Articoli di riviste: "Clays"

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Lakevičs, Vitālijs, Līga Bērziņa-Cimdiņa, Augusts Ruplis e Juris Pelšs. "SORPTION ROPERTIES OF LATVIAN CLAYS AND ENVIRONMENTAL PROTECTION SURVEY". Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (3 agosto 2015): 222. http://dx.doi.org/10.17770/etr2009vol1.1100.

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The survey has been comprised in historical sequence. It has been attempted to group literature sources in a way that we consider to be the most relevant in the publication. Analysis of literature led to the following conclusions: during the last years most important and most advanced ways in investigations of Latvian clay surface characteristics have been found: Value determination of clay specific surface; Clay’s porous structure investigation; Cation exchange capacity determination; Characteristics of organoclays; Catalytic characteristics of Latvian clays; Practical usage of clays in waste water treatment; Usage of clays in adulterants elimination from vegetable oils; Clays as catalysts in of organic compound reactions; New type of sorbent from rapeseed oil treatment waste. Experimental measurements supplement data base about surface characteristics of Latvian clay samples.

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McBride, M. B. "Chemistry of Clays and Clay Minerals". Clays and Clay Minerals 36, n. 5 (1988): 480. http://dx.doi.org/10.1346/ccmn.1988.0360515.

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OLIS, ALEXANDER C. "Chemistry of Clays and Clay Minerals". Soil Science 147, n. 4 (aprile 1989): 309. http://dx.doi.org/10.1097/00010694-198904000-00012.

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Low, Philip F. "Chemistry of clays and clay minerals". Journal of Colloid and Interface Science 125, n. 1 (settembre 1988): 363–64. http://dx.doi.org/10.1016/0021-9797(88)90091-4.

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Yapaskurt, O. V., e V. I. Koporulin. "Conference on clays and clay minerals". Lithology and Mineral Resources 40, n. 2 (marzo 2005): 193–94. http://dx.doi.org/10.1007/s10987-005-0021-0.

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Drits, V. A., e B. B. Zvyagina. "International conference “Clays and Clay Minerals”". Lithology and Mineral Resources 42, n. 5 (settembre 2007): 501–2. http://dx.doi.org/10.1134/s0024490207050094.

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Hunter, Keith A. "Chemistry of clays and clay minerals". Geochimica et Cosmochimica Acta 52, n. 5 (maggio 1988): 1319. http://dx.doi.org/10.1016/0016-7037(88)90287-6.

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Muhammad, Abubakar, Karl-Christian Thienel e Sebastian Scherb. "Calcined Clays from Nigeria—Properties and Performance of Supplementary Cementitious Materials Suitable for Producing Level 1 Concrete". Materials 16, n. 7 (28 marzo 2023): 2684. http://dx.doi.org/10.3390/ma16072684.

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In this work, four naturally occurring (two kaolinite-rich and two smectite-rich) clay samples were collected from different areas around the Ashaka cement production plant, located in Gombe State, Nigeria and calcined in a laboratory. The mineralogical characterization of the clays was carried out by XRD. The hydration kinetics of the calcined clay–cement systems were monitored by isothermal calorimetry. Workability was determined using the flow table method. The reactivity of the calcined clays was determined from the solubility of Si and Al ions and the strength activity index. All calcined clays studied met the requirements of ASTM C618 for the use of natural pozzolans as a partial replacement for hydraulic cement. The metasmectite clays yielded a higher specific surface area, increased water demand, and less reactive Si and Al ions compared to the metakaolin clays. The two calcined clay groups require the addition of superplasticizer to achieve a workability class similar to the Portland cement mortar system. They can be used to replace Portland cement at replacement levels of up to 45%, in combination with limestone powder to form an LC3 cement, thereby achieving at least a “Level 1” reduction in greenhouse gas emissions.

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KOROLEV, V. А. "THE ECOLOGICAL ROLE OF CLAYS AND CLAY MINERALS". Engineering Geology World 14, n. 1 (15 giugno 2019): 60–71. http://dx.doi.org/10.25296/1993-5056-2019-14-1-60-71.

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The article considers the ecological role played by clays and clay minerals in the ecosystem and the biosphere as a whole. The value of clays and clay minerals in the origin of life on Earth and the formation of RNA are analyzed, due to the periodicity of the microstructure of these minerals, their physicochemical activity and sorption capacity with respect to amino acids, nucleotides, proteins and RNA. The processes of interaction of clay minerals with organic matter are considered, including under conditions of hydrothermal conditions, which have specific features that contribute to the origin of life. In addition, the ecological functions of the lithosphere due to clays and clay minerals were analyzed. It is shown that clays and clay minerals perform the most important ecological resource function, being a valuable mineral resource and mineral, participating in providing biota (including humans) with various mineral and energy resources of minerals, in providing biophilic resources, in providing renewable resources (water, oil and gas), in providing resources of the geological space, etc. Also, the clays perform an important ecological geochemical function, which consists in their participation in the geochemistry processes of the lithosphere and the formation of specific geochemical barriers that perform protective ecological functions on the migration routes of various contaminants. The ecological geodynamic function of clays consists in their influence on the development of endogenous and exogenous geological processes affecting the state and functioning of ecosystems. Finally, the participation of clays in ensuring the geophysical ecological function of the lithosphere consists in their influence on the formation of both natural and man-made geophysical fields in ecological-geological systems. Thus, clays and clay minerals have a great influence on ecological and geological systems, they are involved in the formation of all the most important ecological functions of the lithosphere: resource, geochemical, geodynamic and geophysical. Among them, the most significant is the role of clays and clay minerals in ensuring the resource ecological function of the lithosphere.

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Karstunen, Minna, e Mirva Koskinen. "Plastic anisotropy of soft reconstituted clays". Canadian Geotechnical Journal 45, n. 3 (marzo 2008): 314–28. http://dx.doi.org/10.1139/t07-073.

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The aim of the paper is to extend the experimental validation of the S-CLAY1 model, which is a recently proposed elastoplastic constitutive model that accounts for initial and plastic strain-induced anisotropy. Drained stress path controlled tests were performed on reconstituted samples of four Finnish clays to study the effects of anisotropy in the absence of the complexities of structure present in natural undisturbed clays. Each test involved several loading, unloading, and reloading stages with different values of stress ratio and, hence, induced noticeable changes in the fabric anisotropy. Comparisons between test results and model predictions with the S-CLAY1 model and the modified Cam clay model demonstrate that despite its simplicity, the S-CLAY1 model can provide excellent predictions of the behaviour of unstructured soil.

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Bastida, J., M. T. Lores, J. De la Torre, P. Pardo e A. M. López Buendía. "Modificación microestructural de minerales arcillosos en ball clays de Teruel mediante tratamiento térmico". Boletín de la Sociedad Española de Cerámica y Vidrio 45, n. 1 (28 febbraio 2006): 38–45. http://dx.doi.org/10.3989/cyv.2006.v45.i1.327.

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MANGO-ITULAMYA, Lavie A., Frédéric COLLIN, Pascal PILATE, Fabienne COURTEJOIE e Nathalie FAGEL. "Evaluation of Belgian clays for manufacturing compressed earth blocks". Geologica Belgica 22, n. 3-4 (3 dicembre 2019): 139–48. http://dx.doi.org/10.20341/gb.2019.002.

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This study aims to characterize Belgian clays in order to evaluate their use for manufacture of compressed earth blocks (CEB). Nineteen Belgian clay deposits were sampled in 56 sites and 135 samples were collected and analyzed. The analyses focus on the determination of particle size, plasticity, nature and mineralogy as the main characteristics for assessing the suitability of the raw clays to make CEB. These analyses allow for classifying the sampled clay deposits in three categories: clays that can be used unchanged to make CEB (2 clay deposits), clays that are suitable for the manufacture of CEB but require addition of sand and gravel particles (13 clay deposits) and clays that are suitable for the manufacture of CEB if they are mixed with other raw clays (4 clay deposits). In order to verify the use of these clays, five of them served as a model for making CEB. The strength of these bricks was evaluated by testing for compressive strength and abrasion resistance. The results of these tests confirm the suitability or not of the sampled clays for the manufacture of CEB.

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Pozo, Manuel, e José Calvo. "An Overview of Authigenic Magnesian Clays". Minerals 8, n. 11 (9 novembre 2018): 520. http://dx.doi.org/10.3390/min8110520.

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Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is not inherited. Transformation of precursor detrital minerals, a process also termed “neoformation by addition”, can be conducted whether throughout precipitation on pre-existing natural surfaces or transformation and reaction on pre-existing surfaces. Both processes have been recognized as effective mechanisms in the formation of Mg-clays, which mostly include 2:1 clay minerals, such as talc-kerolite and Mg-smectites, as well as fibrous clays (sepiolite, palygorskite). Authigenic Mg-clay minerals occur in both modern and ancient marine and non-marine depositional environments, although formation of these clays in hydrothermal continental and seafloor settings must be also outlined. Most favourable conditions for the formation of Mg-clays on earth surface are found in evaporitic depositional environments, especially where parent rocks are enriched in ferromagnesian minerals. In these settings, Mg-clays are important constituent of weathering profiles and soils and can form thick deposits of significant economic interest. Based on this review of authigenic clay deposits, we propose three geochemical pathways, mainly related to continental environments, for the origin of authigenic Mg-clays: formation of Al-bearing Mg-clays (pathway 1), formation of Al-free Mg clays (pathway 2) and formation of sepiolite from other Mg-clay minerals (pathway 3).

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Souto, Carlos Magno Rocha Almeida, Danielly Vieira Lucena, Clarice Oliveira Da Rocha, Maria Eduarda Da Silva Barbosa e Syane Marcelle Miranda. "Desempenho reológico e de filtração de fluidos de perfuração base óleo preparados com argilas bentoníticas provenientes do município de Boa Vista-PB". Revista Principia - Divulgação Científica e Tecnológica do IFPB 1, n. 51 (3 settembre 2020): 22. http://dx.doi.org/10.18265/1517-0306a2020v1n51p22-29.

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<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p>Bentonite clays are an essential input to the production of drilling fluids. One of the main consumer segments of bentonite clay is the oil industry, where it is used as a thixotropic agent in drilling fluids in oil wells, attributing to the fluids physical characteristics and specific chemical and rheological properties. According to Leal (2012), the physico-chemical and rheological properties must be carefully controlled so that the fluid can perform all its functions, such as cooling the drill, forming a layer of low permeability with the formation and keeping the solids in suspension, in order to ensure its good performance in drilling wells. Three samples of industrialized sodium bentonite clays from the Boa Vista-PB region were studied. For the organophilization of the clays will be used quaternary ammonium salt, the rheology was determined, and it was observed that it is possible to obtain formulations of oil-based fluid additives with clay.</p></div></div></div>

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Korolev, V. A. "BIOTIC COMPONENT OF CLAYSOILS". Gruntovedenie 1, n. 16 (gennaio 2021): 7–15. http://dx.doi.org/10.53278/2306-9139-2021-1-16-7-15.

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All kinds of micro- and macroorganisms live in the massifs of clay soils: plants living in (or on) clay soils are called pelitophytes (from the Greek πηλός - “clay” and phyton - “plant”), micro- and macroorganisms living in clays, or associated with clays, they are called pelitophiles (from the Greek πηλός - "clay" and φιλία - "love"), that is, "loving clays" or "prone to clays." The article analyzes these groups of organisms and describes their role in the formation of the properties of clay soils and ecological-geological systems.

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Katti, Dinesh R., Zillur R. Patwary e Kalpana S. Katti. "Modelling clay–fluid interactions in montmorillonite clays". Environmental Geotechnics 4, n. 5 (ottobre 2017): 322–38. http://dx.doi.org/10.1680/jenge.14.00027.

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Datsenko, L., M. Hanchuk, Yu Chebanova, S. Malyuta e O. Mazykina. "POLOGIVSKIY KAOLIN DEPOSIT: GEOLOGY, MINERAL AND CHEMICAL COMPOSITION, TECHNOLOGICAL PROPERTIES". Visnyk of Taras Shevchenko National University of Kyiv. Geology, n. 2(97) (2022): 74–84. http://dx.doi.org/10.17721/1728-2713.97.10.

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The area of the Pologivskiy deposit of kaolins and refractory clays is located on the border of two geological regions: the Azov crystalline massif and the Konksko-Yalynska depression. Precambrian crystalline rocks and sediments of the Cretaceous, Paleogene, Neogene, and Quaternary systems take part in the geological structure of the district. The geological structure of the district is based on the results of field exploration (23–25) and geological surveying works. Deposits of the Quaternary system are widespread in the territory and are similar to mantle on the underlying rocks. The lower border of the Quaternary system is formed at the base of the Berezanskiy climatolite in accordance with the Geological Map of Ukraine legend (the scale 1:200 000) of the 1996 Central Ukrainian series. The underlying rocks are red-brown Pliocene clays in most parts of the territory, in the rest there are rocks of crystalline basement of Cretaceous, Paleogene and Neogene systems. The thickness of the Quaternary deposits is 10–20 m. Deposits of the Novopetrivska Neogene suite are productive for the extraction of clays and kaolins, in the base of which the undivided deposits of the Upper Eocene (Kyivska suite) and Oligocene (Kharkivska suite) lie. These are coastal-marine deposits – marls, calcareous clays, siltstones, weakly cemented sandstones and glauconite quartz sands. The total thickness of the Kyivska and Kharkivska suites varies from 0,0 to 60–70 m. Clays and kaolins are characterized by almost the same mineral composition. Most of them are composed of fine-grained kaolinite, and quartz predominates among impurities. Accessory and ore minerals are represented by zircon, rutile, ilmenite and hematite. Quartz is present in clays and kaolins in the form of rolled, semirolled and unrolled grains. High-quality aluminosilicate products are obtained from the kaolins of the deposit. Pologivskiy kaolin can be used to make chamotte without the clay addition, as well as a binder. The ratio of chamotte and binder is 80–20 %. The refractories obtained in the laboratory meet the requirements of high density for Class A blast furnace bricks and other products of appropriate determination. Pologivskiy clays are recognized as suitable for the production of 100 % refractories, as well as a binder component instead of ChasovYarska clays. Products made entirely of semi-acid clay meet the requirements for semi-acid refractory products of class B. Pologivskiy kaolins and clays have long been used in refractory, machine-building, ceramic, cement and other industries.

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Efendiyeva, Zarifa J., Maral G. Aliyeva e Matanat J. Hamashayeva. "Possibility of complex use of bentonite clays and modeling of research processes". Journal of Geology, Geography and Geoecology 32, n. 2 (24 giugno 2023): 233–40. http://dx.doi.org/10.15421/112322.

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The efficient and complex use of resources of high quality bentonite clays, as well as the application of relatively low quality bentonite clays in accordance with their mineralogical and lithological properties are identified in the article. As Azerbaijan’s oil industry developed, interest in studying the geological structure of bentonite deposits increased. Prospects for bentonite production to reach 1-1.5 million tons of annual productivity in the next 40-50 years are related to the industrial development of the Daşsalakhli deposit, the largest in terms of resources (explored reserves are 180 million tons). The Dashsalakhli field is unique in terms of mineral quality and is one of the largest deposits in the world. Since the Dashsalakhli field has been researched and prepared for industrial development, and taking into account the demand of the world market, it is possible to increase the production and pro- cessing of bentonites by 1.5-2 times with the production of various commodity products in the republic. For this purpose, a unique and powerful “Azbentonite” processing enterprise equipped with modern equipment was established in Baku. One of the most important physical properties of bentonite clay which determines its industrial use is swelling. The swelling of clays is determined by their granulometric and mineral composition, as well as the content of absorbed cations. Massive bentonites have a relatively low density due to the significant moisture content, in most cases greater than 2.09 g/cm3. Attention was paid principally to the study of the degree swelling of the studied clay samples . The process of swelling in clays depends on their mineralogical composition. As is known, according to P.A. Rebinder, clays with a hard crystal lattice are less exposed to swelling. The elastic skeletal lattice of «Dashsalahli» bentonite clay, which is characteristic of other bentonite clays, causes the swelling process to intensify on contact with water. Bentonite clays are char- acterized by high water absorption or water retention capacity compared to other types of clay. One of the important natural properties of bentonites is their dispersibility, which depends on the type and amount of functionally modifiable clay cations .The more alkali metal (usually sodium) cations in the diffuse layer of bentonite particles, the higher the dispersion. In order to comprehensively study the physical and chemical properties of «Dashsalahli» bentonite clay, samples were taken from the northern, southern, western, eastern and central directions of the clay deposit, and research work was carried out. As a result of the research, it was established that «Dashsalahli» bentonite clay belongs to the class of small dispersed, alkali-based montmorillonite clays and is characterized by plastic texture. The composition of these clays is weakly carbonate and consists mainly of quartz and plagioclase minerals. Reconstructive diagnostic and electron-microscopic data of the corresponding montmorillonite showed that these clays have variable cation capacity. The analysis of «Dashsalahli» bentonite clay ultimately examined the use of this clay in the production of drilling fluids used in wells drilled in the oil industry and in other industries. Bentonite clays, as well as their processed products, have many special qualities and are widely used in certain leading sectors of the economy, as well as in many industries. The possibility of their application in high-quality detergent used in the steel casting industry, granulation of iron ore concentrate, drilling of deep wells, production of expanded clay in the construction industry, production of special purpose aluminum sheets, and their application in the oil refining, chemical , food , liquid and gas in- dustries was determined. The feature of using low-condition bentonite clays and opening rocks in various fields ensures the full use of this raw material and the complex development of the deposit. Currently, bentonite clays, especially their montmorillonite varieties, are considered an important raw material in the world market due to the use of bentonites in the production of iron ore pellets.

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O, Ademila, Ogunribido T. H. T e Abidoye J. M. "Geotechnical and geochemical appraisal of IFON clay, Southwestern Nigeria: Implications for industrial utilization". International Journal of Physical Research 7, n. 1 (5 maggio 2019): 11. http://dx.doi.org/10.14419/ijpr.v7i1.26336.

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Clays are geological materials of economic potential in the manufacturing and environmental industries. Geotechnical properties and geochemical composition of Ifon clay deposits in Ondo State, Nigeria were investigated with the aim of determining their economic potentials. The geotechnical investigation includes consistency limits, strength, permeability and firing tests, while, X-ray fluorescence (XRF) method was used for determination of the bulk elemental composition of the clays using standard techniques. Geotechnical appraisal of the clay deposits revealed that high proportion of clay size fractions (52.3 – 66.1%) makes the clays suitable in their natural state for industrial raw materials. Activity of the clays was found to be low at approximately 0.3 – 0.7 and classified as inactive clays. Unconfined compressive strength varies between 3.4 N/mm2 and 4.7 N/mm2 and moderate shrinkage values (≤ 12%) indicate that the clays could be used as building construction materials. Coefficient of permeability of 7.75 × 10-8 to 1.72 × 10-5 cm/sec described the clays as low to impermeable soils suitable as barrier soils. SiO2 (64.41 – 68.74%) and Al2O3 (22.98 – 28.45%) contents dominate the clay geochemistry followed by iron oxide, Fe2O3 (3.57 – 8.31%) content among other oxides in traces, imply that they originated from underlying basement rocks subjected to varying degree of weathering. Low MgO, CaO, K2O and Na2O indicate no expandable clay minerals in the clays. The clays show low heavy metal concentrations which guarantee their suitability as raw materials in chemical industries. Thus, Ifon clay deposits are suitable for the production of ceramics, refractory bricks, paper, paints, rubber and fertilizer.

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El Ouahabi, M., L. Daoudi e N. Fagel. "Mineralogical and geotechnical characterization of clays from northern Morocco for their potential use in the ceramic industry". Clay Minerals 49, n. 1 (marzo 2014): 35–51. http://dx.doi.org/10.1180/claymin.2014.049.1.04.

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AbstractThis study focuses on the mineralogical and geotechnical characterization of northern Moroccan clays from the Tangier and Tetouan areas and compares them with the main clay deposits used in the Moroccan ceramic industry (from Meknes, Fes, Salé and Safi regions). Sampled clays were analysed by X-ray diffraction on bulk and clay (<2 μm) fractions to identify the mineralogical assemblages of the clay outcrops. Further analyses were conducted to determine the particle size distribution (laser diffraction particle analyser), the total organic matter content (Loss- On-Ignition measurements) and the Atterberg limits of the raw clays. The study aims at investigating the spatial variability of the clay samples and at evaluating their potential application as raw materials in the ceramic industry.Tetouan and Tangier clays are characterized by diversified mineralogical assemblages (in particular a variable proportion of clay, quartz and calcite) compared with the Meknes, Fes, Salé and Safi clays (high clay content, quartz and calcite). The clay fraction of the Tetouan and Tangier samples is dominated by illite and kaolinite with variable amounts of chlorite, smectite and/or vermiculite. Illite is the dominant phase in the Meknes, Fes, Safi and Salé clays, but is associated with kaolinite. No direct relationship between the mineral assemblage composition and the lithology of the series was found.The clays materials studied consist generally of fine particles with medium to high plasticity and low organic matter content. Due to their mineralogy, grain-size distribution and plasticity the clays appear to be suitable as raw material for the growing Morocco ceramic industry.

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Oliveira, F. S., A. F. D. C. Varajão, C. A. C. Varajão e B. Boulangé. "A comparison of properties of clay minerals in isalteritic and in degraded facies". Clay Minerals 48, n. 5 (dicembre 2013): 697–711. http://dx.doi.org/10.1180/claymin.2013.048.5.03.

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AbstractThe mineralogical, geochemical and micromorphological features of an isalteritic clay facies, which originated from weathering of an anorthosite, were compared to those of clay facies derived from the degradation of a bauxite developed from the same rock. The isalteritic clay was formed by the hydrolytic alteration of plagioclase, whereas the degraded clays were formed by decomposition of gibbsite and neoformation of kaolinite. This resilification process resulted from the reintroduction of silica via the oscillation of the phreatic level and/or the decomposition of organic matter on the surface. The degradation process was gradual and yielded two different facies: (a) degraded clays with almost total decomposition of gibbsite, and (b) degraded clays with gibbsite nodules. Morphologically, the isalteritic clays differ from the degraded clays because they contain larger hexagonal and pseudo-hexagonal crystals. The degraded clays have more irregular crystal shapes, ranging from laths to anhedral shapes.

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Refai Kassab, Alaa El-Hosani, Azza Hassan Moubark, Waleed Hamdy Elkamash e Kamal Mohamed Hafez Ismail. "Shear Strength of Unsaturated Soils with Different Plasticity". Journal of University of Shanghai for Science and Technology 23, n. 11 (9 novembre 2021): 197–217. http://dx.doi.org/10.51201/jusst/21/11887.

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A series of shear box tests were conducted on four different types of soils in this study. The first set , (clay1) is the host clay, Middle Delta Nile clay “MDNC” which was obtained from Mid Delta Nile zone, Qalyubiyya Governorate, Egypt. The second set, (clay2) consists of the host clay MDNC but mixed with 40% sand. The third set of tests (clay3) was carried out on natural low plastic clay samples brought from El-Tal El-Kbeer area in Ismailia Governorate. The fourth set (clayey sand -SC) consists of 25% of the host clay MDNC mixed with 75% sand. The purpose is to predict the unsaturated shear strength for various soil types. The results illustrate that for clay1, clay2, and clay3, the relationships between the unsaturated shear strength and matric suction are approximated to two linear failure envelopes intersected at matric suction equals to plastic limit. Each segment has an angle of internal friction due to matric suction  b ranging from 1.80 o to 2.90o for the first zone and  b ranging from 0.28 o to 0.20o for the second zone. Meanwhile, for SC soil it appears to have one linear failure envelope for all saturation levels with angle of internal friction due to matric suction;  b=1.19 o.. Design- Expert® software applied the least square method (LSM) to fit a mathematical model for the experimental data. The Response Surface Methodology (RSM) of the program is used to predict the required model. The paper proposed two general equations to calculate the shear strength of unsaturated clays and one equation for granular soils, which are presented at the end of the paper with their coefficients.

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Incledion, Alexander, Megan Boseley, Rachael L. Moses, Ryan Moseley, Katja E. Hill, David W. Thomas, Rachel A. Adams, Tim P. Jones e Kelly A. BéruBé. "A New Look at the Purported Health Benefits of Commercial and Natural Clays". Biomolecules 11, n. 1 (5 gennaio 2021): 58. http://dx.doi.org/10.3390/biom11010058.

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Clays attributed to have medicinal properties have been used since prehistoric times and are still used today as complementary medicines, which has given rise to unregulated “bioceutical” clays to treat skin conditions. Recently, clays with antibacterial characteristics have been proposed as alternatives to antibiotics, potentially overcoming modern day antibiotic resistance. Clays with suggested antibacterial properties were examined to establish their effects on common wound-infecting bacteria. Geochemical, microscopical, and toxicological characterization of clay particulates, their suspensions and filtered leachates was performed on THP-1 and HaCaT cell lines. Cytoskeletal toxicity, cell proliferation/viability (MTT assays), and migration (scratch wounds) were further evaluated. Clays were assayed for antibacterial efficacy using minimum inhibitory concentration assays. All clays possessed a mineral content with antibacterial potential; however, clay leachates contained insufficient ions to have any antibacterial effects. All clay leachates displayed toxicity towards THP-1 monocytes, while clay suspensions showed less toxicity, suggesting immunogenicity. Reduced clay cytotoxicity on HaCaTs was shown, as many leachates stimulated wound-healing responses. The “Green” clay exhibited antibacterial effects and only in suspension, which was lost upon neutralization. pH and its interaction with clay particle surface charge is more significant than previously understood to emphasize dangers of unregulated marketing and unsubstantiated bioceutical claims.

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Nassetti, G. "Heavy Clays". Key Engineering Materials 53-55 (gennaio 1991): 794–96. http://dx.doi.org/10.4028/www.scientific.net/kem.53-55.794.

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Poncelet, G. "Pillared Clays". Clays and Clay Minerals 38, n. 2 (1990): 223. http://dx.doi.org/10.1346/ccmn.1990.0380217.

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Farfan-Torres, EM, e P. Grange. "Pillared Clays". Journal de Chimie Physique 87 (1990): 1547–60. http://dx.doi.org/10.1051/jcp/1990871547.

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PETKEWICH, RACHEL. "HEALING CLAYS". Chemical & Engineering News 86, n. 17 (28 aprile 2008): 48–49. http://dx.doi.org/10.1021/cen-v086n017.p048.

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28

Churchman, Jock, Dean Hesterberg e Balwant Singh. "Soil clays". Applied Clay Science 64 (agosto 2012): 1–3. http://dx.doi.org/10.1016/j.clay.2012.06.012.

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29

Robert, M., M. Hardy e F. Elsass. "Crystallochemistry, properties and organization of soil clays derived from major sedimentary rocks in France". Clay Minerals 26, n. 3 (settembre 1991): 409–20. http://dx.doi.org/10.1180/claymin.1991.026.3.09.

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AbstractThe nature, crystallochemistry, organization and surface properties of soil clays derived from the most representative sedimentary formations of France are described, using qualitative and quantitative mineralogical methods and high resolution transmission microscopy (HRTEM). The main results show that soil clays differ significantly from reference clays. Even when 2:1 phyllosilicates are dominant, the clays always contain multimineral phases. The smectitic component is dioctahedral and of beidellite type. Soil clay organization is specific: all the clay particles have a short lateral extension and few layers (mean 5 layers, and even mono-layers occur). The superposition of such small particles leads to the formation of what are called “texturally interstratified minerals” which are dominant in soil clays. Exchange and surface properties (high ratio of external surface to total surface area), are related to clay organization.

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30

Manning, D. A. C. "Environmental Interactions of Clays: Clays and the Enironment". Clay Minerals 34, n. 2 (1999): 379–80. http://dx.doi.org/10.1180/claymin.1999.034.2.15.

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31

Biswas, Bhabananda, Jérôme Labille e Benedicte Prelot. "Clays and modified clays in remediating environmental pollutants". Environmental Science and Pollution Research 27, n. 31 (23 luglio 2020): 38381–83. http://dx.doi.org/10.1007/s11356-020-09828-4.

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32

Lefebvre, Guy, Karol Rohan e Serge Douville. "Erosivity of natural intact structured clay: Evaluation". Canadian Geotechnical Journal 22, n. 4 (1 novembre 1985): 508–17. http://dx.doi.org/10.1139/t85-071.

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Previous studies on erodibility of cohesive soil are briefly reviewed and it is concluded that experimental observations have been mainly concerned with remolded and reconsolidated or weathered clays. The structure effect, which is considered important in the behaviour of natural intact clay, especially for Eastern Canadian clays, has not up to now been really considered in the evaluation of clay erodibility. This paper proposes a new laboratory technique for the study of the erodibility of natural intact clays and presents results of a testing program on three Canadian clays. The results indicate that Canadian structured clays are very resistant to erosion if intact and unweathered. Erosion is not taking place at the clay particle level but rather by the pulling out of larger elements composed of sand or silt grains or of clay aggregates. The pulling out of clay aggregates appears related to defects in the clay matrix, such as microfissures or planes of weakness associated with bedding. Key words: erosivity, intact clay, rate of erosion, tractive force, erosivity test, microstructure, macrostructure.

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33

Chorom, M., P. Rengasamy e RS Murray. "Clay dispersion as influenced by pH and net particle charge of sodic soils". Soil Research 32, n. 6 (1994): 1243. http://dx.doi.org/10.1071/sr9941243.

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The effect of changing pH on the dispersion of clay from sodic soils was investigated in relation to changes in net charge on clay particles. A positive relationship was obtained between pH and the percentage of dispersible clay for each soil clay. The percentage increase in net negative charge was also positively correlated with pH. However, the slopes of these relationships varied between soil clays. In general, the net negative charge was the primary factor in clay dispersion and the pH affected clay dispersion by changing the net charge on clay particles. In comparing the values for pure clay minerals quoted in the literature with soil clays having similar mineralogy, it was found that soil clays had higher flocculation values. This is shown to be due to higher net negative charge on soil clays than the corresponding values for pure clay minerals found in the literature. The effect of soil organic matter in enhancing the net negative charge probably contributes to the higher charge on soil clays. The critical dispersion concentration for clay dispersion from soil aggregates was lower than the flocculation values observed for the separated soil clays. The separated soil clays had high negative charge due to exposure of surfaces which were originally bonded in the aggregates. The dispersive potential of a number of Alfisols, Oxisols, Aridisols (calcareous soils) and Vertisols collected from different parts of Australia was highly correlated with soil pH. The relationship with CEC was poor because CEC was estimated at a pH different to the natural pH of the soil. This study has brought out the importance of pH in the management of dispersive soils.

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34

Anyukhina, Anna V., Valerii V. Seredin, Andrey V. Andrianov e Tatiana Yu Khludeneva. "Influence of Heat Treatment of Clays on Their Adsorption of Methylene Blue Dye". Недропользование 21, n. 2 (1 aprile 2021): 52–57. http://dx.doi.org/10.15593/2712-8008/2021.2.1.

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The adsorption activity of soils largely depends on their composition and properties and, first of all, on the specific surface area and energy potential of clay particles. For the formation of "specified" properties, including adsorption, various methods of clay activation have been developed: thermal, ultraviolet, ultrasonic, mechanical, acidic, alkaline. However, despite the published data, the issues of the influence of heat treatment on the formation of the clays properties, including adsorption ones, have not been sufficiently studied. In this regard, an assessment was made of the of clays thermal activation effect on their adsorption activity for the methylene blue dye. Experimental and theoretical studies have shown that the change in the adsorption activity of clays is associated with the degree of their heat treatment. When clays are treated with temperatures up to 200° C, energy centers on the surface of structural elements are activated, which leads to an increase in the clays adsorption in terms of methylene blue by 12–24%; with an increase in the processing temperature of clays to 450–960° С, the processes of their (clays) structural transformation change, which reduces the adsorption activity of clays by 11–16 times. In addition, the influence of the clays saturation degree with water vapor on their adsorption activity has been established. During the heat treatment of clays and their partial saturation with water vapor, water molecules occupy part of the energy centers on the surface of the particles; therefore, the particles have a sufficient energy potential, which is realized in the form of high values of their adsorption to methylene blue. During the clays thermal treatment and their complete saturation with water vapor, the charges on the surface of the particles are mostly compensated by water molecules. Water molecules, entering the inter-package space, compensate charges on the surface of the packages and minerals, which are realized in the form of clay swelling processes. Swelling processes lead to an increase in the size of structural elements, which manifests itself in the form of a decrease in the specific surface of clays. Therefore, clays completely saturated with water vapor are less active adsorption than clays partially saturated with water vapor.

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35

Nisticò, Roberto. "A Comprehensive Study on the Applications of Clays into Advanced Technologies, with a Particular Attention on Biomedicine and Environmental Remediation". Inorganics 10, n. 3 (21 marzo 2022): 40. http://dx.doi.org/10.3390/inorganics10030040.

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In recent years, a great interest has arisen around the integration of naturally occurring clays into a plethora of advanced technological applications, quite far from the typical fabrication of traditional ceramics. This “second (technological) life” of clays into fields of emerging interest is mainly due to clays’ peculiar properties, in particular their ability to exchange (capture) ions, their layered structure, surface area and reactivity, and their biocompatibility. Since the maximization of clay performances/exploitations passes through the comprehension of the mechanisms involved, this review aims at providing a useful text that analyzes the main goals reached by clays in different fields coupled with the analysis of the structure-property correlations. After providing an introduction mainly focused on the economic analysis of clays global trading, clays are classified basing on their structural/chemical composition. The main relevant physicochemical properties are discussed (particular attention has been dedicated to the influence of interlayer composition on clay properties). Lastly, a deep analysis of the main relevant nonconventional applications of clays is presented. Several case studies describing the use of clays in biomedicine, environmental remediation, membrane technology, additive manufacturing, and sol-gel processes are presented, and results critically discussed.

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36

Meethong, Nonglak, Wanwisa Pattanasiriwisawa, Weenawan Somphon, Waraporn Tanthanuch e Sutham Srilomsak. "Properties of Dan Kwian, Sukhothai and Ratchaburi Pottery Clays Fired at 700 and 900 °C". Key Engineering Materials 608 (aprile 2014): 47–61. http://dx.doi.org/10.4028/www.scientific.net/kem.608.47.

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Dan Kwian, Sukhothai and Ratchaburi pottery clays are economically important pottery clays. They are well known in the Thai ceramic society for making Dan Kwian pottery, Sawankhalok pottery and Dragon jars, respectively. There have been several studies of these pottery clays. However, few of them used statistics to analyze their results. This work is a comparative study of the compositions and properties of these three pottery clays using statistical software to analyze the results. Results show that the major components of these pottery clays are SiO2 and Al2O3. The Modulus of Rupture (MOR) of each pottery clay fired at 700°C are not significantly different. Sukhothai pottery clay fired at 900°C has a higher MOR and bulk density while its porosity, water absorption and apparent specific gravity are less than those of the Dan Kwian and Ratchaburi pottery clays fired at the same temperature. Additionally, the current study developed regression equations for estimating the properties of all pottery clays under study. Finally, it was found that the L*, a*, b* and reflectance spectra of all pottery clays increased when firing temperature was increased from 700 to 900°C.

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37

De Souza Santos, P. "The Use of Clay Particle Morphology Studies to Characterize Industrial Clay Deposits: Examples from Brazil". Clay Minerals 28, n. 4 (dicembre 1993): 539–53. http://dx.doi.org/10.1180/claymin.1993.028.4.05.

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AbstractThe use of transmission electron microscopy in association with other methods is described for the characterization of Brazilian industrial clays, especially kaolinitic-halloysitic clays. Examples are presented from: (a) tubular 7 Å-halloysites and the characterization of mixtures with ordered and disordered kaolinites in residual china clays; (b) tubular kaolinitic clay from Piedade, São Paulo; (c) platey 10 Å-halloysite from Poģos de Caldas, Minas Gerais; (d) rolled forms similar to 10 Å-tubular halloysite formed by repeated K Ac intercalation in well ordered kaolinite; (e) use of particle shape and size of kaolinite crystals in the São Simão, São Paulo ball clays as orientation for good sanitaryware ball clays; (f) characterization of gibbsite crystals in high alumina gibbsite/kaolinite clays; (g) antigorite as a clay mineral; (h) electron optical studies of thermal phase transformations involving tubular kaolinite, halloysites, antigorite, chrysotile, talc and pyrophyllite mono crystals.

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38

Singh, Nakshatra Bahadur. "Clays and Clay Minerals in the Construction Industry". Minerals 12, n. 3 (27 febbraio 2022): 301. http://dx.doi.org/10.3390/min12030301.

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Clay is a naturally occurring material that can be converted to different clay minerals through thermal treatments, and can be used for the development of different products. Clays and clay minerals have been used for different applications in different sectors. Detailed information regarding the applications of these materials in the construction industry are described. Clay has been used as a supplementary cementitious material in Portland cement (OPC) mortars and concretes. These minerals decrease raw materials and CO2 emissions during the production of Portland cement clinker and, at the same time, increase the compressive strength of concrete at a later age. Therefore, they are conducive to the sustainability of construction materials. A new type of cement, Limestone calcined clay cement (LC3), and a binding material geopolymer cement have also been developed using clay minerals. The properties of these binders have been discussed. Applications of clay products for making bricks have are also described in this article.

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39

Solin, S. A. "CLAYS AND CLAY INTERCALATION COMPOUNDS:Properties and Physical Phenomena". Annual Review of Materials Science 27, n. 1 (agosto 1997): 89–115. http://dx.doi.org/10.1146/annurev.matsci.27.1.89.

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40

Knodel, PC, A. Sridharan, BT Jose e BM Abraham. "Determination of Clay Size Fraction of Marine Clays". Geotechnical Testing Journal 14, n. 1 (1991): 103. http://dx.doi.org/10.1520/gtj10197j.

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41

Dai, J. "Surface modification of clays and clay–rubber composite". Applied Clay Science 15, n. 1-2 (settembre 1999): 51–65. http://dx.doi.org/10.1016/s0169-1317(99)00020-4.

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42

Picarelli, L., e C. Di Maio. "Deterioration processes of hard clays and clay shales". Geological Society, London, Engineering Geology Special Publications 23, n. 1 (2010): 15–32. http://dx.doi.org/10.1144/egsp23.3.

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43

Pannirselvam, Muthu, R. K. Gupta, S. N. Bhattacharya e Robert A. Shanks. "Intercalation of Montmorillonite by Interlayer Adsorption and Complex Formation". Advanced Materials Research 29-30 (novembre 2007): 295–98. http://dx.doi.org/10.4028/www.scientific.net/amr.29-30.295.

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Clays are essentially composed of crystalline particles of one or more members of a small group of minerals. The ability of clays to intercalate certain organic substances has been known for a very long time. There is a scope in these clay structures for isomorphous replacement, that is, for substitution of Na+ by cations of similar size but usually of lower valency. This research aims at identifying suitable additives for pretreatment of clay and determining the effect of different classes of compounds (intercalants) on the d-spacing expansion of clay layers. This paper addresses a different approach to ion exchange for treatment of sodium montmorillonite, with different functional groups: aldehyde, ether, alcohol, glycol, and stearates. The results were compared with commercially available clays, Cloisite 25A and Cloisite 30B (Southern Clay Products), which are montmorillonite (MMT) clays intercalated with quaternary ammonium salts. The d-spacing increment in this research was consistent with the d-spacing achieved in commercially available clays. Future research will be to utilize the treated clay to produce polymer composites.

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44

Zaccaron, Alexandre, Vítor de Souza Nandi, Marcelo Dal Bó, Michael Peterson, Elídio Angioletto e Adriano Michael Bernardin. "Characterization and use of clays and argillites from the south of Santa Catarina State, Brazil, for the manufacture of clay ceramics". Clay Minerals 55, n. 2 (giugno 2020): 172–83. http://dx.doi.org/10.1180/clm.2020.23.

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AbstractSix clays from various deposits were studied for their use in the production of structural clay products. The clays were characterized using chemical (X-ray fluorescence), mineralogical (X-ray diffraction) and thermal (differential scanning calorimetry/thermogravimetry) analyses. Particle-size distribution was determined by laser diffraction, plasticity by the Pfefferkorn method and the residue by the sieve-size method. Next, specimens were formed by extrusion and characterized by their linear thermal shrinkage (on drying and firing), water absorption, bulk density, porosity and compressive strength. The clays were, in general, suitable for the manufacture of structural ceramics, mainly bricks. The clays from flooded pits (AV1 and AV2) were classified as floodplain clays and alluvial clays. The clays mined in mountainous regions (AM1 and AM2, as well as AV1) were characterized as siliceous clays due to the abundance of free SiO2 phases.

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45

Paramith, Tika, Johnner P Sitompul e Hyung Woo Lee. "The effect of organobentonites from spent bleaching earth (SBE) and commercial bentonite on nanocomposite properties". International Journal of Engineering & Technology 7, n. 4 (5 settembre 2018): 2000. http://dx.doi.org/10.14419/ijet.v7i4.15317.

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This paper concerns on synthesis of nanocomposites consisting of Poly(lactic acid) (PLA) and clays. Two types of clays were regenerated organobentonite and commercial organobentonite. PLA and clays were melt extruded using single-screw extruder. The extruded compound was pelletized, then hot pressed using compression molding machine. Regenerated organobentonite was obtained from regeneration of spent bleaching earth (SBE) using solvent extraction and oxidation method. Afterwards, regenerated SBE modified by organic compound. While, commercial organobentonite was directly modified of commercial bentonite using organic compound. In this study, nanocomposites were prepared with varying compositions of clays from 0% to 5% (by weight). Experimental results show that partially exfoliated nanocomposites structure was shown by X-ray diffraction analyses. In addition, the effect of clays on morphology structure, mechanical, barrier, and biodegradable properties were analyzed. The utilization of clays in nanocomposite increases mechanical properties at low clay compositions. Furthermore, PLA-clay nanocomposites show better barrier and biodegradable properties compared to that of the neat PLA.

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46

Williams, Lynda B. "Geomimicry: harnessing the antibacterial action of clays". Clay Minerals 52, n. 1 (marzo 2017): 1–24. http://dx.doi.org/10.1180/claymin.2017.052.1.01.

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AbstractA decade of research on clays that kill human pathogens, including antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA), has documented their common characteristics. Worldwide, ∼5% of clays tested to date are antibacterial when hydrated. Most antibacterial clays are from hydrothermally altered volcanics, where volcanogenic fluids produce minerals containing reduced metals. Ferruginous illite-smectite (I-S) is the most common clay mineral, although kaolins dominate some samples. Antibacterial clay mineral assemblages may contain other reduced Fe minerals (e.g. pyrite) that drive production of reactive oxygen species (H2O2, •OH, •O2−) and cause damage to cell membranes and intracellular proteins. Ion exchange can also cause loss of bacterial membrane-bound Ca2+, Mg2+ and PO43–.Critically important is the role of clays in buffering the hydration water pH to conditions where Al and Fe are soluble. A nanometric particle size (<200 nm) is characteristic of antibacterial clays and may be a feature that promotes dissolution. Clay interlayers or the lumen of tubular clays may absorb reduced transition metals, protecting them from oxidation. When the clays are mixed with deionized water for medicinal applications, these metals are released and oxidized.Different antibacterial clays exhibit different modes of action. The minerals may be a source of toxins, or by adsorption may deprive bacteria of essential nutrients. In the field, the pH and Eh (oxidation state) of the hydrated clay may help to identify potential antibacterial clays. If the pH is circum-neutral, toxic metals are not soluble. However, at pH < 5 or >9 many metals are soluble and the oxidation of transition metals increases the Eh of the suspension to >400 mV, leading to bacterial oxidation.Understanding the antibacterial mechanism of natural clay may lead to design of new treatments for antibiotic-resistant bacteria, with potential applications in wound dressings, medical implants ( joint replacements, catheters), animal feed stocks, agricultural pathogens, and production of antibacterial building materials. This research exemplifies how ‘geomimicry’ (copying geochemical processes) may open new frontiers in science.

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47

Lite, M. C., E. C. Tănăsescu, L. O. Secăreanu, I. M. Săndulache, O. Iordache e E. Perdum. "REVIEW ON DIFFERENT TYPES OF CLAY AND THEIR USE AS ANTIMICROBIAL AGENTS FOR TEXTILES TREATMENT". TEXTEH Proceedings 2021 (22 settembre 2021): 321–27. http://dx.doi.org/10.35530/tt.2021.51.

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Traditional uses of clay as medicine started in prehistoric times (Aboriginal times). Natural clays have been used in ancient and modern medicine, but the mechanism that makes certain clays lethal to bacterial pathogens has not been yet identified. The aim of this paper is to identify the proper clays that could be used in textile industry for improving textiles` functionality, based on the information extracted from literature. It is important, to differentiate between the properties that make a clay ‘healing’, versus what makes it ‘antibacterial’. So far, literature is abundant in reports regarding ‘healing’ clays, but, when tested against pathogens in vitro and compared to controls, they do not appear to have bactericidal properties. The studies carried out up to this point established that the physical adsorption of water and organic matter is the main feature which leads to healing properties of clays; however, the chemical interaction between clay and bacteria has received less attention. Clay properties, with potential application in medicine, have recently been started to be investigated and the results indicate that certain natural clays can have noticeable and extremely specific effects on microbial colonies. Further studies will be directed towards the characterization of the selected ‘claytextile’ pairs.

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Usmanov, Safar, Rustamjon Anorov, Izzat Eshmetov, Dilnozakhan Salikhanova e Babur Adizov. "The effect of mechanical activation methods on the properties of local clays and waste bentonites". E3S Web of Conferences 390 (2023): 05035. http://dx.doi.org/10.1051/e3sconf/202339005035.

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One of the most important indicators of mechanical activation of clay minerals is the effect of activation time on the strength of the mixture. One of the most important parameters in the preparation of drilling fluid based on clays is their ability to swell, and the effect on the swelling of clays during mechanical activation was studied. One of the most important parameters of clays used in the preparation of drilling fluids resistant to thermomechanical effects is their colloidal index. Therefore, the effect of mechanical activation time on the colloidal index of these clays was studied. The method of activation of bentonites and analysis of their rheological parameters was studied. In the process of mechanical activation of clays, their activation of chemical reagents created conditions for modifying the increased specific surface area of clay materials.

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Wang, Zhijing (Zee), Hui Wang e Michael E. Cates. "Effective elastic properties of solid clays". GEOPHYSICS 66, n. 2 (marzo 2001): 428–40. http://dx.doi.org/10.1190/1.1444934.

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Clay minerals are perhaps the most abundant materials in the earth’s upper crust. As such, their elastic properties are extremely important in seismic exploration, seismic reservoir characterization, and sonic‐log interpretation. Because little exists in the literature on elastic properties of clays, we have designed a method of measuring effective elastic properties of solid clays (clays without pores). In this method, clay minerals are mixed with a material with known elastic properties to make composite samples. Elastic properties of these clay minerals are then inverted from the measured elastic properties of the composite samples using the weighted Hashin‐Shtrikman average. Using this method, we have measured 66 samples of 16 types of clays. In this paper, we present a comprehensive data set of elastic properties of solid clays that commonly occur in, or are related to, petroleum reservoirs. Although uncertainties (up to 10%) exist, the data set reported here is by far the most comprehensive set of elastic properties in the literature. These data can be used potentially in modeling the seismic properties of clay‐bearing rocks.

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Radosavljevic, Slobodan, Jovica Stojanovic, Ana Radosavljevic-Mihajlovic, Nikola Vukovic, Srdjan Matijasevic, Mirjana Stojanovic e Vladan Kasic. "Ceramic clays from the western part of the Tamnava Tertiary Basin, Serbia: Deposits and clay types". Annales g?ologiques de la Peninsule balkanique, n. 75 (2014): 75–83. http://dx.doi.org/10.2298/gabp1475075r.

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Based on geological, mineralogical, physical, chemical and technological investigations in the Tamnava Tertiary Basin near Sabac town (western Serbia), deposits of ceramic clays were studied. These ceramic clays are composed of kaolin-illite with a variable content of quartz, feldspars, mica, iron oxides and hydroxides, and organic matter. Four main types of commercial clays were identified: i) red-yellow sandy-gravely (brick clays); ii) grey-white poor sandy (ceramic clays); iii) dark-carbonaceous (ceramic clays); and iv) lamellar (?interspersed?) fatty, poor sandy (highly aluminous and ferrous clays). Ceramic clays are defined as medium to high plastic with different ranges of sintering temperatures, which makes them suitable for the production of various kinds of materials in the ceramic industry.

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