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  Subjects -> EARTH SCIENCES (Total: 649 journals)
    - EARTH SCIENCES (469 journals)
    - GEOLOGY (70 journals)
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EARTH SCIENCES (469 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted alphabetically
Acta Geochimica     Hybrid Journal   (Followers: 3)
Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Open Access   (Followers: 6)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 21)
Advances In Physics     Hybrid Journal   (Followers: 18)
Aeolian Research     Hybrid Journal   (Followers: 5)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 3)
AMBIO     Hybrid Journal   (Followers: 13)
Anadolu University Journal of Science and Technology     Open Access  
Anales del Instituto de la Patagonia     Open Access   (Followers: 1)
Andean geology     Open Access   (Followers: 13)
Annales Henri Poincaré     Hybrid Journal   (Followers: 3)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access  
Annals of Geophysics     Full-text available via subscription   (Followers: 12)
Annals of GIS     Hybrid Journal   (Followers: 20)
Annals of Glaciology     Full-text available via subscription   (Followers: 3)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 10)
Anthropocene     Hybrid Journal   (Followers: 3)
Anthropocene Review     Hybrid Journal   (Followers: 4)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Geochemistry     Hybrid Journal   (Followers: 11)
Applied Geomatics     Hybrid Journal   (Followers: 3)
Applied Geophysics     Hybrid Journal   (Followers: 7)
Applied Ocean Research     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 2)
Applied Remote Sensing Journal     Open Access   (Followers: 33)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 34)
Arctic Science     Open Access   (Followers: 6)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 10)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 16)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 20)
Asian Journal of Earth Sciences     Open Access   (Followers: 20)
Asian Review of Environmental and Earth Sciences     Open Access   (Followers: 1)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 10)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 12)
Atmospheric and Climate Sciences     Open Access   (Followers: 27)
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: 11)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 21)
Bulletin of Volcanology     Hybrid Journal   (Followers: 17)
Cadernos de Geociências     Open Access  
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 15)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 15)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 4)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 24)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 8)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Contemporary Trends in Geoscience     Open Access   (Followers: 3)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 9)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 3)
Coral Reefs     Hybrid Journal   (Followers: 16)
Cretaceous Research     Hybrid Journal   (Followers: 6)
Cybergeo : European Journal of Geography     Open Access   (Followers: 5)
Depositional Record     Open Access  
Developments in Geotectonics     Full-text available via subscription   (Followers: 3)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 3)
Diatom Research     Hybrid Journal   (Followers: 1)
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 10)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 99)
Earth and Space Science     Open Access   (Followers: 11)
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 4)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 19)
Earth System Dynamics     Open Access   (Followers: 6)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 64)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 10)
Earthquake Spectra     Full-text available via subscription   (Followers: 18)
Ecohydrology     Hybrid Journal   (Followers: 10)
Ecological Questions     Open Access   (Followers: 7)
Electromagnetics     Hybrid Journal   (Followers: 5)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Hybrid Journal   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 22)
Environmental Geology     Hybrid Journal   (Followers: 20)
Environmental Geosciences     Full-text available via subscription   (Followers: 3)
Environmental Geotechnics     Hybrid Journal   (Followers: 4)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (Followers: 17)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 34)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (Followers: 12)
Exploration Geophysics     Hybrid Journal   (Followers: 4)
Facies     Hybrid Journal   (Followers: 9)
Fieldiana Life and Earth Sciences     Full-text available via subscription   (Followers: 1)
Física de la Tierra     Open Access  
Folia Musei rerum naturalium Bohemiae occidentalis. Geologica et Paleobiologica     Open Access  
Folia Quaternaria     Open Access  
Forestry Chronicle     Full-text available via subscription   (Followers: 10)
Frontiers in Earth Science     Open Access   (Followers: 5)
Frontiers in Geotechnical Engineering     Open Access   (Followers: 2)
Frontiers of Earth Science     Hybrid Journal   (Followers: 8)
Fundamental and Applied Limnology / Archiv für Hydrobiologie     Full-text available via subscription   (Followers: 4)
GEM - International Journal on Geomathematics     Hybrid Journal   (Followers: 1)
Geo-Marine Letters     Hybrid Journal   (Followers: 7)
Geoacta     Open Access   (Followers: 4)
Geobiology     Hybrid Journal   (Followers: 8)
Geocarto International     Hybrid Journal   (Followers: 22)
Geochemical Perspectives     Hybrid Journal  
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 7)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 25)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 43)
Geochronometria     Hybrid Journal   (Followers: 3)
Geoderma Regional : The International Journal for Regional Soil Research     Full-text available via subscription   (Followers: 3)
Geodinamica Acta     Hybrid Journal   (Followers: 3)
Geodynamics & Tectonophysics     Open Access   (Followers: 1)
Geoenvironmental Disasters     Open Access   (Followers: 3)
Geofluids     Hybrid Journal   (Followers: 4)
Geoforum     Hybrid Journal   (Followers: 21)
Géographie physique et Quaternaire     Full-text available via subscription   (Followers: 1)
Geography and Natural Resources     Hybrid Journal   (Followers: 5)
Geoheritage     Hybrid Journal   (Followers: 1)
Geoinformatica Polonica : The Journal of Polish Academy of Arts and Sciences     Open Access  
Geoinformatics & Geostatistics     Hybrid Journal   (Followers: 8)
Geological Journal     Hybrid Journal   (Followers: 14)
Geology Today     Hybrid Journal   (Followers: 24)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 3)
Geomatics, Natural Hazards and Risk     Hybrid Journal   (Followers: 9)
Geomechanics for Energy and the Environment     Full-text available via subscription  
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 25)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 31)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Geophysics     Full-text available via subscription   (Followers: 18)
GeoResJ     Hybrid Journal  
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards     Hybrid Journal   (Followers: 8)
Geoscience Canada : Journal of the Geological Association of Canada / Geoscience Canada : journal de l'Association Géologique du Canada     Full-text available via subscription   (Followers: 4)
Geoscience Data Journal     Open Access   (Followers: 2)
Geoscience Frontiers     Open Access   (Followers: 9)
Geoscience Letters     Open Access   (Followers: 1)
Geoscience Records     Open Access  
Geosciences     Open Access   (Followers: 2)
Geosciences Journal     Hybrid Journal   (Followers: 10)
Geoscientific Instrumentation, Methods and Data Systems     Open Access   (Followers: 4)
Geoscientific Model Development     Open Access   (Followers: 2)
Geostandards and Geoanalytical Research     Hybrid Journal   (Followers: 2)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotectonic Research     Full-text available via subscription   (Followers: 4)
Geotectonics     Hybrid Journal   (Followers: 7)
GISAP : Earth and Space Sciences     Open Access   (Followers: 2)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 4)
Global and Planetary Change     Hybrid Journal   (Followers: 16)
Global Biogeochemical Cycles     Full-text available via subscription   (Followers: 12)
Gondwana Research     Hybrid Journal   (Followers: 6)
Grassland Science     Hybrid Journal   (Followers: 1)
Ground Water     Hybrid Journal   (Followers: 30)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 17)
Groundwater for Sustainable Development     Full-text available via subscription  
GSA Today     Partially Free  
Helgoland Marine Research     Open Access   (Followers: 3)
History of Geo- and Space Sciences     Open Access   (Followers: 4)
Hydrobiologia     Hybrid Journal   (Followers: 18)
Hydrogeology Journal     Hybrid Journal   (Followers: 16)
Hydrological Processes     Hybrid Journal   (Followers: 23)
Hydrology and Earth System Sciences     Open Access   (Followers: 26)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 53)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 11)
Indian Geotechnical Journal     Hybrid Journal   (Followers: 3)
Indonesian Journal on Geoscience     Open Access   (Followers: 2)
Interdisciplinary Environmental Review     Hybrid Journal   (Followers: 3)
International Geology Review     Hybrid Journal   (Followers: 12)
International Journal of Advanced Geosciences     Open Access  
International Journal of Advanced Remote Sensing and GIS     Open Access   (Followers: 33)
International Journal of Advancement in Earth and Enviromental Sciences     Open Access   (Followers: 3)
International Journal of Advancement in Remote Sensing, GIS, and Geography     Open Access   (Followers: 27)
International Journal of Applied Earth Observation and Geoinformation     Hybrid Journal   (Followers: 35)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 11)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 30)
International Journal of Earthquake and Impact Engineering     Hybrid Journal   (Followers: 1)

        1 2 3 | Last

Journal Cover Applied Clay Science
  [SJR: 0.826]   [H-I: 83]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [3040 journals]
  • Basic activation of lower Eocene clay from Meknassy-Mezzouna basin
           (centerwestern Tunisia), synthesis of zeolite and clarification of soybean
           oils
    • Authors: Mohamed Mosbahi; Ali Tlili; Mahmoud Khlifi; Fakher Jamoussi
      Pages: 1 - 11
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Mohamed Mosbahi, Ali Tlili, Mahmoud Khlifi, Fakher Jamoussi
      The present work is interested particularly in a basic activation of smectitic clay by solid Na2CO3. The clay samples, belonging to Ypresian Chouabine formation, are taken from the lithological section made in the Oued Errizgui (Jebel Meheri El Jebbes) in the Meknassy-Mezzouna basin. Chemical characterization and mineralogical study shows that studied clays are mostly smectitic and associated with a small amount of sepiolite and palygorskite. The accessory minerals correspond to quartz and dolomite. Moreover, relatively high specific surface (50.47m2/g) encourages the activation of these clays by Na2CO3. Thus, the optimal activation conditions were obtained for 5% Na2CO3 at 75°C during 1h. Under these conditions, the specific surface of smectitic clays increases to 58.63m2/g. The basic activation can cause dissolution of dolomites, crystal grow of zeolites, recrystallization of smectite and Na=Ca ionic exchange between Ca-smectite and basic solution. The activated smectitic clays provide better results compared to those given by the Tonsil product used for the clarification of neutral soybean oils by the refinery of SATHOP and SOZITEX companies. In fact, the bleaching power of the activated clay is much better (71.48%) than that of the Tonsil (56.12%). This is corroborated by the visual examination of the clarified oils.

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.011
      Issue No: Vol. 138 (2017)
       
  • Preparation and performance of amine-tartaric salt as potential clay
           swelling inhibitor
    • Authors: Gang Chen; Jiao Yan; Li Lili; Jie Zhang; Xuefan Gu; Hua Song
      Pages: 12 - 16
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Gang Chen, Jiao Yan, Li Lili, Jie Zhang, Xuefan Gu, Hua Song
      A series of small molecular clay swelling inhibitor was prepared with tartaric acid and amines, presented as amine-tartaric salts (ATS). The inhibitor was screened based on the linear expansion rate of bentonite. The results show that the inhibitor prepared with tartaric acid and triethylenetetramine with the mole ratio of 1:1 (named as ATS-4) is the best inhibitor of the hydration expansion and dispersion of bentonite. The inhibitive properties of ATS-4 were evaluated by various methods, including clay linear swelling tests, anti-swelling tests, mud ball immersing tests, mud-making inhibition experiments and particle distribution measurements etc. The results show that ATS-4 has superior performance to inhibit the hydration swelling and dispersion of clays by controlling the particle size of clay. On the other hand, the bentonite linear expansion rate in 0.5% ATS-4 aqueous solution is much lower than that of others, and the hydration expansion degree of the mud ball in ATS-4 aqueous solution is appreciably weaker than the control test, and it is compatible with the conventional additives in water-based drilling fluids. Then, the inhibition mechanism of the amine-tartaric salt was well discussed based on thermogravimetric analysis (TGA), scanning electron microscope (SEM), X-ray diffraction analysis (XRD), single crystal X-ray diffraction and ion exchange tests.

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.039
      Issue No: Vol. 138 (2017)
       
  • In situ ion induced gelation of colloidal dispersion of Laponite: Relating
           microscopic interactions to macroscopic behavior
    • Authors: Rashmi P. Mohanty; Khushboo Suman; Yogesh M. Joshi
      Pages: 17 - 24
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Rashmi P. Mohanty, Khushboo Suman, Yogesh M. Joshi
      Aqueous dispersion of Laponite, when exposed to CO2 environment leads to in situ inducement of magnesium and lithium ions, which is, however absent when dispersion is exposed to air. Consequently, in the rheological experiments, Laponite dispersion preserved under CO2 shows more spectacular enhancement in the elastic and viscous moduli as a function of time compared to that exposed to air. By measuring concentration of all the ions present in a dispersion as well as change in pH, the evolving inter-particle interactions among the Laponite particles is estimated. DLVO analysis of a limiting case is performed, wherein two particles approach each other in a parallel fashion – a situation with maximum repulsive interactions. Interestingly it is observed that DLVO analysis explains the qualitative details of an evolution of elastic and viscous moduli remarkably well thereby successfully relating the macroscopic phenomena to the microscopic interactions.
      Graphical abstract image

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.036
      Issue No: Vol. 138 (2017)
       
  • Highly luminescent hybrid materials based on smectites with polyethylene
           glycol modified with rhodamine fluorophore
    • Authors: Samuel Sas; Martin Danko; Valéria Bizovská; Kamil Lang; Juraj Bujdák
      Pages: 25 - 33
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Samuel Sas, Martin Danko, Valéria Bizovská, Kamil Lang, Juraj Bujdák
      Highly luminescent anisotropic materials are promising for light harvesting systems, sensors, solid lasers and optical devices. To achieve this, polyethylene glycol (PEG) was derivatized with a reactive rhodamine B (RhB) fluorophore to produce a luminescent, water-soluble and positively-charged polymer (RhPEG) that can be intercalated between layers of smectites. An optimal degree of polymer derivatization was applied to avoid fluorescence quenching. The optical properties of RhPEG were similar to those of the RhB precursor. Colloids were prepared using RhPEG and the montmorillonite Kunipia (Mt) and the synthetic saponite Sumecton (Sap), with polymer/smectite mass ratios of 0.05–0.25, and were cast into thin solid films by a vacuum filtration deposition technique. The luminescent hybrid films exhibited a similar structure to those obtained by the intercalation of non-modified PEG. Optical properties depended considerably on the smectite type. The hybrid films made of Sap, the smectite with low charge density, negligibly induced the molecular aggregation of RhPEG and had high fluorescence quantum yields, similar to dilute solutions of RhB or RhPEG. On the other hand, the results of spectroscopic methods indicated molecular aggregation of RhPEG when intercalated between Mt layers leading to considerable fluorescence quenching, making this material unsuitable for the fabrication of photoactive optical films.
      Graphical abstract image

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.034
      Issue No: Vol. 138 (2017)
       
  • Beneficiation and influencing factors of coal-series kaolin for the
           reduction of COD
    • Authors: Teng Huang; Shaomin Lei; Yuanyuan Liu; Mengjiao Ji; Yanming Fan
      Pages: 34 - 39
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Teng Huang, Shaomin Lei, Yuanyuan Liu, Mengjiao Ji, Yanming Fan
      Coal-series kaolin is the product of seam deposition in coal-accumulating basin. With the high content of reducing substances such as pyrite and fossil, the COD (chemical oxygen demand) can range from 5000 to 30,000μg/g in coal-series kaolin, which is a serious disadvantage for the clarification of glass industry. Through reverse flotation, the COD has effectively enriched in flotation froth products, while the COD in flotation concentrate is 3533μg/g, and can be reduced to 290μg/g at 450°C, which is only <2% of the raw ore. The oxidizing roasting of flotation concentrate has great significance for the decreasing of COD in the coal-series kaolin. Pyrite would also have great influence on the reduction of COD, with a high degree of oxidation, COD decreases more significantly, and the content of pyrite shows linear correlation with COD, which would provide an approximate method to evaluate the COD in coal-series kaolin.

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.032
      Issue No: Vol. 138 (2017)
       
  • Development, characterization and cytotoxicity of novel silane-modified
           clay minerals and nanocomposites intended for food packaging
    • Authors: Sara Maisanaba; Natalia Ortuño; María Jordá-Beneyto; Susana Aucejo; Ángeles Jos
      Pages: 40 - 47
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Sara Maisanaba, Natalia Ortuño, María Jordá-Beneyto, Susana Aucejo, Ángeles Jos
      Layered silicates are largely used to develop polymer nanocomposites with improved physical properties compared to the original polymeric matrix. In this work, the silylation of sodium montmorillonite (Mt) was performed in distilled water using 3-aminopropyltriethoxysilane and vinyltrimethoxysilane, obtaining two different silane modified clay minerals named Clay3 and Clay4, respectively. Clay3 indicated a better profile with a notable increase in the interlayer space compared to Mt. For this reason, Clay3 was selected to scale up its production and to be incorporated in polypropylene (PP) matrix. The PP-Clay3 nanocomposite showed an enhancement in elasticity, a reduction of 15% in the oxygen transmission rate and important antimicrobial effects in comparison to pristine PP. Also, for the first time, cytotoxic effects in human cell lines exposed to Clay3 and Clay4 were evaluated. No cytotoxic damage was observed after Clay3 exposure but an important decrease in cell viability was produced by Clay4. The PP-Clay3 nanocomposite is an attractive alternative for the food packaging industry although further work is needed to get better results in the case of Clay4. Moreover, individual case by case evaluation of clay minerals under different conditions is required in order to obtain the most complete toxicity information.
      Graphical abstract image

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.042
      Issue No: Vol. 138 (2017)
       
  • The corrosion of kaolinite by iron minerals and the effects on
           geopolymerization
    • Authors: R.C. Kaze; L.M. Beleuk à Moungam; M.L. Fonkwe Djouka; A. Nana; E. Kamseu; U.F. Chinje Melo; C. Leonelli
      Pages: 48 - 62
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): R.C. Kaze, L.M. Beleuk à Moungam, M.L. Fonkwe Djouka, A. Nana, E. Kamseu, U.F. Chinje Melo, C. Leonelli
      Iron-rich aluminosilicates with disordered structure (laterites) due to the corrosion of kaolinite by iron minerals were investigated as solid precursors for geopolymerization. The particle size distribution, B.E.T surface area, thermal activation, and chemical and mineralogical compositions were used to evaluate the reactivity of iron-rich laterites (35wt.% of Fe2O3-FeO). The raw materials in the temperature range between 25 and 500°C showed geopolymerization behaviour similar to that of metakaolin. At temperatures higher than 500°C, the coarsening of particles and the decrease of B.E.T surface area correspond to an initial sintering of laterites explaining the poor polycondensation/geopolymerization and the decrease of strength of the final products. The increase of the temperature of calcination of raw laterites between 25 and 500°C corresponds to a reduction of the setting time of geopolymer products. However, this variation of temperature did not significantly affect the flexural strength that remained between ~4 and ~6MPa, confirming the possibility to produce sustainable matrices, with more energy saving, using highly corroded laterites.
      Graphical abstract image

      PubDate: 2017-01-07T01:26:29Z
      DOI: 10.1016/j.clay.2016.12.040
      Issue No: Vol. 138 (2017)
       
  • Thermal stability of tetrabutyl-phosphonium and -ammonium exchanged
           montmorillonite: Influence of acid treatment
    • Authors: Helena Pálková; Małgorzata Zimowska; Ľuboš Jankovič; Bogdan Sulikowski; Ewa M. Serwicka; Jana Madejová
      Pages: 63 - 73
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Helena Pálková, Małgorzata Zimowska, Ľuboš Jankovič, Bogdan Sulikowski, Ewa M. Serwicka, Jana Madejová
      Thermal stability of acid-treated organo-montmorillonites was investigated by thermogravimetric analysis (TA) coupled with infrared (IR) spectroscopic analysis of evolved gasses, and by in-situ measurement of near-IR (NIR) spectra of solid samples. The organoclays prepared from Na-form of SAz-1 montmorillonite (Na-S) and tetrabutylphosphonium (Bu4P+) and tetrabutylammonium (Bu4N+) salts were treated with 6M HCl at 80°C for 2–12h. Elemental analysis revealed higher resistance of Bu4P-S and Bu4N-S to decomposition compared to Na-S, leaving 44 and 52% of the octahedral Mg and/or Al in the solid reaction products after 12h treatment. Bu4N-S decomposed in slightly lower extent than Bu4P-S, pointing thus to the influence of the type of cation headgroup on its stability in HCl. The TG/DTG profiles of both samples showed pronounced mass loss due to decomposition of organic cations within temperature 200–800°C. While Bu4N-S showed onset temperature of near 200°C, significantly higher temperatures, above 300°C, was found for Bu4P-S. The intensities of the absorption bands related to CH vibrations of aliphatic hydrocarbons in the IR spectra reached maxima at 277°C and 446°C for Bu4N-S and Bu4P-S, respectively. The mass loss attributed to the organic cation decomposition for acid-treated samples dropped down below 50% of its initial value due to the leaching of organic phase. Moreover, the onset temperature of organic phase release was shifted to higher temperature indicating that only more strongly held cations remained in the samples. NIR spectra showed that the intensity decrease of the first 2νCH overtones band due to organic cation release began at lower temperature for Bu4N-S (above 380°C) than for Bu4P-S (above 500°C).
      Graphical abstract image

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.043
      Issue No: Vol. 138 (2017)
       
  • Effects of formation and penetration properties of biodegradable
           montmorillonite/chitosan nanocomposite film on the barrier of package
           paper
    • Authors: Shanhui Wang; Yi Jing
      Pages: 74 - 80
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Shanhui Wang, Yi Jing
      The conventional package paper was coated with biodegradable montmorillonite/chitosan nanocomposite, in order to extend the application scope of paper. The effect of coating weight, montmorillonite dispersion rate, montmorillonite and dispersant content on the surface and penetration properties of montmorillonite/chitosan nanocomposite coated paper were being investigated. The surface properties of the coated paper were observed by using scanning electron microscope (SEM) and atomic force microscope (AFM). The water permeation and water vapor barrier properties were confirmed through penetration dynamics analyzer (PDA) and water vapor permeability tester (WVP), respectively. The results indicated that montmorillonite/chitosan nanocomposite had a poorer formation than pure chitosan, but it had better water vapor barrier properties. The paper coated with lower content of montmorillonite, or with higher dispersion speed and dispersant content, had better smoothness and elongation. Additionally, the coated paper had excellent barrier properties under the conditions of high montmorillonite and dispersant content, dispersion rate and coating weight.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.037
      Issue No: Vol. 138 (2017)
       
  • Effects of microbial cells and their associated extracellular polymeric
           substances on the bio-flocculation of kaolin and quartz
    • Authors: Ramin Akbari Ghashoghchi; Mohammad Raouf Hosseini; Ali Ahmadi
      Pages: 81 - 88
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Ramin Akbari Ghashoghchi, Mohammad Raouf Hosseini, Ali Ahmadi
      Microbes can function as bio-surfactants to selectively flocculate or disperse particles, and separate minerals. In the present study, Bacillus licheniformis cells and metabolite were used to change the settling behavior of kaolin and quartz. Moreover, to perform a more detailed study on the metabolite, settling effect of its protein and polysaccharide constituents were also investigated separately. In the best condition, about 40% improvement in kaolin settling was observed using bacterial cells and metabolite at pH=7 and 3, respectively. Also, enhancement in quartz sedimentation using the same bio-flocculants was >50% at pH=1–3. In addition, polysaccharide was more effective in kaolin flocculation, while protein was more influential in quartz agglomeration. Results of adsorption tests suggested that all of the bio-surfactants were more inclined to be adsorbed on quartz, and generally, increasing the pH value decreased the reagent adsorption and mineral flocculation. Moreover, although reducing the mineral concentration from 50 to 20g/l improved the settling of both kaolin and quartz, the highest difference (50%) in their sedimentation occurred at the higher mineral concentration. Finally, according to the statistics, clay concentration was the most influential parameter on kaolin, and the dispersion pH was the most effective variable in quartz bio-flocculation.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2017.01.002
      Issue No: Vol. 138 (2017)
       
  • Curing studies and mechanical properties of glass fiber reinforced
           composites based on silanized clay minerals
    • Authors: Bikramjit Sharma; Rahul Chhibber; Rajeev Mehta
      Pages: 89 - 99
      Abstract: Publication date: 15 March 2017
      Source:Applied Clay Science, Volume 138
      Author(s): Bikramjit Sharma, Rahul Chhibber, Rajeev Mehta
      A commercial organically modified montmorillonite Cloisite® 15A was modified via a new silanization route by two different silane coupling agents: 3-Aminopropyltriethoxysilane and 3-Glycidyloxypropyltrimethoxysilane. This method enables the use of very high concentration of silanes for functionalization of clay minerals. The ratio of weight of silane coupling agent to that of weight of clay mineral (X) was varied from 0.1 to 6. Small angle X- ray scattering and thermogravimetric analysis were carried out on silane modified clay minerals to quantify the grafting of silanes as a function of ratio of weight of silane agent to that of clay mineral. Fiber reinforced epoxy nanocomposites containing silylated clay minerals were manufactured using vacuum assisted resin infusion molding method. Also, curing studies were carried out on fiber reinforced epoxy nanocomposites containing Cloisite® 15A at different cure temperatures, e.g. 70°C, 80°C, 85°C, 95°C and for two different curing time periods, e.g. 7h and 10h. Significant improvements in mechanical properties of fiber reinforced nanocomposites were obtained with incorporation of clay minerals silanized using high concentration of silanes in solvent and chosen curing schedule. The tensile modulus, tensile strength, flexural modulus and bending strength increased by 30%, 37%, 139% and 146% respectively, in nanocomposites containing clay mineral modified using 4X aminopropyltriethoxysilane. An attempt has been made to correlate the results with the morphology of nanocomposites by transmission electron microscopy and that of fractured surfaces by scanning electron microscopy.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.038
      Issue No: Vol. 138 (2017)
       
  • Effect of ball milling process on the structure of local clay and its
           adsorption performance for Ni(II) removal
    • Authors: Shahrzad Maleki; Ayoub Karimi-Jashni
      Pages: 213 - 224
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Shahrzad Maleki, Ayoub Karimi-Jashni
      The effect of ball milling process on the properties of the natural local clay including structural changes and adsorption capacity for the removal of Ni(II) ions from aqueous solutions, was investigated. The local clay was ground at varying times from 5 to 20h with a 10:1 or 20:1 weight ratio of the balls to powder, which produced six different ball milled clays (BM-Clay1 to BM-Clay6). Ground clays were then characterized by particle size measurement, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy analysis, and adsorption experiments. These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity, and adsorption characteristics. According to XRD analysis, the degree of amorphization increased with grinding time, and the present crystalline phase in the final ball milled clay was found to be quartz, which was the associated phase in the original unmilled clay mineral. FTIR studies indicated the destruction of the layers of the montmorillonite upon milling. Adsorption experiments revealed that under similar conditions, BM-Clay2 has the most adsorption capacity for Ni(II) ions. Adsorption characteristics of this ball milled clay for the removal of Ni(II) ions from aqueous solutions was examined in batch adsorption studies under different conditions of contact time, solution pH, adsorbent dose, and initial Ni(II) concentration. The Langmuir maximum adsorption capacity was found to be 29.76mg/g at pH7 and 25°C. The adsorption kinetics data showed better agreement with the pseudo second-order kinetic model. Also, both surface adsorption and intra-particle diffusion contributed to the rate limiting steps in the adsorption of Ni(II) on clay adsorbent. In conclusion, grinding of local clay using ball milling process can significantly increase the adsorption capacity of the clay for Ni(II) removal from aqueous solutions.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.008
      Issue No: Vol. 137 (2017)
       
  • Pairing micropollutants and clay-composite sorbents for efficient water
           treatment: Filtration and modeling at a pilot scale
    • Authors: Filomena Lelario; Ido Gardi; Yael Mishael; Noam Dolev; Tomas Undabeytia; Shlomo Nir; Laura Scrano; Sabino A. Bufo
      Pages: 225 - 232
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Filomena Lelario, Ido Gardi, Yael Mishael, Noam Dolev, Tomas Undabeytia, Shlomo Nir, Laura Scrano, Sabino A. Bufo
      Organically modified clay minerals have been widely developed, tested and employed as sorbents for organic pollutants. However, the process of pollutant-composite pairing is not commonly addressed, which would be valuable for efficient pollutant filtration by such sorbents. This study presents an approach for achieving efficient pollutant removal by large-scale composite filters, based on pairing chemically compatible pollutants and composites and by employing a predictive filtration model. The removal of three organic pollutants, simazine, sulfentrazone and diclofenac by lab-scale filtration columns containing one of three sorbents, a polymer-, micelle- or liposome-clay composite, was measured. Understanding the factors governing pollutant-organic modifier interactions enabled to pair an efficient sorbent to each pollutant. The high removal (80%) of simazine by the polymer composite, was attributed to hydrogen bonds and π-π interactions, compared to less than 20% removal by the surfactant composites. The removal of the anionic diclofenac (pKa=4.1) was mainly governed by electrostatic attraction, explaining its high removal by the most positively charge sorbent, the liposome composite. Sulfentrazone (pKa=6.5) removal was mostly affected by micellar solubilization and upon its removal, the zeta potential of the micelle-composite was not reduced as obtained for diclofenac removal. The filtration of the successful pairs was modelled to determine sorbent capacity and adsorption and desorption rate constants. The pilot filtration experiments were well described by the model and demonstrated efficient removal of paired pollutants and sorbents. Model simulations predicted promising treatment at environmental pollutant concentrations in the μgL−1 range. This pairing approach along with model calculations can be a strong and valid tool for efficient pollutant-sorbent filtration.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.029
      Issue No: Vol. 137 (2017)
       
  • Extended and local structural characterization of a natural and 800°C
           fired Na-montmorillonite–Patagonian bentonite by XRD and Al/Si XANES
    • Authors: L. Andrini; R. Moreira Toja; M.R. Gauna; M.S. Conconi; F.G. Requejo; N.M. Rendtorff
      Pages: 233 - 240
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): L. Andrini, R. Moreira Toja, M.R. Gauna, M.S. Conconi, F.G. Requejo, N.M. Rendtorff
      A structural characterization of a Patagonian bentonite and its corresponding heating product (800°C) was carried out. The nature of aluminum and silicon atoms was investigated using Al and Si K-XANES spectroscopy and compared with other well-known Al and/or Si containing materials. The studied material comes from Lago Pellegrini area-Rio Negro Province, Argentina. The main crystalline phase was confirmed to be a Na-montmorillonite. The thermal behavior was studied by DTA-TG-DTG and XRD. A Rietveld based quantification was performed as complementary study. About 90% Na-montmorillonite (clay mineral of smectite Group) content was confirmed and different impurities (quartz, gypsum and feldspars) were also quantified. The smectitic interlayer thermal displacement was determined between 15.49 and 9.81Å. The XANES results allowed obtaining the AlIV/AlVI ratio and the local symmetry and distortions at Si and Al-sites. The tetra-coordination of silicon and the aluminum tetra and hexa-coordinated was found in both materials. The expected high AlIV/AlVI ratio was confirmed and pondered for the thermally treated bentonite.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.030
      Issue No: Vol. 137 (2017)
       
  • Methoxy-grafted kaolinite preparation by intercalation of methanol:
           Mechanism of its structural variability
    • Authors: Xiaoguang Li; Xianjian Cui; Sen Wang; Ding Wang; Kuo Li; Qinfu Liu; Sridhar Komarneni
      Pages: 241 - 248
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Xiaoguang Li, Xianjian Cui, Sen Wang, Ding Wang, Kuo Li, Qinfu Liu, Sridhar Komarneni
      Methoxy-grafted kaolinite is an excellent organic-inorganic compound, which serves as a precursor to prepare new organic or inorganic kaolinite hybrid materials. Direct intercalation of kaolinite with dimethyl sulfoxide (DMSO), N-methylformamide (NMF) and urea (U) was achieved. All of the above intercalated kaolinites could be grafted by methoxy groups by reacting with methanol. The pre-intercalated molecules of DMSO, NMF and U blocked the grafting action at first but facilitated it at a later stage. Here, the mechanism of the structural collapse of methoxy-grafted kaolinite was proposed. Spontaneous deintercalation of small molecules such as water, ethanol, isopropanol and others was observed. Water and methanol molecules played an important role in the grafting action and also affected the structure of methoxy-grafted kaolinite. The d(001) of methoxy-grafted kaolinite was found to be in the range of 0.99–1.11nm in wet state but constant at 0.86nm for dry state. 13C CP/MAS NMR analysis confirmed that inner-surface hydroxyls were replaced by methoxy groups from methanol as detected by a 13C MASNMR resonance at 51ppm assigned to methoxy groups. 13C MASNMR spectra of intercalated kaolinites confirmed that the pre-intercalated molecules were not displaced completely even though it cannot be detected by XRD. The hygroscopicity of the pre-intercalated molecules was found to affect the structure of methoxy-grafted kaolinite.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.031
      Issue No: Vol. 137 (2017)
       
  • Palygorskite supported BiVO4 photocatalyst for tetracycline hydrochloride
           removal
    • Authors: Yingying Shi; Youdong Hu; Lei Zhang; Zewei Yang; Qianghua Zhang; Hao Cui; Xiufang Zhu; Jizhong Wang; Jing Chen; Kanglin Wang
      Pages: 249 - 258
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Yingying Shi, Youdong Hu, Lei Zhang, Zewei Yang, Qianghua Zhang, Hao Cui, Xiufang Zhu, Jizhong Wang, Jing Chen, Kanglin Wang
      A novel bismuth vanadate-palygorskite (BiVO4-Pal) photocatalyst was successfully prepared by a hydrothermal method. The morphology, structure and chemical composition of the composite was characterized. The adsorption capacity and photocatalytic activity under visible light of this composite to tetracycline hydrochloride were also investigated. The results indicated that BiVO4 was successfully loaded on the Pal. Pal, as a low cost support, improved the adsorption capacity of the photocatalyst, thus increased the contact possibility with the active radicals, hence, the degradation activity of BiVO4 was improved. The maximum adsorption capacity of BiVO4-Pal for tetracycline (TC), calculated by the Langmuir model at 20°C, was 33.11mg·g−1. The pseudo-first-order degradation rate constant for BiVO4-Pal composites was approximately 2.1 times higher than that of pure BiVO4, and the photodegradation ratio on the BiVO4-Pal composite was 1.4 times greater than that of pure BiVO4. In addition, the recovery of the BiVO4-Pal composite was carried out after the reaction by calcination at 400°C for 4h. The test showed that the prepared BiVO4-Pal catalyst was stable during the photodegradation of TC. There was no obvious reduction in the degradation rate of TC over the four successive runs and might be useful for practical applications.
      Graphical abstract image

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.035
      Issue No: Vol. 137 (2017)
       
  • Microstructural, physical and mechanical behavior of pastes containing
           clays and alumina waste
    • Authors: Wherllyson P. Gonçalves; Valmir J. Silva; Romualdo R. Menezes; Gelmires A. Neves; Hélio L. Lira; Lisiane N.L. Santana
      Pages: 259 - 265
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Wherllyson P. Gonçalves, Valmir J. Silva, Romualdo R. Menezes, Gelmires A. Neves, Hélio L. Lira, Lisiane N.L. Santana
      The purpose of this study is to analyze the influence of an aluminum oxide-rich precursor added to clays (smectite/kaolinite) during heat treatment on their mineralogical and microstructural changes, emphasizing the presence of mullite phase. Three clays were used. The samples were subjected to physical, chemical, thermal and mineralogical characterizations. Clay compositions containing alumina waste were then formulated and heat-treated at temperatures ranging from 900 to 1400°C, applying a heating rate of 5°C/min and 60min dwell time, after which mineralogical and morphological analyses were performed. The results indicated that mullite can be obtained from clay formulations containing alumina waste, and that the amount of the mullite phase formed is determined by the composition, particle size and applied temperature.

      PubDate: 2017-01-14T07:49:10Z
      DOI: 10.1016/j.clay.2016.12.026
      Issue No: Vol. 137 (2017)
       
  • Dehydroxylation of dioctahedral smectites in water vapor atmosphere
    • Authors: Katja Emmerich; Annett Steudel; Daniela Merz
      Pages: 1 - 5
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Katja Emmerich, Annett Steudel, Daniela Merz
      Due to dehydration and dehydroxylation, it has to be considered, that thermal treatment of large quantities of bentonites in industrial applications may result in a local water vapor atmosphere above the sample. This study investigates the consequences of a local water vapor atmosphere during thermal treatment of bentonites with emphasis on the influence of water vapor on the DHX of dioctahedral smectites with Na+-saturated interlayers. The dehydroxylation behavior of Na+-exchanged montmorillonites in water vapor atmosphere was compared to dehydroxylation in dry synthetic air. Water vapor at atmospheric pressure delays dehydroxylation of montmorillonites by 50°C. The temperature boundary for dehydroxylation of trans-vacant and cis-vacant layers shifts by 50 to 75°C to higher temperatures. Interlayer Na+ acts as flux and partial melting results in hollow spheres and bubbles that delayed dehydroxylation and entrapped water after dehydroxylation, which is suddenly discharged at higher temperatures. The formation of high temperature phases after heating to 1000°C is controlled by the montmorillonite composition.

      PubDate: 2016-12-07T06:52:11Z
      DOI: 10.1016/j.clay.2016.12.003
      Issue No: Vol. 137 (2016)
       
  • Spontaneous oxygen isotope exchange between carbon dioxide and natural
           clays: Refined rate constants referenced to TiO2 (anatase/rutile)
    • Authors: Antonín Knížek; Markéta Zukalová; Ladislav Kavan; Arnošt Zukal; Petr Kubelík; Petr Rojík; Petr Skřehot; Martin Ferus; Svatopluk Civiš
      Pages: 6 - 10
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Antonín Knížek, Markéta Zukalová, Ladislav Kavan, Arnošt Zukal, Petr Kubelík, Petr Rojík, Petr Skřehot, Martin Ferus, Svatopluk Civiš
      In a series of our previously published papers, we reported a broad range of experiments and theoretical studies devoted to the interaction of carbon dioxide with the anatase titania surface. In the current study, we demonstrate oxygen mobility between gaseous carbon dioxide and solid natural clay minerals. This surprising feature implies that such behaviour is typical not only for titania but also for oxides with different chemical composition and structure. The oxygen mobility was demonstrated by the interaction of isotopically labelled carbon dioxide – C18O2 – with the mineral surfaces. In most cases, we observed rapid oxygen exchange between the gas and the mineral. It was therefore discovered that carbon dioxide is more active than was previously thought because it exchanges its oxygen atoms with inorganic surfaces. Moreover, this feature seems to be very significant in natural clays of various compositions. This finding points not only towards high activity of CO2 but also towards high surface reactivity of clays, which are quite common surface minerals on Earth and other planets.

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.11.031
      Issue No: Vol. 137 (2016)
       
  • Yttrium co-precipitation with smectite: A polarized XAS and AsFlFFF study
    • Authors: N. Finck; M. Bouby; K. Dardenne; T. Yokosawa
      Pages: 11 - 21
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): N. Finck, M. Bouby, K. Dardenne, T. Yokosawa
      The Y(III) binding mechanism(s) by coprecipitation with or by adsorption on hectorite, a mineral phase frequently detected in nuclear waste glass alteration experiments, was investigated by polarized EXAFS (P-EXAFS) spectroscopy. The novelty in this study is the use of yttrium to take advantage of the higher angular dependence of the absorption coefficient at the K-edge for P-EXAFS measurements. In the coprecipitation experiment, a brucite precursor was prepared in the presence of Y and subsequently aged to produce hectorite. In the adsorption experiment, Y(III) ions contacted pre-formed hectorite in dispersion. The coprecipitated hectorite and brucite and the hectorite from adsorption experiment were each prepared as textured samples and the Y(III) local environment was probed by P-EXAFS spectroscopy. P-EXAFS analysis indicated that Y(III) is 6-fold coordinated by O atoms in both the coprecipitated brucite and the coprecipitated hectorite, and surrounded by next-nearest Mg/Si shells. The angular dependences of the coordination numbers strongly point to Y(III) substituting for Mg(II) in brucite layers. Upon hectorite crystallization the local environment evolved. Mg and Si shells were detected at distances suggesting an octahedral clay-like environment in the coprecipitated hectorite, and this finding was corroborated by the angular dependence of the coordination numbers. In the adsorption sample, Y(III) forms inner-sphere surface complexes at the platelet edges (i.e., (0 1 0) plane), slightly tilted off the median clay plane. The presence of such surface complexes in the coprecipitation sample could not be evidenced. Finally, the supernatant of the dispersion containing the coprecipitated hectorite was analyzed by the asymmetrical flow field-flow fractionation (AsFlFFF) technique coupled to ICP-MS to obtain information on the smallest sized particles. The AsFlFFF data indicate that nanoparticulate hectorite of various sizes (50–75nm, 125–140nm and >450nm) can be separated from the bulk dispersion and this finding was corroborated by TEM experiments on the same supernatant. Furthermore, AsFlFFF data also indicate that Y(III) behaves like Mg, used as fingerprint of the presence of hectorite. This finding suggests random substitution for octahedral cation within hectorite nanoparticles. Trivalent yttrium was used as proxy for trivalent actinides (An(III)). Consequently, this study supports the incorporation of An(III) into hectorite forming in the nuclear waste glass alteration layer in deep disposal sites, as already suggested in previous studies.

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.11.029
      Issue No: Vol. 137 (2016)
       
  • Experimental investigation of volume change behavior of swelling soil
    • Authors: Thamer H Al-Yaqoub; Jafarali Parol; Dobroslav Znidarcic
      Pages: 22 - 29
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Thamer H Al-Yaqoub, Jafarali Parol, Dobroslav Znidarcic
      The present paper examines the effect of rate of wetting, type of wetting, surcharge pressure and lateral confinement on the swelling deformation of expansive soil using laboratory experiments. The experimental program consisted of two main parts. In Part I, the deformation under free swelling is measured, where the specimens are subjected to different rate and type of wetting. In Part II, series of constant volume oedometer test (CVOT), one-dimensional swelling test (1DST) and submergence tests are conducted. It is observed that significant swelling occurs when the degree of saturation is more than 80%. When the degree of saturation is lower than 80%, the deformation during swelling is significantly small and this small deformation is attributed to the volumetric expansion associated with suction decrease. It is shown that the swelling rate of expansive soil decreases as the surcharge pressure increases. Experimental results are analysed based on several constitutive relationships such as void ratio - moisture content, void ratio - swelling pressure and moisture content-soil suction. Relationship of parameters such as coefficient of compressibility, coefficient of permeability and hydraulic diffusivity with equilibrium swelling pressure is examined. It is observed here that coefficient of permeability of swelling soils depend up on the degree of saturation in addition to the void ratio.

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.11.018
      Issue No: Vol. 137 (2016)
       
  • Evaporation of allyl isothiocyanate from clay minerals and organoclays
    • Authors: Giora Rytwo; Shany Ben Moshe
      Pages: 30 - 32
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Giora Rytwo, Shany Ben Moshe
      Allyl isothiocyanate (AITC), the major component in mustard oil, is an organosulfur volatile pungent compound classified as “generally regarded as safe”. Methods to slow its evaporation rate can increase its applicability as a natural and safe preservative in food industry and as a pesticide in agriculture. This study tested evaporation of AITC mixed with mineral oil and combined with clay minerals or smectite based organoclays. Raw smectites and halloysites did not influence the evaporation rate, whereas fibrous clays increased half-life time by 3–4 folds. Organoclays differed on their efficiency. An organoclays based on thiamine (B1 vitamin) adsorbed on montmorillonite exhibited the best behavior, increasing half-life time 10 times. Thus, the combination of mustard oil with such organoclay may offer an efficient and natural character preservative and pesticide.

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.12.007
      Issue No: Vol. 137 (2016)
       
  • Evaluation of some intercalation methods of dimethylsulphoxide onto
           HCl-treated and untreated Egyptian kaolinite
    • Authors: Khaled S. Abou-El-Sherbini; Eman A.M. Elzahany; Mohammad A. Wahba; Sayed A. Drweesh; Nabil S. Youssef
      Pages: 33 - 42
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Khaled S. Abou-El-Sherbini, Eman A.M. Elzahany, Mohammad A. Wahba, Sayed A. Drweesh, Nabil S. Youssef
      Dimethylsulphoxide (DMSO)-kaolinite interlayer complexes are important precursors for the organo-modifications of kaolinite. DMSO intercalation into HCl activated (HK) and untreated (UnK) Egyptian kaolinites via four different techniques; reflux of DMSO/water mixture at 70°C (R1), ball-milling with DMSO followed by reflux at 140°C (R2) as well as room temperature ageing for two months in absence and in presence of water (2m and 2mW) were performed and compared. The complexes were investigated by IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffractometry (XRD), mass spectroscopy (MS), elemental analysis, scanning electron microscopy – energy dispersive x-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM). Fourier transform infra-red (FTIR) spectra showed a blue-shift in OH vibrations of the modified kaolinite due to the hydrogen bonds formed between DMSO molecules and the inner-surface hydroxyls of kaolinite with the order 2mW>2m>R2>R1 of DMSO loading. In addition, XRD, TGA and elemental analysis supported the same conclusion by high degree. HCl-treatment of clay was shown to reduce the intercalation of DMSO probably due to the reduction in its Al percentage. DMSO was suggested to be loaded onto kaolinite mainly via two mechanisms; intercalation and adsorption processes. The 2mW and 2m methods were recommended for higher adsorption and intercalation efficiencies of DMSO onto kaolinite.
      Graphical abstract image

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.12.005
      Issue No: Vol. 137 (2016)
       
  • Sepiolite and palygorskite-underpinned regulation of mRNA expression of
           pro-inflammatory cytokines as determined by a murine inflammation model
    • Authors: Cynthia Paola López-Pacheco; Antonio Nieto-Camacho; Luis Zarate-Reyes; Emilia García-Romero; Mercedes Suárez; Stephan Kaufhold; Eduardo García Zepeda; Javiera Cervini-Silva
      Pages: 43 - 49
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Cynthia Paola López-Pacheco, Antonio Nieto-Camacho, Luis Zarate-Reyes, Emilia García-Romero, Mercedes Suárez, Stephan Kaufhold, Eduardo García Zepeda, Javiera Cervini-Silva
      This paper shows that clay minerals, sepiolite and palygorskite collected from Torrejón El Rubio and Vallecas, Spain, respectively, altered the expression of four, namely, pro-inflammatory cytokines: interleukins IL-1 and IL-6, tumor necrosis factor (TNF-α), and interferon gamma (IFN-γ) as determined using a 12-O-tetradecanoylphorbol-13-acetate model for inflammation. Quantitative RT-PCR analyses after 4 and 24h inflammatory stimuli showed that sepiolite or palygorskite brought about a reduction in mRNA expression. Sepiolite provoked the highest mRNA expression inhibition for all cytokines, except for TNF-α, and primarily after 4h. Conversely, the anti-inflammatory effect for cytokine TNF-α was found to be true in the presence of palygorskite. Most notably, the significant reduction in mRNA expression of IL-1 registered just shortly after exposure pointed to that the anti-inflammatory effect may be important for modulation of the late inflammatory response. These clay minerals caused modifications in the mRNA expression of IL-1 and its receptor in endothelial cells and downstreaming inflammatory cascades resulting in the recruitment of neutrophils. In addition, polymorphonuclear peroxidase activity was severely reduced just after short exposure to either sepiolite or palygorskite. Evidence provided herein agree well with the idea that these clay minerals impaired neutrophils infiltration to inflamed skin, notwithstanding ear edema and deficient cell localization to skin coupled with such impairment may affect the later stages of inflammation.
      Graphical abstract image

      PubDate: 2016-12-14T07:22:29Z
      DOI: 10.1016/j.clay.2016.12.006
      Issue No: Vol. 137 (2016)
       
  • Rheological properties of organo-palygorskite in oil-based drilling fluids
           aged at different temperatures
    • Authors: Guanzheng Zhuang; Hao Wu; Haixu Zhang; Zepeng Zhang; Xiangming Zhang; Libing Liao
      Pages: 50 - 58
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Guanzheng Zhuang, Hao Wu, Haixu Zhang, Zepeng Zhang, Xiangming Zhang, Libing Liao
      Aiming to develop a new excellent rheological additive for use in oil-based drilling fluids, palygorskite (Pal) was organically modified with three cationic surfactants using wet method. The surfactants were octadecyl trimethyl ammonium chloride (C18-A), benzyl dimethyl octadecyl ammonium chloride (C18-B) and dimethyl dioctadecyl ammonium chloride (DC18). The structure and properties of organo-palygorskite (OPal) and its use in oil-based drilling fluids were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), thermal analysis, gel volume and rheological tests. Surfactant-modification did not change the crystal structure of Pal, but changed the aggregation of Pal fibers. Surfactants mainly coated on the surface of Pal. But the details were influenced by the molecular scale of surfactants and the coating level. The scale of polar heads of surfactants being smaller than the channels' scale is expected. Surface modification decreased the particle size of Pal and loosened the arrangement of Pal fibers. The thermal stability of OPal decreased as follows: C18-A-Pal>C18-B-Pal>DC18-Pal, as well as the thermal stability of corresponding oil-based drilling fluids. Particularly, C18-A-Pal fluids could bear heat of 200°C. OPal could increase the viscosity of oil-based drilling fluids well. In addition, the oil-based drilling fluids containing OPal showed excellent thixotropy aged above 150°C. Temperatures below 150°C increased the rheological properties of oil-based drilling fluids while high temperature helped to disperse the OPal particles and fibers. The rheological properties of oil-based drilling fluids containing OPal were influenced by surfactants nature (polar head scale of surfactant cation, Hydrophilic-Lipophilic Balance (HLB) value, molecular conformation), coating level and temperature. The rheological properties of OPal fluids indicated that OPal was very suitable for oil-based drilling fluids.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.015
      Issue No: Vol. 137 (2016)
       
  • Insight into thiabendazole interaction with montmorillonite and
           organically modified montmorillonites
    • Authors: Martina Gamba; Petr Kovář; Miroslav Pospíšil; Rosa M. Torres Sánchez
      Pages: 59 - 68
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Martina Gamba, Petr Kovář, Miroslav Pospíšil, Rosa M. Torres Sánchez
      The interactions of the fungicide, thiabendazole (TBZ) on montmorillonite (Mt) and organoclays synthesized from phosphatidylcholine (DSPC) and octadecyltrimethylammonium bromide (ODTMA) was investigated for water remediation. The affinity of TBZ on the surface of Mt and organoclays was evaluated by powder X-ray diffraction, X-ray photoelectron spectroscopy and the experimental results were also reinforced by molecular modelling in order to explore the surfaces arrangements. TBZ was protonated upon interaction with negative charged Mt and therefore this strong electrostatic interactions prevented it's desorption in water. Repulsive electrostatic interactions between the cationic surfactant ODTMA and the cationic form of TBZ on the outer surface of the ODTMA modified Mt resulted in high desorption values. In the DSPC modified Mt, TBZ was anchored within the surfactant chains and a small amount of interlayer water was released from the interlayer space.
      Graphical abstract image

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.001
      Issue No: Vol. 137 (2016)
       
  • Binary adsorption of silver and copper on Verde-lodo bentonite: Kinetic
           and equilibrium study
    • Authors: E.D. Freitas; A.C.R. Carmo; A.F. Almeida Neto; M.G.A. Vieira
      Pages: 69 - 76
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): E.D. Freitas, A.C.R. Carmo, A.F. Almeida Neto, M.G.A. Vieira
      Removal and recovery of toxic metals from wastewater by adsorption is an efficient alternative, especially when using uncommon adsorbents. In the present work, silver and copper binary adsorption onto Verde-lodo bentonite was evaluated in static systems. Kinetic studies under different initial metal concentrations and molar fractions were performed. Kinetic models were adjusted to experimental data, and the External mass transfer resistance model (EMTR) presented the best fitting. The binary kinetic assays revealed that copper presents higher adsorption capacity than silver. Higher total concentrations presented an influence on the adsorption process due to increasing competition for active sites. Equilibrium studies were carried out and the results confirmed the preferential copper adsorption in binary solution with silver. Copper ions were better adsorbed at higher temperatures and silver ions at lower temperatures. The maximum adsorption capacities were 0.110mmol/g for copper at 60°C and 0.090mmol/g for silver at 20°C. Binary equilibrium models were fitted and the Langmuir-Freundlich model best represented the experimental data. The comparison between Verde-lodo clay characterization, prior and post adsorption, indicated that the process caused no significant changes in the morphology, crystal structure, functional groups and thermal stability of the material.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.016
      Issue No: Vol. 137 (2016)
       
  • Cell growth underpinned by sepiolite
    • Authors: Javiera Cervini-Silva; María Teresa Ramírez-Apan; Stephan Kaufhold; Eduardo Palacios; Virginia Gomez-Vidales; Kristian Ufer; Paz del Angel; Ascención Montoya
      Pages: 77 - 82
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Javiera Cervini-Silva, María Teresa Ramírez-Apan, Stephan Kaufhold, Eduardo Palacios, Virginia Gomez-Vidales, Kristian Ufer, Paz del Angel, Ascención Montoya
      This paper reports the role of clay minerals, sepiolites, on the proliferation behaviour of human cancer cells. It reports as well on the proliferation of U251 (central nervous system, glioblastoma) and SKLU-1 (lung adenocarcinoma) cells by sepiolite bearing different extent of isomorphic substitution (IS), either because of the inclusion of Al3+, Fe3+.2+, or Ti4+ in Si structural sites (IS at the tetrahedral sheet, T) or that of Ni2+ in Mg structural sites (IS at the octahedral sheet, O). Studied sepiolites were originally from Ampandrandara, Madagascar; Cerro del Almodóvar, Spain; Deiva Forest, Italy; Eskidir, Turkey; Peguera, Falcondo Plant, Dominican Republic; Sepetciköyü, Turkey; Shimien, China; and Vallecas, Spain. Furthermore, obtained results for sepiolites were compared against those for clays (bentonites). Diffractograms showed characteristic patterns for sepiolite, with no evidence of significant accumulation of secondary phases. XRF data confirmed the incorporation of Al, Fe and, Ti; and Ni, consistent with IS at T and O. The effect of sepiolite on cellular proliferation was determined using the SRB protocol. All sepiolites induced inhibition or increment on the proliferation response of U251 or SKLU cells, depending on the sepiolite; however no correlation between proliferation against composition or microporosity properties became evident. Most notably, sepiolite from Sepetciköyü, Turkey, owning the highest microporosity (evidenced by surface area σ s ) of the sepiolite series, 343m2 g−1, exerted the highest proliferation response for U251 and SKLU-1 cells, namely, 100% inhibition and 22.8±12.1% increase, respectively. Sepiolites from Ampandrandara, Sepetciköyü, and Deiva Forest, owing very low contents of Al (Al2O3 ≤0.2%) and variable σ s yielded the highest inhibition in U251 cells proliferation, best accounted for by growth was limited by specific-adsorption mechanisms in which structural changes associated to Al-for-Si IS at T favoured the adsorption of metabolic growth components [epidermal growth factor receptor (EGFR)], thereby inhibiting the development of primary glioblastomas. On the other hand, increments (%) in SKLU-1 cells proliferation did not correlate with microporosity (measured σ s values), yet two data clusters were identified, higher and lower data values, i.e., 22.8≤% increment≤39% (σ s =83, 220, or 343m2 g−1) and 6.9≤% increment≤14.2% (96≤ σ s ≤266). The second group was composed by Ampandrandara, Sepetciköyü, and Deiva Forest, generating surface sites that catalyze the overexpression of activin A. So, the growth behaviour for both U251 and SKLU-1 cells was affected by Al at T via Al-for-Si IS if proceeded to a small degree. In all, however, the overall chemical composition lacked to serve as predictor for growth. Structural considerations supported the idea that controlled cell growth by sepiolite was not limited by the retention of small solutes at inner surfaces. Finally, whether variations in microporosity exerted changes in the cell proliferation behaviour was strongly dependent if the phyllosilicate was a clay mineral (sepiolite) or a clay (bentonite).
      Graphical abstract image

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.11.032
      Issue No: Vol. 137 (2016)
       
  • Dispersion and rheological behaviors of laponite in
           2-acrylamido-2-methylpropanesulfonic acid solution
    • Authors: Na Li; Juan Du; Yun Tan; Jing Ling; Xue Yang; Jianjun Ma; Ronglan Wu; Shimei Xu; Yi Zhang
      Pages: 94 - 100
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Na Li, Juan Du, Yun Tan, Jing Ling, Xue Yang, Jianjun Ma, Ronglan Wu, Shimei Xu, Yi Zhang
      Previous studies of Laponite (Lap) in electrolyte solution have revealed a fast aggregation or gelation due to reduced electrostatic repulsion between Lap layers. In this work, the dispersion and stability of Lap in 2-acrylamido-2-methylpropanesulfonic acid (AMPS) solution were explored. Lap in low concentration of AMPS (<2.0wt%) were likely to generate aggregation because the formation of electrostatic bonds. In high concentration of AMPS (≥2.0wt%), Lap layers were gradually damaged due to the leaching out of magnesium ions and more likely converted into amorphous silica. So the mutual attraction force between particles was weakened and the phenomenon of aggregation gradually disappeared. However, aging process may convert a well-dispersed fluid into a gel due to electrostatic interaction between sulfonate groups of AMPS absorbed onto Lap and magnesium ions leached out from Lap when the concentration of AMPS range from 2.0wt% to 5.0wt%. Besides, rheological tests indicated that Lap/AMPS dispersions changed from pseudoplastic fluids to Newton fluids as the concentration of AMPS increased to 6.0wt%. The addition of AMPS could also improve the salt tolerance of Lap dispersion.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.018
      Issue No: Vol. 137 (2016)
       
  • Synthesis and characterization of magnetic halloysite-iron oxide
           nanocomposite and its application for naphthol green B removal
    • Authors: Ramin Riahi-Madvaar; Mohammad Ali Taher; Hamid Fazelirad
      Pages: 101 - 106
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Ramin Riahi-Madvaar, Mohammad Ali Taher, Hamid Fazelirad
      In the present work, a magnetic nanoadsorbent was prepared by incorporating magnetic iron oxide nanoparticles (Fe3O4) on the surface of halloysite nanotubes. The structure and morphology of the synthesized nanocomposite were investigated by using of FT-IR and field emission-scanning electron microscope. This nanoadsorbent was successfully applied for removal of naphthol green B from the aqueous solutions. Kinetic studies show the adsorption of naphthol green B on the surface of adsorbent could be characterized by the pseudo-second order model. Also, investigation of adsorption isotherms showed that the Langmuir model fitted better than the Freundlich model and naphthol green B forms a mono-layer on the surface of nanoadsorbent. Furthermore, spectrophotometric determinations for dye were done at λ=265nm and the results show the linearity in the range of 1.0–50μgmL−1.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.019
      Issue No: Vol. 137 (2016)
       
  • Influence of the clay type on the strength evolution of lime treated
           material
    • Authors: N. Maubec; D. Deneele; G. Ouvrard
      Pages: 107 - 114
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): N. Maubec, D. Deneele, G. Ouvrard
      This paper deals with the effects of lime addition on clay materials properties, in terms of mechanical and physico-chemical evolution. A coupling between these two aspects was undertaken in order to explain the mechanical behaviors of lime-treated clay materials. The study was performed on two different clays, a kaolin and a Ca2+-bentonite. Lime addition leads to an increase of mechanical properties of these clays. These improvements are faster with Ca2+-bentonite, even if at long term the performance reached for kaolinite is higher. The coupling between macroscopic and physico-chemical aspects shows that these improvements are linked to the development of secondary compounds such as calcium silicate hydrates, hydrogarnet and calcium carboaluminate hydrate phases.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.11.033
      Issue No: Vol. 137 (2016)
       
  • Remediation of metal contaminated soil by aluminium pillared bentonite:
           Synthesis, characterisation, equilibrium study and plant growth experiment
           
    • Authors: P. Kumararaja; K.M. Manjaiah; S.C. Datta; Binoy Sarkar
      Pages: 115 - 122
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): P. Kumararaja, K.M. Manjaiah, S.C. Datta, Binoy Sarkar
      In order to enhance the efficiency of metal immobilisation, bentonite clay was pillared with polyhydroxy aluminium complexes. The pillared bentonite was systematically characterised by multiple techniques including x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The clay product was assessed for its metal removal efficiency from aqueous systems through batch experiments with variables in pH, amount of adsorbent and initial metal concentration. The adsorption data were fitted with Langmuir and Freundlich isotherm models. The maximum monolayer adsorption capacity of pillared bentonite was 61.4, 32.3 and 50.3mgg−1 for Cu (II), Zn (II) and Ni (II), respectively. The immobilisation efficiency of pillared bentonite was assessed by greenhouse pot culture experiment with amaranth as the test crop. Amendment of soil with pillared bentonite at 2.5% significantly improved the plant growth as well as reduced the bioavailable metals in the metal spiked soils. The study demonstrated that pillared bentonite could potentially be used for addressing heavy metal pollutions by immobilising the metals in the contaminated soil.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.017
      Issue No: Vol. 137 (2016)
       
  • Nanoclay compatibilization of phase separated polysulfone/polyimide films
           for oxygen barrier
    • Authors: Ali Ammar; Ahmed Elzatahry; Mariam Al-Maadeed; Abdullah M. Alenizi; Abul F. Huq; Alamgir Karim
      Pages: 123 - 134
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Ali Ammar, Ahmed Elzatahry, Mariam Al-Maadeed, Abdullah M. Alenizi, Abul F. Huq, Alamgir Karim
      Polyimide (PI) and Polysulfone (PSF) films are used in many applications ranging from electronic film capacitors to membranes for gas separation and water purification, yet their phase separation issues limit many potential synergistic blend film applications. To this end, we examine the potential of nanoclays as non-traditional compatibilizers and re-enforcing agents in these technologically important polymer blend films. Herein, we quantify the effect of a nanoclay, Cloisite 30B on the phase separated blend film morphology compatibilization of PSF/PI and associated changes in its mechanical properties and film surface energy. Addition of as little as 1 mass% of organoclay strongly compatibilized the blend phases at all compositions, reducing the scale of blend phase separation by ~5–10 times, and interestingly, the net discreet surface phase separated domain area converged to that observed in 50% blend composition for other off-symmetric blend compositions. Clay compatibilization effects also induced a notable reduction of aspect ratio of surface phase separated domains in thin film blends, attributed to a high degree of exfoliation of the nanoclay by the PSF component so that the effective PSF domain interfacial tension with PI is reduced. Surface modification effects on topography leveling and surface energy changes are only qualitatively similar to our previous observations of block copolymer compatibilizer effect on polymer thin film blend phase separation. Thermal decomposition (TGA) measurements of PSF/PI films showed a decrease in thermal stability upon adding C30B due to its surfactant modification, while film mechanical tensile modulus properties improved slightly by adding low concentration of C30B (~1 mass%), but higher nanoclay loading decreased tensile strength and elongation at break. Finally we note that in terms of processing, the viscosities of the polymer solutions dramatically changed with addition 1 mass% and 3 mass% of C30B. We anticipate that more generally, nanoclays can act similarly to traditional polymeric compatibilizers in many aspects in suppressing polymer thin film blend phase separation that can have ramifications for many advanced technological applications such as sensors and membranes. To this end, we present preliminary oxygen barrier properties of adding Cloisite 30B on PSF/PI blend films.
      Graphical abstract image

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.012
      Issue No: Vol. 137 (2016)
       
  • Synthesis, characterization and efficiency of new organically modified
           montmorillonite polyethersulfone membranes for removal of zinc ions from
           wastewasters
    • Authors: Caprarescu Simona; Ianchis Raluca; Radu Anita-Laura; Sarbu Andrei; Somoghi Raluca; Trica Bogdan; Alexandrescu Elvira; Spataru Catalin-Ilie; Fierascu Radu Claudiu; Ion-Ebrasu Daniela; Preda Silviu; Atanase Leonard-Ionut; Donescu Dan
      Pages: 135 - 142
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Caprarescu Simona, Ianchis Raluca, Radu Anita-Laura, Sarbu Andrei, Somoghi Raluca, Trica Bogdan, Alexandrescu Elvira, Spataru Catalin-Ilie, Fierascu Radu Claudiu, Ion-Ebrasu Daniela, Preda Silviu, Atanase Leonard-Ionut, Donescu Dan
      The goal of the present paper was to study the separation efficiency of zinc ions of new synthesized polymer membranes based on polyethersulfone (PES) and organically (unmodified and modified) montmorillonite (Mt). The membranes were prepared by a combination of solution dispersion and wet-phase inversion methods. Further, the membranes were used in the removal of zinc ions at concentrations of 2g/L and 4g/L from aqueous model solution, at an applied voltage of 10V, via a laboratory-scale electrodialysis system. The presence of modified montmorillonite influenced the thermal behavior of the samples as evaluated by thermogravimetrical analysis. The XRD data indicated that partially exfoliated and/or intercalated montmorillonite PSf (nano) composite membranes were obtained. The presence of advanced modified montmorillonite influenced the water evaporation enthalpy calculated by DSC, the water contact angle, as well as the silicon peak according to XRF plots. The pore size decreased with montmorillonite addition according to SEM pictures while TEM photomicrographs showed that mostly intercalated nanocomposites were obtained. The performance of electrodialysis cell was evaluated in terms of mass flow (J) and rejection (R) of zinc ions, which increased with the increase of concentration of zinc ions. J and R values were higher, at 4g/L (45.40±0.12g− 2 h−1, 94.59±0.25%), for the membranes that incorporated the Mt functionalized with octadecyl chain which favored the dispersibility of the filler in the PSf membrane. Finally, advanced modified montmorillonite improved the separation efficiency of the final membranes.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.013
      Issue No: Vol. 137 (2016)
       
  • Synthesis and characterization of eco-friendly Ca-Al-LDH loaded with
           phosphate for agricultural applications
    • Authors: Marcela P. Bernardo; Francys K.V. Moreira; Caue Ribeiro
      Pages: 143 - 150
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Marcela P. Bernardo, Francys K.V. Moreira, Caue Ribeiro
      Controlled-release phosphate carriers based on hydrocalumite-like Layered Double Hydroxides (Ca-Al-LDHs) have been synthesized to serve as a P-source for Bradyrhizobium elkanii growth. [Ca-Al]-LDHs loaded with different phosphate contents were prepared by structural reconstruction (SR) and ion exchange (IE) and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), adsorption experiments, solid-state nuclear magnetic resonance (NMR) and thermal analysis (TG/DTG). [Ca-Al-PO4 3−]-LDHs comprising similar crystalline phases were formed regardless the phosphate uptake route. However, phosphate loadings were found to be higher in [Ca-Al-PO4 3−]-LDH obtained by IE rather than by SR. This was related to differences in specific surface area between precursors used in each route. [Ca-Al]-LDH IE-33.10mM significantly increased the growth of Bradyrhizobium elkanii, a nitrogen-fixing symbiotic bacterium widely used in crop (mainly soybean) plantations. Once [Ca-Al-PO4 3−]-LDHs are eco-friendly materials, they have enormous potential to be used in leguminous crops and raise agriculture production.

      PubDate: 2016-12-21T08:38:07Z
      DOI: 10.1016/j.clay.2016.12.022
      Issue No: Vol. 137 (2016)
       
  • A systematic approach to the synthesis of LDH nanoparticles by response
           surface methodology
    • Authors: Cecilia Vasti; Valeria Pfaffen; Ernesto Ambroggio; Mauricio R. Galiano; Ricardo Rojas; Carla E. Giacomelli
      Pages: 151 - 159
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Cecilia Vasti, Valeria Pfaffen, Ernesto Ambroggio, Mauricio R. Galiano, Ricardo Rojas, Carla E. Giacomelli
      The customization of the properties of layered double hydroxides nanoparticles (LDH-NPs) is essential to optimize their design innovative systems for biomedical applications. Response surface methodologies (RSMs), a collection of mathematical and statistical techniques that allows multivariate optimization of processes, are a useful tool for LDH-NPs customization. In this work, RSMs were used to study the synthesis parameters governing the size and composition of MgAl LDH-NPs (Mg/Al=3) labeled with fluorescein isothiocyanate (FITC2−) and prepare customized samples for biological assays. The influence of [Al 3+], [OH −]/[Mg 2++ Al 3+], 2[FITC 2−]/[Al 3+] and time of the hydrothermal treatment (tHT) was determined by a Box-Behnken experimental design (BBD). The experimental responses were hydrodynamic diameter (d H ), polidispersity index (PI) and FITC2− content (%FITC), and their dependence with the synthesis variables was described by polynomial model. The model correlated high [Al3+] with large d H values due to aggregation processes, while tHT was the main variable governing the size of the disaggregated units. These results were explained based on the precipitation and recrystallization mechanisms of LDH-NPs. The mathematical model derived from the BBD accurately predicted the synthesis conditions to obtain LDH-NPs with controlled d H values between 50 and 200nm, minimum PI and tunable %FITC. The convenience of the synthesized LDH-NPs for biological assays were tested in experiments with giant unilamellar vesicles and cell cultures monitored by confocal microscopy.
      Graphical abstract image

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.023
      Issue No: Vol. 137 (2016)
       
  • Preparation and characterization of organo-vermiculite based on
           phosphatidylcholine and adsorption of two typical antibiotics
    • Authors: Shuai Liu; Pingxiao Wu; Langfeng Yu; Liping Li; Beini Gong; Nengwu Zhu; Zhi Dang; Chen Yang
      Pages: 160 - 167
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Shuai Liu, Pingxiao Wu, Langfeng Yu, Liping Li, Beini Gong, Nengwu Zhu, Zhi Dang, Chen Yang
      In this study, a novel organoclay (PC-VER) was synthesized by modifying vermiculite (VER) with phosphatidylcholine (PC), and the adsorption characteristics of oxytetracycline (OTC) and ciprofloxacin (CIP) on PC-VER were further examined. The structural characteristics of PC-VER were analyzed by XRD, FTIR, TG and SEM/EDS, confirming that PC molecules were successfully introduced into VER. It was found that PC molecules cannot only intercalate into the interlayer space but also can adsorb on the external surface of VER if the solution contains water. This causes the decrease in specific surface area and increase in thermal stability. Zeta potential results show that PC-VER has a positively charged surface when the solution pH below 3. The kinetic study showed that the adsorption process of OTC and CIP both abided by pseudo-second-order model. The film-diffusion was the dominated controlling-step for the adsorption on VER, and both film and intra-particle diffusion controlled the adsorption on PC-VER. The adsorption isotherm could be well described by the Langmuir model, exhibiting an enhanced adsorption of OTC and CIP for PC-VER. Electrostatic attraction is the main mechanism for the adsorption on VER according to the effect of pH values and coexisting cations. For PC-VER, the enhanced adsorption of OTC was mainly controlled by hydrophobic interaction; while electrostatic attraction was a priority for the CIP adsorption. Results obtained from this study displayed that PC-VER could serve as a low-cost, suitable and eco-friendly material for adsorption of antibiotics.

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.002
      Issue No: Vol. 137 (2016)
       
  • Formulation study for softening of hard water using surfactant modified
           bentonite adsorbent coating
    • Authors: Nur Nadia Ab Kadir; Mohammad Shahadat; Suzylawati Ismail
      Pages: 168 - 175
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Nur Nadia Ab Kadir, Mohammad Shahadat, Suzylawati Ismail
      As an adsorbent coating of surfactants, sodium dodecylbenzene sulfonate (SDBS) modified bentonite (SMB) has been developed for the removal of Ca2+ and Mg2+ ions from hard water. The adsorbent was characterized using SEM-EDX, Zeta-meter and FTIR analyses. It has the potential to replace expensive conventional softening treatment techniques as well as reduce the usage of excess chemicals (chemical precipitation). Hard water can be easily treated using SMB by applying the adsorbent coating to the treatment area. Testing of adsorbent was carried out in terms of effect of surfactant ratio, effect of different types of binder as well as binder ratio. The best formulation of SMB was achieved by using polyvinyl acetate (PVAc) and bentonite in the ratio of 0.75:1.0 (w/w). Langmuir, Freundlich and Temkin isotherm models were tested to describe the optimum adsorption of Ca2+ and Mg2+ ions on SMB adsorbent coating. Thermodynamic and kinetic parameters were also examined for the adsorption of metal ions at different temperatures. SMB demonstrated the highest metal (Ca2+ and Mg2+) removal efficiency (29.27mgg−1) in 90min from 120mgL−1 hardness. On the basis of good removal capacity for Ca2+ and Mg2+ ions, SMB can be effectively used for treatment of metal ions in industrial wastewater, as well as softening of hard water.
      Graphical abstract image

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.025
      Issue No: Vol. 137 (2016)
       
  • Development of Hashin-Shtrikman model to determine the roles and
           properties of interphases in clay/CaCO3/PP ternary nanocomposite
    • Authors: Yasser Zare; Kyong Yop Rhee
      Pages: 176 - 182
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Yasser Zare, Kyong Yop Rhee
      The Hashin-Shtrikman model underpredicts the bulk, shear and Young's moduli of the prepared clay/CaCO3/PP ternary polymer nanocomposite (TPN) by ignoring the interphase between polymer matrix and nanoparticles. In this study, the Hashin-Shtrikman model was developed assuming the thickness and strength of interphases. Also, the thickness and strength of interphases in the ternary samples could be calculated by the developed Hashin-Shtrikman and Pukanszky models, respectively using the experimental results of mechanical properties. The predictions of the developed model showed good agreement with the experimental data at different Mt and CaCO3 contents assuming the interphase role which validate the current approach. According to the calculations, the strong and thick interphases were formed in the TPN at low nanofiller concentrations. This occurrence for the present samples was explained by the material and processing parameters. However, the thickness and strength of interphases weakened by increasing in clay content, probably due to the poor dispersion of nanoparticles and reduced interfacial area/adhesion at this condition.

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.033
      Issue No: Vol. 137 (2016)
       
  • Dispersion of kaolin particles with carboxymethylated xylan
    • Authors: Mohan K.R. Konduri; Pedram Fatehi
      Pages: 183 - 191
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Mohan K.R. Konduri, Pedram Fatehi
      In this work, the performance of carboxymethylated xylan (CMX) as a dispersant for kaolin particles in an aqueous system (20g/L) was systematically investigated. The influence of process parameters, such as pH and CMX dosage, on the kaolin dispersions was also determined. Adsorption studies revealed that CMX had a maximum adsorption of 2.48mg/g on kaolin particles under the treatment conditions of pH6, 15mg/g CMX/kaolin, 30°C and 30min. The minimum zeta potential of −33mV and the highest stability for the kaolin dispersions were found under the same treatment conditions using photometric dispersion, vertical scan analysis and turbidimetry. Isotherm and kinetic studies revealed that the adsorption of CMX on kaolin particles tended to significantly impact the zeta potential and relative turbidity of the kaolin dispersion, but the zeta potential did not necessarily predict the high stability of the kaolin dispersion. CMX improved the stability of the kaolin dispersions more than unmodified xylan (UX) and mechanical stirring.
      Graphical abstract image

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.027
      Issue No: Vol. 137 (2016)
       
  • Feasible preparation and characterization of tunable novel
           montmorillonite/block-copolymers based composites as potential dual
           adsorbent candidates
    • Authors: Hsuan-Hsuan Chen; Munusamy Thirumavalavan; Ru-Zhen He; Ya-Ting Shih; Jiunn-Fwu Lee
      Pages: 192 - 202
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Hsuan-Hsuan Chen, Munusamy Thirumavalavan, Ru-Zhen He, Ya-Ting Shih, Jiunn-Fwu Lee
      This study was mainly focused on exploring the possible intercalation of block-(diblock or triblock) copolymers into montmorillonite (Mt) to obtain clay mineral polymer nanocomposites (CPN) aiming to increase the interlayer space and application of Mt. The extent of the effect on interlayer space of Mt during reaction was studied in details. N2 adsorption isotherms and X-ray diffraction (XRD) studies were used to confirm the formation of CPN. It was found that the intercalation of polymers enhanced the interlayer space of Mt along with a shift of [001] plane 2θ (6.8°) to lower values. The corresponding interlayer space was increased from 12.65Å to 40.85Å. The intercalation of polymers to form CPN favors both structural orientations and functional groups for the preferential adsorption of both ionic (cationic and anionic inorganic) and non-ionic (organic, NOC) pollutants. Uptake of both organic (toluene; ethylbenzene; and xylene; in brief TEX) and inorganic (Cu2+, Pb2+ and Cr2O7 2−) pollutants were explored and highlighted in this study. The observed log K OC values for the distribution of organic pollutants onto CPN are significantly high in this study. In all cases the adsorption of Pb2+ was comparatively larger than that of Cu2+. Among all the obtained CPN, M-D-DMF displayed enhanced adsorption of both organic and inorganic pollutants and hence it was concluded as a potential candidate.
      Graphical abstract image

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.028
      Issue No: Vol. 137 (2016)
       
  • Microbial sulphide-producing activity in water saturated Wyoming MX-80,
           Asha and Calcigel bentonites at wet densities from 1500 to 2000kgm−3
    • Authors: Andreas Bengtsson; Karsten Pedersen
      Pages: 203 - 212
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Andreas Bengtsson, Karsten Pedersen
      Highly compacted bentonite is projected to function as a buffer against outward transport of radionuclides and inward transport of corrosive groundwater components for copper canisters with spent nuclear fuel in future Scandinavian geological repositories. The dominant long-term copper corrosive species will be sulphide from dissimilatory reduction of sulphate to hydrogen sulphide by sulphate-reducing bacteria (SRB). The effects from varying wet densities of MX-80, Asha and Calcigel bentonites, doped with SRB, on cultivability and sulphide-production of SRB were investigated. The studied commercial bentonites were all infested with cultivable SRB. While cultivability of SRB clearly decreased with increasing wet density of MX-80 and Calcigel, it remained relatively constant for most tested wet densities applied to Asha. The sulphide-production results for the three clays indicated intervals between 1740 and 1880kgm−3 in wet densities within which sulphide-producing activity dropped from high to very low or below detection. This work demonstrated that a high density of bentonite buffers in future spent nuclear fuel repositories will significantly reduce the risk for sulphide production in the buffer and concomitant corrosion of copper canisters.

      PubDate: 2016-12-28T09:49:10Z
      DOI: 10.1016/j.clay.2016.12.024
      Issue No: Vol. 137 (2016)
       
  • Effect of temperature on swelling pressure and compressibility
           characteristics of soil
    • Authors: Ramakrishna Bag; Ahsan Rabbani
      Pages: 1 - 7
      Abstract: Publication date: February 2017
      Source:Applied Clay Science, Volume 136
      Author(s): Ramakrishna Bag, Ahsan Rabbani
      Clays are being used for several construction purposes particularly as waste isolation barrier and undergo several temperature and hydraulic condition during operational period. Clays may undergo large compression during the particular loading condition. Bentonite is highly swelling clay containing high amount of montmorillonite mineral is considered as barrier and backfilling material for high level radioactive waste disposal repositories. The present study investigates the effect of temperature on swelling pressure and compressibility behavior of divalent rich Indian bentonite (liquid limit =139%) from Bikaner, Rajasthan and effect of temperature on compressibility behavior of local soil (liquid limit =35%) from Rourkela. A new oedometer was designed and developed in-house to carry out consolidation and swelling pressure tests at various temperatures. Swelling pressures tests on compacted bentonite specimens of targeted dry density 1.6Mg/m3 were conducted under constant volume condition for the temperature range between 25 and 90°C. Consolidation tests at various temperatures between 25 and 90°C for both soils were carried out using distilled water as inundating fluid. The study revealed that with increase in temperature the swelling pressure and compressibility index of bentonite increased. However, effect of temperature on compressibility behavior of local soil was found to be minimum.

      PubDate: 2016-11-25T07:49:43Z
      DOI: 10.1016/j.clay.2016.10.043
      Issue No: Vol. 136 (2016)
       
  • The removal of molybdates and tungstates from aqueous solution by
           organo-smectites
    • Authors: Barbara Muir; Damian Andrunik; Jakub Hyla; Tomasz Bajda
      Pages: 8 - 17
      Abstract: Publication date: February 2017
      Source:Applied Clay Science, Volume 136
      Author(s): Barbara Muir, Damian Andrunik, Jakub Hyla, Tomasz Bajda
      This paper presents the results obtained when studying the removal of molybdate and tungstate anions from aqueous using organically modified montmorillonite. In batch experiments, the influence of pH, reaction time, the initial concentration of Mo and W, and the influence of the amount and type of surfactant was investigated. The modification of smectite with leads to the formation of an organo-mineral complex characterized by a positively-charged surface and a high sorption capacity in the removal of Mo(VI) and W(VI). The pH effect determining the possibility of Mo and W removal from the aqueous solution. In the pH range of 1–5, the sorption of Mo and W efficiency is very high, while at pH>5 sorption is limited or completely inhibited. DDTMA-smectite and DDDDMA-smectite were recognized as the best sorbents. With an increasing amount of surfactant used in modification process, the sorption efficiency increases. Molybdates are removed from solutions compared to tungstates to a much greater extent – maximum sorption capacities were 705 and 390mmol/kg, respectively. Kinetic studies indicated that maximum sorption capacity is achieved faster in the case of Mo than of W, and that the main sorption mechanisms are chemisorption and ion exchange.
      Graphical abstract image

      PubDate: 2016-11-25T07:49:43Z
      DOI: 10.1016/j.clay.2016.11.006
      Issue No: Vol. 136 (2016)
       
  • Efficient preparation and application of palladium loaded montmorillonite
           as a reusable and effective heterogeneous catalyst for Suzuki
           cross-coupling reaction
    • Authors: Tian Li; Yanjun Liu; Feng-Shou Liu
      Pages: 18 - 25
      Abstract: Publication date: February 2017
      Source:Applied Clay Science, Volume 136
      Author(s): Tian Li, Yanjun Liu, Feng-Shou Liu
      The Na+ montmorillonite (Mt) was modified with l-cystine, and palladium was loaded via an ion-exchange reaction under microwave irradiation to obtain Pd@Mt. The entire process was conveniently carried out under mild reaction conditions in a matter of hours. The XRD, XPS and ICP-AES results confirmed the successful loading of palladium (0.55wt%). The so obtained Pd@Mt was subsequently explored as a catalyst for the Suzuki cross-coupling reaction and afforded the corresponding products in good to excellent yields for twenty reactants (in the range of 79–99%, only 3 reactants gave yields below 90%). The catalytic mechanism was investigated and discussed in detail. This supported catalyst could be easily recovered from the reaction mixture by simple filtration or centrifugation. Decreased palladium loss and improved reusability were achieved when the catalyst was recovered by filtration. Notably, this recovery method maintained the observed high yields, showing a >90% yield for the 6th run. Although palladium ions were reduced to Pd (0) in the cross-coupling reaction, only a small amount of aggregation was observed in the TEM images, where the diameters of the palladium particles on Mt were in nano scale.

      PubDate: 2016-11-25T07:49:43Z
      DOI: 10.1016/j.clay.2016.11.004
      Issue No: Vol. 136 (2016)
       
  • Effect of temperature on the rheological properties of neat aqueous
           Wyoming sodium bentonite dispersions
    • Authors: Zisis Vryzas; Vassilios C. Kelessidis; Lori Nalbantian; Vassilis Zaspalis; Dimitrios I. Gerogiorgis; Yiming Wubulikasimu
      Pages: 26 - 36
      Abstract: Publication date: February 2017
      Source:Applied Clay Science, Volume 136
      Author(s): Zisis Vryzas, Vassilios C. Kelessidis, Lori Nalbantian, Vassilis Zaspalis, Dimitrios I. Gerogiorgis, Yiming Wubulikasimu
      Temperature affects significantly the rheological behavior of neat water Wyoming Na-bentonite dispersions. The results of a very systematic study are presented regarding rheological measurements of 7% mass concentration at different temperatures, ranging between 25 and 80°C at atmospheric pressure. Higher temperature increased the shear stresses at low shear rates while the effect was much smaller at higher shear rates. The Herschel-Bulkley rheological model fitted extremely well all data. The yield stress increased linearly with temperature by almost three-fold, the flow consistency index decreased exponentially with temperature by almost five-fold and the flow behavior index increased by about 20%, tending towards the Newtonian value. At low shear rates (<100rpm corresponding to <170 1/s Newtonian shear rates), which represent very well the shear rates experienced by drilling fluids in the critical annulus region, all rheograms appeared fairly linear and the Bingham plastic model fitted well all data. The Bingham yield stress, from the low shear rate data, increased linearly with temperature, while the plastic viscosity decreased with temperature, in a manner very similar to the decrease of water viscosity with temperature. The plastic viscosity and Bingham yield stress data, from the low shear rate range, can be fitted well by an Arrhenius-type equation, with the activation energy for the plastic viscosity very similar to the activation energy for water viscosity, while for the Bingham yield stress, the activation energy is equal but opposite in sign to that of the plastic viscosity. A hypothesis is stated for the the observed linear increase of the yield stress with temperature, in the temperature range studied. One should be concerned when non-standard preparation and measurement procedures are followed which makes extremely difficult to understand any differences observed when reporting rheological data of water bentonite dispersions. A standard methodology is proposed, complementary to API, which can give very consistent results.

      PubDate: 2016-11-25T07:49:43Z
      DOI: 10.1016/j.clay.2016.11.007
      Issue No: Vol. 136 (2016)
       
  • Recent development of layered double hydroxide-derived catalysts
           −Rehydration, reconstitution, and supporting, aiming at commercial
           application−
    • Authors: Katsuomi Takehira
      Pages: 112 - 141
      Abstract: Publication date: February 2017
      Source:Applied Clay Science, Volume 136
      Author(s): Katsuomi Takehira
      Layered double hydroxide (LDH) has a unique feature, i.e., reconstitution of layered structure from the calcined oxides. The application of LDH as the heterogeneous catalysts by adopting reconstitution phenomenon and supporting on appropriate carrier were reviewed aiming at their commercial uses. After a short explanation on fundamental properties of LDH, such as phase transition by calcination and rehydration of calcined LDH (reconstitution of LDH by “memory effect”), their applications in the catalyst preparations were discussed. By adopting “memory effect”, the surface of LDH-derived mixed oxide was rehydrated or reconstituted as well as decorated with various metals and anions, resulting in an enhanced catalytic activity and selectivity via base sites activation and high dispersion of active metal species. Active OH− species, as Brønsted base, was produced on calcined Mg-Al LDH after the rehydration and exhibited high activity in various reactions. Catalytically active transition metals such as Ni, Fe and Mn were highly dispersed on Mg(Al)O via reconstitution, resulting in the high catalytic activity in dehydrogenation and oxidation reactions. Pt-Sn/Mg(Al)O catalysts prepared by adopting reconstitution phenomenon exhibited an excellent activity in the dehydrogenation of propane to propene. This is owing to the formation of highly dispersed and stable Pt-Sn bimetallic species on the catalyst surface. By supporting LDH on magnetic carriers such as ferrite, the catalyst became magnetically separable and could be utilized recyclably in the fine chemicals synthesis. Paper structured catalyst prepared from LDH by utilizing paper making technology opened new type usage of LDH materials which can be applied in the reforming catalysts for fuel cells. Moreover the reconstitution phenomena donate several beneficial properties to the LDH-derived mixed oxides in their uses as the heterogeneous catalysts. Reconstitution of LDH kinetically accelerated the conversion of anions such as toxic NO3 − and refractory (COO)2− in aqueous solution by entrapping the anions in the interlayer space of rehydrated LDH as observed on Pd-Cu/Mg(Al)O and Cu/Mg(Al)O catalysts, respectively. In the reforming of hydrocarbons for H2 production, self-regenerative activity appeared on trace amount of Pt doped Ni/Mg(Al)O catalyst by reversible oxidation-reduction between Ni0 and Ni2+ on/in Mg(Ni,Al)O periclase assisted by reversible change between periclase and LDH structure of the support. Both Pt-Ni/Mg(Al)O and Pt-Sn/Mg(Al)O catalysts exhibited excellent activities almost closing to the commercial uses.

      PubDate: 2016-11-25T07:49:43Z
      DOI: 10.1016/j.clay.2016.11.012
      Issue No: Vol. 136 (2016)
       
  • Characteristics of clay-rich raw materials for ceramic applications in
           Denizli region (Western Anatolia)
    • Authors: Semiz
      Abstract: Publication date: 1 March 2017
      Source:Applied Clay Science, Volume 137
      Author(s): Barış Semiz
      This study focuses on the evaluation of the potential use of the clay-rich raw materials in Denizli region to manufacture traditional ceramic products with industrial processing and determination of the provenance of archaeological ceramics. For this context, physical, chemical (X-ray fluorescence, XRF), mineralogical (X-ray diffraction, XRD), and thermal analysis (Differential Thermal Analyser-Thermogravimetry, DTA-TG) were performed and plasticity indexes (PI) were determined on the five representative clay-rich materials from three different locations (Yenicekent, Başkarcı and Pamukkale) in Denizli region. Samples have been prepared by pressing and firing in the range of 700–1200°C, then bulk density (BD), water absorption (WA), and unconfined compression strength (UCS) values of the samples were determined. Highly plastic clays were mainly composed of illite, smectite, kaolinite and mixed-layered clay minerals. Quartz, calcite, dolomite and hematite were also detected as non-clay minerals. Chemical composition of the clay samples without carbonate minerals indicated that the main oxide compositions were SiO2, Fe2O3 and Al2O3 whereas other oxides were present only in small quantities. Fired clays exhibited no major differences in BD and WA (except TR1). UCS values of all samples increased with rising firing temperatures. All technological properties showed significant densification at temperatures above 1000°C. One of the studied clay-rich materials (TR3) has comparable characteristics for the production of structural ceramics as references sample (KRC). Furthermore, this sample could be a potential raw material source for the archeological ceramics in the region. In order to use TR2 sample it is necessary to add more plastic clays to enhance its workability, but other clays are not appropriate for such products.

      PubDate: 2016-12-21T08:38:07Z
       
 
 
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