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EARTH SCIENCES (469 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted alphabetically
Acta Geochimica     Hybrid Journal   (Followers: 3)
Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Open Access   (Followers: 6)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 17)
Advances In Physics     Hybrid Journal   (Followers: 13)
Aeolian Research     Hybrid Journal   (Followers: 5)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 3)
AMBIO     Hybrid Journal   (Followers: 13)
Anadolu University Journal of Science and Technology     Open Access  
Anales del Instituto de la Patagonia     Open Access   (Followers: 1)
Andean geology     Open Access   (Followers: 3)
Annales Henri Poincaré     Hybrid Journal   (Followers: 3)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access  
Annals of Geophysics     Full-text available via subscription   (Followers: 12)
Annals of GIS     Hybrid Journal   (Followers: 19)
Annals of Glaciology     Full-text available via subscription   (Followers: 2)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene     Hybrid Journal   (Followers: 3)
Anthropocene Review     Hybrid Journal   (Followers: 4)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Geochemistry     Hybrid Journal   (Followers: 11)
Applied Geomatics     Hybrid Journal   (Followers: 3)
Applied Geophysics     Hybrid Journal   (Followers: 7)
Applied Ocean Research     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 2)
Applied Remote Sensing Journal     Open Access   (Followers: 33)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 34)
Arctic Science     Open Access   (Followers: 6)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 10)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 16)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 10)
Asian Journal of Earth Sciences     Open Access   (Followers: 21)
Asian Review of Environmental and Earth Sciences     Open Access   (Followers: 1)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 2)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 13)
Atmospheric and Climate Sciences     Open Access   (Followers: 26)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 10)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 20)
Bulletin of Volcanology     Hybrid Journal   (Followers: 17)
Cadernos de Geociências     Open Access  
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 15)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 14)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 4)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 24)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 8)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Contemporary Trends in Geoscience     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 9)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 3)
Coral Reefs     Hybrid Journal   (Followers: 16)
Cretaceous Research     Hybrid Journal   (Followers: 6)
Cybergeo : European Journal of Geography     Open Access   (Followers: 4)
Depositional Record     Open Access  
Developments in Geotectonics     Full-text available via subscription   (Followers: 3)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 3)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 10)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 68)
Earth and Space Science     Open Access   (Followers: 9)
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 4)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 19)
Earth System Dynamics     Open Access   (Followers: 6)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 93)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 6)
Earthquake Science     Hybrid Journal   (Followers: 9)
Earthquake Spectra     Full-text available via subscription   (Followers: 17)
Ecohydrology     Hybrid Journal   (Followers: 9)
Ecological Questions     Open Access   (Followers: 7)
Electromagnetics     Hybrid Journal   (Followers: 4)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 23)
Environmental Geology     Hybrid Journal   (Followers: 9)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Hybrid Journal   (Followers: 3)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (Followers: 17)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 34)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (Followers: 11)
Exploration Geophysics     Hybrid Journal   (Followers: 4)
Facies     Hybrid Journal   (Followers: 9)
Fieldiana Life and Earth Sciences     Full-text available via subscription   (Followers: 1)
Física de la Tierra     Open Access  
Folia Musei rerum naturalium Bohemiae occidentalis. Geologica et Paleobiologica     Open Access  
Folia Quaternaria     Open Access  
Forestry Chronicle     Full-text available via subscription   (Followers: 10)
Frontiers in Earth Science     Open Access   (Followers: 5)
Frontiers in Geotechnical Engineering     Open Access   (Followers: 2)
Frontiers of Earth Science     Hybrid Journal   (Followers: 8)
Fundamental and Applied Limnology / Archiv für Hydrobiologie     Full-text available via subscription   (Followers: 4)
GEM - International Journal on Geomathematics     Hybrid Journal   (Followers: 1)
Geo-Marine Letters     Hybrid Journal   (Followers: 7)
Geoacta     Open Access   (Followers: 4)
Geobiology     Hybrid Journal   (Followers: 7)
Geocarto International     Hybrid Journal   (Followers: 18)
Geochemical Perspectives     Hybrid Journal  
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 7)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 24)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 25)
Geochronometria     Hybrid Journal   (Followers: 3)
Geoderma Regional : The International Journal for Regional Soil Research     Full-text available via subscription   (Followers: 3)
Geodinamica Acta     Hybrid Journal   (Followers: 3)
Geodynamics & Tectonophysics     Open Access   (Followers: 1)
Geoenvironmental Disasters     Open Access   (Followers: 3)
Geofluids     Hybrid Journal   (Followers: 4)
Geoforum     Hybrid Journal   (Followers: 20)
Géographie physique et Quaternaire     Full-text available via subscription   (Followers: 1)
Geography and Natural Resources     Hybrid Journal   (Followers: 5)
Geoheritage     Hybrid Journal   (Followers: 1)
Geoinformatica Polonica : The Journal of Polish Academy of Arts and Sciences     Open Access  
Geoinformatics & Geostatistics     Hybrid Journal   (Followers: 8)
Geological Journal     Hybrid Journal   (Followers: 14)
Geology Today     Hybrid Journal   (Followers: 18)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 3)
Geomatics, Natural Hazards and Risk     Hybrid Journal   (Followers: 9)
Geomechanics for Energy and the Environment     Full-text available via subscription  
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 25)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 30)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Geophysics     Full-text available via subscription   (Followers: 18)
GeoResJ     Hybrid Journal  
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards     Hybrid Journal   (Followers: 8)
Geoscience Canada : Journal of the Geological Association of Canada / Geoscience Canada : journal de l'Association Géologique du Canada     Full-text available via subscription   (Followers: 3)
Geoscience Data Journal     Open Access   (Followers: 2)
Geoscience Frontiers     Open Access   (Followers: 9)
Geoscience Letters     Open Access  
Geoscience Records     Open Access  
Geosciences     Open Access   (Followers: 2)
Geosciences Journal     Hybrid Journal   (Followers: 9)
Geoscientific Instrumentation, Methods and Data Systems     Open Access   (Followers: 4)
Geoscientific Model Development     Open Access   (Followers: 2)
Geostandards and Geoanalytical Research     Hybrid Journal   (Followers: 2)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotectonic Research     Full-text available via subscription   (Followers: 4)
Geotectonics     Hybrid Journal   (Followers: 7)
GISAP : Earth and Space Sciences     Open Access   (Followers: 3)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 3)
Global and Planetary Change     Hybrid Journal   (Followers: 12)
Global Biogeochemical Cycles     Full-text available via subscription   (Followers: 11)
Gondwana Research     Hybrid Journal   (Followers: 6)
Grassland Science     Hybrid Journal   (Followers: 1)
Ground Water     Hybrid Journal   (Followers: 26)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 17)
Groundwater for Sustainable Development     Full-text available via subscription  
GSA Today     Partially Free  
Helgoland Marine Research     Open Access   (Followers: 3)
History of Geo- and Space Sciences     Open Access   (Followers: 5)
Hydrobiologia     Hybrid Journal   (Followers: 18)
Hydrogeology Journal     Hybrid Journal   (Followers: 16)
Hydrological Processes     Hybrid Journal   (Followers: 23)
Hydrology and Earth System Sciences     Open Access   (Followers: 26)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 53)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 11)
Indian Geotechnical Journal     Hybrid Journal   (Followers: 2)
Indonesian Journal on Geoscience     Open Access   (Followers: 2)
Interdisciplinary Environmental Review     Hybrid Journal   (Followers: 3)
International Geology Review     Hybrid Journal   (Followers: 5)
International Journal of Advanced Geosciences     Open Access  
International Journal of Advanced Remote Sensing and GIS     Open Access   (Followers: 33)
International Journal of Advancement in Earth and Enviromental Sciences     Open Access   (Followers: 3)
International Journal of Advancement in Remote Sensing, GIS, and Geography     Open Access   (Followers: 27)
International Journal of Applied Earth Observation and Geoinformation     Hybrid Journal   (Followers: 34)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 10)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 30)
International Journal of Forest, Soil and Erosion     Open Access   (Followers: 4)

        1 2 3 | Last

Journal Cover Applied Clay Science
  [SJR: 0.826]   [H-I: 83]   [4 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [3038 journals]
  • Thermoexfoliated commercial vermiculites for Ni2+ removal
    • Authors: Celia Marcos; Irene Rodríguez
      Pages: 685 - 693
      Abstract: Publication date: Available online 6 September 2016
      Source:Applied Clay Science
      Author(s): Celia Marcos, Irene Rodríguez
      The aim of the present study was to investigate the effect of thermal expansion on the removal efficiency of commercial vermiculites towards Ni2+ ion from aqueous solutions. Three effects were studied: 1) Contact time between the adsorbent and Ni2+ dissolved in the retention process; 2) adsorbent mass; 3) concentration of Ni2+ in adsorption. Ni2+ uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR) models. In addition, the adsorption equilibrium was described well by the DKR isotherm model, indicative of a cooperative process. The maximum adsorption capacity obtained with DKR model of 3.13mol/g of Ni2+ on China vermiculite was higher than the value of 2.91 obtained for Piauí vermiculite. The kinetic experimental data were described using pseudo-first and pseudo-second order kinetic models, being well described by pseudo-second order model. The adsorption rate value in distilled water was the same with both vermiculites, 0.001h−1. Thermally exfoliated vermiculites type-2, as China, would be more suitable than vermiculites type-1, as Piauí, for recovering traces of Ni2+ in water because: a) its high mica-like content and therefore high degree of expansion, exfoliation and formation of larger pores; b) its maximum adsorption capacity.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.08.024
      Issue No: Vol. 132-133 (2016)
  • In Memory of HAYDN H. MURRAY
    • Authors: Emilio Galán; Colin Harvey; Faiza Bergaya
      Pages: 1 - 2
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Emilio Galán, Colin Harvey, Faiza Bergaya

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.07.024
      Issue No: Vol. 131 (2016)
  • Kaolin deposits and their uses: Northern Brazil and Georgia, USA
    • Authors: Robert J. Pruett
      Pages: 3 - 13
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Robert J. Pruett
      Kaolin mineral-bearing rocks are classified by their mineralogy and texture, which delineate their potential use. Refractory clay products are made from a continuum of ores comprising fire clay, bauxitic kaolin and bauxite. Ceramic clay products are made from a range of ores comprising near pure kaolin, ball clays, plastic clays, kaolinitic sandstone and china clays along with some other clay minerals that impart plasticity and having some other non-clay minerals such as quartz and feldspar that allow a white-burnt appearance at a specified melting temperature. Pigments and additives are beneficiated from kaolinitic rocks that have textures which permit particle dispersion for size classification and for removal of impurities. The diverse mineralogy and texture found in Georgia, USA sedimentary kaolin deposits explain their range of beneficiation processes and uses. Capim [Brazil] soft kaolins are mostly used for pigment applications because of their mineralogical purity, ease of dispersion and geological homogeneity, which permits large-scale production of products having consistent quality.
      Graphical abstract image

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.01.048
      Issue No: Vol. 131 (2016)
  • New insights on mineralogy and genesis of kaolin deposits: The Burela
           kaolin deposit (Northwestern Spain)
    • Authors: Emilio Galán; Patricia Aparicio; Juan Carlos Fernández-Caliani; Adolfo Miras; Marcial G. Márquez; Anthony E. Fallick; Norbert Clauer
      Pages: 14 - 26
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Emilio Galán, Patricia Aparicio, Juan Carlos Fernández-Caliani, Adolfo Miras, Marcial G. Márquez, Anthony E. Fallick, Norbert Clauer
      The Burela deposit is the largest kaolin deposit in Spain, mined for more than 50years, the product being mainly used for porcelain. Kaolin is dominantly associated with Lower Cambrian felsites, interbedded with quartzites, micaschists and metapelites (Cándana Series), and was strongly folded during the Variscan orogeny. Kaolin layers were ductile and incompetent materials among more competent ones, producing many slides with a diastrophic appearance. Consequently, kaolin outcrops are morphologically very variable– i.e. pockets – and interlayered between metapelites and/or quartzites, resulting in complication for prospection and mining. The kaolin consists mainly of kaolinite, tubular halloysite, and spherical allophane along with quartz and minor illite. The content of kaolin minerals reaches up to 90% in the finer fractions (<2μm and <1μm). Geochemical analyses of trace and REE show a close relationship between kaolin and associated rocks. Two kaolin types can be differentiated: (i) massive, associated to felsite; and (ii) related to metapelite. A temperature range from 15 to 35°C, with an average of approximately 28°C was calculated on the basis of the isotopic signatures (δ18O, δD) for the kaolin materials. This scatter suggests that if continental weathering was involved in the kaolin formation on the lower side of the temperatures, it was not the only process, especially for kaolin associate with felsites and metapelites. The higher temperatures are indicative of a hydrothermal auto-metamorphic alteration, followed by a folding of the series that induced an apparently chaotic kaolin distribution with a combined continental weathering superimposed on the previous low-temperature hydrothermal felsite transformation.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.11.015
      Issue No: Vol. 131 (2016)
  • Approach to the trace element geochemistry of non-marine sepiolite
           deposits: Influence of the sedimentary environment (Madrid Basin, Spain)
    • Authors: Manuel Pozo; María Isabel Carretero; Emilio Galán
      Pages: 27 - 43
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Manuel Pozo, María Isabel Carretero, Emilio Galán
      The trace element geochemistry of sepiolite-rich beds from five lithological sections in the Neogene Madrid Basin was analysed. The samples were collected from representative deposits including alluvial fan (Vicálvaro, Cabañas de la Sagra), palustrine (Cerro de los Batallones) and mudflat (Esquivias, Magán) facies. The mineralogical composition of the samples point out the abundant content of sepiolite, commonly higher than 95%, with variable content of quartz, feldspars, calcite, palygorskite and/or Mg-smectite. The sepiolite occurs as laminated, massive and brecciated facies, often with intraclasts of similar sepiolite composition. The geochemical results indicate that all the trace elements analysed are mostly depleted with respect to the UCC standard (Upper Crust Composition), especially REE (<0.4). The higher depletion was observed in sepiolites from mudflat facies (V and U content are an exception). Cluster analysis of geochemical data corroborates the differences between mudflat sepiolites and those from palustrine and alluvial-related facies. The normalization of REE with chondrite allows clear differentiation between the sepiolites associated with alluvial fan facies from all the remaining samples. On the other hand, the La/Sc ratio against Th/Co ratio indicates provenance from felsic rocks. High content in F (>4000μg/g) and low content of Li (20–180μg/g) is remarkable, allowing to separate samples of sepiolite formed in alluvial fan environments from those of mudflat and palustrine deposits. The geochemical complexity observed in the sepiolites was closely related to the specific mechanisms of formation under different environmental conditions.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.10.024
      Issue No: Vol. 131 (2016)
  • Genesis and mining potential of kaolin deposits in Patagonia (Argentina)
    • Authors: Eduardo Domínguez; Michele Dondi; Ricardo Etcheverry; Clemente Recio; Claudio Iglesias
      Pages: 44 - 47
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Eduardo Domínguez, Michele Dondi, Ricardo Etcheverry, Clemente Recio, Claudio Iglesias
      Kaolin occurs in Patagonia as residual (weathering or hydrothermal) deposits at the surface of an extended Jurassic rhyolite province or in the upper sedimentary Cretaceous or Danian–Paleocene layers. On the same paleogeographic surface, numerous epithermal Au–Ag lodes occur, making kaolin genesis a crucial point in mining exploration. The weathering or sedimentary genesis of some deposits (Puma, Súper, FPS, Espingarda and Marta) was confirmed through clay isotope results. The origin of some corrective clays (Bajo Grande and White Bentonite) was analyzed and compared with that of one sample from Ukraine and one from a hydrothermal deposit in Furtei, Sardinia, Italy. In Patagonia, the residual and sedimentary kaolin deposits have resources of over 12 million tons. The identified hydrothermal deposits have more limited resources, due to their strong mineralogical zonation, which requires their selective “pocket” kaolin exploitation. The Patagonian region is the southernmost part of a continent where a Gondwana paleosurface of Late Mesozoic age developed on Jurassic rhyolite volcanic units. This surface is exposed along tens of thousands square kilometers in the cratonic units of northern and southern Patagonia, having a strong potential for finding new kaolin or epithermal precious metal deposits.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.12.031
      Issue No: Vol. 131 (2016)
  • Spheroidal halloysites from Patagonia, Argentina: Some aspects of their
           formation and applications
    • Authors: F. Cravero; L. Fernández; S. Marfil; M. Sánchez; P. Maiza; A. Martínez
      Pages: 48 - 58
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): F. Cravero, L. Fernández, S. Marfil, M. Sánchez, P. Maiza, A. Martínez
      Halloysite deposits in Argentina have been identified in the province of Río Negro (Patagonia). The mineralized area occurs as altered zones in Eocene volcanic–pyroclastic rocks, dacitic to rhyolitic in composition. A comprehensive study of these deposits was carried out by means of mineralogical, geochemical and isotopic analyses. Intense weathering has transformed the whole rock to a white mass composed of 75% –90% halloysite+kaolinite, with cristobalite, tridymite, and quartz, as the main non-clay minerals. Ferruginous beidellite and titanium minerals are also present in minor amounts. The halloysite–kaolinite ratio ranges from 75 to 25 to 100–0. Due to the alteration of very dense rocks, halloysite morphology is predominantly spheroidal. Tubular halloysite is the main constituent in more porous rocks, but the latter are scarce in the area. Because of the predominance of the spheroidal type, the use of halloysite as HNT (halloysite nanotube) is not feasible. Nonetheless, this mineral can be modified by different organic molecules, and used to remove pollutants such as emulsified hydrocarbons and heavy metals. A special product made with this halloysite is used as sunscreen when sprayed on fruits in areas of intense solar radiation. The whiteness of this mineral is not very high due to the amount of titanium oxide present in its composition (about 1%). Nevertheless, titanium oxide is present as individual particles, so it could be removed by a mechanical process. New applications for spheroidal halloysite are currently being investigated. Moreover, depending on the price and demand, the tubular halloysite of low grade deposits could be exploited.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.01.011
      Issue No: Vol. 131 (2016)
  • Evidence of montmorillonite/Fe-rich smectite transformation in the Morrón
           de Mateo bentonite deposit (Spain): Implications for the clayey barrier
    • Authors: M. Pelayo; E. García-Romero; M.A. Labajo; L. Pérez del Villar
      Pages: 59 - 70
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): M. Pelayo, E. García-Romero, M.A. Labajo, L. Pérez del Villar
      The Morrón de Mateo bentonite deposit (Cabo de Gata region, Spain) has been studied as a natural analogue of the thermal and geochemical effects on the clayey barrier in a deep geological repository of high level radioactive wastes. This deposit was intruded by a volcanic dome inducing an increase of temperature and supplying Fe–Mg-rich solutions, which were responsible for the alteration of the previously bentonitised pyroclastic materials (white tuff formation). The textural, mineralogical and crystallochemical features of the smectites located within the vicinity and away from the dome have been studied in order to elucidate the intrusion effects on these smectites. The results obtained show that distal smectites are Al-montmorillonites, similar to those from other bentonite deposits in the Cabo de Gata region; whereas proximal smectites are a mixture of Al-montmorillonites, Fe-rich montmorillonites and beidellites, and intermediate smectites between beidellite and Fe-rich-saponite. The textural relationships between these smectites indicate that smectites with intermediate composition come from the transformation of Al-montmorillonite, through gradual steps, consisting of increasingly Mg and Fe-rich smectites. This transformation process is confirmed when the structural formulae of proximal smectites are plotted on the MgVI vs (Al+Fe3+)VI diagram. Thus, a gradual transition from dioctahedral smectites to smectites with an intermediate chemical composition is observed, which tend toward trioctahedral smectites. These observations suggest that the transformation of dioctahedral smectites into an intermediate term between di- and trioctahedral Fe-rich smectites could be originated under natural conditions. This transformation can be considered as an analogue process to that expected in the bentonite barrier from a deep geological repository of radioactive wastes whether the two following conditions would occur: i) an increase of temperature due to the radioactive decay of the fission products, and ii) a supply of Fe as result of the canister corrosion under intermediate redox conditions. Furthermore, similar results were obtained in laboratory experiments focused on the Fe/Al-smectite interaction processes, related to the durability of the clayey engineered barrier.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.12.033
      Issue No: Vol. 131 (2016)
  • Hydrochemical factors influencing the crystallinity and composition of
           kaolins and other silicates, revisited
    • Authors: Colin C. Harvey; Enrique Merino
      Pages: 71 - 73
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Colin C. Harvey, Enrique Merino
      Increasing pH of aluminum-bearing aqueous solutions causes most of the aluminum to pass from octahedral to tetrahedral coordination over a narrow pH interval: 5.5 to 6.5 at 25°C and 4 to 5 at 100°C. Thus silicates that grow from Al-bearing solutions having pH>6.5 at 25°C (or >5 at 100°C) should incorporate significant Al(tet) substituting for Si (especially if the solution provides monovalent cations to compensate for the charge defect), but should not do so if pH<5.5. This applies to a number of phyllosilicates, quartz, opal-CT, and opal-A in scales formed in tubes of geothermal power plants. In turn the predicted Al(tet)-for-Si substitution can explain the aggregate deformation of certain crystal structures induced by the larger size of the AlO4 tetrahedra, including the curling of the 1:1 layers of halloysite and the observed twisting of the tiny fibers of chalcedonic quartz making up agate layers.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.01.028
      Issue No: Vol. 131 (2016)
  • Physical properties and Na-activation of Egyptian bentonitic clays for
           appraisal of industrial applications
    • Authors: Mohamed A. Agha; Ray E. Ferrell; George F. Hart; Mohamed S. Abu El Ghar; Ali Abdel-Motelib
      Pages: 74 - 83
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Mohamed A. Agha, Ray E. Ferrell, George F. Hart, Mohamed S. Abu El Ghar, Ali Abdel-Motelib
      Selected physical properties of bentonitic clays in the north Western Desert, Egypt were investigated to assess their potential use in industrial applications. Assessment tests included specific surface area (SSA), swelling index (SI), green (GCS) and dry (DCS) compressive strengths, rheological properties, and filtrate volume. The impact of Na-activation on swelling index and rheological properties was also considered. SSA, SI after Na-activation, GCS, and rheological properties were highly correlated with smectite content and a modified AgTU-CEC. Mineral impurities greatly influenced the physical properties. Quartz and feldspars reduced the rheological properties and increased the water loss. Halite and colloidal iron oxides increased swelling index and enhanced rheological properties. DCS was greatly influenced by the percentage of added water and kaolinite abundance. Na-activation improved the swelling index and rheological properties of halite-poor samples. The swelling index of Na-activated samples was a useful tool for determining the quality and grade of bentonitic clays. The suitability of the Egyptian bentonitic clays for drilling mud and bonding of foundry sands was determined by comparing the results with a standard bentonite and published industrial specifications. Egyptian bentonitic clays showed comparable compressive strengths with Wyoming Na-bentonite (SWy-1) by adding 8 and 10wt.% clay to sand molds and can be used for most metal-type castings. Egyptian bentonitic clays with a high swelling index and low quartz and feldspar content, produced comparable rheological properties with the Wyoming Na-bentonite and met international drilling mud specifications. However, the filtrate volume measurements indicated that the samples require additional modifications to reduce water loss. Many desirable bentonitic clay properties were reduced by large quantities of kaolinite.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.08.016
      Issue No: Vol. 131 (2016)
  • Acid activated clays: Materials in continuous demand
    • Authors: Peter Komadel
      Pages: 84 - 99
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Peter Komadel
      Acid activation is a chemical treatment traditionally used on clays, typically bentonites in hydrochloric or sulphuric acid, to obtain partly dissolved materials with enhanced surface properties suitable for new applications or displaying interesting new behaviour. This paper is based mostly on the results of long-running experiments in our laboratories, supplemented by published data from elsewhere. A review of recent literature shows that interest in these materials remains widespread, with several new developments of environmental relevance and in the area of clay-polymer nanocomposites. Acid treatment of vermiculites and of non-swelling clay materials is also included.
      Graphical abstract image

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.05.001
      Issue No: Vol. 131 (2016)
  • How the unique properties of soil kaolin affect the fertility of tropical
    • Authors: Robert J. Gilkes; Nattaporn Prakongkep
      Pages: 100 - 106
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Robert J. Gilkes, Nattaporn Prakongkep
      The kaolin (s.l.) in many tropical soils is distinctly different from most specimen and industrial kaolins. Crystal structure is highly disordered and crystal sizes are much smaller than for specimen and industrial kaolins. The crystal habit of soil kaolins is diverse ranging through euhedral hexagonal and anhedral platy, spheroidal and tubular. The specific surface of soil kaolins is higher than for most industrial kaolins. Consequently, cation and anion retention capacities are higher although there is no compelling evidence that the high structural disorder of soil kaolin is associated with a greater specific reactivity of the kaolin surface. A small amount of ferric iron substitutes for octahedral Al but there is generally little or no substitution of other cations. Soil kaolin commonly contains minor amounts of potassium but this is present in mica layers within, attached or associated with kaolin crystals so that potassium is not within the kaolin structure. Due to its considerable chemical reactivity soil kaolin helps provide an effective substrate to support agriculture and other land uses in the tropics.
      Graphical abstract image

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.01.007
      Issue No: Vol. 131 (2016)
  • Reflections on the material science of clay minerals
    • Authors: Robert A. Schoonheydt
      Pages: 107 - 112
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Robert A. Schoonheydt
      Possible new applications of clay minerals are explored continuously. Three such areas are clay-polymer nanocomposites, clay mineral films and clay mineral catalysts. Advances in these areas must come from the increase of fundamental knowledge of the clay minerals, especially the expanding clay minerals or smectites. Examples of fundamental research areas are: the mechanical properties of single clay layers and the change of these mechanical properties with the number of layers in a clay mineral particle; control of the organization of clay mineral layers and of molecules in the interlayer space for the production of functional films; and the distribution of pillars and of metal nanoparticles in the interlayer space for application as catalysts. Natural clay minerals suffer from several disadvantages, such as the presence of impurities and inhomogeneities in sizes and shapes of particles and in charge distribution. Synthesis of clay minerals with well-defined sizes and shapes of the particles and with homogeneous charge distribution is imperative to obtain significant advancement of knowledge.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.12.005
      Issue No: Vol. 131 (2016)
  • A proposal for the formulation of high-quality ceramic “green”
           materials with traditional raw materials mixed with Al-clays
    • Authors: I. González; P. Campos; C. Barba-Brioso; A. Romero; E. Galán; E. Mayoral
      Pages: 113 - 123
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): I. González, P. Campos, C. Barba-Brioso, A. Romero, E. Galán, E. Mayoral
      Spain is one of the main ceramics producers of Europe and, in spite of the world economic crisis, the exporting market and the production of advanced ceramics are strengthening again many Spanish ceramic areas. In this sense, the efforts now should be directed to the consecution of new ceramic formulations that optimize the technological properties of the products and contribute to significant changes in the fabrication technology. Some advances should be directed to improve the drying process, to reduce the firing temperature, to eliminate efflorescence, etc., and even to reduce contamination effects of ceramic production, if possible. Accordingly, this paper presents the study of traditional raw materials, marls from the Guadalquivir Basin (south Spain) and aluminium-rich raw materials from the Badajoz province (south-western Spain) for the fabrication of structural ceramics. The investigation led to the preparation of new formulations with higher quality finished products and greater added value. The new mixtures were mineralogical (X-ray diffraction) and chemically (X-ray fluorescence) characterized and their technological properties were also determined. The obtained mixtures could be used with the existing technologies to create majolica or weakly coloured porous materials in the temperature range of 850–900°C, but they are also advisable to be used in the fabrication of monoporosa or white/red birapida products firing at 1050°C. In addition, as the formulations proposed contain only moderate proportions of carbonates, the CO2 emissions during firing are reduced, and the new ceramic materials would meet the requirements of “green materials” for construction.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.12.035
      Issue No: Vol. 131 (2016)
  • ZnO/clay nanoarchitectures: Synthesis, characterization and evaluation as
    • Authors: M. Akkari; P. Aranda; H. Ben Rhaiem; A. Ben Haj Amara; E. Ruiz-Hitzky
      Pages: 131 - 139
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): M. Akkari, P. Aranda, H. Ben Rhaiem, A. Ben Haj Amara, E. Ruiz-Hitzky
      In this work, ZnO-clay heterostructured materials have been prepared as novel nanoarchitectures by generation of ZnO nanoparticles (NP) on the surface of the clay mineral. The synthetic approach implies previous modification of the clay minerals by cation exchange with cetyltrimethylammonium bromide (CTAB) solutions. So, these organophilic solids can be easily dispersed in 2-propanol being further incorporated ZnO nanoparticles (NP), which in turn are formed from reaction of zinc acetate with KOH solution. Once this sol–gel reaction is achieved, the intermediate ZnO/clay organo-heterostructures can be submitted to a thermal treatment for the removal of the organic matter, which finally gives rise to the ZnO/clay nanoarchitectures. The resulting materials were characterized by XRD, FE-SEM, TEM, UV–vis, FTIR, TG and DTA, specific surface area and porosity determinations. These techniques clearly shown the structural and textural arrangements produced during the formation of the ZnO/clay nanoarchitectures. This novel type of materials act as efficient heterogeneous photocatalysts showing higher yield in the photocatalytic decomposition of methylene blue (MB) dye in water than the corresponding ZnO powder without clay prepared under similar experimental conditions.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.12.013
      Issue No: Vol. 131 (2016)
  • Mixture of palygorskite and montmorillonite (Paly-Mont) and its adsorptive
           application for mycotoxins
    • Authors: Huitang Zhou
      Pages: 140 - 143
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Huitang Zhou
      Fuller's earth is a general term to refer to clays or earthy material that are suitable for bleaching and sorptive uses and it could include attapulgite, sepiolite, and smectite clays that have natural bleaching and/or sorptive capabilities. Paly-Mont refers specifically to a natural mixture of montmorillonite and palygorskite minerals that has sorptive property. Compared to other industrial minerals, palygorskite clay is very rare in nature. However, Paly-Mont is even rarer. The comparison of the basic structure of montmorillonite, palygorskite and their mixture Paly-Mont is that montmorillonite has platy structure and palygorskite has needle shaped structure. Paly-Mont is in between. Paly-Mont can be processed to bleaching clay using low dosage acid. It is also an excellent source clay for mycotoxin binder. After dispersion, Paly-Mont shows clearly base montmorillonite structure and the palygorskite needles above the base structure. It is this unique structure that may help for this special mixture to have high absorption to mycotoxins and at same time to have much lower nutrients to be adsorbed compared to montmorillonite.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.03.012
      Issue No: Vol. 131 (2016)
  • Clay supply for Aguada ordinary vessels from Piedras Blancas (4th to 12th
           centuries AC), Ambato Valley (Argentina)
    • Authors: Silvana R. Bertolino; Marcos R. Gastaldi; Udo Zimmermann; Andrés Laguens
      Pages: 158 - 174
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Silvana R. Bertolino, Marcos R. Gastaldi, Udo Zimmermann, Andrés Laguens
      The provenance of the raw materials used to produce ordinary ceramic vessel of the Aguada Culture (4th to 12th c. AC) from the Ambato Valley (Catamarca, Argentina) has been evaluated. Since there are no commercial clay deposits in the area, local clayish sources were selected as possible candidates. Samples were collected from Precambrian to Low Paleozoic metapelites, clays from fault gouges derived from crystalline basement rocks, epiclastic rocks and Quaternary loessic sediments that filled the valley and crop out close to the archaeological sites. The pottery sherds were found at Piedras Blancas highly hierarchical site. Mineralogical and geochemical studies were conducted by XRD and FE-SEM-EDS on both the pot sherds and the possible source materials. The latter were also preliminary evaluated on basic physical and technological properties; test specimens were heated at different temperatures (800, 900 and 1000°C) to study their thermal behavior and their mineralogical and textural transformations. The physical properties of the metapelites, the clay gouges and the loessic sediments suggest that they are suitable for ceramic production. The epiclastic rocks are mostly bentonitic and could have been used as additives to improve the plasticity and other properties of other clay materials. The mineralogy of the sherds is quite homogeneous with no significant differences between technological classes E and D; most of them bear either phlogopite, hornblende and/or hypersthene and high temperature phases (diopside, spinel, mullite and cristobalite) also found in some clays under natural conditions or after firing at 1000°C. Commonly used provenance geochemical ratios are relatively similar in all pottery samples and in the selected source rocks and comparable with typical UCC. Hence, according to those values, all samples are related to each other and indistinguishable except for one sample (B30) highly enriched in REE. Nearly all raw materials and ceramics are either enriched in Cs, Bi, Sb or in any of these elements. The trend of using local materials for the pottery is suggested by the mineralogy and the geochemistry.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.03.019
      Issue No: Vol. 131 (2016)
  • Nanoscale cross-correlated AFM, Kelvin probe, elastic modulus and quantum
           mechanics investigation of clay mineral surfaces: The case of chlorite
    • Authors: Daniele Moro; Gianfranco Ulian; Giovanni Valdrè
      Pages: 175 - 181
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Daniele Moro, Gianfranco Ulian, Giovanni Valdrè
      The physical and chemical surface properties of clay minerals have a significant impact on mineral–environment surface interactions. The study of the local surface properties of clay particles at the nanometre and sub-nm scale is of paramount importance to improve our knowledge on a variety of important interaction processes and interfacial phenomena, such as adsorption, coagulation, aggregation, sedimentation, filtration, catalysis, and ionic transport in porous media. In this work we investigated the physico-chemical properties of the (001) surface of chlorite by cross-correlating AFM, Kelvin probe force microscopy and ab initio quantum mechanics studies. Experimental measurements at the nanometre and sub-nm scale by atomic force microscopy and Kelvin probe force microscopy were performed to investigate the nanomorphology, elastic modulus and surface electrostatic potential of chlorite samples presenting Al substitutions in the tetrahedral sheets and in the hydroxylic interlayer. Quantum mechanics simulations were carried out to investigate the effect of the Al substitutions on both the mineral bulk and surface structures, and on the surface electrostatic potential. Experimental measurements and theoretical calculations were found in very good agreement, complementing each other. The approach here presented and the findings of this study can provide a valuable insight into clay mineral surface properties and a variety of interaction phenomena of clay minerals with important environmental, industrial and biotechnological applications.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2015.11.023
      Issue No: Vol. 131 (2016)
  • Structural Characterization of lamellar compounds
    • Authors: Vicente Rives; Eric Ferrage; Douglas K. McCarty; Vanessa Prevot
      First page: 1
      Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Vicente Rives, Eric Ferrage, Douglas K. McCarty, Vanessa Prevot

      PubDate: 2016-08-06T18:26:11Z
      DOI: 10.1016/j.clay.2016.06.022
      Issue No: Vol. 130 (2016)
  • Reprint of Effect of plant growth on the occurrence and stability of
           palygorskite, sepiolite and saponite in salt-affected soils on limestone
           in South Australia
    • Authors: Melissa B. Fraser; G. Jock Churchman; David J. Chittleborough; Pichu Rengasamy
      Pages: 183 - 196
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): Melissa B. Fraser, G. Jock Churchman, David J. Chittleborough, Pichu Rengasamy
      The Mg-rich clay minerals, palygorskite, sepiolite and also Mg-smectites are generally rare in soils. When they occur they are usually concentrated in subsurface horizons and become replaced by other minerals, e.g., dioctahedral smectites in near-surface horizons. Salt-affected soils on limestone in a flat landscape in southern Australia showed patchy pasture growth, including areas in which almost no growth occurred. Chemical and mineralogical analyses of deep profiles of the soils revealed two main types and that the extent of plant growth reflected their mineralogical composition. The soil type in which plants grow well (‘Chromosol’, an Alfisol) contains dioctahedral smectite (montmorillonite and/or beidellite) but only in substantial amounts at depth. The soil type in which little or no plants grew (‘Vertosol’, a Vertisol) has substantial concentrations of a trioctahedral Mg-smectite, saponite, in its surface horizons along with dioctahedral smectite in lower horizons. Both soil types contain sepiolite and palygorskite, largely in the lower horizons of the Chromosol, but also in near-surface horizons of the Vertosol. Both types of soil also contain illite and kaolinite, which are each concentrated in the upper horizons of the soils and are considered to be detrital. The genesis of the two main types of soils can be explained by the depositional history of the basin. On the eastern side of the basin, palustrine limestone formed when the sediments became exposed, possibly from uplift. The Chromosol formed on this material. On the western side, by contrast, lacustrine sediments on lowland adjacent to a stranded beach ridge, experienced prolonged seasonal inundation by water leading to the formation of the Vertosol. This soil is strongly sodic and strongly alkaline throughout and it is concluded that the high concentration of saponite in the surface swells and thereby ensures that the soil remains wet. Together with its high pH, this soil has very poor conditions for plant growth. The persistence of the Mg-rich clay minerals, especially saponite, at the surface of the Vertosol, suggests that the relative lack of plants has preserved these minerals throughout the profile.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.02.012
      Issue No: Vol. 124-125 (2016)
  • Sorption characteristics of a landfill clay soil as a retardation barrier
           of some heavy metals
    • Authors: A.A. Zaki; M.I. Ahmad; K.M. Abd El-Rahman
      Abstract: Publication date: Available online 20 September 2016
      Source:Applied Clay Science
      Author(s): A.A. Zaki, M.I. Ahmad, K.M. Abd El-Rahman
      The sorption characteristics of landfill silty clay soil (LSC), taken from AL Hammam landfill site, as a retardation barrier of Zn2+, Cd2+ and Pb2+ ions were investigated. LSC consists mainly of kaolinite, quartz and calcite minerals, is a part of thin blanket of Miocene rocks forming a vast persistent limestone plateau of the north part of the western desert of Egypt. The results showed that the percentage equilibrium uptake of the metal ions by LSC are 94.8, 92.7, and 86.0 for Zn2+, Pb2+, and Cd2+, respectively. The coefficient of diffusion's value was found in the range (3.32–6.8)0.10−17 m2/s and increases with the increase in temperature. The distribution coefficient for Pb2+, Cd2+, and Zn2+ ranged from 404.9 to 568, 230.1 to 281.9, and 371.4 to 466.7ml/g in the temperature range 298 to 333±1K, respectively. The value of retardation factor and the sorption affinity onto LSC took the order Zn2+ >Pb2+ >Cd2+. The experimental investigation on ionic concentrations in sorption batches suggested that sorption behaviors of Zn2+, Pb2+, and Cd2+ ion metals onto LSC are mainly controlled by cation exchange. The wetting front of water movement in the LSC as an unsaturated soil reached to about 0.06, 0.19 and 0.25cm after 6, 24 and 48h of steady infiltration. The saturation hydraulic conductivity of the LSC (<2.0μm) fraction is 2.18×10−10 m/s therefore, it matches the condition of suitability of soils as mineral liners for a landfill facility. The Pêclet number values (<32) indicate dominance of dispersion over advection. The <2μm fraction of LSC may be used to attenuate Zn2+, Cd2+ and Pb2+ ions presented in AL Hammam landfill leachate from reaching the shallow groundwater.

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.016
  • Cation doped hydroxyapatite nanoparticles enhance strontium adsorption
           from aqueous system: A comparative study with and without calcination
    • Authors: Poorvisha Ramakrishnan; Seethalakshmi Nagarajan; Vijayaraghavan Thiruvenkatam; Thavamani Palanisami; Ravi Naidu; Megharaj Mallavarapu; Selvakumar Rajendran
      Abstract: Publication date: Available online 23 September 2016
      Source:Applied Clay Science
      Author(s): Poorvisha Ramakrishnan, Seethalakshmi Nagarajan, Vijayaraghavan Thiruvenkatam, Thavamani Palanisami, Ravi Naidu, Megharaj Mallavarapu, Selvakumar Rajendran
      The present study reports the synthesis of a biocompatible, eco-friendly, anisotropic cation doped hydroxyapatite nanoparticles (nHAp) for strontium removal from aqueous environment. The nHAp was modified by cation doping, characterized using suitable techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and, high resolution transmission electron microscopy (HRTEM) attached with selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDAX). nHAp based materials were investigated for its strontium adsorption property with and without calcination. Successful doping of the cations into the nHAp matrix was confirmed by X-ray photoelectron spectroscopy (XPS). The morphology and the particle size of the nHAp varied significantly with cation doping (Na, Mg and Al) and calcination. Calcination of nHAp decreased the dissolution rate when compared to uncalcined nHAp. The biocompatibility and toxicity studies of modified nHAp with human osteoblast (MG63) cell line indicated that the cation doping onto nHAp had considerable impact on its toxicity. In the initial screening studies, Al-nHAp and Mg-nHAp showed higher strontium adsorption percentage of 83.90±3.03 and 70.98±2.74 respectively. The adsorption capacity of the materials was much superior to many of the HAp based materials reported earlier. These studies clearly indicate that the cation doped, degradable (for efficient disposal of adsorbate saturated HAp beyond reuse), eco-friendly nHAp is suitable for removal of strontium from contaminated water.

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.022
  • Investigation of halloysite nanotube content on electrophoretic deposition
           (EPD) of chitosan-bioglass-hydroxyapatite-halloysite nanotube
           nanocomposites films in surface engineering
    • Authors: A. Molaei; M. Yari; M.Reza Afshar
      Abstract: Publication date: Available online 23 September 2016
      Source:Applied Clay Science
      Author(s): A. Molaei, M. Yari, M.Reza Afshar
      This study investigated the effect of halloysite (Hal) concentration on electrophoretically deposited chitosan (CS)-bioglass (BG)-hydroxyapatite (HA)-halloysite nanotube and chitosan-halloysite nanotube films. The distribution of Hal nanotubes and morphological structure of the clay polymer nancomposite (CPN) were examined using TEM, FE/SEM, FT-IR, EDX, and XRD analysis. The stability of dispersion and pH of deposition were studied. The optimum pH chosen for the deposition of CS-BG-HA-Hal film was 2.5<pH<3 in 30% water-ethanol solvent. SEM and FT-IR analysis illustrated more nanotubes deposition in CS-based film by augmenting concentration of Hal nanotubes from 0.3gL−1 to 0.6gL−1. The CS-BG-HA-Hal deposition mechanisms were considered and discussed. Corrosion resistance analysis revealed that CS-BG-HA/Hal coated samples exhibit improved corrosion resistance than uncoated Ti. The increasing of Hal concentration in CPN film reduced corrosion current density (icorr), and increased corrosion potential (Ecorr) in corrected simulated body fluid (C-SBF) at 37°C. Furthermore, EIS analysis would be more reliable than electrochemical polarization to evaluate corrosion resistance of CS-based coatings containing Hal nanotubes.

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.008
  • Characterization, firing behavior and ceramic application of clays from
           the Gabes region in South Tunisia
    • Authors: Salah Mahmoudi; Ali Bennour; Ezzedine Srasra; Fouad Zargouni
      Abstract: Publication date: Available online 23 September 2016
      Source:Applied Clay Science
      Author(s): Salah Mahmoudi, Ali Bennour, Ezzedine Srasra, Fouad Zargouni
      In this study, a part of paper has been conducted on geological survey of Gabes clays and their surroundings; so we can focus on the highest thicknesses of clay sediments, for subsequent investigation or exploration. The greatest part of work focuses on the mineralogical, chemical, physical, and geotechnical tests carried out on Creatceous clays collected from the Zimlet El Beida in Gabes area (South-eastern Tunisia). Firing behavior and ceramic application are also conducted for these clay materials. The mineralogy study shows illitic clays; however, other clay minerals, such as kaolinite, mixed-layer I/Sm and chlorite are also present. The mineralogical phases during the firing process were recorded at 300, 600, 800, 1000 and 1150°C for 3h with heating rate of 10°C/min. The main transformations were observed at 1000°C with the appearance of new crystalline phases, such as diopsite, cristobalite, mullite and spinel. The chemical analysis indicates that these clays are notably siliceous. The alkali content (K2O+Na2O) is high (~ 4.13%), thus explaining why these clays can be fired at relatively low temperatures. The amount of alumina and iron oxide, with an average of 16.42 and 7.07% respectively, is variable. The tests show that these clays have medium plasticity values (PI =14–20%). The firing shrinkage and the expansion are limited. A lower firing and drying temperature can be translated into significant energy savings. Technical tests show that the properties fall within the ceramic International Standards (ISO). Ceramic tiles made of these clays have appropriate characteristics without defects and can be classified in group BIII and BIIb according to the European Standard NF EN 159 (1991).

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.023
  • Reduction of filler networking in silica based elastomeric nanocomposites
           with exfoliated organo-montmorillonite
    • Authors: Maurizio Galimberti; Valeria Cipolletti; Serena Cioppa; Angela Lostritto; Lucia Conzatti
      Abstract: Publication date: Available online 24 September 2016
      Source:Applied Clay Science
      Author(s): Maurizio Galimberti, Valeria Cipolletti, Serena Cioppa, Angela Lostritto, Lucia Conzatti
      Montmorillonite with dimethyl di(hydrogenatedtalloyl) ammonium as the compensating cation was added to a silica based elastomeric composite and the hybrid filler system led to reduction of filler networking phenomenon, better stability of elastic modulus with temperature, enhancement of stresses at all elongations, improvement of ultimate properties. This composite was based on a blend of natural rubber, poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) from anionic polymerization and contained 70 parts per hundred rubber (phr) of silica. The organically modified clay (OC) was below the threshold required to establish an hybrid OC-silica filler network. Such threshold (about 7phr) was estimated by preparing silica based nanocomposites containing various amounts of OC and determining shear storage and loss moduli as a function of strain amplitude. This work demonstrates that exfoliated OC favour lower dissipation of energy of silica based elastomeric composites under dynamic mechanical stresses and paves the way for further large scale applications.
      Graphical abstract image

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.017
  • An elasto-plastic damage model for argillaceous geomaterials
    • Authors: A. Alizadeh; B. Gatmiri
      Abstract: Publication date: Available online 24 September 2016
      Source:Applied Clay Science
      Author(s): A. Alizadeh, B. Gatmiri
      The aim of this paper is to present a new elastoplastic damage model for unsaturated porous media. The proposed model within the context of poromechanics is intended for constitutive modelling of geomaterials which show two (irreversible) dissipative aspects involving plastic flow and damage. Independent stress state variables, namely net stress and suction, are adopted as stress variables of the model. Barcelona Basic Model is extended to a non-isothermal formulation and is coupled to a damage formulation using damage dependent yield surface and damaged stress variables. The stress state variables are transformed into the damaged state through the definition of effective damaged suction and effective damaged net stress in the framework of Continuum Damage Mechanics (CDM). Damage effects on intrinsic permeability and transfer laws are also taken into consideration. The model has been implemented in Θ-STOCK Code and predictive capabilities of the model have been evaluated against experimental results from the literature. The model is validated by comparing the numerical results with experimental results of argillites and results of an elastodamage model. The proposed model is also shown to give satisfactory simulation results which match the experimental data from a heating test on bentonite samples.

      PubDate: 2016-09-24T13:06:18Z
      DOI: 10.1016/j.clay.2016.09.009
  • Facile synthesis of thermally reduced graphene oxide-sepiolite nanohybrid
           via intercalation and thermal reduction method
    • Authors: M.R. Vengatesan; S. Singh; S. Stephen; K. Prasanna; C.W. Lee; V. Mittal
      Abstract: Publication date: Available online 13 September 2016
      Source:Applied Clay Science
      Author(s): M.R. Vengatesan, S. Singh, S. Stephen, K. Prasanna, C.W. Lee, V. Mittal
      Hybrid thermally reduced graphene oxide-sepiolite (TRGO-Sep) nanocomposite has been synthesized using via the intercalation of cetyltrimethylammonium chloride (CTAC) with sepiolite (Sep) and graphene oxide (GO) followed by thermal reduction. The physico-chemical characterization of the hybrid was evaluated by wide angle X-ray diffraction (WAXRD), X-ray photoelectron spectroscopy (XPS) and scanning & transmission electron microscopy. The existence of characteristic (110) reflection of sepiolite at 2θ=7.48° confirmed the presence of Sep in the TRGO-Sep hybrid. BET analysis resulted that the surface area of the hybrid material was found to 128.2m2/g. TEM analysis confirmed that the stacking of one dimensional Sep on the graphene sheets.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.006
  • Evaluation of the physiochemical properties and catalytic performance of
           mixed metal oxides-carbon nanotubes nanohybrids containing carbon
           nanotubes with different diameters
    • Authors: Wen Li; Beini Gong; Pingxiao Wu; Shanshan Yang; Qiliang Yang; Zhi Dang; Nengwu Zhu
      Abstract: Publication date: Available online 13 September 2016
      Source:Applied Clay Science
      Author(s): Wen Li, Beini Gong, Pingxiao Wu, Shanshan Yang, Qiliang Yang, Zhi Dang, Nengwu Zhu
      In this study, three types of oxided multi-wall carbon nanotubes (o-MWCNT) with different diameters and oxygen-containing group content were used to synthesize Layered double hydroxides/mixed metal oxides-carbon nanotubes (LDH/MMO-CNT) nanohybrids via a homogeneous urea precipitation method. The surface morphology, structure, graphitization of as-prepared nanohybrids were investigated by Scanning electron microscopy, X-ray diffraction and Raman measurements, etc. The results showed that 3D hierarchical honeycomb nano-structured MMO-CNT was obtained when adding o-MWCNT with a diameter <8nm during preparation. And addition of o-MWCNT with a diameter >30nm; resulted in formation of a structure in which 1D CNT coupled with layers of 2D LDH/MMO with a “line-face” morphology. The results of bisphenol A degradation showed that addition of o-MWCNT with a smaller diameter led to better catalytic performance of MMO-CNT nanohybrids. It may be attributed to the better graphitization and highly dispersed activated components in the catalyst.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.010
  • Structure, microstructure and mechanical features of ceramic products of
           clay and non-plastic clay mixtures from Tunisia
    • Authors: Hiba Zouaoui; Gisele Laure Lecomte-Nana; Mohamed Krichen; Jamel Bouaziz
      Abstract: Publication date: Available online 13 September 2016
      Source:Applied Clay Science
      Author(s): Hiba Zouaoui, Gisele Laure Lecomte-Nana, Mohamed Krichen, Jamel Bouaziz
      Five clay and non-plastic mineral mixtures (M1, M2, M3, M4 and M5) from Tunisia were investigated for their possible ceramic applications. X-ray diffraction (XRD), thermal analysis (DTA/TG), dilatometry, scanning electron microscopy (SEM) and physical-mechanical analyses were used to assess the phase evolution and microstructure of the mixtures sintered between 900 and 1150°C. The decrease of water absorption and the increase of the bending strength of the samples were due to the formation of both the anorthite and mullite phases and the glassy phase helping to fill the pores. M1 and M2 had the highest values of bending strength at 1150°C. According to the European Norm EN 14411, these mixtures are suggested for porcelainized and fully vitrified stoneware thanks to their low water absorption (0.09 and 0.2%, respectively). M3, M4 and M5 mixtures (with respective water absorption of 2.74, 1.68 and 1.74%) are suitable for the production of vitrified stoneware.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.012
  • Cyclic organic carbonate modification of sodium bentonite for enhanced
           containment of hyper saline leachates
    • Authors: A. Fehervari; W.P. Gates; T.W. Turney; A.F. Patti; A. Bouazza
      Abstract: Publication date: Available online 14 September 2016
      Source:Applied Clay Science
      Author(s): A. Fehervari, W.P. Gates, T.W. Turney, A.F. Patti, A. Bouazza
      Two cyclic organic carbonates (COC), propylene carbonate (PC) and glycerol carbonate (GC), were investigated as saline-resistant modifying agents of Na+-montmorillonite using X-ray diffraction (XRD) and Fourier transform infrared (FTIR). PC has been studied previously and has been used as an effective amendment material of Na+-bentonite for saline applications. In this research GC is proposed as a more effective modifying agent for containing hyper saline leachates. Na+-montmorillonite was reacted with up to 1N sodium chloride (NaCl) and calcium chloride (CaCl2) salt solutions to assess changes in the interlayer spacing (i.e., d-value of the 001 reflection in XRD traces) due to osmotic desiccation, as well as to investigate the mechanism and strength of bonding between GC/PC and Na+-montmorillonite by FTIR. GC/Na+-montmorillonite was strongly resistant against strongly saline sodic salt solution compared to PC/Na+-montmorillonite. CaCl2 solution had a more detrimental effect on COC modified Na+-montmorillonite, however, GC/Na+-montmorillonite appeared to retain more intercalated COC than PC/Na+-montmorillonite when leached by strong calcic salt solutions.
      Graphical abstract image

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.007
  • U(VI) adsorption onto cetyltrimethylammonium bromide modified bentonite in
           the presence of U(VI)-CO3 complexes
    • Authors: Jun Liu; Changsong Zhao; Hong Tu; Jijun Yang; Feize Li; Dongmei Li; Jiali Liao; Yuanyou Yang; Jun Tang; Ning Liu
      Abstract: Publication date: Available online 14 September 2016
      Source:Applied Clay Science
      Author(s): Jun Liu, Changsong Zhao, Hong Tu, Jijun Yang, Feize Li, Dongmei Li, Jiali Liao, Yuanyou Yang, Jun Tang, Ning Liu
      The influence of U(VI)-CO3 complexes on U(VI) adsorption onto cetyltrimethylammonium bromide (CTAB) modified bentonite was investigated using batch adsorption experiments to simulate the feasibility of CTAB-bentonite as an adsorbent for the uranium resources recovery. The adsorption capacity (qe) decreased with increasing pH from 8.9 to 9.5 and dissolved carbonate concentrations, but was significantly improved after cation surfactant modification. The adsorption kinetics was depicted by the pseudo-second-order kinetic equation, where the nonlinear Langmuir and Freundlich models fitted well with the data of CTAB-bentonite. The calculated thermodynamic parameters suggested that the adsorption of U(VI) on material was a spontaneous and endothermic process. In particular, we determined that UO2(CO3)3 4−, UO2(CO3)2 2−, (UO2)2CO3(OH)3 −, UO2(OH)3 − anions may have been adsorbed by anion exchange with bromide ion from the CTAB molecule at high CTAB loading levels according to the uranyl speciation calculations, whereas U(VI)-CO3 complexes adsorption capacity correlated with the proportion of aqueous U(VI) species and the competitive adsorption between CO3 2– anions and U(VI)-CO3 complexes. Additionally, desorption results revealed that the most effective desorption agent was 1.0mol/L HNO3 solution. The findings reported in this study aid in facilitating the extraction of uranium resources from aqueous using CTAB-bentonite and other possible clays, especially from salt lake brines or seawater and the consideration of practical U(VI) species in the natural environment.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.005
  • Removal of anionic and cationic dyes from aqueous solution with activated
           organo-bentonite/sodium alginate encapsulated beads
    • Authors: N. Belhouchat; H. Zaghouane-Boudiaf; César Viseras
      Abstract: Publication date: Available online 15 September 2016
      Source:Applied Clay Science
      Author(s): N. Belhouchat, H. Zaghouane-Boudiaf, César Viseras
      In this study, cross-linked activated organo-bentonite (AOBent)/sodium alginate (SA) composite was prepared by the intercalation of sodium alginate in activated organo-bentonite and the cross-linking reaction between sodium alginate and chlorhydric acid to produce interesting new low cost material for the removal of cationic and anionic dyes (methylene blue (MB) and methyl orange (MO)) from aqueous solutions. Adsorbents were characterized by using X-ray diffraction (XRD), thermal gravimetric analyses (TGA) and Fourier transform infrared spectroscopy (FTIR). Batch adsorption studies were carried out to evaluate the effect of pH solution, the kinetic and the isotherm on the adsorption capacity of the adsorbents. The kinetic of MB and MO adsorption was found to follow a pseudo-second-order kinetic model meanwhile the isotherm was well described by the Langmuir model for all samples. Results obtained from this study suggest the potential of prepared composites for cationic and anionic dyes removal which can also be used easily for clean and ecofriendly processes.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.08.031
  • Adsorption study of reactive dyes onto porous clay heterostructures
    • Authors: J.E. Aguiar; J.A. Cecilia; P.A.S. Tavares; D.C.S. Azevedo; E. Rodríguez Castellón; S.M.P. Lucena; I.J. Silva
      Abstract: Publication date: Available online 16 September 2016
      Source:Applied Clay Science
      Author(s): J.E. Aguiar, J.A. Cecilia, P.A.S. Tavares, D.C.S. Azevedo, E. Rodríguez Castellón, S.M.P. Lucena, I.J. Silva
      The present research evaluates the adsorption of reactive dyes, Remazol Violet 5R (RV5R) and Acid Blue 25 (AB25), using Porous Clay Heterostructures (PCHs) prepared from natural bentonite. Natural bentonite, PCH with silica pillars (Si-PCH) and PCH with silica-zirconia (SiZr-PCH) were characterized by elemental analysis, XRD, N2 adsorption-desorption at −196°C, FT-IR, TG and XPS. The adsorption experiments were carried out in a stirred tank in order to evaluate the effect of pH, contact time and initial concentration. The adsorption isotherms were well fitted by Langmuir (L), Langmuir-Freundlich (LF) and Redlich Peterson (RP) models. The equilibrium data were described using the Langmuir-Freundlich model for both dyes and both materials, obtaining a maximum adsorption capacity of 209.9mgg−1 and 265.9mgg−1 for AB25 using Si-PCH and SiZr-PCH, respectively. In the case of RV5R, the maximum adsorption capacity was 127.07mgg−1 and 185.7mgg−1 for Si-PCH and SiZr-PCH, respectively. The adsorption process takes place by electrostatic interactions between the silanol groups of the PCHs with functional groups of the dyes, such as amine or hydroxyl. From the obtained results, it can be concluded that PCHs showed to be a promising material for the adsorption of dye.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.001
  • Immobilization of Candida antarctica lipase B on kaolin and its
           application in synthesis of lipophilic antioxidants
    • Authors: Sonja Jakovetić Tanasković; Bojan Jokić; Sanja Grbavčić; Ivana Drvenica; Nevena Prlainović; Nevena Luković; Zorica Knežević-Jugović
      Abstract: Publication date: Available online 16 September 2016
      Source:Applied Clay Science
      Author(s): Sonja Jakovetić Tanasković, Bojan Jokić, Sanja Grbavčić, Ivana Drvenica, Nevena Prlainović, Nevena Luković, Zorica Knežević-Jugović
      Lipase B from Candida antarctica was immobilized by adsorption onto laboratory prepared metakaolin. This support has great potential for enzyme immobilization since it has good mechanical characteristics and thermal stability and it is easily obtained from naturally abundant raw kaolin, as presented in this paper. Immobilization process was studied as a function of pH, ionic strength and protein concentration in terms of immobilization and activity yield. It was shown that immobilization occurred via the Langmuir model, and that electrostatic forces were major, but not exclusive contributor for the binding process. The optimum conditions were achieved in 10mM acetic buffer pH5. Biocatalyst obtained under optimum conditions was further successfully used in the synthesis of lipophilic antioxidants, where conversion yields as high as 100% were achieved.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.011
  • Electrochemical modification of saponite for manufacture of ceramic
           building materials
    • Authors: Valentine Chanturiya; Vladimir Minenko; Olga Suvorova; Vera Pletneva; Dmitriy Makarov
      Abstract: Publication date: Available online 17 September 2016
      Source:Applied Clay Science
      Author(s): Valentine Chanturiya, Vladimir Minenko, Olga Suvorova, Vera Pletneva, Dmitriy Makarov
      An effective method of recovering a saponite-containing product and desliming the circulating water of Severalmaz, JSC, has been proposed. The method is expected to enhance the efficiency of diamond recovery from ores and improve the ecological situation by introducing water recycling. Studies of the mineral composition have revealed a higher content of minerals of the smectite group in an electrochemically modified saponite sample (74.5% compared to the initial 68%) and lower (by 4%) quartz and dolomite contents. Using of electrochemically modified saponite in manufacture of building ceramics provides the product with enhanced compressive and bending strengths.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.020
  • Effect of manufacturing methods on the decay of ceramic materials: A case
           study of bricks in modern architecture of Madrid (Spain)
    • Authors: Elena Mercedes Perez-Monserrat; Fernando Agua; Rafael Fort; Monica Alvarez de Buergo; Juan Felix Conde; Manuel García-Heras
      Abstract: Publication date: Available online 18 September 2016
      Source:Applied Clay Science
      Author(s): Elena Mercedes Perez-Monserrat, Fernando Agua, Rafael Fort, Monica Alvarez de Buergo, Juan Felix Conde, Manuel García-Heras
      The appearance and main decay forms in the fair-faced brick façades on the University Campus of Madrid's Faculty of Medicine were taken as a starting point to analyse certain building's construction characteristics and the clay and technology used in brick manufacture. The raw materials consisted in a mix of Miocene marl and red Triassic clays from the Spanish province of Jaén. The exposed face of bricks was characterised by a yellowish tone and smooth, uniform texture that afforded perfect dimensioning and inter-brick alignment. In some bricks this texture was lost, with a concomitant colour change, surface roughness increase and loss of material. Laboratory studies through polarised optical microscope (POM), X-ray diffraction (XRD) and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDS) revealed similar composition in all the bricks, firing temperatures ranging between 800 and 850°C and, with the exception of the exposed surface, not particularly careful manufacture.

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.015
  • Influence of ordering and disordering of organoclay on rheological
           properties of uncured and cured ethylene-octene copolymer nanocomposites
    • Authors: Masoud Tayefi; Mohammad Razavi-Nouri; Alireza Sabet
      Abstract: Publication date: Available online 19 September 2016
      Source:Applied Clay Science
      Author(s): Masoud Tayefi, Mohammad Razavi-Nouri, Alireza Sabet
      In this work, the interplay effects of organoclay (OMt) and curing agent content on the rheological behavior and morphology of uncured and cured ethylene-octene copolymer (EOC)/OMt nanocomposites were studied. The samples with various amounts of OMt (0, 1, 3, 5 and 7wt%) were prepared and dynamically cured using dicumyl peroxide (DCP) at two concentrations (0.5 and 1wt%) in an internal mixer. Morphological studies were conducted on the samples using low angle X-ray scattering and transmission electron microscopy. Different schemes were proposed for showing the morphology of OMt particles within the uncured and cured nanocomposites. Moreover, it was found that the addition of both OMt and DCP had synergistic effects in increasing of the storage modulus of the samples, especially at high frequency region. Other schemes were prepared to show the morphology of OMt platelets after frequency sweep performed on the uncured and cured samples. The rheological data was also analyzed using Carreau-Yasuda model. In addition, in order to better understand the rheological behavior, Cole-Cole plots and the variation of relaxation modulus against time were studied.
      Graphical abstract image

      PubDate: 2016-09-20T12:53:15Z
      DOI: 10.1016/j.clay.2016.09.021
  • Evaluation of hydrotalcite-like compounds with distinct interlaminar
           anions as catalyst precursors in methylene blue photodegradation
    • Authors: Manuel Sánchez-Cantú; M.E. Hernández-Torres; Andrea Castillo-Navarro; Eloína Cadena-Torres; E. Rubio-Rosas; J.M. Gracia-Jiménez; Francisco Tzompantzi
      Abstract: Publication date: Available online 9 September 2016
      Source:Applied Clay Science
      Author(s): Manuel Sánchez-Cantú, M.E. Hernández-Torres, Andrea Castillo-Navarro, Eloína Cadena-Torres, E. Rubio-Rosas, J.M. Gracia-Jiménez, Francisco Tzompantzi
      In this work, two hydrotalcite like-compounds with nitrate and acetate as interlaminar anions (uncalcined and calcined) were evaluated as catalysts in the photodegradation of methylene blue (MB) under visible light irradiation. Materials were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis, Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy. The XRD analysis of the pristine compounds demonstrated that they exhibited the characteristic reflections of hydrotalcite-like compounds as the main crystalline phase. The analysis of the (003) reflection confirmed nitrate or acetate presence in the interlaminar region. However, after annealing spinel and MgO obtaining at 350°C was evidenced in both materials. Major absorbance intensity in the visible region was observed in the acetate-containing samples and the highest MB decomposition was achieved with the acetate precursor sample calcined at 450°C. The photocatalytic activity was attributed to a synergy between the crystalline phases, specific surface area and the band gap energy.
      Graphical abstract image

      PubDate: 2016-09-13T12:14:17Z
      DOI: 10.1016/j.clay.2016.08.028
  • Preparation, characterization and application in controlled release of
           Ibuprofen-loaded Guar Gum/Montmorillonite Bionanocomposites
    • Authors: Joanna Dziadkowiec; Rola Mansa; Ana Quintela; Fernando Rocha; Christian Detellier
      Abstract: Publication date: Available online 13 September 2016
      Source:Applied Clay Science
      Author(s): Joanna Dziadkowiec, Rola Mansa, Ana Quintela, Fernando Rocha, Christian Detellier
      Neutral guar gum-montmorillonite and cationic guar gum-montmorillonite nanocomposites loaded with ibuprofen were prepared, and their ability to control in vitro release of the drug was presented. These materials exhibited a reduced initial burst release effect and sustained release of up to several hours in a pH 7.4 simulated intestinal fluid. Blank experiments suggested a nanocomposite-mediated action. Improved properties were demonstrated for two different clay minerals: Sodium Wyoming (SWy-2) montmorillonite from the Source Clay Repository and a Portuguese montmorillonite from the Benavila bentonite deposit. The prepared materials were based on abundant, low-cost, natural minerals and plant-extracted biopolymers, and were synthesized using a facile method, thus exhibiting a low environmental impact.
      Graphical abstract image

      PubDate: 2016-09-13T12:14:17Z
      DOI: 10.1016/j.clay.2016.09.003
  • Dehydration and rehydration of Zn-hydroxy sulfate minerals with
           interrupted decorated hydroxide sheets
    • Authors: Tsveta Stanimirova; Thomas Kerestedjian; Georgi Kirov
      Abstract: Publication date: Available online 9 September 2016
      Source:Applied Clay Science
      Author(s): Tsveta Stanimirova, Thomas Kerestedjian, Georgi Kirov
      The dehydration-rehydration processes of three Zn-hydroxy sulfate minerals with interrupted decorated sheet structures – osakaite, gordaite and Ca-gordaite were investigated. The obtained products and processes were characterized by DTA-TG-MS, in situ and ex situ PXRD and FTIR. In osakaite structure the two different positions of water molecules cause different ways of dehydration. The derivation of each interlayer molecule results in the formation of discrete phases, with 4, 3 and 1 H2O, without any evidence for dihydrate formation. The process was conducted by both heating and adsorption. The rehydration of these metaphases proceeds reciprocally to the dehydration with relatively high rate at middle and high RH values. The derivation of water molecules from the Zn tetrahedron occurs only on heating. The derivation of only half of the apical molecules was observed. The rehydration of formed hemihydrate metaphase proceeds very slowly even at high RH values. The fully dehydrated phase thus proved to be impossible to form. Structural schemes of monohydrate and hemihydrate phases were proposed. In osakaite structure type all changes occur on the surface of the hydroxide layer, preserving its electrically neutral character, with further possible implications for facilitating intercalation of polar molecules. The negatively charged surface of gordaite hydroxide layer, caused by the occupation of apical position of Zn tetrahedra by Cl− determine dehydration behavior, similar to that of montmorillonite and vermiculite structures. On heating, gordaite and Ca-gordaite form three and two pillared structures with different sizes of interlayer space and different amount of water molecules for each phase. The rate of dehydration and/or rehydration and particular quantity of derived water molecules is controlled by the interlayer cations. In accordance with the high ionic potential of calcium, the dehydration of Ca-gordaite occurs only on heating and the rehydration proceeds at very low RH conditions. To the contrary, the much lower ionic potential of sodium causes the formation of dehydrated gordaite phases by both heating and by adsorption. Similarly to the montmorillonite and vermiculite – these two gordaite minerals can be expected to be used for both cation exchange for interlayer cations and anionic exchange of apical Cl− anion.

      PubDate: 2016-09-13T12:14:17Z
      DOI: 10.1016/j.clay.2016.08.032
  • Hydrothermal synthesis of zinc selenide in smectites
    • Authors: Sonchai Intachai; Nithima Khaorapapong; Makoto Ogawa
      Abstract: Publication date: Available online 8 September 2016
      Source:Applied Clay Science
      Author(s): Sonchai Intachai, Nithima Khaorapapong, Makoto Ogawa
      Nanohybrids of zinc selenide and smectites (a natural montmorillonite and a synthetic saponite) were prepared by a hydrothermal reaction of zinc chloride and sodium selenosulfite in the presence of smectites. The products were characterized by powder X-ray diffraction, scanning and transmission electron microscopies, thermogravimetric analysis, as well as, UV–visible and photoluminescence spectroscopies. The round-shaped zinc selenide nanoparticles with the average diameter of 1–4nm formed in the interlayer space of smectites, which gave the absorption onsets at 379–456nm for montmorillonite system and at 475nm for saponite system. Additional absorption onsets were observed at around 478–665nm for montmorillonite system and at 609–682nm for saponite system, suggesting the larger-sized particles formed at the external surfaces. The photoluminescence observed in the wavelength range of 357–360nm was interpreted to the formation of zinc selenide nanoparticles in smectites. The increase of the photoluminescence intensities of all the products (from 35 for bulk ZnSe to 126–294 for ZnSe(n)-smectites) was thought to be caused by the interactions with smectites and/or size and shape of ZnSe formed in the hybrids.
      Graphical abstract image

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.09.002
  • Surface morphological analysis and water vapor barrier properties of
           modified Cloisite 30B/poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
    • Authors: Madjid Farmahini-Farahani; Avik Khan; Peng Lu; Alemayehu H. Bedane; Mladen Eic; Huining Xiao
      Abstract: Publication date: Available online 9 September 2016
      Source:Applied Clay Science
      Author(s): Madjid Farmahini-Farahani, Avik Khan, Peng Lu, Alemayehu H. Bedane, Mladen Eic, Huining Xiao
      In this work, bionanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared via a solution intercalation process using two types of organomodified clay minerals (0 to 40w%). The effect of Cloisite®30B (C30B) and an intercalated clay mineral, which was synthesized via ring opening polymerization of polyhydroxybutyrate in the presence of Cloisite®30B (PHB-C30B), on the wettability of the assemblies has been investigated in detail. Moreover, phase morphology of the nanocomposite films was investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The moisture adsorption of PHBV and its nanocomposite films was determined using Belsorp-Max. The nanocomposite films derived from PHB-C30B exhibited higher wettability than those derived from C30B. An explanation, based on the surface topographies, has been proposed. Phase morphology, filler dispersion and root mean square roughness (RMS) were also analyzed. The results revealed the impact of aggregates on water vapor transmission rate (WVTR) and contact angle of the composites.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.08.033
  • Mineralogical characterisation and surface properties of sepiolite from
           Polatli (Turkey)
    • Authors: Jara
      Abstract: Publication date: October 2016
      Source:Applied Clay Science, Volume 131
      Author(s): M. Suárez, J. García-Rivas, E. García-Romero, N. Jara
      Sepiolite is one of the most important industrial minerals, due primarily to its surface properties related to its structure. Sepiolite contains alternating 2:1 polysomes that produce tunnels at the inner part of the fibre and channels at the edge of the fibre. Sepiolite is a mineral with notably wide variations in the crystal-chemistry, crystallinity and texture, depending on the formation conditions, which results in highly different characteristics and properties. In this work, six sepiolite samples from the Polatli area (Turkey) are studied, comparing their mineralogical and textural features. The mineralogical composition of the samples is similar: carbonates constitute the main impurities, dolomite appears in all samples studied in different proportions, and small amounts of calcite, quartz and palygorskite have been identified. There is a variation in almost all the reflections of sepiolite, the 110 d-spacing ranges between 12.31Å and 12.05Å, this variation is related to the crystal-chemistry of the mineral. The impurities are clearly identified in the IR spectra, in which in addition to the carbonates the presence of the palygorskite polysomes is also detected by the band located at ~3620cm−1. The differences in the surface properties found in this study (specific surface area between 122m2 g−1 and 376m2 g−1 and microporous area between 55m2 g−1 and 168m2 g−1) cannot be related only with the content in impurities, but with the texture and the possible presence of intergrowths.

      PubDate: 2016-09-09T11:52:34Z
  • A facile method to fabricate N-doped graphene-like carbon as efficient
           electrocatalyst using spent montmorillonite
    • Authors: Shanshan Yang; Pingxiao Wu; Liya Chen; Ligui Li; Zhujian Huang; Shuai Liu; Liping Li
      Abstract: Publication date: Available online 6 September 2016
      Source:Applied Clay Science
      Author(s): Shanshan Yang, Pingxiao Wu, Liya Chen, Ligui Li, Zhujian Huang, Shuai Liu, Liping Li
      Montmorillonite (Mt), as an efficient adsorbent, has been widely applied in the treatment of wastewater. However, it is important to develop appropriate disposal methods, which are currently lacking for spent Mt after adsorption. We utilized Mt after adsorption of tetracyclines (TC) as carbon source to obtain a by-product, N-doped graphene-like carbon-based electrocatalysts (TC-C), by a facile and low cost pyrolysis strategy. Physicochemical and electrochemical characterization of TC-C indicated that the resultant TC-C was made up of many ultrathin nanosheets, which resembled the morphology of graphene, and it had a large Brunauer-Emmett-Teller surface area with narrow slit-like pores. Nitrogen doping was evaluated through X-ray photoelectro-spectra measurements and four nitrogen-bonding configurations were identified and quantified, including pyridinic N, pyrrolic N, graphitic N and pyridinic N+–O−. Electrochemical studies showed that TC-C exhibited high catalytic activity for the oxygen reduction reaction (ORR) in alkaline medium with outstanding methanol tolerance compared to the commercial Pt/C catalysts. Furthermore, the effect of the adsorbed amount of TC on the ORR activity of TC-C was slight and the pyrolysis temperature of 700°C was demonstrated to be the optimal temperature for the pyrolysis process in the recycling of spent Mt.
      Graphical abstract image

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.08.030
  • Illitization of Late Devonian-Early Carboniferous K-bentonites from
           Western Pontides, NW Turkey: Implications for their origin and age
    • Authors: Ömer Bozkaya; Asuman Günal-Türkmenoğlu; M. Cemal Göncüoğlu; Özge Ünlüce; İsmail Ömer Yilmaz; Paul A. Schroeder
      Abstract: Publication date: Available online 6 September 2016
      Source:Applied Clay Science
      Author(s): Ömer Bozkaya, Asuman Günal-Türkmenoğlu, M. Cemal Göncüoğlu, Özge Ünlüce, İsmail Ömer Yilmaz, Paul A. Schroeder
      K-bentonite (tephra) layers are exposed as thin beds within Late Devonian-Early Carboniferous carbonates of the Yilanlı formation at four different locations in northwestern, Turkey. Clays separated from K-bentonites in the Gavurpınarı, Yılanlı Burnu (Bartın) and Çimşir Çukurları (Şapça) quarries and the Güdüllü-Gökgöl highway tunnel section near Zonguldak were analyzed by X-ray diffraction, optical, scanning and high-resolution transmission electron microscopy and inductively coupled plasma-mass spectrometry. The clay mineralogy is dominated by illite and mixed-layer illite-smectite (I-Sm) along with subordinate amounts of kaolinite, dolomite, calcite, quartz, feldspar, and gypsum. Morphologically, platy shaped illite is the major clay mineral in the Gavurpınarı and Yılanlı Burnu sites, while sponge-like to platy shaped mixed-layer illite-smectites occur in the Şapca Çimşir Çukurları and Gökgöl sites. Illite Kübler index (KI, Δ°2θ) and polytype data indicate high-grade diagenesis for illite-bearing site, and low-grade diagenesis for I-Sm-bearing sites. Lattice d060 values (Ǻ) of illite and I-Sm reflect a dioctahedral composition, with relatively larger d060 values in the Yılanlı Burnu site, which is related to Mg incorporation into the octahedral layer from dolomitic limestone host-rocks Illites have relatively lower tetrahedral Al substitution and higher octahedral Fe and Mg substitutions compared to those of I-Sm. Illites with at phengitic composition occur in the Gavurpınarı and Yılanlı Burnu sites, whereas muscovitic composition for Şapca Çimşir Çukurları site. Chondrite-normalized rare earth element patterns for the Gavurpınarı and Yılanlı Burnu sites exhibit similar trends, with relatively higher values when compared to trends for the Şapça Çimşir Çukurları sites. Oxygen (δ18O) isotope values of illites and I-Sm range from 17.7 to 21.9‰ (V-SMOW), whereas hydrogen (δD) isotope values range widely from −10.1 to −69.9‰ (V-SMOW). The depleted values of δ18O values for the Gavurpınarı site imply geologically sudden crystallization under higher temperature conditions. K/Ar ages of different size illite fractions indicate the presence of older detrital illites (2μm) together with younger diagenetic fractions (0.5μm) that correspond with an increase of 2M 1 polytype in the coarser fraction. Illitization ages of K-bentonites in the Bartın area indicate an Early Permian event corresponding to the Variscan orogeny, whereas the illitization of K-bentonites in the Zonguldak area is Early Jurassic in age, related to the Cimmerian deformation in the region.

      PubDate: 2016-09-09T11:52:34Z
      DOI: 10.1016/j.clay.2016.08.020
  • Effect of GGBFS and lime binders on the engineering properties of clay
    • Authors: Mahdi Keramatikerman; Amin Chegenizadeh; Hamid Nikraz
      Abstract: Publication date: Available online 3 September 2016
      Source:Applied Clay Science
      Author(s): Mahdi Keramatikerman, Amin Chegenizadeh, Hamid Nikraz
      Although lime is one of the most suitable binders in soil improvement projects, the associated environmental impact and some accompanying mechanical deficiencies should not be ignored. Partial substitution of lime with other binders is one of the ways of reducing the associated harm and improving the engineering properties of lime. This study investigated the effect of the partial substitution of lime with ground granulated blast furnace slag (GGBFS) on the strength and mechanical properties of lime stabilised clay by performing a total of 246 volumetric shrinkage strain (VSS), unconfined compressive strength (UCS) and ring shear (RS) tests. The VSS results demonstrated that the addition of GGBFS to lime is very effective in reducing the volumetric shrinkage of lime stabilised clay, and that the reduction in volumetric shrinkage behaviour is linearly related to curing period. The UCS results revealed that the partial replacement of lime with GGBFS led to significantly higher compressive strength for all ageing periods. The ring shear results also demonstrated that the partial replacement of lime with GGBFS led to a greater shear strength. Moreover, microstructural studies were performed to better understand the reactions of the mixtures. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) carried on selected specimens revealed that the addition of GGBFS in a lime stabilised clay results in production of the cementitious products in a faster rate. X-ray powder diffraction (XRD) test results revealed that the main hydration products are cementitious products such as calcium silicate hydrates (CSH), calcium aluminates (CAH).

      PubDate: 2016-09-04T11:41:46Z
      DOI: 10.1016/j.clay.2016.08.029
  • Thermal gelation properties of carboxymethyl cellulose and
    • Authors: Abdelhakim Benslimane; Ilies Mohamed Bahlouli; Karim Bekkour; Dalila Hammiche
      Abstract: Publication date: Available online 3 September 2016
      Source:Applied Clay Science
      Author(s): Abdelhakim Benslimane, Ilies Mohamed Bahlouli, Karim Bekkour, Dalila Hammiche
      The aim of this work was to study the thermal behavior of carboxymethyl cellulose (CMC) aqueous solutions and bentonite-CMC mixtures, from room temperature to higher temperatures, above gelation, using a rheological analysis. The rheological properties of aqueous CMC solutions and bentonite-CMC dispersions at different mass concentrations of CMC (0.1, 0.5, 1.0 and 2.0wt%) were investigated at different temperatures (20, 40, 60 and 80°C) using large deformation rheological measurements. Viscosity measurements show that for both CMC solutions and bentonite-CMC dispersions sudden changes in viscosity occur as the temperature increases. The viscosity is found to decrease below a critical temperature which corresponds to a cloud point or gelation temperature. Above this later, the viscosity increases dramatically with temperature. Hydrophobic interaction is postulated to be the cause of gelation.

      PubDate: 2016-09-04T11:41:46Z
      DOI: 10.1016/j.clay.2016.08.026
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