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  Subjects -> EARTH SCIENCES (Total: 652 journals)
    - EARTH SCIENCES (466 journals)
    - GEOLOGY (72 journals)
    - GEOPHYSICS (28 journals)
    - HYDROLOGY (22 journals)
    - OCEANOGRAPHY (64 journals)

EARTH SCIENCES (466 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted alphabetically
Acta Geochimica     Hybrid Journal   (Followers: 4)
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: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 19)
Advances In Physics     Hybrid Journal   (Followers: 19)
Aeolian Research     Hybrid Journal   (Followers: 5)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 4)
AMBIO     Hybrid Journal   (Followers: 15)
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     Open Access   (Followers: 13)
Annals of GIS     Hybrid Journal   (Followers: 21)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Anthropocene     Hybrid Journal   (Followers: 3)
Anthropocene Review     Hybrid Journal   (Followers: 7)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Geochemistry     Hybrid Journal   (Followers: 13)
Applied Geomatics     Hybrid Journal   (Followers: 3)
Applied Geophysics     Hybrid Journal   (Followers: 8)
Applied Ocean Research     Hybrid Journal   (Followers: 5)
Applied Petrochemical Research     Open Access   (Followers: 2)
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: 9)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 19)
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: 28)
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: 9)
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: 18)
Cadernos de Geociências     Open Access  
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 21)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 5)
Chemical Geology     Hybrid Journal   (Followers: 19)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 4)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 4)
Ciencia del suelo     Open Access   (Followers: 2)
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 25)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 8)
Computational Geosciences     Hybrid Journal   (Followers: 14)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 2)
Computers and Geotechnics     Hybrid Journal   (Followers: 10)
Contemporary Trends in Geoscience     Open Access   (Followers: 3)
Continental Shelf Research     Hybrid Journal   (Followers: 9)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 11)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 3)
Coral Reefs     Hybrid Journal   (Followers: 16)
Cretaceous Research     Hybrid Journal   (Followers: 7)
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: 2)
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 11)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 121)
Earth and Space Science     Open Access   (Followers: 13)
Earth Interactions     Full-text available via subscription   (Followers: 12)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 5)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 19)
Earth System Dynamics     Open Access   (Followers: 7)
Earth System Dynamics Discussions     Open Access   (Followers: 5)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 71)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 8)
Earthquake Science     Hybrid Journal   (Followers: 11)
Earthquake Spectra     Full-text available via subscription   (Followers: 18)
Ecohydrology     Hybrid Journal   (Followers: 11)
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: 26)
Environmental Geology     Hybrid Journal   (Followers: 20)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (Followers: 18)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 33)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (Followers: 13)
European Journal of Remote Sensing     Open Access  
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: 3)
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: 28)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 47)
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: 2)
Geoenvironmental Disasters     Open Access   (Followers: 3)
Geofluids     Open Access   (Followers: 4)
Geoforum     Hybrid Journal   (Followers: 23)
Géographie physique et Quaternaire     Full-text available via subscription   (Followers: 1)
Geography and Natural Resources     Hybrid Journal   (Followers: 7)
Geoheritage     Hybrid Journal   (Followers: 1)
Geoinformatica Polonica : The Journal of Polish Academy of Arts and Sciences     Open Access  
Geoinformatics & Geostatistics     Hybrid Journal   (Followers: 9)
Geological Journal     Hybrid Journal   (Followers: 14)
Geology Today     Hybrid Journal   (Followers: 25)
Geology, Geophysics and Environment     Open Access   (Followers: 1)
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   (Followers: 1)
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 27)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 34)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Geophysics     Full-text available via subscription   (Followers: 19)
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: 5)
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: 19)
Global Biogeochemical Cycles     Full-text available via subscription   (Followers: 15)
Gondwana Research     Hybrid Journal   (Followers: 8)
GPS Solutions     Hybrid Journal   (Followers: 17)
Grassland Science     Hybrid Journal  
Ground Water     Hybrid Journal   (Followers: 34)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 19)
Groundwater for Sustainable Development     Full-text available via subscription   (Followers: 3)
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: 21)
Hydrological Processes     Hybrid Journal   (Followers: 28)
Hydrology and Earth System Sciences     Open Access   (Followers: 28)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 54)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 12)
Indian Geotechnical Journal     Hybrid Journal   (Followers: 4)
Indonesian Journal on Geoscience     Open Access   (Followers: 2)
Interdisciplinary Environmental Review     Hybrid Journal   (Followers: 3)
International Geology Review     Hybrid Journal   (Followers: 16)
International Journal of Advanced Geosciences     Open Access  
International Journal of Advanced Remote Sensing and GIS     Open Access   (Followers: 36)
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: 36)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 15)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 38)
International Journal of Earthquake and Impact Engineering     Hybrid Journal   (Followers: 2)
International Journal of Geo-Engineering     Open Access   (Followers: 2)

        1 2 3 | Last

Journal Cover Applied Clay Science
  [SJR: 0.826]   [H-I: 83]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [3043 journals]
  • Inorganically modified clay minerals: Preparation, characterization, and
           arsenic adsorption in contaminated water and soil
    • Authors: Raj Mukhopadhyay; K.M. Manjaiah; S.C. Datta; R.K. Yadav; Binoy Sarkar
      Pages: 1 - 10
      Abstract: Publication date: October 2017
      Source:Applied Clay Science, Volume 147
      Author(s): Raj Mukhopadhyay, K.M. Manjaiah, S.C. Datta, R.K. Yadav, Binoy Sarkar
      The use of modified clay minerals for adsorbing arsenic (As) in contaminated soils is an underexplored area of research. The adsorption behavior of As onto inorganically modified smectite and kaolinite both in aqueous and soil media was studied. X-ray diffraction, infra-red spectroscopy, scanning and transmission electron microscopy studies confirmed successful modification of smectite through Fe-exchange and Ti-pillaring, and kaolinite through phosphate binding. The modified smectites were more efficient than phosphate-bound kaolinite in adsorbing As both in water and soil systems. Kinetic study revealed that the clay products reached adsorption equilibrium within 3h, and the data well fitted to the power function and simple Elovich equation (R2 >0.90). The Freundlich isotherm model best described the As adsorption data (R2 >0.86) of the modified clay products in both the systems. The Ti-pillared smectite exhibited the highest As adsorption capacity (156.54μgg−1) in the aqueous medium, while the Fe-exchanged smectite was the best material in the soil system (115.63μgg−1). The partition coefficient (Kd) and adsorption efficiency (%) data also maintained the similar trend. Precipitation of As and binuclear complex formation also took place in the soil system which made the metalloid non-labile as the time passed. The inorganically modified clay products reported here hold a great potential to adsorb As in contaminated groundwater, drinking water as well as soil.

      PubDate: 2017-08-03T10:13:25Z
      DOI: 10.1016/j.clay.2017.07.017
      Issue No: Vol. 147 (2017)
       
  • Pozzolanic activity of calcined halloysite-rich kaolinitic clays
    • Authors: Alejandra Tironi; Fernanda Cravero; Alberto N. Scian; Edgardo F. Irassar
      Pages: 11 - 18
      Abstract: Publication date: October 2017
      Source:Applied Clay Science, Volume 147
      Author(s): Alejandra Tironi, Fernanda Cravero, Alberto N. Scian, Edgardo F. Irassar
      The aim of this study is to determine the pozzolanic activity of clays with high content of halloysite/kaolinite, and to evaluate the influence of halloysite/kaolinite ratio and halloysite morphology in the development of pozzolanic activity of the calcined clays. For this purpose, three different natural clays from Río Negro Province, Argentine, were selected and completely characterized. After calcined at 700°C and ground to 80% of particle size <45μm, pozzolanic activity was determined using the electrical conductivity test, the Frattini test and the compressive strength index. Results show that all calcined clays are classified as high reactive pozzolana. The presence of kaolinite and spheroidal halloysite exerts great influence at early ages; while tubular halloysite has greater influence in the pozzolanic activity and the compressive strength of mortars at later ages.
      Graphical abstract image

      PubDate: 2017-08-03T10:13:25Z
      DOI: 10.1016/j.clay.2017.07.018
      Issue No: Vol. 147 (2017)
       
  • BiOCl-montmorillonite as a photocatalyst for highly efficient removal of
           Rhodamine B and Orange G: Importance of the acidity and dissolved oxygen
    • Authors: Chengqun Xu; Feng Long Gu; Honghai Wu
      Pages: 28 - 35
      Abstract: Publication date: October 2017
      Source:Applied Clay Science, Volume 147
      Author(s): Chengqun Xu, Feng Long Gu, Honghai Wu
      A BiOCl-Mt material assembled from BiOCl and Na-montmorillonite (Na-Mt) was characterized by XRD, FT-IR, TEM, XPS and UV–vis DRS. Na-Mt was clearly demonstrated to be capable of improving BiOCl's photocatalytic performance. The focus was placed on the evaluation of BiOCl-Mt in the terms of photocatalytic activity for cationic Rhodamine B (RhB) and anionic Orange G (OG). Both can be removed more efficiently using BiOCl-Mt compared with pure BiOCl under ultraviolet light irradiation. Although h vb + and O2 − are the two primary reactive species, the improved photocatalytic degradation performance is primarily attributed to the enhanced separation of photogenerated charge carriers in the catalyst. The Bronsted acidity derived from montmorillonite acid sites and the dissolved oxygen in the solution are capable of promoting dye photocatalysis because they effectively capture the photogenerated electrons. Under optimized conditions, TOC mineralization with rates of 82.3% for RhB and 85.9% for OG was obtained in a BiOCl-Mt catalysed photocatalysis process. The mechanism responsible for the oxidative decomposition of the two different dyes is primarily hole-driven. BiOCl-Mt was stable during the process, with its structures remaining almost unchanged after it was recycled three times. Therefore, BiOCl-Mt will have a promising worldwide application in dye-containing wastewater treatment.
      Graphical abstract image

      PubDate: 2017-08-03T10:13:25Z
      DOI: 10.1016/j.clay.2017.07.025
      Issue No: Vol. 147 (2017)
       
  • Bentonites functionalized by impregnation with TiO2, Ag, Pd and Au
           nanoparticles
    • Authors: Tatiane de Mattos Amadio; Dachamir Hotza; João Batista Rodrigues Neto; Magda Blosi; Anna Luisa Costa; Michele Dondi
      Pages: 1 - 6
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Tatiane de Mattos Amadio, Dachamir Hotza, João Batista Rodrigues Neto, Magda Blosi, Anna Luisa Costa, Michele Dondi
      This work aimed to characterize bentonites with different features and origins (Brazil, Argentina, Italy and United States) that were impregnated with Ag, TiO2, Pd and Au nanoparticles. Either commercial (TiO2) or synthesized (Ag, Pd and Au) nanoparticles (NP) were used and characterized by DLS and XRD. Subsequently, the dispersed NP was impregnated on bentonite by two alternative methods, imbibition or dipping. The efficiency of impregnation of bentonite by metallic nanoparticles was finally tested by ICP-OES, which was over 90% in all cases. Particularly, Ag nanoparticles showed an impregnation efficiency above 99%, as confirmed by SEM-FEG. To improve impregnation, a thermal pretreatment for the bentonites was necessary at 700°C. Both impregnation methods resulted in a suitable distribution and stability of Ag nanoparticles.

      PubDate: 2017-06-01T16:08:31Z
      DOI: 10.1016/j.clay.2017.05.028
      Issue No: Vol. 146 (2017)
       
  • Lauric acid/modified sepiolite composite as a form-stable phase change
           material for thermal energy storage
    • Authors: Qiang Shen; Jing Ouyang; Yi Zhang; Huaming Yang
      Pages: 14 - 22
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Qiang Shen, Jing Ouyang, Yi Zhang, Huaming Yang
      A series of novel composite phase change materials (PCMs) were prepared by impregnating lauric acid (LA) into the chemically modified sepiolite (SEP) via a vacuum impregnation method. Modification strategy was developed to improve the adsorption capacity of SEP, and the effects of thermal and chemical modification on the physical and chemical properties of SEP were investigated. The loading of LA inside the acid treated SEP could reach up to 60wt%, which was 50% higher than that of pristine SEP. The corresponding latent heats of the composite PCMs exhibited 125.2J/g at the melting temperatures of 42.5°C and 113.9J/g at the freezing temperatures of 41.3°C, respectively. The increased latent heat could be attributed to the better microstructure of the modified SEP. The thermal conductivity (0.59W/(m·k)) of the composite PCMs was higher than that of LA. The composite PCMs presented chemical and thermal reliability after 200 thermal cycling tests. The form-stable composite PCMs could be the promising candidate material for thermal energy storage.
      Graphical abstract image

      PubDate: 2017-06-01T16:08:31Z
      DOI: 10.1016/j.clay.2017.05.035
      Issue No: Vol. 146 (2017)
       
  • Magnesium oxide as alternative binder for unfired clay bricks
           manufacturing
    • Authors: Sandra Espuelas; Joshua Omer; Sara Marcelino; Angel Maria Echeverría; Andres Seco
      Pages: 23 - 26
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Sandra Espuelas, Joshua Omer, Sara Marcelino, Angel Maria Echeverría, Andres Seco
      Replacement of fired bricks by unfired ones could be an effective way to reduce the building industry environmental footprint: Their manufacture not only requires less energy and natural resources but also generates less waste. Bricks are based on the use of an additive cementitious material in the form of a binder, usually lime or cement. Such additives have a great environmental impact owing to the high energy consumption and CO2 during in their manufacturing process. In this article experiments are carried out in order to investigate the applicability of a MgO rich industry by-product as a binder for the production of unfired clay bricks. From the experiments, the MgO was observed to show ability to enhance the mechanical properties of a clay brick in much the same way as lime does. Water absorption tests on bricks revealed the superiority of MgO over lime in enhancing the durability properties of unfired bricks. The laboratory results demonstrate the high potential of MgO based additives as alternative binders to the calcium based ones. Consequently, this offers opportunity for reducing the environmental impact associated with the use of fired clay bricks. In addition, it could allow an effective way for the valorization of MgO containing industry by-products that currently discarded to landfills.

      PubDate: 2017-06-01T16:08:31Z
      DOI: 10.1016/j.clay.2017.05.034
      Issue No: Vol. 146 (2017)
       
  • Contribution of nanoclay to the additive partitioning in polymers
    • Authors: Aida Nasiri; Nathalie Gontard; Emmanuelle Gastaldi; Stéphane Peyron
      Pages: 27 - 34
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Aida Nasiri, Nathalie Gontard, Emmanuelle Gastaldi, Stéphane Peyron
      The polymer nanocomposites have become unabatedly popular due to their exceptional properties which results in a plethora of applications including the food packaging. However, safety aspect of these materials is still under debate, specifically in view point of the unknown interactions of nanoparticles with various additives added during the packages processing. For the commonly used polyolefins, the partitioning of additives rather than their diffusivity dictates the extant and extent of these interactions. In this work, the partitioning of various additives between a clay-polymer nanocomposite (CPN) and several food simulants was measured based on a worst-case scenario in viewpoint of the selected polymer and additives. The added value of the CPN in comparison with the pure polymer (LLDPE) was analyzed with regards to their Hansen solubility parameters and log K-log P linearity. Ultimately, an estimation method based on the Flory-Huggins theory was proposed to predict the partition coefficients in CPN.
      Graphical abstract image

      PubDate: 2017-06-01T16:08:31Z
      DOI: 10.1016/j.clay.2017.05.024
      Issue No: Vol. 146 (2017)
       
  • Chitosan and surfactant co-modified montmorillonite: A multifunctional
           adsorbent for contaminant removal
    • Authors: Lifang Zhu; Linhan Wang; Yin Xu
      Pages: 35 - 42
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Lifang Zhu, Linhan Wang, Yin Xu
      The demands for multifunctional adsorbents are increasing in these days because wastewater may simultaneously contain various types of contaminants. In this work, montmorillonite (Mt) was modified with both hexadecyltrimethylammonium (HDTMA) and chitosan (CTS), with the purpose of synthesizing multifunctional adsorbents that can efficiently adsorb hydrophobic organic contaminants, heavy metal cations, and dyes from water. The structural characteristics of the resulting modified samples (H/C-Mt) were first investigated using XRD, FTIR, TG, and Zeta potential measurements. According to the obtained results, both chitosan and HDTMA were intercalated into Mt interlayers, forming hydrophobic organo-phases. With increasing CTS loading amount, the basal spacing of C/T-Mt gradually increased, and the Zeta potential evolved from negative to positive. C/T-Mt could effectively uptake phenol, Cd2+, Conger red (CR), and crystal violet (CV) from water. The organo-phases created by HDTMA were responsible for the uptake of phenol on C/T-Mt, while the functional groups on CTS (e.g., OH, NH2) contributed to the adsorption of Cd2+. The positively charged surfaces of C/T-Mt, together with the hydrophobic interactions between C/T-Mt and contaminants, contributed to the effective uptake of CR on C/T-Mt. As for CV, the hydrophobic interactions should be the main reason for its adsorption on C/T-Mt. The obtained results suggested that C/T-Mt could be a multi-functional adsorbent for the effective uptake of different types of contaminants from water.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.027
      Issue No: Vol. 146 (2017)
       
  • Influence of allophane distribution on photocatalytic activity of
           allophane–titania composite films
    • Authors: Hiromasa Nishikiori; Shingo Matsunaga; Naoyuki Furuichi; Hitoshi Takayama; Koji Morita; Katsuya Teshima; Hiromi Yamashita
      Pages: 43 - 49
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Hiromasa Nishikiori, Shingo Matsunaga, Naoyuki Furuichi, Hitoshi Takayama, Koji Morita, Katsuya Teshima, Hiromi Yamashita
      Allophane–titania composite films were prepared from titanium alkoxide sols dispersing the natural clay mineral allophane as a nano-sized adsorbent. The composites of the titania dispersing the allophane particles in the whole film efficiently degraded trichloroethylene and acetaldehyde better than the normal titania and the titania dispersing the allophane only on the film surface. The titania dispersing the allophane particles in the whole film produced lower amounts of the intermediate products in certain stages than the titania. These results are due to the effective reactant transport from the allophane to titania. Photocatalytic degradation of glucose and photoelectrochemical measurements using an electrolyte solution containing glucose indicated that oxidative degradation of the glucose enhanced the generation of electricity during UV irradiation. A higher short circuit current was observed using the film dispersing the allophane on the surface layer with an ca. 50-nm thickness than the titania and those dispersing the allophane only on the film surface. Allophane effectively adsorbed the glucose molecules and transported them to the titania, then the products were desorbed into the liquid phase. Therefore, the holes were efficiently transported and consumed by the glucose oxidation.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.026
      Issue No: Vol. 146 (2017)
       
  • Determination of the specific surface area of layered silicates by
           methylene blue adsorption: The role of structure, pH and layer charge
    • Authors: Nóra Hegyesi; Richárd T. Vad; Béla Pukánszky
      Pages: 50 - 55
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Nóra Hegyesi, Richárd T. Vad, Béla Pukánszky
      The specific surface area of three layered silicates was determined by three independent methods; it was estimated from the average dimensions of individual silicate layers, determined by nitrogen adsorption using the BET model and calculated from the adsorption of methylene blue on their surface in aqueous sol. The BET model gave smaller surface areas than expected, because nitrogen molecules cannot penetrate freely into the interlayer space of the silicates. Geometric calculations and the methylene blue approach yielded very similar values for two different types of Laponite when the pH of the dispersion was adjusted to 6.5 or the edges of the silicate were modified with tetrasodium pyrophosphate dispersing agent. The measurement of surface area in water without the control of pH yielded smaller surface area, because methylene blue decreased the pH of the solution resulting in the competitive adsorption of methylene blue cations and protons at the basal surface. The methylene blue approach resulted in larger surface area than expected for the silicate with large ion exchange capacity, because of the tilted orientation of the adsorbed methylene blue molecules. All these factors must be considered during the use of the methylene blue method for the determination of the specific surface area of smectites.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.007
      Issue No: Vol. 146 (2017)
       
  • Stabilization of expansive Belle Fourche shale clay with different
           chemical additives
    • Authors: Mustafa Dayioglu; Bora Cetin; Soonkie Nam
      Pages: 56 - 69
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Mustafa Dayioglu, Bora Cetin, Soonkie Nam
      Improving the engineering properties of expansive soils is very important in northern plains, Texas and mid-west regions of the United States. In this study, expansive Belle Fourche clay (B) from South Dakota, was mixed with the class C fly ash (FC), class F fly ash (FF) and lime. Swelling pressure (SWP) and unconfined compressive strength (UCS) tests were conducted on samples that were cured at different periods (0, 7 and 28days). Furthermore, freeze and thaw (F-T) effects on the swelling and strength properties of the clay and selected mixtures were investigated. Results showed that the SWP of the Belle Fourche clay (B) decreased significantly with addition of lime 4% by dry weight of soil from 235kPa to almost 0kPa. Mixing fly ashes also reduced the SWP to 47kPa and 100kPa with class C and class F fly ashes, respectively. Increase in F-T cycles reduced the SWP, whereas the SWP increased with 2 and 4 F-T cycles for the mixtures with the fly ashes. However, after 4cycles, the pressure of the same mixtures decreased. On the contrary, to the clay-fly ash mixtures, F-T did not affect the SWP of the clay-lime mixtures. In terms of strength, chemical treatment increased UCS. The overall effectiveness of the treatment under the curing and F-T was in the order of FC, lime, and FF. The UCSs of the clays treated with these additives were 3.58, 1.82, and 1.63 times higher than the non-treated clay. F-T reduced the UCS of the clay and the clay treated with FF. Although the UCS of the FC and lime mixtures increased within 2cycles of F-T, they did not show the same strength improving performance with more F-T cycles. It was observed that mixtures with higher liquid limit and plasticity index (PI) tended to have higher SWP and lower UCS. This study claimed that chemically stabilized soils with high CaO content, CaO/SiO2, CaO/Al2O3, and CaO/(SiO2 +Al2O3) ratios had higher potential to decrease SWP of expansive soils and increase UCS of weak soils.

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.033
      Issue No: Vol. 146 (2017)
       
  • Mullite-zirconia composites prepared from halloysite reaction sintered
           with boehmite and zirconia
    • Authors: A. Raghdi; M. Heraiz; F. Sahnoune; N. Saheb
      Pages: 70 - 80
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): A. Raghdi, M. Heraiz, F. Sahnoune, N. Saheb
      In this study, Algerian halloysite, a naturally occurring clay mineral, was used as low-cost precursor for the production of mullite-zirconia composites. The halloysite was reaction sintered with boehmite and zirconia in the temperature range 1250–1650°C for 2h. Differential thermal analysis (DTA), thermogravimetry (TG), dilatometry, high temperature X-ray diffraction (XRD), and scanning electron microscopy (SEM) complementary techniques were used to characterize the prepared materials. The influence of ZrO2 content on the microstructure, densification, hardness, and coefficient of linear thermal expansion of the composites was investigated. Algerian halloysite was found suitable material for the synthesis of low-cost mullite based composites. All prepared samples exhibited same phase transformations that ended at 1550°C with the formation of monolithic mullite in halloysite-boehmite mixture and mullite-zirconia composites in halloysite-boehmite-zirconia mixture. The composite materials showed higher values of hardness and coefficient of linear thermal expansion compared with monolithic mullite. The composite containing 10% ZrO2 possessed the highest hardness value of 13.5GPa. The composite containing 30% ZrO2 possessed the lowest value of linear coefficient of thermal expansion of 7.5725×10−6 K−1 between 200 and 1500°C.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.037
      Issue No: Vol. 146 (2017)
       
  • Excavated soil waste as fine aggregate in fly ash based geopolymer mortar
    • Authors: P. Priyadharshini; K. Ramamurthy; R.G. Robinson
      Pages: 81 - 91
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): P. Priyadharshini, K. Ramamurthy, R.G. Robinson
      To explore the significance of geopolymer technology on producing environmental friendly waste based mortar which could be a sustainable replacement for conventional mortar; Low, medium and high plastic soil from different locations was used as fine aggregate to produce fly ash based geopolymer mortars. The experiments were designed using central composite design of response surface methodology. Molarity of NaOH, curing temperature and fly ash content were the key parameters considered in this study. The interaction effect of these parameters with four different fine aggregates (river sand, low, medium and high plastic soils) were identified and discussed. It is demonstrated that geopolymerisation helps in utilizing even high plastic soil as fine aggregate in construction applications. Soil based geopolymer mortar resulted in lower density range compared to conventional geopolymer of similar strength values. The test results show that strength and shrinkage properties of soil based geopolymer mortar significantly depends on the type of clay present in the soil. Geopolymer mix with each specific soil has an optimum combination of NaOH, curing temperature and binder dosage that helps them achieve the desired properties such as higher compressive strength and lower dry density, water absorption and shrinkage values.

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.038
      Issue No: Vol. 146 (2017)
       
  • Oxidative degradation of sulfanilamide catalyzed by Fe/Cu/Al-pillared
           clays
    • Authors: Sesegma Ts. Khankhasaeva; Elvira Ts. Dashinamzhilova; Darima V. Dambueva
      Pages: 92 - 99
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Sesegma Ts. Khankhasaeva, Elvira Ts. Dashinamzhilova, Darima V. Dambueva
      An oxidative degradation of an antibiotic sulfanilamide with hydrogen peroxide was carried out in the presence of Fe/Cu/Al-pillared clays as heterogeneous Fenton type catalysts. Fe/Cu/Al-pillared clays were synthesized by intercalation of layered aluminosilicate containing 95wt% montmorillonite with mixed polymeric Fe,Cu,Al-polyoxocations (Al/(Fe+Cu)=10/1, OH/(Fe+Cu+Al)=2.0mol/mol). The materials were characterized by chemical analysis, low-temperature nitrogen adsorption and XRD. Fe/Cu/Al-pillared clays were active catalysts for sulfanilamide oxidation with hydrogen peroxide in aqueous solutions: in the presence of these materials oxidation rate increased significantly and conversion of sulfanilamide reached 99–100%. The effect of experimental factors such as H2O2/sulfanilamide molar ratio, the catalyst content, the reaction temperature and the pH on the conversion of sulfanilamide were studied. The optimal conditions for the catalytic oxidation of sulfanilamide in the presence of Fe/Cu/Al-pillared clay that permit achieving a high conversion of sulfanilamide and catalyst stability were determined. The Fe/Cu/Al-pillared clay could be used in four consecutive cycles without regeneration and loss of activity. The main intermediate products of sulfanilamide oxidative degradation were sulfanilic acid, benzenesulfonic acid, p-benzoquinone and aliphatic carboxylic acids. The results of the study proved that Fe/Cu/Al-pillared clays were effective catalysts for oxidative degradation of sulfanilamide in aqueous solutions.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.018
      Issue No: Vol. 146 (2017)
       
  • Synthesis, cation exchange and dehydration/rehydration of sodium gordaite:
           NaZn4(OH)6(SO4)Cl·6H2O
    • Authors: Swami Area Maruyama; Fernanda Krause; Sergio Rodrigues Tavares Filho; Alexandre Amaral Leitão; Fernando Wypych
      Pages: 100 - 105
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Swami Area Maruyama, Fernanda Krause, Sergio Rodrigues Tavares Filho, Alexandre Amaral Leitão, Fernando Wypych
      Sodium gordaite (NaG - NaZn4(OH)6(SO4)Cl·6H2O) was synthesized under air and inert atmosphere and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and selected area electron diffraction spectra (SAED). Intercalated hydrated sodium cations from NaG were exchanged by calcium, potassium and lithium, presenting changes of basal distance from 13.03Å in NaG to, respectively, 16.1Å, 16.1 and 17.9Å (in the sample synthesized under air) and from 13.05Å in NaG to 17.8Å, 17.5 and 17.7Å (in the sample synthesized under inert atmosphere). In the samples synthesized under air, all compounds were co-intercalated with carbonate anions, especially those after the exchange reaction with Ca+2 and K+, while this contamination was almost completely removed when the NaG synthesis was performed under inert atmosphere.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.029
      Issue No: Vol. 146 (2017)
       
  • Production of clay ceramics using agricultural wastes: Study of
           properties, energy savings and environmental indicators
    • Authors: R. Sani; A. Nzihou
      Pages: 106 - 114
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): R. Sani, A. Nzihou
      In this study, agro-wastes were used as additive raw materials for the production of fired clay ceramics. The objectives of this study are to evaluate the impact of adding agro-wastes into clay body on the thermal and mechanical properties of ceramic materials, to determine the net energy consumption and to determine gas emissions during firing process. The clay and agro-wastes were characterized by chemical elemental analysis, thermogravimetric and differential thermal analysis (TGA-DTA). The fired clay ceramics were produced with clay and optimal proportions of wheat straw (WS) and olive core flour (OCF). The thermal and mechanical properties were evaluated by measuring thermal conductivity with hot-disk method and bending test respectively. The results showed that for clay incorporated OCF (4, 8wt%) and WS (3, 7wt%), thermal conductivity was decreased by 16 to 30%. However, the mechanical strength of the same samples has slightly decreased respectively. TGA-DTA provided an approach to estimate the heat required or released for both clay and agro-wastes thermal decomposition. The addition of agro-wastes into the clay body showed that energy consumption of fired clay ceramics production decreased to above 36% for clay incorporated 4wt% OCF (C-4wt%OCF). The energy saving during the firing process was a tangible outcome. In order to determine the impact of the agro-wastes addition, the environmental indicators were discussed for the clay incorporated WS and OCF respectively. Total gas yield released were measured by Micro-GC after the combustion of clay incorporated OCF and WS in fixed bed reactor respectively. The analysis of gas emissions are related to the combustion of organic and inorganic compounds of agro-wastes and clay body, respectively. The CO2 emissions coming from the combustion of agro-wastes reached up to 4.38% for C-8wt%OCF. However, the CO2 emissions associated with decarbonatation of clay body decreased. Adding agro-wastes into the clay body results to improving thermal properties without negative impact on the mechanical properties of ceramic materials, also to a significant energy saving and decreasing of the inorganic CO2 emissions related to the decarbonatation of clay body. The relevance of this work, pointed out in the data presented in regards to the state-of-the art is that the paper is focused on fired clay ceramic properties, on energy savings and on the evaluation of environmental indicators in the laboratory scale.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.032
      Issue No: Vol. 146 (2017)
       
  • The modification of rectorite with carbon layers and trisodium
           trimetaphosphate for the removal of Pb2+
    • Authors: Ning Wang; Zhitao Feng; Xiaofei Ma; Pengwu Zheng
      Pages: 115 - 121
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Ning Wang, Zhitao Feng, Xiaofei Ma, Pengwu Zheng
      At the presence of rectorite (Rec), starch was treated with hydrothermal carbonization to fabricate carbon layer with many oxygen containing groups on the surface of Rec layer, which were further reacted with trisodium trimetaphosphate (STMP) to introduce phosphate ester groups on Rec. The obtained RecCPN were used to remove heavy metal ions from aqueous solution. The adsorption kinetics and isotherms could be described with the pseudo- second-order model and the Langmuir model. The maximum monolayer adsorption capacities could reach 258.40mg/g for RecCPN at pH5 and 303K, in which the Pb2+ adsorption processes was spontaneous. The positive values of ΔH0 indicated that the interaction of Pb2+ with phosphate ester groups was endothermic. RecCPN still exhibited the good adsorption capacity in the adsorption-desorption cycles. In addition, RecCPN showed advantageous selectivity towards Pb2+ over other metal ions (Cu2+, Ni2+, Co2+ and Cd2+) and still removed above 90% Pb2+ at the initial trace Pb2+ concentration (0.5mg/L).

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.044
      Issue No: Vol. 146 (2017)
       
  • Estimating Hofmeister energy in ion-clay mineral interactions from the
           Gouy-Chapman theory
    • Authors: Wei Du; Rui Li; Xinmin Liu; Rui Tian; Wuquan Ding; Hang Li
      Pages: 122 - 130
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Wei Du, Rui Li, Xinmin Liu, Rui Tian, Wuquan Ding, Hang Li
      Hofmeister effects are of scientific importance in cation-clay mineral interactions. In this study, we present a kinetics-based approach to estimate the Hofmeister energy of such interactions from the Gouy-Chapman theory. Montmorillonite was employed as the experimental material; the Hofmeister energies of Cs+ and Na+ were estimated. A mathematical relationship between the Hofmeister energy (as well as the classical Coulomb energy and the total energy) of a cation and its equilibrium adsorption amount was first established based on the modified Gouy-Chapman theory; the miscible displacement technique was then employed to estimate the amount of the cation adsorbed at equilibrium. The Hofmeister energy was calculated by introducing the equilibrium adsorption amount into the established mathematical relationship. The validity of the suggested approach was further corroborated. Our study indicated that the observed Hofmeister energy in cation-clay mineral interactions cannot be explained by cationic size, hydration, or dispersion forces. The observed Hofmeister energy bears two important characteristics: it increased with an increase of electric field strength, and it was much larger for the softer Cs+ cation than for the harder Na+ cation. These characteristics implied that Hofmeister effects in cation-clay mineral interactions are closely related to the changes of cationic energy in the strong electric field near the clay mineral surface. Because of the strong Hofmeister energy from the Gouy-Chapman theory, the apparent charge of Cs+ increased from the normal/typical value of +1 to an effective charge of +2.354; in contrast, the apparent charge of Na+ merely increased from the normal/typical +1 to an effective charge of +1.112 in this clay mineral system.

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.039
      Issue No: Vol. 146 (2017)
       
  • One-pot exfoliation of kaolinite by solvothermal cointercalation
    • Authors: Éva Makó; András Kovács; Viktoria Antal; Tamás Kristóf
      Pages: 131 - 139
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Éva Makó, András Kovács, Viktoria Antal, Tamás Kristóf
      A one-pot solvothermal synthesis procedure of kaolinite-cetyltrimethylammonium chloride complex directly from kaolinite-urea precursor to produce kaolinite nanoscrolls is reported. Compared to the commonly applied solution/stirring method, the applied solvothermal synthesis is simple, convenient and effective, requiring an order of magnitude less time and reagent volume. The type of precursor, as well as the reaction time and temperature significantly affect the exfoliation rate of kaolinite. In addition, a strong correlation is demonstrated between the effectiveness of exfoliation and the interaction between the guest molecules and the octahedral sheets of kaolinite. The present findings reveal that the eco-friend kaolinite-urea precursor is favorable for direct intercalation of cetyltrimethylammonium chloride from methanol solution at 100°C (and at equilibrium vapor pressure of methanol), and that the formed kaolinite-cetyltrimethylammonium chloride complex can easily transform into kaolinite nanoscrolls. This conceptually new method utilizing supposed cointercalation processes can open the way to a new series of cost-efficient chemical routes for the direct exfoliation of kaolinite.
      Graphical abstract image

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.042
      Issue No: Vol. 146 (2017)
       
  • Adsorption of switchable surfactant mixed with common nonionic surfactant
           on montmorillonite: Mechanisms and arrangement models
    • Authors: Xiaojun Hu; Senlin Tian; Shujiao Zhan; Jianxi Zhu
      Pages: 140 - 146
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Xiaojun Hu, Senlin Tian, Shujiao Zhan, Jianxi Zhu
      To improve understanding of adsorption behavior of mixed surfactants on typical clay components in soil for potential applications of surfactant-enhanced remediation (SER) technologies during remediation of hydrophobic organics-contaminated soil, the adsorption mechanisms and arrangement models of an electrochemical switchable cationic surfactant (11-Ferrocenylundecyl) trimethylammonium bromide (FTMA), mixed with the nonionic surfactant Tween 80 on montmorillonite were investigated. The mixed system in the presence of Tween 80 remains electrochemically reversible. The adsorption isotherms of the pure FTMA and FTMA-Tween 80 mixed system on montmorillonite were Langmuir type. The major mechanism of pure FTMA adsorption is via cation exchange as the total capacity is close to the cation exchange capacity (CEC) of montmorillonite. With the addition of Tween 80, the cation exchange of FTMA would be weakened by the function of hydrogen bonding. As the added concentration of FTMA and Tween 80 are 2874mg/L and 50 times of critical micelles concentration of Tween 80, adsorption capacity of FTMA and mixed surfactants decrease from 280.6 to 235.2mg/g and 400 to 298mg/g. Moreover, the adsorption capacity of Tween 80 linearly decreases from 118.7 to 62.7mg/g. Meanwhile, as the amount of FTMA increases from 0.4 to 1.0 times CEC of montmorillonite, the arrangement model of FTMA in the interlayer of montmorillonite changes from a flat monolayer, lateral bilayer to pseudotrilayer. When mixed with Tween 80, the interlayer space of montmorillonite increased significantly, and it showed a gradual increasing trend of interlayer space as the concentration of Tween 80 increased. The results of the present study show that the combined use of cationic and nonionic surfactants can reduce the adsorption loss of surfactants during remediation of polluted soil and then be conducive to the application of SER technologies.

      PubDate: 2017-06-06T16:20:07Z
      DOI: 10.1016/j.clay.2017.05.025
      Issue No: Vol. 146 (2017)
       
  • The pyrolysis kinetics of the conversion of Malaysian kaolin to metakaolin
    • Authors: M. Irfan Khan; Hafeez Ullah Khan; Khairun Azizli; Suriati Sufian; Zakaria Man; Ahmer Ali Siyal; Nawshad Muhammad; M. Faiz ur Rehman
      Pages: 152 - 161
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): M. Irfan Khan, Hafeez Ullah Khan, Khairun Azizli, Suriati Sufian, Zakaria Man, Ahmer Ali Siyal, Nawshad Muhammad, M. Faiz ur Rehman
      The aim of this work was to study the pyrolysis kinetics of the thermal transformation of kaolin to metakaolin with the aid of models and model free isoconversional methods. Thermal treatment in the range of 600–850°C is used to convert kaolin into an amorphous and highly reactive metakaolin (MK). In this study, the thermal transformation of kaolin to metakaolin was investigated using thermokinetics and instrumental analysis. Kaolin was subjected to thermogravimetric analysis (TGA) at heating rates of 10, 20 and 40°C/min, in the temperature range of 50–800°C. Approximately, 14.2% of mass loss was recorded during the TG analysis. 95% of the degree of dehydroxylation was attained at 635°C, representing the minimum temperature for this process. The TGA and its related data were analyzed using model free (based on DTG, DTA and TG) and model based kinetics methods. Both DTG and DTA peak temperatures were employed for the thermokinetics of kaolin using Ozawa, Kissinger and Starink methods; giving an E a in the range of 246.6–252.5kJ·mol−1. A slight higher average E a (266–267kJ·mol−1 vs 246.6–252.5kJ·mol−1) was observed when TGA based integral methods (KAS, FWO and Starink) were used. The mechanism of the thermokinetics was investigated using the Redfern model and the best fitting was given by 3rd order chemical reaction (F3) function. Both model-free and model based thermokinetics methods could be used to validate the thermal transformation of kaolinite to metakaolinite.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.017
      Issue No: Vol. 146 (2017)
       
  • Characterization of Tunisian clay suitable for pharmaceutical and cosmetic
           applications
    • Authors: S. Gamoudi; E. Srasra
      Pages: 162 - 166
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): S. Gamoudi, E. Srasra
      The aim of this study is to assess the suitability of purified Tunisian clay for its possible pharmaceutical and cosmetic uses. Mineralogical, chemical and physicochemical characterization was performed with the aid of tools like X-ray diffraction (XRD), Chemical composition, DTA/TGA analysis, Cation exchange capacity (CEC), particle size distribution by laser dispersion (PSD), surface area (BET method), Point of zero charge (PZC) and surface charge density σH. Pharmacopoeia tests were also carried: Swelling capacity, sedimentation volume and pH measurement. For microbiological tests, the absence of Salmonella species, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was tested. The X-ray diffraction data revealed that the Tunisian sample is an interstratified illite-smectite. The percentage of smectitic fraction is estimated to be 78%. The chemical, textural and porosimetric results show important values suggesting that this mineral clay can function in creams, powders and emulsions. In view of the fundamentals of major pharmacopoeias for use of bentonite in pharmacy and considering the swelling capacity and sedimentation volume values, and microbiological results we could designate a pharmaceutical acceptable denomination for Tunisian purified clay.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.036
      Issue No: Vol. 146 (2017)
       
  • Heterogeneous poly(ionic liquids) catalyst on nanofiber-like palygorskite
           supports for biodiesel production
    • Authors: Wen Zhang; Meisheng Li; Jie Wang; Yijiang Zhao; Shouyong Zhou; Weihong Xing
      Pages: 167 - 175
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Wen Zhang, Meisheng Li, Jie Wang, Yijiang Zhao, Shouyong Zhou, Weihong Xing
      New heterogeneous poly(ionic liquids) catalysts (PAL-PILs) were successfully prepared by grafting polymerization of acid ionic liquids (ILs) (1-butysulfonate-3-vinylimidazole hydrogen sulfate) onto nanofiber-like palygorskite (PAL) supports that had been, in advance, covalently modified by γ-methacryloxypropyl trimethoxy silane (OPAL). Using the ester yields and PILs grafting degrees as main indexes, the optimized immobilization conditions were that the mass ratio of OPAL to ILs monomer was 1:2, the immobilization temperature and time were 60°C and 30h, the initiator (2,2′-Azobis(2-methylpropionitrile) dosage was about 5wt%, respectively. Then, the esterification between methanol and oleic acid was carried out to investigate the catalytic properties of PAL-PILs. For the homogeneous ILs catalyst, the yield of methyl oleate was about 85%. For the PAL-PILs, on which only about 41% of ILs used in homogeneous catalysis was immobilized, the yield could reach over 69% after reacting only 5h at 75°C at atmospheric pressure, when the molar ratio of methanol to oleic acid is adjusted to 12:1. More importantly, the yield of methyl oleate still maintained at about 22% after 6 recycling experiments. Moreover, the PAL-PILs catalysts exhibited efficient catalytic properties and could be recycled easily. These results offer great potential for the PAL-PILs in the biodiesel production for further research.
      Graphical abstract image

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.031
      Issue No: Vol. 146 (2017)
       
  • Modelling the deterioration of the near surface caused by drying induced
           cracking
    • Authors: Ross A. Stirling; Stephanie Glendinning; Colin T. Davie
      Pages: 176 - 185
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Ross A. Stirling, Stephanie Glendinning, Colin T. Davie
      Assets such as roads, railways, pipelines and flood embankments are inherently vulnerable to the action of weather and in the long term, climatic change. Their exposure makes them highly susceptible to deterioration during the course of their design life and beyond. The drivers of deterioration are believed to be human (e.g. traffic, maintenance) and environmental (e.g. weather, pollution, burrowing) but the actual deterioration processes are not well understood. Among the weather-driven processes, it is believed that desiccation of the near-surface and the development of cracking can significantly influence the mechanical, hydrological and thermal behaviour of geotechnical structures primarily by impacting the transmission of water between the atmosphere and soil. Enhanced infiltration during rainfall events can potentially lead to rapidly elevated pore water pressures and reduced shear strength and is widely cited as the strength reduction mechanism behind the wide spread failure of infrastructure slopes. This paper describes the development of a pseudo-discrete continuum Finite Difference model and its application to investigate the influence of soil properties (including elastic modulus, hydraulic conductivity and soil-water retention) on the desiccation process and eventual crack initiation and propagation behaviour. The generation of a desiccated crust typified by highly negative pore pressures and increasingly disintegrated texture is demonstrated. The influence of projected higher drying rates and seasonal drying-wetting cycles (that could result from climate change) on crack pattern development is investigated to gain an understanding of progressive deterioration. This points towards the potential for increased future deterioration rates of geotechnical infrastructure.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.06.003
      Issue No: Vol. 146 (2017)
       
  • The time-dependent swelling of argillaceous rock under
           resaturated conditions
    • Authors: L.L. Wang; R.W. Yang; S. Chanchole; G.Q. Zhang
      Pages: 186 - 194
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): L.L. Wang, R.W. Yang, S. Chanchole, G.Q. Zhang
      The evolution of argillaceous rock suffering from desaturation/resaturation is a key factor that affects the safety of deep geological repositories of radioactive waste. However, the behavior of this rock when resaturated to nearly 100% relative humidity (RH) has been poorly studied, because water condensation was frequently encountered in the conventional RH-control technique. This issue has been overcome in the present work using an environmental scanning electron microscope (ESEM) that provides improved RH control. The recorded micrographs subsequently were analyzed for full-field strain measurement using digital-image correlation techniques. The results reveal that the swelling (the sample in the size of several millimeters) attained stability in less than an hour during the 30%–80% RH step; however, the swelling strain continued to rise for up to 10h during the 80%–99% RH step. The anomalous time-dependent swelling at nearly 100% RH is not explicable in terms of hydraulic flow or propagation of swelling-induced microcracks. The evolution of strain fields shows that the areas of continuous swelling are located mainly inside the clay matrix. We suggest that the creep-like swelling of clay might be related to an osmotic flow (driven by a solute-concentration gradient) that dissipates more slowly than the hydraulic flow (driven by pressure gradient). The existence of time-dependent swelling in argillaceous rock under resaturated conditions should be considered for the reliability assessment of long-term radioactive waste disposal.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.041
      Issue No: Vol. 146 (2017)
       
  • The formation mechanism of organoammonium-kaolinite by solid-solid
           reaction
    • Authors: Ding Wang; Qinfu Liu; Dandan Hou; Hongfei Cheng; Ray L. Frost
      Pages: 195 - 200
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Ding Wang, Qinfu Liu, Dandan Hou, Hongfei Cheng, Ray L. Frost
      Solid-solid reactions and its corresponding solution method have been utilized to study the formation and intercalation mechanism of organoammonium-kaolinite formed from quaternary ammonium salt and kaolinite (Kaol) by using a methoxy-modified Kaol as an intermediate. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential scanning calorimetry (TG–DSC) analysis. Results showed that butyl trimethylammonium and hexyl trimethylammonium ions were successfully intercalated into the silicate layers, while the larger ions (CnH2n+1N(CH3)3 +, n≥8) were not. The intercalated alkylammonium ions were lying flat and poorly packed between the interlayer spaces of Kaol. In addition, a similar thermal behavior in the products obtained by both methods was also revealed. During the intercalation process, the alkylammonium ions were introduced by ion-dipole intercalation. In addition to the ion-dipole force, some other factors may contributed to these results, such as the geometrical constraint, the pH value of the mixed solution, the adsorbed water molecules, and the charge distribution at the external surfaces (the latter three will play a role if solutions are used). When solid-state reaction was used, the attraction caused by ion-dipole force was not strong enough to overcome the geometrical constraints, therefore larger alkylammonium ions were not intercalated.
      Graphical abstract image

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.022
      Issue No: Vol. 146 (2017)
       
  • Methodological reconstruction of dioctahedral 1:1 phyllosilicate polytypes
    • Authors: Carlos E. Teixeira; Paulo R.G. Brandão; Ricardo W. Nunes
      Pages: 201 - 205
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Carlos E. Teixeira, Paulo R.G. Brandão, Ricardo W. Nunes
      The layered kaolin-group minerals are composed mainly by three polytypes: kaolinite, dickite and nacrite. The geometrical polytypic reconstruction of these phases regards both the topological properties of individual networks (e.g., OH network linked to the hexagonal siloxane surface) and energetic aspect of superposition of cations. Starting from early attempts made by Bookin and Newnham, Zvyagin, Dornberger-Schiff and Durovic proposed their own symbolic representation of these structures. This work used the symbolic proposal of Zvyagin to prepare a methodological strategy to build the 52 species of dioctahedral polytypes. Two examples are shown to demonstrate the methodology and the CIF file of all the structures are made available.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.06.001
      Issue No: Vol. 146 (2017)
       
  • Molecular dynamics simulation of hydrated Na-montmorillonite with
           inorganic salts addition at high temperature and high pressure
    • Authors: Camara Moussa; Jiafang Xu; Xiaopu Wang; Jun Zhang; Zhe Chen; Xiaodi Li
      Pages: 206 - 215
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Camara Moussa, Jiafang Xu, Xiaopu Wang, Jun Zhang, Zhe Chen, Xiaodi Li
      The swelling behaviors of Na-montmorillonite (Na-Mt) in non-ambient environment have been the subject of considerable speculation due to the difficulties associated with their study. Inorganic salts are often used to minimize clay mineral hydration. The influence of inorganic salts addition (NaCl, CaCl2, KCl) on the hydration of Na-Mt at high temperature and high pressure (HTHP) was investigated by molecular dynamics simulation at 6GPa and different temperatures (200, 300, 400, 500 and 600K) in an isobaric isothermal ensemble (NPT). Water model and force field used in the clay-water system are SPC/E model and universal force field (UFF), respectively. The results show that after adding inorganic salts into Na-Mt, the mobility of the interlayer species increases, and the hydration shell of the interlayer cations decreases with a rise in temperature. The influence of temperature on the diffusion of water molecules is much greater than that of the ions present in the interlayer. Temperature increase and hydration degree play an important role on the diffusion behavior of the interlayer species. The size, valence, mass and hydration energy of cations present between the layers affect the structure of Na-Mt interlayer. The inorganic salts are able to inhibit the hydration of Na-Mt by reducing the mobility of the interlayer species and the basal spacing. After analyzing the effect of each salt on Na-Mt, it was found that, the most stable state of Na-Mt at HTHP is achieved with KCl addition, compared with NaCl and CaCl2. It is expected the results obtained from this study would help to understand the inhibition effect of inorganic salts on Na-Mt, and predict the swelling of Na-Mt at HTHP.

      PubDate: 2017-06-11T16:36:27Z
      DOI: 10.1016/j.clay.2017.05.045
      Issue No: Vol. 146 (2017)
       
  • Layered europium hydroxide system for phosphorous sensing and remediation
    • Authors: Cláudia C.L. Pereira; João Carlos Lima; Artur J. Moro; Bernardo Monteiro
      Pages: 216 - 222
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Cláudia C.L. Pereira, João Carlos Lima, Artur J. Moro, Bernardo Monteiro
      A Layered Lanthanide Hydroxide (LLH) material based on europium (LEuH, Eu8(OH)20Cl4.6H2O) was intercalated with 2,6-naphtalenedicarboxylate (NDC) yielding a material presenting the bright red luminescence characteristic of Eu3+, both by direct excitation of europium and energy transfer from NDC. The material behaves as a sensor towards anions which display the ability to exchange with NDC. The sensor was tested with several anions (phosphate, sulphate, pyrophosphate, acetate, and tetraborate anions) and the changes in NDC (λem =380nm) and europium (λem =615nm) emission intensities upon excitation of NDC (λex =357nm), were studied. Phosphate was found to have the highest degree of intercalation and displayed a strong increase (400% fold) on the fluorescence intensity of NDC. The presence of phosphate was further confirmed with Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES). Taking advantage of LEuH selectivity towards phosphate, its applicability in phosphorus remediation was studied presenting high sequestration capacity followed by controlled release of phosphate in three consecutive cycles and improved stability of the LEuH host material. These results highlight the significant potential of LLHs as new scavenging agents for inorganic phosphate.
      Graphical abstract image

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.06.002
      Issue No: Vol. 146 (2017)
       
  • Geothermal clay-based geopolymer binders: Synthesis and microstructural
           characterization
    • Authors: Qian Wan; Feng Rao; Shaoxian Song; Carlos Alberto León-Patiño
      Pages: 223 - 229
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Qian Wan, Feng Rao, Shaoxian Song, Carlos Alberto León-Patiño
      Geothermal clay rich in kaolinite was first prepared into geopolymer binders. Preparation conditions of calcination on geothermal clay, Na2SiO3 and NaOH combination in alkaline activator, and water content were studied. Thermal nature of the geothermal clay was characterized by TG-DSC and XRD measurements, which shows characteristics of kaolinite and cristobalite during calcination. Mechanical property, morphology and microstructure of the geothermal clay-based geopolymers were characterized by compressive strength measurements, SEM observation and NMR spectra analysis. With optimal synthesizing parameters, geothermal clay-based geopolymer possessed a compressive strength of 19.5MPa, as well as a homogeneous geopolymeric gel with high percentages of Q 4 (2Al) and Q 4 (1Al). As geothermal clay is supposed to be of intermediate dissolution reactivity in geopolymerization, this synthesis might extend the kinds of raw aluminosilicates in geopolymer formation.

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.05.047
      Issue No: Vol. 146 (2017)
       
  • Improving flame retardancy of IFR/PP composites through the synergistic
           effect of organic montmorillonite intercalation cobalt hydroxides modified
           by acidified chitosan
    • Authors: Qinghong Kong; Ting Wu; Hongkai Zhang; Yi Zhang; Manman Zhang; Tianyu Si; Lin Yang; Junhao Zhang
      Pages: 230 - 237
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Qinghong Kong, Ting Wu, Hongkai Zhang, Yi Zhang, Manman Zhang, Tianyu Si, Lin Yang, Junhao Zhang
      To improve the flame retardancy of IFR/PP composites, organic montmorillonite (Mt) intercalation cobalt compounds (Co-OMt) were prepared and modified by acidified chitosan to further expand the interlayer spacing of Mt. The Co-OMt/IFR/PP nanocomposites were fabricated via melt blending method. The results indicated that cobalt hydroxides and acidified chitosan were successfully intercalated into interlayers of Mt, which promoted the fine dispersion of Co-OMt in PP matrix. The results of limiting oxygen index (LOI) and vertical burning (UL-94) tests indicated that IFR/PP composites only reached V-2 rating and the LOI value was 26.5%. With addition of 4mass% Co-OMt, 4mass% Co-OMt/IFR/PP nanocomposites passed UL-94 V-0 rating and the LOI value was high to 32.1%. Furthermore, the cone calorimeter tests results confirmed that peak heat release rate (PHRR), total heat release (THR) and peak smoke production rate (PSPR) of 4mass% Co-OMt/IFR/PP nanocomposites decreased by 33.7%, 11.8% and 16.7% compared with those of IFR/PP composites. The notably improved flame retardant and smoke suppression properties were attributed to the fine dispersion of Co-OMt with layered structure and excellent catalytic performance in PP matrix, which promoted the fully cover of consolidated and compact residual layers on the surface of polymer during combustion, ultimately suppressing heat and mass transfer between polymer matrix and flame zone.

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.05.048
      Issue No: Vol. 146 (2017)
       
  • Synthesis of a kaolin-based geopolymer using a novel fusion method and its
           application in effective water softening
    • Authors: M. Naghsh; K. Shams
      Pages: 238 - 245
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): M. Naghsh, K. Shams
      In this study, kaolin-based geopolymer was synthesized using a two-step method that consists of a fusion step (fusion of kaolin and sodium hydroxide), and a hydration and dealkalization step. The fusion step was performed at a temperature range of 400–800°C for 10 to 20h, and the hydration and dealkalization step was carried out by washing the fusion product with demineralized water for a short time (<10min). The synthesized geopolymer was characterized using XRD, FTIR, SEM, EDS and BET analyses. The sorption efficiency of the synthesized geopolymer was examined via removing Ca2+ and Mg2+ from both model media and groundwater. Results showed that sodium hydroxide to kaolin ratio, fusion time and temperature have profound effects on the performance of geopolymer in reduction of water hardness. Response Surface Methodology (RSM) was used to determine the optimal geopolymer synthesis conditions. RSM results indicated that the sodium hydroxide to kaolin ratio of >2.2, the fusion time of >14h and the fusion temperature range of 500–700°C provide the optimal synthesis conditions. Moreover, the synthesized geopolymer can efficiently adsorb Ca2+ and Mg2+ from both model media and groundwater. Based on the Langmuir isotherm model, the maximum Ca2+ adsorption capacity was 76.34mg/g at 25°C, increasing to 94.34mg/g at 45°C. Similarly, the maximum Mg2+ adsorption capacity increased from 39.68mg/g at 25°C to 51.55mg/g at 45°C. The adsorption experimental data at the above mentioned temperatures (i.e., 25 and 45°C) fitted well with the pseudo-second-order model. Finally, efficient regeneration of the saturated geopolymer, using sodium chloride solution, suggested that the dominating mechanism of water softening by the synthesized geopolymer is ion exchange.

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.06.008
      Issue No: Vol. 146 (2017)
       
  • Sepiolite-TiO2 nanocomposites for photocatalysis: Synthesis by microwave
           hydrothermal treatment versus calcination
    • Authors: Feng Zhou; Chunjie Yan; Hongquan Wang; Sen Zhou; Sridhar Komarneni
      Pages: 246 - 253
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Feng Zhou, Chunjie Yan, Hongquan Wang, Sen Zhou, Sridhar Komarneni
      Sepiolite-TiO2 nanocomposites were synthesized by conventional calcination process and microwave hydrothermal (M-H) treatment and were tested and compared for their photocatalytic activity. XRD analysis indicated that nanocomposites after calcination at 500°C or M-H treatment for 40min at about 200°C appear to be the optimal conditions, which assured the amorphous TiO2 to crystalline anatase phase transition. The deposition of the TiO2 on the surface of sepiolite by M-H treatment yielded small dispersed nanoparticles at all treatment times used in this study. However, TiO2 particle size increased with increasing calcination temperature, which was confirmed by SEM and TEM. N2-adsorption-desorption isotherms indicated that calcination process reduced the specific surface areas of the nanocomposites while the M-H treatment led to a higher surface area with better photocatalytic performance for the degradation of Orange G. The intact structure of sepiolite and the homogeneous dispersion of the TiO2 nanocrystals on sepiolite surfaces led to enhanced photocatalytic activity in M-H treated samples.
      Graphical abstract image

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.06.010
      Issue No: Vol. 146 (2017)
       
  • In situ high temperature X-ray diffraction study of illite
    • Authors: Guanyu Wang; Hejing Wang; Nan Zhang
      Pages: 254 - 263
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Guanyu Wang, Hejing Wang, Nan Zhang
      Despite extensive researches, many aspects of the structural transformation that occur in illite on heating remain unclear. This study concentrates on samples from a mine located in Wenzhou, Zhejiang Province, China to supplement data obtained by previous investigators. In situ high temperature X-ray diffraction (HTXRD), infrared spectroscopy (IR), field emission scanning electron microscope (FESEM) and electron microprobe (EMP) analysis were used to record the characterization of the raw material. XRD pattern showed the illite sample was primarily in 2M1 polytype. The phase transition from illite into dehydroxylated phase started at about 525°C in static air and at about 550°C in vacuum, and from dehydroxylated phase into mullite occurred at above 1100°C. These lattice parameters of illite (RT – 1100°C) and mullite (1125–1150°C) both in static air and in vacuum were refined. The variations of illite lattice parameters with temperature (°C) were therefore well described. Thermal expansion coefficients of illite (RT – 1100°C) were determined. In situ high temperature X-ray diffraction study revealed four stages during heating: expansion, dehydroxylation, post-dehydroxylation and mullite stages.

      PubDate: 2017-06-17T01:46:04Z
      DOI: 10.1016/j.clay.2017.06.006
      Issue No: Vol. 146 (2017)
       
  • Characterization and electrochemical treatment of a kaolin
    • Authors: Juan Carlos Flores Segura; Víctor Esteban Reyes Cruz; José de Jesús Pérez Bueno; Elda Marlem Lozada Ascencio; Felipe Legorreta García
      Pages: 264 - 269
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Juan Carlos Flores Segura, Víctor Esteban Reyes Cruz, José de Jesús Pérez Bueno, Elda Marlem Lozada Ascencio, Felipe Legorreta García
      In this work, studies on characterization and electrochemical treatment of kaolin from the municipality of Agua Blanca, Hidalgo, Mexico were carried out, in order to identify its properties and establish the operating conditions for an electrochemical purification treatment. Different characterization techniques were used in order to quantify this clay characteristics, such as X-ray diffraction, scanning electron microscopy, analysis of the whiteness index, particle size, FTIR, Induced Coupled Plasma Spectroscopy, Z potential, cyclic voltammetry, chronopotentiometry and chronoamperometry. This study shows that the tested clay had a high content of kaolinite, but also impurities, such as: quartz, iron oxides, and titanium oxides. These impurities have an influence on the surface charge of the kaolin particles and therefore on their properties. The clay with a heat treatment exhibited a thermal behavior characteristic of this type of clays. The particle size range was between 0.5 and 100μm with an average particle size about 15μm. The voltammetry study revealed that a reduction processes occur in a range of 0.07 to −1.2V (E vs. SCE) and, when a cell potential of 3.3V for 24h was imposed, there was a decrease of about 43% in the amount of iron oxides present in the ore. This reduction was of particular significance for the cleaning process.

      PubDate: 2017-06-22T12:03:56Z
      DOI: 10.1016/j.clay.2017.06.004
      Issue No: Vol. 146 (2017)
       
  • Pore fluid salinity effects on physicochemical-compressive behaviour of
           reconstituted marine clays
    • Authors: Miao-Miao Song; Ling-Ling Zeng; Zhen-Shun Hong
      Pages: 270 - 277
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Miao-Miao Song, Ling-Ling Zeng, Zhen-Shun Hong
      It has been well recognized that pore fluid salinity significantly affects physical and mechanical properties of clays. However, how to correlate the pore fluid salinity effects on mechanical behaviour with physicochemical variations induced by pore fluid salinity changes is still pending. This study investigates the changes in liquid limit, oxide compositions and compressibility with pore fluid salinity, based on experimental data obtained from reconstituted specimens of two marine clays in China. It is found that oxide compositions vary little with the change in pore fluid salinity, indicating that no chemical reaction occurs during pore salt changing for the investigated clays. Such a finding means that the pore fluid salinity effects on compression behaviour of reconstituted clays can be attributed to the variations in physical properties. For the investigated marine clays with illite as predominant clay mineral, the void ratio at liquid limit is the crucial physical index of assessing the pore fluid salinity effects on the compression behaviour. The intrinsic compression concept is also introduced to compare the compression behaviour of reconstituted clays with and without pore salt. A quantitative approach is proposed to assess the pore fluid salinity effects on the compression behaviour of marine clays reconstituted at different initial water contents.

      PubDate: 2017-06-22T12:03:56Z
      DOI: 10.1016/j.clay.2017.06.015
      Issue No: Vol. 146 (2017)
       
  • Synthesis, characterization and antibacterial properties of novel
           nano-silver loaded acid activated montmorillonite
    • Authors: Anasuya Roy; B.S. Butola; Mangala Joshi
      Pages: 278 - 285
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Anasuya Roy, B.S. Butola, Mangala Joshi
      This paper reports synthesis, characterization and antibacterial properties of a novel silver-exchanged montmorillonite (Ag-Mt) synthesized from acid activated sodium montmorillonite (Na-Mt). The silver-loaded nanostructures (Ag-Mt) were synthesized in a two-step approach in which Na-Mt was first converted into acid activated Na-Mt and further treated with two concentrations of silver nitrate solution to obtain two types of acid activated Ag-Mt for comparison, Ag-Mt without the acid activation step and isotropic silver nanoparticles were synthesized as control samples. EDX confirmed successful loading of elemental silver in all types of Ag-Mt and WXRD analysis showed undisturbed crystal structure with increased interlayer space compared to Na-Mt. TEM micrographs revealed formation of spherical silver nanocrystals on the supporting silicate layers although no external reducing agent was employed due to high reduction potential of silver ions. The results were further confirmed in UV spectroscopy where strong absorption bands related to the surface plasmon resonance (SPR) was observed. The bactericidal efficacy of the clay minerals were evaluated against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus using disk diffusion method which showed excellent inhibitory properties and large inhibition zones of all synthesized Ag-Mt. The minimum inhibitory concentration (MIC) of the clay minerals was also quantified and compared with synthesized isotropic silver nanoparticles. Acid activated Ag-Mt showed antimicrobial activity marginally lower than silver nanoparticles alone, although the silver content was ~10 times lower than Ag-NP. This antibacterial agent is thus very effective and more attractive in terms of cost and environment friendly nature.
      Graphical abstract image

      PubDate: 2017-06-22T12:03:56Z
      DOI: 10.1016/j.clay.2017.05.043
      Issue No: Vol. 146 (2017)
       
  • Synthesis and characterization of nano-sized α-alumina powder from kaolin
           by acid leaching process
    • Authors: Sunipa Bhattacharyya; Pallavi Suhasinee Behera
      Pages: 286 - 290
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Sunipa Bhattacharyya, Pallavi Suhasinee Behera
      α- alumina powder with particle size <100nm and spherical shape was prepared from calcined kaolin by acid leaching method. Here hydrochloric acid was used as a leaching agent. The amorphous white powders formed after precipitation, washing and drying were characterised by the different technique like XRD, TG-DSC and FTIR. Particle size distribution, specific surface area and microstructural analysis of the 1200°C calcined powder were also carried out to ascertain the size, shape and distribution of the particles. The phase pure α-alumina with a size range <100nm, was formed at 1200°C. The presence of a surfactant during processing also exhibited a positive effect on modification of particle size.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.017
      Issue No: Vol. 146 (2017)
       
  • Valorization of KCl/PHPA system of water-based drilling fluid in presence
           of reactive clay: Application on Algerian field
    • Authors: A. Gueciouer; A. Benmounah; H. Sekkiou; R. Kheribet; B. Safi
      Pages: 291 - 296
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): A. Gueciouer, A. Benmounah, H. Sekkiou, R. Kheribet, B. Safi
      During the drilling when using water-based drilling fluid, the swelling issue is encountered, particularly in reactive clay section. After a bibliographical review showing a fundamental divergence from already published results depending on the type of system and shale inhibitors products used, this paper describes an experimental plant to measure inhibition level of KCl/PHPA system on reactive clays. For this, the current study provides more information on the potential of the mud system as well as its influence on the essential properties of drilling fluids. Qualification testing reported here shows that the use of combination of PHPA product and KCl meets the characteristics of performance. The series of X-rays Diffraction analysis were conducted on cutting samples collected from different depths of Ain Amenas field, the results obtained allowed to say that all the samples have different percentages of swelling clay that represent a source Potential of high-reactivity clay materials. Moreover, a series of physico-chemical and rheological analysis were performed on these cutting samples, in order to allow the valuation of the KCl/PHPA system in water based drilling fluids.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.007
      Issue No: Vol. 146 (2017)
       
  • Studies on clay-gelatin nanocomposite as urea sensor
    • Authors: Anshu Sharma; Kamla Rawat; H.B. Bohidar; Pratima R. Solanki
      Pages: 297 - 305
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Anshu Sharma, Kamla Rawat, H.B. Bohidar, Pratima R. Solanki
      Homogeneous gelatin organogel-based nanocomposite (GA-NC) was prepared by Lap as fillers. For customized thermal and viscoelastic properties, saturation binding of Lap to GA chain was probed in aqueous solution, and Lap=0.03% (w/v), (glycerol)=30% (v/v) and (GA)=3% (w/v) was used for organogel nanocomposite. The Lap platelets were successfully exfoliated in the organogel matrix giving rise to a homogeneous phase. The interaction of GA-NC with urea was studied using electrochemical as well as optical technique. For electrochemical study, a thin film of this GA-NC was prepared onto indium tin oxide (ITO) coated glass plate via drop-casting. This GA-NC/ITO electrode was characterized by electrochemical, FTIR and SEM techniques. This GA-NC/ITO electrode exhibited electrochemical response specific for urea with sensitivity of 32.7 and 5.56µA mM−2 cm−2 in the two concentration range of 0.1 to 2 and 2 to 20mM, respectively. The electrochemical profile of this electrode was sensitive towards urea which opens up the possibility for development of strip-based enzyme-free sensors for field applications. This GA-NC material in solution phase also shows optical response for urea with binding constant of 63.93M−1.
      Graphical abstract image

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.012
      Issue No: Vol. 146 (2017)
       
  • Combined effect of epoxy functionalized graphene and
           organomontmorillonites on the morphology, rheological and thermal
           properties of poly (butylenes adipate-co-terephtalate) with or without a
           compatibilizer
    • Authors: Salima Adrar; Abderrahmane Habi; Abdellah Ajji; Yves Grohens
      Pages: 306 - 315
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Salima Adrar, Abderrahmane Habi, Abdellah Ajji, Yves Grohens
      In this work, clay polymer nanocomposites (CPN) with simultaneous dispersion of graphene and organomontmorillonites (OMt) in a poly (butylene adipate-co-terephthalate) (PBAT) biodegradable matrix were prepared, using the melt-blending technique. Two different OMt were used non polar Cloisite15A and polar Cloisite30B with a composition of 3 mass% as well as epoxy functionalized graphene (EFG) with different compositions (1, 3, 5 mass%). The morphology and thermal properties of OMt/PBAT, EFG/PBAT and OMt-EFG/PBAT nanocomposites were studied. A compatibilizing agent (PBATgMA) was elaborated by grafting maleic anhydride on PBAT chains. The effect of incorporation of this compatibilizer on the different nanofillers dispersion in PBAT matrix was studied. The structure of the nanofillers/PBAT nanocomposites was examined using X-ray diffraction analysis and transmission electron microscopy (TEM). The co-addition of EFG with OMt allowed a better dispersion of these nanofillers and more intercalated structures were obtained. The rheological results showed an increase of the storage modulus G′ in the different nanofillers/PBAT nanocomposites, particularly after the co-addition of OMt and EFG. The thermal properties evaluated by TGA were sensibly improved by the association of these nanofillers. From all these results, it can be speculated that a synergism phenomenon between graphene and OMt was produced in the PBAT matrix. However, this phenomenon was reduced after the addition of PBATgMA compatibilizer, probably because of repulsive interactions were produced between this compatibilizing agent and the epoxy functionalized graphene.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.009
      Issue No: Vol. 146 (2017)
       
  • Deformation characteristics and stress responses of cement-treated
           expansive clay under confined one-dimensional swelling
    • Authors: Sopheap Por; Satoshi Nishimura; Suched Likitlersuang
      Pages: 316 - 324
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Sopheap Por, Satoshi Nishimura, Suched Likitlersuang
      This study presents an investigation of the effects of cement addition to expansive clay on its deformation characteristics and stress responses during swelling. The effects were evaluated by focusing on the unconfined compressive strength, swelling-shrinkage strains under various conditions, and the lateral coefficient of earth pressure during one-dimensional deformation for artificial mixtures of two different clays at three different ratios. The clays used in this study were a Na-montmorillonite bentonite and a non-expansive Bangkok clay, mixed at different proportions to simulate naturally encountered expansive clays with different degrees of swelling potential. The experimental programme involved unconfined compression, areal shrinkage strain by unconfined drying, vertical free swelling strain, and confined swelling pressure tests. The experimental results show that the cement addition led to marked decreases in the areal shrinkage strain and vertical free swelling strain in addition to the obvious improvement of strength and stiffness of soils. The confined swelling pressure test results indicated that the cement had a greater effect in reducing vertical swelling pressure than the lateral swelling pressure of the soils during one-dimensional swelling. The measured lateral coefficient of earth pressure and stress paths of untreated and cement-treated soils and their engineering implications are discussed.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.022
      Issue No: Vol. 146 (2017)
       
  • Effects of grinding montmorillonite and illite on their modification by
           dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate
    • Authors: Wuhui Luo; Takeru Fukumori; Binglin Guo; Kwadwo Osseo-Asare; Tsuyoshi Hirajima; Keiko Sasaki
      Pages: 325 - 333
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Wuhui Luo, Takeru Fukumori, Binglin Guo, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko Sasaki
      Montmorillonite (Mt) and illite (Ilt) were ground for different times under wet condition and sequentially subjected to organic modification by dioctadecyl dimethyl ammonium chloride (DDAC). The influence of the grinding time on the obtained products in terms of DDAC loading and ClO 4 − adsorption were evaluated. Multiple techniques were used to characterize the changes in structure and morphology before and after mechanical or organic modification. Compared with Ilt, Mt showed a stronger resistance to mechanical treatment due to its swelling property. Silicon nuclear magnetic resonance (29Si NMR) spectra and X-ray diffraction (XRD) patterns of samples ground for 30min indicate the disintegration of Ilt and exfoliation of Mt, resulting in increase of ClO 4 − uptake by 147% for OIlt and 13% for OMt. Three stages in the grinding Mt can be proposed, including the separation of large particles into small particles, exfoliation of small particles, and disintegration of exfoliated single layers. In contrast, two stages are involved in the grinding Ilt, which are the destruction/exfoliation of large particles and further disintegration of small exfoliated layers.
      Graphical abstract image

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.025
      Issue No: Vol. 146 (2017)
       
  • Provenance and circulation of Bell Beakers from Western European societies
           of the 3rd millennium BC: The contribution of clays and pottery analyses
    • Authors: M. Isabel Dias; M. Isabel Prudêncio; António C. Valera
      Pages: 334 - 342
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): M. Isabel Dias, M. Isabel Prudêncio, António C. Valera
      This work intends to contribute for the discussion of beaker's social role in Western Europe, by studying Central - South Portugal evidences, establishing provenance and therefore pottery transactions between sites and/or regions, emphasizing the circulation /diffusion of this kind of pottery, and their impact on the European societies of the 3rd millennium BC. Ceramics from four relevant Chalcolithic - early Bronze Age archaeological sites of Central and Southern Portugal are studied, based on compositional paste analysis, confronting the bell beakers with other typologies, complemented with local/regional clays characterization. A broader spatial relationship is established, especially with other Iberian sites, and in the European context. Compositional studies were done by instrumental neutron activation analysis (INAA) and X-ray diffraction (XRD). Results for the four sites emphasize that some bell beakers have chemical composition similar to the other typologies, associated with local raw materials close to the archaeological site, pointing to local productions. On the other hand, the outliers identified are mainly comprised of bell beakers, assuming an exogenous nature. Thus, bell beakers are a complex material expression, where local productions are in relation with interregional systems of circulation of ideas and materials.
      Graphical abstract image

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.026
      Issue No: Vol. 146 (2017)
       
  • Drinking water treatment sludge as an efficient adsorbent for heavy metals
           removal
    • Authors: S.A. Abo-El-Enein; Ahmed Shebl; S.A. Abo El-Dahab
      Pages: 343 - 349
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): S.A. Abo-El-Enein, Ahmed Shebl, S.A. Abo El-Dahab
      Green chemists paid much more attention towards the alternative ways to reutilize waste materials instead of its disposal in a non-ecofriendly manner. In this study, drinking-water treatment sludge (DWTS), which is a by-product resulted from drinking water treatment plants, was successfully applied as an adsorbent for Pb(II), Cd(II) and Ni(II) removal from wastewater. The physicochemical characteristics of DWTS were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms. The XRD analysis revealed that the DWTS under study consists of quartz and illite phases which had been reported for their adsorption efficiency. Firing of DWTS at 500°C causes the appearance of albite phase in addition to previous ones which enhances the adsorption capacity of these materials. The influence of different parameters such as firing temperature of DWTS, contact time, pH, DWTS dose and initial metal ions concentration on the adsorption of heavy metal ions and, consequently, on their removal were investigated. DWTS exhibit an adsorption efficiency towards Pb(II)>Cd(II)>Ni(II). The extremely high efficiency of DWTS towards Pb(II) adsorption can nominate it as a specific low-cost adsorbent for Pb ions.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.027
      Issue No: Vol. 146 (2017)
       
  • Effects of talc on fire retarding, thermal degradation and water
           resistance of intumescent coating
    • Authors: H. Hazwani Dzulkafli; Faiz Ahmad; Sami Ullah; Patthi Hussain; Othman Mamat; Puteri S.M. Megat-Yusoff
      Pages: 350 - 361
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): H. Hazwani Dzulkafli, Faiz Ahmad, Sami Ullah, Patthi Hussain, Othman Mamat, Puteri S.M. Megat-Yusoff
      This study presents the influences of talc as an additive in intumescent coating formulations on the thermal insulation, degradation and water resistance. The fire test was performed according to ASTM-E119 standard to study the heat shielding properties of the coated substrates. The results showed that the 20% of the talc enhanced the heat shielding and recorded substrate temperature 75°C after 100min of fire test. The morphology of the char was analyzed by Scanning Electron Microscopy (SEM). X-ray fluorescence (XRF), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) results showed the presence of P2O5, MgO, TiO2, and SiO2 respectively. The functional groups analysis of char confirmed the presence of high temperature compounds and enhanced thermal performance of coatings. Thermogravimetric analysis (TGA) showed that addition of 20% talc increased residual mass of the char by 55.55%. The lap shear test result showed that the talc also improved the adhesion of the intumescent coating with steel substrate and the highest shear strength observed was 7MPa for a formulation, F5 containing 20% talc. Water immersion test was performed according to ASTM D870-15 and the results showed the higher water-resistance was recorded for a formulation containing 10% talc in the control formulation.

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.013
      Issue No: Vol. 146 (2017)
       
  • A novel method for the preparation of inorganic and organo-modified
           montmorillonite essential oil hybrids
    • Authors: Aris Giannakas; Ioannis Tsagkalias; Dimitris S. Achilias; Athanasios Ladavos
      Pages: 362 - 370
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Aris Giannakas, Ioannis Tsagkalias, Dimitris S. Achilias, Athanasios Ladavos
      In this study, a novel method which can be easily applied in industry for the modification of sodium exchanged montmorillonite (NaMt) and commercial organically modified montmorillonite (OrgMt) with essential oils (EO) such as oregano oil, thyme oil and basil oil was presented. The obtained clays-essential oils powders were promising nanostructures for controlled release applications. The presence of EO molecules in the interlayer space was studied with X-ray diffraction (XRD) analysis. Thermogravimetric Analysis (TG) was used to calculate the adsorbed amount of EO into NaMt and OrgMt clay layers and to determine the temperature region where EO release took place. Fourier-Transform Infrared (FTIR) spectroscopy was used to study the adsorption mechanism. The interlayer space of NaMt was found not to be affected by the adsorption of EO molecules while a significant increase of OrgMt interlayer space was recorded. EO amount released from NaMt surface above 220°C and between 100°C to 220°C in OrgMt. A hydrogen bond between OH groups of EO and external surface OH groups of NaMt in the case of NaMt/EO hybrids and a weak interaction between aromatic EO groups and amino chains in interlayer space of OrgMt in the case of OrgMt/EO hybrids were suggested.
      Graphical abstract image

      PubDate: 2017-07-03T06:51:04Z
      DOI: 10.1016/j.clay.2017.06.018
      Issue No: Vol. 146 (2017)
       
  • Influence of dehydration on the dielectric and structural properties of
           organically modified montmorillonite and halloysite nanotubes
    • Authors: Kadlec
      Abstract: Publication date: October 2017
      Source:Applied Clay Science, Volume 147
      Author(s): R. Polanský, P. Kadlec, Z. Kolská, V. Švorčík
      The dielectric behaviours of organically modified montmorillonite (Cloisite-20) and nanosized tubular halloysite (Dragonite-HP) were investigated using broadband dielectric spectroscopy (BDS) under dehydration conditions up to 200°C. The thermal and structural properties of both tested clay minerals were also initially examined in the as-received and dehydrated samples. Dragonite-HP was shown to lose 2.2 mass% of the adsorbed and interlayer water up to 200°C. The dehydration of Dragonite-HP also caused the tightly connected tubular layers to unfold, thereby increasing the specific surface area and the total pore volume. Cloisite-20 lost only 1.1 mass% of its adsorbed water during dehydration due to the presence of an organic modifier, bis(hydrogenated tallow alkyl)dimethyl. Its presence led to decreases in the specific surface area and total pore volume of Cloisite-20 relative to those of pristine montmorillonite. BDS revealed that the dielectric constant (ε') and dissipation factor (tan δ) of the thermally treated Dragonite-HP increased and that the volume resistivity (ρ v ) decreased within one order of magnitude in the temperature range of −40 to 90°C. In contrast, the ε' of the thermally treated Cloisite-20 increased by two orders of magnitude, the tan δ increased by more than three orders of magnitude, and the ρ v decreased by five orders of magnitude. The values of ε', tan δ and ρ v measured via BDS demonstrate that the dielectric properties of Dragonite-HP at a standard industrial frequency of 50Hz and under a typical operating temperature range are more advantageous than those of Cloisite-20. This finding is very promising for the possible use of Dragonite-HP as a nanofiller for clay/polymer nanocomposites intended for cable core insulation manufacturing.

      PubDate: 2017-08-03T10:13:25Z
       
  • Intercalation of vermiculite in presence of surfactants
    • Authors: Sevim
      Abstract: Publication date: 15 September 2017
      Source:Applied Clay Science, Volume 146
      Author(s): Sevim İşçi
      Vermiculite was modified with surfactants in order to enable intercalation of vermiculite layers. Since vermiculite has negative charges on its surfaces, it was expected that cationic surfactant would expand the clay mineral layers more than an anionic surfactant. Nevertheless, negative parts of the anionic surfactants interacted with the positively charged edges of vermiculite and caused to super lattice structure so, unexpectedly the expansion of the layers was determined to be fully collapsed phase of vermiculite. Colloidal and structural properties of vermiculite dispersions were examined in presence of anionic, cationic and nonionic surfactants. The results showed that cationic surfactant covered the surface of the vermiculite with a second layer but the expansion of the clay mineral layer was limited compared to the anionic surfactant. The anionic surfactant produced electrostatic interaction with the positively charged edges of vermiculite and fully expanded the layer structure of the vermiculite.
      Graphical abstract image

      PubDate: 2017-06-01T16:08:31Z
       
 
 
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