O manto litosférico é depletado em elementos incompatíveis como potássio, rubídio e estrôncio, confinado sob altas condições de pressão e caracterizado por uma composição e mineralogia específicas: espinélios anidros e/ou granada lherzolitos e harzburgitos. Esta região pode ser hidratada e enriquecida em elementos incompatíveis (ex. potássio) através de processos de subducção, onde a placa oceânica subductada leva consigo material pelágico composto de argilominerais e filossilicatos. A transferência de massa entre a placa subductada com os sedimentos e a cunha mantélica ocorre primeiramente através da liberação de fluidos aquosos gerados pela devolatilização de minerais hidratados. Neste contexto, a esmectita destaca-se como um dos mais importantes minerias responsáveis pelo enriquecimento do manto litosférico em água e elementos incompatíveis, quando sua estrutura é desestabilizada. Com o aumento da pressão e temperatura, esmectitas perdem sua água interlamelar, ao mesmo tempo em que se transformam em camadas mistas esmectita-ilita. Nestas condições de desidratação, e com o aumento da pressão, mudanças estruturais ocorrem e, havendo potássio disponível no sistema, o argilomineral evolui para uma mica muscovita. Considerando este contexto, o presente trabalho tem como objetivo verificar o comportamento estrutural da esmectita saturada em potássio modificando as variáveis pressão e temperatura: (1) sob pressão atmosférica em diferentes temperaturas (100º a 700ºC); (2) sob pressão de até 11.5 GPa sem temperatura - Diamond Anvil Cell (DAC); (3) sob diferentes pressões com aplicação de temperatura: 2.5GPa (400º a 700ºC) e 4.0GPa (200º a 700ºC). Os resultados das técnicas de análise de Difração de raios X, Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET) e Espectroscopia por Infravermelho (FTIR) sugerem que, sob uma pressão de 2.5 GPa, que é cerca de 75km de profundidade no manto, e a aproximadamente 500ºC, a esmectita transforma-se em muscovita, enquanto sob a pressão de 4.0 Gpa, equivalente a cerca de 120 km de profundidade, a mesma transformação ocorre a 400ºC. Estes resultados contribuem significativamente para o entendimento de como a desidratação do sedimento pelágico ocorre em um processo de subducção, bem como o comportamento da esmectita sob a influência do aumento de pressão e temperatura. / The lithospheric mantle is depleted regarding to incompatible elements as potassium, rubidium and strontium, confined under pressure conditions and characterized by a specific mineralogy and composition, basically as anhydrous spinel and/or garnet lherzolite and harzburgite. This region can be hydrated and enriched in incompatible elements (e.g. potassium) through subduction processes that bring pelagic material, composed of clay minerals and other phyllosilicates, together with the hydrated subducted oceanic slab. A mass transfer from the subducted slab plus sediments into the mantle wedge occurs primarily through the release of aqueous fluids produced by devolatilization of hydrated minerals. In this context, smectite stands out as one of the most important minerals responsible for enriching the lithospheric mantle with water and incompatible elements when its structure is destabilized. By pressure and temperature increasing smectite lose its interlayer water, at the same time that it transforms into a mixed-layer illite-smectite. In this condition of dehydration and with increasing pressure, structural changes occur and, having potassium available on the system, the clay mineral evolves into a muscovite mica. Considering this context, we verified the structural behavior of potassium saturated smectite modifying variables pressure and temperature: (1) under atmospheric pressure at different temperatures (100º to 700º C); (2) under pressure up 11.5 GPa without temperature - Diamond Anvil Cell (DAC); (3) under different pressures with temperature application: 2.5 GPa (400º to 700º C) and 4.0 GPa (200º to 700º C). The results of the analysis techniques of X-ray diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Infrared Spectroscopy (FTIR), suggest that under the pressure of 2.5 GPa, which is about 75km depth in the mantle, and at around 500ºC smectite transforms into muscovite, while under the pressure of 4.0 GPa, equivalent to around 120km depth, the same transformation occurs at 400ºC. These results contribute significantly to understanding how pelagic sediment dehydration occurs in a subduction process, as well as the behavior of smectite under the influence of increasing pressure and temperature.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-11T13:13:10Z No. of bitstreams: 1 JOÃO FERNANDES DUARTE NETO - DISSERTAÇÃO (PPGCEMat) 2015.pdf: 2295774 bytes, checksum: d73166400ea15685ca449c373a12dc20 (MD5) / Made available in DSpace on 2018-07-11T13:13:10Z (GMT). No. of bitstreams: 1 JOÃO FERNANDES DUARTE NETO - DISSERTAÇÃO (PPGCEMat) 2015.pdf: 2295774 bytes, checksum: d73166400ea15685ca449c373a12dc20 (MD5) Previous issue date: 2015-02-24 / Este trabalho investigou o processo de adsorção, equilibrio e cinética de argilas esmectíticas da cidade de Boa Vista (Paraíba), usadas como adsorventes de corantes com comportamentos químicos distintos - rodamina B (RB), catiônico, e alaranjado de metila (AL), aniônico - em meio aquoso. Essas argilas foram escolhidas devido às suas propriedades características do argilomineral esmectítico, que possui sítios quimicamente ativos, provocado pela substituição isomórfica e interação das arestas, tornando-o atrativo sua aplicação para fins adsortivos. As argilas utilizadas são conhecidas como bentonita chocolate e bentonita chocobofe. Esses materiais foram utilizados na forma natural e após tratamento com carbonato de sódio, ácido clorídrico e organofilização (sal quaternário de amônio PRAEPAGEN). Todos os adsorventes foram caracterizados por fluorescência de raios X, difração de raios X, análises térmicas (TG, DTG e DTA) e determinação de tamanho de partícula. Os ensaios de adsorção dos corantes foram examinados por sistema de bateladas, alterando tempo de contato, quantidade de adsorvente, concentração dos corantes e pH inicial. Para a análise do comportamento de adsorção foi utilizado espectrofotometria UV-VIS. O modelo de isoterma de Freundlich foi o que melhor se ajustou aos dados experimentais das argilas naturais e modificadas. Porém nos processos adsortivos envolvendo as argilas organofilizadas, na interação com RB, tanto o modelo de Langmuir como o de Freundlich apresentaram um bom ajuste aos dados experimentais. Os dados cinéticos de adsorção foram ajustados ao modelo de pseudo-segunda ordem (R2>0,9). Os testes de capacidades de adsorção permitiram concluir que a maior eficiência em remover a RB ocorre quando as argilas são tratadas com ácido clorídrico. A maior eficiência na remoção do AL ocorre quando as argilas estudadas foram as organofilizadas. De modo geral, as argilas esmectíticas estudadas se mostraram adsorventes adequados para a remoção do corante RB, sendo, no entanto, necessário tratamentos específicos para maximizar ou melhorar a capacidade de adsorção dos corantes RB e AL. / This study investigated the process of adsorption, equilibrium and kinetics, of smectite clays from Boa Vista of Paraíba used as chemical adsorbents of dyes with different ionic behavior in aqueous media. Smectite clays known as chocolate and chocobofe and the dyes Rhodamine B (RB) (cationic) and Methyl Orange (AL), (anionic) were used in this study. The adsorbents were characterized by X-ray fluorescence, X-ray diffraction, thermal analysis (TG, DTA and DTG) and determination of particle size. Clays have been used in natural form and after treatment with sodium carbonate, acid and organophilization (quaternary ammonium salt – PRAEPAGEN). The dye adsorption was examined by a batch system, changing: contact time, amount of adsorbent, dye concentration and initial pH. UVVIS spectrophotometry was used for the analysis of the adsorption behavior. The clays were characterized as smectite clays and the efficiency of the treatments was confirmed by X-ray fluorescence and X-ray diffraction. The model of Freundlich isotherm presented the best fit to the experimental data of natural clays. However, in the adsorptive processes involving clays organophilizated both the Langmuir model and the Freundlich model showed good fitting to the experimental data. The kinetic adsorption data were fitted to the model of pseudo-second order (R2> 0.9). The adsorption capacities test showed that the highest efficiency in removing RB occurs when the clays are treated with hydrochloric acid. The highest efficiency of the removal of AL occurs when the clays are organophilizated. In general, the smectite clays were suitable adsorbent for the removal of the dye RB. However, special treatment is necessary to maximize or improve the adsorption ability of the dyes AL and RB.

O manto litosférico é depletado em elementos incompatíveis como potássio, rubídio e estrôncio, confinado sob altas condições de pressão e caracterizado por uma composição e mineralogia específicas: espinélios anidros e/ou granada lherzolitos e harzburgitos. Esta região pode ser hidratada e enriquecida em elementos incompatíveis (ex. potássio) através de processos de subducção, onde a placa oceânica subductada leva consigo material pelágico composto de argilominerais e filossilicatos. A transferência de massa entre a placa subductada com os sedimentos e a cunha mantélica ocorre primeiramente através da liberação de fluidos aquosos gerados pela devolatilização de minerais hidratados. Neste contexto, a esmectita destaca-se como um dos mais importantes minerias responsáveis pelo enriquecimento do manto litosférico em água e elementos incompatíveis, quando sua estrutura é desestabilizada. Com o aumento da pressão e temperatura, esmectitas perdem sua água interlamelar, ao mesmo tempo em que se transformam em camadas mistas esmectita-ilita. Nestas condições de desidratação, e com o aumento da pressão, mudanças estruturais ocorrem e, havendo potássio disponível no sistema, o argilomineral evolui para uma mica muscovita. Considerando este contexto, o presente trabalho tem como objetivo verificar o comportamento estrutural da esmectita saturada em potássio modificando as variáveis pressão e temperatura: (1) sob pressão atmosférica em diferentes temperaturas (100º a 700ºC); (2) sob pressão de até 11.5 GPa sem temperatura - Diamond Anvil Cell (DAC); (3) sob diferentes pressões com aplicação de temperatura: 2.5GPa (400º a 700ºC) e 4.0GPa (200º a 700ºC). Os resultados das técnicas de análise de Difração de raios X, Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET) e Espectroscopia por Infravermelho (FTIR) sugerem que, sob uma pressão de 2.5 GPa, que é cerca de 75km de profundidade no manto, e a aproximadamente 500ºC, a esmectita transforma-se em muscovita, enquanto sob a pressão de 4.0 Gpa, equivalente a cerca de 120 km de profundidade, a mesma transformação ocorre a 400ºC. Estes resultados contribuem significativamente para o entendimento de como a desidratação do sedimento pelágico ocorre em um processo de subducção, bem como o comportamento da esmectita sob a influência do aumento de pressão e temperatura. / The lithospheric mantle is depleted regarding to incompatible elements as potassium, rubidium and strontium, confined under pressure conditions and characterized by a specific mineralogy and composition, basically as anhydrous spinel and/or garnet lherzolite and harzburgite. This region can be hydrated and enriched in incompatible elements (e.g. potassium) through subduction processes that bring pelagic material, composed of clay minerals and other phyllosilicates, together with the hydrated subducted oceanic slab. A mass transfer from the subducted slab plus sediments into the mantle wedge occurs primarily through the release of aqueous fluids produced by devolatilization of hydrated minerals. In this context, smectite stands out as one of the most important minerals responsible for enriching the lithospheric mantle with water and incompatible elements when its structure is destabilized. By pressure and temperature increasing smectite lose its interlayer water, at the same time that it transforms into a mixed-layer illite-smectite. In this condition of dehydration and with increasing pressure, structural changes occur and, having potassium available on the system, the clay mineral evolves into a muscovite mica. Considering this context, we verified the structural behavior of potassium saturated smectite modifying variables pressure and temperature: (1) under atmospheric pressure at different temperatures (100º to 700º C); (2) under pressure up 11.5 GPa without temperature - Diamond Anvil Cell (DAC); (3) under different pressures with temperature application: 2.5 GPa (400º to 700º C) and 4.0 GPa (200º to 700º C). The results of the analysis techniques of X-ray diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Infrared Spectroscopy (FTIR), suggest that under the pressure of 2.5 GPa, which is about 75km depth in the mantle, and at around 500ºC smectite transforms into muscovite, while under the pressure of 4.0 GPa, equivalent to around 120km depth, the same transformation occurs at 400ºC. These results contribute significantly to understanding how pelagic sediment dehydration occurs in a subduction process, as well as the behavior of smectite under the influence of increasing pressure and temperature.

Orientadores: João Alexandre Ferreira da Rocha Pereira, Cesar Augusto Moraes de Abreu / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-06T05:19:09Z (GMT). No. of bitstreams: 1 Barauna_OsmarSouto_D.pdf: 2829115 bytes, checksum: bf2e35aadb3829156a0b6febbd04582f (MD5) Previous issue date: 2006 / Resumo: A utilização de argilas do tipo esmectita como agente descorante de óleo de soja, satisfazendo as exigências comerciais e se equivalendo à capacidade adsortiva da argila-padrão importada (Tonsil Supreme 180 FF), foi praticada através do desenvolvimento do processo adsortivo de pigmentos clorofila e carotenóides. A argila esmectítica adsorvente de origem da bacia sedimentar do Araripe/PE é constituída por argilomine rais (predominantes) e uma fração detrítica grosseira composta essencialmente por quartzo, calcita e gipsita. Procedeu-se à ativação ácida (HCl), previamente à aplicação no descoramento, favorecendo-se o desenvolvimento de atividades adsortivas da argila. Os parâmetros com base no desenvolvimento do processo de adsorção de pigmentos com a argila esmectítica ácido-ativada comprovaram a sua aptidão para produzir a despigmentação do óleo vegetal em teor da clorofila-a, repre sentando uma capacidade adsortiva de qAm = 144,93 mg.g-1, significan do ordem de grandeza próxima àquela determinada para a argila Tonsil de qAm = 166,67 mg.g-1. Equilíbrios de isotermas favoráveis nos dois ca sos foram quantificados segundo os parâmetros de adsorção de KAargila = 23,00 cm3.g-1 e KAtonsil = 20,00 cm3.g-1. Resultantes de avalia ções cinéticas experimentais, fundamentados em um modelo do tipo Langmuir-Freundlich, foram estimadas as constantes cinéticas de adsorção da argila (kaAargila = 0,2488 ± 0,0913) e do adsorvente Tonsil (kaAtonsil = 0,0839 ± 0,0219). Caracterizadas as atividades adsortivas das argilas em razão de suas acidez superficiais, traduzidas em números de sítios ácidos, foram identificadas características de sítios fortes (183,90 x 1020 sítios/g de argila), responsáveis pela adsorção dos pigmentos. A argila esmectítica acidificada demonstrou possuir propriedades adsortivas similares a do adsorvente importado, tendo servido à aplicação no processo de descoramento de óleo de soja / Abstract: Smectite clays from the Araripe sedimentary basin were employed as bleaching agents of soy bean oil and compared with adsorption capacity of the imported reference-clay (Tonsil Supreme 180 FF). The system was tested with chlorophyllous pigments and carotenoids. The smectite was mainly composed by a coarse detrital fraction of quartz, calcite and gypsum. To develop its adsorption capacity it was previously activated with acid (HCl). The parameters of the process indicated that the bleaching property of the activated clay in terms of chlorophyll-a representing an adsorption capacity of qm = 144.93 mg.g-1, which had an order magnitude near to that of Tonsil, qm = 166.67 mg.g-1. The adsorption parameters of the equilibrium isotherms for the two cases were KAclay = 23.00 cm3.g-1 KAtonsil = 20.00 cm3.g-1. From the experimental kinetic evaluations, based on a Langmuir-Freundlich model, the estimated kinetic adsorption constants for the clay and the Tonsil were kaAclay = 0.2488 ± 0.0913 kaAtonsil = 0.0839 ± 0.0219 respectively. The number of sites responsible for the pigments adsorption identified on the clay surface, were of the order of 183.90 x 1020 sites/g of clay. The acidified clay presented similar adsorptive properties to the imported product, showing that it may be employed to bleaching soy bean oil / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Este trabalho apresenta o desenvolvimento da tese intitulada: Estudo, em escala de laboratório, do uso de argilas do tipo Bofe na obtenção de argilas organofílicas e ativadas. Argilas do tipo esmectítico são as de maior utilização industrial, sendo considerada a mais interessante das argilas industriais. Todavia em diversos casos faz-se necessário submetê-las a tratamentos químicos para desenvolver suas potencialidades. Para o desenvolvimento da tese foram utilizadas quatro amostras de argilas do tipo Bofe, provenientes de jazidas localizadas no município de Boa Vista, PB. Esse tipo de argila, apesar de ser bastante abundante, possui baixo valor econômico dada a dificuldade de obter produtos com propriedades adequadas a partir delas. Neste estudo utilizamos dois tipos de tratamentos, para verificar a potencialidade destas argilas, que foram: ativação ácida e organofilização. Para ativação ácida, foi utilizado o ácido clorídrico com diferentes tempos de reação, variando de uma hora até sete dias e com estas amostras avaliou-se o poder descorante em óleo de soja. Para a organofilização foram utilizados três sais quaternários de amônio e com as argilas organofílicas obtidas realizou-se teste de sorção em solventes orgânicos. Os resultados obtidos indicam que o tratamento ácido em argilas, com tempos de reação muito longos, promove destruição significativa da estrutura do argilomineral esmectítico. As argilas na sua forma natural apresentaram, no descoramento de óleo de soja, comportamento superior ao de argilas industriais ativadas de alto desempenho o que potencializa o uso das argilas tipo Bofe como materiais descorantes naturais (terras fuller). Em relação à organofilização, observou-se a eficiência no tratamento aplicado, visto o aumento do espaçamento interplanar, medido por difração de raios-X e da alta capacidade de sorção de óleo Diesel e Tolueno dos materiais organofílicos obtidos. / This work present the development of the entitled thesis: Study, at laboratory scale, of the use of the Bofe type clay to obtain organophillic and activated clays. Clays of the smectite type are of the bigger industrial use, being considered most interesting of the clay minerals. However, becomes necessary to submit it to chemical treatments for develop its potentialities. For the development of the research four samples of clay from the Bofe type had been used, proceeding from deposits located in areas near to the city of Boa Vista, PB. This type of clays, in spite of they be quite abundant, possess low economic value because the difficulty to obtain products with adequate properties starting from them. In this study to verify the potentiality of these clays we used two types of treatments. Those treatments were: acid activation and organophillic modification. For the acid activation treatment, hydrochloric acid was used with different times of reaction, varying from one hour up to seven days and with the obtained samples the fade power was evaluated in soy oil. To the organophillic modification treatment three quaternary ammonium salts were used. With the samples of the treated clays were made sorption in organic solvents tests. The obtained results indicate that the acid treatment in clays, with very long times of reaction, promotes significant destruction of the structure of the smectite clay mineral. Clays in its natural form presented, in the soy oil fade, superior behavior to the one of industrial activated clays of high performance, that indicates the potential of use of the type Bofe clays as natural bleacher material (fuller\'s earth). In relation to the organophillic modification, it was observed efficiency in the applied treatment, seen the increase of the interplane spacing, measured by X ray diffraction and the high capacity of sorption of Diesel oil and Toluene of the gotten organophillic materials indicating its potential of use in the sorption of hydrocarbons.

Minerals and clay minerals in continental sedimentary successions are valuable tools for reconstructing past environmental conditions. Given the state of preservation of clays minerals, it is possible to identify how they were formed, providing clues about continental weathering conditions (inherited minerals) and geochemical conditions in the water column (neoformed or transformed). This study presents new mineralogical data from the Baskil section, a highly preserved middle Eocene succession in the Neo-Tethys (central Turkey). A gradual shift from a well-crystalline illite and chlorite interval (subsection I) to a detrital smectite dominant interval (subsection II) characterizes a change in source area from metamorphic to igneous rocks and changes from physical to chemical weathering conditions on land. This period coincides with the Middle Eocene Climatic Optimum (MECO), indicating a mineralogical signature of the event. Higher content of terrigenous input being deposited from 40.5 to 40 Ma caused a dilution effect of the carbonate materials as calcite and dolomite significantly decreases. Authigenic palygorskite showed an increasing trend from the middle to the uppermost portion of the section, indicating favorable conditions in the water column for its formation. We assume that conditions in the ocean circulation changed after 40 Ma, forming a stratified water column with warmer and saline conditions at greater depths, favoring palygorskite and possibly authigenic dolomite precipitation. The mineralogical evolution of the Baskil section reflects how sources and weathering regimes changed through time, and how these changes can be related to global (i.e. MECO) and/or local to regional processes. / Minerais e argilominerais em sucessões sedimentares são excelente ferramentas para a reconstrução de condições ambientais. Dado o estado de preservação dos argilominerais, é possível identificar como eles foram formados, fornecendo informação sobre as condições de intemperismo no continente e sobre condições geoquímicas na coluna d\'água. Este estudo apresenta novos dados mineralógicos da seção de Baskil, uma sucessão do Eoceno médio altamente preservada no Neo-Tethys (Turquia central). Uma mudança na assembléia mineralógica com maiores concentrações de ilita e clorita (subseção I) para um intervalo dominante de esmectita detrítica (subseção II) caracteriza uma mudança na área de fonte de rochas metamórficas para rochas ígneas e mudanças de condições de intemperismo físico para intemperismo químico. Este período coincide com o Ótimo Climático do Eoceno Médio (MECO), indicando uma assinatura mineralógica do evento. A paligorsquita autigênica teve um aumento na porção media e superior da seção, indicando condições favoráveis na coluna de água para a sua formação. Possívelmente as condições na circulação do oceano naquela região mudaram após 40 Ma, formando uma coluna de água estratificada com condições mais quentes e salinas em profundidades maiores, favorecendo precipitação de paligorsquita e dolomita. A evolução mineralógica da seção de Baskil reflete como as fontes e os regimes de intemperismo mudaram ao longo do tempo, e como essas mudanças podem estar relacionadas aos processos globais (e.g. MECO) e /ou a processos locais e regionais.

Minerals and clay minerals in continental sedimentary successions are valuable tools for reconstructing past environmental conditions. Given the state of preservation of clays minerals, it is possible to identify how they were formed, providing clues about continental weathering conditions (inherited minerals) and geochemical conditions in the water column (neoformed or transformed). This study presents new mineralogical data from the Baskil section, a highly preserved middle Eocene succession in the Neo-Tethys (central Turkey). A gradual shift from a well-crystalline illite and chlorite interval (subsection I) to a detrital smectite dominant interval (subsection II) characterizes a change in source area from metamorphic to igneous rocks and changes from physical to chemical weathering conditions on land. This period coincides with the Middle Eocene Climatic Optimum (MECO), indicating a mineralogical signature of the event. Higher content of terrigenous input being deposited from 40.5 to 40 Ma caused a dilution effect of the carbonate materials as calcite and dolomite significantly decreases. Authigenic palygorskite showed an increasing trend from the middle to the uppermost portion of the section, indicating favorable conditions in the water column for its formation. We assume that conditions in the ocean circulation changed after 40 Ma, forming a stratified water column with warmer and saline conditions at greater depths, favoring palygorskite and possibly authigenic dolomite precipitation. The mineralogical evolution of the Baskil section reflects how sources and weathering regimes changed through time, and how these changes can be related to global (i.e. MECO) and/or local to regional processes. / Minerais e argilominerais em sucessões sedimentares são excelente ferramentas para a reconstrução de condições ambientais. Dado o estado de preservação dos argilominerais, é possível identificar como eles foram formados, fornecendo informação sobre as condições de intemperismo no continente e sobre condições geoquímicas na coluna d\'água. Este estudo apresenta novos dados mineralógicos da seção de Baskil, uma sucessão do Eoceno médio altamente preservada no Neo-Tethys (Turquia central). Uma mudança na assembléia mineralógica com maiores concentrações de ilita e clorita (subseção I) para um intervalo dominante de esmectita detrítica (subseção II) caracteriza uma mudança na área de fonte de rochas metamórficas para rochas ígneas e mudanças de condições de intemperismo físico para intemperismo químico. Este período coincide com o Ótimo Climático do Eoceno Médio (MECO), indicando uma assinatura mineralógica do evento. A paligorsquita autigênica teve um aumento na porção media e superior da seção, indicando condições favoráveis na coluna de água para a sua formação. Possívelmente as condições na circulação do oceano naquela região mudaram após 40 Ma, formando uma coluna de água estratificada com condições mais quentes e salinas em profundidades maiores, favorecendo precipitação de paligorsquita e dolomita. A evolução mineralógica da seção de Baskil reflete como as fontes e os regimes de intemperismo mudaram ao longo do tempo, e como essas mudanças podem estar relacionadas aos processos globais (e.g. MECO) e /ou a processos locais e regionais.

The aim of the thesis has been to evaluate and understand the effect of caustic alkali solution of varying composition on the behaviour of expansive soil containing mixed layered minerals. Mixed layered minerals are formed of two or more kinds of inter grown layers, not physical mixtures. Illite - smectite is the most abundant and wide spread of the mixed layered clay minerals in sedimentary rocks and soils and also more common than either discrete illite or smectite. In geotechnical engineering much attention has not been paid to the behaviour of soils containing mixed layered minerals. Much less is known about the behaviour of these soils in polluted environment. Mixed layered minerals are more susceptible to environmental changes as the structural linkages between the layer minerals are weak compared to normal layered phyllosilicates. One important pollutant that can have considerable effect on the behaviour of soils is the caustic alkali contamination released from various industries. Recent studies have shown that the behaviour of even stable minerals is affected by alkali contamination. However, the effect of caustic alkali contamination on the behaviour of soils containing mixed layered minerals is not known and has been chosen for detailed study. Also to understand the mechanism of their interaction with alkali, it is necessary to study the effect of alkali solutions on the constituent clay minerals viz., montmorillonite and illite under similar conditions. To elucidate the mechanism of soil alkali interaction limited tests were conducted with simple electrolyte solution, as the alkali solution also acts as electrolyte apart from being alkaline. To confirm the mechanism of interaction, tests are also conducted on these soils with industrial spent liquor containing high caustic alkali and suspended alumina obtained from an alumina extraction plant treating bauxite with high alkali solutions at high temperatures. The results obtained in the laboratory are compared with the soil samples contaminated with leaking industrial Bayer's liquid in the field. Studies are also conducted to suggest remedial measures to control the adverse effects of alkali solutions on soil containing mixed layer minerals. The content of the thesis is broadly divide into 8 Chapters - viz., Introduction, Background and overview, Experimental program and procedures, Behaviour of soils containing mixed layer mineral illite - smectite (BCSI), Behaviour of montmorillonite and illite, Influence of Bayer's liquor and study on the field contaminated soils, Measures to control the influence of alkali contamination on BCSI and Summary and conclusions. The broad outline of these chapters is given in Chapter 1. A review of literature on the behaviour of soils containing different types of clay minerals with emphasis on mixed layer minerals has been presented in Chapter 2. The influence of different inorganic contaminants on the properties of soils in terms of their physical and chemical characteristics as well as their concentration has been summarized. The importance of changes in surface characteristics of soil particles and the changes in the thickness of diffuse double layer in altering the property of soils at low concentration of contaminants and changes in the mineralogy with high concentrated contaminants such as acids and alkalis has been highlighted. This forms the background information necessary to bring out the scope of the study. Four soils having different mineralogy have been used in this study. These soils are, black cotton soil containing predominantly mixed layer mineral illite - smectite mineral called rectorite, illite, montmorillonite (common smectite) and black cotton soil containing predominantly montmorillonite. The properties of the soils used are described in Chapter 3. Caustic alkali solutions of 1N, 4N concentration prepared in the laboratory and industrial alkali-spent liquor are used as contaminants. The spent Bayer's liquor had about 4N alkali concentration and 10% alumina in suspension. To simulate the effect of suspended alumina, two more caustic alkali solutions of 1N and 4N solutions containing 10% alumina by weight of solutions are also prepared. To isolate the effect of electrolyte solutions from that of alkali solution, two electrolyte solutions of 1N and 4N sodium chloride solutions are also used. Test procedures for conducting various tests such as pH, water adsorption characteristics, X-ray diffraction studies, SEM studies, thermal characteristics and geotechnical properties such as Atterberg limits, Oedometer tests and Shear Strength are given in this chapter. The test procedures are modified, wherever necessary, to bring out the effect of contaminants, particularly the effect of duration of interaction on the properties of soils. The source and properties of black cotton soil are presented in Chapter 4. Detailed x-diffraction studies have confirmed the presence of inter layered illite-smectite mineral viz., rectorite, which is uncommon in Indian expansive soils, and is classified as CH (Clay of high compressibility) as per ASTM soil classification. Effect of alkali and salt solutions of 1N and 4N concentration on all physico chemical and geotechnical properties are studied in this chapter. As it is known that presence of certain elements such as aluminium influence the soil alkali interaction, the effect of suspended alumina along with alkali solution has also been investigated. The effect of contaminating fluids such as 1N NaOH, 4N NaOH with and without alumina, 1N NaCl and 4N NaCl on the geotechnical properties of the soil has been studied. Mineralogical changes were observed by XRD and thermal studies in the soil treated with 4N NaOH solution and 4N NaOH + 10% alumina. The interlayer potassium of illite is released and potassium hydroxide is formed in soil treated with 4N NaOH. Swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH) has formed due to attack of 4N NaOH + 10% alumina on silica rather than on rectorite. Thus the studies clearly bring out that the rectorite present in the soil is dissociated only in the presence of strong alkali solutions of concentration of about 4N. The liquid limit of soil decreased with increase in the electrolyte concentration in the case of NaCl solutions. With 1N NaOH, the liquid limit of soil increased due to increase in the thickness of diffuse double layer due to increased pH. However, Proctor's maximum dry density increased and optimum moisture content decreased with 1N NaOH. With increase in the concentration of alkali solution to 4N, the rectorite dissociates into constituent minerals with the formation potassium hydroxide. The liquid limit of soil decreased probably due to the dominating influence of electrolyte nature of hydroxide solution over the effect of increased negative charge on clay particles due increase in the pH on the constituent minerals. Proctor's maximum dry density decreased and optimum moisture content increased with 4N NaOH. Sediment volume and oedometer free swell at seating/nominal surcharge load of 6.25 kPa of soil increased in 1N and 4N caustic alkali solutions, though by different mechanisms. The increase with 1N solution is essentially due to increased negative charges on clay mineral surface. However, the increase in swelling with 4N solution is associated with the dissociation of rectorite mineral and occurs in two distinct phases unlike in the case of 1N solution. While the first phase can be attributed to the effect of alkaline nature of the solution after reduction in its concentration due to reaction with rectorite and the consequent reduction in its electrolyte nature. The second phase is due to the swelling of the separated constituent minerals in the presence of excess of alkali and occurs after much delay. Consolidation behaviour of rectorite in 1N and 4N alkali solutions has been studied in two ways: 1). Loading without waiting for the second stage of swelling to occur, as in standard consolidation procedure and 2). Loading after completion of second stage of swelling which is occurring after considerable delay as explained earlier. Normally one would initiate loading after equilibrium is reached at the end of first stage of swelling and second stage of swelling is not suspected. As there is no second stage of swelling with 1N solutions, these two types of consolidation tests produced the same results. Abnormal rebound is observed during unloading with 4N solution in which loading cycle is initiated without waiting for second stage of swelling to complete. It is interesting to note that while the liquid limit of soil decreased with increase in the concentration of alkali solution, the swelling increased. The testing procedure and period of interaction as well as the concentration of alkali solution during the test in these two tests are different. The effects of alkali solution are more severe in case of liquid limit because of thorough mixing and consequent effective reaction during testing. Similarly, the volume changes in soil that has already reacted with 4N alkali solution when exposed to further to alkali contamination are considerably less compared to uncontaminated soil exposed to fresh contamination. The shear strength of soil treated with 4N-alkali solution has increased particularly after long period of interaction. This indicates that the soil after mineralogical changes posses good strength. Chapter 5 presents the effect of alkali and salt solutions on the physico chemical and geotechnical properties of component minerals of mixed layered illite/smectite. For this study, commercially obtained montmorillonite (bentonite), naturally occurring black soil containing montmorillonite and commercially pure illite are used. It was observed that montmorillonite alkali reactions would not produce significant mineralogical changes where as illite is dissociated into smectite with the formation of potassium silicate by the interaction of released potassium with soluble silica. This confirms that the ultimate products of rectorite with alkali solutions would be smectite and compounds of potassium. In the absence of mineralogical alterations the liquid limit of montmorillonite decreases due to suppression of diffuse double layer thickness due to dominating influence of alkali solutions on this highly active clay. However a small increase in liquid limit is observed in illite with alkali solutions. Thus the net effect of alkali on rectorite is to decrease the liquid limit with increase in alkali concentration. While the free swell and oedometer swelling of montmorillonite generally decreases with increase in the alkali concentration, they increase in illite. However, in both the minerals the swelling occurs only in one phase. Thus the second phase of swelling that has been observed in rectorite can be attributed to delayed swelling of montmorillonite that has been released by the attack of alkali on rectorite. The behaviour of black soil containing mixed layer mineral contaminated in the field and laboratory by leaking Bayer's spent liquor in an alumina extraction plant has been studied in Chapter 6. The Atterberg limits of the samples treated with liquor are reduced and sediment volume increased. Similarly the swelling at seating load in consolidation test is higher in sample compacted with water and inundated with liquor. X-ray diffraction studies showed that the mineralogical changes are similar to those occurred with 4N caustic alkali solution. The mineralogical and micro structural changes in the soil samples that are contaminated by leaked spent liquor in the field are relatively more marked. Also the behavior of highly montmorillonite clay, bentonite, has been studied contaminated with liquor in the laboratory. The study on the effect of high concentrated alkali solutions on montmorillonite can be useful to study the effect of interaction on the dissociated montmorillonite. These studies are helpful to suggest some possible remedial measures to control the adverse effect of alkali on soils. Possible Remedial schemes that can be adopted before and after contamination of the soil to control the adverse effect of alkali solutions on the black cotton soil containing mixed layered mineral are listed and their effectiveness examined in Chapter 7. The suggested remedial measures include flushing with water to dilute the effect of alkali, neutralisation with dilute hydrochloric acid, stabilisation of soil with lime and calcium chloride and use of impervious membrane to separate the foundation soil from alkali solution. The effectiveness of different measures as well as the method of their application has been described. Efforts are made to understand the mechanism of remedial action. Consolidation tests conducted on soil contaminated with 4N alkali solution and inundated with water showed increased swelling due to dilution of the alkali concentration. Though the swelling of contaminated soil can be controlled by passing dilute hydrochloric acid (1N), the method is not advocated as it can lead to ground water contamination. Mixing the soil with solutions containing up to 5% by weight of calcium compound in water could not prevent the alkali induced heave in the long run when inundated with 4N alkali solution. This was due to dissolution of silica by the strong alkali solutions and formation of swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH). The formation of sodium aluminates occurred only when the alkali solution contained alumina or soil contained calcium compounds. There are no significant variations in the effects of calcium chloride or calcium hydroxide on contaminated soil. Replacing the foundation soil with soil thoroughly contaminated with 4N alkali solutions and controlling the migration of contaminants into the foundation soil using high-density polyethylene (HDPE) geosynthetic membranes can be an effective measure to control the heaving in alkali contaminated foundation soil containing interstratified illite – smectite. Summary and the major conclusions of the thesis are presented in Chapter 8.

Manguezais são ecossistemas de transição entre ambientes continental e marinho. Estão amplamente distribuídos ao longo da costa brasileira, sob grande variabilidade de condições climáticas, oceanográficas, geológicas e geomorfológicas. A mineralogia dos solos reflete e interfere nos processos de formação de solos e no comportamento biogeoquímico de nutrientes e potenciais substâncias poluentes, orgânicas e inorgânicas. O presente estudo avaliou a composição mineralógica dos solos de oito manguezais, do litoral sul ao norte do país, por meio de DRX, infravermelho e MET, das frações finas (silte, argila total e argila fina). A assembléia mineralógica da fração argila é composta, predominantemente, por caulinita, esmectita, ilitas férricas e traços de quartzo e gibbsita. Na argila fina, observou-se a presença de grandes quantidades de caulinita e esmectitas, provavelmente férricas, associadas a algum mineral 2:1 HE além de ilita de baixa cristalinidade interestratificada com minerais expansivos. Dados de semi-quantificação e características cristalográficas de caulinitas e ilitas revelam que a geologia das áreas continentais adjacentes aos manguezais influencia diretamente a assembléia mineralógica dos solos desses ambientes. Sob esse olhar, três padrões de manguezais foram identificados ao longo da costa: manguezais influenciados diretamente por sedimentos derivados de solos desenvolvidos sobre materiais geológicos do escudo cristalino pré-cambriano, com caulinitas pouco cristalinas, ilitas originadas das micas presentes nas rochas correspondentes e esmectitas autigênicas; manguezais próximos a áreas dos tabuleiros terciários do grupo Barreiras, com caulinitas mais cristalinas e menores teores de minerais 2:1; e aqueles sob influência de materiais advindos do clima semi-árido nordestino (menos alterados), com grande quantidade de minerais 2:1 neoformados e herdados dos solos dessas áreas adjacentes, o que pode ser apoiado pelas maiores quantidades de ilitas, com cristalinidade menor. Estudos mais específicos acerca da composição química dos minerais e de seus mecanismos geoquímicos de formação devem ser realizados futuramente, para melhor entendimento dos processos propostos e sua relação com a dinâmica biogeoquímica de importantes elementos nesses ambientes, especialmente do Fe presente nos filossilicatos. / Mangroves are transitional ecosytems between continental and marine environments. Its widely distributed along Brazilian coast under great variability of climatic, oceanographic, geological and geomorphological conditions. Its soil mineralogy has a relevant role in the pedogenic processes and biogeochemical behavior of nutrients and potential inorganic and organic pollutants substances. The present study evaluated the mineralogical composition of fine fractions (silt, clay and fine clay) of eight Brazilian mangrove soils of south to north coast using XRD, infrared spectrometry and TEM analyses. The mineralogical assemblage of clay fraction consists on kaolinite, smectite, ferric illite and traces of quartz and gibbsite. In fine clay fraction it can be observed great amounts of kaolinite and smectites, probably ferric, associated with 2:1 hydroxy interlayered minerals beyond poorly crystalline illite-smectite interstratified minerals. Semi-quantification data and kaolinite/illite crystallographic characteristics reveal the importance of geological materials of continental adjacent areas for mineralogical composition of mangrove soils. Thus three different patterns were identified along the coast: mangrove influenced directly by sediments derived from soils developed on geological materials of Pre-Cambrian basement rocks, with poorly crystalline kaolinites, illite transformed from diagenetic mica present in Pre-Cambrian and authigenic smectites; mangroves next to Tertiary Barreiras Group sediments, with better crystalline kaolinites and less amounts of 2:1 phyllosilicates; and mangroves under influence of sediments that come from soils developed under northeastern semi-arid climate (less weathered), evidenced by great amounts of inherited and neoformed 2:1 phyllosilicates and poorly-crystalline illite. More specific studies about clay minerals chemical composition and its geochemical formation mechanisms should be performed in future, for better understanding of proposed processes and its relation with the biogeochemical dynamics of certain elements in this environment, specially the iron present in phyllosilicates.

O depósito de níquel laterítico de Niquelândia, GO, Brasil, é considerado um dos mais importantes depósitos desta natureza no país, em razão de sua dimensão, seus teores ligeiramente mais elevados e associação com argilominerais. Desde a década de 70, autores como Trescases e Santos já estudavam seus argilominerais detentores de níquel. Este depósito difere dos cubanos e australianos, pois os primeiros têm o níquel associado aos minérios oxidados e os segundos à serpentina. Em Niquelândia, o níquel está associado principalmente às esmectitas e vermiculitas. A existência destes argilominerais ricos em níquel torna o processo hidrometalúrgico aplicado em Niquelândia o menos recomendado, o que pode ser verificado através de perdas significativas de níquel no rejeito, principalmente no que se refere ao minério silicatado. Estas perdas estão relacionadas com a formação de silicatos de magnésio, como piroxênios, anfibólios e olivinas ainda durante o processo de moagem do minério, isto ocorre devido à técnica aplicada para a redução da umidade. A formação destes minerais retém o níquel em suas estruturas, não permitindo que este seja solubilizado na etapa de lixiviação amoniacal. Em Niquelândia, o principal portador de níquel é a esmectita, no entanto, são identificadas esmectitas di e trioctaédricas, quase sempre associadas. Estas variam desde um extremo trioctaédrico rico em níquel, praticamente refratário ao processo Caron, à esmectitas dioctaédricas de ferro, de baixos teores de níquel, mas com boa recuperação junto ao processo. Contudo, predominam no depósito esmectitas di e trioctaédricas de composições variadas de Fe-Mg-Ni, classificadas como montmorillonitas/stevensitas. Uma maneira de minimizar as perdas de recuperação de níquel seria exercer maior controle sobre a alimentação da usina, de forma a reduzir a proporção de minério silicatado do tipo esmectita trioctaédrica, aumentando a proporção de minério oxidado+minério silicatado de esmectitas dioctaédricas. / The nickel lateritic ore from Niquelândia Goiás - is one of the most important and well known Ni lateritic deposits in Brazil. High nickel contents, the deposit dimension and also, their associations with clay minerals are the main reasons for researchers, such as Trescases and Santos, to have studied it in the 1970s. The Cuban and Australian deposits have nickel associated to oxidized ores and serpentine, respectively, but at Niquelandia, nickel is specially associated to smectites and vermiculites. The Caron Process is not the most suitable for treating Ni-bearing clay minerals, as those present in Niquelândia. Consequently, there are many losses related to silicated ore. The reduction temperature used in the Caron process in the reduction step can form minerals, such as pyroxene, amphibole and olivine. These minerals trap Ni inside their structure; hence, the ammoniacal solution can not access this element and solubilize it. The main Ni-bearing clay mineral observed in Niquelândia is smectite. Actually, the silicated ore is composed by a mixture of smectites. One of them is a Ni-trioctahedral one, which is not affected by ammoniacal leaching; however, it has a significant amount of nickel. On the other hand, a dioctahedral Fe-rich smectite, has high Ni recoveries, but its nickel content is lower. Samples composed by a mixture of di and trioctahedrals smectites - Fe-Mg-Ni montmorillonite/stevensite are the most common. Considering all these factors, the losses related to Ni-recoveries can be avoided by a better feed control. The ideal feed should be an oxidized ore + silicate ore composed by dioctahedrals smectites. The Ni trioctahedral smectite should be avoided.