A Ãgua à um recurso natural de valor inestimÃvel. Mais que um insumo indispensÃvel à produÃÃo à um recurso estratÃgico para o desenvolvimento econÃmico. A regiÃo semiÃrida, assim como o resto mundo, sofre cada vez mais com as alteraÃÃes climÃticas, associadas ao aquecimento global. Essas mudanÃas climÃticas tÃm impactos tanto na oferta como na demanda por Ãgua nessa regiÃo. Na regiÃo Nordeste do Brasil, onde hà uma distribuiÃÃo irregular de chuvas, a produÃÃo agrÃcola à substancialmente melhorada atravÃs do uso da irrigaÃÃo. A adoÃÃo do uso da irrigaÃÃo nessas regiÃes semiÃridas causa modificaÃÃes no regime de umidade dos solos e pode ainda alterar suas propriedades e processos. O objetivo deste trabalho foi investigar os efeitos causados durante 23 anos de irrigaÃÃo sobre solos calcÃrios no semiÃrido cearense, com Ãnfase no estudo das alteraÃÃes pedogenÃticas proporcionadas pelo uso dessa prÃtica. As Ãreas escolhidas para o estudo estÃo localizadas no perÃmetro irrigado localizado na Chapada do Apodi no municÃpio de Limoeiro do Norte-CE. Foram realizadas 8 tradagens em cada Ãrea (na Ãrea irrigada e na Ãrea externa e limÃtrofe ao pivÃ). Posteriormente, em cada uma das Ãreas, foram abertas trincheiras para realizaÃÃo das descriÃÃes morfolÃgicas e coleta de amostras de solo para fins de caracterizaÃÃo fÃsica, quÃmica, mineralÃgica e micromorfolÃgica. Os resultados referentes Ãs tradagens indicam terem ocorrido diferenÃas significativas na Ãrea irrigada quando comparada à Ãrea nÃo irrigada, sendo verificadas a intensificaÃÃo da dissoluÃÃo de CaCO3 e o aumento dos teores de cÃlcio, sÃdio e fÃsforo. AlÃm disso, o solo irrigado sofreu alteraÃÃes dos seus atributos fÃsicos, sendo verificado aumento da sua densidade de partÃculas, diminuiÃÃo da permeabilidade do solo ao ar e a formaÃÃo de poros menos contÃnuos. Os resultados das anÃlises dos perfis mostraram que os 23 anos de irrigaÃÃo tiveram efeito no solo irrigado, tornando-o mais evoluÃdo em comparaÃÃo ao nÃo irrigado, isso foi verificado atravÃs dos resultados obtidos na morfologia com aumento da espessura do solum, na fÃsica com a menor relaÃÃo silte/argila e maior conteÃdo argila nesse solo, na mineralogia com indÃcios de aumento da caulinita e neoformaÃÃo de minerais interestratificados e na micromorfologia com o maior grau de pedalidade. O solo irrigado foi classificado como Chernossolo HÃplico carbonÃtico saprolÃtico, por apresentar horizonte A chernozÃnico seguido de horizonte B incipiente e possuir argila de atividade alta. / Water is a priceless natural resource. More than an essential input to production is a strategic resource for economic development. The semiarid region, as well as the rest of the world, suffer more with climate change associated with global warming. These climate changes have impacts on both supply and demand for water in this region. In northeastern Brazil, where there is an uneven distribution of rainfall, agricultural production is substantially improved through the use of irrigation. The adoption of the use of irrigation in these semiarid regions leads to changes in soil moisture regime and may even change its properties and processes. The objective of this study was to investigate the effects during 23 years of irrigation on calcareous soils in semiarid CearÃ, with emphasis on the study of pedogenetic changes provided by this practice. The areas chosen for study are located in Chapada do Apodi located in the city of Limoeiro do Norte - Ce. 8 amostrgens were performed in each area (in the irrigated area and the area outside and adjacent to the pivot). Subsequently, in each of the areas, trenches were opened to perform the morphological descriptions and collected soil samples for physical characterization, chemical, mineralogical and micromorphological. The results indicate significant differences have occurred in the irrigated area compared to non-irrigated area, and verified the increased dissolution of CaCO3 and increased levels of calcium, sodium and phosphorus. Furthermore, the flooded soil has changed its physical characteristics, and found an increase in density of particles decreased permeability of the soil air and the formation of pores less continuous. The analysis results showed that the profiles of 23 years of irrigation had effect on irrigated soil, making it more evolved in comparison to non-irrigated, it was verified by the results obtained in morphology with increasing soil thickness in physics with a lower silt / clay ratio and higher clay content in soil, mineralogy with evidence of increased neoformation of kaolinite and interstratified minerals, in micromorphology with the highest degree of pedalidade. The irrigated soil was classified as Chernosol by presenting chernozÃnico horizon followed by an incipient B horizon and possess high activity clay.

Muitos organismos vivos, tal como seus constituintes, são formados por sistemas químicos complexos que envolvem a interação entre compostos orgânicos e inorgânicos ligados química e/ou fisicamente. Nestes sistemas as matrizes orgânicas são geralmente compostas por macromoléculas como polissacarídeos e proteínas. Essas moléculas têm o papel de direcionar a nucleação e o crescimento da porção inorgânica. O uso de superfícies metálicas adequadas recobertas por este tipo de filme híbrido tem potencial aplicação em implantes de substituição óssea, no qual são requeridas superfícies quimicamente inertes, mas que ao mesmo tempo estimulem processos de calcificação. Nesta tese estudou-se o crescimento de CaCO3 sobre superfícies metálicas de alumínio e aço inox recobertas por matrizes orgânicas compostas por diferentes poliânions e pelo policátion quitosana, na forma de filmes montados camada-a-camada (do inglês LbL), na presença ou não de fosfolipídeos (filmes Langmuir-Blodgett), formando um meio confinado para o crescimento do mineral. Diferentes técnicas foram utilizadas: microscopia eletrônica, microscopia de força atômica, espectroscopias de reflexão nas regiões do Uv-vis, e do infravermelho, Raman, espalhamento e difração de raios-X. Estudou-se a influência de diferentes grupos carregados dos fosfolipídeos e dos poliânions, tal como sua conformação, no crescimento de CaCO3. O tipo de interação entre o poliânion e a quitosana leva ao crescimento de matrizes poliméricas com diferenças em suas espessuras e capacidade de retenção de líquido, modificando as condições de supersaturação local e influenciando no tipo de estrutura de CaCO3. Puderam ser identificados dois polimorfos formados sobre os filmes orgânicos de poli(ácido acrílico) e quitosana, sugerindo que existem dois diferentes sítios onde a nucleação pode ser iniciada: a partir da solução de CaCl2 aprisionada na matriz polimérica e o outro a partir dos íons cálcio ligados como contra-íons aos grupos negativamente carregados do poliânion. Na presença do pré-recobrimento LB, a natureza da cabeça polar do fosfolipídeo direciona o tipo de ligação e crescimento da matriz polimérica, que levam ao crescimento de partículas de CaCO3 com morfologia e tamanho variados, explicados em termos da presença de ambientes com diferenças de concentrações locais de Ca2+. Além disso, verificou-se que a rugosidade superficial dos suportes metálicos pode favorecer a formação do polimorfo de CaCO3 cineticamente mais estável, mostrando que o processo de cristalização sobre estes suportes é um processo governado por difusão. A hidrofilicidade dos suportes é aumentada pela presença da matriz orgânica e pela presença de CaCO3 sobre as matrizes. O crescimento de CaCO3 em meios confinados tridimensionais, formados por membranas de policarbonato modificadas com filme finos de polieletrólitos, também foi estudado. Este tipo de molde leva à formação de estruturas cilíndricas que seguem a morfologia dos poros da membrana. A presença de poli(ácido acrílico) leva a formação de estruturas cilíndricas ocas, enquanto que cilindros completamente preenchidos foram formados nos poros contendo quitosana na última camada. Estes resultados foram explicados com base em diferenças na etapa de nucleação: na presença de PAA a nucleação de CaCO3 deve iniciar-se a partir dos íons Ca2+ ligados ao poliânion que, por sua vez, está ligado diretamente às paredes do molde; já na presença que quitosana, com maior capacidade de retenção de liquido e sem interação específica com Ca2+ a nucleação e seqüente cristalização devem ocorrer por todo o poro da membrana. As estruturas formadas são em sua maioria monocristais de calcita hexagonal orientadas na direção cristalográfica <2 -2 1>. / Some living organisms as well as their constituents are formed by complex chemical systems which involves the interaction among organic and inorganic compounds bounded physically or chemically. In these systems the organic matrices are usually composed by macromolecules like polysaccharides and proteins. These molecules have an important hole in tailoring the nucleation and the sequent growth of the inorganic portion. Metallic surfaces coated with these hybrid films have potential application as implants for bone substitution for which the surfaces must be chemically inert but at the same time they should stimulate calcification processes. In this present thesis we studied the growth of CaCO3 over aluminium and stainless steal surfaces coated with layer-by-layer films composed by different polyanions and chitosan as polycation, in the presence or not of phospholipids (Langmuir-Blodgett films). These organic matrices formed a confined medium within which CaCO3 particles were growth. Different techniques were applied in order to understand these systems: electronic microscopy, atomic force microscopy, UV-Vis and infrared reflection spectroscopy, Raman, and X-ray scattering and diffraction. We studied the influence of the different charged groups of the phospholipids and the polyanion as well as their conformation on CaCO3 growth. The type of interaction between the polycation and the polyanions tailors the growth of the organic matrices, forming films with different thickness and different water retention abilities which change the local supersaturation conditions changing the structure of the CaCO3 formed. Two types of CaCO3 polymorphs were growth over poly(acrylic acid) (PAA) and chitosan films suggesting that there are two sites where the nucleation can be started: the CaCl2 solution retained in the gel-like organic films and the Ca2+ ions bounded to the negative groups of the polyanion. In the presence of the LB pre-coating, the nature of the phospholipid polar head tailors the binding and the growth of the polymeric matrices leading to the formation of CaCO3 particles with difference in their sizes and morphologies. This result was explained in basis of the differences in the Ca2+ local concentrations in each situation. Moreover, it was observed that the surface roughness of the supports can favour the formation of vaterite, the kinetically most stable CaCO3 polymorph, showing that the crystallization may be guided by diffusion processes. The hidrophilicity of the supports was improved by the presence of both organic and hybrid films. The growth of CaCO3 in tridimentional confined mediums was done using LbL modified polycarbonate membranes as template. This template leads to the formation of cylindrical CaCO3 particles following the morphology of the membrane pores. CaCO3 tube-like structures were formed in presence of PAA, while rod-like structures were formed in presence of chitosan in the top LbL layer. These results were explained on basis of the difference in the nucleation stages: in the presence of PAA the nucleation starts on the Ca2+ ions bounded to the polyanion that is linked to the walls of the template; in the presence of chitosan that presents higher water retention ability and has no specific interaction with Ca2+ ions, the nucleation and sequent crystallization should occur through the entire pore of the membrane. The electron diffraction patterns showed that the CaCO3 structures are single crystals of the calcite polymorph oriented in < 2 -2 1> crystallographic direction.

Orientador: José Ricardo Pelaquim Mendes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-23T21:31:12Z (GMT). No. of bitstreams: 1 Rigobello_AnaLuciaGodoy_M.pdf: 19440225 bytes, checksum: 976868faec9ffa0e37433dfbff01c239 (MD5) Previous issue date: 2013 / Resumo: Incrustações consistem em um subproduto indesejável na forma de depósitos cristalinos, provenientes da precipitação de sais presentes na água. Dependendo da natureza da incrustação e da composição do :fluido a deposição pode ocorrer no reservatório de petróleo, próximo ao poço causando dano à formação, ou em instalações de produção ocasionando graves problemas operacionais além do declínio da produtividade. O controle de incrustação atualmente tem sido um problema desafiador na indústria do petróleo além de impactar fortemente no valor econômico do produto final. A variedade e complexidade dos tipos de tal deposição formados aumentam a dificuldade de desenvolver métodos adequados para aliviar esses problemas. Anualmente as empresas de petróleo gastam milhões de dólares na manutenção de equipamentos e produção, e alguns dos mais altos custos ocorrem na prevenção da incrustação. São necessários estudos em diferentes áreas com o intuito de reduzir e combater a formação de depósitos destes sais, evitando assim perdas e danos à formação. A prevenção e mitigação da incrustação é de grande importância além de ser bastante complexa. Um método eficaz é através do cálculo do chamado índice de incrustação, representado neste trabalho por Is. A presente pesquisa visa o estudo de incrustação, em especial incrustações por carbonato de cálcio no sistema de produção como um todo, bem como o estudo das variáveis que influenciam em sua formação através do mapa do potencial de incrustação. Com o intuito de realizar tal estudo, foi utilizado um modelo termodinâmico previamente existente para realizar os cálculos do índice baseado em dados de poços hipotéticos, além de exemplos reais. O modelo mostrou-se válido, e, conforme esperado, obteve-se um comportamento de variação de pressão, temperatura e pH condizente ao descrito nas literaturas / Abstract: Scale consists in an undesirable product in the form of crystalline deposits from precipitation of salts in the water. Depending on the scale nature and the composition of fiuid deposition can occur in the oil reservoir, near the well damaging the formation, or in production facilities causing serious operational problems in addition to the decline of productivity. The control of scale currently has now been a challenging problem in the oil industry and also impact strongly on the economic value of the final product. The variety and complexity of this type of deposition increases the difficulty of developing suitable methods to relieve these problems. Each year oil companies spend millions of dollars in equipment maintenance and production, and some of the highest costs occur in the scale prevention. Several studies are needed in different areas in order to reduce and control the formation of deposits of these salts, thus avoiding damages to the formation. The scaling prevention and mitigation are of great importance as well as being quite complex. An effective method is by calculating the index scale, represented in this work by Is. This research aims to study scale, specially calcium carbonate scale into the production system as a whole, as well as the study of the variables that infiuence its formation through the map of scale potential. ln order to accomplish this study, we used a previously existing thermodynamic model to perform calculations of the index based on data from hypothetical wells and real examples. The model proved to be valid, and, as expected, there was obtained one behavior of variation of pressure, temperature and pH consistent to that described in the literature / Mestrado / Explotação / Mestra em Ciências e Engenharia de Petróleo

Scaling due to calcium carbonate precipitation is a major problem in cooling water circuits in many of Eskom power stations. Some earlier studies have suggested that the natural organic matter (NOM) present in the cooling water may reduce the amount of scaling by limiting the formation of calcium carbonate precipitation. It is therefore the interest of this study to investigate further the role of the NOM in calcium carbonate precipitation at Hendrina power station. The raw water and cooling water were analysed for the major metal ions, anions, alkalinity, conductivity and total organic matter to determine the precipitation potentials of calcite and aragonite using MINTEQA2 speciation program. The NOM was isolated from the raw and cooling water using ion exchange resins, XAD-8/XAD-4 resins and ultrafiltration membranes with molecular weight cut-offs of 100 kDa, 10 kDa and 1 kDa. The isolated fractions were then characterized by ultraviolet and visible absorbance methods and high performance size exclusion chromatography. The effect of the isolated fractions of the NOM from the cooling water on calcium carbonate precipitation was then investigated. The results indicated the presence calcium carbonate precipitation in the cooling water, but the raw water was undersaturated with calcium carbonate. The NOM isolated from the raw water indicated the predominance of the hydrophobic acid NOM (74.17 %) and to a lower extent the presence of hydrophilic acid NOM (34.49%). The NOM isolated from the cooling water also showed the predominance of the hydrophobic acid NOM (69.25 %) and to a lower extent the presence of the hydrophilic neutral acid NOM (20.13 %) and minimal presence of hydrophilic acid NOM (9.51 %). The results obtained from high pressure size exclusion chromatography analyses indicated that in both the raw water and cooling water the NOM was having a low molecular weight (<13.2030 kDa). The specific ultraviolet absorbance (SUVA) of the raw water was high (>4) which also suggested that it contained predominantly hydrophobic NOM and that of the cooling i water was in the range 2-4 suggesting that it contained a mixture of the hydrophobic and hydrophilic acid NOM. The hydrophobic acid, hydrophilic acid and hydrophilic neutral acid NOM fractions isolated from the cooling water reduced the amount of calcium carbonate precipitate formed in synthetic water sample. This effect was more pronounced with hydrophobic and hydrophilic acid NOM fractions than with the hydrophilic neutral acid NOM fraction. / Dr. M. Shumane

Differential thermal analysis le a dynamic process for observing the thermal decomposition of reacting sub- stances, The heart of the equipment for this process is a vanadium steel sample holder approximately two inches in diameter and one inch thick. Two wells, approximately one inch apart, serve as holders for the sample and reference material. Inserted in the bottom of each well is a thermo- couple of platinum, platinum-rhodeus. Attached to the thermocouples is an amplifier and a recorder.

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<p> An analysis of reported and theoretical methods of precipitating calcium carbonate from aqueous solution is presented, with emphasis on methods that generate the anion in the presence of Ca(++) ion.</p> <p> A new CaCO3 precipitation method referred to as precipitation from quasi-homogeneous solution and suitable for digital processor control is developed. This technique is then used to investigate the effects of ionic strength and Mg(++) ion on calcium carbonate nucleation.</p> <p> A minicomputer based interactive information system, capable of automatic data logging and processing of experimental results in studies using processor controlled precipitation of CaCO3 from quasi-homogeneous solution, is implemented and tested.</p> / Thesis / Master of Science (MSc)

Shrinking and swelling in Yazoo Clay is a cause of concern for construction projects in Mississippi. This thesis investigated the effects of adding lime and Douglas Fir biochar on the shrinking and swelling capabilities of Yazoo Clay. Samples of Yazoo Clay were mixed with the additives in defined ratios and subjected to the free swell test and the COLE(rod) test. Biochar addition reduced the COLE(rod) of the samples a large amount, while increasing the swelling potential of the clay samples. The addition of lime slightly reduced both the shrinking and swelling potentials of the samples. The mineralogical variability of Yazoo Clay vertically and horizontally could limit the applicability of these results across the formation and is important to be considered before further application. While constrained to one location, this study showed the influence of biochar and lime on the shrinking and swelling capabilities of Yazoo Clay.

Abstract Amorphous Calcium Carbonate (ACC) is a naturally occurring amorphous form of the widely distributed mineral calcium carbonate (CaCO3). ACC has been found increasingly as a precursor phase, calcium storage site, or strengthening structural phase in a wide array of different biomineralizing organisms. An accurate understanding of the widely used classic carbonate-water paleothermometry relies on formation of CaCO3 minerals and associated oxygen isotope effects. Moreover, ACC has oft been pointed to as a possible reason for non-equilibrium isotope effects, also called vital effects, in biogenic carbonates. It is, therefore, vital to understand whether ACC can reach equilibrium with its surrounding solution, as well as the role of ACC precursors in the isotopic composition and evolution of the final crystalline phase they transform into. This study is designed to answer these questions through the precipitation of stable ACC by two methods, the alkaline method (AM) which utilizes high pH to precipitate ACC, and the silica method (SM) which envelopes precipitating ACC particles in silica vesicles to prevent crystallization. These differently precipitated ACCs are then subjected to several different experimental treatments. This is achieved by monitoring the crystallization by X-ray Diffraction (XRD), and isotopic evolution of the ACC precipitates by Isotope Ratio Mass Spectrometry (IRMS) as they age and concurrently crystallize in parent solution, or in 18O enriched re-equilibration solution. This research indicated a marked difference in the crystallization behaviour, isotopic composition, and isotopic evolution of ACC produced by these two precipitation methods. With the AM method, ACC precipitates (AM-ACC) crystallized more predictably to calcite and maintained δ18O signatures that were slightly lower than the equilibrium CO32- and resisted further isotopic exchange with surrounding solution. We propose that the former is mostly due to an incomplete DIC-water oxygen isotope equilibrium prior to the AM-ACC precipitation and the latter is a result of the high pH of the precipitating solution decreasing the solubility of the precipitated ACC phase, disallowing isotope exchange, and favouring crystallization by solid-state transformation. Conversely, while ACC precipitated using the SM (SM-ACC) yielded much more variable results, both in terms of mineralogical identity upon crystallization, and δ18O values. Isotopic results were much closer to the expected equilibrium δ18O value for calcite, hinting at an expedited oxygen isotope exchange between SM-ACC and parent solution. Furthermore, SM-ACC was capable of isotopic exchange with the 18O enriched re-equilibration solution, a feat corresponding AM-ACC was incapable of. Overall, our experimental results gleaned here that precipitation method or precipitation environment play a critical role in the isotopic evolution of precursor ACC to crystalline CaCO3, suggesting ACC as an important source of the vital effect. / Thesis / Master of Science (MSc)