La bauxite est un minerai utilisé pour l’élaboration de l’aluminium ou en tant que matière première pour les ciments techniques. Elle est employée, sous sa forme naturelle, en blocs. Ces blocs se font de nos jours de plus en plus rares et leur manutention peut entraîner des pertes sous formes de poussières non valorisées. L’objectif de ce projet est de recycler ces fines particules minérales sous forme de compactés afin d’améliorer l’usage des ressources naturelles minérales qui se raréfient. Ces compactés sont obtenus par compression directe puis avec un procédé innovant couplant vibration et compression. La poudre de bauxite est mélangée à du ciment et de l’eau, puis subit une phase de compaction. Ces compactés doivent avoir des propriétés spécifiques en termes de masse volumique, porosité et résistance mécanique. La micro-tomographie à rayons X est utilisée pour décrire le réarrangement granulaire et l’homogénéité 3D des porosités. La distribution poreuse est caractérisée par analyse d’image et comparée avec les résultats de porosimétrie mercure. Cette étude concernant l’évolution des paramètres texturaux des compactés amène une compréhension des phénomènes liés à la phase de compression. Le stockage et la maturation de ces compactés sous température et humidité contrôlées ont également été étudiés. L’optimisation des paramètres de compression et de formulation, comme la quantité d’eau ou de ciment dans le mélange et la pression de compression, a mené à l’amélioration des propriétés des compactés. Dans un second temps, la phase de compression et les propriétés des compactés ont été améliorées en utilisant une phase préliminaire de vibrations. Cette phase a été optimisée grâce à l’étude de plusieurs paramètres spécifiques comme le type, l’amplitude et la fréquence des vibrations. / The bauxite is used in aluminium elaboration or directly as a raw material for calcium aluminates in technical cements. It is used, as a raw material, as blocks. Recently bauxite blocks are rarer and rarer and their handling can lead to dust wastes that are not re-used. The objective of this project is to recycle the fine mineral particles in compacts to improve the use of natural mineral resources that are running out. These products are compacted by direct compaction and also with an innovative vibration and compaction process. The bauxite is mixed with cement and water, and then the mixture is compacted. They must have specific properties with higher density and mechanical resistance. X-Rays micro-tomography is used to describe the particle rearrangement and the 3D density homogeneity. The porous distribution is then characterized by image analysis and compared with the mercury intrusion porosimetry results. This study on textural parameters evolution of the compacts leads to improve an understanding about the phenomenon during the compaction stage. The storage with controlled temperature and humidity will also be studied. The optimization of the compression and mixture parameters, as amount of water or cement in the mixture and compression pressure, led us to get compacts with improved properties. In the final study, we improved the compression stage and the compacts properties by another stage using in-situ vibrations. The vibrations stage has been optimized studying several vibrational parameters especially the type, the duration, the amplitude and the frequency of the vibrations.

To live a healthy life, people all around the world need access to safe water. A lot of industries,together with the fast growing population in Blantyre, a city in southern Malawi, pose a threat to theaccess of safe water for the citizens. Several of the industries in Blantyre release contaminated waterto the nearby streams. One serious pollutant emitted from a match factory is chromium (Cr),especially in the occurrence of Cr(VI) which is carcinogenic for humans. Earlier studies have shownthat the concentration of chromium in the match factory’s wastewater was higher than WHO:sguidelines. It has also been published that natural clay minerals can be used for adsorption of Cr(III).This study investigates the removal of Cr(VI) through the adsorption of Cr(VI) to clay minerals or byreduction of Cr(VI) to Cr(III) which is precipitated from solution.The laboratory work performed in this study includes both experiments for adsorption of Cr(VI) andreduction of Cr(VI) to Cr(III). The reducing agents investigated were two clays and Fe(II) sulfate. Foradsorption of negatively charged Cr(VI) compounds, the two clays where used at lower pH and themineral bauxite was also tried as adsorbent agent. Wastewater from the match factory was dilutedand mixed with the removal agents and the concentration of total chromium was measured beforeand after the mixing process. For the agent with highest potential for Cr(VI) removal, the optimalconditions due to pH, dosage of agents and contact time were inspected.None of the investigated reducing agents served its purpose which means that no Cr(VI) was reducedto Cr(III) in this study. The adsorption of Cr(VI) with clay 1 at lower pH was also not successful, butthe adsorption worked for clay 2 at lower pH and for bauxite. In the experiments bauxite adsorbed ahigher amount of Cr(VI) than clay 2. The adsorption with bauxite turned out to be independent interms of pH. The optimal conditions for bauxite in the experiments were with a dosage of 3.5 gbauxite in 50 mL wastewater and a contact time of 40 minutes. The results showed an adsorption of93 percent of total chromium with bauxite at optimal conditions.

Cretaceous bauxite deposits from Hall and Veneer mines, Wilkinson County, Georgia are composed of kaolinite, gibbsite, goethite, anatase, nordstrandite and bohemite. Quartz and micas are absent in the samples. The presence of boehmite and goethite are evidence of intense weathering forming the bauxite deposits. The extremely high values of the Chemical Index of Alteration (CIA) which is over 99, and the low values of the alkali metals and alkali earth metals, support an intense weathering origin for the bauxite deposit. There is evidence of deposition in the mines based on the presence of pisoids in the bauxite samples and the composition of the parent materials, which vary markedly by the non-uniform TiO2/Al2O3 values which represent the accumulation of transported materials from contrasting source areas. Kaolin minerals were first produced by the hydrolytic weathering of aluminous sediments and then gibbsite was formed as early kaolin was desilicated.

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Cretaceous bauxite deposits from Hall and Veneer mines, Wilkinson County, Georgia are composed of kaolinite, gibbsite, goethite, anatase, nordstrandite and bohemite. Quartz and micas are absent in the samples. The presence of boehmite and goethite are evidence of intense weathering forming the bauxite deposits. The extremely high values of the Chemical Index of Alteration (CIA) which is over 99, and the low values of the alkali metals and alkali earth metals, support an intense weathering origin for the bauxite deposit. There is evidence of deposition in the mines based on the presence of pisoids in the bauxite samples and the composition of the parent materials, which vary markedly by the non-uniform TiO2/Al2O3 values which represent the accumulation of transported materials from contrasting source areas. Kaolin minerals were first produced by the hydrolytic weathering of aluminous sediments and then gibbsite was formed as early kaolin was desilicated.

This thesis is made as it is submitted as a sum of published papers by the candidate. Aluminium hydroxides including gibbsite, boehmite and diaspore, are the major components, while iron hydroxides/oxides and kaolinite are the major impurities in bauxite. The dehydroxylation pathways during thermal activation of bauxite have been debated for decades. Phase transformation during thermal activation or calcination of bauxite to achieve high yields of alumina has been an important goal for the refining industry. This study deals with natural and synthetic aluminium and iron hydroxides using vibrational spectroscopy in conjunction with X-ray diffraction and electron microscopy, followed by the characterisation of the phase transformation in activated bauxite. In the Raman spectra, gibbsite shows four bands at 3617, 3522, 3433 and 3364 cm-1, and bayerite shows seven bands at 3664, 3652, 3552, 3542, 3450, 3438 and 3420 cm-1 in the hydroxyl stretching region. Five bands at 3445, 3363, 3226, 3119 and 2936 cm-1 for diaspore and four at 3371, 3220, 3085 and 2989 cm-1 for boehmite are present. The far infrared spectrum of boehmite resembles that of diaspore in the 300-400 cm-1 region. Boehmite has two characteristic bands at 366 and 323 cm-1 while diaspore has five at 354, 331, 250, 199 and 158 cm-1. The far infrared spectrum of gibbsite resembles that of bayerite in the 230-300 cm-1 region. Gibbsite shows three characteristic bands at 371, 279 and 246 cm-1 whereas bayerite shows six at 383, 345, 326, 296, 252 and 62 cm-1. The far infrared spectra are in-harmony with the FT-Raman spectra, allowing the study and differentiation of the stretching of AlO4 units to characterize these four alumina phases. The surface properties of kaolinite and gibbsite are studied using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). The FTIR-PAS spectra of kaolinite are recorded at mirror velocities of 0.05, 0.1, and 0.2 cm s-1, and compared to the gibbsite spectra recorded at mirror velocity of 0.2 cm s-1. It is found that the hydroxyl surface spectra are a function of depth. For the FTIR spectroscopy of thermal dehydroxylation of goethite to form hematite, the intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite, in particular the migration of excess hydroxyl units from goethite to hematite. Data from the band component analysis of FT-IR spectra indicate that the hydroxyl units mainly affect the a- plane in goethite and the equivalent c- plane in hematite. A larger amount of non-stoichiometric hydroxyl unit is found to be associated with a higher aluminium substitution. A shift to a higher wavenumber of bending and hydroxyl stretching vibrations is attributed to the effects of aluminium substitution associated with non-stoichiometric hydroxyl units on the a-b plane relative to the b-c plane of goethite. The dehydroxylation pathways of both the aluminium hydroxides and the impurities are intensively studied. Gibbsite completely decomposed at 250 °C, followed by boehmite and kaolinite at 500 °C. No phase transformations were observed for hematite, anatase, rutile or quartz up to 800 °C. Small amounts of gibbsite transformed to boehmite but the majority transformed to chi (χ) alumina, a disordered transition alumina phase, after dehydroxylation at 250 °C. The dehydroxylation pathways of crystalline gibbsite follow the orders: (a) gibbsite (&lt250 °C) to boehmite (250-450 °C) to gamma alumina (γ) (500-800 °C); or (b) gibbsite (&lt250 °C) to chi alumina (χ) (250-800 °C) to chi (χ) + kappa alumina (κ) (700-800 °C). Boehmite completely altered to gamma alumina (γ), while kaolinite altered to metakaolinite at 500 °C. The vibrational spectroscopy including FT-IR and FT-Raman, is a rapid, accurate and non-destructive technique in characterising both single and mixed mineral phases. In particular, the vibrational spectroscopy has shown its advantages over other techniques in terms of its sensitivity to hydroxyl groups. Future work on the simulation of bauxite dehydroxylation with emphasis on the studies of transition aluminas is proposed. The application of the advanced technique synchrotron x-ray spectroscopy, in addition to those techniques used in the present study, is recommended.

Orientador: Daniel Barrera-Arellano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-24T21:24:42Z (GMT). No. of bitstreams: 1 Richter_Willian_M.pdf: 5201143 bytes, checksum: 5a032b0c7ff61300137eb551c7dc1a60 (MD5) Previous issue date: 2014 / Resumo: A crescente preocupação com o meio ambiente ao longo dos anos é notória. Aspectos relevantes são a destinação de subprodutos e a emissão de gases e partículas para a atmosfera. Com a aprovação da lei n°. 11.097 de janeiro de 2005, o Brasil passou a inserção de biodiesel como substituto de diesel derivado de petróleo, que é menos poluente que os combustíveis fósseis. Porém, o acréscimo de biodiesel acarreta alguns problemas que não ocorrem com o uso de diesel puro. Destacam-se entre esses problemas os resíduos de reação e a deposição de compostos naturais, formados ou incorporados ao longo da sua cadeia de produção e distribuição. Assim o emprego de adsorvedores alternativos, como a bauxita ativada, para a remoção destes compostos tanto em biodiesel puro (B100) ou nas blendas torna-se uma opção rápida e de fácil implementação, uma vez que a sua instalação poderá ser feita no final da cadeia, nos postos de distribuição. Deste modo, o objetivo deste trabalho foi estudar um processo alternativo de purificação de biodiesel B5 sob uma coluna de bauxita ativada em processo laboratorial e piloto. O estudo empregou técnicas analíticas descritas e aprovadas pela Agência Nacional do Petróleo, Biocombustíveis e Gás Natural. Obtiveram-se também as curvas de rupturas no tratamento laboratorial para avaliar a eficiência do processo. As respostas obtidas para a determinação de contaminantes totais durante os processos mostraram uma diminuição similar nos processos laboratoriais e piloto, onde foi observada uma redução acima de 50% na escala piloto após o vigésimo primeiro dia de tratamento. Para a determinação de água foi observado uma redução de aproximadamente 90% no teste laboratorial e uma pequena redução nos primeiros dias no tratamento piloto. Os atributos de viscosidades dinâmica, cinemática e massa específica não se alteraram para ambos os processos, permanecendo dentro do estipulado pela legislação. No processo laboratorial foi observada uma redução na acidez, enquanto que na escala piloto este atributo permaneceu inalterado. Contudo, pode-se concluir com o estudo realizado que há possibilidade de utilização da bauxita ativada como agente purificador de blenda de biodiesel B5 / Abstract: The growing concern for the environment over past years is notorious. Pinpoints are the allocation of by-products and the emissions of gases and particles into the atmosphere. With the approval of the law n °.11.097 from January 2005, Brazil introduced biodiesel as a substitute for petroleum products which is less polluting than fossil fuels. However, the usage of biodiesel entails some problems that do not occur with pure diesel. Prominent among these problems are the residues of reaction and the deposition of natural compounds, formed or incorporated throughout its chain of production and distribution. Thus, the use of alternative adsorbents such as activated bauxite for removing these compounds in pure biofuels (B100) or their mixtures, biodiesel B5, becomes a quick and easy to implement solution, since its installment can be made at the end of the chain at the distribution depots. Hence, the aim of this study was to investigate an alternative method of purifying biodiesel B5 in a column of activated bauxite in laboratory and pilot process. The study employed analytical techniques described and approved by the National Agency of Petroleum, Natural Gas and Biofuels. Disruption curves in laboratory processing were obtained to assess the efficiency of the process. The data obtained for total contaminants during the process showed a similar decrease in both pilot and laboratory processes where a decrease of over 50% was observed in the pilot scale after the twenty-first day of treatment. For the determination of water, a reduction of approximately 90% in the laboratory test and a small decrease in the first days of pilot treatment, were observed. The attributes of dynamic viscosity, kinematic and density were unaltered for both processes, remaining within legislation. In the laboratory process a reduction in the acidity was observed, while in the pilot it remained unchanged. In conclusion, the study reveals that the use of activated bauxite as a purification agent for B5 biodiesel blend is an optimal possibility / Mestrado / Tecnologia de Alimentos / Mestre em Tecnologia de Alimentos

Pacific Northwest ferruginous bauxite deposits have formed in four main areas of northwestern Oregon and southwestern Washington by laterization of flows of the Columbia River Basalt Group (CRBG). The deposits, averaging 36.3% Al2O3 , 31.8% Fe2O3 , and 5.9% Sio2, generally occur near the surface of hilltops in gently rolling areas. Two very different views have been advanced regarding the setting in which the deposits have formed. The first hypothesis calls for a blanket-type laterization by erosion of much of the original deposit upon uplift and dissection of the area.

Wet chemical analysis and instrumental neutron activation analysis (INAA) were performed on a suite of samples from three residual ferruginous bauxite profiles in the study area for abundances of Al2O3, SiO2, Fe2O3, Ti O2, Na, Sc, Hf, Cr, Co, La, Sm, Yb, Lu, and Th. In addition a mineralogical study accompanied this research, using petrographic, differential thermal, and x-ray diffraction techniques. In each profile, the relative mobility of these elements were calculated by empirical methods for comparison with the parent rock and mineral properties in the saprolite. This study indicates that the first original constituent of the basalt to decompose under the influence of weathering is interstitial glass. The second phase results in the decomposition of plagioclase and pyroxene. Plagioclase alters mainly to kaolinite and metahalloysite. Pyroxene and basaltic glass alters mainly to nontronite, hematite, limonite, and amorphous clay. Opaques remain nearly unaltered. The low grade ferruginous bauxite ore is not derived solely from basalt, but also forms by weathering of younger sedimentary strata that overlie the basalt flows of the Columbia River Group. In general, components that are progressively depleted under the influence of weathering are Si02, Na, La, Sm, and Lu; these losses result in greater concentration of AlO3, Fe2O3, TiO2, Sc, Cr, Th, and Hf. Cobalt behaves erratically. There seems to be no predictable relationship between the ratios of rare earth elements in ferruginous bauxite and the parent rock. In the most weathered zone, Fe2O3, TiO2, Al2O3, Sc, Hi, Cr, and Th are enriched. Na, SiO2, Sm, and Lu are depleted relative to the parent rock. Trace elements associated with iron-rich pisolites are Lu, Yb, Th, and Co. Only Th is associated with gibbsite.