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  Subjects -> EARTH SCIENCES (Total: 644 journals)
    - EARTH SCIENCES (467 journals)
    - GEOLOGY (69 journals)
    - GEOPHYSICS (26 journals)
    - HYDROLOGY (21 journals)
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EARTH SCIENCES (467 journals)                  1 2 3 | Last

Showing 1 - 200 of 371 Journals sorted alphabetically
Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Open Access   (Followers: 6)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 14)
Advances In Physics     Hybrid Journal   (Followers: 6)
Aeolian Research     Hybrid Journal   (Followers: 5)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 3)
AMBIO     Hybrid Journal   (Followers: 12)
Anadolu University Journal of Science and Technology     Open Access  
Anales del Instituto de la Patagonia     Open Access   (Followers: 1)
Andean geology     Open Access   (Followers: 3)
Annales Henri Poincaré     Hybrid Journal   (Followers: 3)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access  
Annals of Geophysics     Full-text available via subscription   (Followers: 8)
Annals of GIS     Hybrid Journal   (Followers: 14)
Annals of Glaciology     Full-text available via subscription   (Followers: 2)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene     Hybrid Journal   (Followers: 2)
Anthropocene Review     Hybrid Journal   (Followers: 4)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Geochemistry     Hybrid Journal   (Followers: 10)
Applied Geomatics     Hybrid Journal   (Followers: 3)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 2)
Applied Remote Sensing Journal     Open Access   (Followers: 13)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 32)
Arctic Science     Open Access   (Followers: 5)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 9)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 14)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 6)
Asian Journal of Earth Sciences     Open Access   (Followers: 19)
Asian Review of Environmental and Earth Sciences     Open Access   (Followers: 1)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 1)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 11)
Atmospheric and Climate Sciences     Open Access   (Followers: 22)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 10)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 9)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 19)
Bulletin of Volcanology     Hybrid Journal   (Followers: 16)
Cadernos de Geociências     Open Access  
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 14)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 17)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 13)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 4)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 2)
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 23)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 7)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Contemporary Trends in Geoscience     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 9)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 1)
Coral Reefs     Hybrid Journal   (Followers: 16)
Cretaceous Research     Hybrid Journal   (Followers: 6)
Cybergeo : European Journal of Geography     Open Access   (Followers: 3)
Depositional Record     Open Access  
Developments in Geotectonics     Full-text available via subscription   (Followers: 3)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 8)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 65)
Earth and Space Science     Open Access   (Followers: 5)
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 3)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 18)
Earth System Dynamics     Open Access   (Followers: 5)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access  
Earth, Planets and Space     Open Access   (Followers: 5)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 6)
Earthquake Science     Hybrid Journal   (Followers: 9)
Earthquake Spectra     Full-text available via subscription   (Followers: 16)
Ecohydrology     Hybrid Journal   (Followers: 9)
Ecological Questions     Open Access   (Followers: 5)
Electromagnetics     Hybrid Journal   (Followers: 2)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 17)
Environmental Geology     Hybrid Journal   (Followers: 9)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access   (Followers: 3)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (Followers: 16)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (Followers: 30)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (Followers: 10)
Exploration Geophysics     Hybrid Journal   (Followers: 3)
Facies     Hybrid Journal   (Followers: 8)
Fieldiana Life and Earth Sciences     Full-text available via subscription   (Followers: 1)
Física de la Tierra     Open Access  
Folia Musei rerum naturalium Bohemiae occidentalis. Geologica et Paleobiologica     Open Access  
Folia Quaternaria     Open Access  
Forestry Chronicle     Full-text available via subscription   (Followers: 10)
Frontiers in Earth Science     Open Access   (Followers: 4)
Frontiers in Geotechnical Engineering     Open Access   (Followers: 2)
Frontiers of Earth Science     Hybrid Journal   (Followers: 8)
Fundamental and Applied Limnology / Archiv für Hydrobiologie     Full-text available via subscription   (Followers: 4)
GEM - International Journal on Geomathematics     Hybrid Journal   (Followers: 1)
Geo-Marine Letters     Hybrid Journal   (Followers: 7)
Geoacta     Open Access   (Followers: 4)
Geobiology     Hybrid Journal   (Followers: 7)
Geocarto International     Hybrid Journal   (Followers: 3)
Geochemistry : Exploration, Environment, Analysis     Hybrid Journal   (Followers: 6)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 23)
Geochimica et Cosmochimica Acta     Hybrid Journal   (Followers: 22)
Geochronometria     Hybrid Journal   (Followers: 3)
Geoderma Regional : The International Journal for Regional Soil Research     Full-text available via subscription   (Followers: 3)
Geodinamica Acta     Hybrid Journal   (Followers: 3)
Geodynamics & Tectonophysics     Open Access  
Geoenvironmental Disasters     Open Access   (Followers: 3)
Geofluids     Hybrid Journal   (Followers: 4)
Geoforum     Hybrid Journal   (Followers: 19)
Géographie physique et Quaternaire     Full-text available via subscription  
Geography and Natural Resources     Hybrid Journal   (Followers: 4)
Geoheritage     Hybrid Journal   (Followers: 1)
Geoinformatica Polonica : The Journal of Polish Academy of Arts and Sciences     Open Access  
Geoinformatics & Geostatistics     Hybrid Journal   (Followers: 3)
Geological Journal     Hybrid Journal   (Followers: 13)
Geological Magazine     Hybrid Journal   (Followers: 15)
Geology Today     Hybrid Journal   (Followers: 17)
Geomagnetism and Aeronomy     Hybrid Journal   (Followers: 2)
Geomatics, Natural Hazards and Risk     Hybrid Journal   (Followers: 6)
GEOmedia     Open Access   (Followers: 1)
Geomorphology     Hybrid Journal   (Followers: 22)
Geophysical & Astrophysical Fluid Dynamics     Hybrid Journal   (Followers: 2)
Geophysical Journal International     Hybrid Journal   (Followers: 28)
Geophysical Prospecting     Hybrid Journal   (Followers: 7)
Geophysics     Full-text available via subscription   (Followers: 17)
GeoResJ     Hybrid Journal  
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards     Hybrid Journal   (Followers: 6)
Geoscience Canada : Journal of the Geological Association of Canada / Geoscience Canada : journal de l'Association Géologique du Canada     Full-text available via subscription   (Followers: 3)
Geoscience Data Journal     Open Access   (Followers: 2)
Geoscience Frontiers     Open Access   (Followers: 8)
Geoscience Letters     Open Access  
Geosciences     Open Access   (Followers: 2)
Geosciences Journal     Hybrid Journal   (Followers: 9)
Geoscientific Instrumentation, Methods and Data Systems     Open Access   (Followers: 2)
Geoscientific Model Development     Open Access   (Followers: 2)
Geostandards and Geoanalytical Research     Hybrid Journal   (Followers: 2)
Geosystem Engineering     Hybrid Journal  
Geotectonic Research     Full-text available via subscription   (Followers: 4)
Geotectonics     Hybrid Journal   (Followers: 6)
GFF     Hybrid Journal  
GISAP : Earth and Space Sciences     Open Access   (Followers: 1)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 3)
Global and Planetary Change     Hybrid Journal   (Followers: 11)
Global Biogeochemical Cycles     Full-text available via subscription   (Followers: 8)
Gondwana Research     Hybrid Journal   (Followers: 6)
Grassland Science     Hybrid Journal   (Followers: 1)
Ground Water     Hybrid Journal   (Followers: 18)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 15)
GSA Today     Partially Free  
Helgoland Marine Research     Open Access   (Followers: 3)
History of Geo- and Space Sciences     Open Access   (Followers: 3)
Hydrobiologia     Hybrid Journal   (Followers: 17)
Hydrogeology Journal     Hybrid Journal   (Followers: 14)
Hydrological Processes     Hybrid Journal   (Followers: 18)
Hydrology and Earth System Sciences     Open Access   (Followers: 19)
ICES Journal of Marine Science: Journal du Conseil     Hybrid Journal   (Followers: 51)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 10)
Indian Geotechnical Journal     Hybrid Journal   (Followers: 2)
Indonesian Journal on Geoscience     Open Access   (Followers: 2)
Interdisciplinary Environmental Review     Hybrid Journal   (Followers: 3)
International Geology Review     Hybrid Journal   (Followers: 5)
International Journal of Advanced Geosciences     Open Access  
International Journal of Advanced Remote Sensing and GIS     Open Access   (Followers: 13)
International Journal of Advancement in Earth and Enviromental Sciences     Open Access   (Followers: 2)
International Journal of Advancement in Remote Sensing, GIS, and Geography     Open Access   (Followers: 11)
International Journal of Applied Earth Observation and Geoinformation     Hybrid Journal   (Followers: 9)
International Journal of Coal Geology     Hybrid Journal   (Followers: 2)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 8)
International Journal of Earth Sciences     Hybrid Journal   (Followers: 26)
International Journal of Forest, Soil and Erosion     Open Access   (Followers: 4)
International Journal of Geo-Engineering     Open Access  
International Journal of Geographical Information Science     Hybrid Journal   (Followers: 42)

        1 2 3 | Last

Journal Cover Applied Clay Science
  [SJR: 1.17]   [H-I: 71]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2970 journals]
  • Editorial Board
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128




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

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


      PubDate: 2016-05-02T10:19:29Z
       
  • Characterization of porous clay ceramics used to remove salt from the
           saline soils
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Jalila Jalali, Moncef Balghouthi, Hatem Ezzaouia
      This paper presents the characterization of porous argil ceramic columns used as a tool to remove salt from the saline soils. The characterization of the samples was performed before and after application for the salt extraction from the soil. Phase, chemical and microstructural characterizations of the whole series of samples were carried out by using X-ray diffraction technique (XRD), ICP-AES measurements and scanning electron microscope (SEM), respectively. Therefore, XRD revealed that quartz is the most important phase. Besides, sodium chloride (halite, NaCl) is the predominant compound formed during the desalination time. The presence of high-temperature phases in the ceramic columns such as diopside and anorthite showed the use of high firing temperatures, in the range 950–1050°C. In addition, SEM observation on cross-sections clearly showed a network of small dense zones, including quartz grains, interconnected by recrystallized porous phases. These images showed the importance of the pores dimensions and structures on the solution movement and salt deposal. Therefore, it revealed that the porosity heterogeneities could have a great impact on the location of efflorescence at the ceramic column surface. As a consequence, the obtained results allowed us to choose the suitable clay ceramic for the salt extraction from the soil.


      PubDate: 2016-05-02T10:19:29Z
       
  • Influence of physical/chemical treatments to delamination of nanohybrid
           kaolinite-dipicolinate
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Adrieli Cristina da Silva, Katia J. Ciuffi, Márcio José dos Reis, Paulo Sergio Calefi, Emerson Henrique de Faria
      This work shows how submitting kaolinite grafted with dipicolinic acid (Kaol-dpa) to treatment with different solvents and physical/chemical treatment (e.g., ultrasound bath, magnetic stirring, or thermal treatment in water) influences Ka-dpa delamination. X-ray powder diffraction, chemical analysis (C, H, and N), thermal analysis, Fourier-transform infrared spectroscopy, and transmission electron microscopy aided examination of all the samples. Delamination of the treated Kaol-dpa samples elicited changes in the intensity of the characteristic Kaol-dpa d001 reflections. Treatment with different solvents reduced the intensity of the d001 reflections, which almost disappeared for the sample treated with water suggesting the exfoliation. Ultrasound bath, thermal treatment, and magnetic stirring in water also decreased the typical Kaol-dpa d001 reflection and increased the reflection at 2θ=12.2°, the reflection due to the basal spacing of purified kaolinite. Long treatment times eliminated the dipicolinic acid that was only adsorbed onto Kaol-dpa nanohybrid. In conclusion, different types of physical treatment in water were able to delaminate Kaol-dpa, thereby exposing the reactive pyridine-carboxylic groups present in the hybrid matrix.
      Graphical abstract image

      PubDate: 2016-05-02T10:19:29Z
       
  • Effects of grain size on the reactivity of limestone temper in a
           kaolinitic clay
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Ignazio Allegretta, Daniela Pinto, Giacomo Eramo
      Carbonates in clay based ceramics produces higher sintering at lower firing temperatures, but may cause lime spalling, affecting the physical and mechanical behaviour of the ceramic body. The present study investigated the mineralogical and microstructural changes that occur in a kaolinitic clay tempered with different contents of limestone sand with two skewed grain size distributions, after firing. The firing temperatures were set at 500, 750 and 1000°C. The mineralogy of the fired bodies was analyzed by XRPD and quantitative phase analysis was performed using Rietveld method. SEM–EDS analyses were carried out to investigate the changes in microstructures and the clay/limestone reactivity. The use of sand-sized limestone temper and short firing times induced the formation of non-stoichiometric phases at the clay/limestone boundary, ruled by the lateral variation of CaO activity. The structure and composition of the spinel-type phase (e.g. γ-Al2O3), as typical firing product of kaolinite clays, were investigated. Different Ca-silicates and -aluminosilicates (gehlenite, rankinite and larnite) in ceramics fired at 1000°C are found according to the limestone grain size. Lime spalling already occurs in ceramics fired at 750°C; it is triggered by coarse calcined grains (σspalling >σmatrix failure) and then fractures propagates through finer calcined limestone grains.


      PubDate: 2016-05-02T10:19:29Z
       
  • Preparation and characterization of novel clay/scleroglucan nanocomposites
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Rola Mansa, Liva Dzene, Ana Quintela, Fernando Rocha, Christian Detellier
      In pursuit of integrating the use of clay/polymer nanocomposites (CPN) into mainstream applications, improvements made to the preparation process can be useful measures. One such measure involves taking advantage of the global prevalence of clay deposits via their use as primary sources for filler material, as opposed to expensive reference or commercial clay minerals. In this paper, a novel CPN was prepared using bentonite from Porto Santo Island, located in the Madeira archipelago, and was subsequently compared to a CPN prepared using the reference clay mineral SWy-2. According to an XRD characterization of both of the CPN materials, a monolayer intercalation of the biopolymer between the clay mineral layers had occurred. TEM results indicated that there was a mixture of exfoliated and intercalated structures in both cases, but in that of the CPN prepared using Porto Santo bentonite, a greater extent of disorder was observed. This was interpreted as having implications in the thermal stability of the CPN, since that of Porto Santo bentonite outperformed the SWy-2 based CPN when the temperatures of the 60% mass loss were compared. Nonetheless, TGA analysis of both nanocomposites indicated a thermal stability that surpassed that of the pristine polymer alone. This advantageous feature, in conjunction with the low-cost and high accessibility of filler material sourced directly from natural clay deposits, is a promising aspect towards improving the applicability of clay polymer nanocomposites.


      PubDate: 2016-05-02T10:19:29Z
       
  • Preparation and characterization of non-solvent halloysite nanotubes
           nanofluids
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Shiwen Yang, Shan Li, Xianze Yin, Luoxin Wang, Dongzhi Chen, Yingshan Zhou, Hua Wang
      In this paper, a novel type of clay mineral (halloysite) nanofluids was successfully synthesized through surface hydroxylated treatment and then tertiary amine and sulfonate anions. The halloysite (Hal) exhibits liquid-like behavior in the absence of solvent above 80°C while it is a gel-like stickum at room temperature. Moreover, the morphology, rheological behavior, thermal and dispersion properties of the resultant Hal nanofluids were systematically characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), UV–Vis transmission spectra and rheological test. Rheological test results show that viscoelasticity (solid-like to liquid-like transition) of Hal nanofluids were regulated by temperature variation. The unique properties of the Hal nanofluids have made this material promising in the applications as rheological additives in industrial paints and polymer processing aids fields.


      PubDate: 2016-05-02T10:19:29Z
       
  • Cu/Mg/Al hydrotalcite-like hydroxide catalysts for o-phenylphenol
           synthesis
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Yongping Zeng, Tianchi Zhang, Yueyang Xu, Ting Ye, Rongrong Wang, Zhenwei Yang, Zhehua Jia, Shengui Ju
      Cu-Mg-Al layered double hydroxides with different amounts of Cu were prepared by the hydrothermal crystallization method. The samples were characterized by XRD and SEM, which confirmed the formation of layered double hydroxides phase. The hydrotalcite materials and their calcined counterparts are further characterized by FT-IR, thermogravimetric, N2 adsorption-desorption, CO2-TPD and temperature-programmed reduction with H2. The Cu/Mg/Al mixed oxide catalysts obtained via thermal decomposition of hydroxides precursor, were used for dehydrogenation of 2-(1-cyclohexenyl). The catalytic measurements conclude that the selectivity to ortho-phenylphenol (OPP) depends on the dispersion of cooper for these catalysts.
      Graphical abstract image

      PubDate: 2016-05-02T10:19:29Z
       
  • Aqueous Acid Orange 7 dye removal by clay and red mud mixes
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): W. Hajjaji, R.C. Pullar, J.A. Labrincha, F. Rocha
      In this study, Portuguese clay, Fe-impregnated clay, red mud and clay/red mud mixtures were used in the removal of Acid Orange 7 by Fenton and photo-Fenton (under UV light) oxidation processes. In comparison with pure adsorption, the catalytic activity of Fe-loaded clay showed an optimum removal rate (98%). This photo-assisted Fenton degradation of Acid Orange 7 azo-dye molecules was exploiting HO radicals from generated H2O2 and clay supported iron species, following the pseudo-first order kinetic mechanism. By using red mud pre-calcined at 400°C, 10% improvement in overall discolouration was observed in comparison to the untreated clay. This improvement is attributed to the partial reduction of Fe3+ to Fe2+ species on the surface of the catalyst, and to the reaction with H2O2 to generate highly oxidative hydroxyl radicals. It was seen that the synergistic effect of photocatalysis due to the presence of TiO2 in the red mud also contributed in this photo-Fenton process. Furthermore, the use of red mud/clay catalyst mixes assured 38% dye discolouration at pH7, but a lowering of solution pH to 3 resulted in a much higher discolouration rate (over 80% after 1h). The good fitting with a pseudo-second-order kinetic model (R2 equals to 0.99) shows that adsorption processes could strongly contribute in the dye removal efficiency.


      PubDate: 2016-05-02T10:19:29Z
       
  • Editorial Board
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126




      PubDate: 2016-05-02T10:19:29Z
       
  • Preparation of palygorskite paraffin nanocomposite suitable for thermal
           energy storage
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Dan Yang, Fen Peng, Hairong Zhang, Haijun Guo, Lian Xiong, Can Wang, Silan Shi, Xinde Chen
      In this study, a series of palygorskite paraffin nanocomposites were prepared by direct impregnation method without vacuuming. In the clay polymer nanocomposite (CPN), up to 143wt% of paraffin could be loaded in acid-treated Pal. The differential scanning calorimetry (DSC) tests indicated that the CPN had a melting temperature of 23.1°C and latent heat of 126.08J·g−1. In addition, Brunauer, Emmett, and Teller (BET), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) were used to characterize the CPN performance. Good thermal stability was observed for CPN by cycling test; we found that the CPN maintained approximate 92% of the initial latent heat after the cycling test. In conclusion, the CPN was a promising material for thermal energy storage used in the building design.


      PubDate: 2016-05-02T10:19:29Z
       
  • Study of spatial distribution of sepiolite in sepiolite/polyamide6,6
           nanocomposites
    • Abstract: Publication date: July 2016
      Source:Applied Clay Science, Volumes 127–128
      Author(s): Cristina Fernandez-Barranco, Anna E. Kozioł, Krzysztof Skrzypiec, Michał Rawski, Marek Drewniak, Africa Yebra-Rodriguez
      The enhancement of the technical properties of a Clay/Polymer Nanocomposite (CPN) is related to the homogeneity and dispersion of the filler within the polymer matrix. In this work, samples of pure polyamide 6,6 (PA66) and reinforced PA66 with 1, 3, 5, 7 and 9wt.% of sepiolite have been studied. The samples have been qualitatively analyzed with different microscopy techniques and with X-Ray diffraction and scattering techniques. The images obtained by confocal microscopy show that the sepiolite is homogeneously distributed in the PA66 matrix. The micrographs taken by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that sepiolite fibres are oriented and equidistantly distributed even in the samples with high percentages of sepiolite. TEM images reveal the absence of clusters of sepiolite and good dispersion of the reinforcement within the matrix. The quantification of the dispersion, calculated from the results of Small Angle X-Ray Scattering (SAXS), indicates that the polymer chains are expanded due to the arrangement of sepiolite within the PA66 matrix and that the fibres are properly dispersed in the polymer.


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


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


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

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

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

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


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


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

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

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


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


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


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


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

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

      PubDate: 2016-04-09T09:45:51Z
       
  • Archaeometric investigation of the Late Chalcolithic-Early Bronze Age I
           and the 1st–2nd millennium BCE potteries from Kuriki-Turkey
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Murat Bayazit, Iskender Işık, Ali Issi, Elif Genç
      In this study, potsherds belonging to the Late Chalcolithic-Early Bronze Age I and the second half of the 2nd millennium BCE-beginning of the 1st millennium BCE from Kuriki (Turkey) were investigated. Energy dispersive X-ray fluorescence and X-ray diffraction were performed for chemical and mineral/phase analysis, respectively. Micro-Raman spectroscopy, optical microscopy and thermal gravimetric-differential thermal analysis were used as complementary techniques. Scanning electron microscopy and energy dispersive X-ray spectrometry were also performed for micro structural and micro chemical characterization. Results showed that mainly illitic and occasionally smectitic type of clays were used. Andesite, basalt, granite and limestone were found as the main sources of the minerals identified in the samples. Considering the decomposition and formation of the minerals, the results showed that potsherds were exposed to firing temperatures changing between 750°C–950°C. SEM images showed that the potsherds have a quite poor vitrification degree and heterogeneous grain distribution suggesting a simple firing technique. The results of this study suggested that despite a long time vacancy from the Late Chalcolithic-Early Bronze Age I to the second half of the 2nd millennium BCE, the ceramic production technology was presumably not changed drastically in Kuriki.


      PubDate: 2016-04-07T12:42:29Z
       
  • Facile synthesis and photocatalytic properties of light emitting layered
           compounds of ZnLaTb hydroxide and oxoanions
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Poonam Singh, Rajamani Nagarajan
      Layered hydroxide containing Zn2+, La3+ and Tb3+ ions intercalated with acetate anions (CH3COO–) have been synthesized by a simple hydrolysis method and characterized. Further ion exchange of this with tungstate, molybdate and vanadate ions in acetic acid medium resulted in layered compounds intercalated with these anions. The phases were characterized by high resolution PXRD, ICP, SEM, FTIR, Raman, UV–visible, PL spectroscopy and TGA techniques. Intercalation of vanadate and tungstate ions in the interlayer of the host hydroxide salt was evident and according to XRD, the samples did not show the presence of any other crystalline impurities. On intercalating molybdate anion, the sample showed two different types of ordering in the PXRD pattern. In the UV–visible absorption spectra of these oxoanion intercalated samples, prominent red shift was observed due to the HOMO-LUMO LMCT transitions. While tungstate and molybdate intercalated samples were green emitters (arising primarily from the Tb3+-ions of the host lattice), strong blue emission, (quenching of green emission of Tb3+) was observed for the vanadate intercalated sample. Superior catalytic performance in terms of photo degradation of aqueous rhodamine-6G dye solutions has been exhibited by the intercalated samples over the acetate intercalated one.
      Graphical abstract image

      PubDate: 2016-04-03T12:38:35Z
       
  • Characterization of tobelite formed from kaolinite under hydrothermal
           conditions (200°C)
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): María Bentabol, María Dolores Ruiz Cruz
      The aim of this paper is the characterization of pure tobelite synthesized in the system (NH4)2O-Al2O3-SiO2-H2O, which is a first, indispensable step for accurately interpreting the data obtained in more complex chemical systems. Tobelite has been synthesized at hydrothermal conditions (200±3°C), using a solid:solution ratio (in weight)=1:15, and reaction times from 1 to 90days and has been characterized by X-ray diffraction; infrared and Raman spectroscopy; differential thermal analysis and thermogravimetry; and transmission-analytical electron microscopy. The average chemical composition of tobelite formed after 90days run time, determined by combining the analytical electron microscopy data with nitrogen determination in the solid products of the reaction by elemental analysis, was [NH4Al1.98(Si3.07Al0.93)O10(OH)2]. The refinement of the X-ray diffraction patterns indicated that the 1M polytype predominates, and the determined cell-parameters were: a =5.219 (0.004) Å; b =9.021 (0.007) Å; c =10.556 (0.009) Å; β =101.41° (0.08); V =487.23 (0.69) Å3. The infrared spectra indicated the presence of two υ4 bands (at 1403 and 1435cm−1), which can be related to the presence of two main tobelite populations with mean particle sizes of 400×60 and 2000×200Å. The thermal study by means of differential thermal analysis and thermogravimetry, combined with X-ray thermodiffraction suggested that the mechanisms of NH4 loss were different in the two differently-sized tobelite populations: the thinner particles showed a low thermal stability (between 380° and 440°C) and the NH4 loss was coupled with dehydroxylation, leading directly to the decrease of the tobelite content. Loss of NH4 from the thicker particles occurred between 440° and 500°C, causing a gradual contraction of the basal spacing, which was followed by dehydroxylation. There were no previous data of Raman spectroscopy of tobelite and this study presents its most characteristic features.


      PubDate: 2016-03-25T08:33:38Z
       
  • Na+ as a probe to structural investigation of dehydrated smectites using
           NMR spectra calculated by DFT
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Carla G. Fonseca, Gustavo S.G. de Carvalho, Fernando Wypych, Renata Diniz, Alexandre A. Leitão
      Ab initio calculations based on density-functional theory (DFT) were made to a large ensemble of representative models of dehydrated smectites with Na+ as counterion. The structures were generated by different isomorphic substitutions of Al3+ by Mg2+ in octahedral sheet and Si4+ by Al3+ in tetrahedral sheet followed by full optimization of the geometries. Structures were chosen among the lowest total energies to calculate nuclear magnetic resonance (NMR) parameters of 1H, 27Al, 29Si, 25Mg and 23Na by means of gauge including projector augmented wave (GIPAW) method. The calculated NMR parameters and simulated spectra suggest that Na+ can be a good probe to investigate the layer structure. The spectra shape for 23Na is more sensitive to isomorphic substitutions in the layer than the other nuclei.


      PubDate: 2016-03-21T00:22:18Z
       
  • The effect of the mineralogical composition of various bentonites on CEC
           values determined by three different analytical methods
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Ko Yeon Choo, Kang Bai
      Bentonite is an important source of montmorillonite, but has a complex surface chemistry that results from its unique combination of properties, including thixotropic gel formation with water, high water absorption, high surface area, layered structure and high cation exchange capability, and may contain other crystalline or amorphous substances, such as quartz, cristobalite and feldspar. Montmorillonite is 2:1 layer in which surface charge development caused by isomorphous substitution results in inserting interlayer cations between its layers. The cations are easily exchanged with other cationic species, a property known as the cation exchange capacity (CEC). CEC values of various commercially available bentonites were determined by three different analytical methods to investigate the effect of the mineralogical composition on CEC value. The first CEC analytical method, termed the BaCl2/MgSO4 method, is to substitute interlayer cations with Ba which is subsequently substituted with Mg and then titrated with EDTA in the presence of ammonia buffer. The second method is an ammonia electrode technique in which after ammoniating bentonites, an ammonia electrode is used to detect dissolved ammonia in the presence of NaOH, and the third is an equilibrium pH method in which all exchangeable metallic cations within the bentonite structure are replaced with acetic acid. Both CEC values obtained by the BaCl2/MgSO4 method for two different masses of each bentonite were all within ±10% of each other with several exceptions. CEC values obtained by the second and third methods were larger than by the first method, for bentonites that contained heulandite of the zeolite group. Additionally, CEC values found by the equilibrium pH method were higher than those determined by the ammonia electrode method for bentonites containing calcite which can be dissolved in acetic acid solution. Although the equilibrium pH method was the simplest to perform, it may be the least accurate, as the presence of calcite and zeolite-type minerals in bentonite samples can result in artificially high CEC values.


      PubDate: 2016-03-21T00:22:18Z
       
  • The effect of natural zeolite on microstructure, mechanical and heavy
           metals adsorption properties of metakaolin based geopolymers
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): S. Andrejkovičová, A. Sudagar, J. Rocha, C. Patinha, W. Hajjaji, E. Ferreira da Silva, A. Velosa, F. Rocha
      This work investigates the effect of clinoptilolite, a natural zeolite, as filler on the mechanical performance and heavy metal's adsorption capacity of the metakaolin-based geopolymers. Clinoptilolite was chosen as an inexpensive additive with high adsorption capacity, replacing metakaolin (0, 25, 50 and 75%) in the synthesis of four different geopolymers (MK100, MK75, MK50 and MK25, respectively). To produce geopolymers with low environmental impact, during the geopolymerization processes the SiO2/Al2O3 and Na2O/Al2O3 molar ratios were kept constant at 1, to reduce sodium silicate and sodium hydroxide to a minimum. The final products were studied by powder X-ray diffraction, 27Al and 29Si solid-state NMR and Scanning electron microscopy. Moreover, strength parameters and heavy metals Pb2+, Zn2+, Cu2+, Cd2+ and Cr3+ adsorption tests were performed. The results show that geopolymerization in the presence of zeolite leads to an increase of the compressive strength of all blended geopolymers, with an optimal metakaolin precursor/zeolite filler ratio of 50:50, affording the highest strength (8.8MPa at 28days). The adsorption of metal cations on geopolymers was well fitted using the Langmuir model (0.97<R2 <0.99). The geopolymers adsorbed heavy metals in the order Pb2+ >Cd2+ >Zn2+, Cu2+ >Cr3+. The maximum adsorption capacity of Cu2+ and Cr3+ was highest for geopolymer with 100% of metakaolin (MK100), while for Pb2+, Cd2+ and Zn2+ the highest adsorption capacity is for geopolymers with 75% of metakaolin (MK75), indicating that 25% zeolite addition to geopolymers has efficiently improved the adsorption capacity.


      PubDate: 2016-03-21T00:22:18Z
       
  • In-situ synthesis of SiCw/Al2O3 composite honeycomb ceramics by
           aluminium-assisted carbothermal reduction of coal series kaolin
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Xiaohong Xu, Xinbin Lao, Jianfeng Wu, Xiaoyang Xu, Yaxiang Zhang, Kun Li
      A new route, aluminium (Al)-assisted carbothermal reduction of aluminosilicate mineral (coal series kaolin, CSK), was developed to in-situ produce SiCw/Al2O3 composite honeycomb ceramics using a three-step reaction scheme. The phase transformation, microstructure evolution and the relevant variations in properties of the composites had been investigated. Results indicated the reduction of CSK-Al system was found to be more superior in preparation of monolithic SiCw/Al2O3 composites under CO-rich condition comparing with the conventional CSK-carbon system. Low linear shrinkage(0.14%), good mechanical and thermophysical properties of samples could be obtained by using Al as assisted reducing agent and firing at 1550 °C as the Vickers hardness, the bending strength, the specific heat capacity and the thermal conductivity were 703.1±21.6HV, 65.9±7.8MPa, 1.09J/(g·K) and 8.96W/(m·K), respectively. The thermal conductivity of the Al2O3 matrix was significantly improved by the incorporation of the in-situ synthesized SiCw with an interlocking texture. The performance study of the produced SiCw/Al2O3 composite honeycomb ceramics revealed that the honeycomb ceramics were characterized by the high softening temperature and the good thermal shock resistance, which make the honeycomb ceramics suitable for the uses as porous thermal storage materials.
      Graphical abstract image

      PubDate: 2016-03-17T00:11:15Z
       
  • Iron removal from kaolin using binuclear rare earth complex activated
           thiourea dioxide
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Wen Cao, Guanghua Xia, Mang Lu, Hangang Huang, Yuxin Xu
      A binuclear rare earth complex was prepared by using Ce3+ and Y3+ as the central ion, and acetyl acetone (Hacac) as the ligand. Thiourea dioxide (TD) had strong reductive properties and good bleaching performance on kaolin after being activated by the complex. The concentrations of TD and the activator were fixed at 30g/L and 0.6g/L respectively, and the influences of raw material proportion, solution pH and reaction time on the activating efficiency of TD were investigated. The results show that TD reached its optimum activating efficiency after activation with the complex prepared under the conditions: the molar ratio of Ce3+:Y3+:Hacac=1:1:7, solution pH=7, and reaction time=3h. The highest reductive potential of TD could reach up to −662mV under the mild conditions (T=25°C, pH=7.2). The influence of the dosage of activated TD on the bleaching effect of kaolin was characterized by colorimeter, XRD, SEM and EDS. The results show that the bleaching effect of kaolin reached the highest when the dosage of activated TD was 0.5wt% (relative to the mass of kaolin). The calcined whiteness index of kaolin was raised from 82.6% to 88.7%.


      PubDate: 2016-03-13T00:04:54Z
       
  • Experimental design investigation for vermiculite modification:
           Intercalation reaction and application for dye removal
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Líbia Nayane Fernandes de Queiroga, Patricia Kaori Soares, Maria G. Fonseca, Fernando José Volpi Eusébio de Oliveira
      With the aim to improve the anionic dye sorption capacity of vermiculite, ethylenediamine was employed to modify vermiculite under different conditions. In this study, a 24 factorial design was used for organovermiculite preparation to assess the influence of the temperature (303 and 323K), ethylenediamine concentration (0.1 and 0.2molL−1), reaction time (24 and 48h) and acid activation of the clay mineral (leached and non-leached samples). The pristine and modified solids were characterized by CHN elemental analysis, infrared spectroscopy and X-ray diffraction. Principal component analysis and hierarchical cluster analysis were performed on the IR spectra to investigate the effect of parameter variation on the vermiculite modification. The reaction temperature and the acid activation of the vermiculite significantly influenced the vermiculite structural features. The optimized sample presented good adsorption capacity for Remazol Brilliant Blue RN, 11.02mgg−1. This study concluded that vermiculite modified with ethylenediamine behaved as a good sorbent to anionic dye.
      Graphical abstract image

      PubDate: 2016-03-13T00:04:54Z
       
  • Preparation and properties of halogen-free flame-retardant layered
           silicate-polyamide 66 nanocomposites
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Kenji Tamura, Shoichi Ohyama, Kiyoshi Umeyama, Takafumi Kitazawa, Akihiko Yamagishi
      The relationship between the morphology, flammability and mechanical properties of layered silicate-polyamide 66 (PA66) nanocomposites was investigated. The nanocomposites were composed of PA66, melamine-modified layered silicate (MLS) as a nanofiller, and/or melamine cyanurate (MC). Samples of MLS with different dispersion states were obtained by changing the melt-mixing procedures for PA66, MLS and MC. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal analysis, strength tests, cone calorimetry tests and UL 94 vertical burning tests were used to examine the effects of MLS on the morphology, mechanical properties and flame resistance performance of the materials. The data revealed a correlation between the dispersion state of the MLS layers and flame retardancy. The nanocomposite manufactured by one-stage kneading of a mixture of PA66, MLS and MC earned a UL 94 rating of V0. The flame retardancy of dripping particles during combustion was found to be due to uneven dispersion of MLS in the PA66 matrix.
      Graphical abstract image

      PubDate: 2016-03-13T00:04:54Z
       
  • A natural clayey adsorbent for selective removal of lead from aqueous
           solutions
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Ali Sdiri, Mohamed Khairy, Samir Bouaziz, Sherif El-Safty
      Natural clay minerals are an inherently colorless class of materials, which have long been known for their versatility as adsorbents due to their interchange capacity, large catalytic support, great surface area, and low cost. Herein, we have reported the use of natural clay, collected from the Gabes area, southern Tunisia (Early Cretaceous) for selectively capturing of lead ions from aqueous environments. Our results showed that natural clay samples were mainly composed of silica, alumina, iron and magnesium oxides. Adsorption data showed that the studied clay samples preferably removed substantial amounts of lead ions from water. The removal efficiency of lead ions was about 86.4mg/g of clay and followed pseudo-second-order kinetics. More than 95% of the total adsorptive capacity occurred within 30min. These results suggest the Early Cretaceous clays, Tunisia, turned out to be an effective natural adsorbent for capturing of lead ions from aqueous environment.


      PubDate: 2016-03-13T00:04:54Z
       
  • Direct acid activation of kaolinite and its effects on the adsorption of
           methylene blue
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): W. Gao, S. Zhao, H. Wu, W. Deligeer, S. Asuha
      Coal-bearing kaolinite was directly treated with concentrated sulfuric acid to improve its surface properties and adsorption ability. Acid treatment was carried out at various temperatures (i.e., room temperature −250°C), by varying time of treatment from 0 to 120min. The samples were characterized by X-ray diffraction analysis, elemental analyses, thermogravimetric analysis, N2 adsorption-desorption analysis, high-resolution transmission electron microscopy, and Fourier transformed infrared spectroscopy. The activation of kaolinite strongly depended on the acid treatment including treatment temperature and time. Acid treatment at room temperature did not cause significant alterations either in the chemical composition or in the structure of the kaolinite. On the other hand, treatment at increased temperature led to the removal of Al3+ ions and thus increased the porosity of the material. The surface area and the pore volume of original kaolinite could be greatly changed as a function of treatment temperature and time of treatment, and they increased from 13.6 to 257.8m2 g−1 and from 0.045 to 0.25cm3 g−1, respectively, when the kaolinite was treated at 200°C for 30min. The adsorption ability of acid-activated kaolinite (AAK) was investigated using methylene blue (MB) as a typical pollutant. For this, the effects of contact time, pH, initial MB concentration and temperature were studied in batch mode. Gibb's free energy (ΔG 0), entropy (ΔS 0) and enthalpy (ΔH 0) changes for MB adsorption were calculated. Owing to its high surface area, the AAK showed higher removal efficiency for MB than for original kaolinite, with a maximum adsorption capacity of 101.5mgg−1.
      Graphical abstract image

      PubDate: 2016-03-13T00:04:54Z
       
  • Bio-nanocomposite films reinforced with organo-modified layered double
           hydroxides: Preparation, morphology and properties
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Jiazhuo Xie, Kun Zhang, Jianfeng Wu, Guangfeng Ren, Hongying Chen, Jing Xu
      Bio-nanocomposite films based on organo-modified layered double hydroxides (OLDH)/poly(butylene adipate-co-terephtalate) (PBAT) were prepared with solution casting method. The morphology and structural characterizations on the OLDH and OLDH/PBAT bio-nanocomposite films were performed by Fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The physical properties of the films were determined by thermal, mechanical and optical analysis, and contact angle testing and water vapor transmission (WVT) measurement. The XRD results show that the basal spacing of the layered double hydroxides (LDH) was increased from 0.88nm to 4.45nm after the modification by long-chain lauryl alcohol phosphoric acid ester potassium (MAPK). The exfoliated OLDH were well dispersed in the PBAT matrix. The crystallization temperature of the OLDH/PBAT bio-nanocomposite films was significantly higher than the base matrix. The hydrophilic, optical, tensile and water vapor barrier properties of the films were obviously improved by the addition of OLDH with low content (1%). The results of this study would be useful for investigating the potential to develop the eco-friendly packaging films.


      PubDate: 2016-03-13T00:04:54Z
       
  • Adduct modified nano-clay mineral dispersed polystyrene nanocomposites as
           advanced corrosion resistance coatings for aluminum alloys
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Annu Raju, V. Lakshmi, R.K. Vishnu Prataap, V.G. Resmi, T.P.D. Rajan, C. Pavithran, V.S. Prasad, S. Mohan
      The present investigation is on processing of a series of clay polystyrene nanocomposite (CPS) coatings containing different adduct modified montmorillonite (Mt) for corrosion resistance coating applications. The corrosion properties were studied using potentiodynamic and electrochemical impedance spectroscopy measurements in 3.5wt% aqueous NaCl electrolyte. The CPS coatings offered enhanced corrosion protection for Aluminum 6061 alloy even at high clay loading (20wt%). The order of their protection efficiency was CPS-AMt>Pristine PS>Pristine Na+-Mt. Dispersion of Mt in the polystyrene matrix resulted in significant improvement of properties such as corrosion protection, optical clarity, electrical conductivity and thermal stability.
      Graphical abstract image

      PubDate: 2016-03-13T00:04:54Z
       
  • Spectral behaviour of TMPyP/layered silicate hybrid nanomaterials in
           aqueous dispersions of reduced-charge montmorillonites
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): A. Čeklovský, P. Boháč, A. Czímerová
      Spectral properties of tetracationic organic dye, meso-tetrakis(N-methylpyridinium-4-yl) porphyrin adsorbed on layered silicate templates of various layer charge were investigated. A series of reduced charge Nanocor montmorillonites was used as host matrices. The study primarily focuses on the influence of the layer charge on the emission characteristics and photoactivity of prepared materials. Usually, adsorption of dyes such as porphyrins leads to significant changes in their spectral characteristics with the main goal being the preservation of their photoactivity. The spectral changes can be explained in terms of e.g. structural changes (flattening, protonation), as well as molecular aggregation. Hence, the aim of this study is to clarify the way to influence the spectral properties and the subsequent photoactivity of incorporated molecules via a strategy of appropriate combination of a photoactive component with specific inorganic templates.


      PubDate: 2016-03-13T00:04:54Z
       
  • Thermal behaviour of clays and clay-water mixtures for pelotherapy
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Francisco Armijo, Francisco Maraver, Manuel Pozo, María Isabel Carretero, Onica Armijo, Miguel Ángel Fernández-Torán, María Virginia Fernández-González, Iluminada Corvillo
      To prepare peloids for thermotherapy, the thermal behaviour of their component clay pastes needs to be known. This study was designed to experimentally determine the specific heat capacity and cooling kinetics of pastes prepared by adding different proportions of water to eight commercially available clays of different composition. According to exponential equations fitted to the cooling curves for the pastes, a new parameter designated the relaxation time is proposed. Using this parameter, the clayey pastes could be classified on the basis of rate of heat release. According to its specific heat capacity and relaxation time, Na-activated magnesium bentonite emerged as the most suitable clay material to prepare peloids with applications in thermotherapy.


      PubDate: 2016-03-08T17:06:04Z
       
  • A noble additive cum compatibilizer for dispersion of nanoclay into
           ethylene octene elastomer
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Soumya Mondal, Amit Das, Joyeeta Bandyopadhyay, Suprakas Sinha Ray, Gert Heinrich, Abhijit Bandyopadhyay
      This paper introduces a poly(ethylene-co-octene)-poly(ethylene-co-vinyl acetate) double network hybrid as a noble additive cum compatibilizer for poly(ethylene-co-octene) (POE). The addition of only 0.5 mass% of the hybrid into POE has raised the net crystallinity from 29% to 59% and consequently improved both static (tensile strength, modulus and elongation at break) and dynamic (stress relaxation and hysteresis) properties of the virgin POE. As compatibilizer for organically modified montmorillonite (OMt) most of the properties further improved at a minimal loading of both OMt (0.5–1.0mass%) and compatibilizer (1–2mass%) owing to the establishment of a dominant intercalated structure. Although the die swell is slightly increased in the presence of both double network hybrid and OMt, the extruded profiles exhibit remarkable improvement in appearance compared to the virgin POE.


      PubDate: 2016-03-08T17:06:04Z
       
  • Modification of natural bentonite using a chelating agent for sorption of
           60Co radionuclide from aqueous solution
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): S.S. Metwally, R.R. Ayoub
      Chemisorption of 60Co radionuclide from aqueous solution using modified bentonite clay with 8-Hydroxy quinoline, as a chelating agent, was investigated. Characterization of the modified clay was carried out using some analytical techniques including, SEM, XRF, EDX and FT-IR spectroscopy. Some factors affecting on the sorption process were studied such as pH of medium, contact time, metal ion concentrations and temperature. Some kinetic models were tested for the sorption process including pseudo-first-order, pseudo-second-order, intra-particle diffusion and Boyd's film-diffusion model. The results indicated that the sorption process well fit pseudo-second-order model, the sorption is controlled by intra-particle diffusion mechanism, and the process is chemisorption since the value of diffusion coefficient is in the order 10−15 m2/s. Regeneration process was carried out, the results illustrated that 8HQ-Bent can be completely generated with 0.5M HNO3. Finally, one can conclude that the modified bentonite is an efficient sorbent media and recommended for removal of 60Co radionuclide from radioactive waste.


      PubDate: 2016-03-08T17:06:04Z
       
  • Inhibitory effect of clay mineral on methanogenesis by Methanosarcina
           mazei and Methanothermobacter thermautotrophicus
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Deng Liu, Hailiang Dong, Abinash Agrawal, Rajesh Singh, Jing Zhang, Hongmei Wang
      With increased concentration of methane in the atmosphere and its impact on climate, effective mitigation of methane emission is of global importance. Recent studies have shown the inhibition of microbial methanogenesis upon addition of ferruginous clay minerals. To better elucidate the mechanism of the inhibitory effect of clay minerals on methanogenesis, laboratory experiments with Methanosarcina mazei and Methanothermobacter thermautotrophicus were performed in batch systems in which pristine kaolinite or iron-coated kaolinite were added as representative clay minerals. Soluble Al in solution and production of Fe(II) and methane gas were monitored over the course of the experiments. The mineralogical changes in the kaolinites were characterized with scanning electron microscopy. The results confirmed that both Ms. mazei and Mt. thermautotrophicus were capable of reducing ferric iron with H2/CO2 as methanogenic reactants. Both pristine and iron-coated kaolinites could act as effective inhibitors of methanogenesis. The overall methane production was similar with pristine kaolinite and iron-coated kaolinite, although at the beginning of the experiment less CH4 was observed in iron-coated kaolinite system. The inhibition of methanogenic activity observed in pristine kaolinite was primarily ascribed to the toxicity effect of aluminum. A more effective inhibition of methanogenesis in iron-coated kaolinite during the first several days could be explained by the combined effects of aluminum toxicity and diversion of electron flow from CO2 to Fe(III). Our results have important implications for mitigating methane emission in natural or anthropogenic settings.
      Graphical abstract image

      PubDate: 2016-03-08T17:06:04Z
       
  • The influence of clay orientation and crystallinity on oxygen permeation
           in dispersion barrier coatings
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Å. Nyflött, E. Moons, C. Bonnerup, G. Carlsson, L. Järnström, M. Lestelius
      In this study oxygen permeability in dispersion barriers produced from poly(vinyl alcohol) (PVOH) and kaolin clay blends coated onto polymeric supports was investigated. To determine the oxygen permeability, two measurement methods were used: the oxygen transmission rate (OTR) and the ambient oxygen ingress rate (AOIR). It was found that with increasing kaolin content the oxygen permeability increased, up to about 5wt% kaolin, whereafter the oxygen permeability decreased, as was expected. The increased (>5%) kaolin loading lowered the diffusion because of an increased tortuosity. Structural information about the dispersion-barrier coatings, such as kaolin orientation and polymer crystallinity, was obtained from Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Kaolin orientation was influenced by the drying temperature, the thickness of the samples, and the kaolin concentration. The polymer crystallinity increased in thicker samples. The drying temperature did not show any clear effect on the crystallinity of thin samples, while for the thicker barriers, combined with a kaolin concentration lower than 20wt%, a higher crystallinity was achieved at lower drying temperatures. This study demonstrates the strong influence of chemical and physical structures on the permeability of the investigated coatings.
      Graphical abstract image

      PubDate: 2016-03-08T17:06:04Z
       
  • Pure-phase zeolite beta synthesized from natural aluminosilicate minerals
           and its catalytic application for esterification
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Yuanyuan Yue, Haiyan Liu, Yanni Zhou, Zhengshuai Bai, Xiaojun Bao
      The use of natural aluminosilicate minerals as the low-cost starting materials for zeolite synthesis is a field of current interest. However, impurities existing in these minerals greatly affect the purity of final products. Herein, we describe a cheap and green route for synthesizing pure-phase zeolite beta from natural aluminosilicate minerals via a modified nanoscale depolymerization-reorganization approach. The physicochemical and catalytic properties of the synthesized zeolite beta were systematically characterized and assessed, respectively. The results indicate that the resulting zeolite beta possesses more moderate Brönsted acid sites compared with the reference one, and thus exhibits higher catalytic activity in the esterification of acetic acid with ethanol. This methodology demonstrates great perspective for the low-cost and environmentally-benign synthesis of zeolite beta that avoids the use of aluminum- and silicon-containing inorganic chemicals, eliminates the interference of impurities, and reduces the usage of the organic template.


      PubDate: 2016-03-08T17:06:04Z
       
  • Characterization of rectorite from the Beatrix Gold Mine in South Africa
    • Abstract: Publication date: June 2016
      Source:Applied Clay Science, Volume 126
      Author(s): Maria T. Atanasova, Anastasia Vyalikh, Ulrich Scheler, Walter W. Focke
      Three rectorite samples from the Beatrix Gold Mine, South Africa were characterized. Scanning electron microscopy revealed a layered morphology. High resolution transmission microscopy showed well distinguished light and dark layers of about 2.20nm consistent with the 1:1 interstratified mica-smectite nature. X-ray diffraction measurements confirmed the basal spacing d001 of 2.20nm consistent with a one-water-layer structure. Unit cell parameters, for a monoclinic unit cell with primitive lattice, refined to a =5.177Å; b =8.980Å; c =22.489Å and β=97.335° with mean crystallite size around 14nm and calculated cell volume of 1045Å3. The Greene-Kelly test suggested that the expandable smectite layers have montmorillonite-beidellite composition. Nuclear magnetic resonance spectroscopy indicated a high degree of Al substitution and the presence of two different Al sites corresponding to six- and four-fold octahedral and tetrahedral aluminum respectively. The chemical composition and diffraction data suggest that the mica is Na-Ca-rich, i.e. of paragonite-margarite series. The fixed interlayer regions (mica interlayers) contains proportionally dominant Na+ and Ca2+ and minor amounts of K+. The exchangeable smectitic interlayers contain almost equal amounts of Na+ and Ca2+ ions. The distribution of the interlayer Na+ ions was quantified by 23Na solid-state NMR spectroscopy. It points to a three component mixed-layer structure with considerable variation in the composition of the mica layer of the different samples.


      PubDate: 2016-03-08T17:06:04Z
       
 
 
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