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.

Les smectites sont des matériaux envisagés pour le stockage des déchets radioactifs en tant que barrière ouvragée et encaissant géologique en raison de leurs propriétés physiques et chimiques particulières. Dans ce contexte, il est important de connaître leur comportement sous irradiations afin de pouvoir estimer la sûreté et la durabilité de l'ouvrage de stockage. Pour cette étude, deux montmorillonites ont été choisies. L'une des argiles provient de la province de Liaoning, en Chine (CHI) et présente la particularité de contenir des défauts d'irradiation stables. La seconde smectite (notée MX) a été extraite de la bentonite de référence méthodologique MX-80 et purifiée à l'aide de différentes techniques chimiques. La spectroscopie par Résonance Paramagnétique Électronique (RPE) a permis d'identifier plusieurs défauts d'irradiations qui se différencient par leur stabilité thermique et leurs caractéristiques RPE. Tous ces défauts peuvent être décrit comme des trous localisés sur une orbitale d'un oxygène lié à un silicium dans le feuillet argileux. Leur concentration augmente avec la dose jusqu'à atteindre une valeur de saturation, mais des différences sont observées entre les deux échantillons. La production de défauts ponctuels est également sensible au type de rayonnements et à la composition de l'espace interfoliaire (nature du cation compensateur, quantité d'eau interfoliaire). L'utilisation conjuguée de la RPE et de la spectroscopie Mössbauer a permis de mettre en évidence deux effets d'irradiation sur le fer structural. La montmorillonite MX purifiée est oxydée alors que la montmorillonite de Chine et la montmorillonite MX non déferrifiée sont réduites. Les irradiations modifient également l'environnement du fer structural. L'intensité du changement d'état d'oxydation dépend du type de rayonnement et de la nature du cation interfoliaire. En revanche, l'influence de l'eau interfoliaire semble être secondaire. Enfin, une variation de la Capacité d'Échange Cationique en fonction de la teneur en fer trivalent a été enregistrée. L'amorphisation de la montmorillonite MX a également été étudiée en fonction de la température. Elle dépend du rayonnement et de la nature du cation interfoliaire. Une dépendance de la dose maximale d'amorphisation en fonction de la masse du cation a été mise en évidence pour l'irradiation avec des ions Krypton.

Ce travail tente de caractériser les modifications structurales affectant les minéraux argileux lors de leur diagenèse d'enfouissement. Ces évolutions structurales ont été décrites dans la littérature comme résultant d'une transformation illite-smectite, par l'intermédiaire d'édifices interstratifiés dont la teneur en feuillets illitiques augmente avec la profondeur d'enfouissement. Historiquement, la diffraction des rayons a été l'outil privilégié pour mettre en évidence ces évolutions structurales du fait des modifications induites sur les profils de raies caractéristiques de ces interstratifiés. Afin de permettre une identification objective des interstratifiés, souvent présents en mélanges complexes de phases aux caractéristiques proches, une méthode de traitement numérique (décomposition) des diffractogrammes de rayons X a été développée afin d'en isoler les différentes contributions élémentaires. L'identification minéralogique est ensuite réalisée par comparaison des paramètres (position, largeur à mi-hauteur) déterminés pour chacune de ces contributions avec les valeurs obtenus sur des diffractogrammes calculés sur la base de modèles structuraux. Ces modèles intègrent la teneur en illite (smectite) des interstratifiés, l'état d'hydratation des smectites, la taille des domaines cohérents de diffraction, ainsi que des paramètres permettant de décrire l'ordre partiel ou la ségrégation. Cette méthodologie a enfin été appliquée sur des échantillons provenant de plusieurs puits forés dans le bassin de Paris et décrivant une section E-W, ainsi que sur des échantillons provenant des séries de référence du Gulf Coast. En s'appuyant sur l'analyse morphologique et chimique des particules argileuses de ces séries réalisée par Didier Champion, les résultats obtenus permettent de proposer des mécanismes réactionnels pour la transformation minéralogique observée. En particulier, la diminution de la teneur en smectite des interstratifiés correspond à la croissance de feuillets illitiques autour des particules pré-existantes par un processus analogue au mûrissement d'Ostwald. La chimie du pôle illite est fixe et présente une charge de ~0.9 par O10(OH)2.

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.

Les matériaux argileux présentent des propriétés favorables au confinement des radio-éléments pour le stockage des déchets nucléaires de haute activité thermogènes. Cette étude vise à déterminer les transformations induites par la contrainte thermique et l'impact sur les propriétés de confinement. Les échantillons ont été prélevés au niveau d'un analogue naturel de chauffage : une intrusion basaltique dans une argilite (Laumiere, Aveyron, France). Cet évènement volcanique s'est déroulé dans des conditions complexes hors d'atteinte en laboratoire. L'étude des interstratifiés illite-smectite (I-S), minéraux principaux de ces argilites, a montré une illitisation au contact de l'intrusion basaltique. La variation d'un indice de cristallinité des I-S est rendue complexe par un hydrothermalisme dans la fracturation. Laumiere a mis en évidence des paramètres déterminants (hétérogénéités sédimentaires, eau/roche ...) qui influencent l'évolution des matériaux argileux en contexte thermique. Mots clés : interstratifiés illite-smectite, illitisation, argilite, chauffage, analogue naturel

The focus of this study is on potential damages to buildings resulting from expansive soils in Tanzania, particularly clay soils in Kibaha. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the behaviour of soils and their interaction with structures has been of interest to the study in order to evaluate properly the source of the problem.The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area.Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples. To extend and amplify the findings, supplementary samples were collected from the environs of the two sites.The collected samples were submitted to soil laboratories at KTH, ARU, SEAMIC and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests. The results of this investigation indicate that soils in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell.Since swell pressure, free swell and swell percent are key properties of expansive soils, the swell properties were measured by free swell tests and one-dimensional oedometer swell tests. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa. The coefficient of linear extensibility (COLE) was determined for characterizing expansive clays. For all tested samples, COLE ranged from 0.09 to 0.14 indicating that soils fall in the region of high to very high expansion potential rating. The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of smectite in the soil. Furthermore, total suction measurement technique using filter paper method indicated that the soils have high suction values, signifying that they have a tendency to swell upon wetting depending on plasticity of particular soil.The depth of the active zone was measured as a function of moisture variations in the profiles during two extreme weather conditions. The active zone depth was found to be between 1.0 and 2.0 m deep. Procedures to assess models to predict swell in the case study were outlined together with their validity.Vertical and horizontal spatial variability in selected soil properties was defined using geostatistical techniques through the fitting of variogram. The indicator semivariograms of both clay contents and free swell gave a range of 20 m horizontally and 1.0 m vertically, with the horizontal variograms exhibiting greater ranges than the dipping variograms.Physical conditions of the surveyed properties in the area confirmed that building damages are associated with poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations was supplemented with prototypes of strip foundations whose performances were monitored over a period of four months. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil / QC 20100824

Expansive clay mineral contamination of road aggregate materials in Texas is a persistent problem. Hydrous layer silicate minerals - particularly smectites - in concretes are associated with decreased strength and durability in Portland cement and asphalt concretes. The Texas Department of Transportation (TXDOT) and Texas A&M Transportation Institute (TTI) evaluated the methylene blue adsorption test for its potential to identify and estimate quantities of expansive clays in aggregate stockpiles. Clay mineral quantification was completed for 27 geologically-diverse aggregate materials from Texas, Oklahoma, and Arkansas. X-ray diffraction analysis (XRD) of separated clays on glass was conducted, and NEWMOD was utilized to model the resulting diffraction patterns. Methylene blue adsorption (MBA) and cation exchange capacity (CEC) of clay fractions (< 2µm) and -40 mesh screenings (< 400 µm) were determined for most aggregates. Many of the aggregates exhibited significant quantities of expansive clay minerals such as smectite, which are linked to deleterious performance properties in concretes. While the majority of aggregates were derived from crushed limestone or calcareous river gravel parent materials, severalexhibited uncommon origins and unusual clay mineralogy. Due to the relatively low number of aggregates tested and diverse geological origins of the different aggregates,it proved difficult to formalize any conclusions abouttrendsbetweenthedifferent aggregate performance properties.

A better understanding of the brine-rock- supercritical CO2 interaction is needed to evaluate the risks of geologic CO2 sequestration. The geochemical effects of brine and supercritical CO2 were examined via laboratory modeling of in situ conditions on two reservoir caprocks in the Black Warrior River Basin, the Pottsville and Parkwood Formations. The clay fraction was extracted and treated at ~ 100 bar and 363 K (90 °C) over periods of up to 70 hours. Supercritical CO2 was introduced as dry ice in a pressurized vessel. Samples were observed using XRD, WD-XRF, AA, SEM, and EDS. Clay fractions contained Fe-chlorite, illite, kaolinite, and quartz. Results show the dissolution of illite, CO2-brine induced cation exchange ok K+, and the dissolution of silicate minerals. Steady-state K/Si ratios in the fluid suggest quartz re-precipitation. These interactions could adversely affect the long-term storativity of the caprock and point to a need for further study.

De par l'étendue de leur répartition géographique et la facilité de leur extraction, les molasses d'âge miocène du bassin rhodanien ont été largement exploitées par l'homme comme pierre de construction depuis le début de l'ère chrétienne. Le patrimoine bâti provençal érigé à l'aide de ce matériau, connu sous le nom de " Pierre du Midi ", et exposé aux intempéries depuis plus de cinq cents ans présente cependant un certain nombre de morphologies de dégradations. Parmi ces dégradations, la desquamation en plaques a la particularité de se développer en dehors des zones de remontées capillaires ainsi qu'en l'absence de sels solubles, de sollicitation mécanique, de pollution atmosphérique ou de colonisation biologique. Ce phénomène est donc induit par les propriétés intrinsèques du matériau et son comportement vis-à-vis des conditions environnementales. L'objectif de ce travail de recherche est d'établir le rôle joué par les minéraux argileux dans ce phénomène de dégradation spécifique. Une étude de terrain a pu mettre en exergue que le degré de desquamation en plaques observable sur des monuments de périodes de construction équivalentes est variable suivant l'origine des assises. A l'issue de cette reconnaissance, neuf échantillons représentatifs de la variabilité du degré de desquamation en plaques ont été prélevés en carrières. Une étude conventionnelle sur les caractéristiques pétrographiques et la composition minéralogique de ces types de " Pierre du Midi " a tout d'abord été conduite. Par la suite, une définition précise du cortège de minéraux argileux a été menée par le biais d'une approche méthodologique originale. Cette dernière combine la caractérisation cristallochimique au MET-EDS à la simulation des raies 00ℓ de diffraction des rayons X. Cette méthode a permis de déterminer les quantités de chacune des phases de phyllosilicate composant les différents cortèges. Le lien entre la quantité de feuillets de phyllosilicates expansifs et le degré de desquamation en plaques a pu, de ce fait, être mis en évidence. Après avoir déterminé les propriétés de stockage et de transfert des fluides des différents types de pierre, leur comportement hydromécanique a été évalué. L'ensemble de ces propriétés pétrophysiques a permis de mettre en relief la forte hétérogénéité du matériau à l'étude. Les indices de durabilité calculés à partir de ces résultats manquent cependant de pertinence quant à la prédiction du phénomène de desquamation en plaques. Après une analyse statistique (ACP) des données expérimentales, la meilleure interprétation suggère que ce phénomène soit déclenché par l'interaction entre les feuillets de phyllosilicates expansifs et les molécules d'eau. Cette interaction se manifeste par le comportement hydromécanique des pierres qui entraîne leur dégradation. Ce dernier est largement contrôlé par les propriétés physiques de stockage et de transfert des fluides qui conditionnent l'accommodation des déformations au niveau macroscopique.

Made available in DSpace on 2014-12-17T15:01:30Z (GMT). No. of bitstreams: 1 GeraldoMRF_TESE.pdf: 3870711 bytes, checksum: 6a5339896637d234e88f58bd692fe8cf (MD5) Previous issue date: 2012-09-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This study aimed to evaluate the potential use of smectite clays for color removal of textile effluents. The experiments were performed by testing exploratory/planning method factorial and fractional factorial where the factors and levels are predetermined. The smectite clays were used originating from gypsum hub of the region Araripe-PE, and the dye used was Reactive Yellow BF-4G 200%. The smectite clay was collected and transported to the Laboratory of Soil Physics of UFRPE, where it held its preparation through air drying, lump breaking and classification in sieve to then submit it to the adsorption process. Upon completion of 22 complete factorial design it was concluded that the values of (96, 96,5 and 95,8%) corresponding to the percentage of of removal for "in-kind", chemically and thermally activated, respectively and adsorbed amounts of (4,80, 4,61 and 4,74 mg/g) for three clays. Showed that the activation processes used did not increase the adsorption capacity of smectite clay. The kinetic data were best fitted to the Freundlich isotherm, with an exponential distribution of active sites and that shows above the Langmuir equation for adsorption of cations and anions by clays. The kinetic model that best adapted to the results was the pseudosecond order model. In the factorial design study 24-1, at concentrations up to 500 mg/L obtains high percentage of color removal (92,37, 90,92 and 93,40%) and adsorbed amount (230,94, 227,31 and 233,50 mg/g) for three clays. The kinetic data fitted well to Langmuir and Freundlich isotherms. The kinetic model that best adapted to the results was the pseudosecond order model / Este trabalho teve como objetivo avaliar o potencial de utiliza??o das argilas esmectitas, para remo??o de cor de efluentes t?xteis. Os experimentos foram realizados atrav?s de ensaios explorat?rios/m?todo de planejamento fatorial e fatorial fracion?rio, em que os fatores e os n?veis s?o pr?-determinados. As argilas esmectitas usadas foram origin?rias do p?lo gesseiro da regi?o do Araripe-PE, e o corante utilizado foi o Amarelo Reativo BF-4G 200%. A argila esmectita foi coletada e transportada para o Laborat?rio de F?sica de Solos da UFRPE, onde se realizou a sua prepara??o atrav?s de secagem ao ar, destorroamento e classifica??o em peneiras para, em seguida, submet?-la ao processo de adsor??o. A partir da realiza??o do planejamento fatorial 22 concluiu-se que os valores de 96, 96,5 e 95,8%, correspondentes aos percentuais de remo??o para as argilas esmectitas innatura , quimicamente e termicamente ativadas, respectivamente, e com quantidades adsorvidas de 4,80, 4,61 e 4,74 mg/g, para as tr?s argilas, mostraram que os processos de ativa??o utilizados n?o aumentaram o poder de adsor??o da argila esmectita. Os dados cin?ticos ajustaram-se melhor ? isoterma de Freundlich, com uma distribui??o exponencial de s?tios ativos e que se mostra superior ? equa??o de Langmuir para adsor??o de c?tions e ?nions pelas argilas. O modelo cin?tico que melhor se adequou aos resultados foi o modelo pseudo-segunda ordem. No estudo do planejamento fatorial 24-1, em concentra??es de at? 500 mg/L se obt?m elevados percentuais de remo??o de cor (92,37, 90,92 e 93,40 %) e quantidade adsorvida (230,94, 227,31 e 233,50 mg/g) para as tr?s argilas. Os dados cin?ticos ajustaram-se bem ?s isotermas de Langmuir e Freundlich. O modelo cin?tico que melhor se adequou aos resultados foi o modelo pseudo-segunda ordem