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1
Ouyang, Shoung. "Sealing performance assessments of bentonite and bentonite/crushed rock plugs". Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185275.
Testo completoAbstract (sommario):
Bentonite and mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. The materials have been used to form cap layers to reduce infiltration for mined waste tailings and can also be used to construct clay liners for municipal as well as industrial waste managements. This study includes a systematic investigation of the sealing performance of bentonite and bentonite/crushed rock plugs under diverse conditions. American Colloid C/S granular bentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no negative effects on the sealing performance within the test range from room temperature to 60°C. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for the plug design. A permeability model developed is useful for the prediction of permeability in clays, especially in view of the difficulties in obtaining such a property experimentally. A piping model is derived based on the plastic flow theory. This piping model permits the estimation of critical hydraulic gradient allowed before the flow of bentonite takes place. It can also be used to define the maximum allowable pore diameter of a protective filter layer.
2
ANDRADE, Daniela de Lourdes Anjos Coutinho Simões. "Influência das variáveis de processo na formação e propriedades de nanocompósitos polipropileno/bentonita". Universidade Federal de Campina Grande, 2009. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1691.
Testo completoAbstract (sommario):
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DANIELA DE LOURDES ANJOS COUTINHO SIMÕES ANDRADE - TESE (PPGEP) 2009.pdf: 2248344 bytes, checksum: 28a93ae4236853f59fe35037c2ab6f28 (MD5)Made available in DSpace on 2018-09-12T12:56:27Z (GMT). No. of bitstreams: 1 DANIELA DE LOURDES ANJOS COUTINHO SIMÕES ANDRADE - TESE (PPGEP) 2009.pdf: 2248344 bytes, checksum: 28a93ae4236853f59fe35037c2ab6f28 (MD5) Previous issue date: 2009
A proposta deste trabalho foi preparar nanocompósitos de polipropileno/compatibilizante/bentonita, pelo método de intercalação na fusão, utilizando como carga uma argila sódica comercial Argel, fornecida por uma indústria local, purificada e modificada organicamente com um sal quaternário de amônio empregando diferentes métodos de preparação. Ao longo do trabalho foram utilizadas duas matrizes e dois tipos de compatibilizantes: PP H103, PP H401, Polipropileno modificado com anidrido maleico (PP-g-MA) e Copolímero de etileno e álcool vinílico (EVOH), respectivamente. As argilas foram caracterizadas por difração de raios-X (DRX), espectroscopia de infravermelho (FTIR) e análise termogravimétrica (TG) visando determinar o método de preparação mais eficiente para obtenção das argilas organofílicas. Uma vez determinado o melhor procedimento para organofilização, na segunda parte deste estudo, avaliou-se o efeito do tipo e teor de argila organofílica, bem como o tipo e teor de compatibilizante nas propriedades de filmes de polipropileno. De acordo com os resultados preliminares deste estudo, há uma indicação de que os filmes de nanocompósitos PP/PP-g-MA/argila organofílica, contendo 1% de argila organofílica e 15% de polipropileno modificado com anidrido maléico (PP-g-MA) podem ser promissores para o mercado de embalagens e poderão em um futuro próximo serem usados como um novo produto por empresas nacionais.
The purpose of this work is to prepare nanocomposites of polypropylene/compatibilizer/bentonite, by melting intercalation, with a commercial sodium clay – Argel – as filler. This clay was organically purified and modified by different methods, with a quaternary ammonium salt. The clays were characterized by X-Ray diffraction (XRD), infrared spectroscopy (FTIR) and thermogravimetric analyses (TG) to determine the most efficient preparation method. Before that, in the second stage of this study, the influence of the type and contend of organoclay in the properties of the polypropylene films was measured; the same was done for the compatibilizer. The preliminary results indicate that the nanocomposites film with 1% of organoclay and 15% of polypropylene grafted with maleic anhydride show promise as packing materials and may be used, in the near future, as a new product by the national industry.
3
Ju, Shuohui. "Electroosmotic dewatering of bentonite suspensions". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59868.
Testo completoAbstract (sommario):
Electroosmotic dewatering of Bentonite suspensions under conditions of constant DC voltage and constant DC current was investigated experimentally in a column 5 cm in diameter. The suspensions were prepared with CaCl$ sb2$ in distilled water with concentrations up to 1 M. The initial solid content was between 9.1 wt% and 26 wt% and the initial bed height ranged from 1.0 cm to 5.2 cm. Constant voltages from 4.0 V to 8.0 V and constant currents from 90 mA to 110 mA were used.Electroosmosis removed 20-60% of the water with energy expenditures well below the energy required to vaporize the water. Higher voltages or currents removed more water. Removal rates were increased by the addition of CaCl$ sb2$. The lowest bed height (1 cm) gave the lowest energy of dewatering, but the final water removal was low. For constant voltage experiments with an initial field strength of 2.8 V/cm, bed heights around 2 cm gave the highest water removal. The initial solid content had little effect on the final solid content. The Helmholtz/Smoluchowski theory did not predict correctly the effects of electrolyte concentration, solid content and bed height on the rate of electroosmotic dewatering.
4
Howarth, Leslie George. "Rheological studies of bentonite dispersions". Thesis, University of Bristol, 1986. http://hdl.handle.net/1983/8cd3b134-1a67-40b0-a779-70559df77948.
Testo completo
5
Magalhães, Vladmir Alvim Vieira. "Bentonita sódica com propriedade antibacteriana para inibição de biocorrosão em poços tubulares profundos /". Araraquara, 2016. http://hdl.handle.net/11449/141943.
Testo completoAbstract (sommario):
Orientador: Rodrigo Fernando Costa MarquesBanca: Miguel Jafelicci Junior
Banca: Wilton Rogério Lustri
Resumo: O presente trabalho consiste na funcionalização do fluido de perfuração conhecido como bentonita (BN) com grupos funcionais sulfidril (SH) provenientes do reagente 3- mercaptopropil-trimetoxissilano (MPTS) e nanopartículas de prata (NPs/Ag), visando a inibição da biocorrosão por oxidação de bactérias. Para tanto, a argila do tipo bentonita, constituída principalmente do argilomineral montmorilonita, foi modificada através de rota de inserção de organossilano e nanopartículas de prata (NPs/Ag) em sua estrutura, sendo um processo favorecido pelo efeito redutor do grupo tiol, proveniente do silano. As amostras funcionalizadas em concentrações distintas de Ag foram testadas contra a ação da ferrobactéria do tipo Thiobacillus ferrooxidans. Para testar o efeito antibacteriano do material híbrido, utilizou-se metodologia em meio de cultura T&K, onde foi possível medir a capacidade de inibição da oxidação de Fe2+ a Fe3+ por unidade de tempo. O processo de modificação proposto permitiu a manutenção da estrutura original da bentonita, bem como a criação de nanopartículas de prata, cujo efeito antibacteriano inibiu a biocorrosão de Fe2+ obtendo, desta forma, fluido de perfuração funcionalizado com grande potencial de aplicação em obras de perfuração de poços tubulares profundos.
Abstract: This work proposes the functionalization of the drilling fluid known as bentonite (BN) with sulfhydryl functional groups (SH) from the reagent 3-mercaptopropyltrimethoxysilane (MPTS) and silver nanoparticles (Ag/NPs), to inhibit corrosion by bacteria that oxidize metal. Therefore, the type clay bentonite, consisting mainly of montmorillonite clay mineral, was modified through organosilane insertion route and silver nanoparticles in its structure, because this is a process favored by the reducing effect of the thiol group from the silane. Samples functionalized in different concentrations of Ag were tested against the action of ferrobactéria type Thiobacillus ferrooxidans. To test the antibacterial effect of the hybrid material, was used T&K methodology, where it was possible to measure the capacity to inhibit the oxidation of Fe2+ to Fe3+ per unit time. The planned modification process, permitted the maintenance the original structure of the bentonite, as well as the creation of silver nanoparticles, that due to the antibacterial effect, has inhibited biocorrosion of Fe2+, obtained in this way, a drilling fluid functionalized with great potential for application in drilling works of deep wells.
Mestre
6
Hume, Harold B. "Gas breakthrough in compacted Avonlea bentonite". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ35063.pdf.
Testo completo
7
Mollins, Lee Hamilton. "The design of bentonite-sand mixtures". Thesis, University of Leeds, 1996. http://etheses.whiterose.ac.uk/4122/.
Testo completoAbstract (sommario):
One-dimensional and isotropic swelling tests, hydraulic conductivity tests and triaxial compression tests have been performed at applied stresses up to 450kPa on sodium bentonite powder, sand and compacted sodium bentonite-sand mixtures (5, 10, and 20% bentonite by dry weight). This was done to investigate the use of bentonite improved soils for waste containment, and study the fundamental geotechnical properties of bentonite-sand mixtures using a classical soil mechanics approach. It was found that air dried bentonite powder swells to reach a state described by a single straight line on a plot of void ratio against the logarithm of vertical effective stress, regardless of preparation technique. The gradient of this line was intermediate between a normal consolidation and rebound line for the same material indicating a different sample fabric when allowed to reach equilibrium from an initially dry state rather than the conventional fully saturated state. Swelling of bentonite-sand mixtures expressed in terms of the clay void ratio show a deviation from bentonite behaviour above a threshold stress which depends on the bentonite content. From this behaviour, a modified principle of effective stress has been proposed. Similar swelling relationships were found for samples under an isotropic confining stress. Hydraulic conductivity data for bentonite and mixtures indicate an approximately linear relationship between the logarithm of hydraulic conductivity and the logarithm of void ratio. Observed differences in hydraulic conductivity between bentonite and mixtures, when represented in terms of the clay void ratio, are attributed to the sand porosity and tortuosity. From a stress-dilatancy analysis of triaxial data, the peak strength of mixtures has been shown to depend on the sand relative density. This parameter indicates how the material will behave during shear. A threshold sand relative density has been postulated, which is dependent on the axial strain. Below the threshold value, it is likely that the stress-strain behaviour will be characteristic of the bentonite alone. A design model based on the clay void ratio, sand porosity and tortuosity, and sand relative density is presented, enabling the hydraulic conductivity or strength of a mixture to be estimated.
8
Visudmedanukul, Punlop. "Solute Transport Through Cement-Bentonite Barriers". 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/123466.
Testo completo
9
Sherriff, Nicholas Kevin. "Radionuclide dissociation from bentonite colloid systems". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/radionuclide-dissociation-from-bentonite-colloid-systems(43918efc-26e4-4e41-a450-3e209c20340d).html.
Testo completoAbstract (sommario):
Deep geological disposal is a method of managing high level, long-‐lived nuclear waste. It is a concept that many countries are exploring for the possibility of managing nuclear waste generated from power production. For deep geological disposal to be viable then areas where problems may surface have to be explored. Bentonite clay has been proposed as the material to be used for the backfill of the repositories. Its swelling properties ensure that it will expand to plug the bore holes that will be made for the waste, its impermeable nature restricts contact between groundwater and the waste package and its stability on a geological timescale all make it desirable as a backfill material. This project looks at the role that colloids formed from the bentonite clay could have in facilitating radionuclide transport away from a nuclear waste repository. Several radionuclides (Eu(III), U(VI), Th(IV) and Am(III)) have been considered in this research, and information from these studies will be used in the BELBaR project’s outputs, which will eventually support a disposal safety case. Ternary systems of 152Eu(III), bulk bentonite and EDTA ([Eu] = 7.9 x 10-‐10 M; pH = 6.0 – 7.0) have been studied. Without EDTA, there was slow uptake in a two-‐stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a smaller fraction (3.0 % over a period of 1 month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1 – 322 days. EDTA was added to the pre-‐equilibrated Eu bentonite systems at 0.01 M. A dissociation rate constant of approximately 4.3 x 10-‐8 s-‐1 (values in the range 2.2 x 10-‐8 – 1.0 x 10-‐7 s-‐1) for pre-‐equilibration times ≥ 7 days was measured. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was also present prior to contact (4.5 % ± 0.6). Eu interactions with colloidal bentonite were studied, and the dissociation rate constant measured by a resin competition method. A dissociation rate of 8.8 x 10-‐7 s-‐1 and a range of 7.7 x 10-‐7 – 9.5 x 10-‐7 s-‐1 were measured. For both bulk and colloidal bentonite slow dissociation was observed for Eu(III), but there was no evidence for ‘irreversible’ binding. The interactions of 232U(VI) with bentonite colloids ([U] = 5.43 x 10-‐10 M; pH = 8.8 ± 0.2) have been studied using a resin ion exchange competition technique. The reversibility of the interaction was studied by allowing U(VI) to sorb to bentonite colloids for periods from 1 – 35 days. A fraction of the U(VI) was removed from the solution instantaneously (28-‐50 %), and after 3 days, the amount of U(VI) remaining on the bentonite colloids was 17-‐ 25%. With time, the amount of U(VI) retained by the bentonite colloid is reduced further, with a first order dissociation rate constant of 5.6 x 10-‐7 s-‐1. Whilst the dissociating fraction was small (24% (+34; -‐12 %)), complete dissociation was not observed. Although slow dissociation was observed for U(VI), there was no convincing evidence for ‘irreversible binding’ of the radionuclide by the colloid. The interactions of 228Th(IV) ([Th] = 3.79 x 10-‐12 M; pH = 8.8 ± 0.2) and 241Am(III) ([Am] = 3.27 x 10-‐9 M; pH = 8.8 ± 0.2), with bentonite colloids have been studied using an ion exchange competition technique. Th(IV) was not fully associated with the bentonite colloids, and filtration showed that the uptake after 1 week was 78.3% (± 2.7%). Am(III) was weakly associated to the bentonite colloids, the uptake after 1 week was 20.1 % (± 5.2 %). Cellulose phosphate was added to the radionuclide/bentonite colloid systems (1 g for Th(IV), 0.2 g for Am(III)), an amount that was sufficient to retain the radionuclide when no bentonite colloids are present. A fraction of the Th(IV) is initially removed by the Cellphos (75-‐93 %), and after 7 days the amount of Th(IV) remaining on the colloids is 1 -‐ 3 %. Over the time of the experiment, the amount of Th(IV) retained by the bentonite colloid appears to remain level and the amount bound to the bentonite colloid at the end of the experiment is 2.1 % ± 0.88 % which is within experimental error of the steady state equilibrium of the system. A fraction (48-‐94 %) of the Am(III) is also initially removed by the Cellphos, after 7 days the8amount of Am(III) remaining on the colloids is 1.2 – 9.3 %. However, after 35 days of contact time with the cellulose phosphate it appears that Am(III) is released back into the system, preventing dissociation rates from being calculated in this case. Studies of the association of Eu(III) to the clay colloids and its subsequent dissociation in this thesis follow similar trends to those described elsewhere in the literature (Missana et al. (2008), Bouby et al. (2011)). The Eu/bentonite colloid dissociation rate calculated here (8.8 x 10-‐7 s-‐1 (± 9.1 x 10-‐7 s-‐1)) is within error of the dissociation rates for trivalent ions estimated by Wold (2010) (Am(III) 5.6 x 10-‐7 s-‐1 Cm(III) 1.7 x 10-‐6 s-‐1). The U(VI) studies in this thesis show a dissociation rate of 5.6 x 10-‐7 s-‐1 (± 4.2 × 10-‐7) which is within error of the U(VI) dissociation rate estimated by Wold (2010) (8.3 X 10-‐7 s-‐1). Reliable dissociation rates could not be obtained from the Am(III) and the Th(IV) studies in this thesis, other studies (e.g. Bouby et al. (2011) showed signs of irreversible binding of Th(IV) to bentonite colloids, however, no irreversible binding was observed in this thesis. Am(III) did not appear to be a close analogue of Eu(III) in these systems. All of the isotopes studied in this thesis showed no evidence of irreversible binding to bentonite or bentonite colloids. As such, the role that bentonite colloids will have in the facilitated transport of radioisotopes away from a repository is likely to have only a limited impact, at most, on the environmental safety case.
10
Schenning, Jessica A. "Hydraulic performance of polymer modified bentonite". [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000403.
Testo completo
11
Machado, Gabriel Gonzalo. "Variação espacial da carga interfoliar de esmectitas do depósto de bentonita de melo (norte do Uruguai): implicações nas propriedades físicas e na organofilização". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/75924.
Testo completoAbstract (sommario):
Para a modelização da distribuição espacial da carga interfoliar das esmectitas de Melo foram amostrados quatro perfis, sendo dois obtidos a partir de furos de sondagens e dois com amostras coletadas na frente da cava de exploração da ocorrência. Os perfis formam aproximadamente uma figura com a forma de um trapezoide isósceles possuindo uma mediana em torno de 100 m. Foi analisado um total de 21 amostras a partir dos perfis. A camada de bentonita na área estudada varia de 5 a 6 metros de espessura e no perfil localiza-se entre a camada de solo do topo e uma camada sotoposta de arenito de granulação media a grossa. A composição mineralógica observada em rocha total ao XRD mostra um aumento do conteúdo de esmectita com a profundidade, estimando-se uma proporção de 30% a 50% na profundidade de 1,5m e de 90 a 96% na profundidade de 7 a 8,3 m, variando muito pouco de um perfil em relação a outro, porém, mantendo a tendência de aumento da esmectita em profundidade. Identifica-se montmorilonitas dioctaedricas magnesianas com predomínio de Ca na posição trocável, seguido de quartzo, feldspatos (albita e K-felçdspato) e raramente identifica-se traços de ilita e zeolitas (heulandita-clinoptilolita). A composição química por XRF também é coerente com a tendência observada na mineralogia, com uma diminuição em profundidade do teor de SiO2, K2O, Na2O indicativo de menos quartzo e feldspato e um aumento do MgO oriundo das substituições octaédricas da esmectita que também é responsável pela origem da carga interfoliar, Al2O3 da posição octaédrica das esmectitas, Fe2O3 supostamente octaédrico e CaO que entra no sistema para compensar o desequilíbrio elétrico das cargas. A carga interfoliar foi estimada na fração <1 μm por dois métodos sendo que a distribuição espacial mostra uma tendência de aumentar na parte intermediária da camada com valores em torno de 0,56 e/huc, diminuindo em direção ao topo e em profundidade com valores variando entre 0,46 a 0,48 e/huc. Esta variação gradual é melhor observada nos difratogramas do que através do método de cálculo da carga interfoliar, que não possuem sensibilidade suficiente para identificar as pequenas variações. Entretanto, variações na posição e na forma do pico 001 da esmectita são evidencias significativas que permitem validar as conclusões. O cálculo da formula unitária da montmorilonita mostra uma carga interfoliar de origem octaédrica com uma distribuição heterogenia ao longo do perfil reforçada pela variação na sorção organofílica e no grau de expansão observado na montmorilonita. A avaliação da capacidade de troca de cátions (CEC) utilizada no projeto foi validada com o método do acetado de amônio, sendo que os valores obtidos foram diretamente proporcionais a estimativa da carga interfoliar das amostras. Valores de CEC entre 110 moles/100gr de argila corresponde a uma carga interfoliar da ordem de 0,55 e/huc e valores em torno de 90 moles/100gr de argila correspondem a cargas interfoliares em torno de 0,46 e/huc. A quantidade de cloreto de dodecylammonium (C12H28CIN) utilisado para organofilização foi proporcional a media do CEC. Em relação às propriedades físicas e organofilização, os padrões dos difratogramas das argilas organofilicas mostraram uma tendência de expansibilidade em função da carga interfoliar e a posição do pico 001 da montmorilonita-(C12H28CIN) que variou de 17,05Å a 17,68Å. Pode-se considerar como um complexo bicamadas organo argilas, classicamente esperadas a 17,46Å considerando o tamanho da cadeia alkyl utilizada e a isoterma de sorção conhecida. As pequenas variações são indicativas da presença de camadas não intercaladas devido a heterogeneidade da carga. Embora as pequenas diferenças no espaçamento “d” entre as amostras, a relação da 001 argila organofilica do perfil em função da carga interfoliar, apresentou uma correlação perfeita. Comparando no perfil, o espaçamento 001 da argila orgânica tende a aumentar com a carga intefoliar. A posição do pico 001 varia entre 17,15Å e 17,5Å e a área do pico 001 após a organofilização variou entre 2620,6 (cps x deg) até 418,8 (cps x deg). A tendência observada para a distribuição espacial da carga interfoliar esta provavelmente relacionada com uma variação gradual da permeabilidade e da razão água/rocha durante a alteração. A zona media da camada que concentra os mais elevados valores de carga interfoliar mostrou frequentemente a presença de uma textura esferulítica. Também, traços de zeolitas no XRD foram encontrados somente em amostras da profundidade entre 4 e 6 metros, indicando que a razão água/rocha estava no limiar do campo de estabilidade onde as zeolitas são favorecidas em detrimento das esmectitas no processo alteração do vidro vulcânico.To model the spatial distribution of key smectite properties, four profiles were sampled, two coming from boreholes and 2 from fresh cut samples over the mining front, Forming roughly an Isosceles Trapezoid with a median of approximately 100 m; 21 samples were analyzed over the four profiles. Bentonite bed ranges in the studied area from 5 to 6 m thick underlying top soil layer and overlaying a gross grain sandstone layer. Mineralogical composition observed on whole rock XRD traces showed an increasing content of the smectitic phase as a function of depth, going from 30% to 50% at around 1,5 m depth to 90 to 96 % at a depth ranging 7 to 8,3 m depth, varying very slightly from one profile to another but keeping the trend. Mayor mineral phases identified were Mg rich dioctahedral montmorillonite with mainly Ca in exchangeable position, Quartz, feldspar (Albite and K-feldspar) and only occasionally as trace phases we observed Illite and Zeolites (heulandite-clinoptilolite). XRF chemical analysis results are also coherent with this vertical tendencies, expressed in a notable decrease of a SiO2, K2O, Na2O indicating less quartz and feldspar species; and with increasing of MgO as octahedral substitution representing the main source of layer charge, Al2O3 most octahedral but also in a rather small amount as tetrahedral substitutions, Fe2O3 presumably octahedral and CaO compensating electrical charge desequilibrium. Layer charge was estimated on the <1 μm size fraction by two methods and spatial distribution shows a clear trend to increase at the middle of the bed up to values around 0,56 e/huc and decrease towards top and bottom over values ranging from 0.46 to 0,48 e/huc. This gradual variations can be better observed on the XRD patters than by actual layer charge calculation methods results, given the fact that for this slight variances, commonly used methods are not sensible enough, Nevertheless the 001 peak position and shape of the smectite phase represents sufficient evidence for conclusions. Layer charge distribution is mainly Octahedral derived from unit formula calculations and Layer charge is clearly heterogeneous due to Organophilic sorption and swelling behavior observed. Cation exchange capacity was calculated by ammonium acetate method, values obtained are directly proportional to layer charge estimations over those samples. CEC values around 110 moles/100gr of clay correspond to Layer charge on the order of 0,55 e/huc and values around 90 moles/100gr of clay to layer charges around 0,46 e/huc. The amount of dodecylammonium Chloride (C12H28CIN) used for organophilization was established proportional to the CEC average. Regarding the implications on physical properties and organophilization, XRD patterns of Organophilic clays showed a tendency on expandability as a function of layer charge in terms of their 001 (C12H28CIN)-Montmorillonite peak position, ranging from 17,05 Å To 17,68 Å. They could all be considered as bilayer intercalated Organoclay complexes, classically expected at 17,46 Å according size of the alkyl chain used, and the known sorption isotherm. The slight variances are indicating the presence of non-intercalated sheets due to charge heterogeneity. Despite the slight d-spacing differences among samples, the relationship 001 Organophilic C profile as a function of layer charge has a perfect correlation. Comparing a single profile, 001 d-spacing of organoclays tends to increase with increasing layer charge. The position of the 001 peak ranges between 17.15 Å and 17.5 Å and the raw 001 peak area after organophilization can vary from 2620.6(cps x deg) to 418.8 (cps x deg). The tendencies observed for layer charge spatial distribution are probably related to gradual variations of permeability and water/rock ratio during alteration, the middle zone of the bed that concentrates higher values of layer charge also has showed very frequent presence of spherulitic textures that may belonged originally of opal-CT but replaced by recrystallized quartz unlike top and bottom of the bed, also Zeolites XRD traces were only found in samples located from 4 to 6 m depth, indicating that water rock ratio close to the threshold where Zeolites are favored with respect to smectites as a product of alteration.
12
Nocon, Melody Schwartz. "Inorganic Sorption in Polymer Modified Bentonite Clays". Scholar Commons, 2006. http://scholarcommons.usf.edu/etd/3850.
Testo completoAbstract (sommario):
In 1986, geosynthetic clay liners (GCLs) were invented and successfully used as a replacement for the soil layer in composite lining systems. In some applications an additive (polymer) is mixed with the bentonite to increase performance, especially in those that have low concentrations of sodium bentonite (EPA 2001).Studies showing significant increases in hydraulic conductivity values for bentonite in the presence of high salt concentrations are frequently documented and there is a risk of early breakthrough due to performance failure of the GCL clay component. (Ashmawy et al, 2002). It has also been stated that sodium, potassium, calcium, and magnesium have such a high affinity for the clay's surface other chemical species have little chance of attenuation (EPA 2001).
For these reasons, researching sorption in the presence of major salt cations and polymers gains great importance.Distribution coefficients were extrapolated from Linear, Freundlich and Langmuir sorption isotherms for sodium and calcium cations modeled from data collected from batch tests of sodium bentonite and various manufactured and custom mixed polymer modified bentonites. Surface characterization before and after calcium or sodium solution exposure of all tested media was accomplished by use of scanning electron microscopy and energy dispersive x-ray analysis.
13
Wilson, James Charles. "The effect of iron on bentonite stability". Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274751.
Testo completo
14
Stepova, K. V., e A. Z. Kontsur. "LEAD ADSORPTION FROM WASTEWASTER BY MODIFIED BENTONITE". Thesis, Львівський національний університет ім. І.Франка, 2019. http://hdl.handle.net/123456789/6235.
Testo completo
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Baxter, Diane Yamane. "Mechanical Behavior of Soil-Bentonite Cutoff Walls". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27079.
Testo completoAbstract (sommario):
A soil-bentonite cutoff wall is a type of subsurface vertical barrier constructed by back-filling a trench with a mixture of soil, bentonite, and water. Although soil-bentonite cutoff walls are common, their mechanical behavior is not well understood. Current design procedures do not consider the final stress state of the consolidated soil-bentonite backfill or deformations in adjacent ground. The final stress state in the completed wall is important because it influences the hydraulic conductivity of the cutoff (Barrier 1995), the cutoff's susceptibility to hydraulic fracture, and the magnitude of deformations adjacent to the cutoff wall. Deformations adjacent to the cutoff wall can be significant and can cause damage to adjacent structures. The objectives of this research are to 1) add to the current body of knowledge of the properties of soil-bentonite mixtures, 2) evaluate constitutive models and select a model to represent soil-bentonite, 3) model a soil-bentonite cutoff wall using finite elements, and 4) investigate the influence of several factors on the deformations in adjacent ground.
These objectives were met by first summarizing information from the literature on soil-bentonite properties and then performing a laboratory testing program on different soil-bentonite mixtures. Five constitutive models were evaluated to determine how well they match the data from the laboratory testing program. A model referred to as the RS model was chosen to best represent soil-bentonite, and provided a good match of the soil-bentonite behavior. The RS model, which is a special case of a more complicated existing model, is a non-associative Modified Cam Clay type model that has parameters to change the yield surface and plastic potential surface into ellipses of varying shapes. The RS model was implemented into the finite element program SAGE.
A finite element model was developed using SAGE to simulate all stages of construction of a soil-bentonite cutoff wall including excavation of a trench under bentonite-water slurry, replacement of the bentonite-water slurry with soil-bentonite backfill, and consolidation of the soil-bentonite backfill. The model was calibrated with a well-documented case history, and predicted deformations in adjacent ground were close to measured deformations. Evaluation of the model indicates that there is good confidence in the prediction of deformations in adjacent ground, but there is lower confidence in the predicted stresses in the consolidated soil-bentonite and settlement of the backfill in the trench. A parametric study was then performed using the finite element model assuming sand sites of varying density and OCR. Deformations in adjacent ground were calculated for various soil conditions, soil-bentonite properties, and trench configurations. A correlation was found between maximum calculated settlement in adjacent ground and factor of safety against trenchPh. D.
16
LEYAMA, MACAIRE. "Etude de l'ecoulement des suspensions de bentonite". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13050.
Testo completoAbstract (sommario):
Le but du travail etait l'etude de l'ecoulement de trois suspensions de bentonite de concentration en poids 6%, 8% et 10%, en conduite circulaire en aval d'un coude a 90\ de rapport de rayons 2,5. Une caracterisation rheologique a montre que les suspensions pouvaient etre modelisees par une loi de herschel-buckley thixotrope, dont l'augmentation de la concentration provoquait l'augmentation de la consistance et de la contrainte seuil, tandis qu'elle provoquait la diminution de l'indice d'ecoulement. Il a egalement ete montre que l'etat structurel des suspensions influence fortement leur loi de comportement et que les echelles de temps caracteristiques de restructuration et de destructuration sont independantes de la concentration. En conduite on a effectue des mesures de pression et du profil de vitesse sur plusieurs positions longitudinales en aval du coude. Il a ete montre qu'en sortie de coude les profils de vitesse sont dissymetriques et les pressions elevees ; l'ecoulement est alors gouverne par les forces centrifuges et par un ecoulement secondaire localise pres de la paroi interieure et perpendiculaire a l'ecoulement principal. L'augmentation de la concentration attenue la deformation du profil de vitesse. Plus en aval le profil de vitesse est symetrique et presente une zone isovitesse qui croit lorsque l'on s'eloigne du coude et lorsque la concentration augmente ; dans cette partie l'ecoulement est domine par les forces d'inertie et de viscosite. Le retablissement de l'ecoulement est effectif dans une zone comprise entre 40 et 50 diametres apres le coude.
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Mohammad, Noor. "Desiccation Cracking Behaviour in Thin Bentonite Layers". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22231.
Testo completoAbstract (sommario):
This thesis investigates the behaviour of desiccation cracks in thin bentonite layers under different conditions (initial water content, layer thickness, temperature and mixtures with kaolinite). For this, a comprehensive series of experiment was conducted as well as some theoretical models were developed. The theoretical model was developed based on the critical cracking thickness following the principles of linear elastic fracture mechanics (Chapter 4). This model was then used in the following chapters and validated with the experimental investigations. Also, hydraulic properties of the cracked soil mass were modelled and the effects of cracks on hydraulic conductivity and water retention properties were shown. In the experimental investigations, firstly, the combined effects of initial water content and layer thickness were studied in a phase diagram to observe the behaviour of desiccation cracks (Chapter 5). It was found that critical cracking thickness could be an important factor in distinguishing cracked and non-cracked samples in the phase diagram. Characteristics of cracks (crack density, total crack length, average crack length and crack width) increase with increasing layer thicknesses as well as initial water contents. The effects of temperature (Chapter 6) and mixtures of bentonite-kaolinite (Chapter 7) on desiccation cracking were investigated in the phase diagram developed in Chapter 5. At higher temperatures, the critical thickness of a clay layer ould be decreased. Results of bentonite-kaolinite mixture demonstrated that the phase boundary shifted to increase the critical thickness of the clay layers of mixtures containing less bentonite (i.e. more kaolinite). Crack morphology was also affected by the change in temperatures and properties of the mixtures. In summary, this study shows some understanding of desiccation cracking behaviour and could provide insights for better design of clay liners, which often at risk of desiccation problem.
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Ran, Chongwei. "Performance of fracture sealing with bentonite grouting". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186118.
Testo completoAbstract (sommario):
A bentonite grouting technology has been developed to meet the requirements of fracture sealing for nuclear waste isolation and environmental engineering. The work reported presents an experimental evaluation of the performance of the bentonite fracture sealing in densely welded tuff. Included are the study of grout stability and resistance to erosion, theoretical and numerical analyses of the grout penetration process, pressure distribution in the fracture during grouting, grout delivery distance, breakthrough pressure and rheological characterization. Bentonite suspensions with solids content of 18, 20 and 22% by weight have been injected into single fractures in rock samples at 0.07 to 3.45 MPa pressure. Bentonite grouting reduces the fracture hydraulic conductivity by 7 to 9 orders in magnitude, to the level of 10⁻⁷ to 10⁻⁹ cm/s. Grout stability and erosion have been studied with long-term flow testing at up to 121 kPa hydraulic pressure. After 1,000 to 5,000 hours of flow testing, at pressure gradients of up to 91 cm/cm, the hydraulic conductivity of the grouted fracture does not increase with test time. The hydraulic conductivity of the grouted fracture decreases with increasing pressure gradient up to the wash-out pressure. Analytical solutions have been derived for pressure distribution during grouting in wedge shaped fractures and in fractures with constant aperture. Influence factors on pressure distribution in a fracture have been identified. They are yield stress, fracture shape, original aperture, deformation properties of the rock mass and the fracture, mixing of air in a grout and sample size. A mathematical solution of grout delivery distance under a given injection pressure has been developed. The breakthrough pressure has been studied, based on the mechanical deformation of the fracture applied by a normal stress across the fracture and by the grout pressure within the fracture during grouting. Results indicate that bentonite grouting is a promising fracture sealing technology. Bentonite grout has great hydraulic conductivity reduction and chemical physical stability. Some disadvantages of bentonite grout have been identified, such as the formation of hydraulic fractures in the grout and the washing away of grout particles when the applied pressure gradient is high enough.
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Ghazi, Ali Faisal. "Engineering characteristics of compacted sand-bentonite mixtures". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1615.
Testo completoAbstract (sommario):
Sand-clay mixtures are commonly used as a liner/barrier material in various engineering applications, such as construction of hydraulic and waste containments. Permeability, compressibility and strength are important properties of sand-clay mixtures and are often required for the design of the liner/barrier of the containments.
In states like Western Australia, which is covered mostly by sandy soils, engineers face difficulties with economically sourcing clays for liner/barrier applications. Any reliable research finding that recommends an optimum clay content to be used with sandy soil can be of significant importance. Such findings for the local Perth sandy soil are rarely available in the literature. Sodium bentonite can be added to Perth sandy soil as active clay in an appropriate amount to create a cost-effective liner/barrier material, especially for landfill applications. Bentonite has been used for such applications in other parts of the world.
In this research, the permeability, compressibility and strength characteristics of Perth sand–bentonite mixtures are investigated to support recommendation for a cost-effective liner material with three different local soils. A series of standard compaction tests, a onedimensional consolidation test for compressibility and permeability characteristics, and an unconfined compression test and direct shear tests for strength characteristics were conducted on nine different sand-bentonite mixtures. The mixtures were formed by mixing local soils, namely brickies sand, plaster sand, and river sand with 5, 10, and 20%, by dry weight, of sodium bentonite.
The test results show that soil permeability and compressibility are greatly affected by the type of soil used in the mixtures. The optimum amount of bentonite for brickies sand, plaster sand and river sand to achieve a permeability of less than 10-9 m/s, which is a liner design requirement, was found to be 5%, 10%, and 10%, respectively. The compression index increases linearly with the increasing bentonite content for any type of sand-bentonite mixture, but the rate of increase is relatively higher when bentonite is mixed with brickies sand. The results obtained from strength tests indicate that the unconfined compressive strength, the cohesion and the Young’s modulus all increase with increasing bentonite content, while the angle of internal friction decreases.
Further, four possible methods, namely Casagrande logarithm of time fitting method, Taylor square root of time fitting method, analytical method and improved rectangular hyperbola fitting, are compared for estimating the coefficient of consolidation of sand bentonite mixture. The analysis shows that the improved rectangular hyperbola method is the most reliable method for calculating the coefficient of consolidation among the four methods.
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Yang, Jinwen. "Hydromechanical behavior of pellets/bentonite powder mixture". Electronic Thesis or Diss., Marne-la-vallée, ENPC, 2023. https://these.univ-paris-est.fr/intranet/2023/TH2023ENPC0023.pdf.
Testo completoAbstract (sommario):
Dans le cadre du stockage géologique des déchets radioactifs de haute et moyenne activité, le mélange de pellet/poudre de bentonite est proposé comme matériau optionnel de scellement/remblayage. Les échantillons de mélange peuvent être endommagés par des fissures, ce qui compromet les performances à long terme du stockage géologique. Il est donc nécessaire de clarifier le comportement du mélange de pellet et de poudre. Des essais de compression oedométrique à succion contrôlée, de porosimétrie par intrusion de mercure (PIM) et de tomographie par microcomputation (μCT) ont été réalisés sur des mélanges de pellets de bentonite et de poudres. Comme le pellet de bentonite jouant un rôle important dans le comportement du mélange de bentonite, des essais de compression uniaxiale, de MIP et de μCT ont été réalisés sur une des pellets individuels de 32 mm en forme cylindrique. Une méthode combinée de MIP /μCT a été proposée pour déterminer la distribution de la taille des pores élargie des pellets avec de grosses fissures.Lors d'un déchargement instantané à partir d'essais oedométriques, une augmentation de la succion a été identifiée en raison du déchargement en condition quasi-non drainée. L'augmentation de la succion dépendait à la fois des effets de la succion et de la contrainte. La variation observée de l'augmentation de la succion due à l'effet de succion a été expliquée par les changements des pentes des courbes de retention d’eau, tandis que celle due à l'effet de la contrainte a résulté de la diminution des grands pores.Les résultats des essais de compression uniaxiale sur des pellets ont montré que la résistance au cisaillement uniaxial, la contrainte de fermeture des fissures (CC), la contrainte d'amorçage des fissures (CI), la contrainte d'endommagement des fissures (CD) et le module d'Young diminuent avec la diminution de la succion, ce qui illustre clairement l'effet de la succion par le ramollissement et la fissuration. Les fissures horizontales induites par le mouillage ont été fermées par le chargement à des succions ≤ 9 MPa. Les résultats des essais de compression oedométrique sur les mélanges de bentonite ont montré que l'effet combiné de la succion et de la contrainte sur le comportement global en compression du mélange de bentonite était insignifiant au stade pseudo-élastique, mais significatif au stade plastique - un indice de compression index C_c^* plus important a été observé pour une succion plus faible et une contrainte plus élevée.En ce qui concerne le comportement d’endommagement, le mouillage a généré principalement des fissures dans la zone marginale des pellets, en raison du transfert plus facile de la vapeur d'eau à travers les fissures marginales produites par la fabrication. Ce phénomène a été observé sur des pellets humidifiés dans des conditions de gonflement libre et sur des pellets de mélange de bentonite humidifié lors de l'essai à l'œdomètre. Au contraire, le chargement était susceptible de générer des fissures étendues, se propageant du centre des pellets vers la bordure en raison d'une forte concentration de contrainte localisée pour s ≥ 25 MPa. Un coefficient d'endommagement D a été défini comme le rapport entre le volume de fissuration du pellet (c'est-à-dire le volume des macropores à l'intérieur du pellet) et le volume total du pellet. Un modèle d'endommagement a été développé et adapté aux résultats expérimentaux, permettant une description quantitative de l'endommagement induit par la succion et la contrainte.Une loi de comportement à triple structure avec prise en compte de l’endommagement a été proposé pour caractériser le comportement hydromécanique du mélange de pellet/poudre de bentonite. Les paramètres du modèle ont été déterminés essentiellement sur la base des résultats expérimentaux issus de cette étude. Les résultats de Molinero-Guerra et al. (2019) et de Darde (2020) ont été exploités pour la validation du modèle proposéIn the geological disposal of high-level and intermediate-level radioactive wastes, bentonite pellet/powder mixture has been proposed as an optional sealing/backfilling material. To ensure the long-term safety of repository, it is essential to well understand the hydro-mechanical behaviour of bentonite pellet/powder mixture. The mixture samples may be damaged with cracking, compromising the long-term performance of the geological disposal facilities. The damage behaviour of bentonite pellet/powder mixture is thus necessary to be clarified. Suction-controlled oedometer compression test, Mercury Intrusion Porosimetry (MIP) and Micro-Computed Tomography (μCT) were conducted on bentonite pellet/powder mixtures. As bentonite pellet played an indispensable role in the behaviour of bentonite mixture, uniaxial compression tests, MIP and μCT were carried out on single cylindrical shape bentonite 32-mm pellet. A combined method of MIP /μCT was proposed for determining the enlarged pore size distribution of pellet with large cracks.During instantaneous unloading from oedometer tests, a suction increase was identified due to the stress release. The suction increase depended on both the effects of suction and stress. The observed variation of suction increase due to the suction effect was explained by the changes of the slopes of SWRCs, while that due to the stress effect resulted from the decrease of large pores.The results from the uniaxial compression test on single pellets showed that the uniaxial shear strength, the crack closure (CC) stress, the crack initiation (CI) stress, the crack damage (CD) stress and the Young’s modulus decrease with suction decreasing, evidencing the suction effect through softening and cracking. The wetting-induced horizontal cracks were closed by loading at suctions ≤ 9 MPa during the crack closure stage. Results from the oedometer compression tests on bentonite mixtures showed that the combined effect of suction and stress on the global compression behaviour of bentonite mixture were insignificant in the pseudo-elastic stage, but significant during the plastic stage - a larger compression index C_c^* was observed under a lower suction and a higher stress.Regarding the damage behaviour, wetting preferentially generated cracks in the marginal area of pellets, due to the easier water vapour transfer through the marginal fabrication-produced cracks. This phenomenon was observed from single pellet wetted under free swelling condition and from pellets of bentonite mixture wetted in the oedometer test. On the contrary, loading was apt to generate extended cracks propagating from the pellet centre to the border due to some localised high stress concentration for s ≥ 25 MPa. Then, a damage coefficient D was defined as the the ratio of the pellet cracking volume (i.e., the volume of macro-pores inside pellet) to the total pellet volume. A damage model was developed and fitted to the experimental results, allowing the quantitative description of wetting and loading-induced damage.A triple-structure hydro-mechanical constitutive damage model was proposed to characterize the hydro-mechanical behaviour of MX80 bentonite pellet/powder mixture. The model parameters were determined essentially based on the back-analysis of the experimental results of this study. Then, the results of Molinero-Guerra et al. (2019) and Darde (2020) were exploited for the validation of the proposed model
21
Virgl, Vítězslav. "Vlastnosti formovacích směsí ze směsných bentonitů po opakovaném použití". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382285.
Testo completoAbstract (sommario):
High class mold is required for high quality castings. At present, the demands on molding materials are being extended by adding the strict requirement of environmentalists. A suitable variant that meets both demands are green sand molds. The goal of the thesis is to repeatedly cast experimental castings into molds made of 4 types of green sand mixtures. The technological properties of the molds will be compared, the degree of bentonite degradation will be assessed and the surface quality of castings will be assessed according to the amount of adherent molding mixture.
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Fermino, Danilo Marin. "Estudo das propriedades mecânicas, reológicas e térmicas de nanocompósito de HMSPP (polipropileno com alta resistência do fundido) com uma bentonita Brasileira". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-31102011-102319/.
Testo completoAbstract (sommario):
Este trabalho aborda o estudo do comportamento mecânico, térmico e reológico do nanocompósito de HMSPP polipropileno de alta resistência do fundido (obtido por radiação gama na dose de 12,5 kGy) e uma argila brasileira bentonítica do Estado da Paraíba (PB), conhecida como chocolate com concentração de 5 e 10 % em massa em comparação a uma argila americana, Cloisite 20A. Foi utilizado nesse nanocompósito o agente compatibilizante polipropileno graftizado com anidrido maleico PP-g-AM com 3 % de concentração em massa, através da técnica de intercalação do fundido utilizando uma extrusora de dupla-rosca e, em seguida, os corpos de prova foram confeccionados em uma injetora. O comportamento mecânico foi avaliado pelos ensaios de tração, flexão e impacto. O comportamento térmico foi avaliado pelas técnicas de calorimetria exploratória diferencial (DSC) e termogravimetria (TGA). O comportamento reológico foi avaliado em um reômetro de placas paralelas. A morfologia dos nanocompósitos foi estudada pela técnica de microscopia eletrônica de varredura (MEV). As bentonitas organofílicas e os nanocompósitos foram caracterizados por difração de raios X (DRX) e infravermelho (FTIR). Nos ensaios mecânicos houve um aumento de 9 % na resistência à tração e no módulo de Young, para os nanocompósitos de HMSPPC com argila Cloisite 20A. No ensaio de impacto izod, o nanocompósito HMSPPB 10 % com argila chocolate obteve um aumento de 50 % na resistência ao impacto.This work concerns to the study of the mechanical, thermal and rheological behavior of the nanocomposite HMSPP - high melt strength polypropylene (obtained at a dose of 12.5 kGy) and a Brazilian bentonite clay from State of Paraiba (PB), known as \"Chocolate\" in concentrations of 5 and 10 % by weight in comparison with one American clay, Cloisite 20A. The compatibilizer agent based on maleic anhydride grafted polypropylene, known as PP-g-MA, was added at 3 % weight concentration through the melt intercalation technique using a twin-screw extruder, and afterwards, the specimens were prepared by injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the differential scanning calorimetry (DSC) and thermogravimetry (TGA). The rheological behavior was evaluated in parallel-plate rheometer. The morphology of the nanocomposites was studied by the technique of scanning electron microscopy (SEM). The organophilic bentonite and the nanocomposites were characterized by X-ray diffraction (XRD) and infrared (FTIR). Results of mechanical tests showed a 9 % increase in the tensile strength and Young\'s modulus for the nanocomposites HMSPPC, with Cloisite 20A clay. The nanocomposite HMSPPB 10 %, with \"chocolate\" clay obtained a 50 % increase in the impact strength in the izod impact test.
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RODRIGUES, Katyane. "Desenvolvimento e caracterização de nanocompósitos de bentonita contendo filtros-solares". Universidade Federal De Pernambuco, 2013. https://repositorio.ufpe.br/handle/123456789/18387.
Testo completoAbstract (sommario):
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Facepe e Capes
A radiação UV compreende uma região do espectro eletromagnético e é classificada conforme o comprimento de onda em: UVC (100-290 nm), UVB (290-320 nm) e UVA, UVA2 (320-340 nm) e UVA1 (340-400nm). Apesar de serem responsáveis pela maioria dos efeitos benéficos, também o são pelos efeitos prejudiciais e, mesmo tendo o organismo humano desenvolvido mecanismos de defesa, estes não são suficientes, por isso o uso de preparações fotoprotetoras tornou-se essencial. A associação de filtros solares, apesar de ser uma forma usual para aumentar os valores do fator de proteção solar (FPS) destas preparações, ocasiona uma série de problemas, como irritação, reações fototóxicas e alérgicas. Em vista disso, o objetivo desse estudo foi o uso de bentonitas como filtro físico para associação a filtros químicos UVA - avobenzona (AVO), UVB - metoxicinamato de etilexila (EHMC) ou de amplo espectro - oxibenzona (OXI). A escolha da bentonita justifica-se, além de ser um recurso natural, por sua estrutura lamelar, podendo gerar compostos de intercalação, o que pode proteger o filtro químico do sol, prolongando sua ação, e a pele do filtro solar. Foram produzidos, então, via solução, sistemas de cada filtro químico supracitado com bentonita sodica (SB) ou organofílica (OB), em diferentes proporções, obtidos por centrifugação [C] ou evaporação rotativa [R]. O rendimento dos produtos foi calculado indiretamente por espectrofotometria do sobrenadante dos centrifugados, de forma que foram escolhidas as proporções de maior rendimento de cada sistema, [C] e [R], para serem caracterizados. Os melhores sistemas com os respectivos rendimentos foram os seguintes: AVO-SB 3:1 (63 ± 1%); AVO-OB 2:1 (51 ± 1%); EHMC-SB 0,5:1 (79 ± 1%); EHMC-OB 0,5:1 (82 ± 1%); OXI-SB 1:1 (59 ± 2%); OXI-OB 1:1 (58 ± 1%). Os produtos foram caracterizados por difração de raios X (DRX), análise termogravimétrica (TG), calorimetria exploratória diferencial (DSC), espectroscopia de infravermelho com transformada de Fourier (FTIR) e microscopia eletrônica de transmissão (MET), os quais, de forma geral, confirmaram a formação dos compostos de intercalação. Para análise dos valores de FPS in vitro, todos os filtros foram incorporados em uma emulsão-base a 2,5%, em sua forma pura ou intercalada em bentonita. As preparações mostraram-se estáveis pelo teste de estabilidade preliminar e com valores de pH em conformidade com a via tópica. Os dados de transmitância revelaram um aumento significativo do FPS em todos os compostos de intercalação de AVO, se comparado ao filtro puro (0,7 ± 0,5), destacando-se o sistema AVO-OB [C] (17 ± 2); com o EHMC, mais uma vez o sistema com OB [C] se destacou (17 ± 1 versus 8 ± 1 para o EHMC puro), tendo sido o único, nesse caso, a ter um aumento significativo; os resultados dos compostos de intercalação contendo OXI não mostraram diferença nos valores de FPS, provavelmente porque o FPS da OXI pura já é bem alto (19 ± 3), pelo contrário, o sistema OXI-SB [C] reduziu o FPS (12 ± 0,5). Os resultados mostraram a viabilidade da formação de compostos de intercalação filtros solares – bentonita e da utilização, em especial, da OB em formulações fotoprotetoras.
UV radiation comprises a region of the electromagnetic spectrum and is classified as wavelength: UVC (100-290 nm), UVB (290-320 nm) and UVA UVA2 (320-340 nm) and UVA1 (340-400 nm). Despite being responsible for the most beneficial effects, so are the harmful effects and even having the human organism developed defense mechanisms, these are not enough, so the use of sunscreen preparations became essential. The combination of sunscreens, despite being a usual way to increase the values of the sun protection factor (SPF) of these preparations, causes a number of problems, such as irritation, allergic and phototoxic reactions. In view of this, the objective of this study was the use of bentonite as a physical filter for joining chemical filters UVA - avobenzone (AVO), UVB - methoxycinnamate etilexila (EHMC) or broad-spectrum - oxybenzone (OXI). The choice of bentonite is justified, besides being a natural resource for its lamellar structure, which can generate intercalation compounds, which can protect the chemical filter the sun, prolonging its action, and the skin of sunscreen. Produced were then via solution, each filter chemical systems above with sodium bentonite (SB) or organophilic (OB), in different proportions, obtained by centrifugation [C] or rotary evaporation [R]. The yield of the products was calculated indirectly by spectrophotometry of the supernatant centrifuged, were chosen so that the proportions of each system higher yield, [C] and [R], to be characterized. The best systems with their yields were as follows: AVO-SB 3:1 (63 ± 1%); AVO-OB 2:1 (51 ±2%); EHMCSB 0.5:1 (79 ± 1%); EHMC-OB 0.5:1 (82 ± 1%); OXI-SB 1:1 (59 ± 2%); OXI-OB 1:1 (58± 1%). The products were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), infrared spectroscopy Fourier transform (FTIR) and transmission electron microscopy (TEM), which so Generally, confirmed the formation of intercalation compounds. For analysis of in vitro SPF values, all filters were incorporated into an emulsion base 2.5% in pure form or interleaved bentonite. The preparations were stable for preliminary stability test with pH values in accordance with topically. The transmittance data revealed a significant increase in FPS in all intercalation compounds of AVO, compared to pure filter (0.7 ± 0.5), highlighting the AVO-OB system [C] (17 ± 2); with EHMC, again with the system B [C] is highlighted (17 ± 1 versus 8 ± 1 for pure EHMC), being the only, in which case , to have a significant increase, the results of intercalation compounds containing OXI showed no difference in SPF values, probably because the SPF of pure OXI is already quite high (19 ± 3), in contrast, the system OXY -SB [C] reduced the FPS (12 ± 0.5). The results show the feasibility of the formation of intercalation compounds sunscreens - bentonite and use, especially in formulations of OB sunscreens.
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Ayar, Engin Mazlum Süleyman. "Bentonit kili kullanılarak su ortamından fosforun adsorbsiyon ile giderimi /". Isparta : SDÜ Fen Bilimleri Enstitüsü, 2009. http://tez.sdu.edu.tr/Tezler/TF01287.pdf.
Testo completo
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Camargo, Karina Retzlaff. "Avaliação da condutividade hidráulica e da resistência ao cisalhamento de misturas solo-bentonita: estudo de caso de um aterro sanitário localizado em Rio Grande (RS)". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-18062013-110028/.
Testo completoAbstract (sommario):
A utilização do solo natural compactado com bentonita empregado em camadas impermeáveis para retenção de contaminantes é bastante usual para aterros sanitários. Neste trabalho são apresentados resultados de ensaios condutividade hidráulica e de resistência ao cisalhamento, realizados em equipamentos triaxiais. Além do solo natural, foram utilizadas misturas solo-bentonita nos teores de 2%, 4% e 6%. O solo arenoso ensaiado é encontrado na Planície Costeira Sul do Estado do Rio Grande do Sul. Os valores de condutividade hidráulica diminuiram tanto com o acréscimo do teor de bentonita, quanto com o aumento da tensão de confinamento. A condutividade hidráulica do solo apresentou uma redução de três ordens de grandeza quando este foi compactado com 6% de bentonita (de \'10 POT.-7\' para \'10 POT.-10\' m/s). Em relação a resistência ao cisalhamento do material, constatou-se que com o acréscimo do teor bentonita de 0 para 6%, a coesão efetiva aumentou (de 2,3 para 12,8 kPa) e o ângulo de atrito efetivo diminuiu (de 22,7º pra 14,0º).Compacted soil-bentonite mixtures used as impermeable layers for retention of contaminants is quite usual in landfills. This paper presents the results of hydraulic conductivity and shear strength tests conducted in a triaxial apparatus. Natural soil, and soil-bentonite mixtures at 2%, 4% and 6% concentrations were tested. The sandy soil tested is found in the Southern Coastal Plain of Rio Grande do Sul. The hydraulic conductivity decreased with both the increase of bentonite content and increase of confining stress. Compared to natural soil, the hydraulic conductivity of compacted soil-bentonite mixtures at 6% content decreased by three orders of magnitude (from \'10 POT.-7\' to \'10 POT.-10\' m/s). Regarding the material shear strength, it was found that when the natural soil is compared to compacted soil-bentonite mixtures at 6% content, the effective cohesion increased (from 2.3 to 12.8 kPa) and the effective friction angle decreased (from 22. 7º to 14.0º).
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Wold, Susanna. "On diffusion of organic colloids in compacted bentonite". Doctoral thesis, KTH, Chemistry, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3522.
Testo completoAbstract (sommario):
The main issue of this thesis was to obtain information ondiffusion and sorption behaviour on organic colloids incompacted bentonite through experimental studies. It was tostudy if bentonite is an efficient barrier for organic colloidsor not. If colloids diffuse into bentonite in sufficientconcentrations, the speciation and sorption characteristics ofdiffusing radionuclides will change. Colloids might facilitatetransport, especially of radionuclides immobilised by strongsorption on bentonite.
Laboratory experiments were performed to determine thestability of humic substances (HS) and bentonite colloids insolutions of ionic strengths representative for deep graniticgroundwaters. The HS but not the bentonite colloids were foundto be stable in these conditions.
The competition between complexation with HS and sorption onbentonite of the cations Sr(II) and Eu(III) were studied inbatch experiments. Eu(III) was foundto complex with HS to bigextent. If HS is present in sufficient concentrations andstable in compacted bentonite, the Eu(III)-HS will be a speciesthat has to be accounted for. Sr(II) sorption decreases in thepresence of HS at ionic strength 0.01 M, but not at 0.1 M.Sr(II) sorbs weakly on bentonite and forms weak complexes withHS.
The diffusion of Sr(II) in bentonite compacted to 1.8 g/cm3dry density and equilibrated with 0.1 M NaClO4 solutions wasstudied with and without HS in the system. The HS concentrationwas varied between 0.1 and 0.2 g/l. The Sr(II) diffusion wasnot affected by the presence of HS, which is in agreement withthe competition data of complexation to HS and sorption onbentonite.
Diffusion of Co(II) and Eu(III) was studied in bentonite ofcompaction 0.6-1.8 g/cm3in the presence of HS. Eu(III)diffusion without HS in the system was studied as well. Co(II)diffusivity was found to increase significantly in the presenceof HS and the Kd-values decreased drastically. The decrease inthe Kd-values was found to be ionic strength dependent. This isexplained by HS complexation capacity decreases with increasingionic strength. The results indicate that the strongly surfacecomplexed Co(II) is mobilised by HS, but the Co-HS is not theonly diffusing Co(II) species in the experimental conditions ofthis study.
Considering that Eu(III) sorbs strongly on bentonite, thediffusivity of Eu(III) was found to be rather high at ionicstrength 0.01 M. The high diffusivity rates are explained bythat the cation-exchanged Eu(III) around 1 % of the totalsorption is in practise mobile. In the presence of HS, Eu(III)diffusivity increases and the sorption decrease drastically.The Eu(III)-HS seems to be the dominating Eu(III) species whenthe HS concentrations are sufficiently high, and the HSsorption and diffusivity govern the system.
Keywords:Diffusion, sorption, complexation, stability,bentonite, humic substances, Sr(II), Co(II) and Eu(III).
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Uskarci, Togan. "Behaviour Of Bentonite Suspensions In Non-aqueous Media". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607161/index.pdf.
Testo completoAbstract (sommario):
Bentonite is a smectite type clay mineral and swells in water. In this thesis, the effect of acetone, methyl-ethyl ketone, n-hexane on the properties of bentonite was determined by thermal analysis and water absorption tests. The tests indicated no significant change with treating bentonite with organic liquids.
Because of the swelling property, only small amount of bentonite can be suspended in water. This may limit certain applications of bentonite. In this thesis, feasibility of suspending large quantities of bentonite in a non-aqueous media was studied. The concentrations for a pumpable high
solid bentonite slurry were determined. As aqueous slurry showed pumpable properties up to 30-35 pounds/barrel, this concentration was as high as 125-150 pounds/barrel for acetone, 175-200 pounds/barrel for methyl-ethyl ketone and 325-350 pounds/barrel for n-hexane.
Bentonite deposite has a complicated composition, containing free silica minerals, such as quartz, cristobalite, and opalsilicate minerals, such as feldspar, mica, and zeolite
carbonates or sulfates of alkaline earth metals, such as calcite, dolomite, and gypsum
and, in addition, iron compounds and humus. As mined it is primarily broken and dried and then pulverized by means of an attrition grinding machine. In this study dispersion of raw bentonite by high shear blending and shaking forces in the presence of acetone, methyl-ethyl ketone and n-hexane and eliminating the non-clay impurities by screening were studied. Many attempts have been made to provide a bentonite composition retaining the full swelling properties of the bentonite by the addition of non-aqueous liquids for obtaining a flexible waterproofing sheet. In this research the possible method for deposition of bentonite in a sponge by saturating the sponge with bentonite using organic liquids was investigated.
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Takai, Atsushi. "Geoenvironmental Reliability of Soil-Bentonite Mixture Cutoff Walls". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188847.
Testo completo
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Wong, Eric 1975. "Surfactant-enhanced electrokinetic remediation of dichlorobenzene-contaminated bentonite". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31077.
Testo completoAbstract (sommario):
A dense nonaqueous phase liquid, o-dichlorobenzene (o-DCB) was removed by surfactant-enhanced electrokinetic remediation from saturated bentonite clay. The surfactant was Antarox BL-236, a nonionic surfactant with a solubilization capacity of 0.052 g DCB/g surfactant. The 9 cm long bed, which initially contained 10 wt % bentonite and a dispersion of o-DCB (2910 or 5821 ppm) in water, was placed in a horizontal cylinder (5 cm ID) and held at each end by a supported filter paper. Carbon disk electrodes were located in compartments at each end of the bed. Surfactant solution or distilled water was fed to the anode compartment and effluent was withdrawn from the cathode compartment to maintain liquid levels. A constant direct current of 1.53 mA/cm2 of bed cross sectional area was applied. The current generated hydrogen ions at the anode, hydroxyl ions at the cathode, and an electroosmotic flow from the anode to the cathode. Stainless steel pin electrodes placed in the bed and pH electrodes inserted into the bed and the electrode compartments gave continuous measurements of voltage differences and pH changes. Experimental runs were 48 to 96 hours in duration.To prevent cracking of the bed, which increased the energy requirements, the cathode compartment was flushed continuously with 0.01 M HNO3, a procedure called cathode rinse. An anode feed of 10 wt % surfactant solution removed six times more DCB in 4 days than distilled water. About 20% of the solubilization capacity of the surfactant was utilized at 2910 ppm initial DCB, increasing to 34% for 5820 ppm. DCB was detected in the effluent after about 1.5 pore volumes of liquid passed through the bed; thereafter the rate of DCB removal was approximately constant. The effects of surfactant concentration and NAPL concentration on DCB removal and the energy expenditure were determined.
30
Sánchez, González Sandra. "The swelling pressure of bentonite and sand mixtures". Thesis, KTH, Skolan för kemivetenskap (CHE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158511.
Testo completoAbstract (sommario):
The compacted bentonites are used as buffer and backfill materials for engineering barriers for high-level nuclear waste repositories located underground. For this purpose, it is very important to evaluate the swelling characteristics of this clay. The swelling capacity is one of the most important properties of the bentonite clay. The swelling behaviour is due two mechanisms, the crystalline swelling and the osmotic swelling. These mechanisms produce an increase in the distance between the layers of montmorillonite which is one component of bentonite. The result of the swelling capacity is the swelling pressure. It has been studied in several investigations. The results of experimental tests have been collected and compared in this thesis, considering only the Na-dominant bentonite and sand and distilled water as test solution. The experimental tests show that there is only an unique relation between different bentonites in the Na-dominant bentonite and sand mixture swollen depending on its final dry density. Also, the relation between the swelling pressure and the clay void ratio shows the mechanism of the swelling pressure. On the other hand, a mechanistic model is used to predict the swelling pressure of fully saturated bentonite and sand mixture in distilled water. Firstly, it has been compared with the results of experimental tests and it should be pointed out that the model gives good predictions. In addition, the model has been used to make sensitivity analysis with different parameters of bentonite. The most important conclusions in this section show that the swelling pressure mainly depends on the distance among particles. Also, the sensitivity analyses indicate which parameters should be fitted more carefully for future studies to validate this model with different bentonites.
31
Ng, Man Yin Albert. "Modelling of hydraulic fracturing in cement bentonite geomaterials". Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/283851.
Testo completo
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Ran, Chongwei 1956. "Effectiveness of rock fracture sealing with bentonite grouting". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278016.
Testo completoAbstract (sommario):
A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.
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Auboiroux, Michel. "Affinité de différents cations métalliques (Co2+, Ni2+, Cu2+, Zn2+, Cd2+ et Pb2+) pour une montmorillonite calcique : expérimentation et applications". Orléans, 1998. http://www.theses.fr/1998ORLE2025.
Testo completoAbstract (sommario):
L'etude experimentale des interactions entre metaux lourds (co, ni, cu, zn, cd, pb) et une montmorillonite purifiee calcique est menee en considerant differentes conditions experimentales (force ionique moderee ou elevee, argile en suspension ou compactee). L'argile et les solutions utilisees sont prealablement caracterisees. Le mecanisme d'echange ionique est mis en evidence par analyse quantitative xps d'echantillons echanges avec cd et pb. Le traitement des resultats experimentaux obtenus en solutions de force ionique moderee et constante, par un modele d'echange ionique et sa fonction puissance permettent de retracer la repartition entre especes adsorbees et especes dissoutes, sur le code de calcul phreeqc. La theorie hsab (hard and soft acid and base) permet de quantifier la sequence de selectivite observee experimentalement pour cu, zn, cd et pb en reliant les proprietes de surface de l'argile a l'electronegativite et la softness des metaux. Une discussion est proposee concernant le role joue par l'heterogeneite energetique des surfaces basales de l'argile et l'hydratation des cations sur la selectivite. Des experiences en solutions de force ionique 3m, montrent l'adsorption anionique de zn et pb (essentiellement presents sous forme m(cl 4) 2 -) mettant en evidence le role preponderant de la speciation des metaux (determinee par le modele de pitzer) sur leurs interactions avec l'argile. Le reste de ce travail est consacre a deux applications de l'echange ionique : _ les performances hydrodynamiques et chimiques d'un geosynthetique bentonitique (gsb) et d'une couche d'argile dans un dispositif d'etancheite de fond de decharge, sont comparees par simulation. Compte tenu de leur faible epaisseur, les gsb ne peuvent pas etre consideres comme equivalents a une couche d'argile compactee ; _ l'utilisation d'argiles comme depolluants est envisagee par des experiences portant sur des effluents industriels reels. La calcination des argiles permet l'inertage des metaux.
34
Colmenares, Montanez Julio Estaban. "Suction and volume changes of compacted sand-bentonite mixtures". Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/7775.
Testo completo
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Krol, Magdalena M. "Implications of trichloroethylene diffusion through soil-bentonite slurry walls". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ58050.pdf.
Testo completo
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Durham, J. "The prediction of shear strength in bentonite/cement groups". Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7435.
Testo completoAbstract (sommario):
Bentonite/cement grouts and slurries are used in the civil engineering industry in various ground engineering processes. The specifications usually require a minimum compressive strength or shear strength at 28 days age. The interaction between the materials namely bentonite, cement and water is complex; both the bentonite content and the cement content of the grout affect the development of shear strength. An investigation of the development of shear strength has been made for a range of grouts with bentonite contents from 5% to 20% by weight of water and water/cement ratios from 4 to 12. The shear strength was measured at various ages up to 336 days age using a Pilcon hand held shear vane tester, for many grout mixes the shear strength was still increasing at 336 days age. Two mixes were placed in vertical plastic pipes in order to investigate how shear strength may vary with depth in a ground borehole. A mathematical model has been developed to predict the shear strength of any grout mix at any age within the range studied, the model comprises a simple equation with two coefficients A and B which can be obtained from contour plots depending on the mix proportions. The model has been tested using four mixes different from those use to derive the model; statistically there is no significant difference between the actual and predicted results and the model can be used with reasonable confidence.
37
Ishidera, Takamitsu. "Study on diffusion behavior of radionuclides in compacted bentonite". 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57264.
Testo completo
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Britton, Jeremy Paul. "Soil-Bentonite Cutoff Walls: Hydraulic Conductivity and Contaminant Transport". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28642.
Testo completoAbstract (sommario):
Soil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls.
When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. There are some cases, however, such as circumferential cutoff walls with inward hydraulic gradients, where it is also important to consider the variability in hydraulic conductivity from point to point in the wall in contaminant transport studies.
A pilot-scale facility was envisioned where subsurface barrier issues such as those mentioned above could be studied. In 1998, the Subsurface Barrier Test Facility (SBTF) was constructed. In this facility, pilot-scale subsurface barriers can be installed using real construction equipment and tested in a controlled environment.
The effectiveness of various methods of measuring the hydraulic conductivity of cutoff walls was studied by building and testing three pilot-scale soil-bentonite cutoff walls at the SBTF. The following currently used test methods were evaluated: API tests on grab samples, lab tests on undisturbed samples, piezometer tests (slug tests), and piezocone soundings. The use of slug tests in cutoff walls was improved in this research in the areas of avoiding hydraulic fracture and accounting for the close proximity of the trench walls. The SBTF allows for measurement of the global, average hydraulic conductivity of an installed pilot-scale cutoff wall, which is a useful value to compare to the results of the above-mentioned tests. The two main factors differentiating the results of the different test methods used for the pilot-scale walls were remolding and sample size. Remolding of the API samples significantly reduced the hydraulic conductivity of these samples compared to the hydraulic conductivity measured in lab tests on undisturbed samples, which were of similar size. For the other tests, the degree and extent of remolding were less significant compared to in the API tests. For these tests, the scale of the measurement is believed to be the main factor differentiating the results. Hydraulic conductivity was found to increase as the sample volume increased, with the global measurement of the average hydraulic conductivity producing the highest value.
The influence of variability in hydraulic conductivity on contaminant transport through cutoff walls was studied from a theoretical standpoint using the one-dimensional advection-diffusion equation. Charts were developed that can be used to estimate the flux through a cutoff wall based on knowledge of the average hydraulic conductivity of the wall and an estimate of the variability in hydraulic conductivity. Data sets of hydraulic conductivity from lab tests on soil-bentonite samples from four cutoff wall case histories were used to estimate typical values of variability. The contaminant transport analyses showed that the effect of variability may be significant when the hydraulic gradient opposes the concentration gradient, which is the case for a circumferential cutoff wall with an inward hydraulic gradient. The goal of a circumferential cutoff wall with an inward hydraulic gradient is to reduce the outward diffusive flux of contaminant by inducing an inward advective flux. The effect of variability in hydraulic conductivity is to reduce the effectiveness of this scheme.Ph. D.
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PUMA, SARA. "Chemico-mechanical improvement of bentonite barriers for pollutant containment". Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2507922.
Testo completoAbstract (sommario):
Pollution control represents one of the main problems of public interest in all industrialised countries.
Since the 1970s, when the engineering of waste containment began, the overall objective of Environmental Geotechnics was to limit contaminant discharge to groundwater and subsoil. Since the 1990s design engineers and environmental agencies have shown a growing interest in the use of geosynthetic clay liners (GCLs) as an alternative to compacted clays in cover systems or in bottom lining of waste containment facilities because they have very low hydraulic conductivity to water and relatively low cost. GCLs contain a thin layer of sodium bentonite with a dry thickness between 5 and 10 mm, sandwiched between two geotextiles or glued to a geomembrane, GM. The excellent hydraulic performances of GCLs have to be attributed to bentonite characteristics and, since these last are greatly influenced by the chemical composition of the environment surrounding the barrier and by the state parameters, the performances of GCLs can be altered, and then worsened, by a simple variation of the chemical or physical boundary conditions. Aimed at solving this last issue, clay liners and GCLs have undergone great change during the last two decades, with new material being introduced (i.e. polymers) and new design methods being adopted (i.e. membrane behaviour investigation, contaminant diffusion estimation).
The research project developed during the Ph.D. has been focused on bentonite barriers. The term “bentonite barriers” includes bentonite or bentonite-based barriers which find application both in urban waste landfill, hazardous or radioactive wastes final disposal and in hydrocarbon containment. The developed theoretical and experimental study has had the aim of evaluating the possible improvement of containment performance of the bentonite barriers, towards standard and non standard liquids, acting on their state parameters, chemical composition, and boundary conditions at installation. The contents of the thesis are reported below:
Chapter 1 – Bentonite barriers.
This chapter is an introduction to the topic of the research activity: the improvement of contaminant containment performances of the bentonite barrier. Chapter 1 gives a phenomenological and physical description of the mineralogical, chemical and physical properties of sodium and calcium bentonite. Moreover, the main features and issues concerning Geosynthetic Clay Liners, and bentonite barriers in general, are introduced.
Chapter 2 – Containment performances of natural and polymer-modified bentonite barriers subjected to physical pre-treatments.
The role of physical pre-treatments, such as pre-hydration, pre-consolidation and salt removal, applied to sodium and polymer modified bentonites, has been analyzed in the Paper reported in chapter 2, titled: “THE ROLE OF PHYSICAL PRETREATMENTS ON THE HYDRAULIC CONDUCTIVITY OF NATURAL AND POLYMER MODIFIED SODIUM BENTONITES”. Moreover, the effect of the presence or absence of needling across the bentonite layer has been studied.
All these variables have been shown to influence the hydraulic performances of bentonite through hydraulic conductivity change in both short and long term conditions. Physical pre-treatments and polymer addiction, in fact, influence the swelling behaviour of bentonite and its response to the cation exchange phenomenon.
Chapter 3 – Osmotic and swelling properties of bentonite barriers.
In the Paper included in this chapter, titled “COUPLED CHEMICAL-HYDRAULIC-MECHANICAL BEHAVIOUR OF BENTONITES”, a theoretical approach has been proposed in order to derive constitutive equations which describe the coupled chemical-hydraulic-mechanical behaviour of bentonite barriers, with the aim to assess their long term performance. The phenomenological parameters that govern the transport of electrolyte solutions through bentonites, i.e. the hydraulic conductivity, the reflection coefficient, which is also called the chemico-osmotic efficiency coefficient, and the osmotic effective diffusion coefficient, have been measured through laboratory tests on a natural sodium bentonite The obtained results have been interpreted by assuming that the microscopic deviations of the pore solution state variables from their average values are negligible. In this way, it is possible to interpret the macroscopic behaviour on the basis of the physical and chemical properties of the bentonite mineralogical components.
At the end of the chapter two further chemico-osmotic tests are described aimed at analysing (1) the osmotic behaviour of calcium bentonite and (2) the effects induced on osmotic behaviour by stress-strain properties. Moreover, the osmotic results are confronted with data from literature.
Finally, the design of a new osmotic apparatus to measure both the swelling pressure and the reflection coefficient is proposed.
Chapter 4 – Hydrocarbon containment performances of natural and polymer-modified bentonite barriers.
Background information on hydrocarbon behaviour in soils is reported in the first part of this chapter. In particular, the effects of capillary forces on the distribution of immiscible fluids in porous media and the theoretical aspects, regarding the formation of tactoids induced by the low dielectric constant that characterizes the most of hydrocarbon species, are studied.
An experimental study is presented in the Paper titled “HYDRAULIC PERFORMANCE OF GCLS WITH DIESEL OIL AND POLYMER TREATMENT PROPOSAL”, which is aimed at evaluating the hydraulic performance of a needle-punched GCL using both standard liquids (i.e. de-ionized water) and diesel oil in order to estimate the change in hydraulic conductivity and swelling ability upon contact or permeation with hydrocarbons. Moreover, the hydraulic conductivity to diesel oil of GCL samples saturated at different initial gravimetric water contents was investigated with the aim to analyse the effect of initial water saturation on hydrocarbon containment performances. Finally, the swelling and hydraulic performances to diesel oil of an innovative material, obtained by mixing sodium bentonite with a polymer, were measured.
Chapter 5 – Containment performances of a bentonite-based barrier constituted of municipal solid waste bottom ashes.
The research described in the Paper included in this chapter, titled “REUSE OF MSWI BOTTOM ASH MIXED WITH NATURAL SODIUM BENTONITE AS LANDFILL COVER MATERIAL” has the aim of evaluating the reuse of incinerator slag, mixed with sodium bentonite, for landfill capping system components. A chemical, hydraulic and mechanical characterization was performed on pure bottom ash (BA) samples from an incinerator in the North of Italy and on the BA-bentonite mixture. This study qualifies the BA-bentonite mixture as a suitable material for landfill cover in Italy. Moreover, owing to the low release of toxic compounds from BA, the proposed cover system does not affect the leachate quality in the landfill.
Chapter 6 – Finite difference modelling of diffusive flux of Calcium through a bentonite barrier in in-situ conditions.
The evidence of the strong degradation induced in the hydraulic performances of sodium bentonite barriers by the cation exchange phenomenon has been highlighted in the previous chapters. This experimental result underlines the need to study the transitional development of the cation exchange phenomenon with the aim to compare that to the period in which landfill barrier performances have to be guaranteed in in-situ conditions.
The mathematical study developed in this chapter is focused on the evaluation of the role of the diffusive component of Calcium flux in the cation exchange phenomenon which can develop in a sodium bentonite barrier, placed in an environment inexorably rich in chemical compounds containing soluble Calcium (i.e. the natural soil, the aquifer, the drainage layer saturated with waste leachate or raining water).
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NASCIMENTO, Neyber Fádio Cavalcanti. "Reologia de argilas bentoníticas do Estado da Paraíba aditivadas com MgO para uso em tintas base água". Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1122.
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Capes
Devido a suas propriedades reológicas, uma grande quantidade de bentonitas são empregadas como aditivos para tintas como agentes espessantes, estabilizadores e antisedimentantes. Este trabalho teve por objetivo avaliar os efeitos da ativação individual e conjunta por Na2CO3 e MgO nas propriedades reológicas de argilas bentoníticas policatiônicas do estado da Paraíba visando o uso das mesmas como agentes espessantes de tintas de base água.Foram utilizadas argilas bentoníticas policatiônicas do estado da Paraíba das ocorrências de Boa Vista e Cubati, denominadas de Chocolate Boa Vista (CH BV) e Chocolate Campos Novos (CH CN), respectivamente. A caracterização física, química e mineralógica das amostras foi realizada pelos seguintes métodos: análise granulométrica (AG), fluorescência de raios X (EDX), difração de raios X (DRX), capacidade de troca de cátions (CTC), área específica (AE), análise térmica diferencial (ATD) e análise termogravimétrica (ATG). Os percentuais dos aditivos Na2CO3 e MgO foram de 0,0%, 0,5%, 1,0%, 1,5%, 2,0%, 3,0% e 4,0% quando utilizados de forma individual e de 0,5%, 1,0%, 1,5% de MgOe 0,5%, 1,0%, 1,5% de Na2CO3 associados de modo que todas as combinações fossem analisadas.Os resultados obtidos foram comparados com as especificações API e ISO de bentonitas para uso em tintas base água. A ativação apenas com MgO não proporcionou maiores valores de viscosidade às suspensões bentoníticas estudadas. A ativação apenas com Na2CO3, na forma sólida, e com ambos aditivos aumentou a viscosidade das dispersões bentoníticas com argila CH BV e foram observados comportamentos reológicos do tipo pseudoplástico com tensão de escoamentoe tixotrópico. Verificou-se também que as argilasCH BV e CH CN, com ambos aditivos, apresentaram comportamentos pseudoplástico com tensão de escoamentoe tixotrópico. Conclui-se que as bentonitas CH BV e CH CN podem ser utilizadas como espessantes de tintas de base água.
Due to its rheological properties, a large amount of bentonites are used as additives for paints as thickeners, stabilizers and anti-settling. This study aimed to evaluate the effects of individual and joint activation Na2CO3 and MgO in the rheological properties of polycationic bentonite clays of the Paraíba state aimed at using them as thickeners for water-based paints. Polycationic clays were used bentonite state of Paraiba occurrences of Boa Vista and Cubati, called Chocolate Boa Vista (CH BV) and Chocolate Campos Novos (CH CN), respectively. The physical, chemical and mineralogical samples was performed by the following methods: Particle size analysis (GA), X-ray fluorescence XDE), X-ray diffraction (XRD), capacity of cation exchange (CEC), specific area (SA), differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). The percentages of MgO and additives Na2CO3 were 0.0%, 0.5%, 1.0%, 1.5%, 2.0%, 3.0% and 4.0% when used individually, and 0.5%, 1.0%, 1.5% MgO and 0.5%, 1.0%, 1.5% Na2CO3 associated so that all combinations were analyzed. The results obtained were compared with API bentonite and ISO specifications for use in water based paints. Activation only with MgO did not provide higher viscosity values for bentonite suspensions studied. Activation only with Na2CO3, in solid form, and with both additives increased the viscosity of bentonite clay dispersions with CH BV and were observed rheological behavior of the pseudoplastic type with yield stress and thixotropic. It was also found that the clays CH BV and CH CN with both additives, presented pseudoplastic behavior with yield stress and thixotropic. It follows that the bentonite and CH CN CH BV can be used as thickeners in water based paints.
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Tiranarat, Chanan. "An investigation of the use of modified clay to remove colour from process wastewater". Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269717.
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Jozja, Nevila. "Etude de matériaux argileux albanais : caractérisation multi-échelle d'une bentonite magnésienne : impact de l'interaction avec le nitrate de plomb sur la perméabilité". Orléans, 2003. https://tel.archives-ouvertes.fr/tel-00003740.
Testo completoAbstract (sommario):
Ce travail s'inscrit dans le cadre des études sur l'interaction argile/polluant, concernant l'utilisation des argiles comme barrière d'un site de stockage de surface. Le travail présenté se propose de relier les variations de la perméabilité avec les modifications structurales et microtexturales pouvant être induites par la fixation d'un cation métallique sur une argile. Parmi 3 matériaux argileux albanais présélectionnés, celui de Prrenjas, formé par pédogenèse puis sédimentation continentale aux dépens d'une roche mère (ultrabasique), a été choisi en raison de ses caractéristiques proches d'une bentonite.
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Diot, Frédéric. "Application des techniques séparatives basées sur le magnétisme et l'électricité à la valorisation des fines de sable de fonderie". Vandoeuvre-les-Nancy, INPL, 2001. http://www.theses.fr/2001INPL598N.
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Le but principal de ce travail porte sur le recyclage de sable de fonderie (séparation quartzbentonite par voie sèche). La bibliographie fait une mise au point sur les différentes méthodes de séparations (magnétique, pneumatique et électrostatique) et les sables de fonderie. L'étape de la caractérisation minéralurgique du sable à vert montre que l'argile (bentonite) est concentrée principalement dans la fraction de taille inférieure à 40Jlm. L'électrostatique est la voie retenue pour la récupération. Les différents tests effectués montrent qu'il est possible au niveau du laboratoire de recycler 50% de l'argile contenue dans le sable à vert qui part en décharge. La modélisation des trajectoires des particules, utilisant la méthode de Runge Kutta, est en accord avec les observations. L'utilisation de l'ACP n'a pas permis de mettre en évidence un facteur prédominant permettant d'augmenter la récupérationThis work deals with the recycling of foundries sand (sorting quartz from bentonite by dry way). A literature survey is performed for collecting the existing methods on (magnetic, pneumatic or electrostatic) sorting and foundries sand. The mineralogical characterisation shows that clay is mainly concentrated in the form of products with size of 40 J. . Lm or below. The recycling method adopted here is based on electrostatic processes. The various tests performed in the laboratory demonstrate that it is feasible to recycle 50 % of the clay content in the dumped sand. Modeling of particle trajectory, based on Runge-Kutta method, consistently reproduces experimental data. Principal component analysis does not allow the dentification of a factor that solely controls the recovery rate
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Muller, John. "Etude du cycle biogéochimique du sélénium dans l'environnement". Nantes, 2008. http://www.theses.fr/2008NANT2082.
Testo completoAbstract (sommario):
Le but de ce travail est de déterminer le cycle biogéochimique du sélénium, et plus particulièrement des sélénites, dans un environnement proche de la surface. Pour cela, nous avons réalisé des études de sorption sur différentes phases minérales en système mono et multi-phasiques. Nous avons également réalisé des expériences pour étudier le devenir du sélénium dans un système-sol_plantes_microorganismes. (i) Les expériences de sorption des sélénites sur différentes phases minérales ont validé la méthode dite des « membranes de dialyse » et ont montré qu'il n'y avait pas d'additivité des capacités de sorption dans des systèmes à plusieurs phases minérales. La présence de Si aqueux relâché par la bentonite réduit la sorption du Se sur la goethite en occupant les sites de sorption. (ii) L'étude de l'influence des substances humiques (HA, FA) sur les capacités de sorption des différentes phases minérales vis-à-vis des sélénites a montré que ces substances diminuent la sorption du Se sur la goethite. De plus, ces expériences ont montré que les HA/FA ne complexent pas le sélénium. (iii) Les expériences « rhizoplants » nous ont permis de calculer des facteurs de transfert du Se des sols vers le ray-grass. Une application de ces facteurs de transfert dans un scénario de migration et de transfert du Se à partir d'un site de stockage des déchets HAVL, a donné une dose effective annuelle vers l'Homme comprise entre2,3 x 10-6 et 5,9 x 10-6 Sv. An-1The aim of this work is to determine the biogeochemical cycle of selenium, especially selenites, in a subsurface environment. To do so, we studied Se sorption on different mineral phases in single or multi-phase systems. We also conducted experiments to investigate the fate of selenium in a soil-plants microorganisms system. (i) Sorption experiments of selenites on different mineral phases validated the « dialysis membranes » method and showed that there was no additivity of the sorption capacity in systems composed of several minerals phases. The presence of aqueous Si released by bentonite reduced Se sorption on goethite by occupying the sorption sites. (ii) The study of the influence of humic substances (HA, FA) on the sorption capacities of different mineral phases has shown that these substances decrease Se sorption on goethite. Moreover, these experiments have shown that HA/FA do not complex selenium. (iii) « Rhizoplants experiments allowed us to calculate transfer factors of soil Se toward rye-grass. In a scenario of migration and transfer of Se from a radioactive waste disposal, the application of these transfer gave an annual effective dose to Humans comprised between 2,3 x 10-6 and 5,9 x 10-6 Sv. Y-1
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Molera, Marimon Mireia. "On the sorption and diffusion of radionuclides in bentonite clay". Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3390.
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Sunde, Marius. "Organic binder as a substitute for bentonite in ilmenite pelletization". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18840.
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TiZir Titanium & Iron produces high titania slag and high purity pig iron from ilmenite in Tyssedal. The ilmenite is pelletized before smelting. Bentonite is added to the ilmenite concentrate as a binder to give the pellets strength and durability. Bentonite consists mainly of silica and alumina, which are considered as impurities in the high titania slag production. The use of organic binder has therefore been suggested as a substitute for bentonite.This work has focused on developing knowledge on the pelletization process and investigating various organic binders.Two methods of agglomeration, pelletization and briquetting, have been used in this work. Three batches of pellets have been made using a laboratory scale pelletizing drum. Two organic binders, Peridur 300 and Peridur 330, have been tested and compared to pellets made with bentonite and without binder. Seven batches of briquettes have been made using a cylindrical mold and a piston. Three organic binders, Peridur 300, calcium lignosulfonate and a nano cellulose fibre have been tested and compared to briquettes made with bentonite and without binder. The characterization included drop number test (pellets only), compression strength and thermal treatment.Briquettes were employed because using pellets yielded large deviations in the results. These deviations were believed to stem from the varying geometry of the pellets and were substantially mitigated by the use of cylindrical briquettes. It was found that Peridur 300 is a potential alternative to bentonite. The findings from thermal treatment suggest that above 500 degrees celcius sintering takes over as the dominating binding mechanism. For green strength, increasing binder viscosity has a positive effect.
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Barclay, D. Scott. "Batch treatment of textile wastewaters with modified bentonite adsorbent blends". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0017/MQ55652.pdf.
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Park, Sang-il. "Thermal conductivity of bentonite-bonded molding sands at high temperatures". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/18386.
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Dzene, Liva. "Synthesis of Scleroglucan-Smectite Composite Based on Porto Santo Bentonite". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30638.
Testo completoAbstract (sommario):
In this thesis, a smectite rich bentonite ore deposit from Porto Santo Island (Portugal) was characterized and then applied to prepare clay-biopolymer nanocomposite material. Natural clay sample is mainly composed of Fe rich smectite, having also feldspar, calcite and magnetite-maghemite minerals. Both montmorillonite from the clay source repository (SWy-2) and the Porto Santo bentonite were used for the nanocomposite synthesis. An exocellular polysaccharide – scleroglucan was used as a biopolymer. The X-ray diffraction and transmission electron microscopy results show that smectite is well dispersed in the scleroglucan matrix with partial exfoliation. The study of various experimental parameters reveal that only the scleroglucan/clay mineral mass ratios determine the level of the clay sheets’ dispersion in the polymer matrix. Compared to SWy-2, the Porto Santo bentonite shows a smaller degree of dispersion within the polymer matrix, but nevertheless its potential outstanding mechanical properties could be of interest for further studies.
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Hurel, Charlotte. "Rétention d'éléments trace sur une bentonite : étude expérimentale et modélisation". Nice, 2002. http://www.theses.fr/2002NICE5801.
Testo completoAbstract (sommario):
Le stockage des déchets radioactifs en formation géologique est envisagé en France. L’altération des déchets peut mobiliser le polluant, qui pourrait alors migrer vers la géosphère. Des argiles sont envisageables comme barrière anti-pollution étant donnée leur faible perméabilité et leur forte capacité de rétention. Un modèle thermodynamique de complexation de surface basé sur le principe d’additivité est proposé pour prédire le comportement des polluants au contact des argiles. Ce principe permet une détermination indépendante de chaque paramètre du modèle, et limite l’ajustement de données corrélées entre elles. Il permet alors l’établissement d’une base de données d’adsorption associée au solide. Les prédictions obtenues sont en bon accord avec les données expérimentales, ce qui offre des perspectives encourageantes quant à l’utilisation de ce modèle en performance assessmentRadioactive waste storage in deep underground is studied in France. The alteration of the radioactive waste can mobilise the elements which can migrate to the geosphere. Clays (bentonite) are investigated as major materials constituting the barriers because of their low permeability and high retention capacity. A thermodynamic surface complexation model, based on the site additivity principle was investigated, in order to predict the adsorption behaviour of pollutants in contact with clay. The principle allows an independent determination of each parameter of the model, limiting the fitting procedure of correlated data, and it allows the use of an adsorption thermodynamic database for a solid. The predictions obtained were un good accordance with experimental data. The model could then be applied successfully in performance assessment