However, the results of sodium carbonate analyses were not satisfactory, showing that the technique must be improved
Mestrado
Engenharia de Processos
Mestra em Engenharia Química
Bourlegat, Fernanda Melo Le. "Disponibilidade de metais em amostras de fosfogesso e fertilizantes fosfatados utilizados na agricultura." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-10082011-093830/.
Full textThe Brazilian phosphate fertilizer is obtained by wet reaction of the igneous phosphate rock with concentrated sulphuric acid, giving as final product, phosphoric acid, and dehydrated calcium sulphate (phosphogypsum) as by-product. Part of this phosphogypsum is stored in stacks at open air and part has been used in agriculture, as soil amendment. To assure a safe utilization of phosphogypsum it is important to determine the levels of impurities, particularly of metals, present in phosphogypsum. In this paper, the concentration of metals (As, Ba, Cd, Cr, Co, Cu, Hg, Ni, Pb, Se, Zn and rare earth elements) present in Brazilian phosphogypsum and also in single super phosphate (SSP), triple super phosphate (TSP), monoammonium phosphate (MAP) and diammonium phosphate (DAP) were determined. The metals Cd, Cu, Ni, Pb and Zn were determined following the procedure EPA 3052. The same elements, As and Se were also determined following the procedure EPA 3050B, recommended by Ministério da Agricultura, Pecuária e Abastecimento (MAPA). All these metals are controlled by environmental and agriculture regulation institutes in Brazil. The concentrations obtained for the metals analyzed by using the two procedures were different. Ba, Co, Cr and rare earth elements were determined by neutron activation analysis. In order to evaluate the availability of these metals As, Cd, Cr, Co, Cu, Ni, Pb, Se and Zn to the environment, the content of the same elements were determined following a procedure established by the EC (European Community), which includes an initial attack of the samples with EDTA-NH4 0.05M, at pH 7.0. In all these cases, phosphogypsum presented metals concentration lower than the phosphate fertilizers, and the results are below the limits adopted by MAPA and Companhia Ambiental do Estado de São Paulo (CETESB). The results obtained using the methodology with mild attack show that the metals are not available to the environment, giving evidence that the application of phosphogypsum in agriculture is safe as far as contamination by metals.
Soares, Isaac Vaz. "Síntese e caracterização de silsesquioxanos organofuncionalizados : aplicações em adsorção, pré-concentração e catálise /." Ilha Solteira, 2013. http://hdl.handle.net/11449/97901.
Full textBanca: Fauze Ahmad Aouada
Banca: Douglas Cardoso Dragunski
Resumo: Este trabalho descreve as sínteses e caracterizações de silsesquioxanos organofuncionalizados com tiouréia (T8-Pr-TU), 2,2'-dipiridilamina (T8-Pr-DPA) e 2-Amino-1,3,4-Tiadiazol (T8-Pr-ATD). Os materiais foram caracterizados por: espectroscopia na região do infravermelho (FTIR), ressonância magnética nuclear 29Si e 13C no estado sólido (RMN) e análise elementar. Nos estudos de batelada para os materiais, foram utilizados os íons metálicos de Cd (II), Cu (II), Ni (II) e Co (II) e os solventes foram água e etanol. Determinou-se a dose de adsorvente na solução e o tempo de equilíbrio, na qual, para o material T8-Pr-TU em todos os meios e metais, a capacidade máxima de adsorção ocorreu em 50 mg de adsorvente, e o equilíbrio de adsorção foi de aproximadamente 9 minutos para todos os solventes e íons metálicos, enquanto que, para o T8-Pr-DPA em todos os meios e metais, a capacidade máxima de adsorção ocorreu com 10 mg de adsorvente e tempo de equilíbrio de 10 minutos; já para o T8-Pr-ATD, independentemente do solvente e dos metais, a capacidade máxima de adsorção foi em 50 mg de adsorvente e tempo de equilíbrio de 10 minutos. Estudou-se ainda a capacidade máxima de adsorção (Nf) para os solventes, na qual a capacidade máxima se deu em meio etanólico > aquoso. O efeito dos contra-íons Cl-, Br- e ClO4- foi estudado para todos os materiais, na qual observou-se que para os três adsorventes a capacidade de adsorção seguiu a seguinte ordem: Cl- > Br- > ClO4-. Em seguida, as isotermas de adsorção foram ajustadas pelos modelos Langmuir, Freundlich, Temkin e Dubinin-Radushkevich (D-R). Para cinética de adsorção dos metais, foram usados três modelos cinéticos como pseudo-primeira-ordem, pseudo-segunda-ordem e Elovich. Os modelos de Langmuir e Elovich foram os mais apropriados para descrever os dados... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work describes the synthesis and characterization of silsesquioxanes organofuncionalizados with thiourea (T8-Pr-TU), 2,2 '-dipyridylamine (T8-Pr-DPA) and 2-Amino-1,3,4-thiadiazole (T8-Pr-ATD). The materials were characterized by infrared spectroscopy (FTIR), nuclear magnetic resonance 29Si and 13C solid state (NMR) and elemental analysis. In studies to batch materials were used for metal ions of Cd (II), Cu (II), Ni (II) and Co (II) and the solvents were water and ethanol. It was determined the dose of adsorbent in the solution and equilibrium time in which, for the material T8-Pr-TU in all ways and metals, the maximum adsorption capacity observed in 50 mg of adsorbent, and adsorption equilibrium was about 9 minutes for all metal ions and solvents, whereas for T8-Pr-DPA in all ways and metals, the maximum adsorption capacity was 10 mg of adsorbent and equilibration time of 10 minutes, whereas for T8-Pr-DPA, regardless of solvent and metals, the maximum adsorption capacity was 50 mg of adsorbent and equilibration time of 10 minutes. It was also studied the maximum adsorption capacity (Nf) for solvents, in which the maximum capacity was in ethanolic > aqueous. The effect of the counter ions Cl-, Br-and ClO4- was studied for all materials in which it was observed that the three adsorbents for the adsorption capacity followed the order: Cl-> Br-> ClO4-. Then the adsorption isotherm models were fitted by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DR). For adsorption kinetics of metals, three kinetic models were used as pseudo-first-order, pseudo-second-order and Elovich. The Langmuir model and Elovich were most suitable to describe the data and kinetics of adsorption, respectively, of all materials. From the model isotherm DR, one can calculate the free energy (E)... (Complete abstract click electronic access below)
Mestre
Sánchez, Navarro Juan Manuel. "Síntesis y caracterización de materiales poliméricos para la separación no cromatográfica de metales nobles. Separación y determinación de iridio mediante cromatografía líquida y electroforesis capilar." Doctoral thesis, Universitat de Girona, 1999. http://hdl.handle.net/10803/96656.
Full textNuevos polímeros quelatantes con el mismo grupo funcional, basado en el sulfuro de tri-isobutilfosfina, han sido sintetizados para la separación selectiva de los Metales Nobles. Se han introducido diferentes espaciadores entre la matriz polimérica y los grupos funcionales, variando su longitud y el número de heteroátomos (O, S) presentes. Estos polímeros muestran una buena afinidad para los iones oro y plata, y una capacidad de adsorción inferior para los iones paladio, mientras que no adsorben al resto de Metales Nobles y metales base evaluados
Nous polímers quelatants amb el mateix grup funcional, basat en el sulfur de tri-isobutilfosfina, han estat sintetitzats per a la separació selectiva dels Metalls Nobles. S’han introduit diferents espaiadors entre la matriu polimèrica i els grups funcionals, variant la seva longitud i el nombre d’heteroàtoms (O, S) presents. Aquests polímers mostren una bona afinitat per als ions or i plata, i una capacitat d’adsorció inferior per als ions paladi, mentre que no adsorbeixen la resta de Metalls Nobles i metalls base avaluats
Asara, Gian Giacomo. "Transition metal carbides as active phase and as support in catalysis: Insights from first principles theoretical modelling." Doctoral thesis, Universitat Rovira i Virgili, 2014. http://hdl.handle.net/10803/454774.
Full textLos carburos de metales de transición (TMC) exhiben propiedades químicas y catalíticas similares a las de los costosos metales nobles. La conversión de alcohol, hidrogenación de olefinas y otras reacciones importantes han demostrado la aplicabilidad de estos compuestos en procesos industriales. También se sabe que nanopartículas de metales nobles (NMNPs) muestran una alta actividad catalítica a pesar de la baja o nula reactividad del metal sólido. Además, investigaciones recientes señalan que los soportes de TMC polarizan la densidad electrónica de NMNPs adsorbidos y aumentan la actividad catalítica respecto a los soportes más tradicionales de óxido metálico. Estos descubrimientos recientes han inspirado el trabajo presentado en esta tesis, realizado mediante técnicas actuales de la química cuántica. Se ha estudiado CO, CO2, H2, H2O adsorbidos sobre TiC y sobre pequeños clusters de oro adsorbidos sobre el suport. Se ha considerado la superficie (001), terrazas, escalones monoatómicos y defectos y, también, la reactividad de las moléculas adsorbidas sobre la superficie limpia de TiC (001) y en dos clusters de oro, Au4 y Au6, adsorbidos. Las barreras energéticas calculadas para la formación de metano o formaldehído a partir de gas de síntesis en la superficie limpia de TiC (001) resultan ser demasiado altas y esos procesos son inviables sobre el soporte limpio. Sobre los clusters de oro soportados sobre TiC (001) hay una mayor actividad catalítica, pero la reacción continúa siendo altamente impedida. Sin embargo la reacción de desplazamiento del gas de agua se prevé que sea rápida en el sistema Au4/TiC (001), superando los catalizadores utilizados normalmente en la industria. Experimentos recientes muestran que los clusters de Ni, Cu y Au están fuertemente deformados una vez adsorbidos sobre TMC dando lugar en catalizadores muy activos. Se ha investigado la interacción de los átomos con la fase delta del catalizador de MoC. La interacción es más fuerte para el recubrimiento más bajo considerado, la relajación de la superficie es importante y la actividad se prevé que aumente en el orden Ni> Cu> Au. Finalmente, se han considerado posibles reconstrucciones no polares para la superficie (001) de Mo2C centrándose en la energía de escisión, que es proporcional a la estabilidad de cada tipo de terminación. Las reconstrucciones no polares disminuyen la energía de escisión, confirmando la aplicabilidad de los conceptos clásicos de Tasker para óxidos a los TMC.
Carbides of the early transition metals (TMC) exhibit chemical and catalytic properties that in many aspects are very similar to those of expensive noble metals. Alcohol conversion, hydrogenation of olefins and many others important reactions demonstrated the applicability of these compounds for industrial processes. It is also known that small noble metal nanoparticles (NMNPs) show high catalytic activity despite of the poor reactivity or inertness of the bulk metal. Additionally, recent investigations pointed out that supporting TMCs polarize the electron density of adsorbed NMNPs increasing the catalytic activity respect to more traditional metal oxide supports. These recent discoveries inspired the work reported in this thesis using state-of-the-art quantum chemical techniques. We studied CO, CO2, H2, H2O molecules adsorbed on TiC and on small gold clusters adsorbed thereon. We considered the (001) extended surface, terraces, monatomic steps and kink defective sites. The reactivity of adsorbed molecules on the clean TiC (001) surface and on two gold clusters, Au4 and Au6, adsorbed thereon were also studied. Energy barriers calculated for methane or formaldehyde formation from syngas, on the clean TiC (001) surface were by far too high and those processes are unviable on the clean support. Gold clusters supported by TiC (001) show higher catalytic activity but the reaction continues to be highly hindered. However water gas shift reaction is predicted to be fast on the Au4/TiC(001) system, overtaking catalysts normally used in industry. Recent experiments show that Ni, Cu and Au clusters are strongly perturbed upon adsorption on TMC resulting in extremely active catalysts. We investigated the interaction of those atoms with the delta phase of the MoC catalyst. The interaction is stronger for the lowest coverage considered, the relaxation of the surface important and the activity is predicted to increase in the order Ni>Cu >Au. Finally, we have studied possible non-polar reconstructions of the (001) surface of Mo2C focusing on the cleavage energy, proportional to the stability of each type of termination. The non-polar reconstructions decreased the calculated cleavage energy, confirming the applicability of the classical Tasker’s concepts for oxides to TMCs.
Fowler, Rebecca M. "Identification of deformation mechanisms during bi-axial straining of superplastic AA5083 material." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://handle.dtic.mil/100.2/ADA432796.
Full textAKAY, NADIDE. "Responses of model plants to metals and non-metals : two case studies." Doctoral thesis, Università del Piemonte Orientale, 2015. http://hdl.handle.net/11579/81640.
Full textCockrell, Gregory Mercer. "The highly preorganized ligand 2, 9-DI-(2'-PYRIDYL)-1, 10-Phenanthroline, and its complexation properties with metal ions /." Electronic version (PDF), 2007. http://dl.uncw.edu/etd/2007-1/cockrellg/gregorycockrell.pdf.
Full textNunes, Silvia Irene. "Grain growth in sintered Zn0 ceramics /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/10594.
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