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  Subjects -> EARTH SCIENCES (Total: 649 journals)
    - EARTH SCIENCES (467 journals)
    - GEOLOGY (73 journals)
    - GEOPHYSICS (27 journals)
    - HYDROLOGY (21 journals)
    - OCEANOGRAPHY (61 journals)

EARTH SCIENCES (467 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted alphabetically
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: 15)
Advances In Physics     Hybrid Journal   (Followers: 8)
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: 17)
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: 2)
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: 29)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 32)
Arctic Science     Open Access   (Followers: 5)
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: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 8)
Asian Journal of Earth Sciences     Open Access   (Followers: 20)
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: 12)
Atmospheric and Climate Sciences     Open Access   (Followers: 24)
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: 9)
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: 14)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 19)
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 Geochemistry     Hybrid Journal   (Followers: 3)
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: 23)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 7)
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: 10)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
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: 2)
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: 65)
Earth and Space Science     Open Access   (Followers: 7)
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 3)
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: 7)
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: 5)
Electromagnetics     Hybrid Journal   (Followers: 3)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 21)
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: 33)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (Followers: 10)
Exploration Geophysics     Hybrid Journal   (Followers: 3)
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: 15)
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 7)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 25)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 24)
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  
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  
Geography and Natural Resources     Hybrid Journal   (Followers: 4)
Geoheritage     Hybrid Journal   (Followers: 1)
Geoinformatica Polonica : The Journal of Polish Academy of Arts and Sciences     Open Access  
Geoinformatics & Geostatistics     Hybrid Journal   (Followers: 6)
Geological Journal     Hybrid Journal   (Followers: 14)
Geological Magazine     Hybrid Journal   (Followers: 16)
Geology Today     Hybrid Journal   (Followers: 18)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 3)
Geomatics, Natural Hazards and Risk     Hybrid Journal   (Followers: 8)
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 23)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 31)
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: 8)
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: 2)
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: 1)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 3)
Global and Planetary Change     Hybrid Journal   (Followers: 11)
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: 23)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 15)
GSA Today     Partially Free  
Helgoland Marine Research     Open Access   (Followers: 3)
History of Geo- and Space Sciences     Open Access   (Followers: 3)
Hydrobiologia     Hybrid Journal   (Followers: 17)
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: 51)
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: 29)
International Journal of Advancement in Earth and Enviromental Sciences     Open Access   (Followers: 2)
International Journal of Advancement in Remote Sensing, GIS, and Geography     Open Access   (Followers: 23)
International Journal of Applied Earth Observation and Geoinformation     Hybrid Journal   (Followers: 27)
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)
International Journal of Geo-Engineering     Open Access  
International Journal of Geographical Information Science     Hybrid Journal   (Followers: 52)

        1 2 3 | Last

Journal Cover Applied Clay Science
  [SJR: 1.17]   [H-I: 71]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2969 journals]
  • Maintaining shale stability using polyether amine while preventing
           polyether amine intercalation
    • Abstract: Publication date: Available online 17 August 2016
      Source:Applied Clay Science
      Author(s): Shifeng Zhang, James J. Sheng, Zhengsong Qiu
      Polyether amine (PA) has recently been widely applied in water-based drilling fluid to improve shale stability. To study whether PA intercalation and the resulting increase of montmorillonite (Mt) d001-value have a negative effect on shale stability, a PA adsorption test on shale, a shale composites X-ray diffraction (XRD) test and a one dimensional swelling test of shale immersed in solution were conducted. PA can absorb on shale by exchanging Na+ in shale, resulting in a d001-value increase of sodium montmorillonite (Na-Mt) in shale and large vertical displacements, causing lots of micro cracks to develop in the shale with the shale matrix dispersed. For shale immersed in solution with KCl and PA mixed, PA intercalation was reduced and even prevented because K+ can exchange Na+ in the shale first. With the cation hydration reduced by K+ adsorption and the clay layer hydration decreased by PA adsorption on clay layer, vertical displacement was greatly reduced and stability was greatly enhanced for the shale immersed in solution with KCl and PA mixed. As a result, during drilling in shale containing Na-Mt, PA can cause shale instability. Using PA and KCl together can achieve better shale stability compared to using KCl only.


      PubDate: 2016-08-18T10:09:59Z
       
  • Experimental and modeling investigations of cesium and strontium
           adsorption onto clay of radioactive waste disposal
    • Abstract: Publication date: Available online 17 August 2016
      Source:Applied Clay Science
      Author(s): Abdel-Aal M. Abdel-Karim, Ahmed A. Zaki, Waheed Elwan, Mohamed R. El-Naggar, Mahmoud M. Gouda
      Migration of strontium and cesium radionuclide in geohydraulic system is important for safety disposal of radioactive waste containing of these two radionuclides to prevent the migration of radionuclides from the disposal site to provide protection for man and his environment. Geochemical analysis was carried out to investigate the mineral composition of the clay taken from the site to predict the historical and environmental geology of Inshas disposal site. Batch experiments were carried out as a function of pH, solute concentration and under three different temperatures (298°, 313° and 333° K). Sorption capacity of Cs+ and Sr2+ onto clay sample was increased when initial metal ions concentration was increased. Increasing the temperature led to decrease in the sorption of Cs+ and Sr2+ ions. Several kinetic models were used to fit the experimental data and to examine the controlling mechanisms of the sorption processes. The kinetic study showed that sorption followed pseudo-second-order model with a good correlation coefficient (R 2 =0.999) for both studied ions. The experimental sorption data were fitted using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) models. Results showed that the adsorption process was exothermic and favored at low temperature.
      Graphical abstract image

      PubDate: 2016-08-18T10:09:59Z
       
  • Changes in mineral assemblages during serpentine carbonation
    • Abstract: Publication date: Available online 9 August 2016
      Source:Applied Clay Science
      Author(s): Kyoung Won Ryu, Hwanju Jo, Sang Hoon Choi, Soo Chun Chae, Young-Nam Jang
      The carbonation of serpentine (lizardite [Mg3Si2O5(OH)4]) was investigated at a fixed temperature of 290°C under a 30-bar CO2 atmosphere in aqueous solutions of different alkalinities to understand the pH-dependence of the process. To activate the carbonation, the serpentine was heat-treated at 650°C beforehand for 2h. At pH6, the main reaction products were magnesite (MgCO3) and well-crystallized saponite [NaxMg3(Si4Al4−x)O10(OH)2]. The carbonation rate of the Mg ions was limited at acidic pH, and thermogravimetry (TG) analysis of the solid product showed that only 13% carbonation rate of serpentine to magnesite was achieved. The partial dissolution of SiOSi and the resultant Mg-rich solution provided a favorable environment for the formation of saponite. In weakly alkaline and neutral solutions, the rate of carbonation was dramatically enhanced well-faceted rhombohedral magnesite crystals of approximately 1μm in size with a round shape appeared together with a small amount of “curled-flaky type” saponite. The conversion of silicate to carbonate was found to be approximately 45%. As the pH of the solution increased further, the dissociation of carbonic acid accelerated and the free Mg2+ cations then reacted with the bicarbonate ions to form magnesium carbonate. Thus, active conversion to magnesite resulted in poor formation of saponite because of the low concentration of Mg ions in the solution. At pH2, well-crystallized saponite appeared, but magnesite was not observed. Under strongly alkaline conditions, saponite may form by a mechanism wherein the undissolved Mg layer of serpentine is available to act as a substrate for saponite precipitation. The transformation of serpentine to saponite and magnesite was influenced mostly by temperature, alkalinity, and mineral composition.


      PubDate: 2016-08-18T10:09:59Z
       
  • Metakaolin as a precursor of materials for applications in Cultural
           Heritage: Geopolymer-based mortars with ornamental stone aggregates
    • Abstract: Publication date: Available online 14 August 2016
      Source:Applied Clay Science
      Author(s): Marina Clausi, Serena C. Tarantino, Laura Lorenza Magnani, Maria Pia Riccardi, Cristina Tedeschi, Michele Zema
      Potentialities and suitability of metakaolin-based geopolymers in Cultural Heritage have been explored. In particular, in order to evaluate their possible use as restoration materials in conservation of historic manufactures, mortars have been prepared by adding aggregates of Italian ornamental stones to alkali-activated metakaolin with binder/sand ratio of 1:1. To improve workability, geopolymer binders have been synthesized from metakaolin and sodium silicate solution with water/solid weight ratios between 0.33 and 0.66 and SiO2/Al2O3 and Al2O3/Na2O molar ratios of 3.70 and 1.04, respectively, and characterized by several techniques, including mechanical strength tests according to UNI EN 196-1. All binders display good mechanical properties, with compressive and flexural strength values as high as 72MPa and 6MPa, respectively, and decreasing with increasing water/solid ratio. The increase of water in geopolymer formulation has little negative effect on the aluminosilicate gel development and on the strength of these materials. Mortars display a homogeneous and compact matrix, bonded (silicoaluminate aggregates) or interlocked (carbonate) with aggregates. Their compressive strengths fall in the masonry mortars class M20 range. Their pore size distribution guarantees good breathability and adaptability to the substrate. The final materials mimic the original stones, with good aesthetic compatibility.


      PubDate: 2016-08-18T10:09:59Z
       
  • Microbial sulphate-reducing activity over load pressure and density in
           water saturated Boom Clay
    • Abstract: Publication date: Available online 15 August 2016
      Source:Applied Clay Science
      Author(s): Andreas Bengtsson, Karsten Pedersen
      The Boom Clay formation in Mol, Belgium, is studied as a reference host rock for the future Belgian repository for high-level and long-lived radioactive wastes. An apparently dormant sulphate-reducing bacteria (SRB) population in Boom Clay can be activated during repository construction and reduce sulphate to sulphide which may enhance the corrosion of metallic components of the engineered barriers. Thirteen test cells constructed of titanium were installed with saturated Boom Clay cores at three different wet densities, 1800, 1900 and 2000kgm−3. For the purpose of analysing microbial sulphate-reduction to sulphide, a previously developed method utilizing the radiotracer 35SO4 2− was applied. Copper discs were installed towards which produced sulphide diffused and reacted to form CuxS. The amounts of radioactive sulphide on the copper disc surfaces were analysed and the sulphide production rates in the clay were modelled using a diffusion coefficient for sulphate that was determined to 2.2×10−12 m2 s−1 for a fully saturated Boom Clay at a wet density of 2000kgm−3. The diffusion coefficient for sulphide was set to 4.4×10−12 m2 s−1. Heat treated clay (120°C, 48h) was included as negative controls in 4 test cells. The analysis for SRB reported from 107 up to 109 cellsL−1 pore water for 34 sample positions and 5 positions in the negative control clay cores were below detection limit. These numbers were within the range of cultivable bacteria observed previously in Boom Clay. There was no clear cut-off in density with respect to presence of cultivable SRB and sulphide production, but it appeared as if sulphide production was increasingly possible at or below 1800kgm−3. At higher densities, numbers were lower, but the SRB were still cultivable and active which suggests that SRB can be active and produce sulphide in a Boom Clay repository for as long as sulphate is available.


      PubDate: 2016-08-18T10:09:59Z
       
  • Shear strength of GMZ07 bentonite and its mixture with sand saturated with
           saline solution
    • Abstract: Publication date: Available online 15 August 2016
      Source:Applied Clay Science
      Author(s): Long Zhang, De'an Sun, Di Jia
      An experimental study involving direct shear, compression and swelling tests is carried out to investigate the effects of salt solution concentration on mechanical behaviour and microstructural features of a sodium bentonite (GMZ07 bentonite) and its mixture with sand. GMZ07 bentonite is a potential buffer/backfill material for deeply buried geological disposal system to isolate high-level radioactive waste (HLW) in China. Compacted unsaturated GMZ07 bentonite and its mixture with sand saturated with distilled water and sodium chloride solutions at different concentrations (0.2, 0.5 and 1.0mol/L) were first consolidated to a specified stress and then sheared at a constant displacement rate. Test results indicate that shear strength or shear resistance has a noticeable improvement with the increase of salt solution concentration. The test results of GMZ07 bentonite reveal that friction angle increases fairly with the salt solution concentration but the cohesion intercept doesn't. Results of compression tests performed with different salt solution concentrations showed almost the same compressibility for GMZ07 bentonite specimen and its mixture with sand. At last, the microstructure changes associated with variations in the salt solution concentration have been photographed by the Scanning Electron Microscopy (SEM). The photographs show that the increase of salt solution concentration would change the surface roughness and specific surface area of aggregates, which will produce greater interaction among aggregates.


      PubDate: 2016-08-18T10:09:59Z
       
  • Thermal behavior of chlorites of the clinochlore-chamosite solid solution
           series: Oxidation of structural iron, hydrogen release and dehydroxylation
           
    • Abstract: Publication date: Available online 15 August 2016
      Source:Applied Clay Science
      Author(s): Annett Steudel, Reinhard Kleeberg, Christian Bender Koch, Frank Friedrich, Katja Emmerich
      The thermal reactions of natural trioctahedral chlorites of the clinochlore-chamosite solid solution series were studied by simultaneous thermal analysis supplemented by comprehensive mineralogical analysis. The Fe(II) and Fe(III) amount varied between 0.09 and 4.15p.f.u. and 0.06 and 0.22p.f.u., respectively. Content and distribution of Fe(II) determined strongly the thermal behavior. The oxidation of Fe(II) to Fe(III) took place prior or occurred in parallel to the dehydroxylation (DHX) of the interlayer octahedral sheet (IOS). During the oxidation, one electron is transferred to the proton of the octahedral hydroxyl groups forming either H2 in N2 atmosphere or reacting further to H2O in synthetic air (SynA). Thereby, the ratio of mass loss of both DHX of IOS and the 2:1 layers varied in dependency of the Fe(II) position. At high Fe content in chlorites and bulk materials, ferromagnetic phases occurred after heating under N2.


      PubDate: 2016-08-18T10:09:59Z
       
  • Muscovite single layer resolution: Secondary ion mass spectrometry depth
           profile
    • Abstract: Publication date: Available online 16 August 2016
      Source:Applied Clay Science
      Author(s): Monika Jerigova, Vojtech Szöcs, Marian Janek, Dusan Lorenc, Dusan Velic
      Three dimensional depth profile of chemical composition by secondary ion mass spectrometry is still of high interest. Spatial resolution is evaluated on muscovite K0.70Na0.11Ca0.01{[Si3.07Al0.93][Al1.88Fe0.12Mg0.05]O10(OH)2}, forming periodically repeating layers with a single layer of 0.98nm. The depth profile determines the periodic structure as the oscillating ion mass intensities of all constituents which are well represented by Na, O, Si, SiO, and Fe cations, with assigned the absolute (depth profile/correlated) positions from the surface 0.00 (1.60/0.00) nm, 0.16 (1.76/0.20) nm, 0.19 (1.79/0.04) nm, 0.24 (1.84/0.06) nm, and 0.39 (1.99/0.19) nm, respectively. The sequence correlates well with the structure of the single muscovite layer with estimated spatial resolution of 0.07nm. Moreover a novel approach by Fourier transform provides frequency pattern with time and chirp parameters which might be a potential tool to evaluate an atomic mixing process in determination of periodic structures of clay minerals.
      Graphical abstract image

      PubDate: 2016-08-18T10:09:59Z
       
  • Crystallographic, vibrational, thermal and electrochemical properties of
           nacrite-NH4Cl nanohybrid
    • Abstract: Publication date: Available online 11 August 2016
      Source:Applied Clay Science
      Author(s): Nouha Jaafar, Hafsia Ben Rhaiem, Abdesslem Ben Haj Amara
      Si2Al2O5(OH)4·(1−χ)NH4Cl·(1−χ)H2O nanohybrid was prepared by indirect intercalation of ammonium chloride into the interlamellar space of nacrite. The number and position of intercalated ions and water molecules, the layer thicknesses, the stacking mode along the normal to the layer plane ( z ) were determined by modelling X-ray diffraction patterns. Infrared spectroscopy was carried out to observe the interactions between the silicate “network” and the ammonium chloride salt. Thermogravimetric analysis was achieved to study the phase transition of the nanohybrid when the system temperature is increased. Finally, the electrochemical identification of the new nanohybrid material was performed with both parameters: frequency and temperature. Indeed, the prepared compound has a fairly high ionic conductivity at higher temperatures and can be classified as a superionic conductor.
      Graphical abstract image

      PubDate: 2016-08-13T18:59:30Z
       
  • Acid based geopolymerization kinetics: Effect of clay particle size
    • Abstract: Publication date: Available online 11 August 2016
      Source:Applied Clay Science
      Author(s): S. Louati, S. Baklouti, B. Samet
      The kinetic of acid-based geopolymer synthesis was studied for different granulometric classes (125μm, 100μm, 80μm and 63μm) of calcined illito-kaolinitic clay. X-ray diffraction (XRD), infrared spectroscopy (IR), Nuclear Magnetic Resonance (MAS NMR), scanning electron microscopy (SEM) and mechanical measurements were used to investigate geopolymerization kinetic. These techniques have shown that the fineness of the precursor has a significant effect on geopolymerization kinetic and on the mechanical properties of the product. A geopolymerization mechanism including three steps has been proposed: dealumination of metakaolinite, reaction between phosphoric acid PO4 tetrahedral units with SiO layer, on one hand, to form an amorphous (SiOPO) structure, and with leached aluminum, on the other hand, to give crystalline AlPO4 and finally polycondensation in the amorphous phase. The final product is a geopolymeric composite composed by crystalline AlPO4 and amorphous (SiOPO) structure.


      PubDate: 2016-08-13T18:59:30Z
       
  • Density functional theory of electrolyte solutions in slit-like nanopores
           II. Applications to forces and ion exchange
    • Abstract: Publication date: Available online 12 August 2016
      Source:Applied Clay Science
      Author(s): Guomin Yang, Ivars Neretnieks, Luis Moreno, Susanna Wold
      An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) for size-asymmetric electrolytes presented in part I is applied to calculate the forces and the ion exchange for Ca- and Na-montmorillonite systems in equilibrium with salt solutions. Our modeling shows that the DFT calculations are in excellent agreement with Monte Carlo simulations and experimental results. The results indicate that the ion size plays an important role in force-distance relation. Due to the excluded volume effect, the osmotic pressure curve predicted by DFT is shifted towards larger separation distances with increasing the diameter of counterions. Additionally, the interaction can be switched from attraction to repulsion with increasing diameter of counterions from standard to hydrated ionic size. Furthermore, the quantitative characterization of the exchange of calcium for sodium at room temperature on Wyoming bentonite is investigated with the DFT modeling in aqueous solutions at pH7.0. It is found that a significant variation of the selectivity coefficient could be observed with the surface charge density, ionic diameter and interlayer separations. This implies that ion selectivity in compacted bentonite differs from that in dilute smectite dispersions.


      PubDate: 2016-08-13T18:59:30Z
       
  • Effects of kaolinite nanoroll on the flammability of polypropylene
           nanocomposites
    • Abstract: Publication date: Available online 12 August 2016
      Source:Applied Clay Science
      Author(s): Wufei Tang, Sheng Zhang, Xiaoyu Gu, Jun Sun, Xiaodong Jin, Hongfei Li
      Kaolinite nanoroll (Kaol nanoroll) was prepared from raw kaolinite (Kaol), and was then incorporated into polypropylene (PP) with intumescent flame retardant (IFR) to improve the fire performance. The characterization by Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that Kaol was transformed from platy to nanoroll. The flammability and thermostability evaluation by limit oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CONE) and thermal-gravimetric analysis (TGA) showed that Kaol nanoroll showed better synergistic effect on thermal stability and fire resistance to PP than Kaol. CONE data showed that the peak heat release rate (PHRR) values of PP/IFR (436kW/m2), PP/IFR/1.5Kaol (372kW/m2) and PP/IFR/1.5Kaol nanoroll (269kW/m2) nanocomposites were reduced by 70.3, 74.4 and 81.7% compared to that of neat PP (1474kW/m2), respectively. The TGA results indicated that Kaol nanoroll can significantly improve the thermal stability and char residues of Kaol PP/IFR nanocomposites. Morphology and structure analysis of char by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) illustrated that Kaol nanoroll was beneficial to improving the char quality of Kaol PP nanocomposite. The FTIR spectra at different temperatures revealed that Kaol nanoroll will promote the formation of charred layers with the PO and PO complexes in the condensed phase to protect the substrate.
      Graphical abstract image

      PubDate: 2016-08-13T18:59:30Z
       
  • Preparation and characterization of polysulfone/organoclay adsorptive
           nanocomposite membrane for arsenic removal from contaminated water
    • Abstract: Publication date: Available online 13 August 2016
      Source:Applied Clay Science
      Author(s): E. Shokri, R. Yegani, B. Pourabbas, N. Kazemian
      Organoclay embedded polysulfone (PSf) nanocomposite membranes were prepared for arsenate removal from contaminated surface water. Prepared membranes consisted of different weight ratios of organoclay to polymer, ranging from 0 to 2.0wt% and were characterized by FE-SEM, XRD, AFM, pure water flux, mechanical strength, contact angle measurement and adsorption experiments. Obtained results showed that pure water flux, surface hydrophilicity, roughness and mechanical strength of the membranes increased as organoclay content increased from 0 to 2.0wt%. XRD analysis confirmed the exfoliated structure of organoclay in membrane when its content increased from 0.5–1.5wt%. Further increase in organoclay content; up to 2.0wt%, resulted in the intercalated structure of dispersed organoclays in membrane matrix. Adsorption kinetic of arsenate was found to follow pseudo-second-order kinetic model and equilibrium data showed good correlation with the Langmuir model. The obtained results also revealed that the arsenate adsorption was most favorable in the neutral pH. Moreover, membrane reusability of the 1.5wt% and 2.0wt% organoclay embedded PSf membranes was assessed by conducting five cycles of adsorption experiments and membrane regeneration in dead-end filtration. Obtained results confirmed the applicability of the prepared membrane for multiple cycles.
      Graphical abstract image

      PubDate: 2016-08-13T18:59:30Z
       
  • Effects of palygorskite dietary supplementation on back fat mobilization,
           leptin levels and oxidative stress parameters in sows
    • Abstract: Publication date: Available online 12 August 2016
      Source:Applied Clay Science
      Author(s): Georgios A. Papadopoulos, Vasileios Kanoulas, Georgios Arsenos, Geert P.J. Janssens, Johan Buyse, Eleni D. Tzika, Paschalis D. Fortomaris
      The effects of dietary supplementation of palygorskite on the metabolic and oxidative parameters during the peripartal period and performance of sows were assessed. Upon insemination sows were allocated to treatments: a) CON (n =23): sows were fed a basal diet; b) PAL (n =21): sows were fed the basal diet supplemented with 7g/kg feed palygorskite; and c) PAL+ (n =23): sows were fed the basal diet supplemented with 8g/kg feed of a palygorskite compound product. Sow plasma samples (n =10/treatment) were obtained at days 108 of gestation, 1 and 14 postpartum. Leptin levels were higher in PAL and PAL+ groups (P <0.001). The levels of thiobarbituric acid reactive substances (TBARS) and ferric reducing ability of plasma (FRAP) were higher in the CON group (P =0.001 and P =0.003, respectively). PAL sows exhibited higher back fat (BF) loss from late gestation to weaning (P =0.015). Litter weight at weaning and litter weight gain during lactation were higher in CON sows (P <0.001). Overall, palygorskite supplementation affected peripartal energy balance of sows, which was characterized by the increased leptin levels and BF mobilization and accompanied by a decreased oxidative stress.


      PubDate: 2016-08-13T18:59:30Z
       
  • Gas migration in pre-compacted bentonite under elevated pore-water
           pressure conditions
    • Abstract: Publication date: Available online 8 August 2016
      Source:Applied Clay Science
      Author(s): Caroline C. Graham, Jon F. Harrington, Patrik Sellin
      Pre-compacted bentonite has long been proposed as a primary component of an engineered barrier system for the safe geological disposal of radioactive waste. Selection of properties such as the clay composition, compaction-state and clay-to-sand ratio varies in different disposal concepts. However, a sound understanding of the gas transport properties of the barrier material is often considered a necessary part of safety case development for a geological disposal facility. In this study, results are presented from two gas injection experiments conducted in Mx80 bentonite, under elevated pore-water pressure conditions. Test observations indicate that the conditions necessary for gas to enter this material are remarkably consistent, irrespective of the applied water pressure. As expected, an association is noted between the total stress experienced by the clay and the gas pressure at the moment of entry. Gas migration is interpreted as occurring by the formation and propagation of dilatant pathways within the bentonite. Local pore-pressure and stress measurements indicate that significant reworking of the clay can occur, resulting in meta-stable episodes of ‘pressure-cycling’, as gas seeks a stable escape pathway. These findings demonstrate the potential for ‘phases’ of pathway development and propagation within the buffer, resulting in successive migration episodes over the repository lifetime. Experiments also show the potential for gas entry into the buffer to occur as a result of declining pore-water pressure conditions. As such, the influence of significant deviations from hydrostatic conditions (for example, resulting from glacial loading) should not be neglected when considering gas interaction with the buffer over long timescales.


      PubDate: 2016-08-10T18:45:15Z
       
  • Development of an industrial mineralogical framework to evaluate mixtures
           from reservoir sediments for recovery by the heavy clay industry:
           Application of the Durance system (France)
    • Abstract: Publication date: Available online 10 August 2016
      Source:Applied Clay Science
      Author(s): Frédéric Haurine, Isabelle Cojan, Marie-Anne Bruneaux
      The use of dam reservoir sediments would contribute to preserving non-renewable resources, offer alternative raw materials for the heavy clay industry, and reduce the silting of dams and the environmental impact of its dispersal following dredging. The aim of this work is to present the structure and application of a mineralogical industrial framework (MIF) in the evaluation of reservoir sediments as a replacement for natural raw materials in the heavy clay industry. The MIF is composed of two ternary plots based on the dominant minerals (quartz, clay minerals (imparting plasticity for shaping and cohesion after drying and firing), feldspars, chlorite and muscovite, and carbonates) and clay mineral assemblages (illite, kaolinite and swelling clay minerals) from 36 industrial mixes. The application of the MIF to reservoir sediments of the Durance system indicates that they fall outside of the industrial domain due to high contents of illite and silicate minerals (upstream Durance) or carbonates (middle Durance and Verdon stream). This conclusion is supported by the technical impossibility of extruding the upstream sediments and the occurrence of cracks on the specimen bars from the carbonate-rich sediments. Finally, we demonstrate that the Durance sediments can be recovered by incorporating some opening agent (quartz sand or calcined clay wastes) and mixing sediments from different sites (upstream and middle course) to adjust the grain-size distribution and lower the carbonate content. The ceramic properties of the mixtures (drying and firing linear shrinkage, water absorption and tensile rupture) match the usual values of the heavy clay industry.


      PubDate: 2016-08-10T18:45:15Z
       
  • Swelling potential reduction of Spanish argillaceous marlstone Facies Tap
           soil through the addition of crumb rubber particles from scrap tyres
    • Abstract: Publication date: Available online 6 August 2016
      Source:Applied Clay Science
      Author(s): Carlos Hidalgo Signes, Julio Garzón-Roca, Pablo Martínez Fernández, Maria Elvira Garrido de la Torre, Ricardo Insa Franco
      During construction of road and railway projects, expansive soils may be encountered. Their use as construction material for embankments presents difficulties, due to their tendency to swell or shrink. Traditional solutions include mixing soil with cement or quicklime, or to import materials from other locations. As an alternative to these solutions, the present paper proposes a less expensive and more sustainable solution, consisting in mixing the natural expansive soil with rubber particles obtained from scrap tyres. Especially, the “Facies Tap” (a typical soil of southeastern Spain) is studied in this paper. This soil, which is mainly a white argillaceous marlstone, is mixed with six different amounts of rubber content (2.5, 5, 10, 15, 20 and 25% in terms of weight) and submitted to several geotechnical tests, including compaction, free swelling, unidimensional consolidation, direct shear testing and undrained shear compression. The addition of rubber particles to the soil up to a 15% makes it lighter and less prone to swelling, while compressibility remains similar to the natural soil and the drained shear strength slightly increases. Based on experimental results, the optimum rubber content mixed with the soil to prevent its swelling is established at around 3%.


      PubDate: 2016-08-10T18:45:15Z
       
  • Photoinduced electron transfer between semiconducting nanosheets and
           acceptor molecules in the presence of colloidal clay particles
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Teruyuki Nakato, Manami Shimizu, Hitomi Edakubo, Emiko Mouri
      Binary clay colloids prepared by mixing smectite and other particles can exhibit unusual properties based on physical and chemical interactions between the colloidal particles. We prepared a binary colloidal system of layered fluoroniobate (K2NbO3F) and synthetic hectorite (Laponite) particles and examined photoinduced electron transfer in the colloid to which electron accepting methylviologen (MV2+) was added. Exfoliation and nanosheet formation of the fluoroniobate were not evidenced, but it was transformed in water to 3D crystalline species that was easily settled down. Addition of a large amount of hectorite suppressed the settlement of the fluoroniobate particles to stabilize the colloid for a few days. When MV2+ ions were introduced to the binary colloid, the organic species was adsorbed on the hectorite particles and electron transfer occurred from the fluoroniobate particles to the MV2+ ions upon UV irradiation. Addition of propylammonium ions to the system enhanced the yield and stability of the photoproduct while an optimal amount was found. This was ascribed to the scarifying hole scavenging by the propylammonium species although the photoinduced electron transfer can occur in its absence.
      Graphical abstract image

      PubDate: 2016-08-06T18:26:11Z
       
  • Compressibility and saturated hydraulic permeability of clay-polymer
           composites — experimental and theoretical analysis
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Hanna Haase, Tom Schanz
      In this study, the volumetric behaviour, hydraulic permeability and micro-fabric of clay-polymer composites fabricated by the use of polyacrylamide polymers were experimentally investigated and discussed by use of theoretical multiscale approaches. Composites were varied systematically in composition taking into account constitutive properties controlling clay-polymer interaction, i.e., clay mineralogy (kaolinite and montmorillonite dominated clays with predominantly mono- and divalent counterions, respectively) and polymer charge (nonionic, cationic, anionic). Composites were produced according to their individual maximum adsorbing capacity and prepared to slurry conditions. 1D compression and rebound tests were performed (2–800–25kPa) and the hydraulic permeability was calculated for each loading increment. Additionally, microscopic investigations in environmental scanning electron microscope were performed. It was found that cationic and anionic polymer adsorption promote aggregated and flocculated clay fabrics, respectively, whereas nonionic polymers promote dispersed clay fabrics. Macroscopically, this led to an increase in void ratio at the same stress level as well as to an increase (cationic polymers) or decrease (nonionic polymers) in hydraulic permeability. Micro- and macroscopic findings were theoretically analysed by use of diffuse double-layer (DDL) theory and cluster-model. A modified approach of DDL theory accounting for the effect of adsorbed nonionic polymers on the electric potential in the nearfield of clay mineral surfaces was derived. Theoretical results were found to be in good agreement with experimental results on volumetric behaviour. By use of cluster-model, hydraulic permeabilities were found to correlate to the microscopic findings on clay micro-fabric.


      PubDate: 2016-08-06T18:26:11Z
       
  • Physico-chemical characterization of lake pigments based on
           montmorillonite and carminic acid
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Frédéric Fournier, Laurence de Viguerie, Sebastien Balme, Jean-Marc Janot, Philippe Walter, Maguy Jaber
      Hybrid materials based on one organic dye, the carminic acid, and montmorillonite have been prepared and characterized by a multi-technical approach. Aluminum and tin II cations were used in the experimental mixtures in order to have a chelating effect with the carminic acid. X-Ray diffraction patterns (XRD) did not highlight any intercalation of the organic molecule in the interlayer space, a result confirmed by transmission electron microscopy (TEM) micrographs. The fixation of the organic molecules on the phyllosilicates was then investigated by 13C solid state nuclear magnetic resonance (NMR) and time resolved fluorescence spectroscopies. The spectra showed the role that the ketone and catechol functions of the dye played for its fixation and stressed on the decrease of its mobility when the lake pigment was formed. The role of the clay edges and/or surface was highlighted by this set of experimental data.
      Graphical abstract image

      PubDate: 2016-08-06T18:26:11Z
       
  • Editorial Board
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130




      PubDate: 2016-08-06T18:26:11Z
       
  • Structural Characterization of lamellar compounds
    • 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
       
  • Correlation between the d-value and the M2+:M3+ cation ratio in
           Mg–Al–CO3 layered double hydroxides
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): E.S. Zhitova, S.V. Krivovichev, I.V. Pekov, V.N. Yakovenchuk, Ya.A. Pakhomovsky
      Twenty-six samples of natural layered double hydroxides (LDHs: hydrotalcite, pyroaurite and quintinite) from various localities worldwide have been studied by means of single-crystal, powder X-ray diffraction and electron microprobe analysis. High crystallinity of samples allowed for the good accuracy of the measured d-values and reliable values of the M2+:M3+ ratios. Based on the obtained data, it has been found out that d-value for LDHs depends upon the M2+:M3+ ratio that can be explained by purely crystal chemical reasons. The ideal d-values for M2+:M3+ =2:1 (quintinite group) and 3:1 (hydrotalcite group) are 7.56 and 7.80Å, respectively, whereas intermediate cation ratios correspond to the intermediate d-values. The observed quantitative correlation between d-value and M2+:M3+ cation ratio for carbonate LDHs can be described by the linear function d =0.2385× R +7.0852 (R=M2+:M3+), which allows for the estimation of M2+:M3+ on the basis of d-value and vice versa.
      Graphical abstract image

      PubDate: 2016-08-06T18:26:11Z
       
  • Ultrasound assisted preparation of chitosan–vermiculite
           bionanocomposite foams for cadmium uptake
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Erika Padilla-Ortega, Margarita Darder, Pilar Aranda, Rubia Figueredo Gouveia, Roberto Leyva-Ramos, Eduardo Ruiz-Hitzky
      The objective of this work was the development of functional bionanocomposites based on the intercalation of the cationic biopolymer chitosan in natural or in organically modified vermiculite samples under experimental conditions involving ultrasound irradiation. The resulting materials were processed as macroporous foams with the aim to apply them in the removal of Cd(II) ions from aqueous solution. Physicochemical characterization confirmed the intercalation of chitosan into the interlayer space of vermiculite, causing the exfoliation of VU layers in those bionanocomposites. They were processed as foams by means of freeze-drying resulting in materials that show interconnected elongated macropores with average diameter around 150–200μm, and the material in the cell walls exhibited a tendency to organize in parallel planes. The adsorption equilibrium data of Cd(II) on the bionanocomposite foams, carried out in batch mode, was interpreted with the Langmuir, Freundlich and Prausnitz–Radke (P–R) isotherm models, and the P-R isotherm showed the best fit to the experimental data. The adsorption capacity was increased by raising the solution pH, which most likely favors a chelation mechanism between the chitosan chains and the Cd(II) cations. The chitosan–vermiculite bionanocomposites with the highest chitosan content showed exceptionally high adsorption capacity values, at least three times higher than those of the individual components.


      PubDate: 2016-08-06T18:26:11Z
       
  • Functional nanohybrid materials derived from kaolinite
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Gustave Kenne Dedzo, Christian Detellier
      The first studies reporting the intercalation of organic compounds in kaolinite appeared in the 1960's. From that time, many advances have been achieved in this field. They are mainly concerned with the mastering and control of the intercalation processes, with the elucidation of various structural interactions between the intercalated compounds and the functionalities of the interlayer spaces, and with the covalent grafting of a variety of compounds on the internal surfaces. A new type of nanohybrid materials was developed, which displayed several potential interesting applications in various research area as clay polymer nanocomposites, adsorbents, electrochemical sensors or catalysts, among others.


      PubDate: 2016-08-06T18:26:11Z
       
  • Layered double hydroxides: Efficient fillers for waterborne nanocomposite
           films
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Cyril Veschambres, Matilte Halma, Elodie Bourgeat-Lami, Laurent Chazeau, Florent Dalmas, Vanessa Prevot
      Using Layered double hydroxides (LDH) nanoparticles and film-forming latexes, waterborne nanocomposite films were produced by simply a heterocoagulation and solvent casting process. Self-standing and transparent films with LDH contents from 2.5 to 15vol% were prepared. The structure, microstructure and mechanical behavior were thoroughly investigated by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), scanning electron microscopy (FIB–SEM) and dynamic mechanical analysis (DMA). Favorable electrostatic interactions between pristine LDH and the latex ensured a good dispersion of the bidimensional LDH platelets in the films. Above a certain content of LDH, the formation of a well-defined cellular LDH network following the starting latex morphology was observed. Such a percolating microstructure induces a large mechanical reinforcement significant of a mechanical percolation behavior.
      Graphical abstract image

      PubDate: 2016-08-06T18:26:11Z
       
  • Drug–clay nanohybrids as sustained delivery systems
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Jae-Hun Yang, Ji-Hee Lee, Hyeon-Ju Ryu, Ahmed A. Elzatahry, Zeid A. Alothman, Jin-Ho Choy
      Biocompatible 2-dimensional layered compounds such as clays and layered double hydroxides (anionic clays) have been explored and utilized in drug delivery system for therapeutic application because they can safely encapsulate drug molecules via intercalation reaction. Therefore, various kinds of drug molecules and bio-functional molecules with cationic or anionic charge have been incorporated into clay delivery carriers, giving rise to the heterostructured layered nanohybrids with chemo-therapeutic and gene-therapeutic functions. Recently, such inorganic delivery systems have received growing attention because their inertness and low toxicity gives rise to safety and stability in bio-systems. Furthermore, the hybridization of drug with clays offers the fascinating features such as controlled and sustained release, improved water-solubility, and even protective and targeted delivery. Unique release behaviors of drugs from the drug–clay nanohybrids are originated from molecular level incorporation, and strong interaction between drug and inorganic layers including electrostatic and hydrogen bonding interactions. In the present review, various drug–clay nanohybrids will be introduced, and their recent development will be highlighted in the viewpoint of oral administration drugs with controlled and sustained release.


      PubDate: 2016-08-06T18:26:11Z
       
  • Beyond smectite-based nanocomposites
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): Pilar Aranda, Christian Detellier



      PubDate: 2016-08-06T18:26:11Z
       
  • Layered double hydroxide/sepiolite heterostructured materials
    • Abstract: Publication date: September 2016
      Source:Applied Clay Science, Volume 130
      Author(s): A. Gómez-Avilés, P. Aranda, E. Ruiz-Hitzky
      This paper reports a new type of heterostructured materials based on the assembly of layered double hydroxides (LDH) to sepiolite fibrous clay. The assembly of Mg-Al and Zn-Al LDH has been explored following two procedures of synthesis: i) co-precipitation of the LDH in the presence of the clay; and ii) LDH reconstruction from the corresponding so-called “layered double oxide (LDO) phase” also in the presence of an aqueous dispersion of the clay. The resulting LDH/sepiolite nanoarchitectures were characterized by diverse physicochemical techniques (XRD, TG-DTA, FTIR, 29Si NMR, SEM and TEM), revealing the interaction of the generated LDH with sepiolite through the silanol groups at the external surface of the silicate. N2 adsorption–desorption isotherms evidence the effect of the sepiolite in providing a stable support for dispersing the LDH particles. The resulting materials show a relatively high external surface area and microporosity, with values depending on the sepiolite:LDH ratio in the final heterostructure. An interesting feature of these nanoarchitectures is related to the dual adsorption properties showing the possibility to simultaneously adsorb both cationic and anionic species. Moreover, the LDH can be transformed in the corresponding double metal-oxide by thermal treatment giving rise to nanoparticles that remain bonded onto the sepiolite fibers, which could be of interest in the preparation of highly disperse metal-oxide catalysts.


      PubDate: 2016-08-06T18:26:11Z
       
  • Pozzolanic reactivity of pure calcined clays
    • Abstract: Publication date: Available online 4 August 2016
      Source:Applied Clay Science
      Author(s): Sofie Hollanders, Rieko Adriaens, Jørgen Skibsted, Özlem Cizer, Jan Elsen
      Eight reference clay samples, 4 kaolinitic, 3 smectitic and 1 illitic clay, were purified and thermally treated in order to determine their pozzolanic reactivity in cementitious materials. The clays were calcined in a fixed-bed electrical furnace at temperatures ranging between 500°C and 900°C. Both raw and calcined clays were characterized by ICP-OES, XRD and BET techniques. Their pozzolanic reactivity was evaluated with clay-lime pastes after 3, 7, 14, 28, 56 and 90days using thermogravimetry (TGA). The results indicate that all kaolinitic clays are highly reactive at a broad range of firing temperatures (500–900°C). The degree of ordering of the raw kaolinite influences the optimal activation temperature and the rate of the calcined clay-lime reaction. The smectitic clays possess a clear optimal calcination temperature of 800°C. Ca-rich smectites are proven to be somewhat more reactive than Na-rich smectites. However, even at 800°C, its reactivity is significantly smaller compared to kaolinite. Hectorite and illite calcined at an optimal temperature of 800 and 900°C, respectively, exhibit poor pozzolanic reactivity.


      PubDate: 2016-08-06T18:26:11Z
       
  • Shear thickening fluids using silica-halloysite nanotubes to improve the
           impact resistance of p-aramid fabrics
    • Abstract: Publication date: Available online 3 August 2016
      Source:Applied Clay Science
      Author(s): Animesh Laha, Abhijit Majumdar
      In this study, p-aramid (Kevlar) fabrics were impregnated with silica and silica-halloysite nanotube based shear thickening fluids to improve the impact resistance performance. Shear thickening fluids (STF) were synthesized using spherical silica particles of 100nm diameter. Two virgin STF were prepared using silica concentrations of 60% and 65% (w/w). Then, halloysite nanotube (Hal nanotube) compounded STF were synthesized by adding Hal nanotube of 0.05, 0.1, 0.2 and 0.5% (w/w) with the existing STF. Rheological study confirmed more intense shear thickening behavior in silica-Hal nanotube compounded STF. Impact resistance of p-aramid fabrics increased drastically after the impregnation with STF. Further improvement in impact resistance was observed after silica-Hal nanotube compounded STF impregnation.


      PubDate: 2016-08-06T18:26:11Z
       
  • Influence of layer charge origin and layer charge density of smectites on
           their aflatoxin adsorption
    • Abstract: Publication date: Available online 3 August 2016
      Source:Applied Clay Science
      Author(s): Ana Luisa Barrientos-Velázquez, Alicia Marroquin Cardona, Lian Liu, Timothy Phillips, Youjun Deng
      The aflatoxin adsorption efficiency of a bentonite depends strongly on the physical, chemical, and mineralogical properties of the smectite, the dominant clay mineral in bentonites. The objective of this study was to determine the effects of the layer charge origin, octahedral cation composition, and layer charge density on the smectites' selectivity and adsorption capacity for aflatoxin. Six smectite samples with different layer charge densities and octahedral cation compositions were evaluated: a montmorillonite (4TX) and a hectorite, which represent smectites with octahedral charge origin; and a beidellite, two saponites from Australia and Spain, and a nontronite, which represent smectites with tetrahedral charge origin. The clay fraction of the smectites was saturated with Na, Ca, and Ba, respectively. Aflatoxin adsorption isotherms were conducted for these smectites. The CEC of one high-charge montmorillonite (5OK) and the nontronite were reduced by Li-saturation and heating. Similar effect of the exchangeable cations was observed in all smectites, but significant differences in the aflatoxin adsorption capacity were observed among the smectites. The octahedrally charged smectites showed higher aflatoxin adsorption than the tetrahedrally charged smectites. The aflatoxin-smectite bonding mechanism was not affected by the layer charge origin or density. Optimal layer charge density was required to have sufficient non-polar sites on the smectite for aflatoxin molecules. High-charge-density smectites had low adsorption capacity and binding affinity for aflatoxin, but aflatoxin adsorption on these smectites can be improved by reducing the layer charge density of the clay mineral. Smectites with octahedral charge increased the interlayer accessibility of aflatoxin molecules. The octahedral cation composition had a negligible effect on the aflatoxin adsorption capacity of smectites.


      PubDate: 2016-08-06T18:26:11Z
       
  • Adsorption of bisphenol A and ciprofloxacin by
           palygorskite-montmorillonite: Effect of granule size, solution chemistry
           and temperature
    • Abstract: Publication date: Available online 3 August 2016
      Source:Applied Clay Science
      Author(s): Tedros Berhane, Jonathan Levy, Mark P.S. Krekeler, Neil D. Danielson
      Adsorption and desorption studies of the endocrine-disrupting compound, bisphenol A (BPA), and the antibiotic ciprofloxacin (CIP) with palygorskite-montmorillonite (Pal-Mt) granules (0.3–0.6mm, 1.7–2.0mm and ≈2.8mm), were done as a function of solution chemistry, temperature, and particle size. The data best fit the Langmuir adsorption model with the smallest and the largest granule sizes, respectively, exhibiting the highest (in mgkg−1, q m =77.3 for BPA; q m =107,000 for CIP) and the lowest (q m =41.0 for BPA; q m =81,000 for CIP) adsorption capacities. CIP adsorption was strongly pH dependent, while BPA adsorption was slightly pH and ionic strength dependent. Thermodynamic parameters indicated BPA and CIP adsorption were spontaneous. Net-adsorption-desorption hysteresis were indicative of irreversible adsorption. FTIR and thermogravimetric analysis (TGA) data corroborate the mechanisms and the level of adsorption for CIP but not for BPA. The smallest and the medium granule sizes, respectively, are appropriate for potential BPA and CIP removal. Capsule abstract BPA and CIP adsorption-desorption data was granule size, experimental pH, ionic strength, and temperature dependent. Adsorption-desorption hysteresis indicated irreversible adsorption.
      Graphical abstract image

      PubDate: 2016-08-06T18:26:11Z
       
  • Reprint of Study of spatial distribution of sepiolite in
           sepiolite/polyamide6,6 nanocomposites
    • Abstract: Publication date: Available online 13 July 2016
      Source:Applied Clay Science
      Author(s): Cristina Fernandez-Barranco, Anna E. Kozioł, Krzysztof Skrzypiec, Michał Rawski, Marek Drewniak, Africa Yebra-Rodriguez
      The enhancement of the technical properties of a Clay/Polymer Nanocomposite (CPN) is related to the homogeneity and dispersion of the filler within the polymer matrix. In this work, samples of pure polyamide 6,6 (PA66) and reinforced PA66 with 1, 3, 5, 7 and 9wt.% of sepiolite have been studied. The samples have been qualitatively analyzed with different microscopy techniques and with X-Ray diffraction and scattering techniques. The images obtained by confocal microscopy show that the sepiolite is homogeneously distributed in the PA66 matrix. The micrographs taken by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that sepiolite fibres are oriented and equidistantly distributed even in the samples with high percentages of sepiolite. TEM images reveal the absence of clusters of sepiolite and good dispersion of the reinforcement within the matrix. The quantification of the dispersion, calculated from the results of Small Angle X-Ray Scattering (SAXS), indicates that the polymer chains are expanded due to the arrangement of sepiolite within the PA66 matrix and that the fibres are properly dispersed in the polymer.


      PubDate: 2016-07-16T19:11:48Z
       
  • Cu-Mg-Al hydrotalcite-like materials as precursors of effective catalysts
           for selective oxidation of ammonia to dinitrogen — The influence of
           Mg/Al ratio and calcination temperature
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Sylwia Basąg, Zofia Piwowarska, Andrzej Kowalczyk, Agnieszka Węgrzyn, Rafał Baran, Barbara Gil, Marek Michalik, Lucjan Chmielarz
      Hydrotalcite originated Cu-Mg-Al mixed metal oxides were studied as catalysts for selective oxidation of ammonia to dinitrogen. Cu-Mg-Al hydrotalcite-like materials with copper content of 5mol% and various molar Mg/Al ratios were synthetized by coprecipitation method and then calcined at 600, 700 and 800°C. It was shown that both Mg/Al ratio as well as calcination temperature are very important synthesis parameters determining selectivity of the studied catalysts in ammonia oxidation process. The catalysts with lower Mg/Al ratio, so higher Al content, were more selective to dinitrogen. Moreover, it was shown that an increase in calcination temperature also resulted in the catalysts with a significantly improved selectivity to dinitrogen. These interesting effects were related to the formation of the Cu-containing spinel phases, which possibly are responsible for high selectivity to dinitrogen in the high temperature range.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Kinetics, isotherms and multiple mechanisms of the removal for phosphate
           by Cl-hydrocalumite
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Yunsheng Jia, Huoyan Wang, Xuesong Zhao, Xiaowei Liu, Yiliu Wang, Qunlong Fan, Jianmin Zhou
      A laboratory study was conducted to evaluate phosphate removal from aqueous solutions by a CaAl-Cl layered double hydroxide (Cl-hydrocalumite). Cl-hydrocalumite was prepared by co-precipitation and was characterized by scanning electron microscopy equipped with energy-dispersive spectrometer (SEM-EDS), powder X-ray diffraction (PXRD), and Fourier transform infrared (FTIR). SEM demonstrated that a crystalline structure was synthesized and PXRD or FTIR spectra revealed that the structure was Cl-hydrocalumite. Adsorption experiments were performed as a function of contact time and initial phosphate concentration. Phosphate adsorption reached equilibrium within 10h, followed by a pseudo-second-order kinetic model with R2 =0.999. The experimental data followed the Langmuir and Fedlich-Peterson isotherm models, and showed a maximum adsorption capacity of ~182.5mgg−1. The Freundlich constant n=3.18>1, represented a favorable phosphate adsorption process. SEM-EDS, PXRD, and FTIR analyses of P-hydrocalumite (after adsorption) were used to elucidate adsorption mechanisms. EDS results indicated that chloride was topotactic, exchanged by phosphate to generate P-hydrocalumite, and partial Cl-hydrocalumite was dissolved. The PXRD and FTIR spectra indicate that P-hydrocalumite was a mixture with a new precipitate, brushite. Phosphate adsorption by Cl-hydrocalumite was topotactic anion exchange combined with dissolution–precipitation. Cl-hydrocalumite was a cost-effective and excellent phosphate adsorbent.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Study on synthesis and characterization of ZSM-20 zeolites from
           metakaolin-based geopolymers
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Qing Tang, Yan He, Yi-pin Wang, Kai-tuo Wang, Xue-min Cui
      This paper presents a novel method for the synthesis of ZSM-20 zeolites. This method based on in situ transformation from a metakaolin-based geopolymer gel is more effective than the traditional hydrothermal method. The crystalline phase, micromorphology and microstructure of the geopolymers and the ZSM-20 zeolite samples were investigated using SEM, XRD and an N2 adsorption apparatus. The experimental results showed that pure ZSM-20 zeolite crystals were obtained without any by-product and with a large BET surface area of 78.52m2/g under optimal conditions. Key factors of the in situ transformation process were studied, such as the alkalinity of the geopolymer gel, the curing conditions and the hydrothermal conditions. The optimum observed conditions were as follows: the modulus of sodium silicate solution (SiO2/Na2O molar ratio) was 1.1, H2O/Na2O molar ratio=7.5, the geopolymers should be cured at 40°C for 3days, and the hydrothermal conditions should be kept at 140°C for 10h.


      PubDate: 2016-06-16T18:00:57Z
       
  • Correlation between chemical and mineralogical characteristics and
           permeability of phyllite clays using multivariate statistical analysis
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): E. Garzón, E. Romero, P.J. Sánchez-Soto
      Phyllite clays are applied as a layer on a surface to be waterproofed and subsequently compacted. For this purpose, phyllite clays deposits can be grouped by their chemical and mineralogical characteristics, and these characteristics can be connected with their properties, mainly permeability, in order to select those deposits with the lowest permeability values. Several deposits of phyllite clays in the provinces of Almería and Granada (SE Spain) have been studied. The results of applying a multivariate statistical analysis (MVA) to the chemical data analysed from 52 samples determined by XRF, mineralogical analysis by XRD and permeability are reported. Permeability, a characteristic physical property of phyllite clays, was calculated using the results for experimental nitrogen gas adsorption and nitrogen adsorption-desorption permeability dependence. According to the results, permeability values differentiated two groups, i.e. group 1 and group 2, with two subgroups in the latter. The influence of chemical as well as mineralogical characteristics on the permeability values of this set of phyllite clays was demonstrated using a multiple linear regression model. Two regression equations were deduced to describe the relationship between adsorption and desorption permeability values, which support this correlation. This was an indication of the statistical significance of each chemical and mineralogical variable, as it was added to the model. The statistical tests of the residuals suggested that there was no serious autocorrelation in the residuals.


      PubDate: 2016-06-16T18:00:57Z
       
  • Kinetics and thermodynamic analysis of the adsorption of hydroxy-Al
           cations by montmorillonite
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Guifang Wang, Xin Su, Yuyan Hua, Shaojian Ma, Jing Wang, Xiaoqiang Xue, Qi Tao, Sridhar Komarneni
      Hydroxy-Al pillaring agent was prepared and used to modify montmorillonite (Mt), and the effects of temperature, initial Al3+ concentration and contact time were investigated by using a batch technique. The results showed that the uptake of Al13 by Mt increased with increasing temperature, initial Al3+ concentration and contact time. The adsorption equilibrium was achieved in 12h as determined by kinetics. The adsorption kinetics demonstrated that the adsorption of Al13 by Mt followed the pseudo-second-order kinetic model. The adsorption isotherms at the temperatures of 40, 60, 80 and 90°C were determined and simulated using Langmuir, Freundlich and Redlich-Peterson models. The three kinds of isotherms could represent the experimental data well. The specific surface areas and pillar density increased while the total porous volumes slightly decreased with increasing Al3+ concentrations. The XRD result showed that adsorbed Al13 ions were located in the Mt interlayer spaces through monolayer adsorption. Thermodynamic analysis of adsorption process showed that the adsorption of Al13 by Mt was spontaneous, endothermic with increasing disorder during the adsorption process and mainly physical in nature.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Photocatalytic degradation of phenol using MgAlSn hydrotalcite-like
           compounds
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Sonia Mancipe, Francisco Tzompantzi, Hugo Rojas, Ricardo Gómez
      MgAl Layered Double Hydroxides (LDH) with molar ratio Mg/Al=3 and MgAlSn containing 5, 10 and 15wt% of tin were synthesized by the co-precipitation method. The solids were characterized by X-ray diffraction (XRD), N2 sorption, infrared spectroscopy (FTIR), Scanning Electron Microscopy coupled to a detector for energy dispersive X-ray spectroscopy microanalysis (SEM/EDS), Transmission Electron Microscopy (TEM) and UV–Vis spectroscopy (UV–Vis) in order to determine the crystalline structure, textural properties, vibrational modes of the LDH, morphology and tin content, as well as the band gap of the solids. The photocatalytic behaviors of synthesized materials were tested in phenol degradation under UV irradiation. The results showed that MgAlSn 15% present the highest activity with 80% degradation of the contaminant molecule after 3hours of exposure to light.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Microbial metabolism in bentonite clay: Saturation, desiccation and
           relative humidity
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): W. Stone, O. Kroukamp, J. McKelvie, D.R. Korber, G.M. Wolfaardt
      Within a Deep Geological Repository for used nuclear fuel storage, compacted bentonite clays are the candidate buffer due to their physical and rheological properties, and their ability to suppress microorganisms. This study focused on the potential for microbial metabolism at bentonite-air interfaces, the influence of relative humidity (RH) and the consequences of metabolic activity on bentonite. Microbial activity, determined by monitoring the concentration of evolved CO2, was sustained at desiccated bentonite-air interfaces at 75% RH (0.6ppm CO2/min after 5days of dessication) but was completely suppressed at 30% RH. Conversely, microbial survival was promoted in dry bentonite, with culturable cell survival up to 3 times higher at lower RH (30%) than higher RH (75%). It was also shown that, under water-saturated conditions, microbial sulphur reduction decreased the clay swell index of uncompacted bentonite, swelling approximately 2.7cm/(g dry weight) less than controls. Notably, natural groundwater salinities were shown adequate to suppress all microbial activity under both saturated and desiccated conditions, confirming that a combination of high bentonite dry density and high salinity inhibits microbial activity, even in microenvironments like surface-air interfaces where swelling pressure limitations may be transiently compromised. Along with the applied need for this knowledge, this study also provided a fundamental opportunity to explore microbial activity in desiccated environments, and suggests that lower RH may promote rapid entry into a dormant cell state and thus more effective long-term adaptation.


      PubDate: 2016-06-16T18:00:57Z
       
  • Effects of imperfect interfacial adhesion between polymer and
           nanoparticles on the tensile modulus of clay/polymer nanocomposites
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Yasser Zare
      This work investigates the effects of incomplete interfacial adhesion between polymer and nanoparticles on the predicted tensile modulus of clay/polymer nanocomposites (CPNs). The Halpin-Tsai and Hui-Shia models which assume the perfect interfacial adhesion commonly overpredict the modulus in CPN. Accordingly, the samples include imperfect interfacial bonding at polymer-filler interface. In this condition, the effective aspect ratio and volume fraction of nanoclay are defined using “L c ” as the essential distance for the normal stress to reach the clay strength and “τ” as the interfacial shear strength. The values of “L c ” and “τ” are calculated for several samples and also, their roles in the predicted modulus are determined. It is shown that low “L c ” and high “τ” result in a significant modulus, because they indicate the great levels of interfacial properties in CPN. Also, the large and thin platelets can produce a high modulus depending to the level of Interfacial parameters.


      PubDate: 2016-06-16T18:00:57Z
       
  • Gas permeability evolution mechanism during creep of a low permeable
           claystone
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Z.B. Liu, J.F. Shao, T.G. Liu, S.Y. Xie, N. Conil
      Clayey rocks, due to its low permeability and self-sealing ability, have been selected as a privilege candidate host rock for underground radioactive waste repository in many countries. The gas permeability evolution is very sensitive to the deformation process in such rocks and can be used as a good indicator of microstructure changes such as the growth of micro-cracks. In this work, the mechanism of gas permeability evolution in the Callovo-Oxfordian (Cox) claystone during a creep deformation is investigated. Firstly, multi-step creep tests with different confining pressures are carried out to characterize gas permeability evolutions under different levels of the deviatoric stress. Secondly, in order to minimize effects of multiple deviatoric loading steps, one-step creep tests are also realized. Throughout all creep tests, the gas permeability is measured by a transient pulse decay method in together with the axial and radial strains. It is first found that the gas permeability of the claystone significantly decreases with the confining pressure or hydrostatic stress. The gas permeability in multi-step creep tests can exhibit a four-stage evolution with the progressive increase of deviatoric stress level, composed of a rapid decrease, a gentle decrease, a gentle increase and a rapid increase. However, the gas permeability is continuously decreasing during one-step creep tests. The permeability change in a one-step creep test can be well correlated with the volumetric strain variation by a logarithmic function. Effects of loading orientation with respect to claystone bedding planes are also investigated.


      PubDate: 2016-06-16T18:00:57Z
       
  • Mechanism of intercalation of polycarboxylate superplasticizer into
           montmorillonite
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Hongbo Tan, Benqing Gu, Baoguo Ma, Xin Li, Chaoliang Lin, Xiangguo Li
      It is well known that polycarboxylate superplasticizer (PC) has a poor clay tolerance, due to huge adsorption amount caused by clay minerals, especially by montmorillonite (Mt). The aim of the paper is to study the mechanism of the interaction of Mt and PC. AA-MA was synthetized by acrylic acid (AA) and methyl acrylate (MA), and PC was synthetized by AA and isopentenol polyoxyethylene ether (TPEG). X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Fourier-transform Infrared Spectroscopy (FTIR), Thermo Gravimetric Analysis (TGA), X-ray Photoelectron Spectroscopy (XPS) and Nuclear Magnetic Resonance (NMR) were used to discuss the structure of the Mt intercalated by polymers including TPEG, AA-MA and PC. The results show that: AA-MA, which is the main chain of PC without long side chain of polyethylene oxide (PEO), only adsorbs on the surface of Mt particles, and it cannot be intercalated into interlayer space of Mt. TPEG containing PEO, the long side chain of PC, can be easily inserted into the interlayer space. Furthermore, it is proved that not the whole molecular but only the long side chain PEO of PC is intercalated into interlayer space, which is the main reason for its huge adsorption amount and less efficient dispersing ability in cement-Mt paste. The results suggest a possibility that those salts or polymers that can preferentially insert into interlayer space of Mt can be utilized to impede the intercalation of the long side chain of PC and improve the clay tolerance of PC.


      PubDate: 2016-06-16T18:00:57Z
       
  • BiVO4/Fe/Mt composite for visible-light-driven degradation of acid red 18
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Tianyuan Xu, Runliang Zhu, Jianxi Zhu, Xiaoliang Liang, Yun Liu, Yin Xu, Hongping He
      This work described a strategy for loading bismuth vanadate (BiVO4) on hydroxy-iron pillared montmorillonite (Fe/Mt), in which vanadate and bismuth were successively loaded on Fe/Mt to synthesize a BiVO4/Fe/Mt composite with high photo-Fenton catalytic activity. The structural characteristics of the resulting materials were studied using X-ray diffraction, inductively coupled plasma mass spectrometry, nitrogen adsorption–desorption isotherms, and UV–vis diffuse reflectance spectra. Then, the photo-Fenton catalytic activity of the obtained catalysts was tested using acid red 18 (AR18) as a model contaminant under visible light irradiation. Furthermore, the concentration of hydroxyl radical (OH) was studied by high performance liquid chromatography. The results indicated that BiVO4 loaded not only on the outer surface but also into the interlayers of Fe/Mt. The 8%BiVO4/Fe/Mt composite exhibited high photocatalytic activity, and the decolorization efficiency, TOC removal efficiency of AR18, and the production of OH by BiVO4/Fe/Mt were higher than those by Fe/Mt. The high removal efficiency of AR18 and remarkable OH generation performance by BiVO4/Fe/Mt should be attributed to the presence of BiVO4, which can accelerate the reduction of Fe3+ to Fe2+ by providing photo-induced electrons from BiVO4. In addition, the leached amount of Fe from BiVO4/Fe/Mt was 0.32mg/L after 180min reaction, much smaller than that from Fe/Mt (0.66mg/L). The results of this work suggest that the introduction of semiconductor materials may be a feasible way for enhancing the photo-Fenton catalytic activity of heterogeneous photo-Fenton catalysts.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Montmorillonite modified with lactim methyl ethers having different ring
           sizes
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Lenka Malinová, Daniel Jaksch, Jiří Brožek
      A series of organically modified montmorillonites (organo-montmorillonites) was prepared by the method of cation exchange using hydrochlorides of lactim methyl ethers derived from cyclic amides (lactams) with varying ring size (five- to thirteen-membered). The content of the organic modifier was determined from the carbon content (elemental analysis) and using the thermogravimetric analysis. The intercalation of lactim methyl ethers into the interlayer space of the aluminosilicate was confirmed by the FTIR spectroscopy. The interlayer distance determined by the X-ray diffraction increased with increasing ring size and was correlated to the values obtained for montmorillonite intercalated by ω-aminoacids derived from lactams. Suitability of montmorillonites organophilized in this way for a preparation of nanocomposites of polyamide6 by in situ intercalation was tested by their swelling in the ε-caprolactam melt. Due to the penetration of the monomer into the interlayer space of the organophilized montmorillonite, the interlayer distance further increased.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Enhanced visible-light photocatalytic activity of kaolinite/g-C3N4
           composite synthesized via mechanochemical treatment
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Zhiming Sun, Guangyuan Yao, Xueyui Zhang, Shuilin Zheng, Ray L. Frost
      A novel kaolinite/g-C3N4 (KA/CN) composite with enhanced visible light-driven photocatalytic activity was prepared through a simple mechanochemical method. The microstructure and interface properties of the obtained nanocomposites were characterized by X-ray diffraction (XRD), surface area measurement (BET), Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscope (HR-SEM), energy dispersive X-ray spectroscopy (EDS), UV–visible diffused reflectance spectroscopy (UV–vis DRS) and photoluminescence spectroscopy (PL). It is indicated that g-C3N4 and kaolinite coexisted in the composite photocatalysts. Compared with the single g-C3N4 or kaolinite and kaolinite/g-C3N4 physical mixtures, the as-synthesized KA/CN composites exhibited significantly enhanced photocatalytic activity after mechanochemical treatment under visible-light irradiation, which was almost 4.0 times that of the pure g-C3N4. The enhanced photocatalytic activity of the kaolinite/g-C3N4 composite could be attributed not only to its high adsorption capacity but also to the synergistic effects between g-C3N4 and kaolinite, effectively reducing the recombination probability of photogenerated electron-hole pairs.


      PubDate: 2016-06-16T18:00:57Z
       
  • Effect of plasma treatment on structure and surface properties of
           montmorillonite
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): P. Čapková, J. Matoušek, J. Rejnek, N. Bendlová, J. Pavlík, M. Kormunda, L. Šplíchalová, V. Pilařová
      Plasma treatment of montmorillonite has been investigated as a prerequisite for design of functional nanostructures, based on clay minerals. The effect of short-term (20s) plasma treatment on structure and bonding of montmorillonite has been analyzed using combination of X-ray powder diffraction and infrared spectroscopy. Results showed that dehydration starts at low discharge power 10W and at 50W is completed. The effect of the plasma treatment was compared to the effect of the heat treatment (8h at 450°C). Both treatments can be considered as similar when dehydration takes place. However, the dehydroxylation does not seem to be triggered by the plasma treatment. Therefore for dehydration only, the plasma treatment can be used instead of much more energy consuming thermal treatment.


      PubDate: 2016-06-16T18:00:57Z
       
  • Editorial Board
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129




      PubDate: 2016-06-16T18:00:57Z
       
  • An evaluation of palygorskite inclusion on the growth performance and
           digestive function of broilers
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Yueping Chen, Yefei Cheng, Weili Yang, Xiaohan Li, Chao Wen, Wenbo Wang, Aiqin Wang, Yanmin Zhou
      Palygorskite (Pal), a natural non-toxic silicate clay mineral with abundant resource reserve on the Earth, has received increasing attention in animal nutrition either as an efficient and safe feed additive or ingredient to promote the growth of animals. The current study was conducted to evaluate the effects of Pal supplementation on the growth performance and digestive function of broilers. 144 one-day-old Arbor Acres broiler chicks were allocated into 3 dietary treatments consisting of 6 replicates with 8 chicks each. Birds in the 3 treatments were given a basal diet supplemented with 0, 0.5mass% and 1.0mass% of Pal for 42days, respectively. The broilers fed diets containing either 0.5mass% or 1.0mass% Pal showed similar growth performance to those given the basal diet. Compared with the control group, the relative weight of the pancreas was increased by Pal inclusion at 42days. 1.0mass% Pal supplementation increased nitrogen retention and organic matter digestibility of broilers during 32 to 34days. Similarly, 0.5mass% Pal inclusion significantly enhanced pancreatic and jejunal lipase activity at 21days. In addition, birds fed diet supplemented with 1.0mass% Pal showed a higher level of jejunal trypsin activity at 42days compared with the control group. The results indicated that dietary Pal supplementation could enhance relative weight of pancreas, nitrogen retention and organic matter digestibility (1.0mass% Pal only), and the activities of digestive enzymes of broilers, which may account for the similar growth performance.


      PubDate: 2016-06-16T18:00:57Z
       
 
 
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