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1
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.
Testo completoAbstract (sommario):
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.
2
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.
Testo completoAbstract (sommario):
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.
3
Lescinskis, Oskars, Ruta Švinka e Visvaldis Švinka. "Common and Different in Latvian Clay Minerals". Key Engineering Materials 762 (febbraio 2018): 268–72. http://dx.doi.org/10.4028/www.scientific.net/kem.762.268.
Testo completoAbstract (sommario):
Clays are materials consisting of clay minerals and non-clay minerals. Some applications allow to use raw clay others require to separate clay minerals from non-clay minerals. Clay mineral fraction is considered to be a nanofraction. Description and characterization of 3 different Latvian clay nanosized minerals from 3 different geological periods (clay Liepa from Devonian period, clay Vadakste from Triassic period and clay Apriki from Quaternary period) are summarized. The main mineral in these clays is illite, however the presence of kaolinite is observed and its quantity depends on geological period in which clays formed. Nanosized clay mineral particles were obtained using sedimentation method. Comparison of mineralogical composition, BET nitrogen adsorption, zeta potential, DTA/TG analysis and FTIR spectra is given. XRD phase analysis results were very close to each other and shows that mineral of illite is more than that of kaolinite. BET nitrogen adsorption data shows that clay minerals of Apriki has the highest specific surface area (81 m2/g), whereas clay minerals of Vadakste has it the lowest (43 m2/g). Zeta potential values for clay minerals Apriki, Liepa and Vadakste are-40.9 mV, -49.6 mV and-43.0 mV, respectively. DTA analysis and FTIR spectra show similar tendencies for all 3 clay minerals.
4
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.
Testo completoAbstract (sommario):
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.
5
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.
Testo completoAbstract (sommario):
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.
6
Lakevičs, Vitālijs, Valentīna Stepanova, Santa Niedra, Inga Dušenkova e Augusts Ruplis. "Thixotropic Properties of Latvian Illite Containing Clays". Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (6 agosto 2015): 133. http://dx.doi.org/10.17770/etr2013vol1.813.
Testo completoAbstract (sommario):
Thixotropic properties of Latvian Devonian and Quaternary clays were studied. Dynamic viscosity of the water clay suspensions were measured with a rotating viscometer. Influence of concentration, pH and modifiers on the thixotropic clay properties was analyzed. It was found that Latvian clays have thixotropic properties. Stability of clay suspensions is described with the thixotropy hysteresis loop. Increasing the speed of the viscometer rotation, dynamic viscosity of the clay suspension decreases. It was found that the solid phase concentration and mineralogical composition make an impact on the thixotropy of clays. Decreasing the solid phase concentration in the clay suspensions from 50% to 25%, dynamic viscosity decreases proportionally to the solid phase concentration. It was found that modifying clay suspensions with carboxymethyl cellulose (0,1g) increases concentration of structure forming. In the same time, modifying of clay suspensions with calcified soda (0,1g) decreases the structure forming concentration. Dependence of pH value from the solid phase concentration slightly decreases with the clay phase concentration increasing in the suspension.
7
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.
Testo completoAbstract (sommario):
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.
8
Chu, Chengfu, Zilong Wu, Yongfeng Deng, Yonggui Chen e Qiong Wang. "Intrinsic compression behavior of remolded sand–clay mixture". Canadian Geotechnical Journal 54, n. 7 (luglio 2017): 926–32. http://dx.doi.org/10.1139/cgj-2016-0453.
Testo completoAbstract (sommario):
A series of incremental loading oedometer tests was conducted on pure clays and sand–clay mixtures with various sand/clay ratios and clay mineral compositions. The void indexes Iv and IvH were introduced to evaluate their intrinsic compressibility. Test results revealed that Iv was more suitable for depicting the compression behavior of pure clays than IvH; whereas, for the compressibility of sand–clay mixtures, the normalized compression line by using Iv was obviously different from that of pure clays and traditional soils due to the presence of sand particles. Therefore, a four-phase analysis framework of sand–clay mixtures was introduced to unify the intrinsic compression behavior of soils with and without sands. It was found that the updated clay void index Ivc parameter was effective to unify the soil’s compression behavior by excluding the influence of sand particles in clays before the sand skeleton formation. After the formation of the sand skeleton, the cluster particles change the stress distribution of mixtures, leading to less stress being applied on the clay matrix and thus the bifurcation of the intrinsic compression behavior.
9
Mohd Amin, M. F., S. G. J. Heijman e L. C. Rietveld. "Clay-biodegradable polymer combination for pollutant removal from water". Drinking Water Engineering and Science Discussions 8, n. 2 (23 settembre 2015): 177–96. http://dx.doi.org/10.5194/dwesd-8-177-2015.
Testo completoAbstract (sommario):
<p><strong>Abstract.</strong> In this study, a new treatment alternative is investigated to remove micropollutants from wastewater effectively and in a more cost-effective way. A potential solution is the use of clay in combination with biodegradable polymeric flocculants. Flocculation is viewed as the best method to get the optimum outcome from the combination of clay with starch. Clay is naturally abundantly available and relatively inexpensive compared to the conventional adsorbents used. Experimental studies were carried out with four different clays to select the best clay for further optimisation. The atrazine removal achieved is in the range of 10–99 % based on the clay concentration of 10–50 g L<sup>−1</sup>. Optimisation of the best clay performer leads towards atrazine reduction of > 99 % with a dosage of 100 mg L<sup>−1</sup>. The best and underperforming clays were then tested in other experiments with the addition of cationic starch flocculants. In this experiment, the addition of a polymer increased the atrazine removal for the underperforming clay to 46 % with only 10 mg L<sup>−1</sup> clay dosages. The clay flocculation test was also performed to test the flocculation efficiency of clays by the polymer. Approximately 80–84 % of the clay is flocculated, which shows exceptional flocculation efficiency in removing both clays and atrazine from the water matrices.</p>
10
Barker, W. W. "Bacterial Trace Fossils in Eocene Kaolin". Proceedings, annual meeting, Electron Microscopy Society of America 43 (agosto 1985): 238–39. http://dx.doi.org/10.1017/s0424820100118114.
Testo completoAbstract (sommario):
Spheroidal electron-dense masses averaging two microns in diameter comprise up to 20% of a thin Eocene grey kaolin in the upper part of the Huber Fm. near Wrens, Georgia. TEM and SEM reveal that the microspheroids consist of tangentially oriented kaolinite platelets enclosing much finer, delicate intergrowths of secondary authigenic minerals.Many types of bacteria and algae produce mucopolysaccharidal exudates which can attach clay platelets. Clay-clad microorganisms are especially common in marine and estuarine environments, where high ionic strength compresses the electric double layer of kaolinite sufficiently for van der Waals forces to aid its attachment to exudates. Maclean and Smart found clay-clad prokaryotic cells in recent estuarine sediments. Avnimelech, et al. demonstrated mutual flocculation of algae and clay upon addition of electrolyte. Because the size and structure of the clay-clad microspheroids in the Eocene kaolin closely resembles the clay-clad bacteria in recent marine muds, they are interpreted as trace fossils of bacteria.
11
Suttikul, Supaluk, Kanyarat Ano e Kedsarin Pimraksa. "Effect of Calcium Hydroxide Content on Pozzolanic Reaction of Calcined Clays: Their Mechanical Properties and Microstructures". Materials Science Forum 1034 (15 giugno 2021): 161–68. http://dx.doi.org/10.4028/www.scientific.net/msf.1034.161.
Testo completoAbstract (sommario):
The research aimed to investigate the effect of calcium hydroxide content on pozzolanic reaction of calcined clays. Pozzolanic reaction of calcined clay was determined in terms of its mechanical properties, phase development and microstructures. Three clay minerals (two kaolinitic clays and kaolinite-montmorillonite clay) were chosen to produce pozzolanic materials via calcination at temperature of 700 °C to allow dehydroxylation of clay minerals. Ratios of calcium hydroxide to calcined clays were varied from 0.1 to 0.5. Mixing water contents or liquid to solid ratios (0.62, 0.75 and 0.80) and curing times (7 and 28 days) were also studied. It was found that calcium aluminosilicate hydrate (stratlingite) could be formed after pozzolanic reactions of all clay minerals. The development of stratlingite agreed with the strength development showing the highest compressive strength at 26 MPa (28 days) when kaolinite-montmorillonite clay was used as pozzolanic material and the ratio of calcium hydroxide to calcined clay was 0.5.
12
Lefebvre, Guy, Karol Rohan e Jean-Pierre Milette. "Erosivity of intact clay: Influence of the natural structure". Canadian Geotechnical Journal 23, n. 4 (1 novembre 1986): 427–34. http://dx.doi.org/10.1139/t86-072.
Testo completoAbstract (sommario):
Erodibility drill hole tests have been conducted on three Eastern Canadian clays on intact structured specimens, on specimens destructured by consolidation, and on remolded and reconsolidated specimens. The intact structured clay is highly resistant to erosion; links between particles can resist high tractive stresses. The resistance to erosion is drastically decreased however when the clay is destructured by consolidation or remolding. The decrease varies from one clay to the other; after consolidation the resistance to erosion is very low for the St. Hyacinthe clay but still high for the St. Leon clay. The clays are even more erodible after remolding and reconsolidation, but important differences are still observed between the clays tested. The pore water salinity appears as a significant factor in the understanding of the different behaviour observed after destructuration of the clay by consolidation or remolding. Key words: erosivity, rate of erosion, critical tractive stress, structured clay, destructuration, consolidation, remolding, pore water salinity.
13
SHEKHAWAT, M. S. "THERMO GRAVIMETRIC AND DIFFERENTIAL THERMAL ANALYSIS OF CLAY OF WESTERN RAJASTHAN (INDIA)". International Journal of Modern Physics: Conference Series 22 (gennaio 2013): 458–65. http://dx.doi.org/10.1142/s2010194513010519.
Testo completoAbstract (sommario):
The paper presents the study of thermo gravimetric and differential thermal analysis of blended clay. Western part of Rajasthan (India) is rich resource of Ball clays and it is mainly used by porcelain, sanitary ware, and tile industry. The quality and grade of clay available in the region vary from one deposit to other. To upgrade the fired colour and strength properties, different variety of clays may be blended together. The paper compares the results of thermal analysis one of blended clay B2 with reference clay of Ukraine which is imported by industries owners. The result revealed that the blended clay is having mineral kaolinite while the Ukrainian clay is Halloysite.
14
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.
Testo completoAbstract (sommario):
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.
15
Elsafi, Mohamed, Yousry Koraim, Mansour Almurayshid, Fahad I. Almasoud, M. I. Sayyed e I. H. Saleh. "Investigation of Photon Radiation Attenuation Capability of Different Clay Materials". Materials 14, n. 21 (7 novembre 2021): 6702. http://dx.doi.org/10.3390/ma14216702.
Testo completoAbstract (sommario):
This work aims to experimentally report the radiation attenuation factors for four different clays (red, ball, kaolin and bentonite clays) at four selected energies (emitted from Am-241, Cs-137, and Co-60). The highest relative difference in the mass attenuation coefficient (MAC) is equal to −3.02%, but most of the other results are much smaller than this value, proving that the experimental and theoretical data greatly agree with each other. From the MAC results, the shielding abilities of the clay samples at 0.060 MeV follow the order of: bentonite > red > ball > kaolin. Thus, at low energies, the bentonite clay sample provides the most effective attenuation capability out of the tested clays. The half value layer (HVL) increases as energy increases, which suggests that, only a thin clay sample is needed to sufficiently absorb the radiation at low energies, while at higher energies a thicker sample is needed to shield the same amount of high energy radiated. Furthermore, bentonite clay has the lowest HVL, while the kaolin clay has the greatest HVL at all energies. The radiation protection efficiency (RPE) values at 0.060 MeV are equal to 97.982%, 97.137%, 94.242%, and 93.583% for bentonite clay, red clay, ball clay, and kaolin clay, respectively. This reveals that at this energy, the four clay samples can absorb almost all of the incoming photons, but the bentonite clay has the greatest attenuation capability at this energy, while kaolin clay has the lowest.
16
Meftah Elgubbi, Hana, Siti Salhah Othman e Farah Wahida Harun. "Modification of kaolinite clay using benzyltriethylammonium chloride as a surfactant: Preparation and characterization". International Journal of Engineering & Technology 9, n. 4 (22 ottobre 2020): 850. http://dx.doi.org/10.14419/ijet.v9i4.31088.
Testo completoAbstract (sommario):
Natural kaolinite clay from Perak, Malaysia with cation exchange capacity (CEC) of 2.5 meq/100g was modified using cationic surfactant, benzyltriethylammonium chloride (BTEA-Cl), at 0.5, 1.0, 1.5 and 2.0 times the CEC. A number of techniques, namely energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption were then used for characterization of the kaolinite and/or organo-modified kaolinite clays. The presence of alkyl groups as a result of successful intercalation of cationic surfactant within the organo-kaolinite layers of the clay was exhibited by the FTIR spectra. The SEM microphotographs exhibited good dispersion of the natural clay particles and slight agglomeration in the organo-modified clay particles. XRD patterns showed that the d001 spacing of the natural kaolinite clay increased from 7.12 Å to between 7.20 - 7.34 Å for the organo-modified clays. Following the BET nitrogen adsorption-desorption technique, all clay samples were of Type IV with narrow hysteresis loops. Surface areas of the clays showed drastic decrease from (25.34 m2/g) for natural kaolinite clay to between 5.90 - 13.11 m2/g for organo-modified clays. The results suggested that modification of natural kaolinite clay using cation surfactant had successfully occurred. The modification can therefore be further applied for alteration and improvement of the properties of natural clays for various industrial applications.
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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.
Testo completoAbstract (sommario):
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.
18
Kumari, Neeraj, Chandra Mohan e Arvind Negi. "An Investigative Study on the Structural, Thermal and Mechanical Properties of Clay-Based PVC Polymer Composite Films". Polymers 15, n. 8 (18 aprile 2023): 1922. http://dx.doi.org/10.3390/polym15081922.
Testo completoAbstract (sommario):
The present study aims to explore the impact of pristine and surfactant-modified clays (montmorillonite, bentonite and vermiculite) on the thermomechanical properties of a poly (vinyl chloride) (PVC) polymer film. Initially, clay was modified by employing the ion exchange method. The modification of clay minerals was confirmed by the XRD pattern and thermogravimetric analysis. Pristine PVC polymer film and clay (montmorillonite, bentonite and vermiculite)-based PVC polymer composite films were fabricated using solution casting. The ideal dispersion of surfactant-modified organo-clays was observed in the PVC polymer matrix due to the hydrophobic nature of modified clays. The resultant pure polymer film and clay polymer composite film were characterized using XRD and TGA, and their mechanical properties were determined using a tensile strength tester and Durometer. From the XRD pattern, the intercalation of the PVC polymer film was found in the interlayer of organo-clay while exfoliation or partial intercalation and exfoliation were observed for pristine clay mineral-based PVC polymer composite films. Thermal analysis indicated a lowering of the decomposition temperature of the composite film as clay promotes the thermal degradation temperature of PVC. Improvement in the tensile strength and hardness was found to be more frequent in the case of organo-clay-based PVC polymer films, which is only due to the hydrophobic nature of organ clays, resulting in greater compatibility with the polymer matrix.
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Behrami, Esad, e Vahid Avdiu. "The Process and Kinetics of Pesticide Desorption from Clay as a Function of Cleaning Polluted Waters". Processes 11, n. 4 (11 aprile 2023): 1180. http://dx.doi.org/10.3390/pr11041180.
Testo completoAbstract (sommario):
This study presents an investigation into the desorption process of pesticides, namely benalaxyl, atrazine, dimethoate, and methomyl, from aqueous solutions in natural Brari clay (Tirana) located at 41°21′14.49″ N and 19° 50′17.74″ E and Dardha clay (Korça) located at 40°31′16.59″ N and 20°49′33.69″ E. The desorption process was fast, where in the first 2 hours of contact, 99.1% of atrazine was desorbed from Brari clay, and 90.1% of atrazine was desorbed from Dardha clay. In addition, in the first 2 hours of contact, 80.3% of benalaxyl was desorbed from pear clay and 79.2% of benalaxyl from Brari clay; 96.2% of methomyl and 81.2% of dimethoate were desorbed. According to the acquired curves, the desorption process began with the dominance of methomyl from Brari clay, followed by dimethoate from Brari clay, dimethoate from Dardha clay, atrazine from Brari clay, benalaxyl from Brari clay, benalaxyl from Dardha clay, and lastly atrazine from Dardha clay. Hence, compared to Dardha clay, less pesticide underwent desorption with Brari clay. Researchers immediately wondered how long (time) these pesticides would remain in the corresponding clays following the adsorption process, so the study of the kinetics of the desorption of pesticides from clay is of special interest. The kinetics of the pesticides atrazine, benalaxyl, dimethoate, and methomyl (all at a concentration of 25 mg/L) desorbing from natural Brari and Dardha clays are presented here.
20
Sayouba, Sandwidi, Haro Kayaba, Dabilgou Téré, Sinon Souleymane, Sanogo Oumar, Koulidiati Jean e Bere Antoine. "Search for Qualified Soil for the Production of Low-Energy Biobased Composite Materials". Asian Journal of Physical and Chemical Sciences 11, n. 3 (24 agosto 2023): 64–73. http://dx.doi.org/10.9734/ajopacs/2023/v11i3207.
Testo completoAbstract (sommario):
The development of earth-based bio-sourced materials requires a thorough analysis of the study soil. For the present study, we took five (05) soil samples from a tunnel-digged quarry in the layer between 0.5 m and 5 m : white clay (MSB-BL), red clay (MSB-RG), weak clay or sandy clay (MSB-FB), strong clay (MSB-FR) and mixture (MSB-ME). To verify the quality of these five (05) soils samples, their intrinsic properties were determined at the National Building and Public Works Laboratory (LNBTP). These included grain size, clay content, specific weight, loss on ignition and moisture content. These analyses revealed that MSG-RG and MSG-BL clays have fine fractions of 64.28% and 47.85% respectively; clay fractions of 27.51% and 20.61% respectively; and methylene blue values in the range (6;8). Their plasticity indices are in the range (20;40). These two (02) clays thus meet the requirements in terms of granularity, and their relatively high clay fraction will favor their adhesion with admixtures such as plant fibers. What's more, the particle size distribution of these clays is within the ideal CRAterre range for soils used in the manufacture of BTC or adobes, so they are all eligible.
21
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.
Testo completoAbstract (sommario):
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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Murray, H. H. "Applied clay mineralogy today and tomorrow". Clay Minerals 34, n. 1 (marzo 1999): 39–49. http://dx.doi.org/10.1180/000985599546055.
Testo completoAbstract (sommario):
AbstractThe clay minerals kaolin, smectite and palygorskite-sepiolite are among the world's most important and useful industrial minerals. Clay minerals are important in a number of geological applications such as stratigraphic correlations, indicators of environments of deposition and temperature for generation of hydrocarbons. In agriculture, the clay minerals are a major component of soils and determinant of soil properties. The clay minerals are important in construction where they are a major constituent in brick and tile. The physical and chemical properties of the clay minerals determine their utilization in the process industries.What about tomorrow? Processing techniques will be improved and new equipment will be available so that improved clay mineral products will be available. Pillared clays and nanocomposites will become important. Further developments in organoclay technology and surface treatments will provide new usages for these special clays. Tomorrow will see further growth and utilization of the clay minerals.
23
Oscarson, D. W. "Comparison of Measured and Calculated Diffusion Coefficients for Iodide in Compacted Clays". Clay Minerals 29, n. 2 (giugno 1994): 145–51. http://dx.doi.org/10.1180/claymin.1994.029.2.01.
Testo completoAbstract (sommario):
AbstractAn understanding of the behaviour of contaminants in compacted clays is important in assessing the effectiveness of clay-based barrier materials used in many waste containment strategies. Here the diffusion and sorption behaviour of I− with selected compacted clays is examined (129I is a relatively long-lived radioisotope present in high-level nuclear fuel waste.) Diffusion coefficients, D, and distribution coefficients, Kd, were measured for I− with four clays: bentonite, Lake Agassiz clay (a glacial lake clay composed mainly of smectite, illite, kaolinite, and quartz), interstratified illite-smectite, and kaolinite. For the diffusion experiments the clays were compacted to a dry bulk density, ρ, of ∼1.2 Mg m−3. The mean measured D values, Dm, were as follows: bentonite, 310 µm2 s−1; Lake Agassiz clay, 0.62 µm2 s−1; illitesmectite, 190µm2s−1; and kaolinite, 74µm2s−1. The measured values were compared with those calculated, Dc, from the following model: D=Doτan/(n + ρKd), where Do is the diffusion coefficient in pure bulk water, τa the apparent tortuosity factor, and n the solution-filled porosity of the clay. Except for the Lake Agassiz clay, where Dm was about an order of magnitude lower than Dc, the Dm and Dc values agreed within a factor of about two. The Lake Agassiz clay has a markedly higher organic carbon content than the other three clays, and this could affect τa, which may be overestimated in the model.
24
Orosz, Viktor, István Kocserha, Róbert Géber e Csilla Paróczai. "Examination of Tile Industrial Usability of High-Quartz Content Clay". Materials Science Forum 659 (settembre 2010): 67–72. http://dx.doi.org/10.4028/www.scientific.net/msf.659.67.
Testo completoAbstract (sommario):
The Hungarian roof tile plants settle near a discovered clay mine in every case thus they work with different content clays. Examining characteristics of certain clay layers is needed to ensure stable product quality. Some clay layers with significantly different content occur among the presently used ones, which need an extensive examination for the production of good quality items. Results of high quartz content clay usability examinations are shown in this paper. The aim of examinations is to determine the usability of frequently occurring high quartz content clays. In the course of tests high quartz content clay mineral was mixed in increased amounts to clay mineral for roof-tile production provided by the industrial partner. Shrinkage, porosity and mechanical properties were examined as a function of mixing ratio.
25
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.
Testo completoAbstract (sommario):
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.
26
Baldi, G., T. Hueckel e R. Pellegrini. "Thermal volume changes of the mineral–water system in low-porosity clay soils". Canadian Geotechnical Journal 25, n. 4 (1 novembre 1988): 807–25. http://dx.doi.org/10.1139/t88-089.
Testo completoAbstract (sommario):
The effect of temperature on the volumetric strains of the clay skeleton and clay – water system has been examined experimentally. Heating tests at (various) constant effective stress and isotropic loading tests at (various) constant temperatures were performed on low-porosity clays under drained conditions. The results indicate that the thermal expansion of adsorbed water in these clays is significantly lower than that of free water. Depending on the effective pressure, the clay skeleton may undergo either compression or expansion. Key words: nuclear waste isolation, clay, low porosity, thermal strain, adsorbed water.
27
Griffiths, Scott, Carl H. Mesarich, Benedetta Saccomanno, Abraham Vaisberg, Pierre J. G. M. De Wit, Russell Cox e Jérôme Collemare. "Elucidation of cladofulvin biosynthesis reveals a cytochrome P450 monooxygenase required for anthraquinone dimerization". Proceedings of the National Academy of Sciences 113, n. 25 (6 giugno 2016): 6851–56. http://dx.doi.org/10.1073/pnas.1603528113.
Testo completoAbstract (sommario):
Anthraquinones are a large family of secondary metabolites (SMs) that are extensively studied for their diverse biological activities. These activities are determined by functional group decorations and the formation of dimers from anthraquinone monomers. Despite their numerous medicinal qualities, very few anthraquinone biosynthetic pathways have been elucidated so far, including the enzymatic dimerization steps. In this study, we report the elucidation of the biosynthesis of cladofulvin, an asymmetrical homodimer of nataloe-emodin produced by the fungusCladosporium fulvum. A gene cluster of 10 genes controls cladofulvin biosynthesis, which begins with the production of atrochrysone carboxylic acid by the polyketide synthase ClaG and the β-lactamase ClaF. This compound is decarboxylated by ClaH to yield emodin, which is then converted to chrysophanol hydroquinone by the reductase ClaC and the dehydratase ClaB. We show that the predicted cytochrome P450 ClaM catalyzes the dimerization of nataloe-emodin to cladofulvin. Remarkably, such dimerization dramatically increases nataloe-emodin cytotoxicity against mammalian cell lines. These findings shed light on the enzymatic mechanisms involved in anthraquinone dimerization. Future characterization of the ClaM enzyme should facilitate engineering the biosynthesis of novel, potent, dimeric anthraquinones and structurally related compound families.
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Cajetan, Okolo Chidiebere, Ezechukwu O.A., Olisakwe C.O., Ezendokwelu C.E. e Umunna Chike. "CHARACTERIZATION OF ELECTRICAL PORCELAIN INSULATORS FROM LOCAL CLAYS". International Journal of Research -GRANTHAALAYAH 3, n. 1 (31 gennaio 2015): 26–36. http://dx.doi.org/10.29121/granthaalayah.v3.i1.2015.3050.
Testo completoAbstract (sommario):
In this thesis, the characterization of electrical porcelain insulators based on local clays has been investigated. Test samples were made by varying the quantities of feldspar and silica required to form a mouldable plastic body with each clay sample. The clay samples were bisque fired which is to 900°C and glazed before it was fired to 1250°C after air-drying. An electrical property such as dielectric strength (breakdown voltage) was determined for each test sample that survived the high temperature. The composition for optimum properties from Ekwulobia and Iva Valley clays each is at composition 3 of 60% clay, 25% feldspar and 15% silica; while for Nawfija clay, the composition for optimum properties was 50% clay, 30% feldspar and 20% silica. Porcelain insulators containing 50-70% clay, 20-30% feldspar and 10-20% silica were found to have requisite properties that make them suitable for domestic production of porcelains insulators from the clay samples studied.
29
Joo, Incheol, e Jongmuk Won. "Influence of Sand Grain Size and Clay Mineralogy on Suffusion of Sand-Clay Mixtures". Journal of the Korean Society of Hazard Mitigation 23, n. 2 (30 aprile 2023): 91–99. http://dx.doi.org/10.9798/kosham.2023.23.2.91.
Testo completoAbstract (sommario):
Suffusion is a type of internal erosion caused by the detachment of fine particles. Additionally, continuous suffusion reduces the stability of geotechnical infrastructures. In this study, the impact of clay mineralogy and sand grain size on the suffusion of sand-clay mixtures was investigated using two-dimensional laboratory experiments on nine different sand-clay mixtures made of three types of sands (K3, K4, and K5) and clays (kaolinite, illite, and bentonite). The breakthrough curve for each sample was obtained for the top/middle/bottom outlets of the designed cell to measure and analyze the amount of detached clay. It was observed that as the sand grain size decreased, the amount of detached clay was more and clays with kaolinite exhibited greater suffusion than those with illite. Bentonite exhibited the lowest amount of detached clay owing to its high swelling potential. The influence of clay mineralogy and sand grain size on the suffusion has been discussed based on the obtained breakthrough curves.
30
Karpiński, B., e M. Szkodo. "Clay Minerals – Mineralogy and Phenomenon of Clay Swelling in Oil & Gas Industry". Advances in Materials Science 15, n. 1 (1 marzo 2015): 37–55. http://dx.doi.org/10.1515/adms-2015-0006.
Testo completoAbstract (sommario):
Abstract Among the minerals found in the earth's crust, clay minerals are of the widest interest. Due to the specific properties such as plasticity, absorbing and catalytic properties clay minerals are used in many industries (oil & gas, chemistry, pharmacy, refractory technology, ceramics etc.). In drilling, a phenomenon of swelling clays is frequently observed. It has an important impact on the cementing quality. During the last few decades clays have been the subject of research on a scale unprecedented in the history of mineralogy. This paper presents review literature on mineralogy of clay minerals and phenomenon of swelling in oil and gas industry. Unique ion exchange properties and clay swelling mechanisms are also considered.
31
Jaskulski, Roman, Daria Jóźwiak-Niedźwiedzka e Yaroslav Yakymechko. "Calcined Clay as Supplementary Cementitious Material". Materials 13, n. 21 (23 ottobre 2020): 4734. http://dx.doi.org/10.3390/ma13214734.
Testo completoAbstract (sommario):
Calcined clays are the only potential materials available in large quantities to meet the requirements of eco-efficient cement-based materials by reducing the clinker content in blended cements or reducing the cement content in concrete. More than 200 recent research papers on the idea of replacing Portland cement with large amounts of calcined clay are presented and discussed in detail. First, the fundamental information about the properties and structure of clay minerals is described. Then, the process of activation and hydration of clays is discussed, including the methods of pozzolanic activity assessment. Additionally, various testing methods of clays from different worldwide deposits are presented. The application of calcined clay in cement and concrete technology is then introduced. A separate chapter is devoted to lime calcined clay cement. Then an influence of calcined clay on durability of concrete is summarized. Finally, conclusions are formulated.
32
Ogawa, Atsushi, Atsushi Takai, Takumi Shimizu e Takeshi Katsumi. "Effects of temperature on consolidation and consistency of clayey soils". E3S Web of Conferences 205 (2020): 09010. http://dx.doi.org/10.1051/e3sconf/202020509010.
Testo completoAbstract (sommario):
This study focuses on the effects of temperature on the consolidation property and consistency of clay for thermal improvement of soft clay ground. Although it is already known that an increase in temperature can accelerate consolidation of clay, the degree of the temperature effect has not yet been generalized between various clays. In this study, a series of one-dimensional consolidation tests at different temperatures (17, 23, 35, 50, and 65°C) using 2 processed clays and 3 natural clayey soils dredged at ports are presented. To evaluate the temperature effect on soil consistency, which might affect the consolidation behavior, atterberg limits of the clays were also evaluated at different temperatures. As a result, it was confirmed that, although the temperature effect on consistency limits varies depending on the type of clay, the consolidation coefficient increases with increase in temperature in all the clay soils tested.
33
Umudi, E. Q., E. Adaikpo, I. E. Obukohwo, J. Igborgbor e A. Egheneji. "Evaluation of Kaolin as Adsorbent for Chlorine Reduction in Seawater from Forcados/Ogulagha Axis of Southwest Delta State, Nigeria". Journal of Applied Sciences and Environmental Management 26, n. 2 (3 maggio 2022): 237–42. http://dx.doi.org/10.4314/jasem.v26i2.10.
Testo completoAbstract (sommario):
This paper evaluates the use of three Nigerian clay types Otorho (OT, Abbi (BB) and Umutu (UM) as adsorbent for the reduction of chlorine in seawater from (Forcados/Ogulagha aix in Southwest Delta State using XRD X ray diffraction and Atomic Absorption Spectrophotometer. The alumino silicate nature of the clays was confirmed by the presence of SiO2 and Al2O3 and the presence of other elements (Na, K, Ca, Mg, Fe and Ti) in trace quantities. Percolation rate studies showed that clay UN had the lowest while OT had the highest. Clays fortified with stone pebbles in ratios 1:3 in columns in one flow-through and three flow troughs were used in different arrangements. Fortified clay (UM) gave the highest percentage reduction of 99.9%, BB clay 98.0% and OT clay 99.2%. The results showed that clay UM removed >99% of chloride.
34
Elsafi, Mohamed, Mirvat Fawzi Dib, Hoda Ezzelddin Mustafa, M. I. Sayyed, Mayeen Uddin Khandaker, Abdullah Alsubaie, Abdulraheem S. A. Almalki, Mahmoud I. Abbas e Ahmed M. El-Khatib. "Enhancement of Ceramics Based Red-Clay by Bulk and Nano Metal Oxides for Photon Shielding Features". Materials 14, n. 24 (19 dicembre 2021): 7878. http://dx.doi.org/10.3390/ma14247878.
Testo completoAbstract (sommario):
We prepared red clays by introducing different percentages of PbO, Bi2O3, and CdO. In order to understand how the introduction of these oxides into red clay influences its attenuation ability, the mass attenuation coefficient of the clays was experimentally measured in a lab using an HPGe detector. The theoretical shielding capability of the material present was obtained using XCOM to verify the accuracy of the experimental results. We found that the experimental and theoretical values agree to a very high degree of precision. The effective atomic number (Zeff) of pure red clay, and red clay with the three metal oxides was determined. The pure red clay had the lowest Zeff of the tested samples, which means that introducing any of these three oxides into the clay will greatly enhance its Zeff, and consequently its attenuation capability. Additionally, the Zeff for red clay with 10 wt% CdO is lower than the Zeff of red clay with 10 wt% Bi2O3 and PbO. We also prepared red clay using 10 wt% CdO nanoparticles and compared its attenuation ability with the red clay prepared with 10 wt% PbO, Bi2O3, and CdO microparticles. We found that the MAC of the red clay with 10 wt% nano-CdO was higher than the MAC of the clay with microparticle samples. Accordingly, nanoparticles could be a useful way to enhance the shielding ability of current radiation shielding materials.
35
Romdhane, Dalila Fkih, Yosra Satlaoui, Rawya Nasraoui, Abdelkrim Charef e Rim Azouzi. "Adsorption, Modeling, Thermodynamic, and Kinetic Studies of Methyl Red Removal from Textile-Polluted Water Using Natural and Purified Organic Matter Rich Clays as Low-Cost Adsorbent". Journal of Chemistry 2020 (6 maggio 2020): 1–17. http://dx.doi.org/10.1155/2020/4376173.
Testo completoAbstract (sommario):
Clay minerals have large surface areas that contribute to their high adsorption capacity. Pure clays were often used. However, their prices remain expensive. However, the natural clay minerals that are locally available can have economic and environmental benefits for textile wastewater treatment. The tested natural clays had given low removal yields. Therefore, we wanted to test particular rich organic matter clay for adsorbing azo dye, which is a very toxic molecule. In order to make the use of this clay type have a better efficiency for removal of this dye from the polluted waters, the optimal conditions had been specified. The results indicated that advised conditions were as follows: 5 min was the contact time of dye-clay; the better adsorbent masses were 0.25 g and 0.5 g per 100 ml solution for raw (ANb) and purified clays (ANp), respectively; the initial dye concentrations were 1 gL−1 for raw clay and 50 mgL−1 for purified clay; pH solution had any effect on the yield of dye removal only when raw clay was used; however, acid environment was advised when purified clay was the adsorbent and for the two tested clays about 20–30°C was the better solution temperature. X-Ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analysis confirmed that functional groups of clay adsorbed the dye. Langmuir maximum adsorption capacities of ANb and ANp were found to be 397 mgg−1 and 132.3 mgg−1 at pH 7 and 5, respectively. Raw and chemically activated samples gave similar results. Adsorption of ANb and ANp data showed better agreement with the pseudo-second-order kinetic model. Thermodynamic parameters of the two adsorbents confirmed that the adsorption was endothermic (ΔH > 0) and spontaneous (ΔG0 < 0). Energy level was high when purified clay was used; however, it was significantly lower when the adsorbent was raw clay. Therefore, it was likely that adsorption by carbonates and organic matter involved small energy amounts. Comparing between these and other previous results, Jebel Louka natural clay type is better recommended for MR removal from textile wastewater, since the removal yield was about 98%. Hence, this tested clay type could provide an alternative low-cost material that could be used in treatment of the textile wastewater rich in MR and the obtained adsorption model and desorption tests provided a background for pilot and industrial scale applications.
36
Rouhani, Hadi, Fatola Farhadi, Mahsa Akbari Kenari, Effat Eskandari e Seeram Ramakrishna. "Selection of suitable bentonite and the influence of various acids on the preparation of a special clay for the removal of trace olefins from aromatics". Clay Minerals 56, n. 3 (settembre 2021): 185–96. http://dx.doi.org/10.1180/clm.2021.32.
Testo completoAbstract (sommario):
AbstractAcid-activated clays are inexpensive materials that are used extensively in the removal of unsaturated compounds on an industrial scale. The performance of bentonitic clays in removing these compounds relies heavily on the types of raw clays and acids used in the activation process. In this work, we report on the removal of olefins from aromatic streams by bentonitic clays activated via two different routes. After preliminary tests of four different natural clays, the best clay was selected in terms of it having high swelling index, cation-exchange capacity, specific surface area and suspension stability values. Activation was achieved with hydrochloric acid (HCl) and sulfuric acid (H2SO4), and olefin removal was evaluated after holistic clay characterization by means of X-ray diffraction, X-ray fluorescence, Brunauer–Emmett–Teller (BET) specific surface area analysis, ζ-potential analysis, Fourier-transform infrared (FTIR) spectroscopy after treatment with pyridine, scanning electron microscopy and transmission electron microscopy. The increased basal spacing, replacement of H+ with interlayer cations and retained structural stability of the clay after acid treatment contributed to the improvement of olefin removal for HCl-activated clay. The HCl-activated clay was more efficient in terms of olefin removal than its H2SO4-activated counterpart, removing up to 90% of olefin components after 40 h. Based on pyridine-FTIR spectra and quantitative measurement of the acidic properties of the samples, HCl treatment increased the total number acid sites (Brønsted and Lewis) by approximately ninefold compared to the pristine natural clay and by approximately fourfold compared to the H2SO4-activated clay.
37
Cotecchia, Federica, Simona Guglielmi, Francesco Cafaro e Antonio Gens. "Micro to macro investigation of clays advising their constitutive modelling - part I". Soils and Rocks 47, n. 3 (2 marzo 2024): e2024011723. http://dx.doi.org/10.28927/sr.2024.011723.
Testo completoAbstract (sommario):
This keynote lecture discusses the results of a long lasting experimental research, devoted to the investigation of clay microstructure and its evolution upon loading. Micro-scale analyses, involving scanning electron microscopy, image processing, mercury intrusion porosimetry and swelling paths to test the clay bonding, are presented on clays subjected to different loading paths, with the purpose of providing experimental evidence of the processes at the micro-scale which underlie the clay response at the macro-scale. Data from the literature on clays of different classes, either soft or stiff, are compared to original results on two stiff clays, Pappadai and Lucera clay, both in their natural state and after reconstitution in the laboratory. The results presented herein allow building a conceptual model of the evolution of clay microstructure upon different loading paths, providing microstructural insights into the macro-behaviour described by constitutive laws and advising their mathematical formalization in the framework of either continuum mechanics or micro-mechanics. For editorial purposes, the research results are presented in two parts. The first part, presented in this paper, concerns the results for reconstituted clays, whereas a second part, concerning the corresponding natural clays, is discussed in a second companion paper.
38
Apkar'yan, A. S., e T. Yu Sablina. "Investigation of the properties of overburden clays from the Kornilovskoye deposit of the Tomsk region". Izvestiya vysshikh uchebnykh zavedenii. Fizika, n. 7 (2022): 35–41. http://dx.doi.org/10.17223/00213411/65/7/35.
Testo completoAbstract (sommario):
Analytical and laboratory-technological studies of overburden clays of the Kornilovskoye deposit in the Tomsk region have been carried out. The chemical composition, mineral composition, granulometric composition, plasticity and refractoriness of clays have been determined. The sensitivity of clay raw materials to drying, apparent density, water absorption, shrinkage, mechanical characteristics of samples from clay raw materials have been investigated. The possibilities of using clay in various industries are determined.
39
Danish, Aamar, Ermedin Totiç, Muhammed Bayram, Mücahit Sütçü, Osman Gencel, Ertuğrul Erdoğmuş e Togay Ozbakkaloglu. "Assessment of Mineralogical Characteristics of Clays and the Effect of Waste Materials on Their Index Properties for the Production of Bricks". Materials 15, n. 24 (13 dicembre 2022): 8908. http://dx.doi.org/10.3390/ma15248908.
Testo completoAbstract (sommario):
Significant research investigations on the characteristics of unexplored clay deposits are being conducted in light of the growing need for clay in the ceramic industry and the variable chemistry of clays. Parallel to this, the generation of waste materials like fly ash, ferrochrome slag, and silica fume is also increasing, responsible for environmental degradation. This paper aims to study the mineralogical properties of pure clays (one specimen from Siberia and five specimens from different locations in Turkey), and the effect of mentioned waste materials on the index properties of clays obtained. This study is divided into two phases, wherein in the first phase, the pure clay specimens are analyzed against mineralogical properties (i.e., chemical composition, thermal analysis, and particle size distribution). While in the second phase, index properties of pure clay specimens and clay specimens modified with 0–50% fly ash, ferrochrome slag, and silica fume are analyzed. The results reveal that the clay specimens from Turkey (USCS classification: CL) are fit for the ceramic industry and bricks production, and incorporation of waste materials can further improve their index properties. It is also observed that incorporation of 10–30% fly ash and ferrochrome slag have higher efficiency in reducing the plasticity index of clays studied as compared to the addition of silica fume.
40
Abd El-Fattah, Ahmed, e Eman Abd ElKader. "Influence of different clays on the mechanical, thermal, and water absorption properties of recycled high-density polyethylene/wood flour hybrid composites". Journal of Composite Materials 52, n. 9 (26 luglio 2017): 1215–26. http://dx.doi.org/10.1177/0021998317723180.
Testo completoAbstract (sommario):
Wood plastic composites based on recycled high-density polyethylene (r-HDPE)/wood flour with the addition of organically modified clays were prepared by melt mixing and compression molding. The effect of two different types and contents of clays, bentonite and layered double hydroxide – on the mechanical, thermal, and water absorption properties of the wood plastic composites – was examined to identify the most effective clay type for wood plastic composites. It was found that incorporation of 2 wt% modified bentonite (mBNT) clay was the most effective in the composite formulation; it has significantly enhanced the properties of the wood plastic composites. The scanning electron micrographs of the fractured surfaces showed improved interfacial adhesion of the composite components. The tensile strength of wood plastic composites was increased by 9.7% when 2 wt% mBNT clay was incorporated in the composite formulation; however, the tensile strength slightly decreased as the clay content was further increased. The izod impact strength was lowered about 10.5% by 2 wt% mBNT clay. Moreover, the addition of 2 wt% mBNT clay enhanced the water resistance of the wood plastic composites by 27.5% after immersion in water for five days. On the other hand, the modified layered double hydroxide (mLDH) clay did not cause any remarkable improvement in the properties of the wood plastic composites. The tensile strength showed a decreasing trend with an increase in mLDH content. However, both clays did not improve the thermal stability of wood plastic composites. In addition, there are no noticeable changes in the values of melting temperature by increasing the content of clays. The experimental results indicated that the properties of the wood plastic composites were significantly improved when combined with the appropriate clay type and content. However, the interaction between wood flour and the intercalated clay particles as well as the processing conditions will need further study.
41
Kiari, Mohamed, Raúl Berenguer, Francisco Montilla e Emilia Morallón. "Preparation and Characterization of Montmorillonite/PEDOT-PSS and Diatomite/PEDOT-PSS Hybrid Materials. Study of Electrochemical Properties in Acid Medium". Journal of Composites Science 4, n. 2 (8 maggio 2020): 51. http://dx.doi.org/10.3390/jcs4020051.
Testo completoAbstract (sommario):
The hybridization of clay minerals with conducting polymers receives great interest for different potential applications, including environmental remediation. This work studies and compares the electrochemical properties of two different clays, montmorillonite (Mont) and diatomite (Diat), and their respective clay/PEDOT-PSS hybrid materials in H2SO4 medium. The hybrid materials were prepared by electropolymerization of EDOT in the presence of PSS. The physico-chemical and electrochemical properties of both clays were analyzed by different techniques, and the influence of the clay properties on electropolymerization and the electroactivity of the resulting clay/PEDOT-PSS hybrids was investigated. Specifically, the Fe2+/Fe3+ redox probe and the oxidation of diclofenac, as a model pharmaceutical emerging pollutant, were used to test the electron transfer capability and oxidative response, respectively, of the clay/PEDOT-PSS hybrids. The results demonstrate that, despite its low electrical conductivity, the Mont is an electroactive material itself with good electron-transfer capability. Conversely, the Diat shows no electroactivity. The hybridization with PEDOT generally enhances the electroactivity of the clays, but the clay properties affect the electropolymerization efficiency and hybrids electroactivity, so the Mont/PEDOT displays improved electrochemical properties. It is demonstrated that clay/PEDOT-PSS hybrids exhibit diclofenac oxidation capability and diclofenac concentration sensitivity.
42
Hurst, A. "Textural and geochemical micro-analysis in the interpretation of clay mineral characteristics: lessons from sandstone hydrocarbon reservoirs". Clay Minerals 34, n. 1 (marzo 1999): 137–49. http://dx.doi.org/10.1180/000985599545993.
Testo completoAbstract (sommario):
AbstractBack-scattered electron images of clay minerals from sandstones are used, together with complementary micro-analytical methods, to identify and quantify mineral microporosity and geochemistry. Clay minerals typically have a range of microporosity from 10 to >90% dependent on texture and paragenesis. Fibrous clays are highly microporous; detrital clays have low microporosity but specific clay minerals have broad ranges of microporosity. The often quoted mineral-chemical association between thorium (Th) and kaolinite cannot be substantiated by micro-analysis. The Th content of clay minerals is associated with micro-inclusions within the kaolinite which form diagenetically or are derived from precursor minerals.
43
Nasedkin, V. V., N. M. Boeva e A. L. Vasiliev. "Akkalkan deposit of bentonite clays (Southeast Kazakhstan): formation conditions and prospects for technological use". Геология рудных месторождений 61, n. 5 (18 novembre 2019): 84–95. http://dx.doi.org/10.31857/s0016-777061584-95.
Testo completoAbstract (sommario):
The article presents the results of the bentonite clays study of Akkolkanskoye deposit, located in South-Eastern Kazakhstan. Based on the mapping, four main types of bentonites were identified: light gray argillite-like clay; dark gray clay lamellar and crushed stone morphology; waxy light brown and pale yellow clay lamellar texture; black plastic clay. Mineralogical study of these varieties allowed to establish the relationship of crystal-morphological features of the main rock-forming mineral in clays with the conditions of their formation and with the technological properties of bentonite raw materials for use in various industries.
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Yakushev, Vladimir. "Experimental Modeling of Methane Hydrate Formation and Decomposition in Wet Heavy Clays in Arctic Regions". Geosciences 9, n. 1 (27 dicembre 2018): 13. http://dx.doi.org/10.3390/geosciences9010013.
Testo completoAbstract (sommario):
Experimental studies on clay sample saturation by methane hydrates proved that clay particles play an important role in the hydrate accumulation and decomposition processes in sediments. Depending on water content, the same clay mineral can serve as inhibitor, neutral component and promoter of hydrate formation. Wet clay is a good mineral surface for hydrate formation, but clays represent the worst media for hydrate accumulation and existence. Nevertheless, there are many observations of hydrate presence in clay-containing sediments, especially offshore. Experimental modelling of metastable hydrate decomposition in sediment samples recovered from permafrost in “Yamal crater” in the Russian Arctic has shown that metastable hydrates located in frozen, salted clays can generate huge volumes of gas, even with a negligible (tenth and hundredth of a degree) temperature rise.
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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.
Testo completoAbstract (sommario):
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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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.
Testo completoAbstract (sommario):
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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Casarella, Angela, Alessandro Tarantino e Alice Di Donna. "Micromechanical interpretation of thermo-plastic behaviour of clays". E3S Web of Conferences 205 (2020): 09003. http://dx.doi.org/10.1051/e3sconf/202020509003.
Testo completoAbstract (sommario):
The effect of temperature on mechanical behaviour of clay-based geomaterials is relevant in a number of geotechnical applications (e.g. low enthalpy geothermal systems and energy geostructures, nuclear waste disposal, and heating in rapid shear deformation). Mechanical response of (saturated) clays upon heating is not always intuitive as volume changes may occur due to both thermal expansion of clay constituents and temperature-induced changes of clay microstructure. This paper first revisits the macroscopic thermally-induced mechanical behaviour of saturated clays available in the literature via an advanced thermo-elastoplastic constitutive model and then elucidates the dependence on clay mineralogy of the two key parameters of the model (mechanical hardening and thermal softening respectively) by inspecting differences in clay inter-particle electro-chemical forces occurring in kaolinitic, illitic, and smectitic clays. The micromechanically-based interpretation of constitutive parameters can serve as a guidance for soil parameter selection in the design of energy geostructures.
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Mousavi, Seyed Sina, Chandrasekhar Bhojaraju e Claudiane Ouellet-Plamondon. "Clay as a Sustainable Binder for Concrete—A Review". Construction Materials 1, n. 3 (29 settembre 2021): 134–68. http://dx.doi.org/10.3390/constrmater1030010.
Testo completoAbstract (sommario):
The negative environmental impacts of Portland cement as a binder in the construction industry have created a growing impetus to develop sustainable alternative binders. Various types of clay have been considered as potential cement replacements. The impact of clays as cement replacement depends on the dosage and treatment methods. This paper presents a comprehensive review to determine the effects of different types of clay on the fresh and hardened properties of concrete mixtures by analyzing the experimental database reported by the literature, including raw, calcined, modified, nano, and organo. This study intends to show the process of optimizing the use of clay in concrete, the reason behind converting raw clay to modified types, and research gaps through a comparison study between different types of clays. The present review study shows that clay-based concrete mixtures have higher thixotropy and yield stress values, improving shape stability. This results in lower early-age shrinkage of the concrete. However, the high floc strength of clay-based concrete causes a reduction in flowability. Treatment methods of raw clay, such as calcination and nano-sized clay particles, improve concrete compressive strength. General results of the previous studies highlight that all types of clay investigated positively affect the resistance of concrete to environmental attack.
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Ushnickaya, H., e A. Mestnikov. "INVESTIGATION OF THE PROPERTIES OINVESTIGATION OF THE PROPERTIES OF CLAY RAW MATERIALS BY METHODS OF PHYSICO-CHEMICAL ANALYSIS". Bulletin of Belgorod State Technological University named after. V. G. Shukhov 9, n. 4 (20 febbraio 2024): 16–25. http://dx.doi.org/10.34031/2071-7318-2024-9-4-16-25.
Testo completoAbstract (sommario):
The article presents the results of the study of the properties of clay raw materials using modern methods of physico-chemical analysis: X-ray fluorescence analysis (XRF), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and thermal analysis. Two types of clay raw materials based on the color of the ceramic shard were considered: light-burning and red-burning clays. The studied clay raw materials contain a small amount of clay minerals and a high content of dusty particles, belong to moderately plastic and medium plastic clays and loams. X-ray spectral analysis allowed to determine the chemical quantitative composition of the main oxides of clay raw materials. Thermal analysis of natural clay raw materials, which have a polymineral composition, reveals exothermic and endothermic effects characteristic of the studied minerals – montmorillonite and kaolinite. According to the mineral composition, the clay raw materials of Central Yakutia are polymineral, with the main clay minerals being montmorillonite and kaolinite, and quartz, calcite, chlorite, minerals from the mica and feldspar groups, and mixed-layer minerals found as impurities. The low quality of the clay raw material suggests that further research should be conducted to improve the technological and physical-mechanical properties of ceramic products made from local clay raw material. In the design of raw material mixtures, local natural and man-made mineral raw materials can be used.
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Yang, Er-jing, Sha-sha Zeng, Hong-yan Mo, Cheng-lin Yang, Cheng Chen e Yan-fu Wang. "Analysis of the Mineral Compositions of Lateritic Clay in Guangxi and their Influence". Advances in Materials Science and Engineering 2022 (11 maggio 2022): 1–9. http://dx.doi.org/10.1155/2022/4068773.
Testo completoAbstract (sommario):
In order to study the effect of mineral composition on the physical properties of lateritic clays, the mineral compositions of four kinds of lateritic clay from Guangxi province in China were quantitatively analyzed by means of DTA, XRD, SEM, XRF and total chemical element analysis. On this basis, the variation law of macroscopic physical properties of lateritic clay was analyzed from the perspective of mineralogy. The results show that kaolinite and goethite are the main minerals of lateritic clays from Guangxi in China. The mineral compositions of these four samples are quantitatively and accurately analyzed by Bogue’s method. According to the study on mineral compositions of soil samples, the physical properties of lateritic clay are related to its clay minerals and cemented substances. The liquid limit (LL) or plastic limit (PL) increases with the increase of the ability and content of clay minerals to adsorb water. The lateritic clay is dominated by kaolinite minerals with low adsorption capacity, so the observed boundary water content (LL and PL) of high value of lateritic clays can be explained by the contribution of “inert water” in soil pores. The iron-bonded cement minerals (the form of existence is goethite) in lateritic clay have great influence on the liquid and plastic limits, which decrease linearly with the increase of goethite, whereas the goethite has relatively smaller effect on shrinkage characteristics. It is believed that the shrinkage characteristics of lateritic clay may also be affected by other factors.