As high grade iron ore deposits are rapidly depleted, the minerals industry is increasingly obliged to enrich their ores and process lower grade iron ores. Production of large quantities of fine ores as tailings or by-products in mining operations and mineral liberation at fine particle sizes have led to the development of concentration methods employed to fine ores. Selective flocculation is one of the beneficial methods which can be used in recovering of very fine particles It is obvious that process water chemistry has a significant influence on the flocculation efficiency, and the water chemistry is deeply affected by carbon dioxide dissolution. Carbonate content of natural waters regulated by CO2, carbonicacid and solid carbonatesis known as &lsquo / carbonate alkalinity&rsquo / whichmay be an important factor in flocculation especially at alkaline pH. Selective flocculation of iron ores is usually run at around pH 11 where carbonate alkalinity could be rather high. There have been no reports in literature regarding the effect of carbonate alkalinity on the flocculation behavior of iron oxides, mainly hematite. In this study, the flocculation behavior of iron ores with starch under different alkalinities has been investigated. The extent of flocculation has been assessed by settling rate and suspended solid content measurements at different starch doses and pH values. Zeta potential measurements and starch adsorption studies were carried out to explain these effects by carbonate alkalinity. According to the results, flocculation is enhanced by addition of low amount of carbonate alkalinity, less than 2.4 mEq/L. However, adding the higher amount of alkalinity adversely affected the flocculation of hematite. Similar behavior was also observed during the starch adsorption tests, larger amount of starch wasadsorbed by hematite in low alkalinity compared to high alkalinity. Zeta potential measurements indicate that, by increasing the carbonate alkalinity of suspension, zeta potential values of solids will become more negativeleading to an increase in the stability of suspension and then adversely affecting flocculation. Therefore, as carbonate alkalinity has a significant effect on the flocculation of hematite, it should be seriously taken into account to optimize the selective flocculation of hematite ores.

No description available.

This thesis describes studies of materials which can be exploited for hydrogen production from water and sunlight. The materials investigated are maghemite (γ-Fe2O3), magnetite (Fe3O4) and especially hematite (α-Fe2O3), which is an iron oxide with most promising properties in this field. Hematite has been deposited using Atomic Layer Deposition (ALD) - a thin-film technique facilitating layer-by-layer growth with excellent thickness control and step coverage. The iron oxides were deposited using bis-cyclopentadienyl iron (Fe(Cp)2) or iron pentacarbonyl (Fe(CO)5) in combination with an O2 precursor. Since it is crucial to have good control of the deposition process, the influence of substrate, process temperature, precursor and carrier gas have been investigated systematically. By careful control of these deposition parameters, three polymorphs of iron oxide could be deposited: hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4). The deposited materials were characterized using X-ray Diffraction, Raman and UV-VIS Spectroscopy, and Scanning Electron Microscopy. Hard X-ray Photoelectron Spectroscopy (HAXPES) was also used, since it is a non-destructive, chemically specific, surface sensitive technique – the surface sensitivity resulting from the short mean escape depth of the photoelectrons. The depth probed can be controlled by varying the excitation energy; higher photoelectron energies increasing the inelastic mean-free-path in the material. HAXPES studies of atomic diffusion from F-doped SnO2 substrates showed increased doping levels of Sn, Si and F in the deposited films. Diffusion from the substrate was detected at annealing temperatures between 550 °C and 800 °C. Films annealed in air exhibited improved photocatalytic behavior; a photocurrent of 0.23 mA/cm2 was observed for those films, while the as-deposited hematite films showed no photo-activity whatsoever. The optical properties of low-dimensional hematite were studied in a series of ultra-thin films (thicknesses in the 2-70 nm range). The absorption maxima were shifted to higher energies for films thinner than 20 nm, revealing a different electronic structure in thin films.

abstract: The goal of the study was twofold: (i) to investigate the synthesis of hematite-impregnated granular activated carbon (Fe-GAC) by hydrolysis of Fe (III) and (ii) to assess the effectiveness of the fabricated media in removal of arsenic from water. Fe-GAC was synthesized by hydrolysis of Fe(III) salts under two Fe (III) initial dosages (0.5M and 2M) and two hydrolysis periods (24 hrs and 72 hrs). The iron content of the fabricated Fe-GAC media ranged from 0.9% to 4.4% Fe/g of the dry media. Pseudo-equilibrium batch test data at pH = 7.7±0.2 in 1mM NaHCO3 buffered ultrapure water and challenge groundwater representative of the Arizona Mexico border region were fitted to a Freundlich isotherm model. The findings suggested that the arsenic adsorption capacity of the metal (hydr)oxide modified GAC media is primarily controlled by the surface area of the media, while the metal content exhibited lesser effect. The adsorption capacity of the media in the model Mexican groundwater matrix was significantly lower for all adsorbent media. Continuous flow short bed adsorber tests (SBA) demonstrated that the adsorption capacity for arsenic in the challenge groundwater was reduced by a factor of 3 to 4 as a result of the mass transport effects. When compared on metal basis, the iron (hydr)oxide modified media performed comparably well as existing commercial media for treatment of arsenic. On dry mass basis, the fabricated media in this study removed less arsenic than their commercial counterparts because the metal content of the commercial media was significantly higher. / Dissertation/Thesis / M.S.Tech Applied Biological Sciences 2011

[pt] A busca por novos reagentes de baixa toxicidade e de alta biodegradabilidade tem sido estimulada. Como resultado, diversas pesquisas vêm desenvolvendo biorreagentes, dentre eles os biossurfactantes. Os biossurfactantes são moléculas de origem microbiana que possuem ação superficial. Essas moléculas, com propriedades anfifílicas, são produzidas biologicamente e têm aplicação em diversos setores industriais. Assim sendo, esta pesquisa teve como objetivo estudar a flotação do sistema hematita-quartzo utilizando o biossurfactante solúvel produzido por Rhodococcus erythropolis como biorreagente coletor. O biossurfactante (BS) foi caracterizado por análises químicas para determinar a percentagem de proteínas, carboidratos e lipídeos e, suas propriedades físico-químicas foram determinadas por tensão superficial e concentração micelar crítica (CMC). Os minerais e sua interação com o BS foram caracterizados por medições de potencial zeta, medidas de ângulo de contato e espectroscopia no infravermelho (FTIR) para determinar suas propriedades eletrocinéticas, hidrofobicidade e grupos funcionais, respectivamente. Os resultados de adsorção revelaram maior adsorção do biossurfactante na superfície de hematita do que na superfície de quartzo e, isto foi confirmado por analises FTIR e testes de microflotação. Os resultados de microflotação de hematita e de quartzo foram maiores em pH 3 e com concentração de BS de 100 mg/L, com recuperações em torno de 99,88 por cento e 31,05 por cento, respectivamente e, os mesmos foram analisados estatisticamente para obter uma função polinomial representativa da microflotação. Os testes de microflotação do sistema hematita-quartzo mostraram que o biossurfactante é mais seletivo com hematita do que quartzo. O estudo cinético mostrou que os dados experimentais da microflotação de hematita foram ajustados quanto ao modelo cinético de primeira ordem como ao modelo cinético de ordem fracionária, enquanto os dados experimentais da microflotação de quartzo foram ajustados ao modelo cinético de ordem fracionária. Finalmente, os resultados deste trabalho evidenciaram que a utilização do biossurfactante solúvel produzido por Rhodococcus erythropolis como reagente coletor no sistema hematita-quartzo foi viável, demonstrando o seu grande potencial e mostrando- se bastante promissor para uma futura aplicação na indústria da flotação mineral. / [en] The search for new reagents of low toxicity and high biodegradability has been stimulated. As a result, several researches have been developing bioreagents, among them biosurfactants. Biosurfactants are molecules of microbial origin that have surface action. These molecules, with amphiphilic properties, are produced biologically and have application in various industrial sectors. Therefore, this research aimed to study the flotation of the hematite- quartz system using the soluble biosurfactant produced by Rhodococcus erythropolis as a collector bioreagent. The biosurfactant (BS) was characterized by chemical analysis to determine the percentage of proteins, carbohydrates and lipids and its physicochemical properties were determined by surface tension and critical micellar concentration (CMC). The minerals and their interaction with BS were characterized by measurements of zeta potential, contact angle measurements and infrared spectroscopy (FTIR) to determine their electrokinetic properties, hydrophobicity and functional groups, respectively. The adsorption results revealed higher adsorption of the biosurfactant onto the hematite surface than onto quartz surface and this was confirmed by FTIR analysis and microflotation tests. The results of hematite and quartz microflotation were higher at pH 3 and at the concentration of 100 mg/L, with recoveries around 99.88 percent and 31.05 percent, respectively, and they were analyzed statistically to obtain a polynomial function representative of microflotation. The microflotation tests of the hematite-quartz system showed that the biosurfactant is more selective with hematite than quartz. The kinetic study showed that the experimental data of hematite microflocation were adjusted to both the first order kinetic model and the kinetic model of non-integral order, while the experimental data of the quartz microflotation were adjusted to the kinetic model of non-integral order. Finally, the results of this work showed that the use of the soluble biosurfactant produced by Rhodococcus erythropolis as a collector reagent in the hematite-quartz system was feasible, demonstrating its great potential and showing quite promising for a future application in the mineral flotation industry.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-06-02T22:41:13Z No. of bitstreams: 2 edilailsa_januario_melo.pdf: 2845467 bytes, checksum: 55f2a32335b696129bb30309f301b7ee (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-06-22T12:28:16Z (GMT) No. of bitstreams: 2 edilailsa_januario_melo.pdf: 2845467 bytes, checksum: 55f2a32335b696129bb30309f301b7ee (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-06-22T12:28:16Z (GMT). No. of bitstreams: 2 edilailsa_januario_melo.pdf: 2845467 bytes, checksum: 55f2a32335b696129bb30309f301b7ee (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O desenvolvimento de novos semicondutores fotocatalisadores, em particular os ativos na produ??o de hidrog?nio por fragmenta??o molecular da ?gua e da am?nia (presente no lixiviado de biodigestores ou de aterros sanit?rios e em efluentes industriais), tem dominado a ordem priorit?ria de interesse nas tecnologias avan?adas para a gera??o de energia limpa. Este trabalho teve como objetivo principal avaliar a produ??o fotocatalisada de hidrog?nio gasoso, a partir da fragmenta??o molecular da ?gua ou da am?nia, por uso da hematita pura ou da hematita dopada com os c?tions met?licos cobalto, n?quel, cobre e zinco como materiais semicondutores. Os materiais preparados por coprecipita??o foram caracterizados pelas t?cnicas de EDX, MEV, DRX, espectroscopia M?ssbauer, FTIR, BET e XPS. A taxa da produ??o de hidrog?nio foi avaliada por medidas de densidade da corrente gerada pelo H2(g) evolu?do da fragmenta??o molecular da ?gua ou da am?nia, em c?lula fotoeletroqu?mica (PEC). Foram tamb?m realizados testes fotocatal?ticos, sob luz vis?vel, com as hematitas, pura e com dopantes, como fotocatalisadores para degrada??o do corante ?ndigo de carmim, utilizado como mol?cula modelo, simulando a decomposi??o de substrato org?nico poluente em ?gua presente em efluentes industriais. Os resultados dos testes de degrada??o do corante mostraram que as hematitas dopadas com cobre e zinco tiveram relativamente alta atividade na degrada??o do corante; os melhores resultados foram obtidos com a hematita com zinco. Na evolu??o do hidrog?nio da fotocat?lise da ?gua, a dopagem com c?tions met?licos n?o alterou significativamente a atividade fotoeletroqu?mica da hematita. Ainda assim, a amostra de hematita dopada com n?quel foi a que apresentou um discreto aumento da densidade de corrente, maior propor??o de hidrog?nio gasoso produzido, sob radia??o com comprimento de onda maior do que 450 nm. A densidade de corrente gerada da degrada??o da am?nia foi maior, se comparada ? fragmenta??o da ?gua. No entanto, a dopagem tamb?m n?o alterou de forma significativa a atividade PEC dos materiais. Das amostras de hematitas dopadas, a com cobre foi a que apresentou os melhores resultados fotoeletroqu?micos, ainda que abaixo da efici?ncia fotoeletroqu?mica da hematita pura. / Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / Technological developments of semiconductors to be used as photocatalysts for hydrogen production and for the degradation of organic pollutants in water in different circumstances, such as ammonia sluggishness from biodigesters and organic residues from industrial effluents, are strongly challenging the interest of the scientific community. The main objective of this work was to evaluate the molecular hydrogen production from the molecular fragmentation of water and ammonia using pure hematite and cobalt, nickel copper and zinc dopant prepared as co-precipitators as semiconductor materials. The materials prepared were characterized by EDX, MEV, XRD, M?ssbauer, FTIR, BET and XPS spectroscopy. The evaluation of the hydrogen production was carried out through measurements of current densities generated by the decomposition of water and ammonia in a photoelectrochemical cell (PEC). Photocatalytic tests were also carried out under visible light using pure hematite and with dopants as photocatalysts for the degradation of carmine indigo dye used as a model molecule. The results of the dye degradation tests showed that copper and zinc doped hematite increased dye degradation, and the best results were obtained for zinc hematite. In the evolution of hydrogen from water, the doping with metallic cations did not significantly alter photoelectrochemical activity of hematite, the hematite with nickel was the sample that presented a small increase in current density when in the presence of light. The current density generated by the ammonia degradation and consequent hydrogen production was higher when compared to water, however, doping also did not significantly alter the PEC activity of the materials, comparing the materials, the hematite with copper was the sample that presented the best results.

Cette thèse s’inscrit dans le projet ASCoPE qui vise à développer les connaissances scientifiques et technologiques nécessaires à la conception et à la réalisation d’un pilote de production d’acier par réduction électrochimique de particules d’hématite en suspension dans un milieu alcalin à 110°C, en vue de proposer un procédé industriel fiable et écologique, comme alternative au procédé classique reposant sur le charbon. Le mélange considéré contient une suspension d’hématite à 12% en volume dans une solution aqueuse de soude à 50% en masse. Cette thèse a pour objectif l’étude de la sédimentation et de la rhéologie des suspensions d’hématite et le comportement hydrodynamique des particules d’hématite dans une cellule inclinée et de quantifier l’éventuel phénomène d’impact sur la cathode / This thesis aims to develop scientific and technological knowledge needed to design a pilot production of steel by electrochemical reduction of hematite particles suspended in an alkaline medium at 110°C in order to provide a reliable and environmentally friendly industrial process, as an alternative to the conventional process based on coal. The mixture considered contains a suspension of hematite of 12% by volume in an aqueous sodium hydroxide solution of 50% by weight. This thesis seeks to study the sedimentation and rheology of hematite suspensions and the hydrodynamic behavior of hematite particles in inclined cell and to quantify the possible phenomeno impact on the cathode

O caulim do Rio Capim na Amazônia Oriental se constitui num depósito importante para o Brasil, ocupando lugar de destaque na produção mundial desta matéria prima mineral. Os modelos estabelecem uma origem para a caulinita vinculada ao intemperismo em condições lateríticas (Paleogeno Inferior) a partir de um substrato formado por rochas sedimentares da Formação Ipixuna (Cretáceo Superior). No perfil, destacam-se em ordem de importância entre os compostos de ferro, a hematita e a goethita, minerais pouco estudados no caulim do Rio Capim. A partir dos fácies principais do caulim (fácies caulim macio na base e caulim duro no topo), foram separados e concentrados os minerais de interesse para estudos de detalhe, utilizando a difratometria de raios X (DRX) e a espectrometria de infravermelho por transformada de Fourier (FTIR). Entre os parâmetros determinados, obtiveram-se estimativas da dimensão, forma, área superficial e substituição isomórfica. A interpretação dos resultados evidencia o potencial de aplicação das informações na estimativa do comportamento destes minerais durante o processo de beneficiamento e para a discussão do modelo genético dos perfis de caulim. As goethitas e hematitas de ambos os fácies possuem propriedades muito semelhantes, reforçando o modelo que especula sobre uma origem comum para a fácies caulim macio e caulim duro do perfil. Entre as propriedades, destacam-se a elevada cristalinidade e a baixa participação do alumínio em sua composição, proporcionando a estes minerais um comportamento com resistência moderada a elevada nos processos de lixiviação ácida e a tendência de dissolução preferencial da hematita. O conjunto de características dos óxidos e oxihidróxidos de ferro são compatíveis com uma formação em ambientes hidromórficos, com baixa influência da matéria orgânica a partir de soluções com baixa atividade do ferro, moderadamente redutoras a fracamente ácidas. Dentro do modelo genético da formação do caulim, sua origem não está associada à zona de laterização do perfil, sendo compatível com um ambiente saprolítico e hidromórfico. As propriedades observadas permitem afirmar que os processos naturais que favoreceram a formação da caulinita na base do manto de alteração foram suficientemente longos e intensos para promover a retirada do ferro destas fácies num processo não dissociado no tempo. No modelo, o caulim é uma fácies da base do perfil formado abaixo do nível freático de um espesso perfil laterítico em condições moderadamente redutoras e ácidas com elevada atividade do Si e do Al, porém, com carência de Al disponível para a formação da hematita e da goethita. Neste ambiente, haveria uma lenta mobilização do Fe dentro do perfil sem a necessidade do estabelecimento de um evento excepcional com uma elevada atividade da matéria orgânica, como previsto em alguns modelos. / The Rio Capim Kaolin from the eastern Amazon is recognized as one of the largest deposits of Brazil with a quality and volume that place this area amongst the most important deposits in the world. Despite the importance and the significant amount of studies about kaolin, many questions remain unanswered and the genesis of this occurrence is not well understood. Perhaps, the consensus today is the acceptance of the Rio Capim kaolin origin to be related to a lateritic weathering process during the Early Paleogene, period with favorable geotectonic, duration and climatic conditions to originate a thick cover with the development of a complete weathering profile above a substrate composed by sedimentary rocks of the Ipixuna Formation (Cretaceous). The models consider kaolin to be a bottom facies of a thick lateritic profile, but nowadays the upper lateritic facies was destroyed (probably by erosion periods along the middle to upper Paleogene). The kaolin profile has two facies: the bottom one, which is called soft kaolin, and the upper, differentiated one forming the flint kaolin. Most controversial points are related to the way that the flint kaolin was formed and the mechanism in which the iron was mobilized from the kaolin profile as a whole. This study aims to get some insight about the Rio Capim kaolin development using some properties measured from the iron oxides and oxyhydroxides. The iron and titanium minerals from the kaolin represent the most important contaminants, and a large effort is made by the industry to eliminate their influence but, despite this negative reputation, those minerals also represent a source of valuable information about the environmental conditions of the profile. Among them, hematite is the most widespread in the entire kaolin profile, followed by goethite, whose importance increases in the direction of the flint kaolin facies. Representative samples of kaolin facies were selected from the kaolin profile and submitted to an approach that allowed concentrating the iron minerals and eliminating the influence of kaolinite. Using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR), a set of properties of the hematite and goethite were determined, including median crystal dimensions, shapes, specific surface area and mineral composition by estimating the isomorphous replacement of iron (Fe) by aluminum (Al). The results show that hematites and goethites do not have enough differences in their properties to support a genesis model with radical changes in their conditions . In terms of behavior to acid leaching, the observed variations were important to predict differences in the rate of mineral dissolution and possibilities of preferential dissolution of hematite in relation to goethite, promoting the increase of the yellow component with the leaching. Both hematite and goethite have high crystallinity and the isomorphous replacement of Fe by Al is low. Comparing the properties observed in synthetic and natural environments, the hematite and goethite from the Rio Capim kaolin profile have characteristics that relate these minerals to a formation environment in hydromorphic conditions where the influence of organic matter was low, with low iron activity, weakly reduced and acidic conditions. These conditions are found in a saprolitic domain in accordance with the bottom facies of a thick laterite profile. Despite agreeing with a laterite model, differences make it difficult to explain iron depletion by organic matter only (Pirabas Event) and the origin of flint kaolin facies by a subsequent and superimposed laterite period. With the hematite and goethite properties found in this study, it is possible to propose that the Rio Capim kaolin is the bottom facies of a laterite profile formed in the zone permanently below the water table. Contrasting with the upper laterite portion of the profile, the bottom zone is in hydromorphic conditions and allowed the fixation of Al and Si to form kaolinite by primary feldspar and mica minerals of the Ipixuna Formation. This environment promotes the slow depletion of iron without the need of an exceptional accumulation of organic matter. The flint kaolin facies was formed in the same period of the soft kaolin facies and the observed differences in the kaolinite morphology are only related to changes caused by the location of this facies in the intermediate zone characterized by the water table fluctuation, but again without the need of subsequent superimposed lateritic processes.

Un procédé simple, compact et continu a été utilisé pour élaborer des particules nanométriques d’oxyde de fer. Il est constitué principalement de deux étapes : une première étape de génération du solide en réacteur à lit fluidisé, une deuxième étape de calcination couplée à un filtre à manches métalliques qui permet de récupérer des particules nanométriques d’oxyde de fer. Différentes analyses ont permis de caractériser les particules obtenues à chacune des deux étapes. Le produit obtenu au cours de l’étape de génération du solide est de la ferrihydrite sous forme de particules micrométriques constituées d’agglomérats de particules nanométriques. L’étape de calcination conduit à la formation de particules nanométriques d’hématite. Elles ont une taille médiane inférieure au µm et présentent une distribution de taille resserrée, ce qui est difficilement atteignable par les procédés conventionnels. Les particules sont constituées d’agglomérats de grains élémentaires de quelques dizaines de nanomètres. Leur surface spécifique BET et leur masse volumique réelle sont comparables à celles mesurées sur un produit commercial. L’étude de l’influence des conditions opératoires du procédé a permis de définir les paramètres optimaux à fixer pour obtenir une hématite pure et peu agglomérée. L’étude du mécanisme réactionnel, réalisée en thermobalance, dans un four à moufle et à l’aide d’une veine de séchage a montré que la décomposition de la solution de nitrate de fer nonahydraté en hématite se déroule en trois phases : une première phase accompagnée d’une perte de l’eau libre et de sept molécules d’eau de constitution, une deuxième phase rapide accompagnée d’une perte des molécules de nitrate jusqu’à l’obtention de la ferrihydrite, une troisième phase lente accompagnée d’une perte de nitrate et d’eau restants jusqu’à l’obtention d’hématite amorphe qui est ensuite cristallisée à haute température. Les deux premières phases ont lieu dans le réacteur à lit fluidisé, alors que la troisième se déroule dans le réacteur de calcination. Une étude cinétique de cette dernière phase a été réalisée en thermobalance. Elle a démontré que l’énergie d’activation est faible et que le processus est complexe. / A simple, compact and continuous process was used to synthesize iron oxide nanoparticles. This process is divided in two parts: dry particles generation and calcination. Different analytical techniques have permitted to characterize the produced particles.The obtained product at the dry particles generation step is ferrihydrite. The particles are constituted of agglomerated nanoparticles. The calcination step allows producing hematite nanoparticles. These ones have a median size less than a micron and a narrow particle size distribution, which is difficult to achieve using conventional methods. These particles are constituted of agglomerated elementary particles which have a size of a few tens of nanometers. The specific surface area and the density of the produced hematite in the process are comparable to those measured on a commercial product. The influence of process conditions was also investigated and the results were analysed to define the optimal operating conditions to produce pure hematite slightly agglomerated. The study of the reaction mechanism, performed in a thermobalance, an oven and a convective dryer showed that the solution of iron nitrate nonahydrate decomposes into hematite according to three steps: removal of free water and seven molecules of constitution water, rapid loss of nitrate molecules until ferrihydrite is formed, removal of remaining nitrate and water leading to the formation of amorphous hematite which is then crystallized at high temperature. The two first steps take place in the fluidized bed reactor, while the third one is performed in the calcination reactor. A kinetic study of the last transformation was performed in a thermobalance. This study showed that the activation energy is low and the reaction is complex.

Orientador: Prof. Dr. Flavio Leandro de Souza / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016. / Com a crescente demanda energética mundial e a necessidade de desenvolvimento nos métodos renováveis para obtenção de energia surge o interesse nas Células Fotoeletroquímicas, dispositivos que possibilitam a conversão da energia da radiação solar em energia química na forma de hidrogênio molecular. Grande parte da pesquisa na área das células fotoeletroquímicas é voltada para a eficiência de conversão energética e barateamento de custos de produção. Com base nisso o presente trabalho tem foco no desenvolvimento de eletrodos usados nesse dispositivo, sintetizados usando hematita em condição hidrotermal, buscando a melhoria dos métodos de síntese para redução de custos, impacto ambiental e eficiência energética. A síntese utilizada teve o intuito de reduzir ao máximo a quantidade de reagentes à base de cloro, que podem interferir negativamente no crescimento das estruturas e analisar a influência de alguns parâmetros alterados durante o processo: tempo de síntese, atmosfera de tratamento térmico e concentração de reagentes. Foi concluído, com base nas caracterizações morfológicas e eletroquímicas aplicadas nas amostras, que a síntese hidrotermal utilizada gerou eletrodos fotossensíveis sendo mais efetiva nos tempos de 1 hora, com tratamento térmico em atmosfera de nitrogênio e com uso de 0,076 mol.L-1 de sulfato de sódio e 0,15 mol.L-1 de cloreto de ferro, contribuindo com a redução da quantidade de cloro utilizado. A melhor fotocorrente obtida para os eletrodos foi por meio da amostra F1Ny chegando a 0,936 mA.cm-2. / The increase of global energy demand and the need for renewable sources results on the interest in devices know as photoelectrochemical cells. This device enables the conversion of solar radiation energy into chemical energy in the form of molecular hydrogen. Most of the research in the area of the photoelectrochemical cells is focused on the energy conversion efficiency and reduction of production costs. This work aimed the development of electrodes used in photoelectrochemical cells, synthesized using hematite in hydrothermal condition, seeking the improvement of synthesis methods to reduce costs, environmental impact and energy efficiency. The synthesis used was intended to reduce the amount of chlorine based reagents that can negatively impact the growth of structures and analyze the influence of some parameters changes during the process: synthesis time, atmosphere used in the heat treatment and reagents concentration. It was concluded through morphological and electrochemical characterization that the hydrothermal synthesis has generated photosensitive electrodes. The most promising electrode produced was synthesized for 1 hour, them treated in nitrogen atmosphere and using 0.076 mol.L-1 of sulfate sodium and 0.15 mol.L-1 of iron chloride, contributing to reduce the amount of chlorine used in relation to other methods generally discussed in the literature. The best photocurrent obtained was 0.936 mA.cm-2.