Ammonia and water are major components of many planetary bodies, from comets and icy moons such as Saturn's Titan to the interiors of the planets Neptune and Uranus. Under a range of high pressures and/or low temperatures known to occur in these planetary bodies, ammonia and water form a series of compounds known as ammonia hydrates. Ammonia and water form three stoichiometric compounds, ammonia hemihydrate, ammonia monohydrate and ammonia dihydrate, which have ammonia-to-water ratios of 2:1, 1:1 and 1:2 respectively. Therefore a good understanding of the three stable ammonia hydrates is required for modelling the interiors of these bodies. Additionally, the ammonia hydrates are the simplest systems to incorporate mixed (N-H O and O-H N) hydrogen bonds. Such bonds are important biochemically, and along with O-H O H-bonds, mixed H-bonds are responsible for the second-order structure of DNA, and they are also responsible for the proton transfer reactions in enzymic processes. The understanding of these bonds and processes rests on the knowledge of the relationship between bond strength and geometry, and the ammonia hydrates provide a rich range of geometries against which models of such mixed H-bonds can be tested. X-ray and neutron diffraction techniques have been used to investigate the behaviour of the ammonia-water complex and further the understanding of this system. This includes solving the structure of a phase which was previously thought to be an ammonia monohydrate phase, but has been shown here to be a mixture of an ammonia hemihydrate phase and Ice VII. In addition to this, x-ray and neutron diffraction experiments have been performed to explore how this phase behaves under changing pressure and temperature conditions, and what other implications that this has on the ammonia-water system. It has been found that ammonia hemihydrate can also form a structural phase observed to form in both ammonia monohydrate and ammonia dihydrate within the same pressure and temperature regime, which opens the possibility of a solid solution existing between all three stoichiometric ammonia hydrates.

Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2018-06-22T19:42:32Z No. of bitstreams: 2 Dissertação - Thiago Lopes dos Santos - 2016 .pdf: 4251376 bytes, checksum: 76ce02aadab49051cfb47e627123aecc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-06-27T11:16:18Z (GMT) No. of bitstreams: 2 Dissertação - Thiago Lopes dos Santos - 2016 .pdf: 4251376 bytes, checksum: 76ce02aadab49051cfb47e627123aecc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-06-27T11:16:18Z (GMT). No. of bitstreams: 2 Dissertação - Thiago Lopes dos Santos - 2016 .pdf: 4251376 bytes, checksum: 76ce02aadab49051cfb47e627123aecc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The phosphogypsum is generated from the production of the phosphogypsum acid in the fertilizer industry and phosphate fertilizers. Studies show that phosphogypsum can be applied in areas such as civil construction, the cement industry and agricultural sector. However this is used in low quantities. In pavements construction, is the phosphogypsum can be used and many studies have been taken at the Universidade Federal de Goias (UFG). In this context, the objective of this work was to study the hemihydrate gypsum (HH) in mixtures with soil, cement and lime, in order to facilitate and expand its use in paving. The heat treatment of dehydrate gypsum (DH) was carried out in the Goias state, thus obtaining the phosphogypsum (HH). Three mixtures were studied: Mixture S+HH (50% soil, 50% phosphogypsum HH); Mixture S+HH+CIM (50% soil, 41% phosphogypsum HH and 9% cement) and Mixture S+HH+CAL (50% soil, 44% phosphogypsum HH and 6% lime). Characterisation tests were conducted (utilising traditional methodology and the MCT methodology) and mechanical strength tests (unconfined compressive strength – UCS and resilient modulus – RM) to obtain parameters for use in paving. Deformability tests were also carried out, through consolidation tests, to evaluate the stabilisation of deformation of phosphogypsum HH over time, and stability when subjected to a load in the saturated and unsaturated conditions. In was studied the effect of bad weather conditions on the samples through resistance tests to the simple compression in samples exposed to the elements for up to 180 days. Scanning electron microscopy tests (SEM) were performed to understand the micro structural behaviour. In the samples that contained phosphogypsum HH there was greater UCS than the samples that contained only soil and mixtures with the same phosphogypsum DH proportions. The mixture S+HH+CIM obtained greater resistance and the mixtures S+HH+CAL and S+HH showed similar results, making the use of lime unnecessary. The RM, like the UCS showed better results for the mixture S+HH+CIM. With regards to deformability, mixture S+HH+CIM showed lower deformations than the other mixtures and a tendency towards stabilisation in unsaturated condition, contrary to mixtures S+HH and S+HH+CAL. During the evaluation of the effect of bad weather, mixture S+HH+CIM showed a 15% reduction of resistance through time, 25% resistance reduction for mixture S+HH+CAL and 50% for mixture S+HH. However, these values are still superior to mixtures using phosphogypsum DH used in past researches. When the microstructure of the samples were evaluated, they showed phosphogypsum DH transformed into HH; this behaviour was more consistent in the mixture S+HH. Finally it can be concluded that mixtures containing phosphogypsum HH are viable application in paving base layers. / O fosfogesso é gerado em grande quantidade a partir da produção do ácido fosfórico nas indústrias de adubos e fertilizantes fosfatados. Pesquisas mostram que o fosfogesso é viável de ser aplicado em áreas como construção civil, indústrias cimenteiras e no setor agrícola, porém em quantidades baixas. Na pavimentação o seu uso também é viável e diversos estudos foram realizados na Universidade Federal de Goiás (UFG) com esse intuito. Neste contexto, o objetivo deste trabalho foi realizar o estudo do uso do fosfogesso hemi-hidratado (HH) em misturas com solo, cimento e cal, a fim de viabilizar e ampliar sua utilização em pavimentação. Para tanto, foi realizado o tratamento térmico do fosfogesso di- hidratado (DH) produzido no estado de Goiás, obtendo assim o fosfogesso HH. Foram estudadas três misturas: Mistura S+HH, constituída de 50% solo e 50% de fosfogesso HH; Mistura S+HH+CIM, constituída de 50% solo, 41% de fosfogesso HH e 9% de cimento e Mistura S+HH+CAL, constituída de 50% solo, 44% de fosfogesso HH e 6% de cal. Foram realizados ensaios de caracterização (utilizando metodologias tradicionais e a metodologia MCT) e ensaios de resistência mecânica (resistência à compressão simples - RCS e módulo de resiliência - MR) para obtenção de parâmetros para aplicação em pavimentação. Foram feitos também ensaios de deformabilidade através de ensaios de adensamento, com propósito de avaliar as deformações do fosfogesso HH ao longo do tempo quando submetido a um carregamento nas condições saturadas e não saturadas. Por fim, foi estudado o efeito das intempéries nas amostras por meio de ensaios de resistência à compressão simples em amostras expostas às intempéries por até 180 dias. Ensaios de microscopia eletrônica de varredura (MEV) foram executados para auxiliar nas análises dos ensaios mencionados anteriormente a partir do comportamento microestrutural. Como resultados foi observado que as amostras contendo fosfogesso HH apresentaram RCS maiores que as amostras contendo apenas solo e misturas com as mesmas proporções de fosfogesso DH. A Mistura S+HH+CIM obteve maior resistência e as Misturas S+HH+CAL e S+HH apresentaram valores semelhantes, tornando-se desnecessário o uso da cal. O MR semelhantemente à RCS apresentou resultados melhores para a Mistura S+HH+CIM. Quanto à deformabilidade, a Mistura S+HH+CIM apresentou menores deformações que as demais misturas e uma tendência à estabilização, na condição não saturada, ao contrário das Misturas S+HH e S+HH+CAL. Ao avaliar o efeito das ações das intempéries, verificou-se redução de 15% da resistência ao longo do tempo da Mistura S+HH+CIM, de 25% para a Mistura S+HH+CAL e 50% para a Mistura S+HH. No entanto, esses valores ainda são superiores às misturas executadas com fosfogesso DH em pesquisas anteriores. A análise microestrutural mostra que, nesse caso, há transformação do fosfogesso DH em HH, sendo esse comportamento mais evidente na Mistura S+HH. Por fim, conclui-se que as misturas contendo fosfogesso HH podem ser viáveis de aplicação em camadas de base de pavimentação.

A fundamental theoretical and experimental study on calcium sulphate scale formation in hydrometallurgical solutions containing various minerals was conducted. A new database for the Mixed Solvent Electrolyte (MSE) model of the OLI Systems® software was developed through fitting of existing literature data such as mean activity, heat capacity and solubility data in simple binary and ternary systems. Moreover, a number of experiments were conducted to investigate the chemistry of calcium sulphate hydrates in laterite pressure acid leach (PAL) solutions, containing Al2(SO4)3, MgSO4, NiSO4, H2SO4, and NaCl at 25–250ºC. The database developed, utilized by the MSE model, was shown to accurately predict the solubilities of all calcium sulphate hydrates (and hence, predict scaling potential) in various multicomponent hydrometallurgical solutions including neutralized zinc sulphate leach solutions, nickel sulphate–chloride solutions of the Voisey’s Bay plant, and laterite PAL solutions over a wide temperature range (25–250°C). The stability regions of CaSO4 hydrates (gypsum, hemihydrate and anhydrite) depend on solution conditions, i.e., temperature, pH and concentration of ions present. The transformation between CaSO4 hydrates is one of the common causes of scale formation. A systematic study was carried out to investigate the effect of various parameters including temperature, acidity, seeding, and presence of sulphate/chloride salts on the transformation kinetics. Based on the results obtained, a mechanism for the gypsum–anhydrite transformation below 100°C was proposed. A number of solutions for mitigating calcium sulphate scaling problems throughout the processing circuits were recommended: (1) operating autoclaves under slightly more acidic conditions (~0.3–0.5 M acid); (2) mixing recycled process solutions with seawater; and (3) mixing the recycling stream with carbonate compounds to reject calcium as calcium carbonate. Furthermore, aging process solutions, saturated with gypsum, with anhydrite seeds at moderate temperatures (~80°C) would decrease the calcium content, provided that the solution is slightly acidic.

De nombreuses transformations de solides en solution, polymorphiques ou non, en industrie minérale ou pharmaceutique, se déroulent par la dissolution d'un premier solide en vue de la cristallisation du second. Au lieu de la voie traditionnelle de séchage, la transformation du gypse (sulfate de calcium dihydrate) en alpha-bassanite (sulfate de calcium hémihydrate) peut s’effectuer en solution aqueuse : en augmentant suffisamment la température, le gypse devient plus soluble dans l'eau que l’hémihydrate, qui a alors la possibilité de cristalliser. Un appareillage et un mode opératoire originaux ont été conçus pour investiguer la sensibilité de la cinétique de la transformation et des caractéristiques des cristaux d’hémihydrate obtenus à ces conditions opératoires. En effet, cette voie de dissolution-recristallisation permet le contrôle du facteur d'aspect des cristaux d’hémihydrate, voire celui de leur taille moyenne et de leur dispersion de taille, par le choix de ses conditions physico-chimiques : température, pH, utilisation d’additifs, et ensemencement de la solution avec des particules d’hémihydrate appropriées. Les techniques d'analyse images sont développées afin d'identifier le rapport d'aspect des particules. Un modèle cinétique prenant en compte la dissolution du gypse, la nucléation et la croissance du sulfate de calcium hémihydrate, les équilibres en phase aqueuse et de solubilité, a été élaboré, et ses équations résolues avec le logiciel MATLAB. Couplée à une méthode numérique d'optimisation, cette résolution sous MATLAB permet d'examiner la validité des hypothèses sur les processus retenus et d'identifier leurs paramètres cinétiques. / In mineral or pharmaceutical industry, many transformations of solids in solution (polymorphic or not), take place by the dissolution of the first solid and the crystallization of the second solid. Instead of the traditional drying process, the conversion of gypsum (calcium sulfate dihydrate) to alpha-bassanite (calcium sulphate hemihydrate) can be carried out in aqueous solution by increasing the temperature sufficiently. At this moment, the gypsum becomes more soluble in water than the hemihydrate, which then has the possibility to crystallize. An apparatus and an original procedure have been designed to investigate the sensitivity of the kinetics of transformation and the characteristics of the hemihydrate crystals obtained under its operating conditions. In fact, this dissolution-recrystallization route allows to control the aspect ratio of the hemihydrate crystals, and even their average size and size dispersion, by the choice of its physicochemical conditions such as temperature, pH, use of additives, and seeding the solution with the appropriate hemihydrate particles. Image analysis techniques are developed to identify the aspect ratio of the particles.A kinetic model taking into account the dissolution of gypsum, the nucleation and the growth of calcium sulphate hemihydrate and their equilibrium in aqueous phase and solubility had been developed and the equations of this model are solved with the help of MATLAB software. Coupled with a numerical optimization method, this resolution under MATLAB makes it possible to examine the validity of the assumptions on the selected processes and to identify their kinetic parameters.

In dieser Arbeit wurde der Einfluss verschiedener Additive (Carbonsäuren, Phosphonsäuren und Retardan P) auf die einzelnen Teilprozesse des Abbindens von Gips an technischen und synthetischen Halbhydraten unter vergleichbaren Bedingungen untersucht. Vorrangig bei der Keimbildung und beim Kristallwachstum wurde ein Einfluss der Additive beobachtet. Das pH-abhängige Wirkungsoptimum kann mit der Speziation der Additive erklärt werden. Ihre Wirkung wird durch Adsorption auf CaSO4-Oberflächen verursacht. Die Untersuchungen ergaben eine bevorzugte Ca-Affinität mit den Flächen (120) und (001) zunehmend von Citronensäure über Weinsäure, HEDP zu HDTMP. Die in verdünnten homogenen Lösungen erhaltenen Ergebnisse sind nicht direkt auf den Abbindeprozess in Pasten übertragbar. In-situ Ramanspektroskopie und Auswaschexperimente weisen in Pasten auf irreversible Adsorption und ein Überwachsen der Additive hin, was zur Abnahme ihrer Wirkung führt. Auf die Festigkeit der abgebundenen Gipskörper zeigen die Additive kaum Einfluss.

A fundamental theoretical and experimental study on calcium sulphate scale formation in hydrometallurgical solutions containing various minerals was conducted. A new database for the Mixed Solvent Electrolyte (MSE) model of the OLI Systems® software was developed through fitting of existing literature data such as mean activity, heat capacity and solubility data in simple binary and ternary systems. Moreover, a number of experiments were conducted to investigate the chemistry of calcium sulphate hydrates in laterite pressure acid leach (PAL) solutions, containing Al2(SO4)3, MgSO4, NiSO4, H2SO4, and NaCl at 25–250ºC. The database developed, utilized by the MSE model, was shown to accurately predict the solubilities of all calcium sulphate hydrates (and hence, predict scaling potential) in various multicomponent hydrometallurgical solutions including neutralized zinc sulphate leach solutions, nickel sulphate–chloride solutions of the Voisey’s Bay plant, and laterite PAL solutions over a wide temperature range (25–250°C). The stability regions of CaSO4 hydrates (gypsum, hemihydrate and anhydrite) depend on solution conditions, i.e., temperature, pH and concentration of ions present. The transformation between CaSO4 hydrates is one of the common causes of scale formation. A systematic study was carried out to investigate the effect of various parameters including temperature, acidity, seeding, and presence of sulphate/chloride salts on the transformation kinetics. Based on the results obtained, a mechanism for the gypsum–anhydrite transformation below 100°C was proposed. A number of solutions for mitigating calcium sulphate scaling problems throughout the processing circuits were recommended: (1) operating autoclaves under slightly more acidic conditions (~0.3–0.5 M acid); (2) mixing recycled process solutions with seawater; and (3) mixing the recycling stream with carbonate compounds to reject calcium as calcium carbonate. Furthermore, aging process solutions, saturated with gypsum, with anhydrite seeds at moderate temperatures (~80°C) would decrease the calcium content, provided that the solution is slightly acidic.

[pt] SO2 é conhecido com um grande contaminante ambiental e muitos países estabeleceram regras para o controle da sua emissão para a atmosfera. Como resultado a maioria das plantas fornecedoras de energia foram equipadas com instalações de dessulfurização de gases de combustão. Embora esta tecnologia seja bem sucedida no abate de SO2, ela gera uma grande quantidade de gesso FGD (flue gas desulfurization) como resíduo. Grandes esforços estão sendo feitos para aproveitar este resíduo (gesso FGD). No presente estudo o gesso FGD foi avaliado como aditivo retardador do tempo de pega substituindo o gesso natural na fabricação do cimento Portland (CP II E-32). Os resultados da caracterização físico-química e morfológica do gesso natural e de gesso FGD identificam um material de alta pureza, sulfato de cálcio di-hidratado para o gesso natural, e presença principalmente de bassanita (CaSO4.0,6H2O) e hannebachite (CaSO3.0,5H2O) com baixas concentrações de impurezas no gesso FGD. Baseado nos resultados, o gesso FGD é uma alternativa adequada para substituir o gesso natural. O tempo de pega mostrou cerca de uma hora de retardo em comparação com gesso natural e seu efeito sobre a resistência à compressão para as amostras de 3, 7 e 28 dias depende da composição das misturas, atingindo um valor máximo para a argamassa com 2,1 porcento de gesso FGD e 1,4 porcentode gesso natural. Também foi estimado o impacto ambiental do gesso FGD, examinando a liberação de seus constituintes inorgânicos seguindo a norma ABNT NBR 10004:2004 e classificando o resíduo como não perigoso e não inerte. / [en] The SO2 is well known as an important environmental contaminant and many countries have established rules to control its emission to the atmosphere and as result most of power supply plants were equipped with flue gas desulfurization systems. Although this technology is successful in the discharge of SO2, its generates a large amount of gypsum FGD (flue gas desulfurization) as a residue. Great efforts are being made to find destinations for this residue. In the present study, the FGD gypsum was evaluated as setting retarder to replace the natural gypsum in the production of Portland cement (CP II E-32). The results of physical-chemistry and morphological characterization of both products, natural and FGD gypsum showed a material of high purity, calcium sulfate dehydrate for natural gypsum, and the presence of bassanite (CaSO4.0,6H2O) and hannebachite (CaSO3.0,5H2O) with low concentrations of impurities for FGD gypsum. Based on the results, the FGD gypsum is a suitable alternative to replace natural gypsum. The setting time with FGD gypsum showed about 1 hour delay compared with natural gypsum and its effect on compressive strength, for samples of 3, 7 e 28 days, depend the composition of the mixtures, reaching the maximum value for the mixture of 1,4 weight percent natural gypsum and 2,1 weight percent FGD gypsum. The FGD gypsum environmental impact was evaluated by determining its potential in releasing inorganic constituents, following the standard ABNT NBR 10004:2004, and it was classified as a non-hazardous and non-inert.

In dieser Arbeit wurde der Einfluss verschiedener Additive (Carbonsäuren, Phosphonsäuren und Retardan P) auf die einzelnen Teilprozesse des Abbindens von Gips an technischen und synthetischen Halbhydraten unter vergleichbaren Bedingungen untersucht. Vorrangig bei der Keimbildung und beim Kristallwachstum wurde ein Einfluss der Additive beobachtet. Das pH-abhängige Wirkungsoptimum kann mit der Speziation der Additive erklärt werden. Ihre Wirkung wird durch Adsorption auf CaSO4-Oberflächen verursacht. Die Untersuchungen ergaben eine bevorzugte Ca-Affinität mit den Flächen (120) und (001) zunehmend von Citronensäure über Weinsäure, HEDP zu HDTMP. Die in verdünnten homogenen Lösungen erhaltenen Ergebnisse sind nicht direkt auf den Abbindeprozess in Pasten übertragbar. In-situ Ramanspektroskopie und Auswaschexperimente weisen in Pasten auf irreversible Adsorption und ein Überwachsen der Additive hin, was zur Abnahme ihrer Wirkung führt. Auf die Festigkeit der abgebundenen Gipskörper zeigen die Additive kaum Einfluss.