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  Subjects -> EARTH SCIENCES (Total: 644 journals)
    - EARTH SCIENCES (467 journals)
    - GEOLOGY (70 journals)
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    - HYDROLOGY (21 journals)
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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: 14)
Advances In Physics     Hybrid Journal   (Followers: 7)
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: 12)
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: 9)
Annals of GIS     Hybrid Journal   (Followers: 16)
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: 10)
Applied Geomatics     Hybrid Journal   (Followers: 3)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 2)
Applied Remote Sensing Journal     Open Access   (Followers: 15)
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: 14)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 7)
Asian Journal of Earth Sciences     Open Access   (Followers: 19)
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: 1)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 11)
Atmospheric and Climate Sciences     Open Access   (Followers: 23)
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: 19)
Bulletin of Volcanology     Hybrid Journal   (Followers: 16)
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: 17)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 13)
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: 2)
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: 9)
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: 9)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 67)
Earth and Space Science     Open Access   (Followers: 6)
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: 5)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 5)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 6)
Earthquake Science     Hybrid Journal   (Followers: 9)
Earthquake Spectra     Full-text available via subscription   (Followers: 16)
Ecohydrology     Hybrid Journal   (Followers: 9)
Ecological Questions     Open Access   (Followers: 5)
Electromagnetics     Hybrid Journal   (Followers: 2)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 17)
Environmental Geology     Hybrid Journal   (Followers: 9)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access   (Followers: 3)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (Followers: 16)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 31)
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: 8)
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: 4)
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: 4)
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 7)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 23)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 22)
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: 19)
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: 3)
Geological Journal     Hybrid Journal   (Followers: 13)
Geological Magazine     Hybrid Journal   (Followers: 15)
Geology Today     Hybrid Journal   (Followers: 17)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 2)
Geomatics, Natural Hazards and Risk     Hybrid Journal   (Followers: 6)
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 22)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 29)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Geophysics     Full-text available via subscription   (Followers: 17)
GeoResJ     Hybrid Journal  
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards     Hybrid Journal   (Followers: 7)
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  
Geotectonic Research     Full-text available via subscription   (Followers: 4)
Geotectonics     Hybrid Journal   (Followers: 6)
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: 8)
Gondwana Research     Hybrid Journal   (Followers: 6)
Grassland Science     Hybrid Journal   (Followers: 1)
Ground Water     Hybrid Journal   (Followers: 19)
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: 14)
Hydrological Processes     Hybrid Journal   (Followers: 20)
Hydrology and Earth System Sciences     Open Access   (Followers: 20)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 51)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 10)
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: 17)
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: 15)
International Journal of Applied Earth Observation and Geoinformation     Hybrid Journal   (Followers: 14)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 9)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 27)
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: 45)

        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  [2970 journals]
  • Short-term effects on physical properties of lime treated kaolin
    • Abstract: Publication date: Available online 25 June 2016
      Source:Applied Clay Science
      Author(s): E. Vitale, D. Deneele, G. Russo, G. Ouvrard



      PubDate: 2016-06-25T15:00:07Z
       
  • CaAl-layered double hydroxides as active catalysts for the
           transesterification of glycerol to glycerol carbonate
    • Abstract: Publication date: Available online 25 June 2016
      Source:Applied Clay Science
      Author(s): Judith Granados-Reyes, Pilar Salagre, Yolanda Cesteros

      Graphical abstract image

      PubDate: 2016-06-25T15:00:07Z
       
  • Structure and thermal stability of organo-vermiculite
    • Abstract: Publication date: Available online 22 June 2016
      Source:Applied Clay Science
      Author(s): Xiaoli Su, Lingya Ma, Jingming Wei, Runliang Zhu
      In this study, organo-vermiculites (HEVrm) were prepared by modifying expanded vermiculite (EVrm) with different amounts of surfactant (hexadecyltrimethyl ammonium bromide, HDTMAB). The obtained HEVrm were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TG). Instead of a gradual increase of the basal spacing for organo-montmorillonite (OMt) as reported in literatures, a one-stepped increase of the basal spacing was observed for HEVrm. As such, the intercalation of surfactant into the interlayer space of EVrm is not homogeneous. In particular, only part of the interlayer spaces of EVrm were intercalated by surfactants at low HDTMAB concentration; with the increase of surfactant concentration, more and more interlayer spaces were intercalated, reaching a “saturation” state at last. The intercalated surfactant adopted a paraffin-monolayer arrangement with all-trans conformation within the interlayer space. The decomposition temperature of the intercalated surfactant in HEVrm is very similar to that of neat surfactant. The protection of the clay mineral layers for the thermal stability of the intercalated surfactant is not obvious, which is very different from that for OMt. This may be due to the one-stepped increase of the basal spacing in HEVrm with relatively large interlayer height. These findings are of high importance for preparation and application of HEVrm.
      Graphical abstract image

      PubDate: 2016-06-25T15:00:07Z
       
  • Surface modified palygorskite nanofibers and their applications as
           reinforcement phase in cis-polybutadiene rubber nanocomposites
    • Abstract: Publication date: Available online 20 June 2016
      Source:Applied Clay Science
      Author(s): Qingguo Tang, Fei Wang, Xiaodong Liu, Mengran Tang, Zhaogang Zeng, Jinsheng Liang, Xueyang Guan, Juan Wang, Xiaozhan Mu
      In this paper, palygorskite nanofibers modified by liquid rubbers and mercapto silane coupling agent were used as reinforcement phase in the preparation of cis-polybutadiene rubber nanocomposites. The morphologies, structures, and performances, of the nanocomposite rubbers and modified palygorskite nanofibers were characterized. Results show that the liquid rubber coated palygorskite (PALHT) nanofibers reinforced cis-polybutadiene rubber nanocomposites exhibit superior performance, which indicates that liquid rubber coating is essential for optimizing the performance of the modified palygorskite nanofibers. This is attributed to penetration of organic molecules into the interlayer of palygorskite, resulting in formation of a three-dimensional network structure during the vulcanization. It is confirmed by the evidences that the characteristic diffraction peaks of palygorskite become weak and broadened distinctly, with a wide amorphous characteristic curve emerging around 15°–30°. The crosslinking force is much larger than that of the binding energy among the palygorskite crystal layers, which promotes peeling on the crystal face. This work demonstrates a feasible way to obtain an island-structured reinforced composite consisting of 3D network structure units.


      PubDate: 2016-06-25T15:00:07Z
       
  • Characterization of clays from the Corumbataí formation used as raw
           material for ceramic industry in the Santa Gertrudes district, São
           Paulo, Brazil
    • Abstract: Publication date: Available online 18 June 2016
      Source:Applied Clay Science
      Author(s): Andrezza de Almeida Azzi, Marek Osacký, Peter Uhlík, Mária Čaplovičová, Antenor Zanardo, Jana Madejová
      The Ceramic District of Santa Gertrudes (CDSG) is the largest producer of ceramic floor and wall tiles in Brazil. Tile manufacturers in the CDSG use the single raw material, clayey rocks from the Corumbataí formation. Mineralogical, chemical, thermal and microstructural characterization of the clayey rocks from the Corumbataí formation have been performed in order to better understand effect of the studied properties on dry route tilemaking process. The results revealed different compositional features among the studied clayey raw materials. The bulk samples were dominated by clay minerals associated with quartz, feldspars and minor amount of hematite. All samples were complex mixtures where different types of clay minerals (illite, smectite, illite–smectite, kaolinite–smectite, chlorite, sometimes kaolinite) coexist in variable amount. The amount of clay minerals increased with a higher degree of weathering of studied samples. Different technological behavior was expected for studied raw materials due to their heterogeneous nature, in terms of mineral composition and weathering degree. To improve technological behavior of studied materials during tilemaking process an upgrade of the currently used raw materials preparation is recommended (raw materials maturation, more aggressive milling of raw materials, addition of plastic component and homogeneous mixing of plastic and non-plastic components).
      Graphical abstract image

      PubDate: 2016-06-25T15:00:07Z
       
  • Potentials of fabricating porous ceramic bodies from kaolin for catalytic
           substrate applications
    • Abstract: Publication date: Available online 16 June 2016
      Source:Applied Clay Science
      Author(s): David O. Obada, David Dodoo-Arhin, Muhammad Dauda, Fatai O. Anafi, Abdulkarim S. Ahmed, Olusegun A. Ajayi
      In this work, the suitability of using kaolin–styrofoam, sawdust, and high density polyethylene to produce porous ceramic bodies was experimentally investigated. The kaolin samples (raw and beneficiated) were characterized by the XRD, SEM, TGA/DSC and FTIR methods. Batch formulations of the samples including the kaolin and pore formers were formed into green bodies and fired to 1150°C. The porosities of sintered bodies were calculated and gave the following: apparent porosity: 28.63%–67.13% for all the samples investigated. Samples with high density polyethylene (HDPE) pore formers showed minor surface cracks after firing, but exhibited the highest porosity levels while samples with styrofoam and saw dust exhibited uniform surface characteristics with pores, thermal stability and no visible surface cracks. It can be concluded that formulations containing 80% kaolin can be used for the production of ceramics with porosities as high as 67% if the right pore formers are used.


      PubDate: 2016-06-18T15:41:41Z
       
  • Strengthening montmorillonitic and kaolinitic clays using a calcium-based
           non-traditional additive: A micro-level study
    • Abstract: Publication date: Available online 11 June 2016
      Source:Applied Clay Science
      Author(s): Nima Latifi, Christopher L. Meehan, Muhd.Zaimi Abd Majid, Suksun Horpibulsuk
      Chemical stabilization of clays is commonly used to improve unfavorable engineering properties. Though the effects of non-traditional additives on soil improvement have been investigated in recent years, documented research studies on the macro- and micro-level characteristics of problematic clays stabilized by non-traditional additives are fairly limited. The current study examines the time-dependent changes induced in the strength, mineralogy, morphology, molecular and micro-fabric characteristics of montmorillonitic and kaolinitic clays stabilized with a non-traditional calcium-based additive, which is commercially available under the product name SH-85. The physico-chemical bonding mechanisms induced by the stabilization process were studied at a micro-level using various spectroscopic and microscopic techniques, such as X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometry (EDAX), Fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett and Teller (BET) surface area analysis and particle size analysis (PSA) using a laser diffraction approach. Unconfined compressive strength (UCS) tests were also performed on stabilized specimens at various curing times to examine macro-level characteristics. The UCS test results showed that the 6% and 9% additive content were optimal for montmorillonitic and kaolinitic clays, respectively, with the UCS of both stabilized clays improving significantly after 7days of curing. This relatively rapid curing reaction process is very advantageous and cost-effective for geotechnical engineering applications. The micro-level study revealed that the calcium-based additive modified the porous network of the stabilized clays. The pores were filled and particles were bonded by cementitious products, including calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) for the stabilized montmorillonitic and kaolinitic clays, respectively.


      PubDate: 2016-06-16T18:00:57Z
       
  • Adsorption of an active molecule on the surface of halloysite for
           controlled release application: Interaction, orientation, consequences
    • Abstract: Publication date: Available online 11 June 2016
      Source:Applied Clay Science
      Author(s): József Hári, Péter Polyák, Dávid Mester, Matej Mičušík, Mária Omastová, Mihály Kállay, Béla Pukánszky
      The goal of the study was to check the possible use of halloysite (Hal) nanotubes as a controlled release natural antioxidant device with quercetin as the active component. The mineral was thoroughly characterized by various techniques including the determination of particle and tube morphology, specific surface area, pore size and volume, and surface energy. The high surface energy of Hal predicted strong adsorption of active molecules on its surface and consequently difficult release. FTIR spectroscopy confirmed the existence of strong interactions, energetically heterogeneous Hal surface and multilayer coverage at large loadings. FTIR and XRD experiments proved the complete lack of intercalation and showed that below 3.5wt% quercetin loading, most of the molecules are located within the Hal tubes. Molecular modeling indicated the parallel orientation of quercetin molecules with the surface. Critical concentrations derived from various measurements agreed well with each other further confirming that up to about 4.0wt% loading, quercetin is bonded very strongly to the Hal surface. As a consequence, the dissolution of active molecules is very difficult or impossible, especially into apolar media; thus, neither stabilization nor controlled release effect can be expected below that concentration.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Adsorption characteristics of arsenate on colloidal nanosheets of layered
           double hydroxide
    • Abstract: Publication date: Available online 11 June 2016
      Source:Applied Clay Science
      Author(s): Paulmanickam Koilraj, Yu Takaki, Keiko Sasaki
      Nanomaterials have gained much interest in water remediation and pollution control in recent years. However, the toxicity associated with nanoparticles remaining in solution after remediation has high impact on the environment. The present study examined the synthesis and characterization of colloidal Mg2Al-NO3 layered double hydroxide (Mg2Al-UD-LDH) nanosheets and their application as adsorbent toward arsenate immobilization. Colloidal LDH nanosheets featured the absence of nanoparticles release in the environment differently from other nanomaterials. The adsorption studies conducted in batch method, revealed that colloidal Mg2Al-UD-LDH nanosheets (obtained by ultrasonic treatment of Mg2Al-NO3-LDH suspension) achieved a higher arsenate adsorption density of 1.21mmol/g than parent Mg2Al-NO3-LDH (1.16mmol/g) at a solid-to-solution dosage of 0.78g LDH/L. The adsorption mechanism of arsenate onto colloidal Mg2Al-UD-LDH nanosheets proceeded through restacking of the nanosheets, besides ion-exchange onto Mg2Al-NO3-LDH and surface adsorption onto Mg2Al-CO3-LDH. Kinetics of arsenate adsorption onto colloidal Mg2Al-UD-LDH nanosheets was rapid, reaching equilibrium within 5min, whereas equilibrium was reached within 120min in the presence of Mg2Al-NO3-LDH. The colloidal LDH nanosheets stacking effect was restricted at higher LDH/As ratios owing to electrostatic repulsion among the nanosheets, as determined by zeta potential measurements. Semi-pilot scale static model systems for arsenate adsorption were examined to further investigate the adsorption performance of colloidal Mg2Al-UD-LDH nanosheets in natural water systems such as river, pond, or lake. Arsenate adsorption was rapid onto colloidal Mg2Al-UD-LDH nanosheets owing to their high dispersibility; specifically, 100% adsorption efficiency was achieved within 5min. Thus, the high adsorption capacity, dispersibility, and fast kinetics of arsenate removal onto colloidal Mg2Al-UD-LDH nanosheets promising for use as an efficient adsorbent for water remediation.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • A kaolinitic clay from Yantai (China): Improvement of properties and
           microstructure
    • Abstract: Publication date: Available online 16 June 2016
      Source:Applied Clay Science
      Author(s): Xiangming Li, Mingjun Gao
      The properties and microstructure of a kaolinitic clay were improved by sintering at 1085–1095°C with addition of cinder powder and calcium sulfate. Both sintering temperature and the additive content have great effect on the properties and microstructure of the clay. The clay sintered with 15–20wt% additive at 1085–1095°C possesses a high open porosity of 34.2–38.1%, flexural strength of 10.8–14.8MPa, low volume shrinkage of 2.4–6.2%, tailored microstructure and well–connected open pores, which is considered suitable for manufacturing irrigation pitchers and units for water seepage and filtration.


      PubDate: 2016-06-16T18:00:57Z
       
  • Preparation, characterization and application on dye adsorption of a
           well-defined two-dimensional superparamagnetic clay/polyaniline/Fe3O4
           nanocomposite
    • Abstract: Publication date: Available online 13 June 2016
      Source:Applied Clay Science
      Author(s): Bin Mu, Jie Tang, Long Zhang, Aiqin Wang
      Well-defined two-dimensional superparamagnetic clay/polyaniline/Fe3O4 nanocomposites were successfully prepared for dye adsorption based on montmorillonite and vermiculite via a one-pot method combining in-situ intercalation polymerization and coprecipitation technique. The results of XRD revealed that montmorillonite and vermiculite were well intercalated and even completely exfoliated by polyaniline and Fe3O4. Furthermore, the generated Fe3O4 nanoparticles with a diameter of about 10nm and polyaniline were well confined to the surface of clay without the free aggregates. The as-prepared two-dimensional superparamagnetic nanocomposites could be served as a recycled adsorbent for the removal of dyes from aqueous solution by magnetic separation. The adsorption ratio toward 100ppm of Brilliant green, Methylene blue, and Congo red reached 96.2%, 99.6% and 98.1%, respectively. In addition, the adsorption kinetics and the adsorption isotherm well fitted pseudo second-order kinetic model and Langmuir isotherm model, respectively. It suggested that the two-dimensional superparamagnetic nanocomposites exhibited excellent adsorption ratio to cationic dyes as well as anionic dyes.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Suitability of soils and river deposits from Marrakech for the
           manufacturing of earthenware
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Hicham El Boudour El Idrissi, Lahcen Daoudi, Meriam El Ouahabi, Achille Balo Madi, Frédéric Collin, Nathalie Fagel
      This paper investigates the suitability of clayey materials originating from semi-arid soil and river sediments, used by potters in the Agafay region for the manufacture of ceramic products. The clay samples were subjected to particle-size analysis, X-ray diffraction and X-ray fluorescence to investigate their physical, mineralogical and chemical characteristics respectively. The physical behaviour of the intermediate products was studied at the shaping and drying stages of the ceramics manufacturing process through the Atterberg limits and the plot of the Bigot curve respectively. The final product characteristics were determined through porosity tests, flexural and compressive strengths tests. Based on results obtained, the raw materials turn out to be suitable characteristics for the manufacture of earthenware products. The application of the suggested recommendations is worthy for the improvement of the products based on such raw materials.


      PubDate: 2016-06-16T18:00:57Z
       
  • Fe3+ in pottery: Distinction of the use for cooking and production
           parameters
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): G.M. Mangueira, S. Teixeira, F.A. Silva, R.W.A. Franco
      The estimated firing temperature and atmosphere in which a piece of pottery was produced can be identified by comparing the concentration of Fe3+ between the piece of pottery and clay with a similar chemical composition that were subjected to identical thermal treatments. This procedure was applied to modern pottery donated by indigenous people and to a set of archaeological pottery. The modern pottery that was used for cooking for two years exhibited higher Fe3+ concentrations than the clay that was fired at any temperature; thus, the parameters of production were not identified in this pottery. The same procedure can be used to identify the use of a piece of pottery as a pan. Of the set of 14 pieces of archaeological pottery examined in this study, 12 were able to have their production parameters identified, and 2 fragments were identified with Fe3+ concentrations that were higher than that of the fired clay, suggesting that these pieces were used as pans. The results of this study indicate that the concentration of Fe3+ can be used to determine if a piece of pottery was used for cooking; additionally, if a piece of pottery was not used for cooking, then the proposed method can identify the parameters of the piece of pottery's production.
      Graphical abstract image

      PubDate: 2016-06-16T18:00:57Z
       
  • Influence of pore fluid concentration on water retention properties of
           compacted GMZ01 bentonite
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Y. He, W.M. Ye, Y.G. Chen, B. Chen, B. Ye, Yu-Jun Cui
      Due to its low hydraulic conductivity, high swelling capacity and good adsorption properties, the Gaomiaozi (GMZ) bentonite has been proposed as a suitable buffer/backfill material for the construction of artificial barriers in a deep geological repository for the disposal of high-level nuclear waste (HLW) in China. Compacted GMZ01 bentonite with an initial dry density of 1.70g/cm3 was hydrated with distilled water and NaCl solutions. The swelling strain was recorded. After being saturated, suction-controlled drying tests were conducted and corresponding soil water retention curves were obtained. MIP investigations were conducted on the void ratio variation of a specimen before and after experiencing wetting and drying processes. Results show that the swelling strain of compacted GMZ01 bentonite decreases as the concentration of infiltration solution increases. The shrinkage curve of saturated compacted GMZ01 bentonite specimens evolves with controlling suctions and could be divided into three stages including a normal shrinkage stage, a residual shrinkage stage and a zero shrinkage stage. For a given suction, the measured void ratio of a specimen saturated with distilled water is slightly larger than those of specimens saturated with salt solutions after the drying equilibrium is reached. For a given suction, the degree of saturation of a compacted GMZ01 bentonite specimen increases as the salt concentration increases. According to the test results, a modified SWRC equation was proposed to account for the effect of void ratio and salt solutions on drying behaviour. The verified results revealed that the proposed equation can satisfactorily describe the SWRCs of compacted GMZ01 bentonite saturated with different solutions.


      PubDate: 2016-06-16T18:00:57Z
       
  • Properties and pozzolanic reactivity of flash calcined dredging sediments
    • Abstract: Publication date: August 2016
      Source:Applied Clay Science, Volume 129
      Author(s): Ruben Snellings, Özlem Cizer, Liesbeth Horckmans, Paweł T. Durdziński, Philippe Dierckx, Peter Nielsen, Koenraad Van Balen, Lucie Vandewalle
      Dredging of ports, harbours and waterways generates vast amounts of sediments that find few applications and need to be disposed of. In the port of Antwerp, Belgium, each year 450,000t (dry matter) of dredging sediments are mechanically dewatered and stockpiled. This paper investigates flash calcination of the clay-rich dredged sediments as a sustainable solution to develop novel pozzolanic supplementary cementitious materials (SCM) for blended cement.


      PubDate: 2016-06-16T18:00:57Z
       
  • 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
       
  • Editorial Board
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128




      PubDate: 2016-05-13T04:33:24Z
       
  • Functional magnetic nanoparticle/clay mineral nanocomposites: preparation,
           magnetism and versatile applications
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Liang Chen, Chun Hui Zhou, Saverio Fiore, Dong Shen Tong, Hao Zhang, Chun Sheng Li, Sheng Fu Ji, Wei Hua Yu
      Clay minerals and magnetic nanoparticles (MNP) combine to form a class of advanced nanocomposites that would possess exceptional magnetism, stability, adsorption, catalysis, and biocompatibility. This review summarizes and examines recent preparation strategies, properties and applications of magnetic nanoparticle/clay mineral (MNP/CM) nanocomposites. It is organized into five sections. The first section introduces the characteristics of magnetic nanoparticles, clay minerals and the scientific and technological necessity and significance of MNP/CM nanocomposites. The second section is concerned with the preparation of MNP/CM nanocomposites which involve the introduction of MNP into clay minerals via the coprecipitation of MNP and clay minerals, the combination of MNP and pillared clay minerals, the MNP-pillared clay minerals, the combination of surfactants coated MNP and clay minerals, and the intercalation of molecular magnetic compounds into clay minerals. In particular, great strides have been made in the integration of MNP with organo-clay minerals and the resultant nanocomposites can be assembled into the films of MNP/CM nanocomposite. The third focuses on discussion on the distinct magnetism, reactivity and stability of MNP/CM naanocomposites. The superparamagnetic MNP in MNP/CM nanocomposites show a fast response to external magnetic fields and allow MNP/CM nanocomposites to be readily manipulated, well functionalized and easily separated. The fourth section deals with the uses and potentials of MNP/CM nanocomposites in electromagnetic devices, magnetorheological fluids/ferrofluids, magnetic adsorbents, catalysts and biomaterials. The last section presents the view on the existing problems and challenges. Accordingly, it is suggested that future studies need place emphasis on narrowing the size distribution of the MNP/CM nanocomposites, endowing the MNP/CM nanocomposites with more functionalities, uncovering the preparation-modification-structure-magnetism-activity relationships of the MNP/CM nanocomposites, and advancing the practical applications.
      Graphical abstract image

      PubDate: 2016-05-13T04:33:24Z
       
  • Strength development in soft marine clay stabilized by fly ash and calcium
           carbide residue based geopolymer
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Chayakrit Phetchuay, Suksun Horpibulsuk, Arul Arulrajah, Cherdsak Suksiripattanapong, Artit Udomchai
      This research investigates strength development and the carbon footprint of Calcium Carbide Residue (CCR) and Fly Ash (FA) based geopolymer stabilized marine clay. Coode Island Silt (CIS), a soft and highly compressible marine clay present in Melbourne, Australia was investigated for stabilization with the CCR and FA geopolymers. CCR is an industrial by-product obtained from acetylene gas production, high in Ca(OH)2 and was used as a green additive to improve strength of the FA based geopolymer binder. The liquid alkaline activator used was a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH). The influential factors studied for the geopolymerization process were Na2SiO3/NaOH ratio, NaOH concentration, L/FA ratio, initial water content, FA content, CCR content, curing temperature and curing time. The strength of stabilized CIS was found to be strongly dependent upon FA content and NaOH concentration. The optimal ingredient providing the highest strength was found to be dependent on water content. Higher water contents were found to dilute the NaOH concentration, hence the optimal L/FA increases and the optimal Na2SiO3/NaOH decreases as the water content present in the clay increases. The maximum strength of the FA geopolymer (without CCR) stabilized CIS was found at Na2SiO3/NaOH=70:30 ratio and L/FA=1.0 for clay water content at liquid limit (LL). The role of CCR on the strength of FA geopolymer stabilized CIS can be classified into three zones: inactive, active and quasi-inert. The active zone where CCR content is between 7% and 12% is recommended in practice. The 12% CCR addition can improve up to 1.5 times the strength of the FA geopolymer. The carbon footprints of the geopolymer stabilized soils were approximately 22%, 23% and 43% lower than those of cement stabilized soil at the same strengths of 400kPa, 600kPa and 800kPa. The reduction in carbon footprints at high strength indicates the effectiveness of FA geopolymer as an alternative and effective green soil stabilizer to traditional Portland cement.


      PubDate: 2016-05-02T10:19:29Z
       
  • Study of spatial distribution of sepiolite in sepiolite/polyamide6,6
           nanocomposites
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      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: 2016-04-27T08:55:22Z
       
  • Properties of modified crude clay by iron and copper nanoparticles as
           potential hydrogen sulfide adsorption
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Sofian Louhichi, Ali Ghorbel, Hassane Chekir, Noureddine Trabelsi, Sabeur Khemakhem
      The present work aimed at modifying original kaolin with iron and copper chlorides in order to introduce active centers for hydrogen sulfide (H2S) adsorption. In the first modification, interlayer sodium cations were exchanged with two metals. In the second one, iron oxide (FeOx) was introduced to the clay surface. Kaolin and modified kaolin were analyzed using ICP, X-ray diffraction (XRD), Infrared Ray, Fluorescence-X, BET surface area analysis and SEM. The modified clay samples were tested as hydrogen sulfide adsorbents. Iron-doped and copper-doped samples showed a significant improvement in the capacity for H2S removal, despite a noticeable decrease in microporosity compared to the initial pillared clay. The smallest capacity was obtained for the clay modified with FeOx. Variations in adsorption capacity are likely due to differences in the chemistry of metals species, degree of their dispersion on the surface, and accessibility of small pores for H2S molecule. Results suggest that on the surface of metal-modified clay, hydrogen sulfide reacts with Cu2+ and Fe+3 ions to form sulfides or can be catalytically oxidized to SO2 on iron (hydro) oxides. Subsequent oxidation may lead to sulfate formation.


      PubDate: 2016-04-27T08:55:22Z
       
  • Polyethyleneimine as shale inhibitor in drilling fluid
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Jiang Guancheng, Qi Yourong, An Yuxiu, Huang Xianbin, Ren Yanjun
      In this paper, the inhibition property of polyethyleneimine (PEI) in drilling fluid was studied. The inhibition property was evaluated by linear swell test and roll recovery. The addition of PEI70000 resulted in the lowest swelling height, compared with the others inhibitor. Especially PEI was environmental and friendly. The inhibition mechanism was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Scanning electron microscopy, Zeta potential and Surface area analyzer. The negative charge in the surface of montmorillonite (Mt) was neutralized by the positive charge of PEI. PEI was adsorbed in the surface of Mt and intercalated into the interlayer of Mt, which reduced the hydration repulsion of diffuse electric double layer and leaded to inhibit the hydration of clay. Hydrogen bonding between amino groups in PEI and hydroxyl in the surface of Mt can be formed in the process. The coordination of electrostatic interaction and hydrogen bonding presented water molecules from the interlayer space of Mt, which resulted from the adsorption and intercalation of PEI in the surface and interlayer space of Mt. There was an amount of nitrogen in the backbone and side of PEI, leading to more positive ion than chitosan quaternary ammonium salt (HTCC). The more positive ion resulted in the stronger force between inhibitor and clay due to the protonation of nitrogen in water. The molecular weight of PEI has great influence on inhibition property. The larger molecular weight of PEI performed the better inhibition property except for PEI1800. Indicating the molecular weight of PEI was not the sole factor to control the inhibition property. What was more, the larger molecular weight of PEI leaded to the worse water-solubility.


      PubDate: 2016-04-23T08:37:31Z
       
  • Changes on montmorillonite characteristics through modification
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Rustam Hojiyev, Gafure Ersever, İbrahim Ethem Karaağaçlıoğlu, Fırat Karakaş, Feridun Boylu
      Since montmorillonite (Mt) and organomontmorillonite (O–Mt) are widely used in many different areas from ordinary to high technological applications, there are lots of studies about them in the literature. However, its unique characteristic and different interaction mechanism with additives make those studies continue in order to explain much more detail on it. In this study effect of hexadecyltrimethylammonium bromide (HDTMA) on Mt through modification process has revealed in detail. Adsorption, electrokinetic, rheology and structural aspects of the system were considered in together to explain the interaction mechanism between Na–Mt and HDTMA. Mt suspensions show four different characteristics that are dependent on the HDTMA concentration as dispersion, coagulation-precipitation, coagulation-flotation and re-dispersion. It is found that sedimentation behavior at this regions are in a good agreement with adsorption isotherm, zeta potential, apparent viscosity, X-ray diffraction patterns, swelling index and filtration losses.
      Graphical abstract image

      PubDate: 2016-04-23T08:37:31Z
       
  • Assessment of swelling inhibitive effect of CTAB adsorption on
           montmorillonite in aqueous phase
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Aghil Moslemizadeh, Saeed Khezerloo-ye Aghdam, Khalil Shahbazi, Hadi Khezerloo-ye Aghdam, Fatemeh Alboghobeish
      Physicochemical aspect of wellbore stability during drilling shale formations is linked to the interaction between montmorillonite (Mt) and aqueous phase. This study conducts for the first time a comprehensive study to assess swelling inhibitive effect of cetyltrimethylammonium bromide (CTAB), a celebrated cationic surfactant in petroleum industry, adsorption on Mt in the aqueous phase. Initially, the adsorption behavior of CTAB on Mt below and above the critical micelle concentration (CMC) was assessed by batch equilibrium experiments and then the adsorption data were examined using four famous adsorption equilibrium models. It was found that Mt has a great tendency to adsorb CTAB. Furthermore, the equilibrium data for monomeric and micellar adsorptions suited very well to Langmuir and Linear isotherms, respectively. The swelling inhibitive feature of CTAB was explored through extensive experiments comprising mud making, settlement, filtration, zeta potential, particle size, water adsorption, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). In contrast to deionized water, CTAB aqueous solution exhibited fairly low rheological profile with larger amount of Mt loading (225g/L). The dispersion of pre-hydrated Mt was fully unstable after being exposed to CTAB. Mt lost completely its ability to control fluid loss in aqueous solution of CTAB. The addition of CTAB to Mt dispersion extremely changed the magnitude of zeta potential from negative to positive, specifically before micelles formation. Compared to deionized water, Mt particles gave larger particle sizes in aqueous solution of CTAB, indicating the low degree of particle delamination. The affinity of Mt to water decreased by about 70% after modification via CTAB. Unlike deionized water, modification of Mt in aqueous solution of CTAB led to the larger size of aggregates, according to SEM analysis. TGA demonstrated that modified Mt in aqueous solution of CTAB has 4.68% water content less than that of modified in deionized water. The findings convey the message that CTAB can act as a far superior clay stabilizer at concentration much higher than CMC. Finally, Fourier transform infrared spectroscopy (FT-IR) analysis was carried out to prove the adsorption of CTAB on Mt. It was concluded that the intercalation of CTAB (molecules and CTA +) into the interlayer space of Mt through cation exchange and hydrophobic interaction is probably the main inhibition mechanism.
      Graphical abstract image

      PubDate: 2016-04-23T08:37:31Z
       
  • Preparation and evaluation of quaternary imidazolium-modified
           montmorillonite for disinfection of drinking water
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Phumelele E. Kleyi, Suprakas Sinha Ray, Akebe Luther King Abia, Eunice Ubomba-Jaswa, James Wesley-Smith, Arjun Maity
      Quaternary imidazolium salts with varying alkyl chain lengths (octyl, decyl, dodecyl, tetradecyl, hexadecyl) were synthesized and characterized with nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. Antibacterial screening experiments revealed that the activity decreased with increasing alkyl chain length. Quaternary imidazolium salts with alkyl chains, such as octyl and decyl, were used for the modification of montmorillonite (Mt). The characterization of the modified Mts was performed using XRD, TGA and TEM, and results showed that the surfactants were successfully intercalated in the Mt interlayer space. The selected quaternary imidazolium salt-modified Mts were evaluated for water disinfection using distilled, borehole and river water inoculated with Escherichia coli. Mt modified with surfactants carrying the octyl chains displayed excellent disinfection properties for all three water types. The TEM results showed that the mechanism of inactivation occurred through rupturing of the cell membrane after the E. coli cells came into contact with the modified Mt. In summary, the quaternary imidazolium-modified Mt has great potential to be used for household water disinfection.
      Graphical abstract image

      PubDate: 2016-04-23T08:37:31Z
       
  • Synthesis and characterisation of surfactant enhanced Mg–Al
           hydrotalcite-like compounds as potential 2-chlorophenol scavengers
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Selina Ilunakan Omonmhenle, Ian James Shannon
      Magnesium aluminium hydroxycarbonate hydrotalcites (denoted as MgAl–CO3-HTs) with different Mg/Al molar ratios (4, 3 and 2) were synthesised by the co-precipitation method under low supersaturation conditions, and then treated with sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS) surfactants to produce the nanocomposites — organo-hydrotalcites; dodecylsulfate-hydrotalcites(DS-HTs) and dodecylbenzenesulfonate-hydrotalcites (DBS-HTs) through calcination-reconstruction method. Powder X-ray diffraction (PXRD) and infrared spectroscopy analysis of intercalated samples showed that dodecylsulfate and dodecylbenzenesulfonate guests were successfully intercalated into the parent hydrotalcites, with the PXRD revealing that the species could assume varying configurations within the interlayer gallery regions of this clay based materials, displaying monolayer and bilayer orientations. The uptake ability of the resulting DS-hydrotalcites and DBS-hydrotalcites for the adsorption of phenolic compounds from aqueous solution was investigated. The results showed that, the adsorption process can be described by pseudo-second order kinetics, while the capacity of 2-chlorophenol uptake is dependent on the MgII:AlIII ratio within the interlamellar of the organo-hydrotalcite, the anion present (with DBS modified samples showing higher adsorption capacities) and the pH at which adsorption was carried out.


      PubDate: 2016-04-23T08:37:31Z
       
  • Characterization and traditional ceramic application of clays from the
           Douiret region in South Tunisia
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): S. Mahmoudi, A. Bennour, A. Meguebli, E. Srasra, F. Zargouni
      This study of the Aptian clays of Douiret (south-east of Tunisia) and their use in ceramic industry is original. At first, mineralogical, chemical, physical and thermal analyses of these clays are given. In terms of mineralogy, they can be considered as illitic clays (50–67%). However, other clay minerals, such as kaolinite, I/Sm mixed-layer, quartz, feldspar, dolomite and hematite, are present in small quantities. Next, this study reveals that the average amounts of silica and potassium are 53.9% and 3.3% respectively. The amount of alumina and iron oxide, with an average of 16.8% and 6.3% respectively, is variable. The plasticity test shows a high value (PI=39–56%). The mineralogical changes during the firing process were recorded via the X-ray diffraction of the raw clays and subsequent firing at 300, 700, 800, 900 and 1150°C for 3h with heating rate of 10°C/min. The main transformations were observed at 900°C with the appearance of new crystalline phases especially mullite, anortite and spinel. Technical tests show that the properties fall within the ceramic International Standards (ISO). Finally, ceramic tiles and bricks prepared from these clays have suitable characteristics without defects and can be classified in group BIII according to the European Standard NF EN 159 (1991).


      PubDate: 2016-04-23T08:37:31Z
       
  • Enhanced luminescence of 3,3′-diethyl-2,2′-thiacyanine cations
           adsorbed on saponite particles
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Peter Boháč, Adriana Czímerová, Juraj Bujdák
      Hybrid colloidal dispersions based on cationic dye 3,3′-diethyl-2,2′-thiacyanine iodide (NK88) and saponite (Sap) were prepared and their spectral properties were compared with dye solution. The effect of various NK88/Sap ratios was investigated by absorption and fluorescence spectroscopies. A detailed analysis of absorption spectra based on chemometric methods (principal component analysis and multivariate curve resolution - alternating least squares) revealed a very complex nature of these hybrid systems. Most relevant spectral components were identified as monomeric form, H- and J-aggregates. The rearrangement of initially formed dye species with time led to the increase of the amount of the J-aggregates at the expense of the H-aggregates and the monomers. The larger amounts of the H-aggregates were observed in the specimens with relatively highest dye loadings. NK88 luminescence was significantly enhanced upon the adsorption on Sap particles, but could not be assigned to a single dye form. The participation of different dye forms can explained in terms of strong couplings, such as collective exciton delocalization in dye supramolecular systems formed on Sap surface, and weak coupling between various forms via excitation energy migration and transfer. These interactions led to the emission spectra, whose profiles did not depend on the excitation wavelengths. The colloidal systems based on NK88 and Sap are perspective precursors for hybrid materials with interesting optical and photophysical properties.
      Graphical abstract image

      PubDate: 2016-04-23T08:37:31Z
       
  • Electrospun layered double hydroxide/poly (ε-caprolactone)
           nanocomposite scaffolds for adipogenic differentiation of adipose-derived
           mesenchymal stem cells
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Seyedeh Sara Shafiei, Mahnaz Shavandi, Ghasem Ahangari, Fatemeh Shokrolahi
      Tissue-engineering scaffolds provide biological and structural supports for cell adhesion, proliferation, and differentiation. Fibrous scaffolds properly mimic the native extra cellular matrix (ECM) fibers which play an important role in development and regeneration of tissue and/or organs. One way to achieve fibrous scaffold with tailored properties is incorporating suitable nanomaterials into the polymeric matrix. In this study, the uniform and bead free fibers of poly (ε-caprolactone) (PCL) composited with different layered double hydroxide (LDH) contents (ranging from 0.1wt.% to 10wt.%) were successfully fabricated by electrospinning technique. The LDHs are uniformly dispersed throughout the fibers, as confirmed by Energy dispersive X-ray analysis (EDX). The morphology, degradation, mechanical behavior, porosity, hydrophilicity, and protein adsorption of samples were analyzed. Also, the biological effects of nanocomposites on attachment, viability, proliferation, and adipogenic differentiation of mouse adipose derived stem cells (mADSCs) were evaluated. The results showed that the addition of LDH reduced the average fiber diameter and improved the tensile strength and elongation at break values of the PCL scaffold while hydrophilicity and degradation rate were increased. The LDH-enriched electrospun PCL scaffolds had a remarkable influence on cell adhesion and proliferation. Also, a significant increase in adipogenic differentiation of mADSCs was seen. The PCL-LDH fibrous scaffolds with a high porosity (94%) showed great potential in application for soft tissue engineering.
      Graphical abstract image

      PubDate: 2016-04-19T08:31:01Z
       
  • Preparation and characterization of soy lecithin-modified bentonites
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Danila Merino, Romina Ollier, Matias Lanfranconi, Vera Alvarez
      In this work, a study of exchange of soy lecithin, a natural product, in bentonite was performed in order to synthesize bio-organoclays. The effects of initial amount of modifier and reaction time were studied at a fixed reaction temperature. Organoclays thus obtained were characterized by means of X-ray diffraction (XRD) analysis, X-ray fluorescence spectrometry (XRF), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and water absorption tests. An effective intercalation of soy lecithin between the clay layers was obtained. The ionic exchange reaction was completed at short times whereas variations in the initial amount of modifier produced organoclays with different final properties. At low ratios of soy lecithin to bentonite, a slight increment in basal spacing of organoclays was observed due to intercalation of the organic modifier between the clay layers and a significant diminution on water absorption was achieved. When the organic content increased, the interlayer spacing increased but thermal stability of organoclays decreased compared to the samples with low organic content, whereas the water absorption was not affected. The obtained bio-organoclays are potential environmental-friendly fillers for the development of clay/biopolymer nanocomposites.


      PubDate: 2016-04-15T07:57:49Z
       
  • Strength and micro-structure evolution of compacted soils modified by
           admixtures of cement and metakaolin
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Zilong Wu, Yongfeng Deng, Songyu Liu, Qianwen Liu, Yonggui Chen, Fusheng Zha
      Metakaolin, widely applied in concretes and cement-stabilized soft clays to improve their macro performance, was evaluated for use in compacted soils in highway and backfill engineering. The compactability and strength performance of cement-modified soils with metakaolin were evaluated in the terms of their applicability and effectiveness. The cement-based modified soil with metakaolin was more insensitive to water and more convenient in the field rolling compaction. The strengths, in addition to the unconfined compressive strength and splitting tension strength, were improved significantly. Up to a threshold ratio of metakaolin to cement ranging from 1/3 to 1/2 in this case, the strengths increased gradually, while they unexpectedly decreased thereafter. This phenomenon was different from the previously reported metakaolin applications in concrete and cement-stabilized soft clays, which was probably due to the water content and the ratio of metakaolin to hydrated calcium hydroxides of the cements. Microstructure analysis by X-ray diffraction, scanning electronic microscopy, thermo-gravimetric analysis and mercury intrusion porosimetry, demonstrated that the addition of metakaolin led to a higher quantity of hydration products and a denser micro-porosity distribution.


      PubDate: 2016-04-15T07:57:49Z
       
  • Adsorption behavior of Th(IV) onto illite: Effect of contact time, pH
           value, ionic strength, humic acid and temperature
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Zhang Hongxia, Wang Xiaoyun, Liang Honghong, Tan Tianshe, Wu Wangsuo
      The adsorption experiments of Th(IV) on illite as a function of time, pH, ionic strength, temperature and humic acid (HA) were investigated using batch experiments. The results showed that adsorption of Th(IV) on illite was strongly dependent on contact time, pH, and temperature and independent on humic acid(HA). The Th(IV) adsorption on illite increases with increasing pH (pH<4.5) and temperature, but decreases with increasing ionic strength at pH<4.5. Th(IV) adsorption data were successfully described by the pseudo second-order kinetic model and the intraparticle diffusion equation. Langmuir adsorption isotherm model simulated the adsorption process better than Freundlich model. The thermodynamic parameters of enthalpy, entropy and free energy change were calculated and thermodynamic parameters revealed the spontaneity and exothermic nature of adsorption Th(IV) on illite. Th(IV) of adsorption mechanism on illite is outer-sphere surface complexation and ion exchange with Na+/H+ on illite at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH.


      PubDate: 2016-04-15T07:57:49Z
       
  • A novel bio-based deflocculant for bentonite drilling mud
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Karim Samadzadeh Hafshejani, Aghil Moslemizadeh, Khalil Shahbazi
      The physical and chemical properties of bentonite, a widely utilized drilling fluid additive, in the aqueous phase could potentially change when encountering drilling fluids contaminants. Therefore, prior to encountering an excepted contaminant, it is mandatory that one treat the bentonite mud by an appropriate deflocculant. This study assesses for the first time the performance of Oak seed extract (OSE) as a novel bio-based deflocculant in bentonite drilling mud through some extensive experiments. After being exposed to high temperatures and contaminants, the value of rheological parameters and fluid loss of bentonite mud free from any additives changed remarkably. The OSE kept the stability of bentonite in aqueous phase by restraining the capacity of bentonite to form a flocculated structure, decreasing rheological parameters and fluid loss value. From bentonite inhibition tests, the incapacity of OSE to reduce the magnitude of plastic viscosity was fairly clear. Based on particle size measurements, OSE had a significant impact in reducing particle size of contaminated bentonite muds. According to SEM observations, no remarkable difference was seen between the morphological features of modified bentonite with and without OSE, indicating particle delamination in both cases and no inhibitive property of OSE. The findings verify that OSE can act as a superior deflocculant. The deflocculating performance of OSE was more drastic in the case of cement-contaminated mud owing to its acidic nature (pH=4.58 at 1mass%). Therefore, this study proposes the pre-treat of the bentonite mud with OSE for encountering ultra-high pH condition generated by cement. The deflocculation mechanism is believed to be a neutralization of the positive edges of montmorillonite (Mt, dominant mineral in bentonite) by tannins (dominant constituent in OSE), destroying the ability of Mt layers to link one another. In addition to high performance, environmentally friendliness and cost effectiveness are characteristics which can be considered as other fascinating aspects of OSE.


      PubDate: 2016-04-15T07:57:49Z
       
  • Re(VII) diffusion in bentonite: Effect of organic compounds, pH and
           temperature
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Tao Wu, Zhifen Wang, Qingmei Li, Guoxiang Pan, Jinying Li, Luc R. Van Loon
      In order to understand the diffusion properties of anionic radionuclides (RN) in bentonite in the presence of organic compounds with chelating and reducing properties, the effect of humic acid (HA), citrate, oxalate and formate on Re(VII) diffusion was investigated by a through-diffusion method under different pH (pH7.0 and 10.0) and temperature conditions (10–65°C). When the molar ratio of oxalate to Re(VII) was higher than 1:1, the accumulated mass and flux were observed to decrease drastically as a function of time. It can be explained by photocatalytic impact of Fe(III) on the reduction of Re(VII) to insoluble Re(IV) by oxalate. Thus, the diffusion of Re(VII) was also observed to decrease in the presence of minor citrate, oxalate and formate. Effective diffusion coefficient (De) values decreased from 8.7×10−11 m2/s to (5.1–5.9)×10−11 m2/s. In contrast, HA had no significant impact on Re(VII) diffusion. The De values of 1.54×10−11 and 6.5×10−12 m2/s were obtained at pH7.0 and 10.0, respectively. HA thus neither has an effect on the speciation of Re(VII) nor does it change the charge of the surface. The latter is probably due to the fact that HA preferentially interacts with the aluminol sites of the montmorillonite edges without changing the zeta potential of the surface. The dependence of De of Re(VII) on temperature in the absence and presence of citrate or formate was described by the Arrhenius equation. The activation energy, Ea, was in the range of (20.7–25.1) kJ/mol, demonstrating that Re(VII) diffusion followed a pore water diffusion model.
      Graphical abstract image

      PubDate: 2016-04-15T07:57:49Z
       
  • Characterization and antibacterial activity of chlorhexidine loaded
           silver-kaolinite
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Seow Khai Jou, Nik Ahmad Nizam Nik Malek
      Chlorhexidine acetate-loaded silver-kaolinite (CA-Ag-Kaol) was prepared and characterised, and its application as an antibacterial agent was studied. CA-Ag-Kaol was prepared by the adsorption of chlorhexidine acetate (CA) (0.5mmol/L) on Ag (50% of the Cation Exchange Capacity (CEC) of kaolinite) on kaolinite. Kaolinite (Kaol), silver-kaolinite (Ag-Kaol), CA-modified kaolinite (CA-Kaol) and CA-Ag-Kaol were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning-electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, zeta potential analysis and dispersion behavior measurements. The modification of kaolinite with cationic silver and chlorhexidine ions did not change the structure of kaolinite, and the characterization of the kaolinite samples revealed the successful loading of cationic silver and chlorhexidine ions on the kaolinite. The antibacterial assay of the samples was carried out against Escherichia coli ATCC 11229, Pseudomonas aeruginosa ATCC 15442, Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212 using the disc diffusion technique (DDT) and the minimum inhibition concentration (MIC) technique. Based on the antibacterial assay, CA-Ag-Kaol showed better antibacterial activity than Ag-Kaol and CA-Kaol, and it performed well in both distilled water and a 0.9% saline solution. Gram-positive bacteria were more susceptible to the antibacterial behavior of Ca-Ag-Kaol than Gram-negative bacteria. In conclusion, silver-kaolinite that has been loaded with chlorhexidine acetate can be used as an effective antibacterial agent because of its high antibacterial activity against wide spectrum of bacteria in solutions containing electrolytes (saline solution).
      Graphical abstract image

      PubDate: 2016-04-09T09:45:51Z
       
 
 
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